Portrait of Dr Benito Sanz Izquierdo

Dr Benito Sanz Izquierdo

Lecturer in Electronic Systems

About

Dr. Sanz received the B.Sc. from the ULPGC, Spain, and the M.Sc. and Ph.D. degrees from the University of Kent, U.K. He holds a Masters in Business Administration degree (MBA) from Canterbury Christ Church University, UK. Prior to becoming a lecturer in 2013, he was a Research Associate with the School of Engineering and Digital Arts, where he worked on  EPSRC funded projects. In 2012, he worked for Harada Industries Ltd on the development of novel antennas for the automotive industry. In 2017, he was visiting fellow at Selex E.S. where he worked on reconfigurable antennas for the defense industry. Since 2015, he has been EPSRC High Value Manufacture fellow which involves working with the Centre of Process Innovation on the development of Innovative 3D printing solutions for antenna applications.

His main research interests are multiband antennas, wearable microwave devices, substrate integrated waveguides components, electromagnetic band-gap structures and frequency selective surfaces. Currently, he is involved in projects in he area of additive manufacturing (3D printing) for electromagnetic device fabrication. His research has been funded by the Royal Society, the Royal Academy of Engineering, the EPSRC. He has authored more than 100 peer-reviewed journal publications and international conference papers and has h-index of over 23. He has received many awards and special mentions for his work on wearable antennas, reconfigurable antennas, 3D printed antennas and frequency selective surfaces.

He is an active researcher and excellent supervisor who is always looking for potential PhD students that can be supported by government scholarships (e.g., China Scholarship Council or similar government scholarships in other countries) or other sources.

Research interests

Compact multiband antennas, Electromagnetic Band Gap (EBG) structures, Frequency Selective Surfaces (FSS), Reconfigurable electromagnetic structures, 3D Printing of Antennas.

Publications

Article

  • Jun, S. et al. (2018). 3D Printing of Conformal Antennas for Diversity Wrist Worn Applications. IEEE Transactions on Components, Packaging and Manufacturing Technology [Online]. Available at: https://doi.org/10.1109/TCPMT.2018.2874424.
    This paper presents for the first time the application of 3D printing techniques for the development of conformal antennas for diversity wrist worn wireless communications. Three processes are described with the common challenge of depositing the metallic layers of the antennas on a bracelet fabricated using fuse filament fabrication (FFF). The first is a multistep process which combines adding a layer to smooth the surface of the band, aerosol jetting the metallic tracks, flash curing and then electroplating. The second combines painting the metallic layers by hand and then electroplating. The last process uses a single machine to fabricate both the bracelet and then the metallic layers by means of a direct write system with silver conductive ink. The wrist worn antennas are presented and its performances on the human wrist are discussed. All antennas cover 2.4 GHz and 5.5 GHz used for WLAN communication with the reflection coefficients less than −10 dB. The diversity wrist worn antennas system is developed for the final two processes. Three WLAN antennas are fabricated at different positions and shape angles within the bracelet. In terms of communications systems, the advantage of this configuration is that it can increase coverage. The radiation patterns of the antenna are nearly omnidirectional in free space and directional on the human wrist. When the patterns of the three antennas are combined together, the coverage for the communication system improves. Simulation results of all antenna designs and studies using the finite integration technique (FIT) agree well with experimental measurement results. The main motivation of this work is to investigate alternative additive manufacturing methods for the development of conformal diversity antennas on customized 3D printed parts.
  • Gu, C. et al. (2018). Wideband high-gain millimetre/submillimetre wave antenna using additive manufacturing. IET Microwaves, Antennas & Propagation [Online] 12:1758-1764. Available at: https://doi.org/10.1049/iet-map.2018.5412.
    This paper presents a novel design of a wideband high-gain resonant cavity antenna (RCA) for millimetre and
    submillimetre wave bands, and its fabrication using additive manufacturing. The proposed RCA antenna consists of a partially
    reflecting surface and three impedance matching layers fed by a waveguide. Additive manufacturing (AM) techniques are
    utilized to fabricate the design operating at 30 GHz. Two fabrication techniques are assessed for printing the antenna. The
    first technique is based on printing a dielectric material and fully coating the parts with a metallic layer, while the second
    technique involves printing the parts in a single process using metal 3D printing. The first technique offers a lightweight
    solution while the second technique can print the whole model in one run. The antenna design is investigated by both
    simulations and experiments. The measured results show an 3dB gain bandwidth of about 10%, and high gain over 15 dBi
    for all the three resulting antennas. Good agreement between simulation and measurement is obtained. The antenna has a
    low cost and achieved good performance in terms of wide bandwidth and high gain, thus it is potentially useful for highspeed
    wireless communications at millimetre-wave and sub-millimetre-wave frequencies.
  • Gu, C. et al. (2017). Dual-Band Electronically Beam-Switched Antenna Using Slot Active Frequency Selective Surface. IEEE Transactions on Antennas and Propagation [Online] 65:1393-1398. Available at: http://dx.doi.org/10.1109/TAP.2016.2647578.
    Abstract—A dual-band electronically beam-switching antenna using a cylindrical active frequency selective surface (AFSS) is presented. The antenna structure consists of a slot AFSS and an omnidirectional dual-band feed antenna. The PIN diodes of half the AFSS are switched ON and OFF respectively to reconfigure the surface as transparent and opaque to the incident EM waves. Thus by controlling the bias voltages to different columns, the directive beams can be swept in 4 steps covering the whole azimuth plane. A design validation based on a metallic reflector antenna is performed to predict the performances of the proposed AFSS antenna. To validate the design concept, the transmission coefficients of the active FSS sheet are experimentally examined. Then an antenna prototype operating at 2.5 GHz and 5.3 GHz frequency bands is fabricated and measured. Simulation and measurement results of the fabricated antenna are presented to verify the design principle. A comparison between this work and previous (single-band) designs is given to better interpret the characteristics of the dual-band AFSS antenna.
  • Gu, C. et al. (2017). 3D-Coverage Beam-Scanning Antenna Using Feed Array and Active Frequency Selective Surface. IEEE Transactions on Antennas and Propagation [Online] 65:5862-5870. Available at: http://dx.doi.org/10.1109/TAP.2017.2754400.
    This paper presents the design of a smart antenna that can achieve three-dimensional beam scanning coverage. The antenna consists of a novel planar feed array and a cylindrical active frequency selective surface (AFSS). First, an array fed metallic reflector is studied as a reference antenna to validate the beam scanning characteristics in the elevation plane. Then the AFSS is assessed through simulation and measurement results. Finally, the complete structure containing the planar collinear array and the AFSS is analyzed. A prototype at S-band has been designed, manufactured and measured. The resulting antenna is shown to be able to operate at the 2.4 – 2.5 GHz frequency band and switch beams in both the azimuth and elevation planes. In the azimuth plane, the proposed antenna is capable of sweeping beams towards different directions to cover a full range of 360˚. In the elevation plane, it can achieve beam steering within an angle range of +16˚/-15˚. The measured maximum gain of the antenna is 9.2 dBi. This is the first report of a low-cost 3D coverage beam scanning antenna based on AFSS.
  • Jun, S. et al. (2017). Circular polarised antenna fabricated with low-cost 3D and inkjet printing equipment. Electronics Letters [Online]. Available at: https://doi.org/10.1049/el.2016.4605.
    The fabrication of a patch antenna using low-cost 3D printing equipment is presented. A circular polarised (CP) patch antenna is manufactured by combining inkjet printing and stereolithography (SLA) technology. The substrate has been fabricated by curing photosensitive resin while the patch element of the antenna has been inkjet printed using silver ink. The printed antenna satisfies the required reflection coefficient, axial ratio and radiation pattern at 1575 MHz. The aim is to demonstrate an inexpensive technology that could be used for the fabrication of antennas on customised 3D printed substrates. The performance of the antenna is summarised through simulations and experimental results.
  • Jun, S. et al. (2017). Manufacturing Considerations in the 3-D Printing of Fractal Antennas. IEEE Transactions on Components, Packaging and Manufacturing Technology [Online] 7:1891-1898. Available at: https://doi.org/10.1109/TCPMT.2017.2730366.
    The use of additive manufacturing (AM) techniques for the fabrication of 3-D fractal monopole antennas is presented. The 3-D printing (3-D P) of 3-D designs based on the Sierpinski fractal concept is studied, and the performance discussed. The AM allows the fabrication of the complex features of these antennas. The specific structures, on the other hand, provide a reduction of the material used in AM compared with the equivalent nonfractal designs, in which two cases can be described by over 75%. This is the first time that 3-D fractals have been studied in terms of volume reduction and their potential benefits to AM of antennas. The first investigated antenna derives from the Sierspinki tetrahedron fractal shape. From this initial design, two new structures have been developed: the dual Sierpinksi fractal and the dual inverse Sierpinski fractal. The new designs offer improved matching and radiation pattern. All the antennas operate at 2.4 GHz used in Bluetooth and wireless LAN band. Furthermore, the final inverse fractal shape is able to cover both the 2.4- and 5.5-GHz WLAN frequencies with a reflection coefficient (S₁₁) better than -10 dB, together with coverage at bands around 8 GHz. This ratio of resonant frequencies is achieved after a series of described design stages. The radiation patterns of the antennas are monopole-like at both bands. The AM technique employed is metal powder embinder printing where a binding material is jetted on a powder bed containing metal particles. Metal 3-D P is ideal for maintaining the mechanical strength of the structures. The envisaged applications are in the defense and aerospace sectors where high-value, lightweight, and mechanically robust antennas can be integrated with other 3-D printed parts. Transient simulations based on the finite integration technique compare well with measurements.
  • Gu, C. et al. (2017). Frequency-Agile Beam-Switchable Antenna. IEEE Transactions on Antennas and Propagation [Online] 65:3819-3826. Available at: https://doi.org/10.1109/TAP.2017.2713978.
    A novel antenna with both frequency and pattern reconfigurability is presented. The reconfigurability is achieved by integrating an active frequency selective surface (AFSS) with feed antenna. The smart FSS comprises a printed slot array loaded by varactors. A novel dc biasing arrangement is proposed to feed the slots vertically so that the unwanted effects caused by bias lines are minimized. A monopole antenna is designed to illuminate the AFSS. The resulting structure can operate in a frequency tuning range of 30%. By reconfiguring the different sections of active FSS cylinder into a transparent or reflector mode, the omnidirectional pattern of the source antenna can be converted to a directive beam. As an illustration, half of the AFSS cylinder is successively biased, enabling the beam switching to cover the entire horizontal plane over a range of frequencies. An antenna prototype was fabricated and measured. Experimental results demonstrate the capability of providing useful gain levels and good impedance matching from 1.7 to 2.3 GHz. The antenna offers a low-cost, low-power solution for wireless systems that require frequency and beam reconfigurable antennas. The proposed design consumes about 1000 times less dc power than the equivalent narrowband beam-switching antenna design using p-i-n diode-loaded AFSS.
  • Mao, C. et al. (2016). A Novel Multiband Directional Antenna for Wireless Communications. IEEE Antennas and Wireless Propagation Letters [Online] 16:1217-1220. Available at: https://doi.org/10.1109/LAWP.2016.2628715.
    A novel multiband patch antenna with unidirectional radiation is proposed by integrating resonators in the design. The multiple frequency bands are achieved based on a coupled resonators network. The topology and design methodology are detailed. The patch not only works as the last-order resonator of the network, but also as the radiating element. Using this approach, multiple bands can be achieved without changing the shape of the radiation element. In addition, the operation bands can be adjusted by adjusting the coupling between the resonators. In this work, the four bands are designed at 4.6, 5.05, 5.8, and 6.3 GHz as a proof-of-concept. The prototype is fabricated and tested, and measured results agree very well with the simulations, showing an excellent performance in terms of impedance matching, radiation patterns, gains, and cross-polarization discrimination.
  • Jun, S., Sanz-Izquierdo, B. and Parker, E. (2016). 3D printing technique for the development of non-planar electromagnetic bandgap structures for antenna applications. Electronics Letters [Online] 52:175-176. Available at: http://doi.org/10.1049/el.2015.3637.
    The use of 3D printing for the development of non-planar electromagnetic bandgap (EBG) structures for antenna applications is proposed. A coplanar waveguide (CPW) fed antenna is tested on a non-planar EBG substrate, fabricated using additive manufacturing techniques. Inexpensive fuse filament fabrication is used as the fabrication process. Silver-loaded conducting ink is employed for the metallic components of the EBG. The CPW antenna on the non-planar EBG structure has a satisfactory reflection coefficient at 2.45 GHz, which is suitable for Bluetooth/WLAN communications. The radiation patterns have reduced back lobes and improved gain compared with the antenna in free space.
  • Mao, C. et al. (2016). An Integrated Filtering Antenna Array With High Selectivity and Harmonics Suppression. IEEE Transactions on Microwave Theory and Techniques [Online]:1798-1805. Available at: http://doi.org/10.1109/TMTT.2016.2561925.
    In this paper, a new design of an antenna array with integrated functions of filtering, harmonics suppression, and radiation is proposed. The device employs a multi-port network of coupled resonators, which is synthesized and designed as a whole to fulfill the functions of filtering, power combination/division, and radiation. The 50-Ω interfaces between the cascaded filter, power divider, and antenna in traditional RF front-ends are eliminated to achieve a highly integrated and compact structure. A novel resonator-based four-way out-of-phase filtering power divider is proposed and designed. It is coupled to the patch array, rendering a fourth-order filtering response. The coupling matrix of the resonator network is synthesized. The physical implementations of the resonators and their couplings are detailed. Compared to a traditional patch array, the integrated filtering array shows an improved bandwidth and frequency selectivity. In addition, the harmonic of the antenna array is suppressed due to the use of different types of resonators. To verify the concept, a 2x2 filtering array at S-band is designed, prototyped, and tested. Good agreement between simulations and measurements has been achieved, demonstrating the integrated filtering antenna array has the merits of wide bandwidth, high frequency selectivity, harmonics suppression, stable antenna gain, and high polarization purity.
  • Mao, C. et al. (2016). Dual-Band Patch Antenna with Filtering Performance and Harmonic Suppression. IEEE Transactions on Antennas and Propagation [Online] 64:4074-4077. Available at: http://dx.doi.org/10.1109/TAP.2016.2574883.
    A novel design of dual-band antenna with integrated filtering performance is proposed. A low-profile aperture-coupled U-slot patch antenna is employed for dual-band operation with a uniform polarization, which is fed by a dual-mode stub-loaded resonator (SLR). The U-slot patch works as a dual-mode resonator of the dual-band filter as well as the radiation element. The odd- and even-mode of the SLR are coupled and tuned with the U-slot patch, generating two 2nd-order operation bands at 3.6 and 5.2 GHz. Compared with the traditional patch antenna, the proposed antenna exhibits improved bandwidth and frequency selectivity. In addition, the bandwidths can be controlled by adjusting the coupling strength between the SLR and the patch. Furthermore, the higher-order harmonics can be suppressed over a broadband without increasing the footprint of the design. Measured and simulated results agree well with each other, showing an excellent performance in terms of impedance matching, bandwidths, 2nd-order filtering, out-of-band rejection, cross polarization discrimination (XPD) and gains at both bands.
  • Liang, B. et al. (2015). A Frequency and Polarization Reconfigurable Circularly Polarized Antenna Using Active EBG Structure for Satellite Navigation. IEEE Transactions on Antennas and Propagation [Online] 63:33-40. Available at: http://dx.doi.org/10.1109/TAP.2014.2367537.
    This paper presents a broadband frequency tunable and polarization reconfigurable circularly polarized (CP) antenna, using a novel active electromagnetic band gap (EBG) structure. The EBG surface employs identical metallic rectangular patch arrays on both sides of a thin substrate, but rotated by 90º from each other. The active bias circuits are also orthogonal for each surface, enabling the reflection phases for orthogonal incident waves to be tuned independently in a wide frequency range. By placing a wideband coplanar waveguide (CPW) fed monopole antenna above the EBG surface, and properly tuning the bias voltages across the varactors in each direction, CP waves can be generated at any desired frequency over a broad band. In accordance with simulations, the measured 3dB axial ratio (AR)bandwidth reaches 40% (1.03-1.54GHz), with good input matching(S11) and radiation patterns at six presented sampling frequencies. The polarization reconfigurability is verified by simulations and measurements, and shown to be capable of switching between left hand circular polarization (LHCP) and right hand circular polarization (RHCP).
  • Gu, C. et al. (2015). Compact Smart Antenna with Electronic Beam-Switching and Reconfigurable Polarizations. IEEE Transactions on Antennas and Propagation [Online]:1-1. Available at: http://doi.org/10.1109/TAP.2015.2490239.
    This paper presents a compact-size, low-cost smart antenna with electronically switchable radiation patterns and reconfigurable polarizations. This antenna can be dynamically switched to realize three different polarizations including two orthogonal linear polarizations and one diagonally linear polarization. By closely placing several electronically reconfigurable parasitic elements around the driven antenna, the beam switching can be achieved in any of the three polarization states. In this design, a polarization reconfigurable square patch antenna with a simple feeding network is used as the driven element. The parasitic element is composed of a printed dipole with a PIN diode. By using different combinations of PIN diode ON/OFF states, the radiation pattern can be switched towards different directions to cover an angle range of 0° to 360° in the azimuth plane. The concept is confirmed by a series of measurements. This smart antenna has the advantages of compact size, low cost, low power consumption, reconfigurable polarizations and beams.
  • Mackay, A., Sanz-Izquierdo, B. and Parker, E. (2014). Evolution of Frequency Selective Surfaces. FERMAT [Online] 2:1-7. Available at: http://www.e-fermat.org/files/articles/1535189605e795.pdf.
    This review gives an account of the route through which Frequency Selective Surfaces have developed in form and in application over the past few decades. Applications range from their use in radome structures, and in meta-materials, to their incorporation into buildings for signal propagation control
    in the built environment. For some of these applications the geometries of the array elements can be very simple, but in cases where surfaces are curved, significantly more complicated configurations are likely to be required. Fabrication cost is an important issue. In applications to multiband radiometry for satellite systems for example, the high cost of precision manufacture is normally considered to be acceptable. In contrast, in the built environment inexpensive larger scale production techniques are important. Inkjet or 3D printing may offer cost effective ways forward.
  • Liang, B. et al. (2014). Cylindrical Slot FSS Configuration for Beam-Switching Applications. IEEE Transactions on Antennas and Propagation [Online] 63:166-173. Available at: http://ieeexplore.ieee.org/xpl/downloadCitations.
    A novel design for a beam-switching antenna using active cylindrical slot frequency selective surface (ACSFSS) is presented. The antenna system is composed of an omnidirectional monopole antenna and the ACSFSS, which employs a new technique of switching slot arrays. The ACSFSS is made up of twelve columns with eight slots each, dividing the cylinder by 30º. To steer the beam of the antenna the diodes are set OFF and ON, so that the radiation pattern of the antenna is determined by the number of OFF state columns. To estimate the general dimension of the cylindrical FSS, an equivalent metallic reflector is introduced
    and optimized, and then parametric studies for the unit cell dimensions are discussed. The fabricated prototype works within the WLAN band, centered around 2.45GHz, and can agilely select either a narrow-beam or wide-beam operating mode. Simulation and measurements confirm the operation of the ACSFSS antenna,
    with good matching and gain observed. In particular, the narrow-beam mode -3dB beamwidth is 47º which offers enhanced angular resolution compared with other reported beam-sweeping work.
  • Sanz-Izquierdo, B. and Parker, E. (2014). Dual Polarized Reconfigurable Frequency Selective Surfaces. IEEE Transactions on Antennas and Propagation [Online] 62:764-771. Available at: http://dx.doi.org/10.1109/TAP.2013.2292056.
    Novel band-stop active frequency selective surfaces (FSS) capable of modifying their response for different polarizations are proposed. Geometries based on full rings, and split rings are employed. The designs using full rings are able to tune over a wide frequency range while designs using split rings tune in a narrow frequency band. Both structures use a new biasing methodology which allows independent control of rows and columns of FSS arrays, therefore permitting independent modification of the transmission responses at the vertical and horizontal polarizations. Convoluting the shape of the elements significantly reduces the sensitivity to angle of wave incidence. The aim is to demonstrate a technology that could be used for various applications including modification of the electromagnetic architecture of buildings and the control of electromagnetic wave propagation to improve the efficiency of radio spectrum use. The surfaces incorporate commercially available, low cost, varactor diodes and surface mount resistors. Theoretical and experimental results confirm the operation of the surfaces within the UHF frequency band.
  • Sanz-Izquierdo, B. and Parker, E. (2014). 3D Printing of Elements in Frequency Selective Arrays. IEEE Transactions on Antennas and Propagation [Online] 62:6060-6066. Available at: http://dx.doi.org/10.1109/TAP.2014.2359470.
    3-D printing is a technology that enables the fabrication of complex objects directly from a digital model. Folding the elements of Frequency Selective arrays in three dimensions gives a significant reduction in the resonant frequency for a given cell dimension, and such structures are candidates for additive manufacture. The aim in this paper is to demonstrate by example the development of novel electromagnetic structures that could be fabricated in parallel and integral with the additive manufacture of buildings, for electromagnetic architecture control. The principle is illustrated with two new geometries based on dipole and loop elements. The cores of these structures were fabricated with a 3-D printer that uses a plaster-based material. Theoretical and experimental results confirm the operation of the surfaces within the UHF frequency band.
  • Sanz-Izquierdo, B. and Parker, E. (2013). 3D printing technique for fabrication of frequency selective structures for built environment. Electronics Letters [Online] 49:1117-1118. Available at: http://dx.doi.org/10.1049/el.2013.2256.
    The frequency selectivity of an array of triple cross elements fabricated using an additive manufacturing technique is assessed, to demonstrate the feasibility of using three-dimensional (3D) printing techniques in frequency selective structure production. The process is a candidate for the fabrication of frequency sensitive components in buildings, in situations where the electromagnetic architecture is an important consideration. As a simple symmetrical 3D element, the triple cross is part of a class of elements suitable for crystal-like configurations. The basic performance of the array is summarised through simulations and experimental results.
  • Sanz-Izquierdo, B., Parker, E. and Batchelor, J. (2011). Switchable Frequency Selective Slot Arrays. IEEE Transactions on Antennas and Propagation 59:2728-2731.
    A switchable frequency selective surface (FSS) made of square loop slots and PIN diodes connected to a novel separate biasing circuit is presented. The structure uses a very thin, flexible substrate sandwiched between two physically independent metallic layers to create the active filter. An application is the modification of the EM architecture of buildings, where propagation could be controlled using active FSS. The relatively small number of elements employed creates a compact FSS structure which could fit in an aperture within a wall of a building. The Fabry-Perot approach is used to design a cascaded version for improved filter selectivity.
  • Sanz-Izquierdo, B. et al. (2011). Wideband FSS for Electromagnetic Architecture in Buildings. Applied Physics A: Materials Science & Processing [Online] 103:771-774. Available at: http://dx.doi.org/10.1007/s00339-011-6337-9.
    Interweaving the elements of a frequency selective surface (FSS) is a technique that allows wideband frequency filtering as well as size reduction. FSS structures using this method are well suited to wireless indoor applications where the operating bands are spread over a wide spectrum. Interwoven square loop slots FSS have been designed, fabricated and measured. The FSS structure to be presented offers transparency at the emergency services band at around 400 MHz and suppresses most of the mobile and wireless bands up to 3 GHz. The size of the unit cell developed is around 3% of the corresponding wavelength, significantly smaller than a half wavelength resonant dipole.
  • Xu, R., Sanz-Izquierdo, B. and Young, P. (2011). Switchable Substrate Integrated Waveguide. IEEE Microwave and Components Letters [Online] 21:194-196. Available at: http://dx.doi.org/10.1109/LMWC.2011.2108274.
    A switchable substrate integrated waveguide is presented that can be switched between two different modes of propagation via the biasing of a pin diode switch. To demonstrate the usefulness of the design a single pole single through (SPST) waveguide switch is presented. The switch is shown to have approximately 50 dB isolation and 3 dB insertion loss over the switchable bandwidth.
  • Parker, E. et al. (2010). Frequency Selectively Screened Office incorporating Convoluted FSS Window. Electronics Letters 46:317-318.
    The frequency selectivity of small single and double layer FSS windows built into an office enclosure and employing highly miniaturised interwoven array elements is assessed across the frequency range from 200 MHz to 2 GHz. The aim of providing an emergency services passband at about 400 MHz while providing isolation of at least 15 dB above 600 MHz is achieved.
  • Sanz-Izquierdo, B. et al. (2010). Singly and Dual Polarized Convoluted Frequency Selective Structures. IEEE Transactions on Antennas and Propagation [Online] 58:690-696. Available at: http://dx.doi.org/10.1109/TAP.2009.2039321.
    Convoluting the elements of frequency selective surfaces produces resonating structures with very small unit cell dimensions. This feature is attractive when the FSS is to be used at low frequencies, mounted on a curved surface, or when placed in the proximity of compact radiators. The characteristics of single and dual polarized convoluted FSS are analyzed and measured. The development of novel convoluted elements derived from the square loop slot is traced and their performance is examined. A novel technique of interweaving convoluted loops allows for further cell size reduction, while increasing the passband width, introducing flexibility in wideband FSS design, particularly for tailoring the Electromagnetic Architecture of buildings, and mobile communications in the built environment. Simulated transmission responses of the convoluted structures are in good agreement with the measurements.
  • Sanz-Izquierdo, B., Parker, E. and Batchelor, J. (2010). Dual-Band Tunable Screen using Complementary Split Ring Resonators. IEEE Transactions on Antennas and Propagation [Online] 58:3761-3765. Available at: http://dx.doi.10.1109/TAP.2010.2072900.
    Active frequency selective surfaces (FSS) based on slot-form split ring resonators are described. Switching and tuning have been achieved using two different biasing circuit configurations. The first design switches ON and OFF the two concentric rings separately, producing four distinct transmission responses. The second design is able to vary the capacitance of the two split rings, allowing independent dual-band frequency tuning. The active FSS incorporate commercially available, low cost, surface mount switched PIN diodes and varactor diodes. The operation of the surfaces covers a wide band frequency range within the UHF spectrum, which is desirable for applications such as the modification of the EM architecture of buildings. Measurements compare well with the simulations.
  • Sanz-Izquierdo, B. et al. (2010). Tuning Patch-Form FSS. Electronics Letters 46:329-330.
    The application of a novel biasing technique to tune frequency selective surfaces (FSS) made of patch elements is described. The methodology follows a recently developed technique where the biasing circuit of an active FSS is etched at the rear of a double sided substrate. On this occasion, the structure consists of dipole patches on one side of the thin polyester substrate and the housing circuit at the rear, electromagnetically hidden by the patches. Varactor diodes are employed to modify the capacitance between the patches. The novel active FSS structure is able to tune a bandstop filter response over a wide frequency range, which could suit applications such as the time dependent modification of the EM architecture of buildings.

Conference or workshop item

  • Jun, S. et al. (2017). A Fractal Tetrahedron Antenna Fabricated Using Metal 3D printing. in: 2017 IEEE AP-S Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting.. Available at: http://2017apsursi.org/Papers/ViewPapers_MS.asp?PaperNum=2409.
    Sierpinski tetrahedron fractal antenna is fabricated using metal additive manufacturing techniques. Metal 3D printing is able to fabricate the complex internal and external features while providing acceptable mechanical strength. The main advantage of this type of fractals is that it is able to reduce the amount of material used in additive manufacturing processes. This can also lead to weight reduction, an important factor in aerospace and defense applications. Selective laser melting of metal powder has been employed for the fabrication. The input matching has been optimized for a first resonance at the 2.4GHz, making it suitable for existing wireless communications. The basic performance of the antenna is summarized through simulations and experimental results.
  • Jun, S. et al. (2017). Inkjet Printed Dual-Band Origami Frog Antenna. in: 2017 IEEE AP-S Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting.. Available at: http://2017apsursi.org/Papers/ViewPapers.asp?PaperNum=2694.
  • Shastri, A. et al. (2017). Switchable slot antenna using close-coupled biasing technique. in: Electromagnetics in Advanced Applications (ICEAA), 2017 International Conference on. IEEE, pp. 1377-1380. Available at: https://doi.org/10.1109/ICEAA.2017.8065533.
    Abstract:
    This paper presents a reconfigurable slot antenna that uses a close-coupled biasing technique to facilitate the switching between two frequency bands. The technique uses a very thin double layered flexible copper clad Mylar substrate with the slot antenna on the front side and the biasing circuits at the backside of the design. The biasing circuit uses a conventional PIN diode to switch between ON and OFF states. Each state corresponds to a separate operating band. The switching from one sub-band to another is done electronically by means of a BAR64 diode. In this first example, the two bands are located close to each other to increase the bandwidth of the antenna. The resulting -10dB bandwidth increases by 20% as compared with the OFF-state. The antenna has mostly omnidirectional radiation patterns at the two frequency bands. Simulation and measurement results are compared and discussed which are to be in good agreement with one another.
  • Gu, C., Gao, S. and Sanz-Izquierdo, B. (2017). Low-cost wideband low-THz antennas for wireless communications and sensing. in: 10th UK-Europe-China Workshop on Millimetre Waves and Terahertz Technologies (UCMMT), 2017. IEEE. Available at: https://doi.org/10.1109/UCMMT.2017.8068470.
    Terahertz technology is expected to provide a significant improvement in wireless system performance. A common assumption is that traditional microwave devices can be scaled down to operate at higher frequency bands. However, it can be a challenge to directly transfer the design methodology from microwave to THz band as the size of the devices becomes a few millimeter large. The reduced antenna size at the THz band limits the suitable fabrication processes. This paper reviews a wide range of THz antennas and their fabrication methodology. Then based on the resonant cavity antenna concept, an all-metal 300 GHz wideband high-gain antenna is designed and simulated. The presented metallic antenna is suitable to be fabricated using 3D printing techniques, which can lead to a low-cost, reliable solution for the emerging THz applications.
  • Gu, C., Gao, S. and Sanz-Izquierdo, B. (2017). Wideband low-THz antennas for high-speed wireless communications. in: Electromagnetics in Advanced Applications (ICEAA), 2017 International Conference on. IEEE, pp. 141-145. Available at: https://doi.org/10.1109/APWC.2017.8062263.
    This paper presents a brief review of low THz antennas and discusses their corresponding manufacturing techniques. In addition, a new antenna is introduced for the 300 GHz frequency band. The design is an all-metal structure with interesting features such as compactness, high gain, and wide operational bandwidth. These characteristics make it a promising solution for future high-speed THz communication systems.
  • Jun, S., Heirons, J. and Sanz-Izquierdo, B. (2017). Inkjet printed dual band antenna for paper UAVs. in: 11th European Conference on Antennas and Propagation (EUCAP), 2017. Institute of Electrical and Electronics Engineers (IEEE), pp. 3452-3456. Available at: https://doi.org/10.23919/EuCAP.2017.7928707.
    A dual band antenna is inkjet-printed and then folded as part of a paper unmanned aerial vehicle (UAV). The patterns of the antenna are reproduced on a standard photo paper substrate using an off the shelf inkjet printer. Readily available cartridges with nanoparticle silver conductive ink are employed. A single-layer planar antenna is fed by coplanar waveguide (CPW). The geometry of the radiating element consists of a semicircle with a centered square slot. In order to examine the effect of bending on performance, the antenna is tested unfolded and then folded when integrated onto the airplane. Two configurations of the folded antenna on the plane are analyzed. The aim is to investigate the feasibility of fabricating foldable antennas for paper airplanes using low-cost inkjet printing techniques. The antenna operates at the existing 2.4 GHz and 5.2 GHz WLAN bands. Finite different time domain simulations compare well with measurement.
  • Sanz-Izquierdo, B. et al. (2016). Inkjet printed and folded LTE antenna for vehicular application. in: 46th European Microwave Conference (EuMC), 2016. Institute of Electrical and Electronics Engineers (IEEE), pp. 88-91. Available at: https://doi.org/10.1109/EuMC.2016.7824284.
    A multi-band antenna suitable for Long-term Evolution (LTE) is inkjet-printed, and then folded around a cylindrical form. The plastic cylinder is also printed using additive manufacturing techniques, as a separate process. The antenna is based on a planar wideband monopole radiator concept with an additional resonator for the LTE700 frequency band. The aim is to study the potential of low-cost additive manufacturing (AM) techniques for the development of vehicular antennas. Two antennas have been fabricated, one on paper substrate, and a second on polyethylene terephthalate (PET) substrate. The one on paper is tested as a planar monopole antenna on a large ground plane. The one printed on PET is shaped onto the cylindrical form. The main aim is to investigate the use of low-cost inkjet printing techniques for the fabrication of disposable vehicular antennas that can be upgraded regularly. The antennas successfully operate at all LTE and mobile frequency bands. Finite different time domain simulations compare well with measurements.
  • Heirons, J. et al. (2016). Inkjet printed GPS antenna on a 3D printed substrate using low-cost machines. in: Loughborough Antennas & Propagation Conference (LAPC), 2016. Institute of Electrical and Electronics Engineers (IEEE), pp. 1-4. Available at: https://doi.org/10.1109/LAPC.2016.7807590.
    Additive manufacturing (AM), also known as 3D printing, is a process of fabricating a 3D digital design by printing layer after layer. 3D printing has advanced very rapidly in recent years and has become an alternative to traditional manufacture methods for customized objects. Originally intended for the prototyping of mechanical objects, this technique has expanded into different areas such as biomedical [1] and electronics [2]. Within electronics, antennas and microwave engineering can greatly benefit from this technology. Researchers have already demonstrated the potential applicability of 3D printing in this field. Light weight waveguides have been fabricated by copper plating plastics forms [3]. Substrates for antenna applications have been modified and new properties have been found with the assistance of additive manufacturing [4]. Novel frequency selective structures (FSS) have been developed by fully [5] and partially [6] metalizing 3D printed elements. Non-uniform electromagnetic band gap structures have been fabricated on printed substrates [7]. Antennas have been placed onto wearables and tested on 3D printed phantoms [8]–[9]. Fig. 1.
  • Sanz-Izquierdo, B. et al. (2016). An application of active frequency selective surface to reconfigurable antenna technology. in: Active and Passive RF Devices Seminar. London, UK: IET. Available at: http://doi.org/10.1049/ic.2016.0006.
    This paper illustrates the use of active frequency selective surfaces (FSS) in reconfigurable antennas. A patch-form dual-polarized tunable FSS is adapted for use as an active artifi-cial magnetic conductor (AMC). As with the tunable FSS, the ac-tive AMC offers independent tuning capability of the reflection phases for two polarisations of incident EM waves. By combining the AMC with a wideband coplanar waveguide fed monopole an-tenna, circularly polarisation (CP) capability is realized at any fre-quency over the 1.15-1.60GHz band. Furthermore, the CP state can be switched between left hand CP and right hand CP, by simply interchanging the capacitances of varactors controlling the reflection phases of the two orthogonal polarised waves. The an-tenna covers the frequency bands of all operational and in-prepa-ration satellite navigation systems, including GPS, GLONASS, Beidou and Galileo. polarization reconfigurable circular polar-ized (CP) antenna using active artificial ground (AG) structure
  • Shastri, A. et al. (2016). Evaluation of a low-cost inkjet printed slot antenna for energy harvesting applications. in: Loughborough Antennas & Propagation Conference (LAPC), 2016. Institute of Electrical and Electronics Engineers (IEEE), pp. 1-5. Available at: https://doi.org/10.1109/LAPC.2016.7807593.
    A circularly polarized patch antenna fabricated using commercially available, low-cost, printers is described. Two additive processes are combined for the fabrication: stereolithography (SLA) and inkjet printing of silver inks. A widely available SLA 3D printer is employed to fabricate the substrate of the antenna. Inkjet printing is used to deposit the metallic layers of the radiating element on the substrate. The two machines employed are very low-cost in comparison to those used in previously reported work. Good adhesion of the metallic patterns to the substrates is observed. Furthermore, the resistance of the added metallic patch is relatively low. The aim is to demonstrate the use of alternative, inexpensive machines, for the prototyping and manufacturing of antennas on 3D printed substrates. In this work, the antenna operates at the 1.575GHz GPS frequency band. Finite-difference-time-domain simulations compare well with the practical experiments.
  • Liang, B. et al. (2015). Frequency Tunable and Circular Polarization Switchable Antenna using Dual Polarized Active Artificial Ground Structure. in: European Conference on Antennas and Propagation EuCAP 2015. Piscataway, NJ : IEEE.
    This paper presents a frequency and polarization reconfigurable circular polarized (CP) antenna using active arti-ficial ground (AG) structure. The active AG structure offers independent and symmetrical tuning capability of the reflection phases for dual polarized incident waves. By combining the AG structure with a wideband coplanar waveguide fed monopole antenna, and tuning the capacitances of the varactor diodes on the AG structure, CP wave is dynamically realized at any desired frequency over a wide band in the 1.15-1.60GHz range. At each frequency, the CP state is switchable between left hand CP and right hand CP, by simply swapping the capacitances of varactors controlling the reflection phases of the two orthogonal polarized waves. The antenna covers the frequencies of all operational and in-preparation satellite navigation systems, including GPS, GLONASS, Beidou and Galileo.
  • Sanz-Izquierdo, B. and Parker, E. (2015). Frequency Selective Surfaces Formed by Partially Metalising 3D Printed Shapes. in: 9th European Conference on Antennas and Propagation (EuCAP), 2015. IEEE, pp. 1-4.
    The use of additive manufacturing (AM) techniques for the development of 3D frequency selective structures is discussed. The type of structures introduced use 3D printing to form the shape of the elements which are then coated with conductive paint. Fully and partially metalised array elements are studied. Fully metalised elements offer mechanically robust structures as well as reliability in the transmission responses. By controlling current paths, partially metalised structures can offer lower frequency operation and stability to angle of wave incidence. They are also a more efficient use of conductive material. The element dimensions suit the long wavelengths employed in wireless communications and assist in controlling electromagnetic wave propagation in buildings.
  • Sanz-Izquierdo, B. and Parker, E. (2015). Fully and Partially Metallised 3D Printed FSS Elements. in: RF Technology for Aerospace.
  • Mao, C. et al. (2015). Integrated filtering-antenna with controllable frequency bandwidth. in: 9th European Conference on Antennas and Propagation (EuCAP), 2015.
    An integrated design of a band-pass filter and a patch antenna is proposed in this paper by using an aperture coupled structure. Traditionally, the microwave filter and antenna are designed separately using 50 Ohm interface and then connected by transmission lines, which lead to a large size and more loss. Here, the antenna and microwave filter are directly integrated without a 50 Ohm interface between them. Compared with the traditional cascade designing, the co-design of filter and antenna has a more compact size, simpler configuration, improved frequency selectivity and higher system efficiency. The frequency bandwidth also can be controlled by adjusting the dimension of the coupling aperture in the ground. The measured results agree very well with the simulations, showing the filtering-antenna has good performance in impedance matching, radiation pattern and antenna gain.
  • Jun, S. and Sanz-Izquierdo, B. (2015). A CPW-fed antenna on 3D printed EBG substrate. in: Antennas & Propagation Conference (LAPC), 2015. pp. 1-5. Available at: http://doi.org/10.1109/LAPC.2015.7366063.
    This paper proposes a coplanar waveguide (CPW) fed antenna and electromagnetic band gap (EBG) structure on 3D printed substrates. Low-cost fuse filament fabrication (FFF) technology is employed. Two sets of experiments are described. In the first, the antenna and EBG patterns are etched on copper clad Mylar® polyester film and attached to the 3D printed substrates. In the second, the patterns of the EBG are added using silver conductive paint. Both experiments compare very well between them, and with the simulations. The EBG structure provides improved antenna performance such as gain, efficiency and directivity. The antenna and EBG are designed for the 2.4 GHz Bluetooth frequency band. The Finite-difference time-domain (FDTD) computational method was used for the study.
  • Sanz-Izquierdo, B., Jun, S. and Baydur, T. (2015). MIMO LTE Vehicular Antennas on 3D Printed Cylindrical Forms. in: IEEE. Available at: http://doi.org/10.1049/ic.2015.0145.
    A multi-band antenna suitable for Long-term Evolution (LTE) is shaped around a 3D printed cylindrical form, and arranged in a MIMO configuration. The antenna is based on a planar wideband monopole radiator with an additional resonator for the LTE700 frequency band. Conforming the antenna onto a cylindrical shape reduces its length while keeping performance. It also reduces the space used by the MIMO antenna system. Furthermore, the plastic cylinder improves the mechanical strength of the supporting substrate for the radiating element. The aim is to study the potential of additive manufacturing (AM) of substrates for the development of conformal vehicular antenna. Two antennas have been fabricated, one etched on a copper clad Mylar substrate, and a second painted directly onto the cylindrical form. The two antennas have been measured and the results are compared. Two copper based antennas have been tested in a MIMO configuration. The antennas successfully operate at all LTE and mobile frequency bands. Finite different time domain simulations compare well with measurements.
  • Jun, S., Sanz-Izquierdo, B. and Summerfield, M. (2015). UWB antenna on 3D printed flexible substrate and foot phantom. in: 2015 Loughborough Antennas & Propagation Conference (LAPC). Loughborough: IEEE, pp. 1-5. Available at: http://doi.org/10.1109/LAPC.2015.7366100.
    An ultra-wideband (UWB) monopole antenna on an additive manufactured (AM) flexible substrate for foot wear application is proposed. The 3D printing of foot phantoms for the testing of this type of antennas is also introduced. Inexpensive fuse filament fabrication (FFF) technology is utilized for these developments. Flexible polylactic acid plastic filament (PLA) material is used for the antenna while transparent PLA for the phantom. The antenna is intended for integration into the footwear tongue. The UWB monopole antenna achieves -10dB input impedance matching from 3.1GHz to over 10.6GHz in freespace, on the foot phantom and on the real human body. Simulation and measurement confirm the ultra-wideband operation of the antenna.
  • Sanz-Izquierdo, B. and Sungyun, J. (2014). WLAN antenna on 3D printed bracelet and wrist phantom. in: Loughborough Antennas & Propagation Conference (LAPC). pp. 372-375. Available at: http://dx.doi.org/10.1109/LAPC.2014.6996400.
    A WLAN antenna shaped around a 3D printed bracelet and tested on another printed phantom is proposed. The antenna is a planar dipole with three resonant elements at each end. Inexpensive fuse filament fabrication (FFF) of polylactic acid plastic (PLA) material has been employed for the manufacturing of the bracelet, and the phantom. The phantom was fabricated as a hollow structure which was filled with a solution consisting of water, salt and sugar. The aim is to demonstrate the potential of personal manufacturing of wearable antenna, and body phantoms for radio frequency testing. The antenna successfully operates at the 2.4GHz and 5GHz frequency bands on and off the body.
  • Liang, B. et al. (2014). Active FSS enclosed Beam-switching Node for Wireless Sensor Networks. in: EuCAP 2014.. Available at: http://www.eucap2014.org/.
    A wireless node with beam-switching and beam-sweeping features for wireless sensor networks (WSNs) is proposed. A readily available Virtual Sense wireless node which makes use of 2.4GHz IEEE 802.15.4 wireless transceivers, as well as active cylindrical slot frequency selective surfaces (FSSs) are employed. The active FSS is made up of twelve columns with four hybrid slots each, dividing the cylinder by 30º. The dimension of the cylinder is calculated to enclose the node with a folded dipole antenna in the center, so that compactness can be maintained. By changing the configuration of the active PIN diodes, omnidirectional and swept directional signal transceiving of nodes can be switched agilely. The work can make communication in nodes controllable depending on the demands of application, and bring flexibility and compatibility in WSNs.
  • Sanz-Izquierdo, B. and Leelaratne, R. (2014). Vehicular LTE Antenna on an Additive Manufactured Cylindrical Form. in: LAPC 2014.
  • Sanz-Izquierdo, B. and Leelaratne, R. (2013). Evaluation of wideband LTE antenna configurations for vehicle applications. in: Antennas and Propagation Conference (LAPC), 2011 Loughborough. IEEE, pp. 383-387. Available at: http://dx.doi.org/10.1109/LAPC.2013.6711925.
    An analysis of different configurations of two identical LTE antennas suitable for vehicle applications is described. The antenna used for the study is a variation on the ultra wideband monopole principle and covers all the frequency bands required for the Long-Term Evolution (LTE) standard. The design is intended for roof mount position on large vehicles for public transportation. Computational studies of the coupling between the two antennas at different locations on a metallic ground plane are included. Simulations were carried out using CST Microwave Studio. Initial measurements confirm the operation of the antenna.
  • Sanz-Izquierdo, B. et al. (2011). Body Armour with Integral High Impedance Surface. in: 5th European Confernce on Antennas and Propagation (EUCAP). pp. 1061-1064.
    This paper describes the performance of high impedance surfaces (HIS) integrated into body armour equipment. A protective insert made of Aramid material and a metallic woven layer is used as the dielectric material with a metallic ground plane of the HIS. The frequency selective layer added to create the high impedance surface consists of a 15x15 array of interwoven spiral elements capable of reducing size of the cell by over 98% compare to the typical square patch element. The HIS has been designed to operate at around the 400MHz band TETRA employed by the police and emergency services in Europe. The HIS is able to improve the matching of the antenna by over 7dB compared to the antenna mounted directly on the armour vest. The paper includes simulations and experiments.
  • Sanz-Izquierdo, B., Batchelor, J. and Parker, E. (2011). Integration of Antennas and High Impedance Surfaces in Ceramic Body Armour Plates. in: IEEE International Conference on Microwave Technology and Computational Electromagnetics (ICMICE2011). pp. 77-80.
  • Sanz-Izquierdo, B. et al. (2010). Interwoven Loops for Electromagnetic Architecture of Buildings. in: International Symposium on Antennas and Propagation. pp. 1-4.
    Convoluting array the elements of an FSS can considerably reduce the size of the unit cell and perform well when incorporated into curved surfaces. In addition, convoluting FSS elements improves the angular stability of the frequency responses of the surface, moving the operating bands away from the grating region determined by the periodicity of the array.
    Interweaving is a technique for closely packing the elements of a frequency selective surface whose main effect is a substantial increase in reflection bandwidth. This paper will present the development of interwoven square loop slots elements for improving the Electromagnetic Architecture of buildings.
  • Sanz-Izquierdo, B. et al. (2010). Wideband FSS for Electromagnetic Architecture in Buildings. in: 2nd International Conference on Metamaterials, Photonic Crystals and Plasmonics.