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2020-02-12
PIER C
Vol. 99, 251-267, 2020
download: 208
Space-Borne Compressed Sensing Based Receiver for Accurate Localization of Ground-Based Radars
Esmaeil Ramezani Mohammad Farzan Sabahi Seyyed Mohammad Saberali
Space borne accurate emitter localization has become an important and indispensable part of electronic warfare (EW) systems. In this paper, a system-level approach to design space borne receiver for accurate localization of long range co-channel radars (e.g. a network of similar surveillance radars) is presented. Due to the wide frequency range of modern radar signals, the receiver should have wide instantaneous bandwidth and requires high sampling rate analog-to-digital converters (ADCs). To address this issue, we propose a receiver structure with an appropriate sub-Nyquist sampling scheme and fast sparse recovery algorithm. The proposed sub-Nyquist sampler employs a three dimensional uniform linear array (ULA), followed by a modulated wideband converter (MWC). To accurately estimate the location of the co-channel radars from sub-Nyquist samples, a novel quad-tree variational Bayesian expectation maximization (QVBEM) algorithm is proposed. The QVBEM algorithm minimizes the computational load and grid mismatch error by iteratively narrowing the search area. This is done by smart grid refinement around radars' locations. To evaluate the performance of the proposed receiver, location finding of pulsed radars is studied through numerical simulations in various scenarios. The results show that the proposed QVBEM method has a significantly lower estimation error than conventional deterministic and Bayesian approaches, with a reasonably computational complexity.
SPACE-BORNE COMPRESSED SENSING BASED RECEIVER FOR ACCURATE LOCALIZATION OF GROUND-BASED RADARS
2020-02-11
PIER C
Vol. 99, 239-250, 2020
download: 158
Thermal Analysis of Bearingless Switched Reluctance Motor
Binbin Zhang Zewei He
A bearingless switched reluctance motor (BSRM) has the same body structure as a switched reluctance motor (SRM), but the winding method is different. The accurate analysis of thermal characteristics is especially important for the service life and safety performance of the two motors. According to the initial design parameters, the initial size calculation equations of SRM and BSRM are given, and the ontology design parameters are obtained according to the same design goal. The two-dimensional finite element model is established, and the stator rotor iron loss is analyzed. The distribution characteristics of iron loss of SRM and BSRM are summarized. Secondly, the three-temperature field model of the motor is built, and the reasonable boundary conditions are set. The temperature distribution law of the two motors is analyzed. It is concluded that the BSRM components have lower loss and lower temperature rise under the same design target.
THERMAL ANALYSIS OF BEARINGLESS SWITCHED RELUCTANCE MOTOR
2020-02-10
PIER C
Vol. 99, 221-238, 2020
download: 266
A Miniature Implanted Antenna for UHF RFID Applications
Van Hieu Nguyen Aliou Diallo Philippe Le Thuc Robert Staraj Stephane Lanteri Georges F. Carle
In this paper, the design of a miniature antenna dedicated to be implanted in a small animal and intended to work in the European UHF RFID (865-868 MHz) band is presented. One of the goals of this work is the miniaturization of the radiating element while preserving its efficiency to allow a reliable communication between an external interrogating reader and the implanted device. The radiating element is a small rectangular loop antenna associated with a dipole allowing impedance matching. The antenna has dimensions of 2.4 mm x 25.4 mm x 0.5 mm and integrates an Impinj Monza 4 chip presenting an impedance of 5.5-j74 Ohms at 868 MHz. The antenna is designed and optimized by using the ANSYS HFSS software. The obtained results show a simulated radiation efficiency of 0.7% and simulated total gain of -17.5 dBi. A prototype is realized, and RSSI measurements have demonstrated the possibility of reliable wireless communications between the implanted antenna and an external reader. In addition, Specific Absorption Rate (SAR) calculation indicates that this implanted antenna meets the required safety regulations.
A MINIATURE IMPLANTED ANTENNA FOR UHF RFID APPLICATIONS
2020-02-10
PIER C
Vol. 99, 209-219, 2020
download: 540
A Novel Broadband Double Whip Antenna for Very High Frequency
Hengfeng Wang Chao Liu Huaning Wu Xu Xie
In this paper, a new type of single loaded broadband double-whip antenna is designed for very high frequency (VHF). The simulation model by moment method is established to analyze the influence of antenna spacing on the performance of a double-whip antenna. The location of antenna loading and the parameters of loading network and broadband matching network are optimized by grasshopper optimization algorithm, and the voltage standing wave ratio (VSWR), gain, pattern and roundness of double-whip antenna are calculated. In fact, a fabricated prototype of the proposed antenna is realized. The measured VSWR is consistent with the simulation results, which is less than 3 at all frequencies, with an average value of 1.89; the maximum directional gain is greater than 2.01 dB, with a maximum of 6.44 dB and average value of 3.79 dB; the minimum roundness of antenna gain is 0.03 dB (at 30 MHz), and the maximum roundness is 1.87 dB (at 300 MHz); the efficiency is all over 51%, with a maximum value of 79% and an average value of 60.71%.
A NOVEL BROADBAND DOUBLE WHIP ANTENNA FOR VERY HIGH FREQUENCY
2020-02-10
PIER C
Vol. 99, 193-208, 2020
download: 384
Gain Enhancement of an UWB Antenna Based on a FSS Reflector for Broadband Applications
Avula Swetha Kurukundu Rama Naidu
In this paper, a novel semi-circular ultra wide-band antenna inspired by a complementary split ring resonator for enhancement of bandwidth and a frequency selective surface reflector for gain enhancement is proposed for broadband applications. Initially, an ultra wide-band antenna employing a pair of L-shaped resonators and complementary split ring resonators is proposed which provides a wide impedance bandwidth of 130.3% from 3.16 to 15 GHz with -10 dB return loss. Finally, a frequency selective surface reflector is employed below the suggested ultra wide-band antenna to enhance the gain. The dimensions of the coplanar waveguide fed ultra wide-band antenna are 35 × 30 × 1.6 mm3 and those of the ultra wide-band antenna with a frequency selective surface reflector, which consists of 10 × 10 array of elements located at a distance of 17 mm below the proposed antenna, are 53.15 × 53.15 × 1.6 mm3. A parametric analysis of substrate dimensions of ultra wide-band antenna and the distance between ultra wide-band antenna and frequency selective surface reflector is performed. The average peak gain of the proposed antenna increases from 4.9 dB to 10.9 dB, which operates at 3.79 GHz, 4.44 GHz, 7.89 GHz, 9.01 GHZ, and 11.15 GHz proposed for broadband applications. With the help of ANSYS, the signal correlation of the proposed antenna is analysed by time domain analysis using similar antennas in face-to-face and side-to-side scenarios. The simulated results of the proposed model are in correlation with experimental ones of the prototype model.
GAIN ENHANCEMENT OF AN UWB ANTENNA BASED ON A FSS REFLECTOR FOR BROADBAND APPLICATIONS
2020-02-07
PIER C
Vol. 99, 179-191, 2020
download: 439
Design of Sub-THz Beam Scanning Antenna Using Luneburg Lens for 5G Communications OR Beyond
Thevaruparambil Abdulnazer Nisamol Kunnath Kodakkat Ansha Parambil Abdulla
This work presents the design and simulation of a beam scanning antenna at 300 GHz using Luneburglens for 5th generation communication applications or beyond. The basic antenna consists of a highly directional Yagi-Uda antenna with lens shaped configuration (substrate lens antenna - SLA) and designed using multiple parallel elements such as one reflector and one driven element with 6 directors. The SLA is focused by Luneburg lens, which is modeled using a unique foam material AirexR82 with relative dielectric constant of 1.12, and it is pressed to realize different dielectric constants in order to obey the index law inside the lens. The final nine - element array of SLA integrated with Luneburg lens provides a 50% increase in bandwidth compared with conventional Yagi-Uda antenna along with an increase in the gain of 31.3% compared with single SLA. The designed model can achieve a beam scan coverage up to 146˚ with a maximum gain of 17.1 dBi and an estimated efficiency of 92.9%. The beam scanning antenna provides a wide bandwidth of 83 GHz starting from 289 GHz to 372 GHz. The analysis of the proposed antenna is done in CST suite and is validated using HFSS software.
DESIGN OF SUB-THZ BEAM SCANNING ANTENNA USING LUNEBURG LENS FOR 5G COMMUNICATIONS OR BEYOND
2020-02-07
PIER C
Vol. 99, 167-178, 2020
download: 212
Phase-Only Nulling with Limited Number of Controllable Elements
Ahmed Jameel Abdulqader Jafar Ramadhan Mohammed Raad H. Thaher
In this paper, the required array patterns with controlled nulls are obtained by optimizing only the excitation phases of a small number of elements on both sides of the array. A genetic algorithm is used to appropriately find which elements of the array to be optimized and also to find the required number of the excitation phases. The performance of the proposed phase-only method is compared with some other exciting methods, and it is found to be competitive, fulfill all the desired radiation characteristics, and represent a good solution for interference mitigation. Moreover, the proposed phase-only array is designed and validated under realistic electromagnetic effects using CST full wave modeling. Experimental results are found in a good agreement with the theoretical ones and show realistic array patterns with accurate nulls.
PHASE-ONLY NULLING WITH LIMITED NUMBER OF CONTROLLABLE ELEMENTS
2020-02-07
PIER C
Vol. 99, 157-165, 2020
download: 436
Dual-Band MIMO Antenna Array for Compact 5G Smartphones
Guobo Wei Quanyuan Feng
An eight-port antenna system for fifth-generation (5G) multi-input multi-output (MIMO) mobile communication in smartphones is proposed, working in 3.5 GHz frequency band (3400-3600 MHz) and 5 GHz frequency band (4800-5100 MHz). The presented eight-port antenna array consists of four vertical structure antennas placed at four corners and four horizontal structure antennas etched along the two long sides of the circuit board. The height of vertical structure is only 4 mm, which is suitable for ultra-thin smartphones. The design of eight-port antenna array was fabricated and measured. According to the test results, an ideal impedance matching (superior to 10 dB), preeminent isolation (superior to 17 dB) and excellent efficiency (superior to 61%) are obtained over the 3.5 GHz frequency band and 5 GHz frequency band. In order to evaluate MIMO performance, the ergodic channel capacities and envelope correlation coefficients (ECC) are also investigated.
DUAL-BAND MIMO ANTENNA ARRAY FOR COMPACT 5G SMARTPHONES
2020-02-04
PIER C
Vol. 99, 145-156, 2020
download: 257
Design of a Miniaturized Multilayer Tunable Super Wideband BPF
Aditi Sengupta Somdotta Roychoudhury Santanu Das
A miniaturized multilayer tunable super wideband (SWB) bandpass filter (BPF) is presented based on a microstrip structure. A pair of transmission line is coupled with the aid of three defected ground structures (DGS) at ground to improve the coupling and provide ultra wide band pass response. One of the transmission line is placed at the top plane of the upper layer, and the other transmission line is at bottom plane of the lower layer with defected microstrip structures (DMS) to improve the return loss. Bandwidth can be tuned by properly selecting the resonator size. Circuit model for the microstrip resonator and mathematical analysis are given and studied. Finally, the proposed vertical connection with slotline structures and a three pole UWB filter is designed, simulated, fabricated, and the results are well vindicated by an exemplary circuit centered at 6.5 GHz with the measured fractional bandwidth (FBW) of 135%. The filter exhibits a constant group delay of 0.3 ns in the pass band and the size of the resonator is 13.67 mm×17.58 mm×3.2 mm.
DESIGN OF A MINIATURIZED MULTILAYER TUNABLE SUPER WIDEBAND BPF
2020-02-03
PIER C
Vol. 99, 133-143, 2020
download: 263
Multi-Band mm -Wave Antenna for 5G-WiGig Communication Systems
Nada Abdelatif Hany Mahmoud Zamel Ahmed Attiya Amr Awamry
In this paper, we develop a multi-band circularly polarized planar antenna operating at 28 GHz and 60 GHz for 5G and WiGig applications. The antenna is composed of a square slot antenna fed by a proximity coupled microstrip line and loaded by grounded square loop and three tilted angle strips. Grounded square patch introduces resonance at 60 GHz frequency while the strips introduce resonances at 28 GHz. The square slot is designed as a wide-band antenna which can support these two resonances.
MULTI-BAND MM-WAVE ANTENNA FOR 5G-WIGIG COMMUNICATION SYSTEMS
2020-01-30
PIER C
Vol. 99, 123-132, 2020
download: 192
A Novel Patch Array Antenna with Wideband and Dual Sense Circular Polarization Characteristics for WiMAX & WLAN Applications
Yaqiang Zheng Min Gao Xiaohu Zhao
A wideband patch array antenna with dual sense circular polarization (CP) is investigated in this paper. Four rotated hexagonal patches are sequentially distributed on the upper surface of substrate 1 to form a patch array. In order to widen impedance bandwidth, an annular feeding network with four rectangular branches is designed. At the bottom of the antenna, two orthogonally placed microstrip baluns are introduced to obtain the characteristics of left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). Meanwhile, four coaxial probes, passing through substrate 2 and substrate 3, are used to transmit the feeding signal between microstrip balun and the annual feeding network. The proposed patch array antenna is fabricated for verifying the feature of wideband and dual circular polarizations. The measured results show that the antenna has an impedance bandwidths of 70.2% (1.72-3.58 GHz) with an axial ratio (AR) bandwidth of 61% (1.85-3.48 GHz) and over 6.2 dBi gain at two ports. Moreover, the measured port isolation remains below -15 dB over the entire impedance bandwidth, and the measured radiation patterns with excellent directionality and symmetry at two ports indicate that the proposed antenna can be used for wireless applications.
A NOVEL PATCH ARRAY ANTENNA WITH WIDEBAND AND DUAL SENSE CIRCULAR POLARIZATION CHARACTERISTICS FOR WIMAX & WLAN APPLICATIONS
2020-01-30
PIER C
Vol. 99, 111-122, 2020
download: 492
Truncated Circular Microstrip Ultra Wideband Antenna Exhibiting Wideband Circular Polarization
Kollannore Ukru Sam Parambil Abdulla
Circular polarization is manifested by means of truncations on basic circular radiating patch with precisely designed asymmetric feed. The proposed truncated circular microstrip antenna (TCMA) yields impedance bandwidth (IBW) of 7.6 GHz, almost covering the FCC approved ultra wideband (UWB) frequency and 3-dB axial ratio bandwidth (ARBW) of 5.05 GHz spreading over two bands, enabling the antenna to be used for multiple applications in ultra wideband frequency range. A peak gain of 5.73 dBi is documented at 5 GHz which is within the circular polarization (CP) band. This single feed antenna is very simple to design and compact in size.
TRUNCATED CIRCULAR MICROSTRIP ULTRA WIDEBAND ANTENNA EXHIBITING WIDEBAND CIRCULAR POLARIZATION
2020-01-30
PIER C
Vol. 99, 99-110, 2020
download: 348
Early Brain Stroke Detection Using Flexible Monopole Antenna
Md. Ashikur Rahman Md. Foisal Hossain Manjurul Ahsan Riheen Praveen Kumar Sekhar
In this paper, an inkjet printed slotted disc monopole antenna is designed, printed and analyzed at 2.45 GHz ISM band on a polyethylene terephthalate (PET) substrate for early detection of brain stroke. PET is used as a substrate due to its low loss tangent, flexible, and moisture-resistant properties. By the implementation of slotting method, the size of this antenna is reduced to 40×38 mm2. The printed antenna exhibits 480 MHz (19.55%) bandwidth ranging from 2.25 GHz to 2.73 GHz frequency. It shows a radiation efficiency of 99% with a realized gain of 2.78 dB at 2.45 GHz frequency. The Monostatic Radar (MR) approach is considered to detect brain stroke by analyzing the variations in reflected signals from the head model with and without stroke. The maximum specific absorption rate (SAR) distribution at 2.45 GHz frequency is calculated. The compact size and flexible properties make this monopole antenna suitable for early detection of brain stroke.
EARLY BRAIN STROKE DETECTION USING FLEXIBLE MONOPOLE ANTENNA
2020-01-29
PIER C
Vol. 99, 87-98, 2020
download: 221
Dual Polarized UWB MIMO Antenna with Elliptical Polarization for Access Point with Very High Isolation Using EBG and MSR
Gnanaharan Irene Anbazhagan Rajesh
A compact microstrip fed dual polarized Ultra Wide Band (UWB) monopole Multiple Input Multiple Output (MIMO) antenna for access point application in Wireless Body Area Networks (WBAN) is proposed. The antenna is elliptically polarized in the 6 to 10.6 GHz band. The proposed structure possesses high isolation with the introduction of Modified Serpentine Structure (MSS) that behaves as a decoupling unit (DU). To further reduce the coupling and to improve the impedance bandwidth, an Electromagnetic Band Gap (EBG) structure is introduced. The proposed antenna has a wide impedance bandwidth with S11 < -10 dB in the UWB from 3.1-10.6 GHz and has a high isolation S21 < -25 dB. The antenna has a fractional bandwidth of 106%. The radiation pattern of the antenna is omnidirectional. The Envelope Correlation Coefficient (ECC) is equal to zero, and the capacity loss is 0.264 which proves the diversity characteristics of the proposed antenna.
DUAL POLARIZED UWB MIMO ANTENNA WITH ELLIPTICAL POLARIZATION FOR ACCESS POINT WITH VERY HIGH ISOLATION USING EBG AND MSR
2020-01-26
PIER C
Vol. 99, 77-86, 2020
download: 255
Indium Tin Oxide Based Wideband Dielectric Resonator Antenna for Wireless Communication
Vivek Parimi Sajal Biring Ku Chia Hao Abhirup Datta Somaditya Sen
In this paper, a novel dielectric resonator antenna has been numerically simulated and experimentally demonstrated. The proposed design, comprising an Indium Tin Oxide (ITO) coated glass slide placed on a microstrip transmission line, is intended for WLAN and Wi-Max applications. The antenna shows a maximum bandwidth of 2.15-7.65 GHz and 10.36-11.78 GHz and a gain ranging from 2.21 to 6.44 dB. The novelty of the design lies in the use of ITO coating on glass to enhance as well as regulate the antenna bandwidth. Parametric variations have been investigated to analyse the topology for understanding the effect of the design parameters on gain, bandwidth, and reflection coefficient. A prototype has also been fabricated, where different ITO sheets have been mounted to measure the response. The proposed geometry has been found to be better and competent enough with respect to antenna parameters than existing Ultrawide Band antennas.
INDIUM TIN OXIDE BASED WIDEBAND DIELECTRIC RESONATOR ANTENNA FOR WIRELESS COMMUNICATION
2020-01-25
PIER C
Vol. 99, 61-75, 2020
download: 255
Synthesis of Chained-Elliptic Function Waveguide Bandpass Filter with High Rejection
Guan Shen Ng Sovuthy Cheab Peng Wen Wong Socheatra Soeung
This paper describes the synthesis of a bandpass filter to achieve high selectivity and rejection properties using a new class of filter functions called chained-elliptic function filters. Chained-elliptic filters have higher selectivity than Chebyshev function filters and have the property of sensitivity to manufacturing tolerance reduction in chained-function filters. The proposed design has high selectivity and reduced sensitivity, enabling easier and faster filter fabrication. The characteristic polynomials of chained-elliptic function filters are derived through chaining elliptic filtering function and extracted to form a coupling matrix of the bandpass filter. The novel transfer polynomials are given in detail, and a thorough investigation of the filter characteristics is performed. A theoretical comparison with Chebyshev and elliptic filters of the same order is performed to ascertain the demonstrated advantages of this proposed filter class. A high frequency narrow-band fourth-order chained-elliptic function waveguide filter centred at 28 GHz with a fractional bandwidth of 1.61% is fabricated to validate the proposed design concept. A good match among the measured, simulated and ideal filter responses is shown where the overall responses between measurement and simulation have a difference of approximately 2% which is within the acceptable limit. The chained-elliptic function concept will be useful in designing low-cost high-performance microwave filters with various fabrication technologies for millimetre-wave applications.
SYNTHESIS OF CHAINED-ELLIPTIC FUNCTION WAVEGUIDE BANDPASS FILTER WITH HIGH REJECTION
2020-01-24
PIER C
Vol. 99, 49-59, 2020
download: 302
Eight-Port MIMO Antenna System for 2.6 GHz LTE Cellular Communications
Naser Ojaroudi Parchin Haleh Jahanbakhsh Basherlou Yasir I. A. Al-Yasir Ahmed M. Abdulkhaleq Raed A. Abd-Alhameed Peter S. Excell
In this paper, an eight-port antenna array operating in the 2.6 GHz band (2550-2650 MHz) for a multi-input multi-output (MIMO) mobile terminal is presented. The design is composed of four pairs of compact dual-polarized slot antennas that are symmetrically placed at the corners of a mobile-phone mainboard. Each antenna pair consists of miniaturized petal-shaped slot resonators fed by two independent microstrip-feeding lines, thus facilitating radiation pattern and polarization diversity: when acting together, they facilitate multi-channel MIMO operation. The design offers good isolation, dual polarization and full radiation coverage in a smartphone sized package. A low-cost FR-4 dielectric (ε = 4.4, δ = 0.02, and h = 0.8 mm) with a dimension of 75×150 mm2 is used as the PCB substrate. The characteristics of the smartphone antenna are examined using both simulations and measurements.
EIGHT-PORT MIMO ANTENNA SYSTEM FOR 2.6 GHZ LTE CELLULAR COMMUNICATIONS
2020-01-23
PIER C
Vol. 99, 35-48, 2020
download: 276
Microstrip Defected Ground Structure for Determination of Blood Glucose Concentration
See Khee Yee Soon Chong Johnson Lim Pih Shyan Pong Samsul Haimi Dahlan
This work reports the application of a microwave sensor in measuring human blood glucose concentration. The main contribution of this work lies on the blood glucose profile which is collected from 69 random patients regardless of their gender, age, and haematology properties, instead of using water as the base or focusing on a single person. Hence the blood glucose profile is more realistic. Blood is extracted from the participants and dropped at the center of the dumbbells section of a microstrip defected ground structure to gather the notch frequency shifting data. On the other hand, the blood samples are measured using Omron Freestyle Glucometer to collect their associated blood glucose readings. Five predicting models have been proposed in this work. Based on the cross-validation, it is found that the blood glucose level can be correlated very well with shifted notch frequency by using a linear model. It introduces least root mean square error (RMSE) of 0.0592 and shows good correlation (R2 = 0.9356) between the reading from commercial glucometer and microwave sensor in the range up to 12 mmol/L. The reliability of this microwave sensor is proven once again when the predicted blood glucose data are all falling in Zone A of Clarke Error Grid. The outcome of this work shows the capability of this microwave sensor in measuring the blood glucose level. Since this microwave sensor can be reused under a proper cleaning procedure, it improves the sustainability of conventional blood glucose testing by reducing the disposal of testing strips and cost. It is believed that this sensor will be suitable for extensive blood glucose testing conducted in the laboratory.
MICROSTRIP DEFECTED GROUND STRUCTURE FOR DETERMINATION OF BLOOD GLUCOSE CONCENTRATION
2020-01-20
PIER C
Vol. 99, 15-33, 2020
download: 256
Microwave Diathermy for Deep Heating Therapy of Knee Joint
Asmaa Elsayed Farahat Heba Mohamed Kahil Khalid Fawzy Ahmed Hussein
This study proposes the idea of a thermotherapy device for the treatment of human knee joint disorders by the thermal effect of microwave radiation. The device is composed of a circular array of dipole antennas operating at 2.45 GHz. A high resolution three dimensional geometric, electric, and thermal model for a human right knee is constructed. Electromagnetic simulations are performed to calculate the specific absorption rate (SAR) distribution within the tissues of the human knee using the finite difference time domain (FDTD) method. The SAR distributions are calculated for four and eight elements circular arrays. The FDTD is applied to calculate the rise in temperature within different tissues of the human knee due to the exposure to different levels of heating microwave power. The effect of the tissue thermoregulatory response on the temperature rise is investigated for each individual tissue type. Moreover, the dependence of the induced steady state rises in tissue temperatures on the absorbed SAR is studied in the case of the SAR at a point in the muscle tissue (local SAR), and the SAR averaged over 1 g (SAR1 g) and over 10 g (SAR10 g). The rise in temperature distribution due to radiation from the circular array of dipoles is calculated at different cross sections.
MICROWAVE DIATHERMY FOR DEEP HEATING THERAPY OF KNEE JOINT
2020-01-17
PIER C
Vol. 99, 1-14, 2020
download: 149
Coherence Reduction of the Measurement Matrix in Microwave Computational Imaging by Introducing Polarization Diversity
Jian Guan Chang Chen Weidong Chen
For microwave computational imaging (MCI), the reduction of measurement matrix's coherences permits better reconstruction performance. Therefore, frequency diverse apertures (FDAs) have become a major option of antennas for MCI due to their frequency-varying radiation patterns. The frequency diversity in the patterns reduces coherences; however, the losses in practical materials and the finite sizes of apertures impose upper limits on frequency diversity. For further coherence reduction, the polarization diversity (PD) of aperture elements is as a new approach introduced in this paper. We present an electromagnetic formulation of scattering aperture elements' PD. In the formulation, the PD brings an additional degree of freedom in the generation of the measurement matrix, given the apertures being illuminated with varying polarizations. This new degree of freedom enables a potential of reducing the coherences. Two complementary electric-field-coupled (cELC) scattering apertures, which differentiate in the polarizations of elements, are fabricated for validation. A set of comparisons yielded by the near-field scanning data of these apertures shows that the PD effectively reduces coherences and improves reconstruction performance.
COHERENCE REDUCTION OF THE MEASUREMENT MATRIX IN MICROWAVE COMPUTATIONAL IMAGING BY INTRODUCING POLARIZATION DIVERSITY