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2021-07-09 PIER C Vol. 113, 265-275, 2021. doi:10.2528/PIERC21052703

Metasurface Incorporated Frequency Reconfigurable Planar Antenna for Wireless Applications

Navneet Kaur, Jagtar Singh Sivia, and Rajni

In this paper, the design of a Metasurface incorporated Frequency Reconfigurable Planar Antenna (MS-FRPA) for Wireless Applications is presented. The structure of projected MS-FRPA consists of a patch with a metasurface placed one above the other with no gap between them. The MS is composed of an array of alternately placed dual split ring resonators arranged periodically in both horizontal and vertical directions. Frequency reconfiguration is achieved by rotating the MS relative to the designed patch antenna. The projected reconfigurable antenna is constructed on Rogers RO4350B material with thickness 1.524 mm. High Frequency Structure Simulator software is employed for analysis of the structure. The results clearly reveal that frequency tuning is achieved in 4.35 to 5.33 GHz with a fractional tuning range of 20.2%. The proposed structure provides appreciable realized gain with stable radiation patterns at all rotation angles. Further, the measured outcomes of the developed prototype show good correlation with the simulated outcomes.

2021-07-07 PIER C Vol. 113, 251-263, 2021. doi:10.2528/PIERC21052007

Dual-Band Complementary Split-Ring Resonator Engraved Rectangular Monopole for GSM and WLAN/WiMAX /5G Sub-6 GHz Band (New Radio Band)

Samuel Prasad Jones Christydass and Nagarajan Gunavathi

In this paper, a rectangular monopole antenna engraved with a complementary split-ring resonator is proposed for dual-band operation. The proposed antenna is fabricated on an FR4 substrate with a dimension of 20 x 34 x 1.6 mm3. The entire simulation is done using CST EM studio software. The proposed antenna exhibits dual-band operation from 1.78 GHz to 1.90 GHz and from 3.45 GHz to 6.58 GHz. The band from 1.78 GHz to 1.90 GHz is due to the inclusion of CSRR, and its corresponding bandwidth is 120 MHz. It is validated with the quasi-static analysis. The permittivity characteristics of the proposed CSRR are retrieved using the NRW method and presented. The resonant frequency of the band created by the CSRR is 1.83 GHz with -37.68 dB as its return loss values. The second wider band is due to the combination of the mode created by the CSRR along with the radiating patch from 3.45 GHz to 6.58 GHz with 3132 MHz which has a dual resonance at 3.65 GHz and 5.59 GHz with a return loss of -30.23 dB and -29.80 dB. The optimal values are chosen with the help of parametric analysis. The designed antenna is fabricated and measured. The measured results of return loss, gain, E-plane, and H-plane are compared with simulated results, and they are complying with each other. The dual-band operation, compact size, stable radiation pattern along with gain above 2.3 dBi in the whole resonating band make it suitable for the GSM and WLAN/WiMAX/5G Sub-6 GHz band (new radio band).

2021-07-03 PIER C Vol. 113, 239-249, 2021. doi:10.2528/PIERC21050901

Axial Ratio Tuned Circularly Polarized Slot-Loaded Antenna for S-Band and C-Band Applications

Ramya Radhakrishnan and Shilpi Gupta

This paper introduces a dual-band circularly polarized antenna modeled on an FR4 substrate with an optimized dimension of 48 mm × 29.5 mm × 1.6 mm. A maximum usable circularly polarized bandwidth of 90% is obtained in the lower band (3.08 GHz to 3.75 GHz). A square slot etched in the ground plane loaded with asymmetric plus-shaped slits and tabs aids the impedance bandwidth enhancement. The dual-band operation is accomplished by facilitating parasitic square patches in the slot. The simulated impedance bandwidth of the proposed antenna is 740 MHz (3.07 GHz to 3.81 GHz) for the lower band and 1.57 GHz (4.64 GHz to 6.21 GHz) in the upper band. The impedance and axial ratio bandwidth percentages for lower and upper-frequency bands are 21.5%, 19.6%, and 29.4%, 10.54%, centered at 3.5 GHz and 5.5 GHz, respectively. The simulated and measured results are in reasonably good agreement.

2021-07-01 PIER C Vol. 113, 227-238, 2021. doi:10.2528/PIERC21040904

K -Band Ka-Band Planar Spiral Antenna Arrays with Integrated Corporated Feeding Network

Paul Tcheg and David Pouhè

Although spiral antennas have undergone continuous development and refinement since Edwin Turner conceived them in 1954, only a few compact planar arrays exist. The shortcoming is even more significant when it comes to spiral antenna arrays in mode M2 operation. The present work addresses this issue, among other things. It presents two planar arrays of spiral antennas operating in the same frequency band and radiating for the first one an axial mode M1 and a conical mode M2 for the second. Both arrays are modeled, simulated, and fed with a corporate feeding network embedded in a dielectric substrate. It is shown that keeping the same topology, the array for conical M1 mode can be obtained from the array for mode M2 by a simple introduction of a phase shift on one branch of the feed and vice versa, providing thus the possibility to obtain in the same structure a spiral antenna array operating in both modes in the same frequency band simultaneously. Comparison between simulated and measured data shows good agreement.

2021-06-30 PIER C Vol. 113, 211-226, 2021. doi:10.2528/PIERC21051702

A Compact Low SAR and High Gain Circularly Polarized AMC Integrated Monopole Antenna for WBAN Applications

Nibash Kumar Sahu and Sanjeev Kumar Mishra

This paper presents a compact CPW fed circularly polarized AMC integrated monopole antenna with low SAR and high gain for 2.4 GHz WBAN applications. The proposed design is achieved through a four-stage progression. Stage-1 consists of a straight monopole with an extended vertical stub at one of the ground planes to generate circular polarization. In stage-2, a novel ring-type isotropic AMC is implemented beneath the monopole antenna to mitigate the antenna's back radiations towards the human body. On the body at `0' mm distance, it reduces the SAR by 99.47% and increases the impedance bandwidth, radiation efficiency, and gain to 480 MHz, 77% and 7.1 dBi, respectively. However, there is a decrease in AR bandwidth that indicates AR > 3-dB, which is compensated in stage-3 by optimizing the monopole. The optimization results an AR BW of 190 MHz and a size reduction of monopole antenna by 30.862%. Due to the size reduction of monopole with same AMC, the SAR reduction and peak gain are improved to 99.63% and 7.4 dBi, respectively. In Stage-4, the 3×3AMC is replaced by 2×2 AMC, results in total size and SAR reduction of 55.56% and 97.72% respectively. Stage-4 provides a simulated impedance bandwidth of 350 MHz, peak gain of 6.4 dBi and AR bandwidth of 170MHz, whereas the fabricated structure on felt substrate provides 650 MHz, 6.5 dBi and 150 MHz respectively.

2021-06-25 PIER C Vol. 113, 197-209, 2021. doi:10.2528/PIERC21050202

Design of Triple Band-Notched UWB MIMO/Diversity Antenna Using Triple Bandgap EBG Structure

Priyanka Dalal and Sanjeev Kumar Dhull

This paper presents the design of a compact triple band-notched ultra-wideband (UWB) two element multiple-input multiple-output (MIMO) antenna. For validation of the simulation results, the prototype of the design is fabricated and experimentally measured. From the experimental results, it is observed that the proposed design, operating in the frequency range 2.5-12 GHz, successfully rejects three interfering bands i.e. the WiMAX band, WLAN band, and satellite communication X-band, when a triple bandgap CSRR-loaded EBG structure is embedded close to the feedline of the UWB antenna. In the ground plane of MIMO antenna, a rectangular slot and a mirrored pair of F-shaped stubs are added to minimize the mutual coupling between the UWB elements. The proposed MIMO antenna has good wideband isolation between the elements (> 20 dB), high diversity gain (10 dB), and low envelope correlation coefficient (< 0.02) over the entire UWB.

2021-06-24 PIER C Vol. 113, 177-195, 2021. doi:10.2528/PIERC21040906

Evaluating Performance of Heating, Ventilation & Air Conditioning Duct Communication Channel at 60 GHz Using Ray Tracing

Esha Bangar and Kamran Kiasaleh

In this paper, we developed a 3-dimensional (3D) ray-tracing simulator using MATLAB for establishing the viability of heating, ventilation, and air conditioning (HVAC) ducts as a reliable communication channel for indoor communication at millimeter-wave (mm-wave) frequencies. We present theoretical analysis of image theory ray-tracing and provide the equations for total electric field due to different rays undergoing reflections at the duct walls. We also computed the received signal strength indicator (RSSI) for the dry and moisture-laden air flowing through the HVAC ducts. The ray-tracing results are compared with the experimental and theoretical results we obtained for the HVAC ducts. With transmitter effective isotropic radiated power (EIRP) of 7 dBm, we obtain RSSI which varies between -34 dBm and -53 dBm for dry atmospheric pressure and temperature of 1013.25 hPa and 294.26 K, respectively, and duct lengths of up to 8 m at 60 GHz.

2021-06-23 PIER C Vol. 113, 161-175, 2021. doi:10.2528/PIERC21040202

Novel Design and Characterization of Wide Band Hook Shaped Aperture Coupled Circularly Polarized Antenna for 5G Application

Ravikanti Swetha and Mallavarapu Sandhya

This research paper presents a wideband hook shaped aperture coupled circularly polarized antenna for 5G application. It consists of three layers; a radiating copper plate (0.5 mm) as a top layer, a foam material of 2 mm thickness as a middle layer, an FR4 substrate with hook-shaped apertures in the ground plane, and a bent feed line as the bottom layer. The performance characteristics of the proposed design are improved by feeding mechanism, which entails the use of a bent shape microstrip line coupling through four hook shaped slots to generate four sequentially phased sources to excite the single layer patch antenna. The proposed antenna exhibits return loss bandwidth of 29.10% (2.8-3.81 GHz), axial ratio bandwidth of 13.47% (3.61-4.11 GHz), and cross polarization level is 20 dB which is attained at boresight and Gain of 4.08 dBic at the resonant frequency of 3.47 GHz. The proposed antenna design is fairly applicable to 5G radio band and discussed about the azimuth, elevation patterns and surface current distribution in frequency band of interest. The proposed design is simulated using High frequency structure simulator (v.13), and measured results are in good agreement with simulated ones.

2021-06-16 PIER C Vol. 113, 147-160, 2021. doi:10.2528/PIERC21042502

Multi-Objective Optimal Design and Analysis of Variable Leakage Flux IPM Motors for Improve Flux-Weakening Ability

Xiping Liu, Gaosheng Guo, Longxin Du, and Wenjian Zhu

In this paper, two variable leakage flux permanent magnet (VLFPM) machines are proposed. The keys are to adopt the rotor with single-layer and double-layer PMs and intentionally create leakage flux paths to extend the operating speed range and increase the machine efficiency. The characteristics of the variable leakage flux of the proposed machines are investigated. In order to improve the performances of the VLFPM machines, the Multi-Objective Genetic Algorithm (MOGA) method is applied for achieving the multi-objective optimizations of variables. Then, the performances of the double-layer permanent magnet variable leakage flux motor (DLPM-VLFM) and the single-layer permanent magnet variable leakage flux motor (SLPM-VLFM) are analyzed and compared with conventional interior PM machine (CIPMM) in detail. The performances mainly include flux linkage and torque, flux-weakening capability and efficiency. Finally, it is shown by analysis and comparison that the DLPM-VLFM can have a wider range of speed and high efficiency.

2021-06-16 PIER C Vol. 113, 137-146, 2021. doi:10.2528/PIERC21041202

Human Multicomponent Micro-Doppler Signals Separation Based on a Novel Local Time-Frequency Sparse Reconstruction Method

Zhongfei Ni and Bin-Ke Huang

The use of radar micro-Doppler (m-D) signatures for human activities classification, surveillance and healthcare has become a hot topic in recent years. While m-D signals are always multicomponent, it is necessary to separate them into mono-components signals associated with individual body parts for easier features analysis and extraction. In this paper, a novel method called local time-frequency sparse reconstruction (LTFSR) is proposed to iteratively extract and separate m-D components one by one in a descending intensity order from a time-frequency (T-F) representation. For the current strongest m-D component, we first estimate its instantaneous frequency (IF) by dividing the signal into short overlapping time intervals and selecting the best matching chirp atom to approximate the local frequency in each time interval based on matching pursuit. Then, a T-F filtering is used to extract and remove the strongest component from the multicomponent signal. Repeat the above steps until all m-D components are separated. Simulations are given to validate the effectiveness and robustness of the proposed method.

2021-06-16 PIER C Vol. 113, 123-136, 2021. doi:10.2528/PIERC21042703

Design of Compact 4-Port MIMO Antenna Based on Minkowski Fractal Shape DGS for 5G Applications

Sara Yehia Abdel Fatah, Ehab K. I. Hamad, Wael Swelam, Abdemegeed Mahmoud Allam, and Hesham Abd Elhady Mohamed

A 4-port wideband Multiple-Input Multiple-Output (MIMO) antenna operating in the frequency band from 24.8 GHz to 27.6 GHz dedicated to 5G application is proposed in this manuscript. The MIMO antenna is implemented on a 23.75 × 42.5 × 0.508 mm3 Roger/Druoid 5880 substrate with relative dielectric constant εr = 2.2 and loss tangent 0.0009. Firstly, the design starts with a simulation and optimization of a single element antenna based on Minkowski fractal shape as Defected Ground Structures (DGSs) using CST Studio Suite. The single proposed element shows a 7 dBi gain and antenna efficiency of 85% at the operating frequency band. Secondly, to design a MIMO antenna with good isolation, three different configurations are used, and overall MIMO performances such as low Envelope Correlation Coefficient (ECC), high Diversity gain (DG), and low Channel Capacity Loss (CCL) are calculated and analyzed. Finally, fabrication and measurement are conducted to validate the concept for single and 2-port MIMO antenna performance.

2021-06-14 PIER C Vol. 113, 111-122, 2021. doi:10.2528/PIERC21050305

Eight-Port Double Band Printed MIMO Antenna Investigated for Mutual-Coupling and SAR Effects for Sub-6 GHz 5G Mobile Applications

Insha Ishteyaq, Issmat Shah Masoodi, and Khalid Muzaffar

An 8-element/8-port antenna with four resonating dual-polarized slot radiator elements for sub-6 GHz 5G multiple-input multiple-output (MIMO) applications is proposed in this paper. The proposed MIMO design comprises four annular slot radiators with dual-polarized characteristic and has rectangular micro-strip line feeds. The designed elements operate in the frequency bands 2.73-3.12 GHz and 4.33-4.68 GHz providing an acceptable characteristic for dual-polarizations. The isolation improvement and reduction in mutual coupling factor are achieved by using split ring resonator (SRR) structures on the top layer along the slot radiator. The proposed design has a -10dB wide impedance bandwidth in both bands, considerable realized peak gain around 4 dBi, and better efficiencies around 80\% with ECC < 0.004 which has enhanced the performance of the MIMO array in terms of diversity. The antenna is fabricated, characterized, and it is shown that the measured results are in good agreement with the simulated ones. The proposed MIMO design has been analyzed for SAR functions and the radiation coverage in the vicinity of the user human head. The SAR values studied are found to be less than `2' which is quite desirable. All the features achieved in the proposed MIMO design suggest it to be suitable for 5G mobile terminal applications.

2021-06-11 PIER C Vol. 113, 97-110, 2021. doi:10.2528/PIERC21041102

Octa-Band Metamaterial Inspired Multiband Monopole Antenna for Wireless Application

Samuel Prasad Jones Christydass and Nagarajan Gunavathi

In this paper, a Rectangular Monopole Antenna (RMPA) with offset microstrip feed is presented. The structure is fabricated on an FR4 substrate with a dimension of 28 x 32 x 1.6 mm3. The proposed structure achieves multiband operation by engraving 2 Complementary Split Ring Resonators (CSRRs) and a C-Shaped slot. Also, 2 Split Ring Resonators (SRRs) are printed on the adjacent sides of the radiating element. The parametric analysis is used to determine the optimum position of the feed and other critical parameters. The proposed structure operates at 2.25 GHz, 3.86 GHz, 4.60 GHz, 5.64 GHz, 5.86 GHz, 6.94 GHz,7.48 GHz, and 9.47 GHz. The permeability of the SRR and permittivity of the CSRR are extracted and presented. The proposed antenna is fabricated and measured. The measured results of S11, radiation pattern, and gain are on par with the simulated results. The proposed antenna's simulated surface current and efficiency are also presented to validate the performance. Simple structure, stable radiation patten, multiband operation, reasonable gain, and efficiency are the significant features of the proposed RMPA.

2021-06-10 PIER C Vol. 113, 83-96, 2021. doi:10.2528/PIERC21032507

A Dual Bandpass Filter Design Using Strong Coupling, Evanescent Mode and Modular Concept

Sek-Meng Sow, Peng Tan, and Jian Lu

This paper presents a new design concept of dual bandpass filter. Based on the strong coupling between two resonators, a dual 1-pole band-pass filter is designed and is used as the basic building block. By providing appropriate weak coupling between these building blocks, a higher-order dual bandpass filter can be realized. In addition, these building blocks can be stacked vertically and/or horizontally to construct a compact filter. In this way, by using 3D full wave EM and circuit co-simulation, the simulation time required in the design stage can be reduced. In addition, it also provides a way to post-tune each building block individually and further reduces the time required in prototype post tuning process. For demonstration, an L-band dual 4-pole bandpass filter is designed with passband frequencies of 1.23 GHz~1.255 GHz and 1.55 GHz~1.6 GHz. In order to reduce the size of the filter and obtain a wide stopband bandwidth, a suitable evanescent mode cavity is used to realize the resonant structure. The measurement result shows that the insertion losses of the low passband and high passband are 1.03 dB~2.00 dB and 1.02 dB~1.75 dB, respectively; the return loss of both passbands is better than 15 dB. Furthermore, up to 5 GHz (> 3fo, where fo is at 1.39 GHz), the stopband rejection level is better than 80 dB.

2021-06-10 PIER C Vol. 113, 69-82, 2021. doi:10.2528/PIERC21042701

A Compact Four-Port High Isolation Hook Shaped ACS Fed MIMO Antenna for Dual Frequency Band Applications

Praveen Naidu, Dhanekula Maheshbabu, Akkapanthula Saiharanadh, Arvind Kumar, Neelima Dudi, Lam Sumanji, and Khalim Amjad Meerja

In this work, a novel 4 element Multi-Input Multi-Output (MIMO) antenna is reported. The proposed antenna has a size of 50x50x1.6 mm3 is printed on the FR-4 substrate having dielectric constant εr = 4.4 and loss tangent (tan δ = 0.02). The four antenna elements are positioned in each corner of the PCB board in an orthogonal manner such that they can provide better isolation between antenna elements. The proposed MIMO antenna is designed to operate in frequency bands of 2.25 GHz to 2.4 GHz and 4.7 GHz to 6.3 GHz. The lower band ranges from 2.25 GHz to 2.4 GHz and covers 2.3 GHz WiBro applications while the upper band ranging from 4.7 GHz to 6.3 GHz is useful for Hiper LAN and Wi-MAX applications. The proposed antenna acquires return loss less than -10 dB and isolated by more than 16 dB throughout the dual operating bands. The structure exhibits stable gain and radiation patterns. Various diversity performance metrics including envelope correlation coefficient (ECC), diversity gain (DG), and mean effective gain (MEG) are evaluated and are within acceptable limits.

2021-06-10 PIER C Vol. 113, 59-68, 2021. doi:10.2528/PIERC21041001

A Compact Dual Asymmetric L-Slot Frequency Reconfigurable Microstrip Patch Antenna

Bhaben Saikia, Pulin Dutta, and Kunal Borah

A frequency reconfigurable microstrip patch antenna with two asymmetric L-slots is proposed in this article. Two RF pin diodes inserted on the asymmetric L-slots are used to switch the operating frequency over the C band. Design and optimization of different physical parameters of the antenna viz. slot dimensions, feed location, notch size and pin diode positions are carried out using High Frequency Structure Simulator Version 13.0. The design is implemented on an FR4 substrate (εr = 4.4) of dimension (35×40×1.6) mm3. DC bias circuitry for RF PIN diode activation is also integrated with the antenna. Switching combinations of two PIN diodes offer four reconfiguration modes of operation at 4.75, 5.05, 5.11 and 5.18 GHz. In all the states, the -10 dB bandwidth shows minimal changes with average variations of 15.8% with respect to the state when both PIN diodes are OFF. The gains of the antenna for different modes of operation are found almost stable with an average of 6.64 dBi.

2021-06-01 PIER C Vol. 113, 47-58, 2021. doi:10.2528/PIERC21042303

Radiation of Electromagnetic Waves by an Arbitrarily Oriented Slot at the End Wall of a Rectangular Waveguide

Mikhail Nesterenko, Viktor A. Katrich, Victor I. Kijko, and Svetlana V. Pshenichnaya

A problem of electromagnetic waves radiation diffracted at a narrow rectilinear arbitrarily oriented slot cut in an end wall of a semi-infinite rectangular waveguide is solved by an asymptotic averaging method. The slot radiates into a half-space over an infinite perfectly conducting plane. An influence of slot inclination angle upon energy and spatial characteristics is numerically studied. Theoretical results are compared with experimental data. A numerical-analytical problem of a narrow rectilinear slot radiating into the space above an infinite impedance plane is also presented. The asymptotic solution for the slot magnetic current was obtained by a generalized method of induced magnetomotive forces (MMF) by using Green's functions of a space above the impedance plane. The effect of the plane with impedance coating on the slot is reduced taking into account an additional term to the slot external conductivity, for which the expressions were obtained in an analytical form.

2021-05-31 PIER C Vol. 113, 29-46, 2021. doi:10.2528/PIERC21033002

Investigating the Equivalent Source and the Plane Wave Spectrum Methods in Predicting the Magnetic Field Behavior in the Vicinity of Microstrip Patch Antenna for Bluetooth and Wi-Fi Applications

Mohamed Amine Benchana, Abdesselam Babouri, Zouheir Riah, Abderrezak Khalfallaoui, Abdelaziz Ladjimi, and Jamel Nebhen

Over the past few years, the continuous evolution of embedded electronic systems has increased electromagnetic interferences problems. It has also generated a new design constraint on electromagnetic compatibility. Hence, predicting the electromagnetic field behavior in the vicinity of the electronic components and systems becomes a priority to avoid the potential for unwanted coupling occurrence, as well as to ensure the electromagnetic compatibility compliance for those components and systems which are embedded in a confined space. As a result, the designers of electronics' equipment are extremely interested in radiated emission models. This paper reports a comparative study in which two different methods will be applied: the equivalent source method and plane wave spectrum method. These two methods will be used to predict the magnetic field behavior in the vicinity of a microstrip patch antenna. The latter works in ISM band for Wi-Fi and Bluetooth applications. The two applied models are constructed from the tangential magnetic fields cartographies of the antenna obtained from HFSS® at 3.5 mm and validated by comparing the HFSS® results with those of the models at a higher elevation. Furthermore, the relative error between the simulated field of the antenna and those of the equivalent source model according to the dipoles number is presented to determine the minimum number of dipoles that allow users to obtain the results with better accuracy. Subsequently, the relative error as function of different elevations along the z axis together with the two methods comparison results is presented.

2021-05-18 PIER C Vol. 113, 13-27, 2021. doi:10.2528/PIERC21031402

Design, Optimization, and Analyses of Nano-Optical Couplers Consisting of Nanocubes to Construct Efficient Nanowire Transmission Systems

Aşkın Altınoklu and Özgür Ergül

We present the design, optimization, and analyses of efficient couplers to construct nano-optical transmission systems involving nanowires. The couplers consist of optimized arrangements of nanocubes and are integrated into critical locations, such as nanowire inputs, corners, and junctions, to improve electromagnetic transmission in accordance with design purposes. Optimization and numerical analyses are performed by employing an efficient simulation environment based on a full-wave solver and genetic algorithms. Using the designed couplers, we obtain various configurations that enable efficient transmission and distribution of input powers to multiple outputs. With their favorable properties, the designed couplers and constructed systems can be further used to build larger nanowire networks.

2021-05-18 PIER C Vol. 113, 1-11, 2021. doi:10.2528/PIERC21032704

A Compact Broadband Circularly-Polarized Patch Antenna with Wide Axial-Ratio Beamwidth for Universal UHF RFID Applications

Zhongbao Wang, Ya-Nan Wang, Xinhong Liu, Hongmei Liu, and Shao-Jun Fang

A compact broadband circularly-polarized (CP) patch antenna with a wide 3-dB axial-ratio (AR) beamwidth is proposed for universal ultra-high-frequency (UHF) radio frequency identification (RFID) applications. The proposed antenna consists of four triangular radiation patches and a compact feed network. Each of the radiation patches is grounded by shorting pins for 3-dB AR beamwidth enhancement and patch miniaturization. The feed network having a miniaturized hybrid coupler and two trans-directional couplers is proposed for good circular polarization. Measured results show that the -10-dB impedance bandwidth of the antenna is 18.4% (820-986 MHz); the 2.5-dB AR bandwidth is 32.8% (700-975 MHz); and the gain is 5.12 dBic. The measured 3-dB AR beamwidths for the planes of phi = 0° and phi = 45° are 177° and 190°, respectively. The overall antenna size is 0.408λ0 × 0.408λ0 × 0.053λ0 at 900 MHz.