Modulated Antenna Array Research Articles

Reinforcement learning-based adaptive beam alignment in a photodiode-integrated array antenna module.

We successfully demonstrated an intelligent adaptive beam alignment scheme using a reinforcement learning (RL) algorithm integrated with an 8 × 8 photonic array antenna operating in the 40 GHz millimeter wave (MMW) band. In our proposed scheme, the three key elements of RL: state, action, and reward, are represented as the phase values in the photonic array antenna, phase changes with specified steps, and an obtained error vector magnitude (EVM) value, respectively. Furthermore, thanks to the Q-table, the RL agent can effectively choose the most suitable action based on its prior experiences. As a result, the proposed scheme autonomously achieves the best EVM performance by determining the optimal phase. In this Letter, we verify the capability of the proposed scheme in single- and multiple-user scenarios and experimentally demonstrate the performance of beam alignment to the user's location optimized by the RL algorithm. The achieved results always meet the signal quality requirement specified by the 3rd Generation Partnership Project (3GPP) criterion for 64-QAM orthogonal frequency division multiplexing (OFDM).

MmWave Flat Panel Phased Array Antenna Module With Enhanced Scanning Coverage

mmWave Flat Panel Phased Array Antenna Module With Enhanced Scanning Coverage

A 2-D Beam Scanning Array Antenna Fed by a Compact 16-Way 2-D Beamforming Network in Broadside Coupled Stripline

A 2-D beam scanning array antenna fed by a compact 16-way 2-D beamforming network (BFN) designed in Broadside Coupled Stripline (BCS) is addressed. The proposed 16-way 2-D BFN is formed by interconnecting two groups of 4x4 Butler Matrix (BM). Each group is composed of four compact 4x4 BMs. The critical point of the design is to propose a simple and compact 4x4 BM without crossover in BCS to achieve a better transmission coefficient of the 16-way 2-D BFN with reduced size of merely 0.8λ0 × 0.8λ0 × 0.04λ0. Moreover, the complexity of the interface connection between the 2-D BFN and the 4x4 patch array antenna is reduced by using probe feeding. The 16-way 2-D BFN is able to produce the phase shift of ±45°, and ±135° in x- and y- directions. The 2-D BFN is easily integrated under the 4x4 patch array to form a 2-D phased array capable of switching 16 beams in both elevation and azimuth directions. The area of the proposed 2-D beam scanning array antenna module has been significantly reduced to 2λ0 × 2λ0 × 0.04λ0. A prototype operating in the frequency range of 4-6GHz is fabricated and measured to validate the concept. The measurement results agree well with the simulations.

Open-access millimeter-wave software-defined radios in the PAWR COSMOS testbed: Design, deployment, and experimentation

While millimeter-wave (mmWave) wireless has recently gained tremendous attention with the transition to 5G, developing a broadly accessible experimental infrastructure will largely facilitate the research and allow the community to make significant progress in this area. In this paper, we present the design and implementation of various programmable and open-access mmWave software-defined radios (SDRs) that have been deployed in the PAWR COSMOS advanced wireless testbed, in both indoor and outdoor environments. These programmable mmWave radios are based on the IBM 28GHz 64-element dual-polarized phased array antenna module (PAAM) subsystem board and the Sivers IMA 60GHz WiGig transceiver. These front ends are integrated with USRP SDRs or Xilinx RFSoC boards, which provide baseband signal processing capabilities. Moreover, we present measurements of the TX/RX beamforming performance and example experiments (e.g., real-time channel sounding and RFNoC-based 802.11ad preamble detection), using the mmWave radios. Finally, we discuss ongoing enhancement and development efforts focusing on these radios.

Design and Fabrication of Wideband Array Antenna Module for Two-Dimensional Interferometer Direction-Finding System

Design and Fabrication of Wideband Array Antenna Module for Two-Dimensional Interferometer Direction-Finding System

Power pattern synthesis of a moving phase center time modulated antenna array using symmetrically and asymmetrically positioned time schemes

The advantages of exploiting the harmonic patterns in a time-modulated linear array (TMLA) is presented in this paper through mathematical validation and also applied for real-world applications like beam scanning. The inherently generated harmonics or sideband radiations (SRs) in TMLAs are normally considered as a loss of power in unwanted direction. The effect of SRs at the multiple harmonic frequencies is mathematically modeled and presented in this paper. Time sequences with symmetrically and asymmetrically oriented pulses are studied (ON-time duration of array element is generally termed as ‘pulse’). The symmetrically oriented non-shifted switching scheme is equivalent to a simple ON–OFF switching, where all the switches connected with array elements are turned ON at the same time. On the other hand, an asymmetrically oriented shifted switching scheme has different switch-ON instants for different elements of an array. Closed-form expressions of radiated power in the main beam and sideband patterns are derived for both cases. The comparison of the shifted and non-shifted pulse is mathematically derived, and the advantages of shifted pulse for exploiting the sidebands are well established. To further discuss the advantages and limitations of these time schemes, phase-centered motion based TMLAs are investigated for electronic beam scanning, and the radiated power by fundamental and sideband patterns are calculated using closed-form equations.

Phase Shift Impact on the Performance of Time Modulated Antenna Arrays Driven by Radio Over Fiber

The joint exploitation of Radio over Fiber (RoF) and Time Modulated Arrays (TMA) is proposed, showing how, particularly within In-Building scenarios, it allows to combine the pervasiveness of the first technique with the beam-steering capability of the second. A cost-effective 3-element RoF-TMA system is presented and investigated, to realize a solution for small offices / private houses (SoHo's). It is confirmed that bringing the feed to the antennas through the RoF system keeps the possibility for the TMA to radiate power at different frequencies, in each case with a steerable maximum direction. Referring to mobile signals with RF carriers of few GHz, it is shown that to guarantee, for each of the multiple beams emitted by the TMA, a maximum deviation of 5° from its ideal direction, it is sufficient that among the output branches of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1:3{\boldsymbol{\ }}$</tex-math></inline-formula> optical splitter utilized the length difference is maintained in the range of a few millimeters.

An optimal time modulated compact circular antenna array design using a stochastic optimization technique

ABSTRACT This paper presents a time modulated far-field radiation pattern synthesis of a compact circular antenna array (CAA) by employing a stochastic optimization technique known as grey wolf optimization (GWO). The compactness of the antenna array is achieved by reducing the inter-element distances between the elements of the array which leads to the miniaturization of the antenna array size. On the other hand, an optimal far-field radiation characteristic is achieved by suppressing the side lobe level (SLL) as well as by narrowing the first null beamwidth (FNBW). A lower SLL value is necessary to avoid the interference with the system working in the same frequency, whereas, a narrow FNBW helps the antenna array to attain a high directivity. The performance of a time modulated antenna array (TMAA) depends on the rise on–off time, pulse shape as well as on the switching time duration of each element of the array which radiates at different harmonic frequencies. In this paper, the generation of radiation pattern at the fundamental/central frequency and its first two harmonic frequencies are considered for the design issue.

Efficient Shaped Pattern Synthesis for Time Modulated Antenna Arrays Including Mutual Coupling by Differential Evolution Integrated With FFT via Least-Square Active Element Pattern Expansion

The fast Fourier transform (FFT) via the least-square active element pattern expansion (LSAEPE) is generalized to speed up the computation of array patterns including mutual coupling and platform effect for time-modulated antenna arrays (TMAAs) at the central and sideband frequencies. By integrating the LSAEPE-FFT with differential evolution algorithm (DEA), the resulting DEA-LSAEPE-FFT method can realize efficient shaped pattern synthesis with accurate control of main lobe shape, sidelobe level (SLL) and sideband level (SBL). Two examples of synthesizing different shaped patterns for different TMAAs mounted on a nonuniform platform or with metal scatters are conducted to validate the effectiveness and robustness of the proposed method. Synthesis results show that the proposed method has much better accuracy performance than the conventional DEA-FFT while costing much less CPU time than that of using DEA combined with a direct summation.

Development of the algorithm of reliability­centered maintenance of phased array antennas

The strategy and algorithm of reliability-centered maintenance of active phased array antennas are developed. The use of this strategy and algorithm makes it possible to determine the time and volumes of corrective replacements of the antenna subarray modules based on the results of predicting the reliability indexes of the array antenna as a whole. This procedure is performed as a result of consistent refinement of statistical estimates of reliability indexes of the modules during the normal operation of the phased array antenna. For processing statistical information on the failures of the array antenna modules and determining the estimates of the sample mean, upper and lower confidence limits, the method of quantiles is used. As the law of distribution of the operating time of the array antenna modules, the combination of exponential and diffusion nonmonotonic distributions is used. The example of implementation of the reliability-centered maintenance strategy and algorithm for the receive phased array antenna including 100 antenna subarrays is presented. The results of the research can allow organizing the APAR condition-based maintenance and minimizing the operating costs. Implementation of the obtained results can ensure failure-free operation of active phased array radars during operation with the timely provision of antenna subarrays with spare modules.

A Time Modulated Printed Dipole Antenna Array for Beam Steering Application

This paper presents time modulated beam steered antenna array without phase shifters. The beam steering is analyzed considering a two-element time modulated antenna array (TMAA) of printed dipoles with microstrip via-hole balun. The proposed array resonates at the Industrial, Scientific, and Medical (ISM) radio bands, 2.45 GHz and 5.8 GHz, and offers wide bandwidth inherited due to modified structure of ground plane. Array elements are excited by complex exponential excitation signal through broadband power divider and radio frequency (RF) switches to achieve amplitude and phase variation without phase shifters. Differential Evolution algorithm is used to modify the time sequences of the RF switches connected to the antennas to generate radiation pattern with optimum dynamic efficiency by suppressing sideband radiations. Also switch-on time instant of RF switch connected to the subsequent element is modulated to steer the beam towards different directions. The proposed prototype is fabricated followed by parametric optimization. The fabrication results agree significantly well with simulated results.

항공기 날개 탑재 안테나의 빔 보상을 위한 X-대역 위상 배열 안테나 모듈

비행 중 날개 변형에 의해 바뀐 빔 방향을 보상하기 위한 X대역 위상 배열 안테나 모듈을 설계 및 제작하였다. 위상 배열 안테나 모듈은 배열 안테나, 전력분배기, 위상변위기 및 제어회로로 구성된다. 최적의 부품 선택을 위해 날개 변형 및 위상변위기의 위상 오차에 의한 방사 패턴의 변화를 시뮬레이션하였다. 제작된 위상 배열 안테나 모듈은 9.375 GHz에서 5.84 dBi의 이득, 13.6 dB의 반사손실, 10.6 %의 대역폭을 얻었다. 주빔 방향 보상 성능을 확인하기 위해 측정 장치를 구축하였다. 측정을 통해 굽힘 변형이 9 %일 때 빔 보상이 정확히 이루어짐을 확인하였다. X-band phased array antenna module for the compensation of deformed beam direction by wing deformation is designed and fabricated. The phased array antenna module consists of array antenna, phase shifter, power divider and control circuit. To select out the best component, the variation of radiation pattern by wing bending and phase error of components is simulated. The fabricated phased array antenna module shows an antenna gain of 5.84 dBi, a return loss of 13.6 dB and a bandwidth of 10.6 % at 9.375 GHz. The test bed was set up to verify the performance of beam direction compensation. This test confirmed that the main beam direction of array antenna has been well restored under wing bending of 9 %.

Reply to comment on ‘Enhancing the security of communication via directly modulated antenna arrays’

Reply to comment on ‘Enhancing the security of communication via directly modulated antenna arrays’

Comment on ‘Enhancing the security of communication via directly modulated antenna arrays’

In a recent study by Hong Zhe Shi et al., a new approach to enhance the security of data transmission using a two-element array based on the directly modulated antenna array technique has been shown. Consequently, Hong Zhe Shi et al. have presented the phase shift values of the array to synthesise a directional modulation (DM) signal in the desired direction. In this current comment, the author demonstrates that the DM signal cannot be synthesised by a two-element phase array because the relative phase information maintain as the conventional baseband modulation signal. The DM signal synthesised using a phase array needs at least three elements.

A 60-GHz-band 2 x 4 planar dipole array antenna module fabricated by 3-D SiP technology

A 2 × 4 phased array antenna module has been developed for 60-GHz-band short- range high-speed wireless communication terminals. To realize the required vertical distance between the antenna elements, the module is made of five sheets of multi-layered organic substrates vertically stacked with Cu balls, and the 1 x 4 dipole array antenna is placed on both the top and bottom organic substrates. To reduce the mutual coupling between the element antennas, a monolithic microwave integrated circuit (MMIC) is flip-chip mounted on the feed line of each element antenna. The Au-stud bump flip-chip mounting technique helps achieve a lower return loss in the transition section at the MMIC than the Au-wire bonded. The placement accuracy of each antenna element in the vertical direction, 60-GHz signal vertical interconnection between the substrates with Cu balls, and flip-chip mounting of the MMIC are confirmed by 3-D computed tomography (CT) scans.

Reliability study of a tunable Ka-band SIW-phase shifter based on liquid crystal in LTCC-technology

A tunable substrate-integrated waveguide phase shifter using low-temperature co-fired ceramic (LTCC)-technology is presented in this paper. By changing the effective permittivity in the liquid crystal (LC)-filled waveguide, the differential phase can be tuned continuously. This is achieved by means of an analog signal applied to the electrodes, surrounding the LC. The design allows for precise tuning of the differential phase, which is proven with a Monte Carlo measurement resulting in phase errors of less than 3° at 28 GHz. Besides that, the ambient temperature dependency of the module is shown. The phase shifter has a high integration level and can be included into a complete and lightweight single-phased array antenna module. The phase shifter is realized with a high level of integration which is available through the multilayer process of the LTCC. It has a length of 50 and provides a differential phase shift of more than 360° at 28 GHz. The figure of merit for tunable phase shifters is &gt;40°/dB.

A single objective approach for suppressing sideband radiations of ultra-low side lobe patterns in time-modulated antenna arrays

In this paper, a novel optimization method based on single objective, that is, minimization of sideband radiation (SBR) of ultra-low side lobe, narrow beam patterns in time modulated antenna arrays (TMAAs) is proposed. The proposed method utilizes the weighting vectors of the low side lobe Dolph-Chebyshev/Taylor series patterns as the dynamic excitation coefficients of the desired pattern at fundamental radiation. Differential evolution algorithm is employed to distribute the static amplitudes and switch-on time durations in such a way that in the optimization process, dynamic excitation distribution remains the same. Static amplitudes are perturbed in a predefined search range of (0.25, 1), whereas the weighted values of switch-on time durations are obtained by dividing dynamic excitation coefficients by static amplitudes. The technique greatly simplifies the difficulties of multi-objective TMAA synthesizing problem by reducing it to a single-objective optimization problem. Numerical examples for a 32-element linear array are presented to produce ultra low side lobe Taylor and Dolph-Chebyshev pattern with low value of maximum sideband radiation (SBRmax). The optimization results of the proposed method are also compared with those obtained by other optimization techniques, which have been reported previously.

Enhancing the security of communication via directly modulated antenna arrays

A new approach to enhance the security of data transmission using direction dependent antenna modulation based on an array with wide element spacing combined with directional array elements is presented. For illustrative purposes, the system investigated, and reported here, consists of an array of only two elements but the approach is general and can be extended to multi-element array systems. It is shown that by increasing the element spacing of an array the directional error rate characteristics of the system, in a given direction, can be significantly improved. Furthermore, the directly modulated system shows superior error rate performance to that of an equivalent, conventionally modulated, system in the grating lobe directions. The error rate characteristics of the proposed system are analysed for two scenarios: firstly when the angular separation between an eavesdropper and the intended recipient is small and secondly for the case when a potential eavesdropper is located much closer to the transmit antenna than the intended recipient.

Design of a novel monopulse antenna system using the time-modulated antenna arrays

A novel monopulse antenna for a tracking radar system is proposed using the time modulated antenna array technique. The time modulation technique applied in the antenna arrays overcomes the usual need for compromise between sum and difference beams and avoids the need for implementation of two separate feed networks. The time modulated antenna array also relaxes the error tolerance of the tracking accuracy from the amplitude and phase errors, due to the new design freedom of “time” which can be controlled precisely and quickly. Moreover, the position of the target can be recovered by two reflected echoes from one previously transmitted pulse, thus the tracking errors resulting from the excitation errors and receiver noise in conventional antenna arrays can be greatly alleviated. Numerical results show that with the aid of time modulation technique, one sum beam and two difference beams can be simultaneously obtained either for the boresight or off-boresight target tracking. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.

A Study on the Application of Time Modulated Antenna Arrays to Airborne Pulsed Doppler Radar

The time modulated (TM) linear arrays with variable aperture sizes (VAS) are applied to the airborne pulsed Doppler (PD) radar system in this paper. The VAS arrays which have great flexibility in the control of the aperture excitations are employed to synthesize low/ultra-low sidelobe patterns in the PD radar system, and the optimized time sequences obtained via the differential evolution (DE) algorithm is used to minimize the average power loss due to the time modulation. Numerical simulation results of the signals transmitted and received by PD radar based on the VAS arrays show that the time modulation changed the waveforms of the signals in time domain but the received signals also contain the correct range and velocity information of the moving target.