Phased Array Antenna Calibration Research Articles

A Fast and Efficient Calibration Method for Phased Array Antennas Using Fourier-Structured Excitation Matrix

This article presents a novel phased array antenna calibration method. Unlike conventional phased array calibration methods equipped with only one probe antenna in the far-field setup, multiple measurement probes are introduced in the proposed algorithm to significantly improve the measurement efficiency. Specifically, a novel construction method for an excitation matrix (which contains excitation coefficients for phased array elements) is proposed, where phase differences introduced by the spatial locations of the multiple probes are perfectly incorporated into the Fourier-structured excitation matrix, thereby presenting the best measurement efficiency without sacrificing the array calibration accuracy. The proposed method can offer robust array calibration results (guaranteed by the low condition number of the constructed excitation matrix with Fourier structure) and high measurement efficiency (offered by multiprobe setups). To experimentally validate the proposed algorithm, a multichannel (i.e., multiprobe) far-field measurement setup was utilized. A four-element open-ended waveguide array operating at 2.6 GHz and two-probe far-field systems were employed as the antenna under test (AUT) and multiple probes, respectively, to validate the effectiveness and robustness of the proposed phased array calibration algorithm. The proposed algorithm will be highly valuable for efficient phased array calibration, especially for future antenna systems equipped with large-scale antenna configurations.

Transfer-Learning-Assisted Multielement Calibration for Active Phased Antenna Arrays

A transfer-learning-based method for accelerating power-only calibration of phased array antennas by combining the conventional array theory with deep learning is presented in this communication. The existing power-only calibration methods either require a significant number of measurement cycles or have restrictive phase shifter resolution requirements. The proposed array calibration method uses a surrogate model to calibrate all the array elements in one pass without restricting phase resolution requirements. We developed a novel feature extraction scheme (FES) that picks out the most important power features resulting in reduced measurement cycles. The burden of data acquisition for model training is further reduced by relational knowledge transfer learning. The surrogate model acquires its general calibration capability from massive theoretical data, which is easily collected by the radiation multiplication theorem, and captures the detailed nonideal response from a small number of simulations. The proposed methodology has been demonstrated and tested on several arrays for validation. The effectiveness and performance of the method have been verified, and hence, it can serve as a complementary tool to accelerate the calibration process of phased antenna arrays.

Phased Array Antenna Calibration Method Experimental Validation and Comparison

This paper investigates the calibration methods appropriate to the phased array calibration in practical measurement setups. The rotating element electric field vector (REV) method, fast amplitude-only calibration method, and complex amplitude calibration method are compared and analyzed in the same measurement setup. The objective is to investigate the robustness of the discussed algorithms with different measurement ranges, with or without the support of array element on/off operation. A 4×8 uniform rectangular array (URA) is used to validate the three different calibration methods. The measurement results indicate that array element on/off measurement in the far field is suitable to be a reference calibration method in practical setup. The REV and complex amplitude calibration methods present comparable accuracy while fast amplitude-only calibration method provides less accurate calibration results in this measurement. Further, it was demonstrated that with element on/off data available, same calibration accuracy can be achieved either in small or large measurement ranges for the three different calibration methods. However, when the element on/off data is not available, the array calibration accuracy deteriorates with small measurement range. This paper presents the method to calibrate the phased array antenna in near-field by using the element on/off data. This is a very useful method in massive production line calibration. The calibration errors of different calibration methods are analyzed. Furthermore, this paper also analyzes the uncertainty of each method.

Skeleton Array를 이용한 능동 위상배열 안테나 교정

본 논문에서는 skeleton array 이용하여 능동 위상배열 안테나 채널간의 오차를 교정하는 방법을 제안한다. 상호 간섭을 이용한 내부 교정 방법은 추가적인 시스템이 필요하지 않지만, 상호 간섭 측정에 많은 시간이 소요된다는 단점이 있다. 이러한 상호 간섭 측정에 소요되는 시간을 최소화하기 위하여 skeleton array를 도입하였다. 또한, 11×11 배열 교정을 통하여 제안된 방법을 검증하였다.

Mutual coupling을 이용한 능동 위상배열 안테나 교정

본 논문에서는 mutual coupling을 이용하여 능동위상배열 안테나 채널 간의 진폭과 위상 오차를 교정하는 방법을 제안한다. Mutual coupling을 이용한 교정 방법은 내부 소스원을 사용하기 때문에 추가적인 시스템이 필요하지 않다는 장점이 있다. 제안하는 교정 방법을 검증하기 위하여 5×5 비발디 안테나를 설계하였으며, 채널 간 오차가 없는 모델과 오차가 교정된 모델의 특성이 일치함을 통하여 제안하는 방법을 검증하였다.

Fast Phased Array Calibration by Power-Only Measurements Twice for Each Antenna Element

This paper proposes a novel power-only measurement method for phased array antenna calibration. Besides the total array power, only one phase shift and two power measurements for each array element are required to determine the element complex electric field distortion, one by shifting the element’s phase of π/2 and the other by turning the element under test off. The theory of the proposed calibration method is given, and the closed form formulation of the element amplitude and phase distortions is derived. From the mathematical point of view, it is the minimum required measurements that use two scalar values to determine one complex vector. Numerical simulations and experiments are conducted to validate and demonstrate the effectiveness of the proposed calibration method.

A Multiple Element Calibration Algorithm for Active Phased Array Antenna

In this paper, we investigate an octagonal phase settings algorithm for multiple k th elements in improving the calibration techniques for an active phased array antenna using the power measurement output of each element. An active phased array antenna calibration requires simultaneous measurement of each antenna element of an array to guarantee high target precision to meet a specific operation. Therefore, each element in the active phased array antenna requires an efficient and accurate amplitude and phase variation in order to calibrate the array antenna system power output with the excitations of the antenna elements using linear equations to adjust the corresponding amplitude and phase errors. Calibration and optimization in an active phased array system steer antenna beam to the desired direction and they are applicable in radar communications, automobiles, communication systems, and electronic warfare.

Phased Array Antenna Calibration with Probe Positioning Errors [Measurements Corner

Calibration is often performed inservice with a calibration probe (CP) located in the far field (FF) of the antenna under test (AUT). Nevertheless, in some cases, it is suitable to work in the near-field (NF) environment. NF calibration is especially useful for large-aperture phased-array antennas (PAAs), when it is often complicated to arrange the CP in the FF of the antenna array. Recalculating complex initial coefficients from the NF to the FF requires taking into account distances between the phase centers of the emitters of the channels under test and the phase center of the CP. In this article, the influence of errors in the determination of coordinates of a CP on the calibration results, together with antenna pattern distortions, are considered. The derived formulas could be used to produce new requirements on the accuracy of an AUT in a CP survey.

Design and Performance of Frequency Selective Surface With Integrated Photodiodes for Photonic Calibration of Phased Array Antennas

The design, fabrication, and integration of a frequency selective surface (FSS) with integrated photodiodes to allow for photonic calibration of phased array antennas is presented. The design includes embedding electrically short dipole antennas in each unit cell of the FSS, with a zero-biased photodiode placed across the gap of the diode. Fibers from an optical distribution network are passed through the honeycomb core of the frequency selective surface and pigtailed to the photodiodes. The RF performance of the frequency selective surface with integrated optics is investigated via simulations and measurements, and the results show that the structure maintains RF-transparency.

Performance of 16-channel, photonic, phased-array antenna calibration system

Experimental results from a 16-channel photonic phased-array calibration system are presented. The calibrator utilises an array of fibre-pigtailed, zero-biased photodiodes as optical transducers to transmit an RF signal from an electrically-shorted dipole integrated in each unit cell of a frequency-selective surface radome. RF phase and amplitude stability, along with the overall RF transparency of the hardware, are presented. The system successfully demonstrates a solution with performance suitable for in situ real-time calibration of phased-array antennas.

Phased array antenna calibration and pattern prediction using mutual coupling measurements

A technique which utilized the inherent mutual coupling in an array to both calibrate and predict the radiation patterns of a phased-array antenna is investigated. The only restriction of the technique is that the ability to transmit and receive with pairs of the array elements is required. The theory associated with array mutual coupling and its relationship to both array calibration and array patterns is discussed. The design of a test bed phased-array antenna is covered. The mutual coupling technique (MCT) is used experimentally to calibrate the test array as well as to predict the array radiation patterns. It is shown that the results obtained by MCT are in good agreement with conventional far-field measurements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>