Accurate knowledge of initial complex excitation coefficients for phased-array elements is essential to ensure accurate array performance. In the literature, many array calibration algorithms have been proposed for this purpose, which generally requires customized phase setting for individual phase shifters connected to array elements. In this article, a new array calibration method is proposed for phased array operating in beam-steering mode only, that is, phase shifts of elements are only simultaneously set according to the beam-steering directions, and therefore, there is no need for dedicated individual element phase tuning. The proposed method requires a minimum number of complex-signal measurements in principle, which enables fast measurement. Furthermore, it is found that the performance of the proposed method is determined by the beam-steering matrix, whose condition number is mainly ruled by the beam-steering angle interval. The proposed method is numerically simulated and experimentally validated in a millimeter-wave (mmWave) phased-array antenna-in-package (AiP) platform at 28 GHz. The proposed method presents good agreement with the well-known rotating element electric field vector (REV) array calibration method, with an amplitude error and phase error within ±0.5 dB and ±5°, respectively. Furthermore, the reconstructed array pattern with the proposed method offers excellent match with the measured array pattern.

This letter presents an improved phased array calibration method based on measured complex array signals with one single probe. All the phased array elements are excited simultaneously in the measurement and only phase reverse of each element is required. The error on the 1st antenna element of the reference method is analysed, which shows it is accumulated as the array size increases. One more measurement with designed element phase settings is introduced to overcome the deficiency. The improved method shows only N + 1 measurements are required to calibrate N antenna elements accurately. Finally, a 4×8 antenna array composed of 4-ridged horn antennas operating at 3:5 GHz was measured to validate the effectiveness of the improved algorithm.

This paper presents a polarization-reconfigurable wideband high-gain antenna based on liquid metal tuning. The antenna consists of a center-feed circular patch antenna with a C-shaped slot as the driven element. To broaden the bandwidth and improve the realized gain, a parasitic circular disc and 13 circular directors are employed. The direction of polarization can be tuned by changing the location of liquid metal alloy contained in the tube. The relationship between the dimensions and the maximally achievable gain has been analyzed. The antenna has exhibited a -10 dB impedance bandwidth from 4.3 to 5.3 GHz (a fractional bandwidth of 21.2%). A 14.4 dBi gain is achieved at 5.3 GHz. The simulation and measurement results show good agreement with each other.

This letter presents a sub-6 GHz cost-effective wideband dual-polarized plane wave generator (PWG) design for the fifth-generation (5G) base station over-the-air test. The proposed nonuniform PWG design is composed of 256 elements and has a dimension of 1.7 m × 1.7 m. Several novel strategies are proposed and implemented to reduce the cost and complexity. To reduce the feeding network complexity and mutual coupling among PWG elements, a novel tapered amplitude-only excitation method (i.e., with the same relative phase excitations among all PWG elements) is proposed. To reduce the number of channels in the phase and amplitude control network, a four-element subarray is applied. Furthermore, the wideband PWG element design and nonuniform configuration are applied to support for ultrawideband operations from 2 to 5 GHz. The proposed PWG design is numerically simulated and experimentally validated. A cylindrical quiet zone of a diameter of 0.9 m and a depth of 0.9 m, with 2.1 m distance to the PWG, is achieved in the measurement for the considered bandwidth, with the typical peak-to-peak E-field amplitude and phase variations less than ±1.25 dB and ±7.5°, respectively, which demonstrated its effectiveness and robustness.

A very small focal-to-diameter (F/D) ratio transmitarray for compact antenna test range (CATR) application is proposed in this article. The transmitarray comprises a feed antenna, a metasurface for phase modulation (MPM), and another one for amplitude modification (MAM). MPM and MAM are implemented using the same metasurface cell but with different cell selections and arrangements. A holistic phase-only design method determines whether the metasurface is for amplitude modification or phase modulation. A CATR collimator with an overall low profile is realized through the joint design of MAM and MPM. The proposed technique overcomes the limits of the ordinary metasurface lenses and enables plane wave generation with a short focal length and sizeable quiet zone. The resulting CATR demonstrates a 50% quiet zone of the aperture size with ±0.5-dB amplitude and ±5° phase errors by full-wave simulation. For further verification, a prototype is fabricated, and its experimental results confirm the simulations.

There has been growing interest in employing phased array systems with large-scale array configurations in the cellular, satellite and automotive applications. Array calibration is essential to ensure phased array beamforming performance. The amplitude-only calibration methods, which only require amplitude measurement, are highly attractive especially when phase measurement is unavailable or unreliable. One of the most widely applied method is the rotating element electric field vector (REV) method.However, it becomes more sensitive to noise when the element number of the array under test (AUT) increases, making it unreliable for large-scale phased array calibration. In this work, a novel amplitude-only calibration method is proposed for large-scale phased arrays when the signal-to-noise (SNR) condition in the measurement is low. The basic idea is to divide the AUT elements into several groups and to perform the group-wise REV operations of the AUT in multiple rounds. Numerical simulations and experimental results have validated the effectiveness and advantages of the proposed method in calibrating large-scale phased arrays over the classic element-wise REV method.