A Simultaneous Wideband Calibration for Digital Beamforming Arrays at Short Distances [Measurements Corner]

Abstract

Massive multiple-input multiple-output (MIMO) is seen as an essential feature for the fifth-generation (5G) communication systems. To ensure the array performance for beamforming or nulling, it is important to conduct array calibration beforehand. Since 5G massive MIMO base stations (BSs) are expected to be highly integrated, i.e. the antenna arrays are directly integrated with the transceiver front ends, there may be no antenna connectors reserved for calibration purpose. In this case, array calibration will be done fully over-the-air (OTA). In this work, we propose a fast and short-distance OTA calibration method for massive MIMO BSs based on digital beamforming structures. Specifically, the correlation-based sounding technique is utilized for simultaneous measurements, and phase deviation due to the spherical wavefront at short distance is corrected with the known propagation geometry. Moreover, a multipath cancellation scheme is adopted to improve the calibration accuracy. An experiment is conducted in an open laboratory environment to assess the validity and robustness of the proposed calibration method.

Convolutional Neural Network for Array Size Selection of a Dual-band Reconfigurable Array

“…In order to test the effectiveness of the CNN, 1,000 arbitrary radiation pattern masks were simulated for array sizes N y ,N z in [2,4,6,8] and main beam directions [-45 ≤ θ , φ ≤ 45] deg. The operating frequency was randomly assigned to one of the four unit cell frequencies listed in Table 1.…”

“…The set of images are generated with equations ( 6) and ( 8) using a variable array shape, reconfigurable switch state, and steering direction, which are represented in the label p. We also scaled the pixel values to the interval [-1,1]. The length of the array in each dimension is allowed to be within [2,4,6,8], and the steering direction û0 is constrained to a 45-degree cone relative to boresight. Also, a −35-dB Taylor window is used to reduce sidelobes.…”

“…Multichannel arrays are commonly used as multipleinput multiple-output (MIMO) antennas in communications [1][2][3] These antennas are essential for multi-beam forming [4], fast angle-of-arrival estimation [5], interference suppression [3], and array calibration [6][7]. The reconfigurable antenna has gained much attention for MIMO arrays because it can facilitate smart antenna technology in which the system senses the environmental conditions and automatically changes the antenna elements and circuitry to operate at different frequencies [2], with different polarization states [8], and with different radiation patterns [1,9], or a combination thereof [10].…”

A Mutual Coupling-Based Full Self-Online Calibration Method for Antenna Arrays in Uplink

“…Large-scale phased array antennas are considered to play fundamental role in the fifth-generation (5G) [1], [2] and future sixth-generation (6G) wireless communication systems [3], [4]. The new generation 5G and 6G wireless systems are expected to be used in many civil, commercial, and military areas such as massive multiple-input multiple-output (mMIMO) [5], [6], autonomous driving [7], satellite systems [3], internet of things (IoT) [4], anti-jamming, and antispoofing [8]. With the latest developments in phased array antenna technology, beamforming is intended to be one of the key techniques for the next generation wireless systems [1], [2], [9].…”

“…The near-field or far-field probing methods employ a test probe moved across a phased antenna array to measure the relative phase and amplitude of each antenna element [6], [17], [18]. The peripheral fixed probe methods use one or more fixed probes around the periphery of the phased array to measure the coupling between antennas and compensate for excitation errors [19], [20].…”