Caudill Derek, Chuang Jack, Jun Sung Yun, Gentile Camillo, Golmie Nada
RF Technology Division, National Institute of Standards and Technology, Boulder, CO 80305 USA.
Wireless Networks Division, National Institute of Standards and Technology, Gaithersburg, MA 20899 USA.
IEEE Trans Microw Theory Tech. 2021 Nov;69(11). doi: 10.1109/tmtt.2021.3104278.
We propose a 28.5-GHz channel sounder that switches through all antennas of multiple dual-polarized 8 × 8 phased arrays at the transmitter and receiver and performs beamforming in postprocessing through digital weights to synthesize a sweepable beam. To our knowledge, we are the first to implement-what we refer to as- with phased arrays for millimeter-wave channel sounding, realized through highly stable Rubidium clocks and local oscillators coupled with precision over-the-air calibration techniques developed in house. By circumventing the time-consuming programming of analog weights that is associated with analog beamforming-what phased arrays are designed for-we can sweep a 3-D double-omnidirectional dual-polarized channel in just 1.3 ms, for real-time sounding. By in turn circumventing the coarse precision of analog weights, we can synthesize ideal beam patterns thanks to the effectively infinite precision of digital weights, enabling fine weight calibration for the nonidealities of the system hardware and fine weight tapering for sidelobe suppression. This translates to average estimation errors of 0.47° in 3-D double-directional angle, 0.48 dB in co-polarized path gain, and 0.18 ns in delay, as substantiated by field measurements.
我们提出了一种28.5吉赫兹的信道探测仪，它在发射机和接收机处切换多个双极化8×8相控阵的所有天线，并通过数字加权在后期处理中执行波束形成，以合成一个可扫描波束。据我们所知，我们是首个使用相控阵实现毫米波信道探测的，这通过高度稳定的铷钟和本地振荡器，结合我们自主研发的精确空中校准技术得以实现。通过避免与模拟波束形成相关的耗时模拟加权编程（相控阵就是为此设计的），我们能够在仅1.3毫秒内扫描一个三维双全向双极化信道，实现实时探测。反过来，通过避免模拟加权的粗精度，由于数字加权具有实际上无限的精度，我们能够合成理想的波束方向图，从而能够针对系统硬件的非理想性进行精细的加权校准，并针对旁瓣抑制进行精细的加权渐变。现场测量证实，这在三维双方向角度上的平均估计误差为0.47°，在同极化路径增益上为0.48分贝，在延迟上为0.18纳秒。
