V-band Direct-RF DBF Receiver with RF-Input-Free Sampling-Timing Calibration Method

We propose a V-band direct-RF digital-beamforming (DBF) receiver that employs a RF-input-free sampling-timing calibration method. This method controls phase difference between the LO signal of the sample-and-hold integrated circuit (S/H-IC) and the clock signal of the ADC, using LO leakage, produced by a controlled DC differential mismatch at the S/H IC input, to maximize conversion gain. The proposed method obviates the need for a dedicated calibration signal. We implemented an S/H-IC with the proposed calibration function in 45 nm CMOS-SOI and demonstrated that the proposed method can limit gain variation due to sampling-timing to less than 1.4 dB. Furthermore, we realized a brick-type V-band 8-element DBF receiver module on a PCB incorporating the S/H-IC, with an element pitch of 4.4 mm. At 60 cm-OTA measurements, the V-band DBF receiver module using direct-RF architecture achieved a data rate of 3.2 Gbps using 4-element combining.