A Four-Element True-Time-Delay Slice-Based Receiver Array for FR3 Upper Mid-Band Wireless

A continuous beam angle resolution enables precise beam steering and prevents beam squinting, especially in dense environments where large arrays create narrow beams to maximize capacity. This work proposes a continuous beam angle reconfigurable four-element receiver (RX) for the FR3 frequency band. The implemented vector modulator (VM) phase-shifting mechanism is based on the slice-based RX for the coarse stage and phase-shifting polyphase filters (PPFs) in the local oscillator (LO) paths for the fine stage to overcome the limited phase resolution. The beamformer is equipped with current-mode true-time delay (TTD) units to further assist with better linearity performance and signal-to-noise ratio (SNR) improvement at the band edges. Fabricated in TSMC 65-nm complementary metal-oxide–semiconductor (CMOS), the prototype occupies an area of 1.65 mm², consuming 14 mA/element centered at 7.5GHz. The measured maximum single-channel gain is 22 dB, with a minimum noise figure (NF) of 7.48 dB while having an $S_{11}\lt -10$ dB across 7.28–7.78-GHz input frequency span. A root mean square (rms) phase error of 0.76° is achieved while showing continuous phase shifting over 360°. The TTD units improve the beamformed down-converted 100-MHz wideband (WB) up to 1.5-dB gain at the band edge. Moreover, over-the-air (OTA) measurements show the reception of a single-tone signal at a 297.88-cm distance between RX and a horn antenna.