A 4-Element Ka-Band Phased-Array Receiver With Code-Domain Hybrid Beamforming

This letter presents a 4-element phased-array receiver with code-domain hybrid beamforming (CDHBF) in 65-nm CMOS technology. Code-division multiplexing is used to fully preserve the flexibility in the digital domain while using a single RF interface, which reduces the RF chain complexity, reduces the chip area, and improves power efficiency. Phase and amplitude control circuits are also integrated into each path to keep the flexibility to use the receiver as a traditional 4-element phasedarray. The phased-array and code modulator can be turned on or off to reconfigure this structure into an analog beamformer, hybrid beamformer, and digital beamformer according to applications. An over-the-air wireless measurement is set up and two streams from different directions are simultaneously received and processed by the proposed receiver. The measured EVMs in CDHBF mode are -22.7 dB and -20.5 dB for 100 Ms/s and 200 Ms/s data streams, respectively, without any digital domain equalization.