An Ultra Low Cost Highly Reliable 18–22 GHz T/R Front-End With Adaptive Sensitivity, Rx Absorptive Calibration, and Fast Switching Time for Phased-Array Radars Applications

This letter proposes a fully integrated K-band front-end architecture for radars targeting extremely low NRE and RE. The RF front-end is composed of an SPDT-less half-duplex low-noise variable gain amplifier (LNVGA) co-designed with a power amplifier (PA) and an Rx coupler for A/φ calibration. The design architecture is built to answer to the multirange detection requirement of many phased-array applications and optimize their calibration in an array configuration. The half-duplex receiver has a gain ≥25 dB between 18 and 22 GHz and is integrating a current steering gain control mechanism for changing the Rx IP1dB up to -5 dBm. For this lowest sensitivity, the minimum 6.5-dB noise figure is affected by only 0.3 dB and conserves an AM-to-PM ≤ 2°. The half-duplex transmitter has a 34-dB small-signal gain and delivers at 20 GHz an output power of +18 dBm with a PAE of 16 % at 4-dB compression. The calibration circuit degrades the Rx noise figure by only 0.1-dB NF while acting as a coupler with 18-dB coupling and 21-dB directivity. The circuit with all its periphery can switch between Tx and Rx in less than 15 ns. Compared to the previous works in similar technology, performances were significantly improved. Despite the very low cost 180-nm CMOS process used, this SPDT-less T/R front-end architecture demonstrates excellent performances for radar applications at K-band frequencies, therefore, presenting a high performance-to-cost ratio. In terms of reliability, this circuit is designed for a life time of more than 106 h under HCI and TTBD degradations at continuous waves.