65nm CMOS phase conjugator for retro-directive short-range wireless power transfer

We present an ultra-compact phase conjugator for a radio frequency (RF) system of a retro-directive array (RDA) that is, suitable for a short-range wireless power transfer (WPT) application. The proposed phase conjugator consists of a mixer, buffer, and limiter, and provides not only an accurate conjugate phase but also small jitter, variable gain, and linear phase characteristics. The phase conjugator was implemented using Samsung 65 nm RF CMOS technology. The size of the core chip was 1150 × 880 μm ² . The circuit used a supply voltage of 1.4 V and a current of 10 mA. All ports are matched to 50 Ω. In the measurements, the RF, intermediate frequency (IF), and local oscillator (LO) frequency of the mixer are 2.5, 2.4, and 4.9 GHz, respectively. The phase conjugator provides an excellent RF-IF isolation of less than −45 dB and small RMS jitter of less than 4.3 ps. The limiter enables the phase conjugator to exhibit a constant phase of 168.1 ± 0.1 ⁰ and a constant output power of about −22.5 ± 0.3 dBm in the input power range from −10 dBm to 0 dBm.