Active Phased Array Antennas (APAA) are widely used in various applications such as weather radars and mobile communication base stations. APAA is a high-performance antenna that consists of multiple element antennas and microwave control circuits connected to each element antenna. By electronically changing the excitation phase of each element antenna using phase shifters, the beam direction can be controlled without mechanical scan. Additionally, the variable gain control circuits allow for the suppression of side lobes. However, implementing both the phase shifters and variable gain circuits requires a larger size. Recently, a variable gain phase shifter has been proposed that realizes the phase shift function and amplitude control function in a single circuit in a small size. However, the insertion phase changes with the control, degrading the beam quality of the APAA. To address this issue, a variable gain phase shifter with phase compensation using varactors is proposed in this paper.

By focusing on the change in passband phase characteristics of the variable gain phase shifter due to input capacitance variations with the control, a varactor is incorporated in the input terminal to compensate for the phase variation during control, achieving low phase shift and amplitude errors.

A Ka-band variable gain phase shifter with the proposed phase compensation technique was prototyped using a 130 nm SiGe BiCMOS process. A comparison is made with the case where a compensation technique is not used, confirming improvements of 0.76° in phase shift error and 0.06 dB in amplitude error. The performance achieved includes a gain control range of 23 dB, an amplitude error of less than 0.19 dB, and a phase shift error of less than 0.75° and it also demonstrated a compact variable gain phase shifter with high-precision variable gain and phase shifting.

This paper demonstrates that the proposed variable gain phase shifter technology contributes to improving the beam quality of APAA and makes a significant contribution to the widespread adoption of social infrastructure. Therefore, this paper is highly evaluated as a paper worthy of the Society's Paper Award.