A Ka-Band Beam-Steering Radar Transmitter Using Active Multiplier and Coupled Delay Line Phase Shifter

Abstract

This paper presents a Ka-band beam steering transmitter exploiting a coupled varactor loaded transmission line (VLTL) phase shifter and a CMOS transmitter chip with an integrated frequency multiplier. The short-coupled line couplers placed along a single VLTL provides multi-phase outputs while minimizing the impedance mismatch and unequal power distribution along the VLTLs. The inherent phase-accumulating nature along the VLTL reduces the burden of wide phase control range required for using separate phase shifters for each channel. Additionally, the frequency multiplier with a multiplication ratio of 8 reduces the required amount of phase change at the reference frequency and therefore the tuning range of the varactor, which also minimize a change of line characteristic impedance to ensure the impedance matching of the VLTL. Hence, a 32 GHz phased array transmitter is implemented using a single VLTL phase shifter operating at a low reference frequency of about 4 GHz. The fabricated $1\times 4$ phased array transmitter achieves a continuous beam steering range of ±20° in the E-plane using a single control voltage. The sidelobe level is below -10 dB at all scan angles and the peak effective isotropic radiated power (EIRP) is 38.1 dBm at 31.6 GHz and the 3-dB bandwidth of 2.4 GHz is achieved.

Keywords

• Phased-array
• VLTL
• beam-steering
• coupler
• phase shifter
• transmitter