A 2.5–25-GHz 10:1 Bandwidth Eight-Channel Rx Beamformer Chip Based on Quad-Pole I/Q Network for Ultra-Wideband Systems

This article presents an ultra-wideband quad-pole $I/Q$ network and its implementation in a 10:1 bandwidth beamformer receiver from 2.5 to 25 GHz. Unlike conventional quadrature all-pass filter (QAF) network with second-order response, this design uses a voltage-to-current (V–I) conversion architecture to achieve a fourth-order quadrature phase response, maintaining a $\lt \pm 5^{\circ } $ phase error over a decade of bandwidth. The network also features third-order IQ gain error response with low conversion loss, making it an ideal candidate for beamformer designs. A circuit implementation of the V– $I~IQ$ network on an ultra-wideband phase shifter is presented using a high-linearity common-base (CB) vector modulator (VM). To demonstrate the efficacy of this design, a single-channel beamforming receiver and an eight-channel beamformer were fabricated and measured. The channel is measured to have an rms phase error of 2.7° at 2.5–25 GHz without any calibration. The eight-channel beamformer chip shows an IP1dB of −28 to −25 dBm with a channel NF of 2.5–4 dB at 2.5–25 GHz. For base station applications, a 16-element linear array using Vivaldi antennas is also presented, demonstrating the ultra-wideband capabilities of this design and confirming its feasibility for future sixth-generation (6G) FR3 systems.