X/Ku-band 8-element phased arrays based on single silicon chips

This paper presents a complete 8-element X/Ku-band phased array based on a single silicon chip. The phased array is integrated together with the antennas and digital control circuitry on a single Teflon board. The chip-on-board package, together with 8 X/Ku-band RF inputs and one RF output in a 2.2×2.5 mm² area, and the appropriate grounding and Vcc connections, are modeled using a 3-D EM solver. The design results in a low coupling between the different RF ports, and ensures stability even with a channel gain of 20 dB at 12 GHz. The measured patterns show a near-ideal performance up to a scan angle of 60° with an instantaneous scanning bandwidth of 11.4-12.6 GHz (limited by non true-time delay connections between the antennas and the chip). Temperature tests indicate that the silicon chip maintains excellent phase stability and rms phase error up to 100°C. To our knowledge, this represents the first system-level measurements on silicon-chip phased arrays.

I. Introduction

Silicon-based phased arrays have now been demonstrated from X-band to V-band using RF beam-forming techniques [1]– [7]. The main advantages of the RF architecture are its simplicity, system-level linearity, low power consumption (no LO drivers, no LO distribution), and the use of a single high-performance transceiver. Most of the published work presents on-chip measurements using CPW probes, but this ignores the packaging aspects of multi-element phased arrays, such as RF transitions and associated impedance matching networks, coupling between the different RF ports, V cc de-coupling and oscillations–especially in high gain designs, and the creation of a low-inductance ground between the chip and the antenna distribution board. These issues if not properly designed and mitigated, can degrade the phased-array chip performance and render it un-usable in practical implementations. Fig. 1. Functional block diagram of the 8-element silicon phased array chip (from 1 D. Fig. 2. (a) The 8-element X/Ku-band phased array with the silicon chip at its center, and (b) input and output transmission lines around the silicon chip ().