A 4-Element 60-GHz CMOS Phased-Array Receiver With Beamforming Calibration

A 4-element 60-GHz phased-array receiver RF front-end (RFE) employing LO-path phase-shifting configuration is presented. A wide bandwidth from 57 to 66 GHz is achieved by using multiple design techniques, including wide-band input matching network using on-chip baluns, peak-frequency staggering in the LNAs, and resonant-frequency tuning of the LC load in the first down-conversion stages. Furthermore, beamforming calibration is implemented by sequentially performing gain equalization, I/Q calibration and successive-approximation phase tuning. Implemented in a 65-nm CMOS process, each element measures gain of 21 dB and NF of 7.2 dB and IP1dB of -21 dBm in high-gain mode while achieves IP1dB of -12.5 dBm with gain of -2 dB and NF of 20 dB in low-gain mode. With beamforming calibration, the peak-to-null ratio of the synthesized 4-element array pattern is improved from 16.5 dB to 28.5 dB, corresponding to phase error of ±0.6° and amplitude mismatch of ±1.1 dB. The whole system consumes 320 mW from a 1.2-V supply and occupies a core area of 2.0 × 1.3 mm² excluding pads.

I. Introduction

To achieve high data rates without complicated modulation schemes, many emerging wireless applications such as high-definition video streaming have recently been focused in the millimeter-wave (mmW) region. In particular, the 60-GHz unlicensed band is of great interest due to its unprecedented wide bandwidth of up to 9 GHz. To overcome the substantial path loss at 60 GHz and to meet the stringent link budget requirement for a sufficient signal-to-noise ratio (SNR) of the received signal, the RF transmitter should radiate a large power while the receiver is required to possess a high gain and a low noise figure (NF) for a high sensitivity. Unfortunately, at mmW frequencies, not only power amplifiers have very limited output power, but low-noise amplifiers also have very low gain and high NF. As a result, there are still major challenges in implementing a 60-GHz CMOS RF transceiver using advanced CMOS technologies for high integration level and low cost, even though their cut-off frequency has reached hundreds of GHz already [1]–[7]. A promising solution to addressing this critical issue is to use phased-arrays emulating a high-gain antenna by spatial power combining [8]–[9]. Meanwhile, their beam-steering capability is very useful in deploying mmW systems as picocell or femtocell networks.