A CMOS 22-29GHz Receiver Front-End for UWB Automotive Pulse-Radars Vipul Jain', Sriramkumar Sundararaman2, and Payam Heydari
1Nanoscale Communication IC Lab, University of California, Irvine, CA 92697 2Avago Technologies, San Jose, CA 95131
Abstract - The design of a CMOS 22-29GHz pulse-radar receiver (RX) front-end for ultra-wideband (UWB) automotive radar sensors is presented. Fabricated in a 0.18,m CMOS process, the 3mm2 RX chip achieves a conversion gain of 35-38.1dB, noise figure of 5.5-7.4dB and input return loss less than -14.5dB in the 22-29GHz band. The phase noise of the constituent QVCO is -107dBc/Hz at 1MHz offset from a center frequency of 26.5GHz. The total dc power dissipation of the RX including LO/output buffers is 131mW. Index Terms CMOS integrated circuits, direct-conversion receiver, LNA, pulse radar, quadrature VCO, ultra-wideband (UWB).
I. INTRODUCTION
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Short-range UWB radars providing a high-resolution safety= zone around the vehicle are essential for incorporating
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collision aodance, precic sne airbag activation, parking Inert assistance, and short-range adaptive cruise control (ACC) To baseband processor stop-and-go capability. Several of these functions require a&Dm radar range resolution of only a few centimeters and detection of objects at distances ranging from 10cm to 4Gm. Fig. 1: Block diagram of the UWB RX for pulse-radars Frequency bands around 25GHz have been allocated exclusively for UWB vehicular radars [1]. Since small transmitter (TX) [2]. Pulse-radars, on the other hand, can form-factor and low cost are imperative for this application, an attain a high dynamic range as the RX and TX operate in a all-CMOS implementation is attractive. SiGe realizations have time-duplexed fashion. been reported [2]-[3] but suffer from limited bandwidth and The RX is based on a pulse-radar architecture employing high power dissipation. Narrowband 24GHz transceivers for time-gated quadrature correlation, as shown in Fig. 1. high data-rate wireless communications in CMOS Primarily a direct-conversion architecture, this pulse-radar technologies have been reported in [4] and [5]. RX comprises of a 22-29GHz UWB LNA with a peak This paper presents a CMOS short-range automotive power-gain of 18dB and minimum noise-figure (NF) of 4.5dB, pulse-radar RX front-end operating in the FCC-approved band IIQ mixers, a QVCO, pulse formers, and baseband variable from 22 to 29GHz. Circuit techniques used in the UWB RX gain amplifiers (VGAs). A free-running injection-locked front-end design enable the system to achieve a high range QVCO generates I and Q differential LO signals, which are resolution and detect objects at a close range, thereby fed to the pulse formers through high-frequency tuned buffers. demonstrating suitability for integration in short-range radar The pulse formers in Fig. 1 upconvert the baseband pulses to systems. The allocated power-constrained spectrum is RF by modulating them with the 26.5GHz LO carrier. After efficiently used while minimizing the interference with other being amplified by the LNA, the received RF pulses are systems operating in the same frequency range [1]. The correlated with local pulses from the pulse formers using IIQ remainder of this paper is organized as follows: Section II mixers. The cross-correlation products are amplified by the discusses the architecture of the receiver. Section III describes baseband VGAs and fed to integrate and dump circuits. The the circuit design of the building blocks of the front-end. design of pulse generator and integrate and dump circuitry is Measurement results are presented in Section IV. Finally, not a part of this paper. Section V provides concluding remarks. Because of extremely low transmit duty cycle [2] and time-gated operation, oscillator pulling is negligible. FCC
