High-Resolution 160-GHz Imaging MIMO Radar Using MMICs With On-Chip Frequency Synthesizers

Abstract

A high-resolution frequency modulated continuous wave imaging radar for short-range applications is presented. A range resolution of about 1 cm is achieved with a bandwidth of up to 16 GHz around 160 GHz. In order to overcome losses and large tolerances on a printed circuit board (PCB), 8 coherently coupled monolithic microwave integrated circuits (MMIC) are used, each with one transmit and receive antenna on-chip and each representing a single channel radar system. The signals on the PCB are below 12 GHz, which facilitates fabrication and enables a design with low-cost substrates. The MMIC comprises a phase noise optimized architecture with a fully integrated on-chip frequency synthesizer. Due to partly uncorrelated phase noise between the frequency synthesizer components, the noise level is increased in bistatic radar measurements between two different MMICs, which is explained by a thorough phase noise analysis. Time-division multiplexing is used to realize a multiple-input multiple-output system with a virtual array of 64 elements and an angular resolution better than 1.5 • for the designed array. The positioning tolerances of the MMICs are included into the design resulting in a robust array design. The high-resolution radar performance is proven by imaging radar measurements of two exemplary scenarios.

Range-Angle Coupling and Near-Field Effects of Very Large Arrays in mm-Wave Imaging Radars

“…This is particularly challenging at higher frequencies and comes with an increased hardware effort. For apertures of medium size (30 λ 0 -70 λ 0 ), the local oscillator (LO) signal can be distributed at a lower frequency band and multiplied on the monolithic microwave integrated circuit (MMIC) [10], [13], [21]. However, for large apertures, high losses of the distributed signal aggravate a coherent LO distribution concept.…”

“…Typically, the DoA of the target is estimated after a previous range-Doppler processing and subsequent target extraction [16]. For typical multiple-input multiple-output (MIMO) radars using conventional aperture sizes or modulation bandwidths, the difference in path length of the incident wave at the receive antennas does not noticeably exceed the range resolution of the radar, see [11]- [13].…”

Calibration-Based Phase Coherence of Incoherent and Quasi-Coherent 160-GHz MIMO Radars

“…Typically, imaging radars above 100 GHz are implemented completely coherently, as shown in Fig. 1(a), by distributing a single generated radio frequency (RF) signal between 1 and 100 GHz to all radar MMICs [8]. In comparison, the radar architectures in Fig.…”

“…The noise level of the IF signal determines the achievable SNR and the resulting system performance. It is determined by a superposition of thermal noise, quantization noise, and phase noise [8], [22]. In this section, a system performance comparison of the quasi-coherent and the incoherent system after the frequency and phase corrections according to Section III is given.…”

“…In order to perform coherent beamforming, imaging radars require a time, frequency, and phase synchronization between the individual transmit (TX) and receive (RX) signal paths [8]. Thus, imaging radars are usually realized fully coherently, i.e., the frequency-modulated continuous-wave (FMCW) ramp oscillator (RO) signal is derived from a single PLL and afterward distributed to the individual TX and RX channels [9]- [14].…”