An FM-CW radar module with front-end switching heterodyne receiver

Abstract

Antenna A b s t r a c t Triangular coupler We have developed a 60-GHz FM-CW radar module that generates sidebands by switching a HEMT front-end. Our module also uses FM-AM conversion j heterodyne detection for FM-AM conversion noise noise reduction. The module's signal to noise Antenna ratio was 20 dB better than a previously Beat signal Mixer designed homodyne FM-CW radar module.

A Heterodyne Six-Port FMCW Radar Sensor Architecture Based on Beat Signal Phase Slope Techniques

“…FM-AM conversion noise is the largest noise component in a homodyne radar receiver [7]. The FM-AM conversion noise is produced by unwanted envelope components resulting from transmission line effects, mixing, and frequency response limitations of the FM modulator.…”

“…DC offset and amplitude and phase imbalance are caused by the six-port imbalance and the non-linear analog devices (diodes, transistors, etc) used for the I/Qmixer. The FM-AM conversion noise is produced by unwanted envelope components resulting from transmission line effects, mixing, and frequency response limitations of the FM modulator [7]. In fact DC offset, amplitude and phase imbalance and FM-AM conversion noise cause unacceptable measuring errors.…”

“…The heterodyne architecture reduces the FM-AM conversion noise and low frequency noise as demonstrated in [7] and [8], improving thereby the receiver sensitivity. The digital IF I/Q mixer avoid DC offset and amplitude and phase imbalance.…”

A W-Band Heterodyne FMCW Radar Based on TX IQ-Modulation

“…Thus alternative solutions have been developed allowing to generate the offset frequency in a part of the radar operating at a lower frequency where the generation of highly accurate signals is easier. An example for such an approach was published in [9], where a switch in the RX path has been used to modulate the received signal leading to an offset frequency equating to the switching frequency due to the on-off modulation. However, due to the switching operation, not only sidebands at the modulation frequency but also at multiples thereof are generated.…”

“…However, due to the switching operation, not only sidebands at the modulation frequency but also at multiples thereof are generated. Thus parts of the RX power are unused in [9]. Therefore in [6] it was proposed to use an in-phase/quadrature (IQ) modulator in the radar's TX path rather than using a switch to modulate the radio frequency (RF) signal.…”