This article presents a frequency-modulated continuous wave (FMCW) harmonic radar in the 61-/122-GHz industrial, scientific, and medical (ISM) frequency bands. The radar is based on two self-designed monolithic microwave wave integrated circuits (MMICs) for the transceiver (TRX) and tag which are fabricated in a 130-nm SiGe BiCMOS technology. The presented TRX-MMIC consists of a fundamental voltagecontrolled oscillator (VCO), a power amplifier (PA), Wilkinson power dividers, and a static divide-by-16 chain for stabilization within a phase-locked loop (PLL) in the transmitter (TX) part. The receiver (RX) part has two channels with a low noise amplifier (LNA), a Gilbert cell mixer, and an intermediate frequency (IF)-amplifier each. The fundamental of the VCO is converted by a frequency doubler and distributed to the local oscillator (LO) input of the RX-mixers. With such a TRX architecture the active nonlinear tag which consists of antennas, pre-amplifiers, and a frequency doubler can be detected. For a sweep from 60 to 64 GHz, a spatial resolution of 4 cm at 1-m distance and a range of 23.3 m is achieved. With these characteristics, the tag enables harmonic radar applications in the millimeter-wave (mm-wave) range for medium range with high accuracy and resolution with a small form factor.
Airborne applications demand exceptional overall radar system performance and eminently high output power for high range target detection. The frequency modulated continuous wave (FMCW) radar system presented in this article is capable of achieving this task due to its high output power at 94-GHz center frequency with over 26-GHz tuning range. Nevertheless, the radar still provides a small form factor and low power consumption of 4.25 W at 5 V single Universal Serial Bus (USB) supply. The key system component is a Silicon Germanium (SiGe) bipolar complementary metal-oxide-semiconductor (BiCMOS) monolithic microwave integrated circuit (MMIC) that contains a 94-GHz voltage-controlled oscillator (VCO), and a 27-GHz VCO for dual-loop phase-locked loop (PLL) stabilization, a power amplifier (PA), and two receive mixers. It generates frequency ramps between 83-and 109-GHz with a maximum output power of 19.7 dBm at its output after the bond wires on the printed circuit board (PCB) and 14.8-dBm output power at the radar's transmit (TX)-waveguide WR-10-flange. The sensor was also tested in a temperature range from −40 • C to +70 • C with menial deviation. Thus, the system offers high system dynamic range and far distance target detection range. Following a detailed system description, we finally present the FMCW range and Doppler measurements performed with the presented radar sensor as well as the application on unmanned aerial vehicles (UAVs) for flight altitude control and as airborne collision avoidance system (ACAS).
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