Abstract
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).
Highlights
A CHIEVING sufficient output power of the transmitted electromagnetic wave in radar systems is, besides other key characteristics such as high transmitter-receiver (TX–RX)isolation, high receiver sensitivity, or low total receiver noise factor, one of the essential attributes to reach high system dynamic range and high detection range
For the results presented in this publication, the auxiliaryVCO’s (27 GHz) frequency is phase-locked loop (PLL)-stabilized at exactly 28.8 GHz
Together with the tuning range of the 94-GHz voltage-controlled oscillator (VCO), this leads to a frequency configuration that is best suited to the frequency limitations given in the datasheet of the PLL ICs
Summary
A CHIEVING sufficient output power of the transmitted electromagnetic wave in radar systems is, besides other key characteristics such as high transmitter-receiver (TX–RX)isolation, high receiver sensitivity, or low total receiver noise factor, one of the essential attributes to reach high system dynamic range and high detection range. For high detection range in airborne applications, this work demonstrates a quasimonostatic 94-GHz FMCW radar system with one transmitter and two receivers with 14.8-dBm output power at the radar’s TX-waveguide port and over 26 GHz of phase-locked loop (PLL)-stabilized frequency modulation. On the right-hand side of the block diagram, the front-end includes the PLLs for the radar MMIC’s voltage-controlled oscillators (VCOs), the 94 GHz radar MMIC, IF-amplifiers for both receiver channels with bandpass behavior, a digital-toanalog converter (DAC) that controls the radar’s output power, and transitions for the 94-GHz signals between the MMIC and the WR-10 waveguide ports for antenna connection. In this work, the recent system concepts were improved by shrinking the MMIC die size while adding additional functionality like a second RX-channel and a PA on the MMIC, and a DAC for output power control and new passive components for low loss high-frequency signal routing between MMIC and antennas on the PCB. The position of both PLL ICs and the IF-amplifier is given by the back-end interface that was kept from previous radar systems for good interoperability
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