A Mixed-Mode Beamforming Radar Transmitter MMIC Utilizing Novel Ultrawideband IQ-Generation Techniques in SiGe BiCMOS
Wireless systems like radar and communication systems evolved progressively into multichannel systems over the past years. The most common multichannel concepts are multiple-input multiple-output (MIMO) and phased array architectures. In this paper, we present a transmitter monolithic microwave integrated circuit (MMIC) in a SiGe BiCMOS technology for its application, a mixed-mode frequency modulated continuous wave radar that is able to operate in both ways, in an MIMO and a beamforming mode. The MIMO mode is used for medium range and fast 3-D scans and the phased array mode is used for beamforming. This mode increases the effective output power of the transmitted signal beam and thus system dynamic and detection range. For this purpose, we developed ultrawideband quadrature (IQ) generation techniques to generate synchronous IQ-signals in each channel of our system to feed a vector adder, which is capable of shifting the phase for beamforming. The developed IQ-generation circuits are able to operate from 1 to 30 GHz, and the complete radar transmitter MMIC, including a power amplifier (PA), operates from 11 to 20 GHz. The IQ-generation phase error in this frequency range is below 6° and below 9°/3.2°rms for the IQ-generation together with vector modulator. The power consumption is 285 mW and the PA consumes 1.25 W with a maximum output power of the complete multimode TX MMIC of 24.4 dBm at 15 GHz.