On-Wafer Noise Characterization of an Automotive Monostatic Radar Transceiver With Self-Interference Evaluation

We present a novel microwave on-wafer measurement system for fast evaluation of an automotive monostatic radar transceiver. In the first development phase of a radar transceiver, building blocks and the whole transceiver have to be analyzed in detail. The setup includes a vector network analyzer (VNA) combined with 110-GHz frequency extension converters and an 85-GHz spectrum analyzer. By means of the proposed measurement system structure, switching between noise figure (NF) observation of the device under test (DUT) at microwave frequencies (e.g., for LNAs) or in the IF domain (frequency conversion devices, e.g., for mixers), can be handled by replugging of one coaxial cable. Consequently, the setup calibration can be reused after switching, which is beneficial for the setup time effort and accuracy. Applying the direct-noise method (DNM), the need for reassembly or use of a waveguide switch to connect a noise-source after on-wafer calibration is eliminated. Furthermore, the use of the VNA in combination with the DNM allows precise deembedding. Improvements achieved by the deembedding methodology proposed are demonstrated and compared with the results of Y-factor measurements. To verify DUT usability for monostatic frequency-modulated continuous-wave (FMCW) applications, the NF can be obtained in the presence of self-interference caused by TX-RX leakage (i.e., blocker signal). Reusing the VNA as a signal source for the blocker signal, this RF signal was analyzed in detail in terms of amplitude and phase noise. For the first time, the amplitude noise of the signal source is considered as well and even suppressed in the blocker measurements at the mm-wave frequency range. Amplitude noise suppression has been verified by a custom amplitude modulation (AM) circuit, which is added in the common VNA signal path and thus can be switched transparently for the remaining configurations. The proposed measurement system has been used successfully to characterize a monostatic radar transceiver for FMCW applications.