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This work presents a D-band monostatic radar system operating from 144.6 to 161 GHz, which is placed inside a 3-D-printed low-cost case with a built-in lens to boost the antenna (ANT) directivity. The monolithic microwave integrated circuit (MMIC) is manufactured in a 130-nm BiCMOS process and includes a compact transceiver architecture consisting of an oscillator, a diode-based mixer, and an on-chip antenna. The implemented topology allows to significantly improve the signal-to-noise ratio and features a built-in self-test (BIST) structure with the possibility to provide on-chip antenna characterization using power sensors in combination with a directional coupler. Housed inside the robust printed package, the MMIC has only dc and baseband frequency connections, which offers ease of handling and poses the low-cost potential for a variety of applications. The complete transceiver chip consumes only 84.7 mA from a 3.3-V supply and its size is 1964 μm x 1448 μm. Together with the package the sensor measures a size of 42.2 mm x 42.2 mm x 45.7 mm.

Direct characterization of differential components requires multiport equipment, which is not always available. Thus, it is a common practice to attach balanced-unbalanced (balun) circuits to convert between single-ended and differential signals. However, removing impact of baluns from measured two-port S-parameters is a challenge, since baluns are three-port devices and classical de-embedding techniques are not applicable. Additionally, obtaining the S-parameters of baluns by two-port network analyzer is not trivial, since the ports at the differential side are tightly coupled. In this paper we address both challenges by proposing two techniques: how to characterize a balun using two-port measurements, and how to accurately de-embed the impact of balun characteristics from device-under-test (DUT) measurements. The applicability and accuracy of the proposed techniques is analyzed. For verification, the first technique has been applied to characterize an integrated ultrawideband (UWB) Marchand balun, and the second to de-embed the baluns impact from measured results of the balun-DUT-balun structure. The characterized DUT is a differential LNA operating in the range from 30 GHz to 110 GHz realized in 0.35 μm SiGe:C bipolar technology. The obtained de-embedded S-parameters are compared with the directly measured results.

A novel monostatic transceiver topology that makes use of a diode-based mixer and operates from 143.8 to 158.1 GHz is proposed. The architecture avoids using couplers and the associated limitations. Hence, it allows to save space and minimizes losses. The signal travels directly from the VCO to the antenna through a diode-connected npn transistor, which performs the mixing. For the transmitted signal, solely a small insertion loss of less than 1.8 dB occurs. The complete mixer circuit only consumes an area of 65 x 260 µm2. Furthermore, the transceiver concept significantly improves the signal-to-noise ratio.