3D Micromachined Passive Components and Active Circuit Integration for Millimeter-wave Radar Applications

The development of millimeter-wave (30-300 GHz) sensors and communications systems has a long history of interest, spanning back almost six decades. In particular, mm-wave radars have applications as automotive radars, in remote atmospheric sensing applications, as landing radars for air and spacecraft, and for high precision imaging applications. Mm-wave radar systems have high angular accuracy and range resolution, and, while susceptible to atmospheric attenuation, are less susceptible to optically opaque conditions, such as smoke or dust. This dissertation document will present the initial steps towards a new approach to the creation of a mm-wave radar system at 94 GHz.

Specifically, this dissertation presents the design, fabrication and testing of various components of a highly integrated mm-wave a 94 Ghz monopulse radar transmitter/receiver. Several architectural approaches are considered, including passive and active implementations of RF monopulse comparator networks. These architectures are enabled by a high-performance three-dimensional rectangular coaxial microwave transmission line technology known as PolyStrataTM as well as silicon-based IC technologies. A number of specific components are examined in detail, including: a 2x2 PolyStrata antenna array, a passive monopulse comparator network, a 94 GHz SiGe two-port active comparator MMIC, a 24 GHz RF-CMOS 4-port active monopulse comparator IC, and a series of V- and W-band corporate combining structures for use in transmitter power combining applications.

The 94 GHz cavity-backed antennas based on a rectangular coaxial feeding network have been designed, fabricated, and tested. 13 dB gain for a 2 x 2 array, as well as antenna patterns are reported. In an effort to facilitate high-accuracy measurement of the antenna array, an E-probe transition to waveguide and PolyStrata diode detectors were also designed and fabricated. AW-band rectangular coaxial passive monopulse comparator with integrated antenna array and diode detectors have also been presented. Measured monopulse nulls of 31.4 dB in the ΔAZ plane have been demonstrated. 94-GHz SiGe active monopulse comparator IC and 24 GHz RF-CMOS active monopulse comparator RFIC designs are presented, including detailed simulations of monopulse nulls and performance over frequency. Simulations of the W-band SiGe active monopulse comparator IC indicate potential for wideband operation, with 30 dB monopulse nulls from 75-105 GHz. For the 24-GHz active monopulse comparator IC, simulated monopulse nulls of 71 dB and 68 dB were reported for the azimuthal and elevational sweeps. Measurements of these ICs were unsuccessful due to layout errors and incomplete accounting for parasitics.

Simulated results from a series of rectangular coaxial power corporate power combining structures have been presented, and their relative merits discussed. These designs include 2-1 and 4-1 reactive, Wilkinson, and Gysel combiners at V- and W-band. Measured back-to-back results from Gysel combiners at 60 GHz included insertion loss of 0.13 dB per division for a 2-1 combination, and an insertion loss of 0.3 dB and 0.14 dB for "planar" and "direct" 4-1 combinations, respectively. At 94 GHz, a measured insertion loss of 0.1 dB per division has been presented for a 2-1 Gysel combination, using a back-to-back structure. Preliminary designs for a solid-state power amplifier (SSPA) structure have also been presented. Finally, two conceptual monopulse transceivers will be presented, as a vehicle for integrating the various components demonstrated in this dissertation.