Compact Duplexing for a 680-GHz Radar Using a Waveguide Orthomode Transducer

Abstract

Abstract-A compact 680-GHz waveguide orthomode transducer (OMT) and circular horn combination has been designed, tested, and characterized in a radar transceiver's duplexer. The duplexing capability is implemented by a hybrid waveguide quasi optical solution, combining a linear polarization OMT and an external grating polarizer. Isolation between the OMT's orthogonal ports' flanges was measured with a vector network analyzer to exceed 33 dB over a >10% bandwidth between 630 and 710 GHz. Calibrated Y-factor measurements using a mixer attached to the OMT ports reveal losses through the transmit and receive paths that sum to an average of 4.7 dB of two-way loss over 660-690 GHz. This is consistent with radar sensitivity measurements comparing the new OMT/horn with a quasi-optical wire grid beam splitter. Moreover, the radar performance assessment validates the OMT as a suitable compact substitute of the wire grid for the JPL's short-range 680-GHz imaging radar.

Submillimeter‐wave waveguide filters fabricated by SU‐8 process and laser micromachining

“…(6) Inspect the produced filter on a high-resolution microscope to identify deviations of dimensions compared with nominal ones. (7) Final small operations to resolve deviations found in step (6), which ends up with the final filter.…”

“…Researchers have been pushing the limit of conventional CNC machining, with milled waveguide filters demonstrated at W-band [1, 2], WR-6 band [3] and WR-3 band [4]. Beyond this frequency, CNC machining is struggling to overcome the challenges of available cutter sizes, the wear and breakage of cutters, generation of defects/recesses and cracks due to mechanical stresses, and achievable aspect ratios [5,6]. To accommodate the fabrication of complex terahertz waveguide circuits, improvements are being made with CNC machining; an example of a purpose-built ultra-high precision CNC micromachining platform is developed and reported in [7].…”

Submillimeter-Wave Radar: Solid-State System Design and Applications

“…This is especially important if a compact one-or two-dimensional transceiver array were to be built with the diode multipliers and mixers mounted in a single monolithic split-waveguide assembly. Therefore, we designed a 680-GHz waveguide OMT to replace the wire grid, shown in Figure 6(b) [37], [38].…”

Accurate Modeling of Conductor Rough Surfaces in Waveguide Devices

“…Waveguides are a basic component in radar and communication applications [1][2][3]. The accurate modeling of electromagnetic wave propagation is an important problem, especially as majority of present and future radar and communication systems operate at higher frequencies in the millimeter-wave bands.…”

“…Using Morgan's model, Hammerstand and Bekkadal [5] derived a widely used empirical formula that matches the numerical results produced by Morgan. This formula, given in (1), provides a correction factor describing the ratio of the power absorption of a rough surface P rough to that of a corresponding smooth surface P smooth .…”