Stephen V. Robertson

Electrooptic mapping of near-field distributions in integrated microwave circuits

A field mapping system based on external electrooptic sampling has been developed in order to determine the vectorial components of the electric near-field distribution within microwave integrated circuits. The capabilities of the setup are demonstrated by two-dimensional measurements of normal and tangential fields in a coplanar microwave distribution network at frequencies up to 15 GHz. Results obtained on a functioning power-distribution network, as well as on two nonfunctioning networks, show the ability of the technique to interrogate internal circuit operation and to isolate faults through investigation of the field distributions.

Micromachined self-packaged W-band bandpass filters

Experimental and theoretical results are presented for membrane supported W-band bandpass filters which utilize silicon micromachining technology to create self-packaged, shielded circuits. A coupled line shielded microstrip implementation of a 5-element 0.5 dB equal ripple Chebyshev filter achieves a minimum insertion loss of 3.4 dB with a 6.1% bandwidth centered at 94.7 GHz. The measured filter performance shows very sharp cutoff with out of band attenuation better than 25 dB and input return loss better than 8 dB. Results are also presented for a 5-element filter that achieves a minimum insertion loss of 2.2 dB with an 11.3% bandwidth centered at 94.7 GHz, and a 3-element filter with 1.3 dB insertion loss and 16.4% bandwidth at 94.9 GHz. Efforts to model filter performance using commercially available software and FDTD techniques are discussed.<<ETX>>

A 10-60-GHz micromachined directional coupler

A 20-dB directional coupler has been designed and fabricated on a thin dielectric membrane using micromachining techniques. The fabrication process is compatible with monolithic microwave integrated-circuit (MMIC) techniques, and the coupler can be integrated into a planar-circuit layout. Design of the asymmetric tapered coupled-line coupler relies on simple quasi-static models and ideal transmission-line theory. The use of membrane technology results in less than 0.5-dB insertion loss in the coupler from 10 to 60 GHz. In addition, a micromachined packaging technique creates a shielded circuit, which is extremely compact and lightweight.

Three-dimensional high-frequency distribution networks. I. Optimization of CPW discontinuities

This paper describes a systematic study of coplanar waveguide discontinuities that are requisite components of high-frequency distribution networks. The specific geometries addressed are air bridges, right-angle bends, tee junctions, and Wilkinson dividers. Relative to typical monolithic-microwave integrated-circuit designs, the components studied herein are electrically large in order to minimize signal attenuation. The large size leads to pronounced parasitic effects, and the emphasis of this study was to optimize the electrical performance using simple compensation techniques. The optimization methods are developed using full-wave simulation and equivalent-circuit modeling, and are verified experimentally up to 60 GHz. Part II of this paper describes the implementation and packaging of the components to realize a three-dimensional W-band distribution network.

A folded slot antenna for planar quasi-optical mixer applications

The simple uniplanar quasi-optical mixer uses the effect of orthogonal modes in the folded slot antenna fed by slotline and coplanar waveguide on opposite sides. The input impedance of the antenna is analyzed with the space domain integral equation technique. Experiments at 11 GHz have demonstrated antenna and mixer operation. The antenna shows reasonable radiating properties. By taking advantage of even and odd modes in the antenna, balanced mixing can be achieved with good conversion loss.<<ETX>>

W-band finite ground coplanar (FGC) line circuit elements

This paper describes the modeling and experimental evaluation of Finite Ground Coplanar (FGC) lines, stubs, and filters between 2 and 110 GHz. These lines provide a very low loss alternative to microstrip or coplanar waveguide for millimeter- and submillimeter-wave applications without the use of vias. Their mode free operation allows excellent agreement between measured data and LIBRA modeling to 110 GHz. The lines have very low loss at W-band and filters have a loss comparable with the best membrane filters reported recently. The paper includes details of analytic and FDTD investigations of the lines, a description of the fabrication and measurement calibration and measured data on lines, tuning stubs, and a variety of low-pass filters.

Three-dimensional high-frequency distribution networks. II. Packaging and integration

This paper describes the implementation and packaging of the components, described in Part I of this paper, to realize a three-dimensional W-band distribution network.

A planar quasi-optical mixer using a folded-slot antenna

A quasioptical mixer using only planar structures such as coplanar-waveguide and slotline is presented. The mixer, which can be scaled for millimeter-wave applications and placed on a substrate lens, uses orthogonal modes in a folded-slot antenna to achieve intrinsic RF/LO isolation without BF filtering or subharmonic pumping. The folded-slot balanced mixer was fabricated on RT/Duriod and obtained a minimum isotropic conversion loss of 1.2 dB at 11.6 GHz. Numerical integration of full two-dimensional antenna patterns yielded an antenna directivity of 7 dB, corresponding to a single side-band (SSB) mixer conversion loss of 8.2 dB. The mixer demonstrated -18 dB RF/IF isolation and -30 dB LO/IF isolation. >

W-band microshield low-pass filters

Experimental and theoretical results are presented for a planar W-Band low-pass filter. A stepped impedance implementation of a 7-section 0.5 dB equal ripple Chebyshev filter achieves an insertion loss of 1 dB in the passband and a 90 GHz cutoff frequency. The filter is fabricated in microshield line technology, a new type of planar transmission line based on coplanar waveguide supported by a thin dielectric membrane. The inadequacy of conventional quasi-static models is discussed, and a Finite-Difference Time-Domain (FDTD) analysis is applied to predict the filter performance.<<ETX>>

W-Band Micromachined Vertical Interconnection for Three-Dimensional Microwave ICs

A novel vertical interconnection utilizing finite ground coplanar waveguide (FGCPW) and silicon micromachining has been developed for W-band The measured results indicate insertion loss of only 0.6 dB. This transition uses standard processing techniques and is a compact, 520 ¿m width and 520 ¿m length, design. With this vertical interconnect, multiple IC layers may be connected to achieve new levels of high density, low loss integration.