Gildas P. Gauthier

Off-axis properties of silicon and quartz dielectric lens antennas

The theoretical far-field patterns and Gaussian-beam coupling efficiencies are investigated for a double-slot antenna placed off aids on extended hemispherical silicon and quartz lenses. Measured off-axis radiation patterns at 250 GHz agree well with the theory. Results are presented that show important parameters versus off-axis displacement: scan angle, directivity, Gaussicity, and reflection loss. Directivity contour plots are also presented and show that near-diffraction limited performance can be achieved at off-axis positions at nonelliptical extension lengths. Some design rules are discussed for imaging arrays on dielectric lens antennas.

Microstrip antennas on synthesized low dielectric-constant substrates

Micromachining techniques using closely spaced holes have been used underneath a microstrip antenna on a high dielectric-constant substrate (/spl epsiv//sub r/=10.8) to synthesize a localized low dielectric-constant environment (/spl epsiv//sub r/=2.3). The measured radiation efficiency of a microstrip antenna on a micromachined 635-/spl mu/m thick /spl epsiv//sub r/=10.8 Duroid 6010 substrate increased from 48/spl plusmn/3% to 73/spl plusmn/3% at 12.8-13.0 GHz (including 3.3-cm feed line losses). We believe that this technique can be applied to millimeter-wave antennas (microstrip, dipoles, slots, etc.) on silicon and GaAs substrates to result in relatively wideband (3-6%) monolithic microwave integrated circuits (MMIC) active antenna modules for phased-arrays and collision-avoidance systems.

A 94-GHz aperture-coupled micromachined microstrip antenna

This paper presents an aperture-coupled micromachined microstrip antenna operating at 94 GHz. The design consists of two stacked silicon substrates: (1) the top substrate, which carries the microstrip antenna, is micromachined to improve the radiation performance of the antenna and (2) the bottom substrate, which carries the microstrip feed line and the coupling slot. The measured return loss is -18 dB at 94 GHz for a 10-dB bandwidth of 10%. A maximum efficiency of 58/spl plusmn/5% has been measured and the radiation patterns show a measured front-to-back ratio of -10 dB at 94 GHz. The measured mutual coupling is below -20 dB in both E- and H-plane directions due to the integration of small 50-/spl mu/m silicon beams between the antennas. The micromachined microstrip antenna is an efficient solution to the vertical integration of antenna arrays at millimeter-wave frequencies.

Mode conversion at GCPW-to-microstrip-line transitions

Mode conversion at the transition between grounded coplanar waveguide (GCPW) and microstrip line is demonstrated. Experimental results show the effect of overmoding in a conductor-backed coplanar waveguide on the transition behavior. A simple micromachining solution is used to cancel the parasitic modes triggered by the transition in the GCPW feed line. This results in an insertion loss of 0.3 dB and a return loss better than -18 dB from 75 to 110 GHz. The transition can prove very useful for millimeter-wave packaging and interconnects.

W-Band finite ground coplanar waveguide (FGGPW) to microstrip line transition

fA uniplanar transition from finite ground coplanar waveguide (FGCPW) to microstrip line operating at W-Band has been developed. The design is uniplanar and does not require viaholes or wirebonds. The transition, centered at 94 GHz, results in 0.2 dB insertion loss with a bandwidth of 20%. The return loss is better than -17 dB from 85 GHz to 100 GHz. To our knowledge, this simple transition shows state-of-the-art performance, and can be very useful for CPW-probe to microstrip circuit measurements.

A uniplanar 90-GHz Schottky-diode millimeter-wave receiver

A 90 GHz Schottky-diode receiver based on a double slot antenna fed by a coplanar-waveguide (CPW) transmission line is presented. The double slot antenna is placed on an extended hemispherical high-resistivity silicon substrate lens. The uniplanar receiver results in a 9.3/spl plusmn/0.3 dB measured SSB conversion loss at 88-90 GHz including antenna and IF circuit losses and a 1-dB loss due to the use of a nonoptimal matching cap layer at the silicon lens-air interface. The calculated conversion loss agrees very well with the RF measurements. The uniplanar double-slot antenna receiver is very small, less than 1.1/spl times/4 mm including the RF/IF filter, and is compatible with monolithic two- and three-terminal devices on GaAs substrates. The application areas are in millimeter-wave receivers for automotive systems, communication systems, and radiometric linear imaging arrays. >

A 94 GHz aperture-coupled micromachined microstrip antenna

In this paper, we present an aperture-coupled micromachined microstrip antenna operating at 94 GHz. The design consists of two stacked silicon substrates: (1) the top substrate, which carries the microstrip antenna, is micromachined to improve the radiation performance of the antenna, and (2) the bottom substrate, which carries the microstrip feed line and the coupling slot. The measured return loss is -17 dB at 91 GHz for a 10-dB bandwidth of 11%. The radiation patterns show a measured front-to-back ratio of -10 dB at 91 GHz. The micromachined microstrip antenna is an efficient solution to the vertical integration of antenna arrays at millimeter-wave frequencies.

W-band single-layer vertical transitions

Vertical single-layer transitions operating at W-band frequencies have been developed. The designs are uniplanar, use electromagnetic coupling, and do not require via holes or air bridges. The first transition uses coplanar-waveguide-mode coupling and results in an insertion loss of better than 0.6 dB over the whole band, with a loss of 0.25 dB from 85 to 110 GHz. The return loss is better than -10 dB from 75 to 110 GHz. The second transition uses microstrip-mode coupling and results in a 0.2-dB insertion loss over the whole W-band. These transitions can prove very useful for millimeter-wave packaging and vertical interconnects.

A 90-100 GHz double-folded slot antenna

A double-folded slot antenna (DFS) has been designed, fabricated, and tested at 90-100 GHz. The antenna shows a very wideband impedance around 20 /spl Omega/ from 85 to 110 GHz. The low impedance is compatible with superconductor-insulator-superconductor (SIS) junctions, Schottky diodes or high electron mobility transistor (HEMT) amplifiers, which require a low impedance at millimeter wave frequencies. The antenna is placed on a dielectric lens to synthesize a semi-infinite substrate and realize high-directivity patterns. The measured radiation patterns agree very well with theoretical calculations and demonstrate symmetric main beams and sidelobe levels below -15 db over a 10% bandwidth. The double folded slot antenna is an attractive candidate for low-cost wideband millimeter-wave monolithic microwave integrated circuits (MMIC) front ends.

A 140-170-GHz low-noise uniplanar subharmonic Schottky receiver

A 150-GHz Schottky diode subharmonic receiver based on a coplanar-waveguide-fed double-folded-slot (DFS) antenna is presented in this paper. The DFS antenna is placed on an extended hemispherical high-resistivity silicon substrate lens to achieve a high directivity and a high coupling to a Gaussian beam efficiency. The uniplanar receiver results in a 12±0.5-dB measured double-sideband conversion loss at 144-152 GHz for a 8-10 mW local-oscillator power at 77 GHz, and has a wide-hand l13-dB conversion loss over 30 GHz of bandwidth (140-170 GHz). The measured conversion loss includes silicon lens absorption and reflection losses, as well as IF mismatch losses. The applications are in new small aperture (7.5-cm lenses) collision-avoidance radars at 150 GHz.