Stephanie L. Smith

A beam-scanning dual-polarized fan-beam antenna suitable for Millimeter wavelengths

The design and testing of a beam-scanning pillbox antenna for use in a 200 GHz imaging system is presented. The antenna features a rotating subreflector that scans the antennas fan beam and a multimode structure that reduces ohmic loss and allows use of two orthogonal polarizations. The antenna has an aperture size of 450/spl times/5 mm, half-power beam widths of approximately 0.4/spl deg/ and 18/spl deg/ and a beam-scan range of 10/spl deg/. The gain of the antenna was measured to be greater than 33 dBi for both polarizations. The radiation patterns of the pillbox antenna have been measured in the radiating near field using an outdoor range. Good agreement between measured and calculated patterns has been obtained.

A Millimeter-Wave Antenna Amplitude and Phase Measurement System

We describe the design and application of a system for measuring the magnitude and phase of antenna radiation patterns in the 182-194 GHz frequency range. A heterodyne receiver comparing antenna and reference signals is designed from readily available components and incorporated into a 12-m anechoic chamber. The chamber is used with or without a compact-range reflector for compact-range or far-field measurement of antennas up to 0.6 m in diameter. The measured phase variation of the system, when idle, averages 0.3° over 227 s and 4.5° over 30 min. The amplitude stability is better than ±0.15 dB over a 63-h period. Verification of the system is obtained through comparison with other measurements and calculated results on horn and pillbox antennas. The applications of the system are illustrated through its use in characterizing the magnitude and phase radiation patterns of a new beam-scanning pillbox antenna for a 186-GHz imaging system.

Design Aspects of an Antenna-MMIC Interface Using a Stacked Patch at 71–86 GHz

A bond-wire-free interconnection between monolithic microwave integrated circuit (MMIC) and antenna using a stacked patch configuration is investigated. An edge-fed patch on a gallium arsenide (GaAs) MMIC chip drives a patch antenna integrated in the lid of the MMIC package. The lid is formed using a liquid crystal polymer (LCP) substrate. The first implementation using a laminated multichip module (MCM-L) process is presented that covers the designated E-band spectrum for long-range wireless communications (71–86 GHz). Electromagnetic simulations and measurements of antenna radiation patterns agree well over the whole frequency range of interest. Important design aspects and manufacturing tolerances specific for the implementation of the interface in MCM-L millimeter-wave front-ends are presented. An alternative design is proposed for improved radiation patterns across the band.

An ultra-wideband dielectrically loaded quad-ridged feed horn for radio astronomy

We present a broadband dielectrically loaded quad-ridged feed horn for illuminating reflector antennas. The feed horn combines a central dielectric spear with a corrugated skirt to achieve a near constant beam width over a 6:1 bandwidth from 0.7-4.2GHz. The feed accepts two linear polarizations which are differentially fed. We present the directivity of the feed measured in an anechoic chamber. The feed exhibits a directivity of 12dB±1.5 and a measured return loss of greater than 14dB across the frequency band.

Performance validation of the 19-element multibeam feed for the five-hundred-metre aperture spherical radio telescope

The performance of an L-band 19-element multibeam feed for the five-hundred-metre aperture spherical radio telescope is verified here. Radiation patterns have been measured in an anechoic chamber in the radiating near field of the array and compared with simulated radiation patterns from HFSS for the same conditions. Very good agreement is observed between the measurements and simulations.

Three-Shaped-Reflector Beam-Scanning Pillbox Antenna Suitable for mm Wavelengths

We describe the design and measured performance of an improved beam-scanning fan-beam antenna suitable for mm wavelengths. The fan beam is scanned in the direction orthogonal to the fan and can be polarized either in or orthogonal to this direction. The pillbox design is improved by the introduction of a third cylindrical reflector and optimum shaping of all reflector profiles using an iterative diffraction analysis that includes aberration and blockage effects. Good agreement between the calculated and measured results is obtained, confirming a beamwidth of 0.3° and a scan range of 13.5° (45 beamwidths) for both polarizations at 186 GHz.

Design and laboratory testing of the five hundred meter aperture spherical telescope (FAST) 19 beam L-band receiver

We describe a multibeam receiver for the FAST radiotelescope. The receiver provides 19 dual polarised beams over a band of 1050–1450 MHz with an expected receiver noise temperature under 7 K and aperture efficiency of greater than 62%. The feed is currently undergoing final assembly and testing.

Design of an artificial magnetic conductor surface using an evolutionary algorithm

Application of an evolutionary algorithm in designing an artificial electromagnetic conductor (AMC) at 12 GHz is explained in this paper. To do so, a binary version of particle swarm optimization algorithm in connection with EM simulation is used, resulting in an AMC with 29% fractional bandwidth at the operating frequency.

Analysis of offset Gregorian reflector with phased array feed for SKA

Selected results of the optics analysis of the proposed offset Gregorian reflector with Phased Array Feed (PAF) are presented. The approach used to analyze the phased array feed with the Gregorian reflector is described.

E-band aperture coupled GaAs / LCP antennas

An E-band aperture coupled patch antenna using a combination of GaAs and liquid crystal polymer (LCP) substrates packaged with a laminated multi-chip module (MCM-L) process is presented in this paper. The antenna offers an electromagnetic interface between a GaAs MMIC and a separate dielectric antenna package. Design, manufacture, packaging and test results of the proposed antenna are presented. Measurement of a waveguide to microstrip transition used in the testing of the antenna is presented with excellent performance obtained across the E-band. Further analysis of the packaging method is required to assess the unpredicted loss observed in the measurements.