Richard Q. Lee

A broad-band U-slot rectangular patch antenna on a microwave substrate

A broad-band U-slot rectangular patch antenna printed on a microwave substrate is investigated. The dielectric constant of the substrate is 2.33. The antenna is fed by a coaxial probe. The characteristics of the U-slot patch antenna are analyzed by the finite-difference time-domain (FDTD) method. Experimental results for the input impedance and radiation patterns are obtained and compared with numerical results. The maximum impedance bandwidth achieved is 27%, centered around 3.1 GHz, with good pattern characteristics.

Experimental study of the two-layer electromagnetically coupled rectangular patch antenna

Experimental results on the characteristics of two-layer electromagnetically coupled rectangular patch antennas are presented. In addition to the relatively large bandwidth region that occurs when the separation between the two layers is less than 0.15 wavelength, a high-gain region is found when the separation exceeds 0.3 wavelength. The relative sizes of the parasitic and fed patches are found to have significant effects on the resonant input resistance and bandwidth. >

On-wafer characterization of millimeter-wave antennas for wireless applications

This paper demonstrates a deembedding technique and a direct on-substrate measurement technique for fast and inexpensive characterization of miniature antennas for wireless applications at millimeter-wave frequencies. The technique is demonstrated by measurements on a tapered slot antenna (TSA). The measured results at Ka-band frequencies include input impedance, mutual coupling between two TSAs, and absolute gain of TSA.

Coplanar-waveguide aperture-coupled microstrip patch antenna

The performance characteristics of a coplanar waveguide (CPW) aperture-coupled microstrip patch antenna were investigated experimentally. A grounded CPW with a series gap in the center strip conductor was used to couple microwave power to the antenna through an aperture in the common ground plane. Results indicate good coupling efficiency and confirm the feasibility of this feeding technique.<<ETX>>

Integrated uniplanar transition for linearly tapered slot antenna

This paper presents the design, fabrication, and numerical modeling of two new uniplanar microstrip-to-coplanar strip (CPS) line transitions and a new variant of the linearly tapered slot antenna (LTSA). This new variant with an integrated uniplanar microstrip-to-coplanar strip line feed is called a V-LTSA. The advantages of these transitions in packaging and monolithic microwave integrated circuits (MMIC) integration are listed. The two transitions and the feed are modeled using finite difference time domain (FDTD) method. The overall agreement between the measured and modeled return-loss and insertion-loss characteristics of two back-to-back transitions is good. The resonance frequencies predicted by the FDTD method are within a few percentage points of the measurements. Furthermore, the V-LTSA with the feed is experimentally shown to have a wide return loss (/spl les/-10 dB) bandwidth, good radiation patterns, and low cross-polarization. The gain of the V-LTSA is 9 dB at the design frequency of 10 GHz. A proof-of-concept package to house the feed is experimentally evaluated and shown to have negligible effect on the antenna characteristics. This type of antenna readily integrates with MMIC packages in an array having a brick architecture. The V-LTSA has potential applications in phased arrays. >

Non-planar linearly tapered slot antennas with balanced microstrip feed

A nonplanar linearly tapered slot antenna (LTSA) has been fabricated and tested at frequencies from 8 to 32 GHz. The LTSA is excited by a broadband balanced microstrip transformer. An LTSA fed with this feed network exhibits very broad bandwidth extending from X-band to Ka-band with good impedance match and excellent radiation patterns.<<ETX>>

Bandwidth enhancement of dielectric resonator antennas

An experimental investigation of bandwidth enhancement of dielectric resonator antennas (DRAs) using parasitic elements is reported. Substantial bandwidth enhancement for the HE/sub 11/spl delta// mode of the stacked geometry and for the HE/sub 13/spl delta// mode of the coplanar collinear geometry has been demonstrated. Excellent radiation patterns for the HE/sub 11/spl delta// mode were also recorded. Because of excellent return loss and radiation characteristics, the DRA should be excited in HE/sub 11/ mode when used as radiating elements in an array.<<ETX>>

RF MEMS phase shifters and their application in phase array antennas

Electronically scanned arrays are required for space based radars that are capable of tracking multiple robots, rovers, or other assets simultaneously and for beam-hopping communication systems between the various assets. ^Traditionally, these phased array antennas used GaAs Monolithic Microwave Integrated Circuit (MMIC) phase shifters, power amplifiers, and low noise amplifiers to amplify and steer the beam, but the development of RF MEMS switches over the past ten years has enabled system designers to consider replacing the GaAs MMIC phase shifters with RF Micro-Electro Mechanical System (MEMS) phase shifters. In this paper, the implication of replacing the relatively high loss GaAs MMICs with low loss MEMS phase shifters is investigated.

Multi-beam discrete lens arrays with amplitude-controlled steering

This paper presents a multi-beam antenna array with amplitude-controlled continuous beam steering of each beam. The principle is demonstrated on a Ka-band full-duplex dual-polarized array with an uplink frequency of 24.7GHz and a down-link frequency of 26.7GHz. The array is designed as a discrete lens, and the antenna elements are dual-frequency patches integrated in a 5-layer structure with delay lines that enable multiple beams. The array is spatially fed with a feed corresponding to each beam. Amplitude control at the feed results in continuous beam steering. Theoretical and experimental results for the multi-beam patterns and the beam steering are presented.

Effects of parasitic patch sizes on multi-layer electromagnetically coupled patch antenna

It is found experimentally that reducing the size of the parasitic patch can significantly change the resonant frequency, resonant input impedance, and bandwidth of the two-layer and three-layer EMCP (electromagnetically coupled patch) antennas. For antennas operating in the broadband region, the bandwidth is maximum when the parasitic and the fed patches are approximately equal in size. For antennas operating in the high-gain region, the bandwidth is maximum when both dimensions of the parasitic patch are reduced by 0.35 cm.<<ETX>>