Microwave Applications Group (United States)

In this paper a new and simple dual-band microstrip slot antenna design combined with two inverted L-shaped slots integrated in the radiating patch is presented. This antenna is suitable for operating at 915 MHz and 2.45 GHz in order to cover the Radio Frequency Identification (RFID) frequencies bands. By optimizing the structure design, good performances in term of return loss radiation pattern and efficiency are achieved. The simulation results were obtained by using ADS and CST Microwave Studio electromagnetic solvers. The proposed antenna is mounted on an FR4 substrate with dielectric permittivity constant 4.4, thickness of 1.6 mm and loss tangent of 0.025 and a total area of 48×47 mm2. The design methodology used to achieve the dual-band antenna and both experimental, simulated results are presented.

In this paper a new dual-band uniplanar monopole antenna fed by Coplanar Waveguide (CPW) line is proposed for Radio Frequency Identification (RFID) applications. The antenna structure includes a CPW fed line and the dual-band operation is achieved from the G-shaped folded antenna. The antenna parameters have been investigated and optimized by using CST Microwave Studio. To validate the CST Microwave Studio results before the antenna achievement, we have conducted another study by using ADS. The final circuit was achieved, measured and validated. Experimental results show that the proposed antenna with compact size of 30*45 mm2 is simple in design and compact in size. It exhibits broadband impedance matching, consistent omnidirectional radiation patterns and appropriate gain characteristics suitable for the microwave RFID applicartions.

This paper describes the design approach and characteristics of an air-cooled ferrite half-wave plate operating in the vicinity of 1.3 GHz. frequency at a peak power level of 65 kW. and an average power level of 6,500 W. Measured data are presented for an engineering model unit with 0.4 dB. maximum insertion loss, capable of switching between any two states in approximately 500 microseconds.

The basic structure of microwave ferrite reciprocal phase shifters of the Dual-Mode and Rotary-Field types can readily be adapted to incorporate the function of a circulator outside the phase shifting region. The circulator effect is realized in the form of orthogonal polarization of waves in the two directions of propagation in circular or square waveguide at the input of the device. A mode-separating waveguide junction is required to resolve these orthogonal modes into two single-mode waveguides. This paper presents specific implementations of duplexing ferrite reciprocal phase shifters, comments on the factors affecting the isolation of the equivalent-circuit circulator, and discusses possible advantages in antenna system applications.

This paper is about third generation, PCS and other cellular signal profiling in a built-up area such as Melbourne CBD. The purpose of this investigation is to determine the variation of the signal strength between a transmitter, 1218-BV lockable oscillator 900-2000MHz general radio, mounted on top of a RMIT University building and a portable receiver, Protek 3201, covering the streets below the transmitter. It is divided into sectors and the points of data collection are marked in steps of 10 meter. The transmission paths between the transmitter and receiver can be varied from direct line-of-sight to those fully blocked by a tree or a building. 3G systems require site-specific propagation modeling due to the high speed signal such as video-conferencing and video streaming. They require reliable and continuous service. Signal profiting is essential for service reliability.

Unlike conventional waveguides, lossless ferrite-filled guides may exhibit a complex propagation factor below cutoff of the dominant TE mode when a transverse magnetic bias field is applied. In that case, the field in a very long waveguide has the character of a traveling wave whose amplitude decays exponentially with distance from the driven end. The wavelength and the magnitude of the applied bias field are inversely related, and at zero field as the gyromagnetic effects vanish in the ferrite the wavelength becomes infinite. For a bias field of one polarity, the traveling wave will be a forward wave, and for the opposite polarity it will be a backward wave. This peculiar behavior allows phase shift to be produced in a bandpass filter-like structure in which small cross-section below-cutoff ferrite waveguide sections alternate with sections of high dielectric constant material.

Ferrite rotary-field phase shifters have offered highly accurate reciprocal phase control for moderate to high microwave power levels, at the expense of continuous current excitation. This paper presents the concept, basic design considerations, and initial data for the first realization of a latching version that operates at remanent magnetization of the ferrite and requires excitation only during switching. Changes in configuration necessary for latching operation imply slightly larger rms phase errors and a reduced capability for average r-f power handling. Data are presented for a breadboard S-band unit, and control advantages unique to this device are discussed. >

The basic ferrite rotary-field phase shifter geometry can be adapted to perform the vector modulator functions of amplitude control as well as phase control in a closed-loop signal cancellation system. The control concept is easily described as a mapping between the sine and cosine drive currents and the insertion phase and amplitude. Adaptability is achieved by digitizing the error signal and using a microprocessor to correct angular offsets and gain compression between the current plane inputs and the rf plane outputs. In this way the closed-loop system can be made unconditionally stable, regardless of line-length differences in the sensing, reference, and error-cancelling branches. A laboratory test at X-band demonstrating 60 dB. cancellation with 30 dB. dynamic range is described. The approach is easily capable of handling hundreds of watts of peak power and several watts of average power, with a maximum amplitude output corresponding to an insertion loss on the order of one half dB. Low insertion loss plus the fact that no electron transport is involved should mean that the noise contribution of the device is very low. >

This paper reviews parameters for dual mode reciprocal phasers, which operate most effectively in the 5-25 GHz range. Items which receive attention include bandwidth, insertion loss, power handling, size and weight. Computed design relations are presented with some supporting experimental data.