IEE Journal on Microwaves, Optics and Acoustics
Volume 1, Issue 5, September 1977
Volume 1, Issue 5
September 1977
Design of receiving stations for satellite-to-ground propagation research at frequencies above 10 GHz
- Author(s): J.E. Allnutt and J.E. Goodyer
- Source: IEE Journal on Microwaves, Optics and Acoustics, Volume 1, Issue 5, p. 157 –164
- DOI: 10.1049/ij-moa.1977.0020
- Type: Article
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Tropospheric effects relevant to satellite communication at frequencies above 10 GHz can be investigated with passive radiometers, radars, and by monitoring transmissions from geostationary satellites. By using satellite beacons, it is possible to measure phase coherence over large bandwidths and crosspolarisation discrimination, as well as single-site and space-diversity attenuation characteristics. In designing a receiver for a propagation experiment, the satellite/earth-station system must be investigated as a whole to optimise the characteristics of the receiver. The paper sets out a design approach for a low-cost earth-station receiver for automatic operation and then details the receivers built at the Appleton Laboratory for the SIRIO and ATS-6 satellite-to-ground radio-propagation experiments.
Microstrip antennas and arrays. Part 1: Fundamental action and limitations
- Author(s): J.R. James and G.J. Wilson
- Source: IEE Journal on Microwaves, Optics and Acoustics, Volume 1, Issue 5, p. 165 –174
- DOI: 10.1049/ij-moa.1977.0021
- Type: Article
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Consideration of the radiation mechanism of an open-circuit microstrip termination indicates that the terminal-plane region is the dominant radiating aperture. On this basis, the radiation patterns of several types of microstrip radiating elements in rectangular and cylindrical geometry are calculated and substantiated by experiment. In general, the patterns exhibit the characteristics of slot radiators, thus endorsing the action of an end-radiating aperture; the radiation admittance of the latter is obtained by novel measurements of the standing waves in a truncated microstrip line but, when the substrate extends beyond the radiating aperture, substrate surface waves are generated. An analysis of the substrate waves indicates that the side-lobe level of an array of microstrip radiating elements could be limited to around –20 dB, and severe unwanted coupling effects between microstrip circuits are also noted. The use of substrate troughs to reduce the surface-wave generation is discussed, and a strip width-modulation technique proposed to control the array aperture distribution and simplify the feeding configuration. The implications of these present findings on the potential performance of microstrip antenna arrays is discussed and design recommendations made; the latter are investigated in a companion paper.
Microstrip antennas and arrays. Part 2: New array-design technique
- Author(s): J.R. James and P.S. Hall
- Source: IEE Journal on Microwaves, Optics and Acoustics, Volume 1, Issue 5, p. 175 –181
- DOI: 10.1049/ij-moa.1977.0022
- Type: Article
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Open-circuit terminations on half-wavelength stubs form the radiating elements in a new design technique for linear microstrip microwave arrays. Measured results, on computer-designed resonant and wideband travelling-wave arrays with broadisde beams, demonstrate the technique; the effects of corporate feeds and radomes are also considered. The computer design of medium gain arrays, with H-plane sidelobe levels below about –21 dB, demands characterisation of the microstrip T-junction with an accuracy that is currently unavailabe, and the dimensional precision has to be obtained by experimental means. It is concluded, to date, that the known extraneous sources of radiation do not inhibit the control of H-plane sidelobes to a level of at least –25 dB and the new design technique makes microstrip arrays highly competitive with their conventional waveguide counterparts.
Transmission-line matrix analysis of continuous waveguiding structures using stepped-impedance cavities
- Author(s): John E. Sitch and Peter B. Johns
- Source: IEE Journal on Microwaves, Optics and Acoustics, Volume 1, Issue 5, p. 181 –184
- DOI: 10.1049/ij-moa.1977.0023
- Type: Article
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Up to the present time, the t.l.m. method of numerical analysis has found the dispersion characteristics of continuous waveguiding structures by obtaining the resonant frequencies of quarter wavelength cavities. Long cavities requring many nodes have been necessary, and the computer power required for solution becomes excessive as the frequency of interest decreases. This paper shows how cavities of any length may be represented by stepped impedance cavities which, for the t.l.m. method, are only two mesh lengths long for 2-dimensional analysis and 2.5 mesh lengths long for 3-dimensional analysis. The savings in computer time and storage, using the stepped impedance technique, may be of the order of 100 times.
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