IEE Journal on Microwaves, Optics and Acoustics
Volume 3, Issue 3, May 1979
Volume 3, Issue 3
May 1979
Propagation studies on a line-of-sight microwave link at 36 GHz and 110 GHz
- Author(s): K.L. Ho ; N.D. Mavrokoukoulakis ; R.S. Cole
- Source: IEE Journal on Microwaves, Optics and Acoustics, Volume 3, Issue 3, p. 93 –98
- DOI: 10.1049/ij-moa.1979.0022
- Type: Article
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93
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Experimental results obtained on two line-of-sight links at 36 GHz and 110 GHz operating over a period of more than two years across central London are summarised. Scintillation measurements on the two links show that the experimental results are in good agreement with the theoretical predictions of Tatarski. Additional scintillation information on millimetre-wave propagation in a town environment, attenuation due to rainfall and fog, and long-term statistics are also presented.
More accurate model of the coupled microstripline section
- Author(s): B. Easter and C. Gupta
- Source: IEE Journal on Microwaves, Optics and Acoustics, Volume 3, Issue 3, p. 99 –103
- DOI: 10.1049/ij-moa.1979.0023
- Type: Article
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99
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A parallel coupled microstripline bandpass filter was designed to operate at a frequency of 10 GHz with a 10% bandwidth. The theoretical transmission-loss response was predicted for a coupled microstripline section using a more accurate model. A discrepancy of about 2% remained between the predicted and the measured centre frequencies of the filter. This was partly attributed to the possible influence of nonadjacent resonators which were not included in the model. Further evidence of the presence of such a couplig phenomenon between nonadjacent resonators was demonstrated experimentally.
Conversion factors for the power radiated by a small slot in loaded rectangular waveguide
- Author(s): A.J. Sangster
- Source: IEE Journal on Microwaves, Optics and Acoustics, Volume 3, Issue 3, p. 104 –108
- DOI: 10.1049/ij-moa.1979.0024
- Type: Article
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p.
104
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The radiation characteristics of slot radiators in uniform rectangular waveguide have been extensively documented, both theoretically and experimentally. However, to avoid grating lobes, or to accommodate frequency scanning, in slotted waveguide arrays, the waveguide used is often partially filled with a periodic structure, or with dielectric, to reduce the guide wavelength. This communication describes conversion factors which have been generated to permit the radiation strengths of nonresonant slots, in such waveguides, to be estimated from known results for uniform empty waveguides.
Simulation of the near field of single-mode fibres by means of a microwave model
- Author(s): J. Albrecht and E.-G. Neumann
- Source: IEE Journal on Microwaves, Optics and Acoustics, Volume 3, Issue 3, p. 109 –114
- DOI: 10.1049/ij-moa.1979.0025
- Type: Article
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109
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In order to verify the agreement of the conventionally used approximations for the field equations of the fundamental mode of a fibre and to study the near field in the vicinity of a discontinuity, a microwave model of a single-mode fibre is designed and constructed. At this waveguide, which works at frequencies of about 10 GHz, the field distribution can be measured with a small microwave probe. Using a semi-automatic level- and wavefront-recorder the field pattern of the radiating fibre end, as well as that in the vicinity of a gap, a displacement or an angle, is plotted and discussed.
Design and performance of microwave oscillators in integrated fin-line technique
- Author(s): Reinhard Knöchel
- Source: IEE Journal on Microwaves, Optics and Acoustics, Volume 3, Issue 3, p. 115 –120
- DOI: 10.1049/ij-moa.1979.0026
- Type: Article
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115
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Guidelines are outlined for the design of oscillators for various applications, which are realised in integrated fin-line technique. The characteristic features are derived and compared to one another. The results are then applied to cavity-stabilised oscillators, injection-locked amplifiers, and varactor-tuned oscillators, which have all been realised in fin-line technique. Stabilisation by an integrated transmission cavity is shown to be the best configuration for fin-line. For injection-locked amplifiers the stable locking range has been considerably improved by reactance compensation. Finally, it is shown how a varactor diode should be integrated in order to achieve wideband electronic tunability. Performance data of realised (Gunn or Impatt) oscillators are given for each case of application.
Design technique for broadband microwave transistor power amplifiers
- Author(s): K.L. Kotzebue and E.R. Ehlers
- Source: IEE Journal on Microwaves, Optics and Acoustics, Volume 3, Issue 3, p. 121 –127
- DOI: 10.1049/ij-moa.1979.0027
- Type: Article
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121
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A technique for the design of broadband microwave transistor power amplifiers is presented that utilises the powerful methods of network synthesis to achieve optimum large-signal performance. Only two large-signal transistor measurements per frequency are required to achieve a good analytic model of the transistor's variation of added power with load impedance, and a mapping function is presented that translates this added-power characteristic into an equivalent linear-circuit reflection-coefficient characteristic. With this representation, methods of linear-network synthesis are used to obtain circuits which optimise the amplifier's added-power efficiency over a broad range of frequencies. The design technique has been experimentally verified by the characterisation, design and construction of a b.j.t. amplifier of near-octave bandwidth centred at 1 GHz, with the large-signal performance in good agreement with that predicted by the design theory.
Model for s.a.w. scattering by i.d.t. and its application to s.a.w. track changer
- Author(s): P. Sudhakar and A.B. Bhattacharyya
- Source: IEE Journal on Microwaves, Optics and Acoustics, Volume 3, Issue 3, p. 128 –132
- DOI: 10.1049/ij-moa.1979.0028
- Type: Article
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128
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A superposition model for surface-acoustic-wave (s.a.w.) scattering by an interdigital transducer (i.d.t.) has been developed. In essence, it consists of two steps, (a) The incident s.a.w. induces a voltage across the i.d.t. (b) The bidirectionally radiated s.a.w., due to this induced voltage, is superposed with the incident s.a.w. to yield the scattered s.a.w. field. It is shown to considerably simplify the s.a.w. scattering parameter calculations for i.d.t. The results agree with earlier observations. Scattering parameter calculations of nonuniformly illuminated, resonantly loaded hybrid-junction i.d.t.s (r.l.h.i.d.t.) show that (i) s.a.w.s are unidirectionally radiated over the unilluminated part of the h.i.d.t. and (ii) it is described by a (track-changing) transfer function of bandpass type, with flat bandwidths up to 20% of nearly 0 dB loss, under appropriate conditions. The r.l.h.i.d.t. track changer should, therefore, be useful in realising long delay lines. The attractive feature of the r.l.h.i.d.t. as an s.a.w. track changer is that its implementation is practically feasible even on a low piezoelectric-coupling substrate like ST quartz. However, its main disadvantages are the requirement of (a) multilevel high-resolution lithography and (b) the additional high-Q tuning inductors for resonant loading.
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