Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 8, Issue 14, 13 July 1972
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Volume 8, Issue 14
13 July 1972
Pyroelectric properties of lead germanate
- Author(s): G.R. Jones ; N. Shaw ; A.W. Vere
- Source: Electronics Letters, Volume 8, Issue 14, p. 345 –346
- DOI: 10.1049/el:19720252
- Type: Article
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p.
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–346
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An evaluation of the pyroelectric properties of ferroelectric lead germanate Pb5Ge3O11 in both single-crystal and ceramic form is presented. It is shown that the expected noise-equivalent power for lead germanate is similar to that of triglycine sulphate, and the voltage responsivity is slightly lower. The superior chemical and mechanical properties of lead germanate make it an attractive alternative for use in pyroelectric detectors.
Identification of linear systems using correlation data
- Author(s): D.B. Hernández Castaños and D.Q. Mayne
- Source: Electronics Letters, Volume 8, Issue 14, p. 346 –348
- DOI: 10.1049/el:19720253
- Type: Article
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p.
346
–348
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Powerful algorithms exist for identifying linear systems given input/output data. In many cases, however, it is convenient to obtain the data in the form of correlation functions. The data in this form are often more condensed. An extension of Åström's identification algorithm for making it able to use correlation functions in the place of an input/output record is described.
Theory of optimum M-ary laser detection
- Author(s): A.K. Kamal ; P.D. Sharma ; N. Malaviya
- Source: Electronics Letters, Volume 8, Issue 14, p. 348 –349
- DOI: 10.1049/el:19720254
- Type: Article
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p.
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–349
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An upper bound on the average error probability of all possible M-ary optical systems, using large-average photon statistics, has been derived. This bound clearly indicates the superiority of the M-ary system over the binary one in terms of allowable transmission rates below which the error rate decreases exponentially with code-block length. A probabilistic solution for the problem of efficient signal selection has been found and demonstrated with a simple illustration.
Frequency/temperature characteristics of Gunn devices
- Author(s): R. Davies ; W.S.C. Gurney ; A. Mircea
- Source: Electronics Letters, Volume 8, Issue 14, p. 349 –351
- DOI: 10.1049/el:19720255
- Type: Article
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p.
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–351
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The variability and large magnitude of the frequency/temperature coefficient of Gunn oscillators has limited the application of these devices. The letter outlines a program of experiments and computer simulations aimed at achieving an understanding of the basic ∂f/∂T mechanism and thus producing a deep stable oscillator. Our simulations successfully predict observed trends in the ∂f/∂T behaviour of Gunn devices with both alloyed metal and n+ regrown contacts. The results of our study show that stable oscillators with a small loaded Q factor and near maximum power output are realisable.
Improved geometry for a semiconductor surface-wave oscillator
- Author(s): T.J.B. Swanenburg
- Source: Electronics Letters, Volume 8, Issue 14, p. 351 –352
- DOI: 10.1049/el:19720256
- Type: Article
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p.
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–352
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It is shown theoretically that the recently observed negative conductance of an interdigital-electrode structure situated near a semiconductor surface is enhanced considerably if a configuration is chosen which is symmetrical with respect to a plane perpendicular to the carrier drift velocity. Furthermore, the threshold drift velocity may be much lower than in the original configuration.
Image-cancelling mixers
- Author(s): D.P. Howson and J.G. Gardiner
- Source: Electronics Letters, Volume 8, Issue 14, p. 352 –354
- DOI: 10.1049/el:19720257
- Type: Article
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–354
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Image-cancelling mixers are a form of image-recovery or image-enhancement mixer. The method of operation is discussed and the possible circuit arrangements are derived. It is shown that it is necessary to have a π/2 phase shift in the local oscillator path to one mixer, and a corresponding phase shift in the i.f. path of the same mixer. No restrictions appear necessary on the phase shifts in the signal paths, but it is argued that equal-signal phase shifts to the two mixers are advantageous.
Stability circle criterion with 3rd-order spatial-harmonic balance for nonlinear distributed-parameter systems
- Author(s): R.G. Jumarie
- Source: Electronics Letters, Volume 8, Issue 14, p. 354 –355
- DOI: 10.1049/el:19720258
- Type: Article
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p.
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–355
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A 1-dimensional, 1-distributed-parameter nonlinear system which exhibits a structure similar to that of the standard nonlinear control loop with lumped-parameter elements, is investigated from the viewpoint of its input-output stability. An approached stability circle criterion, available in the context of a 3rd-order harmonic balance with respect to the distributed parameter, is stated.
Differential d.c. conductance of a p-n-junction space-charge region
- Author(s): C.T. Sah
- Source: Electronics Letters, Volume 8, Issue 14, p. 355 –356
- DOI: 10.1049/el:19720259
- Type: Article
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p.
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–356
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It is shown that the differential d.c. conductance under reverse bias can be correctly obtained from the lumped approximation of the small-signal distributed-transmission-line model if the true majority-carrier concentration in the edge region of the space-charge layer is taken into account.
Multimillisecond timse delays with wrap-around surface-acoustic-wave delay lines
- Author(s): T.M. Reeder ; H.J. Shaw ; E.M. Westbrook
- Source: Electronics Letters, Volume 8, Issue 14, p. 356 –358
- DOI: 10.1049/el:19720260
- Type: Article
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p.
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–358
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Time delays of up to 3 ms in passive systems, and up to 20 ms with the addition of loss compensation by means of internal surface-wave amplifiers, have been observed in wrap-around surface-wave delay lines constructed of Bi12GeO20 and operating in a recirculating mode at 52 MHz.
Frequency-modulation sensitivity and frequency-pushing factor of a pd-n-p+ punchthrough microwave diode
- Author(s): H. Herbst and W. Harth
- Source: Electronics Letters, Volume 8, Issue 14, p. 358 –359
- DOI: 10.1049/el:19720261
- Type: Article
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Measurements of the frequency-modulation sensitivity, the frequency-pushing factor and f.m. noise are reported. At bias currents with maximum microwave-power output where amplitude modulation is very small, both the pushing factor and the f.m. noise reach low levels, which is of particular interest for practical applications.
Design of nonrecursive digital moving-target-indicator radar filters
- Author(s): J.J. Hill
- Source: Electronics Letters, Volume 8, Issue 14, p. 359 –360
- DOI: 10.1049/el:19720262
- Type: Article
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p.
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–360
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This letter describes the design methods for a class of non-recursive digital m.t.i. filters with a multiple zero at z = 1 and an equiripple passband. Some examples of these responses are given, together with the filter coefficients.
Transition from sheath-convection to saturation-current behaviour of a Langmuir probe in a flowing plasma
- Author(s): R.M. Clements ; R.D. Kerr ; A.A. Offenberger ; P.R. Smy
- Source: Electronics Letters, Volume 8, Issue 14, p. 361 –362
- DOI: 10.1049/el:19720263
- Type: Article
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p.
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–362
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The transition between diffusive (saturated-current) and sheath-convection [current ∝(voltage)½] behaviour of the current to a negatively biased Langmuir probe in a plasma jet has been studied experimentally by varying the electron density over a wide range. The measurements verify for the first time the expected change in the dependence of current on voltage. However, this change occurs at higher electron densities than expected, and, when saturated-current behaviour is finally obtained, these currents are significantly lower than their calculated values and, surprisingly, remain close to the sheath-convection currents calculated for moderate voltages.
Reciprocal but nonsymmetrical transmission characteristics of tapered irises
- Author(s): Thomas A. Brewer and T. Koryu Ishii
- Source: Electronics Letters, Volume 8, Issue 14, p. 362 –363
- DOI: 10.1049/el:19720264
- Type: Article
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–363
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Both the input impedance and the transmission coefficient of an H plane tapered iris are found to be reciprocal but asymmetrical. The H plane tapered iris behaves similarly to a transformer of nonunity turn ratio.
Electron-relaxation effects in transferred-electron devices revealed by new simulation method
- Author(s): D. Jones and H.D. Rees
- Source: Electronics Letters, Volume 8, Issue 14, p. 363 –364
- DOI: 10.1049/el:19720265
- Type: Article
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p.
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–364
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A simulation method which efficiently solves the complete Boltzmann transport equation has been used to analyse transferred-electron oscillators. Four hitherto unrecognised relaxation effects have been identified, which are of major significance in characterising modes of operation.
Optimum loading for relaxation l.s.a. diode
- Author(s): M. Wasse ; J. Mun ; J.S. Heeks
- Source: Electronics Letters, Volume 8, Issue 14, p. 364 –366
- DOI: 10.1049/el:19720266
- Type: Article
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In the relaxation l.s.a. mode, the r.f. waveform across the loaded diode reaches very high voltages and then approaches, in part, the first cycle of a damped oscillation. The degree of damping depends on the loading of the circuit. It is shown theoretically that, for typical drive voltages, if the load is greater than G0/120 where G0 is the low-field device conductance, the voltage will not ultimately fall below threshold, accumulated space charge will not be dispersed and the diode will suffer avalanche breakdown owing to domain formation. Conversely, the loading must approach G0/120 to obtain maximum efficiency. These effects have been demonstrated in a pseudolumped circuit, using vapour-epitaxial metal-contacted devices. 400 W of peak power with 13.6% efficiency at 6.1 GHz has been obtained.
Technique for compensating for reflector-antenna-surface errors with long correlation lengths
- Author(s): E.A. Parker and P.R. Cowles
- Source: Electronics Letters, Volume 8, Issue 14, p. 366 –367
- DOI: 10.1049/el:19720267
- Type: Article
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p.
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–367
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The profile of a secondary mirror has been figured to compensate for errors with long correlation lengths on the surface of a parabolic reflector 2.8 m in diameter. At 34 GHz, a gain improvement of 2.9 dB was obtained, with a corresponding decrease in the sidelobe level close to the main beam.
Technique for varying the conversion loss against frequency of a surface-wave transducer without apodisation
- Author(s): G.R. Nudd
- Source: Electronics Letters, Volume 8, Issue 14, p. 367 –368
- DOI: 10.1049/el:19720268
- Type: Article
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p.
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–368
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A technique for controlling the insertion loss of a surface-wave acoustic transducer as a function of frequency, which avoids apodisation and its associated problems, is described. As an example of its implementation, a flat bandpass filter of constant aperture is described.
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