Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 9, Issue 10, 17 May 1973
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Volume 9, Issue 10
17 May 1973
AgSn cathode contact in gallium-arsenide transferred-electron devices
- Author(s): M.P. Wasse ; B.W. Clark ; R.F.B. Conlon
- Source: Electronics Letters, Volume 9, Issue 10, p. 189 –190
- DOI: 10.1049/el:19730139
- Type: Article
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p.
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–190
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Simple observations of the temperature dependence of the threshold current of AgSn-contacted gallium-arsenide transferred-electron devices are interpreted in terms of Schottky-barrier cathodes. From the measurements, the barrier heights are deduced and a mechanism is suggested for their formation. The consequences of the presence of the barrier on the operation of oscillators and amplifiers are discussed and illustrated by experimental results.
Digital-phase-shifter performance
- Author(s): G.D. Brownlie
- Source: Electronics Letters, Volume 9, Issue 10, p. 190 –191
- DOI: 10.1049/el:19730140
- Type: Article
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–191
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The performance of a new type of digital phase shifter is compared with that of analogue systems of comparable complexity. The digital method results in greater stability and precision and is particularly applicable to digitally controlled systems that require a large number of phase-shifted signals.
Measurement of external Q factor of microwave oscillators using frequency pulling or frequency locking
- Author(s): G.S. Hobson
- Source: Electronics Letters, Volume 9, Issue 10, p. 191 –193
- DOI: 10.1049/el:19730141
- Type: Article
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–193
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Conditions are identified for the measurement of the external Q factor of microwave oscillators by use of frequency pulling or locking techniques. A small modification to a technique proposed previously for frequency locking is derived, and is extended to the case of frequency pulling. It is shown that measurements of the full locking or pulling bandwidths give information on the first derivatives, with respect to r.f.-voltage amplitude, of the device susceptance and conductance.
Monolithically integrated Bragg deflector for an optical guided wave made of zinc-oxide film
- Author(s): N. Chubachi ; J. Kushibiki ; Y. Kikuchi
- Source: Electronics Letters, Volume 9, Issue 10, p. 193 –194
- DOI: 10.1049/el:19730142
- Type: Article
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–194
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A new film Bragg deflector has been fabricated on a non-piezoelectric substrate. The deflector is made of ZnO film, so that both an optical waveguide and acoustic-surface-wave transducers are monolithically integrated. High diffraction efficiencies (more than 90%) are obtained with this device.
Piecewise-linear-signal representation
- Author(s): C.R. Paul and R.W. Koch
- Source: Electronics Letters, Volume 9, Issue 10, p. 194 –195
- DOI: 10.1049/el:19730143
- Type: Article
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–195
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A new method for representing a signal is provided. An exact representation of a piecewise linear approximation of the signal with a finite number of basis functions is presented.
Surface-acoustic-wave oscillators: mode selection and frequency modulation
- Author(s): J. Crabb ; M.F. Lewis ; J.D. Maines
- Source: Electronics Letters, Volume 9, Issue 10, p. 195 –197
- DOI: 10.1049/el:19730144
- Type: Article
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–197
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The letter discusses various aspects of the design and performance of surface-acoustic-wave oscillators, including two proved solutions to the mode-selection problem and a demonstration of the wide frequency-modulation capability.
Rain-attenuation measurements of millimetre waves over short paths
- Author(s): J.W. Mink
- Source: Electronics Letters, Volume 9, Issue 10, p. 198 –199
- DOI: 10.1049/el:19730145
- Type: Article
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Results of rain-attenuation measurements at millimetre waves are presented that have been obtained with a shuttle-pulse technique. This technique requires a path length through rain of only a few metres, so that the rainfall rate and drop-size distribution can be considered to be uniform along this path.
Active surface-wave directional coupler
- Author(s): K.L. Davis ; V.L. Newhouse ; C.W. Lee ; R.L. Gunshor
- Source: Electronics Letters, Volume 9, Issue 10, p. 199 –201
- DOI: 10.1049/el:19730146
- Type: Article
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We report experimental results which show that noncollinear surface-wave mixing on [111]-cut bismuth–germanium oxide can be used to realise an active, switchable directional coupler. For low-level inputs, the coupling is enhanced by as much as 20 dB by a semiconductor placed over the interaction region. The directivity is found to be greater than 40 dB.
Bias-dependent phase delay of Schottky contact microstrip line
- Author(s): D. Jäger and W. Rabus
- Source: Electronics Letters, Volume 9, Issue 10, p. 201 –203
- DOI: 10.1049/el:19730147
- Type: Article
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Schottky contact lines are a form of microstrip on a semiconducting substrate, the strip of which forms a rectifying metal–semiconductor contact. Such a line has an extremely low phase velocity that is determined by the ratio of the depletion-region width to the substrate thickness, i.e. by the bias. Measurements agree well with theoretical expressions that are deduced from a parallel-plate-waveguide model.
Numerical computation of the input impedance of a finite helix
- Author(s): D.C. Wynn and C.T. Carson
- Source: Electronics Letters, Volume 9, Issue 10, p. 203 –205
- DOI: 10.1049/el:19730148
- Type: Article
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A numerical method is given for the determination of the input impedance of a thin-wire helix. The problem is approximated by a frequency-dependent matrix equation whose solution is an approximation to the current distribution and is used in a variational expression for the impedance. Experimental and theoretical results for the determination of the resonant frequency are included.
Direct microwave imaging with enhanced resolution
- Author(s): A.P. Anderson ; R.D. Orme ; S.J. Mawani
- Source: Electronics Letters, Volume 9, Issue 10, p. 205 –206
- DOI: 10.1049/el:19730149
- Type: Article
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A means of direct imaging with a microwave lens is described in which the object is scanned by the focused source/receiver unit. Enhanced resolution of the object is demonstrated by the closely spaced image-intensity contours obtained.
Application of Howitt transformations to 2-element-kind networks
- Author(s): V. Tavşanoglu
- Source: Electronics Letters, Volume 9, Issue 10, p. 206 –208
- DOI: 10.1049/el:19730150
- Type: Article
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–208
(3)
A relationship is obtained for the nonsingular T transformation that exists between two minimal realisations of the state equations and the Howitt transformation between the corresponding 2-element-kind networks. It is proved that the Howitt transformation can generate all the passive minimal RC or RL equivalent networks that can be generated by the nonsingular T transformation.
Estimation of discrete-time systems using pseudorandom sequences
- Author(s): Y. Funahashi and K. Nakamura
- Source: Electronics Letters, Volume 9, Issue 10, p. 208 –209
- DOI: 10.1049/el:19730151
- Type: Article
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–209
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The pseudorandom binary sequence is applied to the parameter estimation of discrete-time systems. The proposed method, based on correlation analysis and system theory, requires a smaller number of correlators than the other methods. The estimates of the parameters are shown to be asymptotically unbiased.
Estimation of weighting-sequence matrices by correlation method
- Author(s): Y. Funahashi and K. Nakamura
- Source: Electronics Letters, Volume 9, Issue 10, p. 209 –210
- DOI: 10.1049/el:19730152
- Type: Article
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The pseudorandom binary sequence transformed by the Hadamard matrix is applied to the estimation of weighting-sequence matrices of multi-input and multioutput discrete-time systems. The method is based on the correlation analysis and matrix algebra. The weighting-sequence matrix is obtained directly from the measured-correlation matrix.
Characteristics of ion-implanted hybrid voltage-variable capacitors
- Author(s): B.A. MacIver
- Source: Electronics Letters, Volume 9, Issue 10, p. 210 –212
- DOI: 10.1049/el:19730153
- Type: Article
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–212
(3)
Hybrid voltage-variable capacitors were fabricated with hyperabrupt ion-implanted doping profiles. The capacitance uniformity was within 2% over the operating voltage range. Losses in the low-bias-voltage range were reduced by a factor of 3 by a 475°C anneal in N2–H2. A small bias-temperature instability was observed.
Comment on ‘Active RC realisation of a 3rd-order lowpass Butterworth characteristic‘
- Author(s): F. Anday
- Source: Electronics Letters, Volume 9, Issue 10, page: 212 –212
- DOI: 10.1049/el:19730154
- Type: Article
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Generalised autocorrelation theorem
- Author(s): K.R. Rao ; K. Revuluri ; N. Ahmed
- Source: Electronics Letters, Volume 9, Issue 10, p. 212 –214
- DOI: 10.1049/el:19730155
- Type: Article
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p.
212
–214
(3)
It is shown that the modified generalised discrete transform of the autocorrelation of a sequence yields the shift-invariant spectral modes within some scale factors. This is a fundamental result, as it is a logical extension of the well known autocorrelation theorem for the discrete Fourier transform.
Comment on ‘New definition of multiple-root sensitivity’
- Author(s): M.P. Dave
- Source: Electronics Letters, Volume 9, Issue 10, page: 215 –215
- DOI: 10.1049/el:19730156
- Type: Article
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215
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New method for the testing of capacitors for internal ionisation discharges
- Author(s): M.J. Drury
- Source: Electronics Letters, Volume 9, Issue 10, p. 215 –216
- DOI: 10.1049/el:19730157
- Type: Article
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215
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The letter concerns the development of a method for testing dielectric capacitors for the presence of internal discharges that can lead to breakdown of the insulation and failure of the capacitor. This method is suitable for rapid, production-line testing of capacitors; minor modification only would be necessary for it to be applied to other insulation media, e.g. in power cables.
Method for measuring the anisotropy of precipitation media
- Author(s): G.C. McCormick and A. Hendry
- Source: Electronics Letters, Volume 9, Issue 10, p. 216 –218
- DOI: 10.1049/el:19730158
- Type: Article
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p.
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–218
(3)
A system for measuring both the differential phase shift and differential attenuation through precipitation over a 1-way transmission link is discussed. An example of observations of a summer shower is given. A general formula for cross-polarisation is derived.
Coaxially fed hollow cylindrical monopole in a rectangular waveguide
- Author(s): A.G. Williamson and D.V. Otto
- Source: Electronics Letters, Volume 9, Issue 10, p. 218 –220
- DOI: 10.1049/el:19730159
- Type: Article
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218
–220
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A formally exact solution that can easily be put in a form suitable for accurate numerical calculation is presented for a hollow coaxially fed cylindrical monopole in a rectangular waveguide. The solution utilises a well known Fourier-transform technique in conjunction with a Cheby̅shev polynomial representation for the unknown function. The result is an almost diagonalised infinite matrix—a form eminently suitable for the purpose of numerical inversion.
Equivalence of the Box–Jenkins–Aström control law to the Kalman linear regulator
- Author(s): D.J. Hughes
- Source: Electronics Letters, Volume 9, Issue 10, p. 220 –221
- DOI: 10.1049/el:19730160
- Type: Article
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The letter demonstrates the equivalence of the BJA control law to the Kalman linear regulator for a class of single-input single-output stochastic LQP control problems. The result is obtained by comparing explicitly the two control laws derived for the same problem.
Time-domain reflectometry from Smith-chart plotting
- Author(s): P.I. Somlo
- Source: Electronics Letters, Volume 9, Issue 10, p. 221 –222
- DOI: 10.1049/el:19730161
- Type: Article
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Attention is drawn to the fact that time-domain reflectometry may be carried out without any special apparatus by measuring the input impedances of a transmission-line system at a number of frequencies, using a slotted line for instance. When these impedances are referred to different planes along the line, and the corresponding plots on the Smith charts are produced, the centroids of these plots yield the reflection coefficient as a function of distance along the transmission line.
Fast high-input-impedance unity-gain buffer stage
- Author(s): B.L. Hart and R.W.J. Barker
- Source: Electronics Letters, Volume 9, Issue 10, p. 223 –224
- DOI: 10.1049/el:19730162
- Type: Article
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The interconnection of a monolithic matched-f.e.t. pair and a high-frequency bipolar-transistor array permits the design of a fast high-input-impedance unity-gain buffer stage that does not employ passive components. Typical performance data are: input direct bias current <50 pA, output impedance <50 Ω, power consumption <60 mW.
State-space approach to the multiplication error in a digital filter
- Author(s): K.M. Wong
- Source: Electronics Letters, Volume 9, Issue 10, p. 224 –226
- DOI: 10.1049/el:19730163
- Type: Article
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The state-space method has been used to evaluate the statistical error due to the finite-precision arithmetic in a digital filter. The actual error of a 2nd-order filter obtained from computer simulation has also been plotted against the expected error
Boron redistribution at the oxide–silicon interface during drive-in in oxidising atmospheres
- Author(s): G. Masetti ; S. Solmi ; G. Soncini
- Source: Electronics Letters, Volume 9, Issue 10, p. 226 –228
- DOI: 10.1049/el:19730164
- Type: Article
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A modified form of the Kato and Nishi solution for computing boron redistribution at the moving oxide–silicon interface is presented, its advantages are discussed, and its accuracy is checked by extensive boron drive-in experiments carried out in oxidising atmospheres. A segregation coefficient k = 4, practically not influenced by either the boron-doping concentration or the silicon-oxidation rate, is suggested.
Extension of a small-signal model for thyristor-rectifier control loops when using an asynchronous delay-type firing circuit
- Author(s): R. Prajoux ; P. Thierry ; J. Jalade
- Source: Electronics Letters, Volume 9, Issue 10, p. 228 –229
- DOI: 10.1049/el:19730165
- Type: Article
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A previously established model for the small-signal behaviour of thyristor-rectifier control loops is extended to rectifiers involving an asynchronous delay-type firing circuit. It is shown that this type of firing circuit behaves like a positive-feedback loop across the rectifier, and that the order of the system is increased by one unit.
Electronically variable analogue delay
- Author(s): J.M. Deacon ; J. Heighway ; D.E. Hooper ; D.W. Tarrant
- Source: Electronics Letters, Volume 9, Issue 10, p. 229 –230
- DOI: 10.1049/el:19730166
- Type: Article
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A novel approach to the use of acoustic-surface-wave filters in the realisation of variable analogue delays is described. Maximum delays of up to several tens of microseconds have already been achieved in practice, and it is expected that engineered systems will have high dynamic ranges and low distortions.
j multiplier: a new network device
- Author(s): A.B. Sardharwalla and M.A. Laughton
- Source: Electronics Letters, Volume 9, Issue 10, p. 231 –232
- DOI: 10.1049/el:19730167
- Type: Article
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This letter describes a novel linear nonreciprocal active 2-port network element called a j multiplier. It has the unique property that, whenever a nonlinear immittance is connected across one of its ports (port 1), the resulting 2-terminal network behaves as the original immittance multiplied by j; i.e. a resistance appears as an imaginary resistance, whereas capacitors or inductors appear as frequency-dependent real resistances. There are two types of j multipliers: the voltage j multiplier and the current j multiplier. The realisations of both these types of devices at any frequency using ±jR elements, or at one single frequency using ±R, L and C elements and a controlled source, are given.
Si and GaAs 0.5 μm-gate Schottky-barrier field-effect transistors
- Author(s): W. Baechtold ; K. Daetwyler ; T. Forster ; T.O. Mohr ; W. Walter ; P. Wolf
- Source: Electronics Letters, Volume 9, Issue 10, p. 232 –234
- DOI: 10.1049/el:19730168
- Type: Article
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Si and GaAs Schottky-barrier field-effect transistors with gate lengths of 0.5 μm have been experimentally realised. Noise and gain properties were measured in the microwave range up to 20 GHz. When compared with 1 μm-gate f.e.t.s, the devices show considerable improvements in gain and in noise figure. At 10 GHz, the following values were measured: Si m.e.s.f.e.t.: maximum available gain = 5.9 dB, noise figure = 5.8 dB; GaAs m.e.s.f.e.t.: maximum available gain = 12.8 dB, noise figure = 3.7 dB.
Calculation of the secondary-radiation pattern for a paraboloid reflector with a given illumination function and feed position
- Author(s): E.W. Munro ; A.J.T. Whitaker ; P.A. McInnes
- Source: Electronics Letters, Volume 9, Issue 10, p. 234 –235
- DOI: 10.1049/el:19730169
- Type: Article
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A computer program is described for the calculation of the near-axis secondary-radiation pattern of a parabolic reflector. The program has been devised for a laterally or axially displaced feed, in particular a log-periodic dipole array. The illumination-function data are input in the form of radiation-pattern co-ordinates of the feed aerial.
Multistrip coupler in acoustic-surface-wave filters
- Author(s): J.M. Deacon ; J. Heighway ; J.A. Jenkins
- Source: Electronics Letters, Volume 9, Issue 10, p. 235 –236
- DOI: 10.1049/el:19730170
- Type: Article
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–236
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Multistrip couplers have been used in a number of applications: to reduce spurious modes, to make an efficient reflecting track changer, to operate a magic T etc. However, no results on the effects of varying the aperture of the sending transducer have yet been reported. Here we present measurements taken with an electrostatic probe of the transmitted signal amplitude for various transducer apertures, and discuss their implications.
Reply to ‘Comment on Determination of the velocity/field characteristic for n-type indium phosphide from dipole-domain measurements’
- Author(s): B.A. Prew
- Source: Electronics Letters, Volume 9, Issue 10, p. 236 –238
- DOI: 10.1049/el:19730171
- Type: Article
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Simple matrix-theory proof of the discrete dyadic convolution theorem
- Author(s): M.N. Gulamhusein
- Source: Electronics Letters, Volume 9, Issue 10, p. 238 –239
- DOI: 10.1049/el:19730172
- Type: Article
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p.
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A matrix-theory proof of the (periodic) discrete dyadic convolution theorem based on the determination of the eigen-values and eigenvectors of the dyadic convolution matrix is given. The eigenvalues are shown to be equal to the discrete Walsh transform of the dyadic convolution system's impulse response, and the matrix of the eigenvectors corresponds to the discrete Walsh-transform matrix.
Code generation with s.a.w. tapped delay lines
- Author(s): J.J. Crisp and J.S. Heeks
- Source: Electronics Letters, Volume 9, Issue 10, p. 239 –240
- DOI: 10.1049/el:19730173
- Type: Article
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A surface-acoustic-wave tapped delay line is used as the basis of a pseudonoise-code generator operating at 20 Mbits. The temperature range of operation for nonisopaustic materials has been extended by a novel arrangement of the delay line and associated circuitry. In consequence, high-acoustic-coupling low-loss materials may be used, offering the potential of high-bit-rate operation.
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