Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 9, Issue 4, 22 February 1973
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Volume 9, Issue 4
22 February 1973
Current-zero detection in thyristor convertors
- Author(s): J.S. Ford
- Source: Electronics Letters, Volume 9, Issue 4, page: 73 –73
- DOI: 10.1049/el:19730054
- Type: Article
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p.
73
(1)
A method of detecting current zeros in thyristor convertors is described. The method utilises an optically coupled isolator to sense the voltage across each of the thyristors in the convertor, thereby detecting the conduction state of each device. This information is then processed by simple logic to detect current zeros from the convertor.
Distributed frame synchronisation by nonlinear-shift-register sequences
- Author(s): P. Tolstrup Nielsen
- Source: Electronics Letters, Volume 9, Issue 4, p. 73 –75
- DOI: 10.1049/el:19730055
- Type: Article
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p.
73
–75
(3)
A class of nonlinear-shift-register sequences is proposed for use as synchronisation words in systems employing the distributed method of synchronisation. Owing to the unique properties of these sequences, it is possible to achieve fast acquisition by simple circuits, even for long frames or multiframes.
Least-squares monotonic lowpass filters with sharp cutoff
- Author(s): B.D. Rakovich and V.B. Litovski
- Source: Electronics Letters, Volume 9, Issue 4, p. 75 –76
- DOI: 10.1049/el:19730056
- Type: Article
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p.
75
–76
(2)
A new class of lowpass-filter functions with no finite zeros and a monotonic magnitude response is first derived by using a least-squares norm to minimise the passband attenuation, and these filter functions are then augmented by adding one pair or multiple pairs of jω-axis zeros. The magnitude characteristics of these filters are compared with those of the generalised inverse Cheby̅shev filters and are found to be superior, both in the passband and in the stopband.
Complementary dynamic m.o.s. logic circuits
- Author(s): E. Vittoz and H. Oguey
- Source: Electronics Letters, Volume 9, Issue 4, p. 77 –78
- DOI: 10.1049/el:19730057
- Type: Article
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–78
(2)
Allowing both p and n channel groups of transistors to be blocked between transitions of c.m.o.s. gates leads to complementary dynamic m.o.s. circuits which, in many cases, are significantly less complex than their static counterparts. The value of the concept and a method of synthesis are demonstrated with a practical example. Systematic application to frequency dividers yields very simple new structures.
Open resonator operating at 337 μm wavelength
- Author(s): R.J. Batt ; H.L. Bradley ; D.J. Harris
- Source: Electronics Letters, Volume 9, Issue 4, p. 78 –79
- DOI: 10.1049/el:19730058
- Type: Article
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p.
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–79
(2)
Open-resonator techniques are investigated at the sub-millimetre wavelength of 337 μm A folded spherical resonator with periodic variation of intermirror separation is excited at 33 μm using an HCN laser. Initial results show that the theoretically expected form of resonance spectra can be obtained experimentally, and that the method should be applicable for dielectric-property and scattering-cross-section measurements in this wavelength range.
Floating switch with large-signal capability
- Author(s): A. Hamed and H. Sutcliffe
- Source: Electronics Letters, Volume 9, Issue 4, p. 79 –80
- DOI: 10.1049/el:19730059
- Type: Article
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p.
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–80
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Electronic switches using field-effect devices are widely used, but suffer from a low ratio of signal-waveform amplitude to control-waveform amplitude. A switch configuration is described using two devices and overcoming this disadvantage.
Computer analysis of nullor networks
- Author(s): D. Coldham and L.T. Bruton
- Source: Electronics Letters, Volume 9, Issue 4, p. 80 –82
- DOI: 10.1049/el:19730060
- Type: Article
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–82
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A computer program for the analysis of nullor circuits is presented. The method follows the approach of Davies, and requires the formation of the incidence matrix for the corresponding passive network. Output is available in graphical form or printed form. The program is in FORTRAN IV, and is suitable for interactive use.
Pulsed measuring technique for isothermal transistor characteristics
- Author(s): A.W. Alden and A.R. Boothroyd
- Source: Electronics Letters, Volume 9, Issue 4, p. 82 –83
- DOI: 10.1049/el:19730061
- Type: Article
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p.
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–83
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A procedure is described which allows the determination of the d.c. and a.c. characteristics of the bipolar transistor under defined isothermal conditions. Representative results are given illustrating the need for such temperature control. Explanations are advanced for the observed temperature dependence of transistor delay time.
Deadbeat control of linear multivariable discrete-time systems
- Author(s): B. Porter
- Source: Electronics Letters, Volume 9, Issue 4, p. 83 –84
- DOI: 10.1049/el:19730062
- Type: Article
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p.
83
–84
(2)
A simple closed-form control law for the deadbeat control of a class of linear multivariable discrete-time systems is presented.
Reply to ‘Comments on New measurement method of Gunn-diode impedance’
- Author(s): H. Hartnagel
- Source: Electronics Letters, Volume 9, Issue 4, p. 84 –85
- DOI: 10.1049/el:19730063
- Type: Article
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p.
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–85
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A reply is given to comment by Charlton et al. on a letter by Hartnagel et al. which describes a method of deriving the negative conductance of X-band Gunn diodes from oscillation buildup characteristics when a steep bias-voltage step is applied.
Microwave frequency division using transferred-electron devices
- Author(s): L.C. Upadhyayula and S.Y. Narayan
- Source: Electronics Letters, Volume 9, Issue 4, p. 85 –86
- DOI: 10.1049/el:19730064
- Type: Article
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85
–86
(2)
Transferred-electron devices (t.e.d.s), when biased above threshold (Vth) exhibit transit-time or circuit-controlled oscillations. This property of t.e.d.s is used to achieve dynamic division at microwave frequencies. The device is biased at 0.9–0.95 Vth using a d.c. power source, and an input signal of 0.1–0.3 Vth, is used to raise the device bias above threshold level. The division occurs when the input frequency is an integral multiple of the oscillator frequency. We observed dynamic division by 2, 3 and 4 with the output frequency 4.0 GHz. The bandwidth for division by two is 560 MHz referred to the input.
640 Mbit/s waveguide transmitter at 38 GHz
- Author(s): G. Hanke and W. Lorek
- Source: Electronics Letters, Volume 9, Issue 4, p. 86 –88
- DOI: 10.1049/el:19730065
- Type: Article
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p.
86
–88
(3)
The principle of a digital waveguide transmitter working at 38 GHz is given. A pulse-code-modulation simulator, with a bit rate of 640 Mbit/s, produces the modulation signal and also allows error-rate measurements. Typical switching times of the modulator are less than 500 ps. These results have been obtained by use of a varactor diode installed in a rectangular R band waveguide.
Measurement of carrier-concentration profiles in epitaxial indium phosphide
- Author(s): M.J. Cardwell and R.F. Peart
- Source: Electronics Letters, Volume 9, Issue 4, p. 88 –89
- DOI: 10.1049/el:19730066
- Type: Article
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p.
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–89
(2)
A technique is described for measuring carrier-concentration profiles of vapour-deposited epitaxial indium phosphide using the capacitance/voltage characteristics of a reverse biased metal-insulator-semiconductor diode. Profiles of layers grown on chromium and tin-doped substrates are presented. The effect of dopant type on the sharpness of electrical interfaces is discussed.
Moving-target-indicator recursive radar filter using bucket-brigade circuits
- Author(s): J.B.G. Roberts ; R. Eames ; K.A. Roche
- Source: Electronics Letters, Volume 9, Issue 4, p. 89 –90
- DOI: 10.1049/el:19730067
- Type: Article
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p.
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–90
(2)
A prototype clutter-rejection filter for radar is described. It uses analogue shift registers of the bucket-brigade type, which, in common with charge-coupled devices, can combine the flexibility of digital processing with the simplicity of analogue operation. Certain imperfections in the devices are shown to be particularly important for moving-target-indicator filtering.
Resistance of earth electrodes
- Author(s): James R. Wait
- Source: Electronics Letters, Volume 9, Issue 4, p. 90 –91
- DOI: 10.1049/el:19730068
- Type: Article
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p.
90
–91
(2)
By use of potential theory, expressions are obtained for the ohmic resistance of a slender metallic electrode located in a fluid-filled borehole. The configuration is idealised as a spheroidal confocal system.
Thickness dependence of effective coupling factors of ZnO thin-film surface-wave transducers
- Author(s): H. Sasaki ; N. Chubachi ; Y. Kikuchi
- Source: Electronics Letters, Volume 9, Issue 4, p. 92 –93
- DOI: 10.1049/el:19730069
- Type: Article
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p.
92
–93
(2)
The effective coupling factors of ZnO thin-film surface-wave transducers are described for the various transducer arrangements; the factors are estimated from the motional conductance measurement, and their thickness dependence is shown in relation to the theoretically calculated values.
Microstrip bandpass filters with reduced radiation effects
- Author(s): B. Easter and J.G. Richings
- Source: Electronics Letters, Volume 9, Issue 4, p. 93 –94
- DOI: 10.1049/el:19730070
- Type: Article
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p.
93
–94
(2)
The realisation of a microstrip bandpass filter employing coupled hairpin-line resonators is discussed. The performance of an experimental filter at 11 GHz confirms that the low-radiation property of the hairpin resonator leads to improved behaviour compared with a coupled-resonator filter o conventional form.
Computational estimate of applicability of infinite-array theory
- Author(s): D. Parkin
- Source: Electronics Letters, Volume 9, Issue 4, p. 94 –96
- DOI: 10.1049/el:19730071
- Type: Article
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p.
94
–96
(3)
Measurements on a 275-waveguide-element planar array do not indicate the E plane coupling null predicted computationally on the assumption of an infinite array. A numerical method, utilising the fast Fourier transform, for determining the number of elements required to exhibit the E plane null, is presented with computed results.
Constant-factor delta modulator
- Author(s): A.T. Kyaw and R. Steele
- Source: Electronics Letters, Volume 9, Issue 4, p. 96 –97
- DOI: 10.1049/el:19730072
- Type: Article
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p.
96
–97
(2)
A companded delta modulator, employing an adaptation principle that produces voltages fed back to the error point in the coder which are discrete and multivalued, is achieved with just a 1 bit memory and simple signal processing, and is a significant invention. The constant-factor-delta-modulator system described here is an extension of this principle, which gives an improved signal/noise ratio at the output of the decoder and remove an objectionable hunting characteristic. These improvements are acquired due to a slight increase in the complexity of the coder.
Synthesis of cutpoint cellular arrays
- Author(s): G. Papakonstantinou
- Source: Electronics Letters, Volume 9, Issue 4, p. 97 –99
- DOI: 10.1049/el:19730073
- Type: Article
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p.
97
–99
(3)
The rules for the simplification of cascades, used previously for the synthesis of cutpoint cellular arrays, are combined into only one rule, which is more general and more powerful. The efficiency of the synthesis algorithm is increased from 80% to almost 100%.
Locating a horizontal magnetic dipole buried in a 2-layer earth
- Author(s): V. Ramaswamy and H.W. Dosso
- Source: Electronics Letters, Volume 9, Issue 4, p. 99 –100
- DOI: 10.1049/el:19730074
- Type: Article
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p.
99
–100
(2)
The possibility of applying an electromagnetic technique to locate a horizontal magnetic dipole buried in the upper layer of a 2-layer earth is studied. Results for a highly conducting substratum for various source depths and frequencies are presented.
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