Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 15, Issue 13, 21 June 1979
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Volume 15, Issue 13
21 June 1979
Strays-insensitive switched-capacitor filters based on bilinear Z-transform
- Author(s): Ken Martin and Adel S. Sedra
- Source: Electronics Letters, Volume 15, Issue 13, p. 365 –366
- DOI: 10.1049/el:19790263
- Type: Article
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p.
365
–366
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Biquadratic circuits are introduced which enable the exact design of switched-capacitor filters using the bilinear z-transform. The resulting filters are completely insensitive to stray capacitances, and meet their specifications up to and including one-half the sampling frequency.
Integrated-circuit relay correlator for measurement-system applications
- Author(s): J.R. Jordan
- Source: Electronics Letters, Volume 15, Issue 13, p. 366 –367
- DOI: 10.1049/el:19790264
- Type: Article
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p.
366
–367
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The use of c.c.d. techniques is proposed to implement a relay correlator with features particularly attractive for measurement-system applications. Use of the circuit as a correlation interface for a microcomputer is described. The system advantages of a shorter integration-time requirement, resulting from the use of relay correlation and c.c.d. techniques, is discussed.
Self-equalising sample-and-hold circuits
- Author(s): Roubik Gregorian and Gabor C. Temes
- Source: Electronics Letters, Volume 15, Issue 13, p. 367 –368
- DOI: 10.1049/el:19790265
- Type: Article
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p.
367
–368
(2)
Two circuits are described which can perform the sample-and-hold operation without introducing the usual sin x/x distortion. They can also be used as equalisers in sampled-and-held-signal systems.
Moulded optical-fibre connectors using rods and balls
- Author(s): Hisashi Murata
- Source: Electronics Letters, Volume 15, Issue 13, p. 369 –370
- DOI: 10.1049/el:19790266
- Type: Article
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p.
369
–370
(2)
Moulded demountable single-fibre and compact multifibre connectors, which contain precision rods and balls within the plug mouldings to locate the fibres and to align pairs of plugs, have been constructed. The samples tested so far have exhibited insertion losses of less than 0.2 dB with index matching and off-axes of less than 3 μm on average.
Milliwave Fabry–Perot tuning and modulation by electrically variable external reactance
- Author(s): A. Godone ; E. Bava ; A. de Marchi
- Source: Electronics Letters, Volume 15, Issue 13, p. 370 –371
- DOI: 10.1049/el:19790267
- Type: Article
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p.
370
–371
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Fast frequency modulation of millimetric radiation in an open resonator is described. The frequency variation is obtained by means of a lumped electrically variable external reactance. The maximum modulation depth obtained is 30 kHz peak-peak. The possible applications to far-infrared lasers modulation are discussed.
Novel computer-based infrared pedestrian data-acquisition system
- Author(s): S.S. Mudaly
- Source: Electronics Letters, Volume 15, Issue 13, p. 371 –372
- DOI: 10.1049/el:19790268
- Type: Article
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p.
371
–372
(2)
The design and evaluation of an inexpensive, reliable and flexible computer-aided pedestrian data-acquisition system, capable of automatically gathering and processing information, are described. The detection of pedestrians by a unique method employing infrared techniques is also discussed.
D.C. SQUID with high energy resolution
- Author(s): P. Gutmann
- Source: Electronics Letters, Volume 15, Issue 13, p. 372 –373
- DOI: 10.1049/el:19790269
- Type: Article
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p.
372
–373
(2)
The energy resolution per 1 Hz bandwidth of a SQUID has been improved to 3.9×10−31 Js, which is better than any other value so far reported for SQUIDs. This was achieved by a good magnetic-field coupling, a high sampling rate, utilising the relaxation oscillations of the SQUID and a suitable gap voltage of the Josephson tunnel junctions.
Frequency limitation of GaAs transferred-electron devices: influence of operating d.c. and r.f. field values
- Author(s): P.A. Rolland ; E. Constant ; E. Salmer ; R. Fauquembergue
- Source: Electronics Letters, Volume 15, Issue 13, p. 373 –374
- DOI: 10.1049/el:19790270
- Type: Article
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p.
373
–374
(2)
The possibility of making use of the transferred-electron effect for power generation in the whole millimetre-wave range is shown for long and uniform-field GaAs samples. A great improvement in the upper frequency limit under large-signal operation is reported.
Multistrip coupler performance for surface-skimming bulk waves on lithium tantalate
- Author(s): E.G.S. Paige and P. Whittle
- Source: Electronics Letters, Volume 15, Issue 13, p. 374 –376
- DOI: 10.1049/el:19790271
- Type: Article
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p.
374
–376
(3)
Measurements are presented of the performance of the multi-strip coupler for X-direction propagating acoustic waves on 36° rotated Y-cut lithium tantalate. The predominant launched and coupled mode is the surface-skimming bulk wave. The coupler shows excellent discrimination against other modes. The maximum power transfer ratio is limited to approximately 4:1 and the strengths of transmitted symmetric and antisymmetric modes are found to be unequal.
Two-diode power combining near 140 GHz
- Author(s): Y.C. Ngan
- Source: Electronics Letters, Volume 15, Issue 13, p. 376 –377
- DOI: 10.1049/el:19790272
- Type: Article
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p.
376
–377
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This letter describes the achievement of 3.0 W peak power output near 145.0 GHz by combining two pulsed Impatt diodes in a resonant waveguide cavity. A combining efficiency of close to 90% was obtained.
Compensation for parasitic capacitances in switched-capacitor filters
- Author(s): Gabor C. Temes and Roubik Gregorian
- Source: Electronics Letters, Volume 15, Issue 13, p. 377 –379
- DOI: 10.1049/el:19790273
- Type: Article
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p.
377
–379
(3)
Three methods are described for eliminating the effects of parasitic capacitances associated with floating capacitors in switched-capacitor filters.
A.D. convertor using digital discriminator: an experimental result
- Author(s): A. Akademir and C.S. Aitchison
- Source: Electronics Letters, Volume 15, Issue 13, p. 379 –380
- DOI: 10.1049/el:19790274
- Type: Article
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p.
379
–380
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This letter describes a simplification in a previously described a.d. convertor using a digital discriminator, which results in a Gray code output. Practical details are given of a 4-bit encoder using this technique, which confirms that the principle is valid.
Preservation of polarisation in optical-fibre waveguides with elliptical cores
- Author(s): R.B. Dyott ; J.R. Cozens ; D.G. Morris
- Source: Electronics Letters, Volume 15, Issue 13, p. 380 –382
- DOI: 10.1049/el:19790275
- Type: Article
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p.
380
–382
(3)
Elliptically cored fibres with large index differences have been drawn and shown to hold polarisation well, the modal beat length being less than 1 mm. An analysis of the propagation characteristics shows that there is a point below the higher-mode cutoff where the difference in group velocities between the two fundamental modes is zero but where there is a large enough difference in the phase velocities to preserve polarisation.
Multidimensional fast-Fourier-transform algorithm
- Author(s): B. Arambepola and P.J.W. Rayner
- Source: Electronics Letters, Volume 15, Issue 13, p. 382 –383
- DOI: 10.1049/el:19790276
- Type: Article
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p.
382
–383
(2)
A multidimensional fast-Fourier-transform algorithm is developed for the computation of multidimensional Fourier and Fourier-like discrete transforms; it has considerably less multiplications than the conventional fast-Fourier-transform methods.
Numerical analysis of forward-biased diode structures based on direct-gap semiconductors
- Author(s): E. Velmre and B. Freidin
- Source: Electronics Letters, Volume 15, Issue 13, p. 383 –385
- DOI: 10.1049/el:19790277
- Type: Article
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p.
383
–385
(3)
A numerical model for investigation of the physical processes in forward-biased diode structures based on direct-gap semiconductors is described. The model is based on the numerical solution of the set of fundamental equations for semiconductors with boundary conditions on contacts. The effects related to the absorption of the recombination radiation are incorporated. Some results of calculations on GaAs are given.
Novel technique for eliminating the ambiguity in p.s.k. signal detection
- Author(s): A. Pongsupaht and J.D. Parsons
- Source: Electronics Letters, Volume 15, Issue 13, p. 385 –386
- DOI: 10.1049/el:19790278
- Type: Article
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p.
385
–386
(2)
When a p.s.k. signal is synchronous, i.e. the transmitted signal is phase-locked to the data, it carries extra information which allows demodulation without ambiguity. A simple practical demodulator circuit is described, which, in long term use, has proved to be very successful.
Quantitative analysis of 2-f.s.k. traffic detection
- Author(s): Børje Forssell
- Source: Electronics Letters, Volume 15, Issue 13, p. 386 –388
- DOI: 10.1049/el:19790279
- Type: Article
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p.
386
–388
(3)
Two different methods of detecting signal flow in a noncoherent 2-f.s.k. channel are analysed with respect to the necessary signal/noise ratio for a certain error probability. It is found that separate detection of each frequency requires s.n.r. ≈18 dB compared to about 19.5 dB for sum detection when the error probability is 10−7.
Dual-channel 1.5 Mb/s lightwave receiver employing an InGaAsP wavelength-demultiplexing detector
- Author(s): T.P. Lee ; T.P. Campbell ; K. Ogawa ; A.R. McCormick ; A.G. Dentai ; C.A. Burrus
- Source: Electronics Letters, Volume 15, Issue 13, p. 388 –389
- DOI: 10.1049/el:19790280
- Type: Article
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p.
388
–389
(2)
A dual-channel 1.5 Mb/s lightwave receiver has been operated simultaneously with optical signals at two different wavelengths. Two individually modulated InGaAsP/InP l.e.d.s provided optical signals at 10 and 1.18 μm wavelengths, and a new dual-wavelength photodetector served as a demultiplexing detector. The effect of interchannel interference on error rate was measured.
Step and frequency responses of c.t.d.s with nonuniform transfer inefficiency
- Author(s): Radu M. Barsan
- Source: Electronics Letters, Volume 15, Issue 13, p. 389 –391
- DOI: 10.1049/el:19790281
- Type: Article
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p.
389
–391
(3)
General models for the small-signal step and frequency responses of charge-transfer devices with nonuniform inefficiency are derived. The case when the transfer inefficiency becomes position-dependent due to a nonuniform distribution of the background charge along the register is experimentally investigated using bucket-brigade delay lines as test vehicles.
Split-loop method for wide-range frequency synthesiser with good dynamic performance
- Author(s): M.J. Underhill and P.A. Jordan
- Source: Electronics Letters, Volume 15, Issue 13, p. 391 –393
- DOI: 10.1049/el:19790282
- Type: Article
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p.
391
–393
(3)
In a p.l.l. frequency synthesiser with a wide-range varactor-tuned oscillator, the proportional path gain can be made nearly constant by the split-loop method. Good dynamic performance is then maintained over the range despite any integral-path gain variation caused by a nonlinear varactor capacitance law.
Wideband frequency modulation of frequency synthesisers
- Author(s): M.J. Underhill and R.I.H. Scott
- Source: Electronics Letters, Volume 15, Issue 13, p. 393 –394
- DOI: 10.1049/el:19790283
- Type: Article
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p.
393
–394
(2)
Two-point frequency modulation gives a flat frequency response irrespective of the loop cutoff frequency of a p.l.l. digital frequency synthesiser. The spurious modulation components otherwise generated are also then suppressed. The modulation index is typically limited to Nπ where N is the divider ratio.
Total dispersion in step-index monomode fibres
- Author(s): C.R. South
- Source: Electronics Letters, Volume 15, Issue 13, p. 394 –395
- DOI: 10.1049/el:19790284
- Type: Article
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p.
394
–395
(2)
An algebraic solution is given to calculate the total dispersion coefficient for a step-index fundamental-mode waveguide at any normalised frequency in the range 2.5>v>1.5. Examples are shown about the dispersion minimum for germanium-doped silica fibres.
Zero total dispersion in step-index monomode fibres at 1.30 and 1.55 μm
- Author(s): K.I. White and B.P. Nelson
- Source: Electronics Letters, Volume 15, Issue 13, p. 396 –397
- DOI: 10.1049/el:19790285
- Type: Article
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p.
396
–397
(2)
The total dispersion of monomode fibres is resolved into its constituent parts. The use of waveguide dispersion to shift the zero dispersion point to longer wavelengths is described. The range of fibre parameters that give zero total dispersion at 1.3 or 1.55 μm are evaluated numerically for germania-doped silica. Comments are made on the consequences for jointing and microbending losses.
Filtering out intersymbol interference in spread-spectrum communication systems
- Author(s): L. Alcuri ; G. Mamola ; E. Randazzo
- Source: Electronics Letters, Volume 15, Issue 13, p. 397 –399
- DOI: 10.1049/el:19790286
- Type: Article
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p.
397
–399
(3)
In this letter the transfer characteristic of the optimum filter suitable for eliminating intersymbol interference in pseudo-noise spread-spectrum communication systems is determined. Such a characteristic is independent of the code sequence employed.
Sequential voltage-inversion principle for switched-capacitor filters
- Author(s): J. Pandel
- Source: Electronics Letters, Volume 15, Issue 13, p. 399 –400
- DOI: 10.1049/el:19790287
- Type: Article
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p.
399
–400
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For a special class of switched-capacitor filters, voltage-inverter switches are needed. It is shown how several voltage-inverter switches can be realised using only one operational amplifier.
Crosspolar performance of an elliptical corrugated-horn antenna
- Author(s): R.F.E. Guy and R.W. Ashton
- Source: Electronics Letters, Volume 15, Issue 13, p. 400 –402
- DOI: 10.1049/el:19790288
- Type: Article
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p.
400
–402
(3)
Details are given of a corrugated-horn antenna of elliptical cross-section and its electrical performance. It is shown that this type of horn is suitable for use in systems where a high degree of polarisation purity is required in both planes of polarisation.
Fault detection in Moore-model sequential machine using counter-cycle technique
- Author(s): A. Bhattacharyya
- Source: Electronics Letters, Volume 15, Issue 13, p. 402 –403
- DOI: 10.1049/el:19790289
- Type: Article
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p.
402
–403
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The letter considers the applicability of the counter-cycle technique for the fault detection of a Moore-model sequential machine. It also covers the types of faults that may increase the number of states of the machine.
W-band two-diode power combiner
- Author(s): K. Chang ; R. Ebert ; C. Sun
- Source: Electronics Letters, Volume 15, Issue 13, p. 403 –405
- DOI: 10.1049/el:19790290
- Type: Article
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p.
403
–405
(3)
Two-diode power combiners have been developed to generate high-pulsed power in W-band. Two diodes were operated with 100 ns pulse width and 0.5% duty cycle. Peak combined power output of 20.5 W with 82% combining efficiency has been achieved.
High-linearity multimode optical fibre sensor
- Author(s): T.J. Hall
- Source: Electronics Letters, Volume 15, Issue 13, p. 405 –406
- DOI: 10.1049/el:19790291
- Type: Article
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p.
405
–406
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Experimental evidence is presented which demonstrates that a multimode optical fibre sensor can have a performance comparing favourably with that of a monomode optical fibre sensor. This is achieved by judicious choice of detection technique and by the manner in which the fibre is strained.
Two-stage amplifier utilising GaAs active-medium-propagation devices
- Author(s): P.L. Fleming and H.E. Carlson
- Source: Electronics Letters, Volume 15, Issue 13, p. 406 –407
- DOI: 10.1049/el:19790292
- Type: Article
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p.
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–407
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This letter describes a practical 2-stage amplifier utilising active-medium-propagation (a.m.p.) devices. The unit is centred at 14.7 GHz with a 500 MHz bandwidth and 15 dB external gain. Comparable f.e.t. devices require ≈ 0.5 μm gate dimensions whereas the GaAs a.m.p. is fabricated with a 5.0 μm gap.
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