Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 14, Issue 19, 14 September 1978
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Volume 14, Issue 19
14 September 1978
Multiple canonic RLC ladder synthesis of biquadratic immittance functions with double poles and complex zeros
- Author(s): S. Tirtoprodjo and P. van Beers
- Source: Electronics Letters, Volume 14, Issue 19, p. 607 –608
- DOI: 10.1049/el:19780408
- Type: Article
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Sufficient conditions for the precise location of the complex zeros of a subclass of biquadratic immittance functions are derived, such that at least one canonic RLC ladder realisation exists. The synthesis is performed on immittance functions having normalised real double poles. However, an indication is provided on how to extend the proposed procedure to encompass biquadratic functions with complex poles or real single poles.
Scaling of contour-coded binary images
- Author(s): Piero Zamperoni
- Source: Electronics Letters, Volume 14, Issue 19, p. 608 –610
- DOI: 10.1049/el:19780409
- Type: Article
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Contour-coded binary images on a discrete square grid can be expanded by means of a simple numerical manipulation of their chain code if they are first decomposed into elementary convex patterns. This approach avoids several shape-interpretation problems, arising with arbitrary blobs, and reduces geometrical distortions to a minimum.
Sliding mean edge estimation
- Author(s): Gary E. Ford
- Source: Electronics Letters, Volume 14, Issue 19, p. 610 –611
- DOI: 10.1049/el:19780410
- Type: Article
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p.
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–611
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A new algorithm is presented for the determination of the locations of major edges in a noisy image based, in part, on the approach of maximum-likelihood estimation.
Single-mode fibre connectors
- Author(s): Nobuo Shimizu and Haruhiko Tsuchiya
- Source: Electronics Letters, Volume 14, Issue 19, p. 611 –613
- DOI: 10.1049/el:19780411
- Type: Article
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A low-loss detachable connector has been fabricated for single-mode optical fibres. It consists of a pair of plugs accommodating fibres to be joined and a sleeve provided with ball-bearing arrays to align the plugs. The average connecting loss is reduced to as low as 0.5 dB, including fibre end reflection.
Mechanical strength of fusion-spliced optical fibres
- Author(s): Iwao Hatakeyama ; Masao Tachikura ; Haruhiko Tsuchiya
- Source: Electronics Letters, Volume 14, Issue 19, p. 613 –614
- DOI: 10.1049/el:19780412
- Type: Article
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Mechanical strengths of optical fibres heated under different electric-discharge conditions have been systematically examined. Exclusion of fibre surface contaminations and making heating duration as short as possible are important for prevention of strength deterioration.
Electric/magnetic field ratios of ground waves in a realistic terrain
- Author(s): J.H. Causebrook
- Source: Electronics Letters, Volume 14, Issue 19, p. 614 –615
- DOI: 10.1049/el:19780413
- Type: Article
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–615
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An investigation of ground waves at low and medium frequencies has shown that in cluttered or undulating terrain the electric field is reduced relative to the magnetic field. This reduction applies to the median value over large areas and has different characteristics dependent on type of terrain factor (buildings, trees or undulatlons).
Multiplier for delta-modulated signals
- Author(s): D. Lagoyannis
- Source: Electronics Letters, Volume 14, Issue 19, p. 615 –616
- DOI: 10.1049/el:19780414
- Type: Article
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A new method for multiplying delta-modulated signals by a constant is suggeated. The rate multiplier is employed here for this multiplication.
Slotted waveguide linear array with polarisation control
- Author(s): A.J. Sangster
- Source: Electronics Letters, Volume 14, Issue 19, p. 616 –618
- DOI: 10.1049/el:19780415
- Type: Article
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The design of an experimental dual-mode waveguide linear array antenna is described and measurements on a 10-element model are presented. The antenna comprises a ‘notched’ wall dual-mode waveguide containing an array of suitably located transverse/longitudinal slot pairs. Polarisation control is achieved by feeding the array through a 3 dB hybrid followed by a phase shifter.
Zero-mode dispersion in single-mode fibres
- Author(s): W.A. Gambling ; H. Matsumura ; C.M. Ragdale
- Source: Electronics Letters, Volume 14, Issue 19, p. 618 –620
- DOI: 10.1049/el:19780416
- Type: Article
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Near cutoff the loss of the LP11-mode in cladded optical fibres becomes very high in the presence of even slight bends. Singlemode operation can thus be achieved with zero-mode dispersion as well as zero material dispersion, thus promising enormously large bandwidths.
Interaction of high-frequency sound with fibre-guided coherent light
- Author(s): D. Howard and T.J. Hall
- Source: Electronics Letters, Volume 14, Issue 19, p. 620 –621
- DOI: 10.1049/el:19780417
- Type: Article
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Variations in mechanical stress applied to an optical fibre result in a phase modulation of coherent light propagating along the fibre. Mechanical vibration modes of the fibre have been found to play an important role in this process. This letter describes the effect of these vibration modes and presents experimental evidence of the accentuation of the phase modulation due to one of these modes.
Deep traps in polysilicon solar cells
- Author(s): A. Criado ; B. Alonso ; J. Piqueras
- Source: Electronics Letters, Volume 14, Issue 19, p. 622 –623
- DOI: 10.1049/el:19780418
- Type: Article
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Anomalously high values of the ideality parameter n have been found in n+−p diffused polysilicon solar cells indicating large generation-recombination rates in the space-charge layers. Two electron traps situated at 0.46 ± 0.03 eV and 0.12 ± 0.02 eV below the conduction-band edge seem to be responsible for these large generation-recombination currents. Because the concentration profiles of both levels are very similar, both can be attributed to the same defect.
Magnetoresistive class-C frequency multipliers
- Author(s): V. Dey and D. Midgley
- Source: Electronics Letters, Volume 14, Issue 19, p. 623 –624
- DOI: 10.1049/el:19780419
- Type: Article
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Experimental frequency-multiplier circuits are described. For the generation of odd harmonics an unconventional circuit exploits the bidirectional property of the magnetoresistor. For even harmonics a conventional circuit is found to be capable of high efficiency (>70%) for a modest change in magnetoresistance (factor 6).
One-parameter adoptive cancellation for satellite microwave links
- Author(s): N.J. McEwan and M.S. Mahmoud
- Source: Electronics Letters, Volume 14, Issue 19, p. 624 –625
- DOI: 10.1049/el:19780420
- Type: Article
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For dual linearly polarised microwave links (especially to satellites), in situations where differential phase shift is the dominant cause of crosspolarisation, it is proposed to perform adaptive cancellation of crosspolarisation by means of a simplified network having only one variable parameter. A possible construction of the device is suggested and its performance in various situations assessed.
Optical injection locking of impatt oscillators
- Author(s): J.R. Forrest and A.J. Seeds
- Source: Electronics Letters, Volume 14, Issue 19, p. 626 –627
- DOI: 10.1049/el:19780421
- Type: Article
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A method for locking impatt oscillators by illuminating the impatt diode with a low-power laser beam, amplitude modulated at microwave frequency, is described. A large-signal theory of impatt operation, including the effects of finite reverse saturation currents and their modulation by the laser beam, is presented and predicts locking ranges of several tens of MHz with laser powers of a few mW
Explicit modelling of antennas with sparse-ground screens
- Author(s): E.K. Miller ; J.N. Brittingham ; J.T. Okada
- Source: Electronics Letters, Volume 14, Issue 19, p. 627 –629
- DOI: 10.1049/el:19780422
- Type: Article
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Recently we reported a numerical technique that uses interpolation to provide the Sommerfeld-integral values needed for a moment-method model of objects located near an interface. Here we use that technique to evaluate the characteristics of a vertical monopole connected to one to three ground-screen wires elevated 0.01λ above a lossy ground.
Inductance simulation and filter design using a single-pole amplifier approximation
- Author(s): J. Allen ; M. Gumussoy ; A.G.J. Holt
- Source: Electronics Letters, Volume 14, Issue 19, p. 629 –631
- DOI: 10.1049/el:19780423
- Type: Article
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By assuming the operational amplifier can be represented by a single-pole model, a very simple circuit has been developed to replace grounded inductors in ladder filters. The resulting active filters can be used at high frequencies and produce very little noise at their outputs.
True quadrature taps for s.a.w. delay lines
- Author(s): R.J. Murray ; R.C. Peach ; S. Neylon
- Source: Electronics Letters, Volume 14, Issue 19, p. 631 –632
- DOI: 10.1049/el:19780424
- Type: Article
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A novel technique is described in which a combination of geometrically symmetric and antisymmetric interdigital transducers may be employed to produce a constant 90° phase difference between two taps on a surface-acoustic-wave delay line. This relative phase difference is maintained at 90° over the whole transducer bandwidth.
Realisation of grounded capacitor with operational amplifiers and resistance
- Author(s): Muzafier A. Siddiqi and T. Muslim Ahmed
- Source: Electronics Letters, Volume 14, Issue 19, p. 633 –634
- DOI: 10.1049/el:19780425
- Type: Article
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A simple circuit is given for the simulation of a high-quality grounded capacitor. It uses only two operational amplifiers and one resistance. Experimental results are included.
Fast-Fourier-transform processor using s.a.w. chirp filters
- Author(s): M.A. Jack
- Source: Electronics Letters, Volume 14, Issue 19, p. 634 –635
- DOI: 10.1049/el:19780426
- Type: Article
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–635
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A fast-Fourier-transform (f.f.t.) processor based on the chirp transform algorithm implemented with surface-acoustic-wave (s.a.w.) chirp filters is reported. Using commercially available s.a.w. devices the processor computes a 128-point (nominal) f.f.t. in 25 μs, permitting real-time operation over 4 MHz bandwidth. Experimental results showing operation with sine and cosine inputs demonstrate processor performance in computing real and imaginary Fourier-transform components to an accuracy equivalent to 6 bits.
Computer studies on the widening of the avalanche zone and the decrease in efficiency of silicon X-band symmetrical double-drift impatt diodes at high current densities
- Author(s): M. Sridharan and S.K. Roy
- Source: Electronics Letters, Volume 14, Issue 19, p. 635 –637
- DOI: 10.1049/el:19780427
- Type: Article
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A computer study of the field and current profiles of silicon X-band symmetrical d.d.r. impatt diodes is presented. The results show that there is considerable widening of the avalanche zone at high values of current density. This causes a sharp fall in the efficiency of the device at high current density after reaching a maximum.
Effect of neutron and gamma irradiation on the low-frequency noise in GaAs m.e.s.f.e.t.s
- Author(s): S.B. Moghe ; R.J. Gutmann ; M.J. Chudzicki ; J.M. Borrego
- Source: Electronics Letters, Volume 14, Issue 19, p. 637 –639
- DOI: 10.1049/el:19780428
- Type: Article
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Low-frequency noise in GaAs m.e.s.f.e.t.s has been measured from 2 kHz to 1.5 MHz as a function of fast neutron fluence and gamma dose. From 5 × 1013 to 8 × 1014 n/cm2, the noise increases appreciably, with the noise enhancement from 2 to 10 kHz attributed to generation-recombination noise in the gate depletion layer and from 500 kHz to 1.5 MHz to channel trapping effects. There was comparably little change with gamma irradiation up to doses above 107 rad (Si).
Determination of arbitrary doping profile in p–n junctions
- Author(s): D.A. Tjapkin and V.B. Milanović
- Source: Electronics Letters, Volume 14, Issue 19, p. 639 –640
- DOI: 10.1049/el:19780429
- Type: Article
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Measurements of the depletion-layer capacitance as a function of both voltage and temperature enable the determination of an arbitrary profile for any ratio of Nd/Na. The proposed method is valuable for the determination of temperature dependences of relative permittivity and built-in voltage.
Modulation of room-temperature GaAs lasers at X-band frequencies
- Author(s): Mysore R. Lakshminarayana ; Robert G. Hunsperger ; Larry D. Partain
- Source: Electronics Letters, Volume 14, Issue 19, p. 640 –641
- DOI: 10.1049/el:19780430
- Type: Article
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GaAs lasers operating at room temperature are directly modulated at X-band frequencies. A fast silicon avalanche photodiode is used to demodulate the laser light.
Number of minimum-weight code words in a product code
- Author(s): R.L. Miller
- Source: Electronics Letters, Volume 14, Issue 19, p. 642 –643
- DOI: 10.1049/el:19780431
- Type: Article
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It is well known that if the linear code Ci over GF(q) has ωi words of minimum weight Wi (1 ≤ i ≤ t), then the product C = C1 ⊗ C2⊗…⊗Ct has minimum weight w1w2…Wt. In this letter it is shown that C has exactly ω1 ω2… ωt/(q − 1)t−1 such minimum-weight code words. Moreover, if v∈C has weight w1w2…wt then v = v1 ⊗ v2 ⊗ … ⊗ vt where vi is a word of Ci with weight wi (1 ≤i≤t).
Enhancement-mode ion-implanted InP f.e.t.s
- Author(s): K.R. Gleason ; H.B. Dietrich ; M.L. Bark ; R.L. Henry
- Source: Electronics Letters, Volume 14, Issue 19, p. 643 –644
- DOI: 10.1049/el:19780432
- Type: Article
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Planar enhancement-mode InP f.e.t.s have been fabricated through the use of ion implantation and subsequent electron-beam lithography. Noise figures of 3.2 and 2.6 dB were achieved at 8 GHz with associated gains of 6.4 and 4.7 dB, respectively.
Insular-image guide-fed short backfire antenna
- Author(s): R.N. Simons and D.T. Shahani
- Source: Electronics Letters, Volume 14, Issue 19, p. 644 –645
- DOI: 10.1049/el:19780433
- Type: Article
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A short backfire antenna using an insular-image waveguide feed that is compatible with the microwave dielectric integrated-circuit technology is presented. The antenna is made feasible by providing an annular gap between the insular image guide and the metal reflector at the feed point. The important parameters of the antenna are experimentally optimised to give a maximum gain of 12.5 dB at the design frequency of 10 GHz. The measured radiation patterns are compared with the theoretical patterns computed from the near-field amplitude distribution. This type of antenna can find extensive applications at millimetre-wave frequencies.
Least-squares algorithm for the design of digital 2-dimensional allpass filters
- Author(s): G.L. Sicuranza
- Source: Electronics Letters, Volume 14, Issue 19, p. 645 –647
- DOI: 10.1049/el:19780434
- Type: Article
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–647
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A least-squares-approximation technique for the design of digital 2-dimensional allpass filters is described. The method allows the phase equalisation of low- or highpass filters with symmetrical amplitude response.
Calculation of reference equivalents and loudness ratings
- Author(s): D.L. Richards
- Source: Electronics Letters, Volume 14, Issue 19, p. 647 –649
- DOI: 10.1049/el:19780435
- Type: Article
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A new algorithm is proposed that enables reference equivalents to be calculated instead of having to be determined by subjective measurements.
Spectral and transient response of low-threshold proton-isolated (GaAl)as lasers
- Author(s): M.R. Matthews and A.G. Steventon
- Source: Electronics Letters, Volume 14, Issue 19, p. 649 –651
- DOI: 10.1049/el:19780436
- Type: Article
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Optimisation of the (GaAl)As laser to achieve a low threshold current leads to the suppression of relaxation oscillations and a consequent reduction, not previously reported, in the spectral broadening under pulse conditions. In this letter we describe lasers having these characteristics and their advantages for optical-fibre communications systems.
Computation of optimal piecewise-linear feedback gains for linear regulators
- Author(s): P.J. Fleming
- Source: Electronics Letters, Volume 14, Issue 19, p. 651 –653
- DOI: 10.1049/el:19780437
- Type: Article
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For finite-time linear regulator problems, it is shown that the optimal piecewise-constant feedback gains can be computed using a gradient minimisation technique. Employing this approach the following two schemes are considered: (a) simultaneous optimisation of switching times and (b) determination of optimal piecewise-linear feedback gains. Computational results are presented.
Random bend losses in single-mode optical-fibre cables: power-spectrum estimation from spectral losses
- Author(s): Kazuhito Furuya and Yasuharu Suematsu
- Source: Electronics Letters, Volume 14, Issue 19, p. 653 –654
- DOI: 10.1049/el:19780438
- Type: Article
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For single-mode optical-fibre cables, power spectra of random bends were estimated to be Gaussian with correlation lengths of around 1 mm. The method was to fit measured curves of loss against wavelength to theoretical ones.
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