Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 18, Issue 11, 27 May 1982
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Volume 18, Issue 11
27 May 1982
Measurements substantiating localised microwave hyperthermia within a thorax phantom
- Author(s): M. Melek ; A.P. Anderson ; B.H. Brown ; J. Conway
- Source: Electronics Letters, Volume 18, Issue 11, p. 437 –438
- DOI: 10.1049/el:19820297
- Type: Article
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Computer simulations of remotely induced microwave hyperthermia for selective tumour destruction are validated experimentally. This letter shows the first practical measurements of a focused microwave intensity distribution inside a thorax phantom irradiated from a microwave array of 11 elements.
Polarisation characteristics of a travelling-wave-type semiconductor laser amplifier
- Author(s): J.C. Simon
- Source: Electronics Letters, Volume 18, Issue 11, p. 438 –439
- DOI: 10.1049/el:19820298
- Type: Article
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We report experimental results on the gain sensitivity of a travelling-wave-type (TW) AlGaAs semiconductor laser amplifier to the input signal polarisation state.
Improvements to a surface-wave antenna measurement range with troublesome site effects
- Author(s): K.M. Keen ; R.R. Grime ; B.E. Stemp
- Source: Electronics Letters, Volume 18, Issue 11, p. 439 –440
- DOI: 10.1049/el:19820299
- Type: Article
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–440
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A surface-wave antenna measurement range used for ship antenna modelling work has been improved by the development of a novel source antenna. The antenna, a large ‘half-truncated’ corner reflector, has reduced unwanted range reflections to allow phase measurements to be made to an accuracy of approximately ±2°. Also, the screening effect of the reflector allows an adjacent range on the same reflecting ground plane to be operated simultaneously without noticeable effect on the surface-wave range performance.
Finite-element analysis of birefringence in azymuthally inhomogeneous optical fibre
- Author(s): P.L. Chu ; P.Y.P. Chen ; R.A. Sammut
- Source: Electronics Letters, Volume 18, Issue 11, p. 441 –442
- DOI: 10.1049/el:19820300
- Type: Article
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This communication reports the existence of a general purpose finite-element analysis program which can be used for the analysis of stress-induced birefringence in a single-mode optical fibre. This is applied to the azimuthally inhomogeneous fibre and it is found that the stress-induced birefringence is an order of magnitude larger than the geometric birefringence in the vicinity of V = 2. Maximum birefringence occurs when equal segments of different indices are used in the core.
Improving the linearity of piezoelectric ceramic actuators
- Author(s): C.V. Newcomb and I. Flinn
- Source: Electronics Letters, Volume 18, Issue 11, p. 442 –444
- DOI: 10.1049/el:19820301
- Type: Article
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It is shown that the linearity of a piezoelectric ceramic actuator may be greatly improved if the applied electric charge, rather than the applied voltage, is varied to control the extension. Hysteresis is virtually eliminated.
2-phase circulating shift register for switched-capacitor N-path filters
- Author(s): H.C. Patangia and J. Cartinhour
- Source: Electronics Letters, Volume 18, Issue 11, p. 444 –445
- DOI: 10.1049/el:19820302
- Type: Article
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A novel circulating shift register for switched-capacitor N-path filters is presented. The configuration affords a means of increasing the allowable discharge time for the shift register capacitors and eliminates clock feedthrough at the signal frequency. The shift register employs a simple 2-phase clock signal for any number of paths.
102 km unrepeatered monomode fibre system experiment at 140 Mbit/s with an injection locked 1.52 μm laser transmitter
- Author(s): D.J. Malyon and A.P. McDonna
- Source: Electronics Letters, Volume 18, Issue 11, p. 445 –447
- DOI: 10.1049/el:19820303
- Type: Article
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An experiment has been performed over 102 km of low-loss monomode fibre at 140 Mbit/s using an injection-locked source at 1.52 μm. The experiment showed that long-haul unrepeatered transmission is possible with nonzero-dispersion shifted fibre using narrow-linewidth laser transmitters.
Fused conically tapered fibre-optical power divider
- Author(s): E.G. Rawson and M.D. Bailey
- Source: Electronics Letters, Volume 18, Issue 11, p. 447 –448
- DOI: 10.1049/el:19820304
- Type: Article
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We describe a novel, conically tapered fibre-optical power divider which substantially increases the usable power of an LED source and provides highly homogeneous power division among the output fibres. Such devices are of use in optical signal distribution systems such as fibre-optical local computer networks. The performance of a 25-fibre power divider is described.
Power spectrum of microbends in monomode optical fibres
- Author(s): K.J. Blow ; N.J. Doran ; S. Hornung
- Source: Electronics Letters, Volume 18, Issue 11, p. 448 –450
- DOI: 10.1049/el:19820305
- Type: Article
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A new model is proposed for the power spectrum of microbends in monomode optical fibres. This model is based on the idea that microbends are extended rather than point, as has been previously assumed. By fitting our model to the experimental data we obtain values for the wavelength and correlation length of the disturbance causing the microbends.
Material dispersion slope in optical-fibre waveguides
- Author(s): K. Nassau and S.H. Wemple
- Source: Electronics Letters, Volume 18, Issue 11, p. 450 –451
- DOI: 10.1049/el:19820306
- Type: Article
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The slope of the material dispersion dM/dλ at λ0, the material dispersion zero where d2n/dλ2=0, can be calculated to yield values applicable to crystals and glasses. The results, in units of ps/nm km μm, range from 217 for B2O3 and 105 for SiO2 to 9 for TI2O and 0.40 for TlI. The key parameters affecting the material dispersion slope at λ0 are the chemical valence of the anion, the reduced mass and the density.
Temperature dependence of threshold current of GaAs quantum well lasers
- Author(s): N.K. Dutta
- Source: Electronics Letters, Volume 18, Issue 11, p. 451 –453
- DOI: 10.1049/el:19820307
- Type: Article
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The radiative recombination rate in a quantum well structure is calculated using a constant density of states and the k-selection rule. This calculation shows that the threshold current of a GaAs quantum well laser has low temperature sensitivity (T0 ̃ 330 K for T > 300 K).
Experimental comparison of a germanium avalanche photodiode and InGaAs PINFET receiver for longer wavelength optical communication systems
- Author(s): D.R. Smith ; R.C. Hooper ; P.P. Smyth ; D. Wake
- Source: Electronics Letters, Volume 18, Issue 11, p. 453 –454
- DOI: 10.1049/el:19820308
- Type: Article
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–454
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The receiver sensitivity of an InGaAs PIN photodiode-GaAs MESFET hybrid optical receiver is compared experimentally with that of a germanium avalanche photodiode from 34 to 565 Mbit/s and over the temperature range 20 to 60°C.
Wide bandwidth, high-repetition-rate optoelectronic modulation of millimetre waves in GaAs waveguide
- Author(s): Ming G. Li ; Wei L. Cao ; Veerendra K. Mathur ; Chi H. Lee
- Source: Electronics Letters, Volume 18, Issue 11, p. 454 –456
- DOI: 10.1049/el:19820309
- Type: Article
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The generation of ultrashort, chirped and coherent millimetre-wave pulses by an optical method is reported. Using this technique, the modulation of millimetre-wave signals at 94 GHz with a modulation bandwidth in excess of 1 GHz is readily achievable.
Modification of shanks conjecture on stability of 2-D planar least-square inverse polynomials
- Author(s): P.S. Reddy ; D.R. Reddy ; M.N.S. Swamy
- Source: Electronics Letters, Volume 18, Issue 11, page: 456 –456
- DOI: 10.1049/el:19820310
- Type: Article
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In the letter we state a theorem modifying the Shanks conjecture on the stability of the planar least-square inverse of a 2-D polynomial based on our observation of various counterexamples.
Design of high-order filters with restricted component values
- Author(s): K. Ramakrishna and K. Rajgopal
- Source: Electronics Letters, Volume 18, Issue 11, p. 457 –458
- DOI: 10.1049/el:19820311
- Type: Article
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The feasibility of realising a high-order LC filter with a small set of different capacitor values, without sacrificing the frequency response specifications, is indicated. This idea could be conveniently adopted in other filter structures also—for example the FDNR transformed filter realisations.
1.5 μm GaInAsP/InP distributed Bragg reflector lasers with built-in optical waveguide
- Author(s): O. Mikami ; T. Saitoh ; H. Nakagome
- Source: Electronics Letters, Volume 18, Issue 11, p. 458 –460
- DOI: 10.1049/el:19820312
- Type: Article
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Room-temperature operation of distributed Bragg reflector (DBR) lasers emitting at 1.5 μm is reported. The diode was fabricated by conventional techniques and has a simple configuration with a built-in waveguide grown by single-step liquid-phase epitaxy. Single-longitudinal-mode oscillation at 1.504–1.505 μm was obtained at temperatures between −10°C and 5°C with 310–360 mA threshold current.
Empirical model for rainfall rate distribution
- Author(s): F. Moupfouma and J. Dereffye
- Source: Electronics Letters, Volume 18, Issue 11, p. 460 –461
- DOI: 10.1049/el:19820313
- Type: Article
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An empirical but theoretically sound law derived from rainfall measurements obtained in the Congo (tropical and equatorial climates), and which provides a good fit of rainfall rate distributions observed in various hydrometeorological zones of the world, is presented. This rainfall rate distribution model is compared with the gamma and log-normal ones.
Surface-emitting GaInAsP/InP injection laser with short cavity length
- Author(s): Y. Motegi ; H. Soda ; K. Iga
- Source: Electronics Letters, Volume 18, Issue 11, p. 461 –463
- DOI: 10.1049/el:19820314
- Type: Article
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We have succeeded in making a surface-emitting GaInAsP/InP injection laser with short cavity length (≅ 10 μm) which operates at 1.22 μm of wavelength with threshold current of 160 mA (33 kA/cm2) at 77 K. No side-emitting mode was observed as a result of preparing long absorbing regions and a small dot electrode (25 μm φ). One of the longitudinal modes, with a spacing of 170 Å, dominated above threshold and the far-field radiation angle was sharp (2Δθ = 10°).
Wave propagation in transversely inhomogeneous dielectric waveguide
- Author(s): J. Gomi ; T. Yoneyama ; S. Nishida
- Source: Electronics Letters, Volume 18, Issue 11, p. 463 –464
- DOI: 10.1049/el:19820315
- Type: Article
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Guided mode propagation in inhomogeneous dielectric waveguides is calculated by a series expansion method which is particularly useful for analysing single-mode dielectric waveguides. As an example we estimate the error in the phase constant of waveguides whose dielectric constant profile is not necessarily near-parabolic.
Microwave open resonator: a paradox
- Author(s): A.C. Lynch
- Source: Electronics Letters, Volume 18, Issue 11, p. 464 –465
- DOI: 10.1049/el:19820316
- Type: Article
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If a thin lens is placed in an open resonator, it does not refract if it is in a nodal plane, but at the maxima of the electric field it behaves like a lens having a refractive index greater than the true value.
Statistical analysis of instantaneous laser spectra
- Author(s): I.D. Henning and D.A. Frisch
- Source: Electronics Letters, Volume 18, Issue 11, p. 465 –466
- DOI: 10.1049/el:19820317
- Type: Article
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A statistical description of the pulse to pulse spectral variations of a semiconductor laser has been made using a technique which records the true instantaneous spectrum. Mode selection caused by external feedback has been examined.
Behaviour of spectrum-conserving RBQPSK digital radio during multipath propagation
- Author(s): G.D. Richman
- Source: Electronics Letters, Volume 18, Issue 11, p. 467 –468
- DOI: 10.1049/el:19820318
- Type: Article
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Studies indicate that reduced bandwidth quadrature phase-shift-keyed digital radio relay systems (RBQPSK) employing adaptive decision-feedback techniques have good spectrum utilisation efficiency coupled with robustness in the presence of distortion induced by multipath propagation. The letter discusses the practical confirmation of RBQPSK performance during multipath propagation on a 6 GHz, 51 km long test link in East Anglia.
Semiconductor laser FSK modulation and optical direct discrimination detection
- Author(s): S. Saito ; Y. Yamamoto ; T. Kimura
- Source: Electronics Letters, Volume 18, Issue 11, p. 468 –469
- DOI: 10.1049/el:19820319
- Type: Article
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FSK signals are generated in an AlGaAs double heterostructure laser by employing an electrical equalising circuit to compensate for its nonuniform FM modulation characteristics. A 10−9 bit error rate is achieved at a 100 Mbit/s data rate in the optical direct discrimination detection with a Michelson interferometer. The optical FSK discrimination detection performance is studied in terms of receiving signal power level and laser spectral linewidth.
Optical FSK signal detection in a heterodyne system using semiconductor lasers
- Author(s): S. Saito ; Y. Yamamoto ; T. Kimura
- Source: Electronics Letters, Volume 18, Issue 11, p. 470 –471
- DOI: 10.1049/el:19820320
- Type: Article
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A 10−8 bit error rate is achieved for 100 Mbit/s signals in an FSK heterodyne frequency-discrimination detection system, in which AlGaAs double-heterostructure lasers are used as both the FSK transmitter and the local oscillator. Receiving signal power level to achieve a low bit error rate is experimentally obtained, which confirms the principle of optical heterodyne detection. AM quantum noise in the laser local oscillator and FM quantum noise are important factors which determine the system performance.
W-band broadband integrated circuit mixers
- Author(s): R.S. Tahim ; G.M. Hayashibara ; K. Chang
- Source: Electronics Letters, Volume 18, Issue 11, p. 471 –473
- DOI: 10.1049/el:19820321
- Type: Article
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Broadband integrated circuit mixers using a crossbar stripline configuration and a finline configuration have been developed. For the crossbar stripline balanced mixer, less than 7.5 dB conversion loss for 15 GHz instantaneous IF bandwidth has been achieved with the LO at 75 GHz and the RF swept from 76 to 91 GHz. For the finline balanced mixer, a conversion loss of 9 to 12 dB over a 19 GHz instantaneous IF bandwidth has been achieved as the RF is swept from 91 to 110GHz.
Simple equivalent network for a rectangular dielectric image guide
- Author(s): M. Koshiba ; H. Ishii ; M. Suzuki
- Source: Electronics Letters, Volume 18, Issue 11, p. 473 –474
- DOI: 10.1049/el:19820322
- Type: Article
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The equivalent network approach is described for the analysis of the rectangular dielectric image guide. A network representation is derived by taking the discrete-continuous spectrum coupling at the sides of the waveguide into account. The results by this simple approach agree well with the point-matching results and the experimental results.
Determination of stress profiles in optical-fibre preforms
- Author(s): R.B. Calligaro ; D.N. Payne ; R.S. Anderssen ; B.A. Ellem
- Source: Electronics Letters, Volume 18, Issue 11, p. 474 –475
- DOI: 10.1049/el:19820323
- Type: Article
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A computational technique is presented for the nondestructive determination of the radial, axial and tangential stress profiles in optical-fibre preforms. Optical retardation which arises as a consequence of the photoelastic effect is the basis for the technique. The stress profiles are obtained by first evaluating and then numerically differentiating indefinite integrals defined on the optical retardation profiles.
Graphic image coding based on a pattern-dependent runlength model
- Author(s): Y.S. Shim and J.K. Kim
- Source: Electronics Letters, Volume 18, Issue 11, p. 476 –477
- DOI: 10.1049/el:19820324
- Type: Article
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A new graphic image coding based on a pattern-dependent runlength model is investigated. The binary image is considered as a concatenation of alternating white and black runs the probability of occurrence of which is dependent on the pattern of neighbouring runs. Based on this model, an optimum coding strategy is obtained for the case of simplified composite states. Simulation results show its better performance over conventional schemes.
Effects of filtering on rate of change of rain-induced attenuation
- Author(s): E. Matricciani
- Source: Electronics Letters, Volume 18, Issue 11, p. 477 –478
- DOI: 10.1049/el:19820325
- Type: Article
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Time series of rain attenuation on a slant path at 11.6 GHz are analysed with two digital filters to assess their influence on the statistics of the rate of change. It is found that the statistics depend on the measuring apparatus and that a normalisation to the median value reduces the dependence, efficiently permitting comparisons with statistics collected with different time resolutions. A cutoff in the rates is found at high attenuation level and the constancy of the log-normal variance found experimentally is discussed.
Utilisation d'un nouveau type de noeud dans la méthode TLM en 3 dimensions (Usage of a new type of node in the 3D TLM method)
- Author(s): P. Saguet and E. Pic
- Source: Electronics Letters, Volume 18, Issue 11, p. 478 –480
- DOI: 10.1049/el:19820326
- Type: Article
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Nous proposons l'utilisation d'un type de noeud unique dans la méthode TLM en 3 dimensions, à la place des noeuds ‘série’ et ‘shunt’ habituellement utilises. Le noeud présenté a l'avantage d'être ponctuel, ce qui donne une meilleure précision des résultats. Le temps de calcul nécessaire est moindre que dans la méthode originale et la programmation est simplifiée.In the three-dimensional TLM method, series and shunt nodes may be replaced by a single node type. This new node acts as a point rather than as a cell, thus increasing the accuracy of the computational results. Computation time is reduced as compared to the original method, and the programming work is simpler.
Root-locus plot of systems with time delay
- Author(s): K.S. Yeung and W.T. Wong
- Source: Electronics Letters, Volume 18, Issue 11, p. 480 –481
- DOI: 10.1049/el:19820327
- Type: Article
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An existing root-locus technique for linear finite-dimensional systems is modified and adapted to the case of systems with time delay. By means of the modified approach, root loci of time-delay systems can be numerically computed in a simple manner without having to solve transcendental equations. An example is given to show the effectiveness of the method.
Simple model for threshold voltage of a nonuniformly doped short-channel MOS transistor
- Author(s): A.M. Asenov
- Source: Electronics Letters, Volume 18, Issue 11, p. 481 –483
- DOI: 10.1049/el:19820328
- Type: Article
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In this letter a simple geometric model for evaluating the threshold voltage of an ion-implanted short-channel MOS transistor, taking into account the form of the depletion regions around the source and drain p-n junctions, is presented. The model displays good agreement between the theoretical and experimental results and can be employed for sensitivity evaluation and optimisation of the threshold voltage.
Characteristics of light induced annealing in irradiated optical fibres
- Author(s): R.H. West and A.P. Lenham
- Source: Electronics Letters, Volume 18, Issue 11, p. 483 –484
- DOI: 10.1049/el:19820329
- Type: Article
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Transmission losses produced in fibre-optics by ionising radiation may be annealed by the signal light. Results are presented for the dependence of the effect on the light power level and its wavelength. Losses which are thus annealed appear to be related to strain in the fibre.
Sensitivity to geometrical parameters in a dispersion-free multicomponent fibre
- Author(s): P.L. Francois
- Source: Electronics Letters, Volume 18, Issue 11, p. 484 –486
- DOI: 10.1049/el:19820330
- Type: Article
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A general expression for the dispersion coefficient in a multi-component structure is derived and applied to step-index fibres with depressed inner cladding. The fundamental mode spot size and the sensitivity to a change in index differences, core radius and wavelength are then evaluated in the case of dispersion-free propagation.
Analysis of rain attenuation models for slant path
- Author(s): G. Macchiarella
- Source: Electronics Letters, Volume 18, Issue 11, p. 486 –487
- DOI: 10.1049/el:19820331
- Type: Article
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Several methods for computing the cumulative distribution of rain attenuation for slant paths have been tested at three different locations in Italy. The results have been compared with the measured attenuation at 11.6 GHz through the Sirio satellite beacon, and the behaviour of each model has been investigated.
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