Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 17, Issue 17, 20 August 1981
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Volume 17, Issue 17
20 August 1981
Fibre-optic spectrophone
- Author(s): D.H. Leslie ; G.L. Trusty ; A. Dandridge ; T.G. Giallorenzi
- Source: Electronics Letters, Volume 17, Issue 17, p. 581 –582
- DOI: 10.1049/el:19810409
- Type: Article
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The first operation of a fibre-optic spectrophone is reported. A 2.54 cm diameter coil of single-mode fibre was fused into one arm of an all-fibre Mach-Zehnder interferometer. The device operated as a highly sensitive optoacoustic detector.
Crystallographic facets chemically etched in GaInAsP/InP for integrated optics
- Author(s): K. Furuya ; L.A. Coldren ; B.I. Miller ; J.A. Rentschler
- Source: Electronics Letters, Volume 17, Issue 17, p. 582 –583
- DOI: 10.1049/el:19810410
- Type: Article
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Vertical crystallographic (011) planes were exposed on (100) GaInAsP/InP double heterostructures (DH) by a newly developed chemical etchant and method. This method provides optically flat, mirror quality facets reproducibly and could be very attractive in integrated optics and optoelectronic devices.
Encryption with keyed random permutations
- Author(s): F. Ayoub
- Source: Electronics Letters, Volume 17, Issue 17, p. 583 –585
- DOI: 10.1049/el:19810411
- Type: Article
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583
–585
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A method is presented to generate a keyed random permutation (for example when enciphering a block of binary data) using the theoretical minimum number of key bits. The method is especially useful in an environment with limited key supply. An algorithm for implementing the method is given, with an estimate of its complexity.
Investigation of crosspolarisation in offset Cassegrain antennas
- Author(s): T.S. Bird
- Source: Electronics Letters, Volume 17, Issue 17, p. 585 –586
- DOI: 10.1049/el:19810412
- Type: Article
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585
–586
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The geometric optics condition for zero crosspolarisation in offset Cassegrain antennas is discussed. It is shown that with a feed having perfect pattern symmetry the crosspolar performance of the offset Cassegrain is limited by diffraction. As a result minimum crosspolarisation is only achieved at the geometric optics condition when the subreflector diameter is at least 40 wavelengths.
Low-temperature process to increase the grain size in polysilicon films
- Author(s): R. Reif and J.E. Knott
- Source: Electronics Letters, Volume 17, Issue 17, p. 586 –588
- DOI: 10.1049/el:19810413
- Type: Article
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–588
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The letter describes a novel process for increasing the grain size in polycrystalline silicon films at temperatures near 500°C. This process, once perfected, could lead to mono-crystalline or large-grain, uniformly oriented polysilicon films on amorphous surfaces.
Finite-element analysis of angularly dependent modes in a general RF periodic cavity
- Author(s): G.Y. Philippou ; G.S. Gupta ; J.B. Davies
- Source: Electronics Letters, Volume 17, Issue 17, p. 588 –589
- DOI: 10.1049/el:19810414
- Type: Article
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–589
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An analysis is presented for a circularly symmetric periodic structure for any angular dependence of the modes. The finite-element technique is applied and computations for the simple case of an iris loaded circular waveguide are compared with previously published results.
Oscillation frequency, linewidth reduction and frequency modulation characteristics for a diode laser with external grating feedback
- Author(s): O. Nilsson ; S. Saito ; Y. Yamamoto
- Source: Electronics Letters, Volume 17, Issue 17, p. 589 –591
- DOI: 10.1049/el:19810415
- Type: Article
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–591
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Simple analytical expressions are given for the oscillation frequency, linewidth, FM noise spectrum and frequency modulation characteristics of a diode laser with external grating feedback. The analytical expressions are found to be in good agreement with experimental results and to be useful for quantitative predictions and optimisations of the external feedback controlled diode laser performance.
Fluoride-glass-cladded optical fibres for mid-infra-red ray transmission
- Author(s): S. Mitachi ; T. Miyashita ; T. Kanamori
- Source: Electronics Letters, Volume 17, Issue 17, p. 591 –592
- DOI: 10.1049/el:19810416
- Type: Article
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–592
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Cladded-type fluoride glass fibres with a transmission loss of 0.1 dB/m at 2.5 μm and 0.3 dB/m at 3.6 μm, respectively, were fabricated by a novel casting method. Relative refractive-index differences between core and cladding ranging from 0.17% to 0.33% were obtained using BaF2-GdF3-ZrF4-AlF3 glasses as core and cladding components.
Fibre-length dependence of critical power for stimulated Raman scattering
- Author(s): Y. Ohmori ; Y. Sasaki ; T. Edahiro
- Source: Electronics Letters, Volume 17, Issue 17, p. 593 –594
- DOI: 10.1049/el:19810417
- Type: Article
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–594
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The fibre-length dependence of critical powers, at which Stokes lights begin to build up, is investigated on stimulated Raman scattering in single-mode fibres. A mode-locked and Q-switched Nd:YAG laser is used as a pumping laser. The critical powers for the first five Stokes decrease with an increase in the length of fibre and become constant above 200 m long. The critical powers of 8 W, 20 W, 30 W, 53 W and 73 W for 1st, 2nd, 3rd, 4th and 5th Stokes, respectively, are obtained for fibres longer than 200 m.
Single-pass Raman generation pumped by a mode-locked laser
- Author(s): Y. Ohmori ; Y. Sasaki ; M. Kawachi ; T. Edahiro
- Source: Electronics Letters, Volume 17, Issue 17, p. 594 –596
- DOI: 10.1049/el:19810418
- Type: Article
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–596
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Single-pass Raman generation pumped by a mode-locked Nd:YAG laser is investigated for long-span and low-loss fibres. The peak wavelength of the first Stokes jumps dramatically from 1.114 μm to 1.12 μm at 1.65 W average input power. The first Stokes increases rapidly between the inputs of 1.65 W and 2.1 W. These characteristics of single-pass stimulated Raman scattering are discussed in terms of group velocity matching.
Measurement of magnetic field by polarisation optical time-domain reflectometry
- Author(s): J.N. Ross
- Source: Electronics Letters, Volume 17, Issue 17, p. 596 –597
- DOI: 10.1049/el:19810419
- Type: Article
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p.
596
–597
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The technique of polarisation optical time-domain reflectometry has been used to measure magnetic field through the use of the Faraday effect. A spatial resolution of 0.4 m was achieved, and a sensitivity corresponding to a magnetic field of 10−3 T over a length of 0.5 m was obtained.
Room temperature CW operation of GaInAsP/InP double-heterostructure diode lasers emitting at 1.23 μm grown by low-pressure metalorganic chemical vapour deposition
- Author(s): M. Razeghi ; J.P. Hirtz ; P. Hirtz ; J.P. Larivain ; R. Bondeau ; B. de Cremoux ; J.P. Duchemin
- Source: Electronics Letters, Volume 17, Issue 17, p. 597 –598
- DOI: 10.1049/el:19810420
- Type: Article
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597
–598
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We report the first successful room-temperature CW operation of GaInAsP/InP DH lasers emitting at 1.23 μm grown by LP MOCVD. Current thresholds as low as 250 mA have been obtained for CW operation.
Formulation of electric-field integral equation without use of differential operator
- Author(s): C.J. O'Neill ; T. Downs ; P.J. Khan
- Source: Electronics Letters, Volume 17, Issue 17, p. 598 –600
- DOI: 10.1049/el:19810421
- Type: Article
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p.
598
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(3)
We derive a new formulation of the electric-field integral equation for the surface current density on an infinitely long conducting strip, with a TE incident field. The formulation avoids the use of a differential operator, allows numerical solution using pulse basis functions and point matching, and is applicable to any two-dimensional scatterer. Our approach is readily extendable to three-dimensional problems.
Real-time programmable unit-element SC filter for LPC synthesis
- Author(s): U. Kleine ; D. Herbst ; B. Hoefflinger ; B.J. Hosticka ; R. Schweer
- Source: Electronics Letters, Volume 17, Issue 17, p. 600 –602
- DOI: 10.1049/el:19810422
- Type: Article
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600
–602
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The letter presents a novel programmable unit-element SC filter for LPC synthesis. The circuit is based on the theory of wave-flow networks. It has the advantage that for a programmable 10th-order unit-element SC filter only five programmable capacitor arrays are needed. The capacitive loading of every op amp is constant, thus simplifying the op amp design. The circuit is insensitive to stray capacitances which are commonly associated with integrated MOS capacitors and transistors. It also exhibits a low sensitivity to coefficient quantisations; hence, the circuit is well suited for integration in MOS technology.
Effects of surface metallisation on SSBW and BGW propagation in quartz
- Author(s): M. Yamaguchi ; K.Y. Hashimoto ; H. Kogo
- Source: Electronics Letters, Volume 17, Issue 17, p. 602 –603
- DOI: 10.1049/el:19810423
- Type: Article
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602
–603
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The letter describes theoretical results of the effects of surface metallisation on surface-skimming-bulk-wave (SSBW) and Bleustein-Gulyaev-wave (BGW) propagation characteristics for rotated Y-cuts of quartz. For a range of rotations, the surface metallisation increases the surface mechanical displacement of the BGW relative to the SSBW. The metallisation is ineffective in trapping the SSBW energy close to the surface.
Chromatic dispersion measurement by white-light interferometry on metre-length single-mode optical fibres
- Author(s): Hen-Tai Shang
- Source: Electronics Letters, Volume 17, Issue 17, p. 603 –605
- DOI: 10.1049/el:19810424
- Type: Article
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603
–605
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Chromatic dispersion near 0.8 μm in a short (∼1 m) single-mode optical fibre is determined by a white-light interferometric technique. In particular, the wavelength-dependent group delay of the fibre is obtained directly from the spectra of the output light from a Mach-Zehnder interferometer illuminated by a GaAlAs LED. Its application in single-mode fibre studies in the 1.3 μm wavelength region is discussed.
Programmable transversal filter
- Author(s): I.A. van Gelder ; G.J. Declerck ; M.A. Copeland
- Source: Electronics Letters, Volume 17, Issue 17, p. 605 –606
- DOI: 10.1049/el:19810425
- Type: Article
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–606
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A programmable transversal filter is presented, based on the combination of a dynamic amplifier and a bucket-brigade-device analogue delay line. Experimental results are presented, indicating the suitability for a complete monolithic filter realisation.
Single-interface enhanced mobility structures by metalorganic chemical vapour deposition
- Author(s): J.J. Coleman ; P.D. Dapkus ; J.J.J. Yang
- Source: Electronics Letters, Volume 17, Issue 17, p. 606 –608
- DOI: 10.1049/el:19810426
- Type: Article
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606
–608
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Enhanced mobility effects in single-interface 2-dimensional electron gas heterostructures grown by metalorganic chemical vapour deposition (MOCVD) are reported. The mobility/temperature characteristics of single-interface structures, with and without an undoped spacer to reduce coulomb scattering at the interface, are described.
Interference of correlated radio signals with Rayleigh fading
- Author(s): A. Wojnar
- Source: Electronics Letters, Volume 17, Issue 17, p. 608 –609
- DOI: 10.1049/el:19810427
- Type: Article
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608
–609
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Radio signals from various sources may be correlated due to propagation irregularities. Here, the probability that one signal exceeds another one at least p (protection-ratio) times is determined for the case when both signals are Rayleigh distributed and correlated. The closed-form result is exact and simple. Its applications in radiocommunication are discussed.
Numerical analysis of two-dimensional piezoelectric waveguides for surface acoustic waves by finite-element method
- Author(s): M. Koshiba ; M. Okada ; M. Suzuki
- Source: Electronics Letters, Volume 17, Issue 17, p. 609 –611
- DOI: 10.1049/el:19810428
- Type: Article
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609
–611
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A combined approach of the finite-element method and the analytical solutions is described for the analysis of two-dimensional piezoelectric waveguides with semi-infinite media for surface acoustic waves. Agreement between the exact and predicted results is very good.
Fast photoconductive optoelectronic broadband switch with low control voltage
- Author(s): R.I. MacDonald ; E.H. Hara ; R.H. Hum
- Source: Electronics Letters, Volume 17, Issue 17, p. 611 –612
- DOI: 10.1049/el:19810429
- Type: Article
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611
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Optoelectronic switching with a gallium arsenide field-effect transistor used as a photoconductive detector is demonstrated. On-state to off-state isolation ratios of 65 dB from 500 kHz to 1.3 GHz, and switching times less than 10 ns, are observed. Gating voltage is of the order of 3–10 V.
Rings as elements for frequency selective surfaces
- Author(s): E.A. Parker and S.M.A. Hamdy
- Source: Electronics Letters, Volume 17, Issue 17, p. 612 –614
- DOI: 10.1049/el:19810430
- Type: Article
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Arrays of simple rings on close packed square or triangular lattices are useful frequency selective surfaces for reflector antennas. Reflection bandwidths of about 26 per cent and transmission/reflection band ratios of 3:1 are readily attainable for angles of incidence of up to 45° at least. Experimental transmission coefficients are compared with the results of modal computations.
SSB-FDM using complementary comb filters
- Author(s): Y. Hirata
- Source: Electronics Letters, Volume 17, Issue 17, p. 614 –615
- DOI: 10.1049/el:19810431
- Type: Article
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614
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The letter describes single-sideband frequency division multiplex (SSB-FDM) systems using complementary comb filters. A lot of analogue bandpass filters in conventional modulators and demodulators can be replaced by comb filters. In the case of a 12-channel FDM system, SSB modulators can be implemented by 12 product modulators and a pair of complementary comb filters.
Low-noise state-space realisation of bandpass active filter
- Author(s): E.J.P. May and H.H. Mehdi
- Source: Electronics Letters, Volume 17, Issue 17, p. 615 –617
- DOI: 10.1049/el:19810432
- Type: Article
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An active 2nd-order bandpass state-space filter realisation known as the symmetric-form filter has been studied theoretically and practically and has been found to have desirable qualities, particularly those of low noise and good linearity. The noise and linearity performance of this realisation has been compared with that of the companion-form filter (feedforward filter).5.7 The dynamic range of the symmetric form, expressed as a power ratio, is shown to be 1000 times greater than that of the companion form having the same transfer function and using the same type of operational amplifier.
12 GHz receiver with self-oscillating dual-gate MESFET mixer
- Author(s): C. Tsironis
- Source: Electronics Letters, Volume 17, Issue 17, p. 617 –618
- DOI: 10.1049/el:19810433
- Type: Article
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A hybrid integrated 12 GHz receiver, fabricated on a 1 ×2N alumina substrate, contains a two single-gate FET preamplifier, one dual-gate FET self-oscillating mixer, IF matching and bias filters of all FETs. 11–14 dB conversion gain for a bandwidth of 400 MHz and an associated noise figure of 4.5–5 dB have been obtained.
Minority-carrier injection into diffused region of small n+-p junction
- Author(s): A.A. Eltoukhy and D.J. Roulston
- Source: Electronics Letters, Volume 17, Issue 17, p. 619 –620
- DOI: 10.1049/el:19810434
- Type: Article
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A comparison is made between one- and two-dimensional analysis of injection into the diffused region of small n+-p diodes using a numerical iterative scheme. Results are presented which show clearly the limitation of the one-dimensional analysis.
High current gain in monolithic hot-electron transistors
- Author(s): J.M. Shannon and A. Gill
- Source: Electronics Letters, Volume 17, Issue 17, p. 620 –621
- DOI: 10.1049/el:19810435
- Type: Article
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Monolithic hot-beam transistors have been made in silicon with a current gain of 20 and a MAG>20 dB. Hot electrons are injected at approximately 1.7 eV, cross a ∼250 Å wide degenerate base and surmount a 0.4 eV collector barrier.
Fully ion-implanted GaAs ICs using normally-off JFETs
- Author(s): J. Kasahara ; K. Taira ; Y. Kato ; M. Dohsen ; N. Watanabe
- Source: Electronics Letters, Volume 17, Issue 17, p. 621 –623
- DOI: 10.1049/el:19810436
- Type: Article
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Fully ion-implanted normally-off-type JFET GaAs ICs were fabricated by selective ion implantation of Si directly onto a Cr-doped semi-insulating substrate for an n-active region and Zn for a p+-gate region with subsequent capless annealing in AsH3 ambient. A 15-stage ring oscillator, consisting of the DCFL logic gate with resistive load, exhibited a propagation delay time of 85 ps/gate with a power delay product of 34 fJ.
Annealing of Si3N4-capped ion-implanted InP
- Author(s): S.S. Gill ; B.J. Sealy ; P.J. Topham ; N.J. Barrett ; K.G. Stephens
- Source: Electronics Letters, Volume 17, Issue 17, p. 623 –624
- DOI: 10.1049/el:19810437
- Type: Article
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CVD-Si3N4 layers have been used to encapsulate Se+-implanted InP during annealing in the range 550°C to 730°C. Annealing at 700°C for about 3 min produced the best electrical properties for a dose of 1×1013 Se+ cm−2, i.e. an electrical activity of 80% and and sheet mobility of 1400 cm2V−1s−1.
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