Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 23, Issue 15, 16 July 1987
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Volume 23, Issue 15
16 July 1987
Improving the performance of nonplanar systolic architectures through increased fan-out
- Author(s): A. El-Amawy
- Source: Electronics Letters, Volume 23, Issue 15, p. 765 –766
- DOI: 10.1049/el:19870542
- Type: Article
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We show that the performance of nonplanar systolic architectures implementing nonfeedback recurrences can be improved through increased processing element fan-out. As an illustrative example we demonstrate the speed improvement for matrix-matrix multiplication on a modified cylindrical array.
Variable-data-rate systems applicable to fading satellite channels
- Author(s): A.P. Gallois and A.M. Böck
- Source: Electronics Letters, Volume 23, Issue 15, p. 766 –767
- DOI: 10.1049/el:19870543
- Type: Article
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To maintain communication over fading satellite channels, either the transmission rate and system bandwidth have to be reduced or the equivalent isotropic radiated power (EIRP) of the satellite has to be increased. In the letter methods are proposed for changing the transmission rate without changing the filters, and the performance of these methods is evaluated.
Wideband microstrip balanced mixer
- Author(s): R.S. Tahim ; K. Chang ; K.A. Hummer
- Source: Electronics Letters, Volume 23, Issue 15, p. 767 –768
- DOI: 10.1049/el:19870544
- Type: Article
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–768
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A novel microstrip balanced mixer circuit has been developed with over 40% bandwidth. The circuit uses two coupling rings for RF and LO inputs. A conversion loss of less than 8dB has been achieved for the RF frequency swept from 13 to 23 GHz with an LO signal at 25 GHz.
High-efficiency Nd-doped fibre lasers using direct-coated dielectric mirrors
- Author(s): M. Shimizu ; H. Suda ; M. Horiguchi
- Source: Electronics Letters, Volume 23, Issue 15, p. 768 –769
- DOI: 10.1049/el:19870545
- Type: Article
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The letter presents an Nd-doped silica single-mode fibre laser with dielectric mirrors coated directly on to the fibre endfaces. The LD-pumped fibre laser had a CW output power of more than 4mW, a threshold power of 1.51 mW and a slope efficiency of 55%. The theoretically predicted values and experimental values of the laser characteristics are very similar owing to a negligibly small excess cavity loss.
Reduced-complexity digital filtering structures using primitive operations
- Author(s): D.R. Bull and D.H. Horrocks
- Source: Electronics Letters, Volume 23, Issue 15, p. 769 –771
- DOI: 10.1049/el:19870546
- Type: Article
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The letter presents a class of algorithms which generate filtering structures with reduced numbers of elementary operations. The directed acyclic graphs which result completely describe the device structure, and may be mapped directly into hardware or software realisations.
Novel 93 GHz injection-locked impatt oscillator
- Author(s): D.H. Evans and R.N. Bates
- Source: Electronics Letters, Volume 23, Issue 15, p. 771 –772
- DOI: 10.1049/el:19870547
- Type: Article
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–772
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An injection-locking technique whereby a varactor-tuned Gunn oscillator is connected directly to a high-power impatt oscillator is described. The technique does not require a circulator and results in a compact, high-power, electronically tunable source.
High-power etched-facet lasers
- Author(s): P. Tihanyi ; D.K. Wagner ; H.J. Vollmer ; A.J. Roza ; C.M. Harding ; R.J. Davis ; E.D. Wolf
- Source: Electronics Letters, Volume 23, Issue 15, p. 772 –773
- DOI: 10.1049/el:19870548
- Type: Article
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We demonstrate, for the first time, laser diodes with anetched facet fabricated by chemically assisted ion beametching, producing 1–7 W pulsed and 470mW CW output power from one facet. The devices were coated and bonded junction-side-up and tested at room temperature. The single 40 μm stripe, 300 μm-long devices exhibit 94 mA threshold current and differential quantum efficiencies of 80% pulsed (78% CW).
Analysis of an interferometric optical fibre detection technique applied to silicon vibrating sensors
- Author(s): M.V. Andres ; M.J. Tudor ; K.W.H. Foulds
- Source: Electronics Letters, Volume 23, Issue 15, p. 774 –775
- DOI: 10.1049/el:19870549
- Type: Article
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–775
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A simple and accurate analysis of a single-mode optical fibre interferometric displacement detection technique is resented. This analysis is in good agreement with experimental measurements, and shows that angular alignment between the fibre and the sensor is the most critical parameter.
Precise realisation of an insensitive floating negative admittance convertor
- Author(s): R. Nandi
- Source: Electronics Letters, Volume 23, Issue 15, p. 775 –777
- DOI: 10.1049/el:19870550
- Type: Article
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775
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A new floating negative admittance convenor (FNAC) network using the second-generation current conveyor (CCII) active devices has been proposed. The novelties of the scheme are no component matching requirements, use of only the nominal termination admittance under ideal device conditions, and practically active-insensitive network characteristics. Even with nonideal but matched devices, no extra matching component is required for a true FNAC realisation. However, with nonideal and nonidentical devices, insertion of a single compensating admittance yields a precise bilateral FNAC.
Minimal transistor-only micropower integrated VHF active filter
- Author(s): Y.P. Tsividis
- Source: Electronics Letters, Volume 23, Issue 15, p. 777 –778
- DOI: 10.1049/el:19870551
- Type: Article
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A minimal integrated filter containing four MOS transistors as the only circuit elements is presented. Voltage tuning is used to set the cutoff frequency and band-edge peaking. A filter test chip occupies an active area of 0006mm2, has acutoff frequency of 40 MHz and dissipates 580W.
Nonlinear interpolation of TV image sequences
- Author(s): R. Glavina ; S. Cucchi ; G.L. Sicuranza
- Source: Electronics Letters, Volume 23, Issue 15, p. 778 –780
- DOI: 10.1049/el:19870552
- Type: Article
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A 3-D nonlinear filter for the interpolation of skipped frames in the transmission of TV image sequences at low bit rates is presented. The results obtained show that the nonlinear approach is convenient in the presence of moderate movements of the objects in the observed scene
Excitations providing maximum directivity for difference arrays of discrete elements
- Author(s): D.A. McNamara
- Source: Electronics Letters, Volume 23, Issue 15, p. 780 –781
- DOI: 10.1049/el:19870553
- Type: Article
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p.
780
–781
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The discrete distributions which provide maximum difference directivity, analogous to that derived previously for continuous line sources, are considered, and some general results given.
Pigtailed high-finesse tunable fibre Fabry-Perot interferometers with large, medium and small free spectral ranges
- Author(s): J. Stone and L.W. Stulz
- Source: Electronics Letters, Volume 23, Issue 15, p. 781 –783
- DOI: 10.1049/el:19870554
- Type: Article
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p.
781
–783
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We have made prototypes of three kinds of fibre Fabry-Perot (FFP) tunable filters, each of which can cover a separate free spectral range interval as determined by its resonator length. Free spectral ranges from hundreds of angstroms to tens of megahertz can be realised from the appropriate type. We have built FFPs with free spectral ranges of >1000 A, 25 GHz, 5 GHz and 2.5 GHz. Finesse up to 200 has been demonstrated. The devices are piezoelectrically tuned and are coupled to fibres in-line using standard rotary splices or ST connectors.
Optical sampling of GHz charge density modulation in silicon bipolar junction transistors
- Author(s): A. Black ; C. Courville ; G. Schultheis ; H. Heinrich
- Source: Electronics Letters, Volume 23, Issue 15, p. 783 –784
- DOI: 10.1049/el:19870555
- Type: Article
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We report the use of optical sampling employing a gain-switched 1.3μm semiconductor laser to observe charge density modulation in a 1.5μm x 5μm emitter silicon BJT. The overall system bandwidth is 8 GHz. The device under test is switched at frequencies from 100 MHz to 2.5 GHz.
Accuracy of method of moments and weighted index method
- Author(s): D.A. Roberts and M.S. Stern
- Source: Electronics Letters, Volume 23, Issue 15, p. 784 –785
- DOI: 10.1049/el:19870556
- Type: Article
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p.
784
–785
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The weighted index (WI) method has been used to compute the propagation constants of buried and channel waveguide structures. The results are compared with the commonly used effective index method, the method of moments and an accurate finite difference technique. The WI method is shown to be the most accurate of the approximate methods and is especially useful close to cutoff.
Transformer-tuned front-ends for heterodyne optical receivers
- Author(s): J.X. Kan ; I. Garrett ; G. Jacobsen
- Source: Electronics Letters, Volume 23, Issue 15, p. 785 –786
- DOI: 10.1049/el:19870557
- Type: Article
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p.
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–786
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We present measured noise spectra for heterodyne optical receivers with front-end tuning based on a T-equivalent circuit of transformer coupling. A noise spectral density below 6pA/√(Hz) over a 1-3 GHz bandwidth is demon-strated, even with parasitic capacitances totalling 2 pF.
Improved design of tuned optical receivers
- Author(s): G. Jacobsen ; J.X. Kan ; I. Garrett
- Source: Electronics Letters, Volume 23, Issue 15, p. 787 –788
- DOI: 10.1049/el:19870558
- Type: Article
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p.
787
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We present new design principles for improved heterodyne tuned optical receivers where several tuning inductances reduce the influence of thermal receiver noise over a broad frequency range. A theoretical example for a 600 MHz tuning bandwidth shows a reduction of thermal receiver noise (and thus in required local oscillator power) of up to 13dB. The example is tested experimentally for the so-called mixed tuning configuration. We obtain good agreement with the theoretical predictions. The experimental RMS noise current is <5pA/√(Hz) over a 580 MHz bandwidth with the lowest value of 3-5 pA/√(Hz) at 950MHz.
5 GHz-spaced, eight-channel, guided-wave tunable multi/demultiplexer for optical FDM transmission systems
- Author(s): H. Toba ; K. Oda ; N. Takato ; K. Nosu
- Source: Electronics Letters, Volume 23, Issue 15, p. 788 –789
- DOI: 10.1049/el:19870559
- Type: Article
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p.
788
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A 5GHz-spaced, eight-channel, guided-wave tunable multi/demultiplexer for optical frequency-division-multiplexing (FDM) transmission systems is demonstrated. It is constructed with high-silica channel waveguides and thin-film heaters loaded on the waveguides for frequency tuning
Subreflector shaping to improve multiple-beam performance of a Cassegrain antenna
- Author(s): S.G. Hay
- Source: Electronics Letters, Volume 23, Issue 15, p. 789 –791
- DOI: 10.1049/el:19870560
- Type: Article
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p.
789
–791
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A method of designing multiple-beam antennas based on shaping the subreflector of an offset Cassegrain antenna is described. It is applied to a compact system having a diameter of 300λ that is required to produce beams up to 4-6°either side of boresight. The performance is shown to be only slightly less than that obtainable by also shaping the main reflector, indicating that efficient multiple-satellite-access antennas can be designed without specially shaped main reflectors.
Second-harmonic generation in single crystals of 2-(N,N-dimethylamino)-5-nitroacetanilide (DAN) at 1.3 μm
- Author(s): P.V. Kolinsky ; R.J. Chad ; R.J. Jones ; S.R. Hall ; P.A. Norman ; D. Bloor ; J.S. Obhi
- Source: Electronics Letters, Volume 23, Issue 15, p. 791 –792
- DOI: 10.1049/el:19870561
- Type: Article
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p.
791
–792
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Measurements are reported on efficiency phase-matched second-harmonic generation (SHG) in a single crystal of the organic material 2-(N, N-dimethylamino)-5-nitroacetanilide (DAN) at the technologically important communications wavelength of 1-3 /mi. Using 0-5 mJ pulses, a conversion efficiency of 18% has been achieved for a sample 2 mm thick.
Low-loss optical stripe waveguides in LiNbO3 formed by He+ implantation
- Author(s): G.T. Reed and B.L. Weiss
- Source: Electronics Letters, Volume 23, Issue 15, p. 792 –794
- DOI: 10.1049/el:19870562
- Type: Article
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792
–794
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We report the fabrication of low-loss stripe optical wave-guides in LiNbO 3by He+ implantation. At a wavelength of 633 nm the waveguides were found to have a propagation loss as low as l-OdBcm−1, dependent on the make-up of the vertical waveguide walls. These waveguides were also found to exhibit no photorefractive effects.
Fast computation of A * B modulo N
- Author(s): P.W. Baker
- Source: Electronics Letters, Volume 23, Issue 15, p. 794 –795
- DOI: 10.1049/el:19870563
- Type: Article
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The computation of A*BmoduloN is an important arith-metic operation in security cryptosystems. Since the word length n involved is large, speed-up techniques are important. The letter demonstrates that, for n-bit arguments, at most 2n carry-save additions are required, followed by at most two carry-propagate additions for final assimilation, using components no more than n + 3 bits wide.
Electromagnetic scattering by inhomogeneous dielectric cylinders
- Author(s): C.G. Migliora and M.B.F. Chaves
- Source: Electronics Letters, Volume 23, Issue 15, p. 795 –796
- DOI: 10.1049/el:19870564
- Type: Article
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The scattering of electromagnetic waves by inhomogeneous dielectric cylinders is formulated by the unimoment method, and the interior finite-element problem is solved in a mesh geometry that greatly increases computational efficiency. Results are presented and compared to previously reported curves.
Reduction of bend losses in Ti:LiNbO3 waveguides through MgO double diffusion
- Author(s): B. Scḧppert
- Source: Electronics Letters, Volume 23, Issue 15, p. 797 –798
- DOI: 10.1049/el:19870565
- Type: Article
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A significant reduction in bend losses in Y-cut Ti: LiNbO3waveguides by means of a double-diffusion technique is reported. Compared to pure Ti: LiNbO3 waveguide bends, MgO: Ti: LiNbO3 waveguide bends offer a reduction in the necessary bend radius by a factor as large as eight, if a total bend excess loss of 1 dB is allowable.
Garbage collection coprocessor system
- Author(s): K.F. Wong
- Source: Electronics Letters, Volume 23, Issue 15, p. 798 –800
- DOI: 10.1049/el:19870566
- Type: Article
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798
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The intelligent cell memory system is a coprocessor system to achieve on-the-fly garbage collection. Analyses on its experimental results reveal its advantages over conventional garbage collection approaches
Transconductance dependence on gate length for GaAs gate SISFETs
- Author(s): M. Chen ; W.J. Schaff ; P.J. Tasker ; L.F. Eastman
- Source: Electronics Letters, Volume 23, Issue 15, p. 800 –801
- DOI: 10.1049/el:19870567
- Type: Article
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We have processed GaAs gate SISFETs with gate lengths varying from 0.75 μm to 20 μm and shown that the trans-conductance varies inversely with gate length at a rate similar to that observed in MODFETs. Short-gate-length effects are observed for gate lengths less than 4/xm. The intrinsic transconductances both at room temperature and at 77 K of 350mS/μm and 440mS/mm, respectively, for 0.75/μm-gate-length devices are as far as we know the highest values ever reported and are essentially flat for gate voltages in the range of 0.2 to 0.9 V.
16 Gbit/s direct modulation of an InGaAsP laser
- Author(s): A.H. Gnauck and J.E. Bowers
- Source: Electronics Letters, Volume 23, Issue 15, p. 801 –803
- DOI: 10.1049/el:19870568
- Type: Article
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We describe the first 16Gbit/s electronic multiplexer and use it to measure the characteristics of a high-speed directly modulated InGaAsP 1-3/wn-wavelength laser and a high-speed InGaAs/InP PIN photodetector. The laser rise and fall times are typically 35 ps and 40 ps, respectively. The largest eye opening occurs at an output power of 10mW with an optical extinction ratio of 2-3:1.
Polarisation switching in a single-frequency external-cavity semiconductor laser
- Author(s): T. Fujita
- Source: Electronics Letters, Volume 23, Issue 15, p. 803 –804
- DOI: 10.1049/el:19870569
- Type: Article
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p.
803
–804
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Polarisation switching between the TE and TM modes is demonstrated in an external-cavity semiconductor laser. A novel polarisation-selective external cavity with an intra-cavity electro-optic intensity modulator is used to switch the polarisation between two stable single-frequency oscillations
Ferrite tunable metal insert filter
- Author(s): J. Uher
- Source: Electronics Letters, Volume 23, Issue 15, p. 804 –806
- DOI: 10.1049/el:19870570
- Type: Article
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p.
804
–806
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A novel type of magnetically tunable waveguide filter is presented which is highly appropriate for E-plane integrated circuit applications. The design theory, which is based on the field expansion into normalised eigenmodes and the modal S-matrix description of the discontinuities, includes both higher-order mode interaction and finite thickness of the E-plane metal, as well as of the lateral ferrite inserts. Optimised design data for two-and three-resonator-type filters are given for midband frequencies of about 15.3-15.4 GHz and 14.1-14.8 GHz. The theory is verified by measurement
Improved scheduling of traffic for a high-speed slotted ring
- Author(s): J.O. Limb and S. Kandiyoor
- Source: Electronics Letters, Volume 23, Issue 15, p. 806 –807
- DOI: 10.1049/el:19870571
- Type: Article
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We describe a new scheduling protocol, designed to work efficiently at very high speeds over large distances and adaptable to support arbitrary mixtures of different types of traffic. While the concept may be applied to different types of LANs and MANs, we explore it here in the context of a slotted ring with packet reuse.
Automatic formant estimation algorithm based on pointwise analysis
- Author(s): X.D. Huang ; G. Duncan ; M.A. Jack
- Source: Electronics Letters, Volume 23, Issue 15, p. 807 –809
- DOI: 10.1049/el:19870572
- Type: Article
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807
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Accurate formant analysis of speech is crucial to speech recognition and coding systems. Here, it is shown that the analysis frame position can perturb the formant estimates. A novel temporal synchronous approach employing adaptive filter techniques is presented. The optimum frame position is obtained from probability measures derived from filter parameters, thereby attenuating formant perturbation.
Public key cryptosystem using a reciprocal number with same intractability as factoring a large number
- Author(s): K. Kurosawa ; T. Ito ; M. Takeuchi
- Source: Electronics Letters, Volume 23, Issue 15, p. 809 –810
- DOI: 10.1049/el:19870573
- Type: Article
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The letter proposes a public key cryptosystem using a reciprocal number. Breaking the proposed cryptosystem is proven to be as difficult as factoring a large number.
kth least significant bit of a plaintext in reciprocal number cryptosystem
- Author(s): K. Kurosawa
- Source: Electronics Letters, Volume 23, Issue 15, p. 810 –811
- DOI: 10.1049/el:19870574
- Type: Article
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810
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Breaking the public key cryptosystem proposed by the author has been proven to be as hard as factoring a large number. The letter shows that guessing the kth least significant bit of a plaintext is also as difficult as factorisation (k ≤ log n, where n is the bit length of a plaintext).
Base station multicoupler design for UK cellular radio systems
- Author(s): S. Kazeminejad ; D.P. Howson ; G. Hamer
- Source: Electronics Letters, Volume 23, Issue 15, page: 812 –812
- DOI: 10.1049/el:19870575
- Type: Article
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Intermodulation interference in a TACS cellular radio scheme can be reduced if the base station multicoupler operates at 900 MHz, with transmitter frequency spacings of 200 kHz. Such a combiner, using a high-Q cavity and a circu-lator in each branch, is described. This gives a total transmitter-transmitter isolation of 75 dB for an insertion loss of 2.5 dB.
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