Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 20, Issue 2, 19 January 1984
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Volume 20, Issue 2
19 January 1984
Amorphous/crystalline heterostructure as a novel approach to fabrication of a solar cell
- Author(s): M.M. Rahman and S. Furukawa
- Source: Electronics Letters, Volume 20, Issue 2, p. 57 –58
- DOI: 10.1049/el:19840039
- Type: Article
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–58
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The performance and characteristics of a novel structure device combining amorphous and crystalline semiconductors is reported for the first time. An amorphous SiC:H/crystal Si heterostructure solar cell gave a conversion efficiency of 5.11% with Voc = 0.53 V and Isc = 22.64 mA/cm2 without the use of any transparent electrode or AR coating. The relative spectral response of the cells has been found to be close to that of the ‘violet cell’.
Optical power limits in multi-channel wavelength-division-multiplexed systems due to stimulated Raman scattering
- Author(s): A.R. Chraplyvy
- Source: Electronics Letters, Volume 20, Issue 2, p. 58 –59
- DOI: 10.1049/el:19840040
- Type: Article
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p.
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–59
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General expressions are derived to estimate transmitter power limitations due to stimulated Raman scattering in wavelength-division-multiplexed optical communication systems. These results are applicable to systems containing an arbitrary number of channels with arbitrary (but equal) channel separation.
GCF extraction from multivariable polynomials using generalised Padé approximations
- Author(s): Y. Shamash and M. Messiter
- Source: Electronics Letters, Volume 20, Issue 2, p. 59 –61
- DOI: 10.1049/el:19840041
- Type: Article
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p.
59
–61
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A new algorithm is presented for determining the GCF from multivariable polynomials. The technique consists of applying the generalised Padé approximation method for multivariable functions. The algorithm is conceptually simple and computationally easy.
Position recovery using binary sequences
- Author(s): B. Arazi
- Source: Electronics Letters, Volume 20, Issue 2, p. 61 –62
- DOI: 10.1049/el:19840042
- Type: Article
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It is shown how to arrange a sequence of 2n−1 bits on the circumference of a rotating device, such that the location of any specified bit is instantly recovered from the values of 2n+1 bits, sensed by fixed contacts.
Error control codes for QAM signalling
- Author(s): E.L. Cusack
- Source: Electronics Letters, Volume 20, Issue 2, p. 62 –63
- DOI: 10.1049/el:19840043
- Type: Article
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A class of block codes is described which exploits the properties of quadrature amplitude modulation signal constellations whose points lie on a square grid. The simplest codes in the class have block lengths 4 and 8 and offer coding gains of 3 dB and 4.5 dB, respectively.
Threshold current characteristics of GaAs lasers under short pulse excitation
- Author(s): N.A. Olsson ; N.K. Dutta ; W.T. Tsang ; R.A. Logan
- Source: Electronics Letters, Volume 20, Issue 2, p. 63 –64
- DOI: 10.1049/el:19840044
- Type: Article
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–64
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Measurements of the temperature dependence of threshold current using both short pulse and CW excitation of GaAs heterostructure lasers with multiquantum well and conventional active layers are presented. Our results show that the carrier density at threshold is weakly temperature-dependent in both types of lasers. This is consistent with the measured carrier lifetime at threshold.
Design procedure for offset dual reflectors with low crosspolarisation
- Author(s): T.B. Vu
- Source: Electronics Letters, Volume 20, Issue 2, p. 64 –66
- DOI: 10.1049/el:19840045
- Type: Article
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64
–66
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A simple procedure for designing offset dual reflectors with low crosspolarisation is presented. It provides simple guidelines by which the subdish and the feed parameters can be specified once the main dish geometry is known. The method is most suitable for upgrading existing offset systems with poor crosspolarisation characteristics.
Interferometric monomode fibre measurements: influence of source spectrum and second-order dispersion
- Author(s): F. Mengel
- Source: Electronics Letters, Volume 20, Issue 2, p. 66 –67
- DOI: 10.1049/el:19840046
- Type: Article
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p.
66
–67
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Crosscorrelation interferometry with below-threshold semiconductor lasers for measuring the first-order dispersion β̈ near the minimum-dispersion wavelength λ0 of monomode fibres is investigated experimentally and theoretically. A Gaussian approximation for the source spectrum is invalid, but a simple formula is found for a Lorentzian spectrum. Second-order dispersion distorts the measurements even up to 50 nm from λ0.
Remote temperature sensing using polarisation-preserving fibre
- Author(s): M. Corke ; A.D. Kersey ; K. Liu ; D.A. Jackson
- Source: Electronics Letters, Volume 20, Issue 2, p. 67 –69
- DOI: 10.1049/el:19840047
- Type: Article
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p.
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–69
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A fibre-optic temperature sensor is described in which the change in modal birefringence of a short length of polarisation-preserving fibre is monitored in reflection through a 90 m length of input fibre. The system shows high sensitivity and good downlead insensitivity.
Wavelength self stabilisation of coupled-cavity semiconductor lasers
- Author(s): K.J. Ebeling and L.A. Coldren
- Source: Electronics Letters, Volume 20, Issue 2, p. 69 –70
- DOI: 10.1049/el:19840048
- Type: Article
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A simple wavelength control circuit is demonstrated that maintains single-longitudinal-mode operation of coupled-cavity semiconductor lasers over wide ranges of temperature. Photodetection properties of the lasing system itself are used for generating the discriminating signal for the feedback loop. No external optical elements like photodetectors or spectrometers are required.
Iterative determination of oxide thickness in MOS structures from one DC current/voltage pair
- Author(s): R.B. Calligaro
- Source: Electronics Letters, Volume 20, Issue 2, p. 70 –72
- DOI: 10.1049/el:19840049
- Type: Article
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p.
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–72
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A simple iterative technique which enables the silicon dioxide thickness to be determined using Fowler-Nordheim tunnelling measurements is described. It is shown that by assuming the accepted values of the Fowler-Nordheim tunnelling constants only one DC current/voltage pair is required to obtain the thickness. The thicknesses obtained in this way are shown to be in good agreement with ellipsometer and high-frequency capacitance measurements over the range 70–350 Å.
Novel thick-grating beam-squeezing device in Ta2O5 corrugated planar waveguide
- Author(s): P.St.J. Russell
- Source: Electronics Letters, Volume 20, Issue 2, p. 72 –73
- DOI: 10.1049/el:19840050
- Type: Article
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p.
72
–73
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The fabrication and performance of a novel thick-grating beam-squeezing device in a Ta2O5 corrugated planar waveguide is described. The device, in which the design relies on consideration of the group velocities of the light inside the periodic guide at Bragg incidence, features a curved (hyperbolic) boundary transition between smooth and corrugated waveguide regions. A contraction ratio of about 30 is achieved.
Homodyne network analysis by digital phase modulation and baseband sampling
- Author(s): U. Gärtner and B. Schiek
- Source: Electronics Letters, Volume 20, Issue 2, p. 73 –75
- DOI: 10.1049/el:19840051
- Type: Article
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–75
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A homodyne detection principle employing a series of digital phase modulators is presented. Data are sampled in the baseband, and information about amplitude and phase is obtained via a simple evaluation algorithm which can be readily implemented in a microprocessor system.
Data-transmission pulses for duobinary systems
- Author(s): N. Boutin
- Source: Electronics Letters, Volume 20, Issue 2, p. 75 –76
- DOI: 10.1049/el:19840052
- Type: Article
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–76
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The letter deals with the design of finite-duration signalling pulses for duobinary systems. The proposed procedure leads to pulses which have maximum energy concentration in a given bandwidth.
Molecular hydrogen behaviour for loss increase of silica fibre in cable filled with water
- Author(s): Y. Mitsunaga ; T. Kuwabara ; T. Abe ; Y. Ishida
- Source: Electronics Letters, Volume 20, Issue 2, p. 76 –78
- DOI: 10.1049/el:19840053
- Type: Article
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–78
(3)
Evaluation of molecular hydrogen diffusion into silica fibre, which causes a loss increase at 1.24 μm wavelength, and the accumulation mechanism for hydrogen in cable are reported. It has been found that loss increase around 1.24 μm wavelength due to hydrogen greatly depends on the ambient hydrogen pressure. The hydrogen pressure in LAP sheath cable easily increases due to metal corrosion and the sealing effect of the sheath.
Analysis of splices in shifted zero dispersion monomode fibre
- Author(s): D.J. McCartney ; D.B. Payne ; J.V. Wright
- Source: Electronics Letters, Volume 20, Issue 2, p. 78 –80
- DOI: 10.1049/el:19840054
- Type: Article
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p.
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–80
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We present loss histograms for splices in shifted zero dispersion monomode optical fibre, at λ = 1.55 μm using fusion and glueing techniques. Mean losses of 0.29 dB and 0.08 dB, respectively, have been obtained. The increased loss in the fusion splices is shown to be attributable to effective separation and effective offset, due to core deformation at the splice point.
1.5 μm phase-shifted DFB lasers for single-mode operation
- Author(s): K. Sekartedjo ; N. Eda ; K. Furuya ; Y. Suematsu ; F. Koyama ; T. Tanbun-Ek
- Source: Electronics Letters, Volume 20, Issue 2, p. 80 –81
- DOI: 10.1049/el:19840055
- Type: Article
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p.
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–81
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Fabrication and single-mode laser oscillation were demonstrated for modified DFB lasers where the phase of the corrugations was shifted at the centre by a quarter guided-wavelength and which, in principle, provided a resonance at the Bragg wavelength and stable single-mode oscillation. Phase-shifted corrugations were fabricated using electron-beam lithography.
Correction for measured resonant frequency of unloaded cavity
- Author(s): D. Kajfez
- Source: Electronics Letters, Volume 20, Issue 2, p. 81 –82
- DOI: 10.1049/el:19840056
- Type: Article
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p.
81
–82
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Ginzton's method of Q-factor measurement provides the necessary data for taking into account the detuning effect of the coupling circuit by means of which the measurement is performed.
Proposal of a distributed feedback laser with nonuniform stripe width for complete single-mode oscillation
- Author(s): K. Tada ; Y. Nakano ; A. Ushirokawa
- Source: Electronics Letters, Volume 20, Issue 2, p. 82 –84
- DOI: 10.1049/el:19840057
- Type: Article
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p.
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–84
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For a complete single axial mode oscillation of the DFB laser, a new structure is proposed, in which the stripe width is varied symmetrically along the laser axis. An optimum design example is presented.
High-frequency GaAs transversal filter
- Author(s): A.J. McKnight ; J. Mun ; I.A.W. Vance
- Source: Electronics Letters, Volume 20, Issue 2, p. 84 –85
- DOI: 10.1049/el:19840058
- Type: Article
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–85
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A transversal filter integrated circuit, fabricated using 1 μm GaAs MESFET technology, is described. The filter uses 280 MESFETs, has a clocked delay line and on-chip tap weighting to give three different filter responses. Operation has been demonstrated up to a clock frequency of 400 MHz, which is believed to be the fastest reported operation of a clocked transversal filter.
Evidence of the importance of Auger recombination for InGaAsP lasers
- Author(s): A. Haug
- Source: Electronics Letters, Volume 20, Issue 2, p. 85 –86
- DOI: 10.1049/el:19840059
- Type: Article
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p.
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–86
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The temperature dependence of Auger recombination in InGaAsP can be described by two regions, one with a slow increase of the Auger coefficient and one with a strong increase. This behaviour is similar to that of the threshold current of an InGaAsP laser. In particular, the slope of the temperature curve of the Auger coefficient changes at T = 255 K, which is exactly the break point temperature of the threshold current. Auger recombination therefore seems to be the most important cause for the temperature dependence of the threshold current in InGaAsP lasers.
Temperature effects on high-gain photoconductive detectors
- Author(s): J.P. Vilcot ; J.L. Vaterkowski ; D. Decoster ; M. Constant
- Source: Electronics Letters, Volume 20, Issue 2, p. 86 –88
- DOI: 10.1049/el:19840060
- Type: Article
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p.
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–88
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In the letter we report gain measurements on N-type GaAs planar photoresistors which have been performed against temperature, for various light powers. A strong dependence of gain on temperature has been shown and interpreted in terms of trapping effects.
Direct measurement of the frequency-modulation characteristics of a coupled-cavity laser
- Author(s): A.S. Sudbø
- Source: Electronics Letters, Volume 20, Issue 2, p. 88 –89
- DOI: 10.1049/el:19840061
- Type: Article
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p.
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–89
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The modulation characteristics of a coupled-cavity AlGaAs injection laser have been investigated in the frequency range 0.2 to 1.0 GHz. The laser operates in a single longitudinal mode for almost all injection currents and modulation indices above laser threshold. The phase and amplitude of the current-to-frequency-modulation transfer function of the laser have been measured.
New prime implicant algorithm, based on monotonicity properties
- Author(s): B. Taconet
- Source: Electronics Letters, Volume 20, Issue 2, p. 89 –90
- DOI: 10.1049/el:19840062
- Type: Article
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p.
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–90
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The key of this new algorithm is the building of prime generators, only made up of unate letters. It is revealed to be very efficient when the function is nearly monotonic.
Tropospheric amplitude scintillations at C-band along satellite up-link
- Author(s): C.N. Wang ; F.S. Chen ; C.H. Liu ; D.J. Fang
- Source: Electronics Letters, Volume 20, Issue 2, p. 90 –91
- DOI: 10.1049/el:19840063
- Type: Article
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–91
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Long-term data for unusually strong tropospheric amplitude scintillations at 6.2 GHz on a satellite up-link are presented. A diurnal maximum in the afternoon and seasonal peaks in spring and autumn are found. The high-level scintillation activities are explained in terms of local tropospheric conditions and propagation theory. A typical power spectrum and distribution are discussed.
Twisted-terraced-substrate GaAs/AlGaAs lasers
- Author(s): K.-L. Chen ; T. Sugino ; S. Wang
- Source: Electronics Letters, Volume 20, Issue 2, p. 91 –93
- DOI: 10.1049/el:19840064
- Type: Article
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–93
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We present a new structure of AlGaAs/GaAs DH lasers consisting of two oppositely facing terraced-substrate cavities in series. Polarisation change at the junction results in internal reflection and produces a mode-selection effect. A stable single longitudinal mode is observed over a wide current range from 100 to 150 mA. The dominant lasing mode is locked over a 7° temperature variation. The lowest observed threshold current is 50 mA.
Optical losses in polycrystalline thallium halide fibres at CO- and CO2-laser wavelengths
- Author(s): V.G. Artjushenko ; L.N. Butvina ; V.V. Vojtsehovskii ; E.M. Dianov ; A.M. Prokhorov
- Source: Electronics Letters, Volume 20, Issue 2, p. 93 –94
- DOI: 10.1049/el:19840065
- Type: Article
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93
–94
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The scattering and absorption loss distribution along polycrystalline fibres from KRS-5 was measured by the laser calorimetry method. The minimal optical losses at 10.6 μm were 0.35 dB/m and were mainly caused by absorption. At 5–6 μm, absorption and scattering losses were equal and their sum was 1.6 dB/m.
Multi-look-up-table module for RNS systems implementation
- Author(s): M. Bayoumi ; G.A. Jullien ; W.C. Miller
- Source: Electronics Letters, Volume 20, Issue 2, p. 94 –95
- DOI: 10.1049/el:19840066
- Type: Article
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–95
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A multi-look-up-table module is proposed for implementing residue number system (RNS) algorithms getting the benefit of VLSI technology. The performance measures of this implementation are area and time. An example of using this module for building a scaling array is presented.
Fibre-optic tapped delay line filter employing coherent optical processing
- Author(s): D.E.N. Davies and G.W. James
- Source: Electronics Letters, Volume 20, Issue 2, p. 95 –97
- DOI: 10.1049/el:19840067
- Type: Article
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–97
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The letter describes a novel form of optical fibre tapped delay line signal processor in which the signal taps are achieved without introducing couplers into the fibre, by the use of external piezoelectric phase modulators located along the single-mode fibre. This enables the system to operate as a coherent processor and the concept has a number of attractive features including reduced optical losses, increased dynamic range and capability for electronic control of fibre taps. A simple laboratory demonstration of a two-tap filter is described to confirm the operation of the system.
Modelling of single- and dual-gate MESFET mixers
- Author(s): R. Meierer and C. Tsironis
- Source: Electronics Letters, Volume 20, Issue 2, p. 97 –98
- DOI: 10.1049/el:19840068
- Type: Article
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97
–98
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Computer modelling allowing the determination of matching circuitry and optimum bias conditions for maximum conversion gain and IF bandwidth of FET mixers is described. Theoretical results for single-gate and dual-gate FET mixers are presented. Good agreement with measurements on a 12 GHz DBS reception dual-gate FET mixer (8 dB conversion gain with 800 MHz bandwidth) is demonstrated.
GaAs MESFETs with a buried p-layer for large-scale integration
- Author(s): Y. Umemoto ; S. Takahashi ; N. Matsunaga ; M. Nakamura
- Source: Electronics Letters, Volume 20, Issue 2, p. 98 –100
- DOI: 10.1049/el:19840069
- Type: Article
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A new GaAs MESFET structure with a buried p-layer that produces a uniform threshold voltage is proposed and realised using a Be ion implantation technique. These new FETs improve the uniformity of the threshold voltage to 5% from the previous 10% in HB Cr-doped GaAs crystal.
Fabrication of fluoride glass fibres by the improved crucible technique
- Author(s): Y. Mimura ; H. Tokiwa ; O. Shinbori
- Source: Electronics Letters, Volume 20, Issue 2, p. 100 –101
- DOI: 10.1049/el:19840070
- Type: Article
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–101
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A novel crucible technique is described for the manufacture of crystalline-free fluoride glass fibres. Using the improved crucible technique, 200 m-long ZrF4-BaF2-LaF3-AlF3-NaF glass fibres have been fabricated.
Passive switched capacitor filters: general biquad topology
- Author(s): S. Manetti
- Source: Electronics Letters, Volume 20, Issue 2, p. 101 –102
- DOI: 10.1049/el:19840071
- Type: Article
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101
–102
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A new technique is described for the realisation of the general biquad topology by means of passive switched-capacitor networks, i.e. utilising only capacitors and MOS switches.
Generalised coupled-wave theory of scalar volume diffraction
- Author(s): J.W. Lewis and L. Solymar
- Source: Electronics Letters, Volume 20, Issue 2, p. 103 –104
- DOI: 10.1049/el:19840072
- Type: Article
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p.
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–104
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An extended coupled-wave theory of volume phase holography is developed using Fourier techniques. Fresnel, as well as Bragg, diffraction effects are incorporated for general high-efficiency transmission gratings illuminated by general beams. The method is illustrated by a numerical example.
Linear amplification of signals by use of two oscillators: a proposal
- Author(s): M. Nakajima and J. Ikenoue
- Source: Electronics Letters, Volume 20, Issue 2, p. 104 –105
- DOI: 10.1049/el:19840073
- Type: Article
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It is described how linear amplification of signals is achieved by a coupled system of oscillators with a hybrid element, and an experimental verification is given. This scheme may be applied to amplification of signals ranging from microwave to optical frequencies.
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