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Electronics Letters

Issue 22 • Date 28 Oct. 1993

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Displaying Results 1 - 25 of 65
  • Backfire mode zigzag antenna

    Publication Year: 1993 , Page(s): 1905 - 1906
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (191 KB)  

    A backfire mode zigzag antenna is analysed using the method of moments. The effects of the filament length of the zigzag on the -10 dB beam width is calculated. The zigzag antenna is applied to a symmetrical paraboloidal reflector antenna as a primary feed. The reflector antenna shows a relatively constant gain in the communication satellite frequency band 12.25-2.75 GHz. View full abstract»

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  • Dual slot-coupled microstrip antenna for dual frequency operation

    Publication Year: 1993 , Page(s): 1906 - 1907
    Cited by:  Papers (5)  |  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (192 KB)  

    A new dual slot-coupled circular antenna for dual frequency or dual polarisation operation is proposed. By optimising the placement of the two slots, high isolation between two ports is achieved. Experimentally, an isolation of more than 35 dB is obtained at L-band. View full abstract»

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  • Improved analysis method for broadband rectangular microstrip antenna geometry using E-plane gap coupling

    Publication Year: 1993 , Page(s): 1907 - 1909
    Cited by:  Papers (1)  |  Patents (11)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (262 KB)  

    An analysis method for the broadband rectangular microstrip antenna geometry using E-plane gap coupling is considered. The return loss of the designed broadband antenna is computed theoretically and compared with experimental results for illustrating the usefulness of this method. View full abstract»

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  • Cochannel interference probability for micro- and picocellular systems at 60 GHz

    Publication Year: 1993 , Page(s): 1909 - 1910
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (192 KB)  

    Cochannel interference probability is evaluated for micro- and picocellular systems considering the oxygen absorption at 60 GHz. For a picocellular system both desired and interfering signals are Rician distributed, whereas for a microcellular system the desired and interfering signals are Rician and Rayleigh distributed, respectively. View full abstract»

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  • DC-free error-correcting convolutional codes

    Publication Year: 1993 , Page(s): 1910 - 1911
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (214 KB)  

    A new class of DC-free error-correcting convolutional codes is presented. The codes are constructed based on error-correcting convolutional codes and can be encoded and decoded using convolutional encoders and decoders with slight modifications. The DC-free error correcting codes are especially well suited for applications in high-speed noisy channels. View full abstract»

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  • Fuzzy smoothing of HMM parameters using the Parzen window

    Publication Year: 1993 , Page(s): 1911 - 1913
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (322 KB)  

    Presents a parameter-smoothing technique for discrete hidden Markov models in speech recognition using fuzzy vector quantisation and the Parzen window. The technique is compared with existing smoothing techniques by experiments with speaker-independent isolated word recognition. The results suggest that this technique is more effective than the others in terms of improved recognition. View full abstract»

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  • General computation method of outage time for digital radio links

    Publication Year: 1993 , Page(s): 1913 - 1914
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (219 KB)  

    A method to compute outage time during clear air conditions on any radio path for various types of digital modulation is proposed. The performance of digital systems depends on combined effects of in-band amplitude dispersion (IBAD) in the channel bandwidth, and of carrier to noise ratio (CNR). Outage time is then computed for a given period using the statistical dependence of IBAD and CNR in the propagation mechanisms occurring on the path and using the formal relation of IBAD with CNR characterising the digital equipment in service. View full abstract»

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  • Hangup in asynchronous timing recovery loops

    Publication Year: 1993 , Page(s): 1914 - 1915
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (213 KB)  

    The effects of hangup in digital asynchronous timing recovery loops are investigated. It is demonstrated that delay quantisation in the interpolation filter exacerbates the problem of hangup. It is also noted that the effects of hangup are worse for the non-data aided (NDA) loops than they are for the decision-directed (DD) loops. This may preclude the use of the former in TDMA applications. View full abstract»

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  • Hierarchical block-motion estimation using linear model-based postprocessing

    Publication Year: 1993 , Page(s): 1915 - 1917
    Cited by:  Patents (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    A two-hierarchy block-motion estimation method is proposed which uses a postprocessor based on a linear model of the block-motion vector field. Postprocessing in each hierarchy uses the linear model to correct false motion vectors estimated by blockmatching. By depending on a weighting parameter and window size for the correction, the global or local motion is effectively generated at each hierarchy. View full abstract»

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  • Improvement of delay spread immunity by using symbol timing synchronisation based on maximum likelihood estimation for 16 QAM/TDMA diversity receivers

    Publication Year: 1993 , Page(s): 1917 - 1918
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (189 KB)  

    Symbol timing synchronisation (STSYNC) based on maximum likelihood estimation and a receiver configuration in which each branch independently estimates optimum STSYNC timing are proposed to improve delay spread immunity for I6 QAM/TDMA diversity receivers. Computer simulation confirms that the proposed STSYNC and receiver configuration can improve delay spread immunity by approximately 30%. View full abstract»

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  • Interpolation using the discrete sine transform with increased accuracy

    Publication Year: 1993 , Page(s): 1918 - 1920
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (274 KB)  

    The accuracy of interpolation using the discrete sine transform can be greatly improved by mapping the sequence to one which satisfies zero boundary point conditions. The accuracy may be increased if the mapped sequence also satisfies the boundary requirements for second-order derivatives. View full abstract»

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  • Minislotted packet reservation multiple access

    Publication Year: 1993 , Page(s): 1920 - 1921
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (209 KB)  

    A minislotted packet reservation multiple access (PRMA) protocol is proposed in response to the disadvantage of PRMA wherein an entire slot is wasted in the event of a collision. The proposed protocol is shown to yield improvements over PRMA at the expense of introducing small amounts of additional clipping in some talkspurts. View full abstract»

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  • New total carrier phase estimator in fully phase modulated signals

    Publication Year: 1993 , Page(s): 1921 - 1922
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (203 KB)  

    The open-loop phase estimator (OLPE) has been used to recover the carrier phase for burst mode communications. However, OLPE is not optimal in the presence of frequency offset. The authors propose a new carrier phase estimator in a feedforward form to restore the total carrier phase, including the carrier phase offset and/or the carrier frequency offset. The proposed estimator has significantly less complex hardware compared with the maximum likelihood estimator (MLE) in practical implementations. View full abstract»

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  • Programmable general purpose data path suitable for video signal processors

    Publication Year: 1993 , Page(s): 1922 - 1924
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (314 KB)  

    A new general purpose data path is presented which is suitable for use in a programmable video signal processor. The device is based on a combination of multi-pipeline and SIMD processors. The authors begin with an explanation of the inadequacies of current SIMD processors. The proposed data path is then presented. This is followed by a brief algorithmic comparison between the proposed data path, and a traditional SIMD processor, for a selected image coding task. View full abstract»

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  • Robust hybrid pitch detector

    Publication Year: 1993 , Page(s): 1924 - 1926
    Cited by:  Papers (8)  |  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (290 KB)  

    A hybrid pitch detector characterised by parallel analysis of the speech signal in temporal, spectral and cepstral domains is proposed. The voiced/unvoiced decision and pitch period evaluation is realised by a logical analysis of the results from three domains. The experimental analysis shows the robustness of the detector for noisy and telephone speech. View full abstract»

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  • Suppression of impulsive disturbances from audio signals

    Publication Year: 1993 , Page(s): 1926 - 1927
    Cited by:  Papers (2)  |  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (209 KB)  

    A simple and effective method is proposed for suppressing impulsive noise from audio signals with minimal high frequency loss. Suppression is accomplished by median filtering the contaminated signal sections. A gating signal that enables local median filtering is generated by an algorithm that involves impulse detection and recursive median filtering. View full abstract»

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  • Performance of a novel synchronisation algorithm over AWGN channels

    Publication Year: 1993 , Page(s): 1927 - 1929
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (307 KB)  

    Recently a novel symbol timing recovery technique that is implemented in the frequency domain has been presented. This technique is briefly described, where the performance of the time-error estimator under noisy conditions is assessed. Four different methods for time-error estimation are discussed, and the simulation results show that highly accurate estimates can be achieved. View full abstract»

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  • FFT-based algorithm for scattering from a circular, cylindrical shell in the presence of an inhomogeneous cylinder

    Publication Year: 1993 , Page(s): 1929 - 1930
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (214 KB)  

    An FFT-based algorithm is proposed to solve the problem of scattering from a homogeneous, thin, circular, dielectric cylindrical shell in the presence of an inhomogenous, cylindrical scatterer. The incident wave is taken to be transverse magnetic (TM); the problem considered is one of two-dimensional, scalar type. Results of computer simulations are provided illustrating the method proposed. View full abstract»

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  • Wave-orientated processing of scattering data

    Publication Year: 1993 , Page(s): 1930 - 1932
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (285 KB)  

    Windowed transforms applied to scattering data gathered along an elevated track parallel to a scattering surface are shown to provide local plane wave spectra which can be backpropagated to synthesise distinct features of the scattering environment. The method is illustrated for plane wave scattering from a truncated array of pitched strips. View full abstract»

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  • Universal active current filter with single input and three outputs using CCIIs

    Publication Year: 1993 , Page(s): 1932 - 1933
    Cited by:  Papers (12)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    A universal active filter with current gain and with single input and three outputs using second-generation current conveyors (CCIIs) is presented. The proposed circuit offers the following advantageous features: independent control of omega 0, Q and current gain through separate grounded resistors, use of only two grounded capacitors making it ideal for integration, and no requirements of critical matching condition/cancellation constraints in realising the lowpass, bandpass, highpass and notch filter responses. View full abstract»

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  • Adaptive mixed-rank filters

    Publication Year: 1993 , Page(s): 1933 - 1935
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    Proposes an adaptive median-type filtering scheme which is both computationally efficient and effective in suppressing impulsive noise from images without loss of image detail. A fast implementation is briefly discussed and comparisons with other filters are presented. View full abstract»

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  • AC-coupled complementary push-pull ECL circuit with 34 fJ power-delay product

    Publication Year: 1993 , Page(s): 1938 - 1939
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    The authors describe the first experimental result of a high-speed low-power ECL-based AC-coupled complementary push-pull circuit. Implemented in a 0.8 mu m high-performance fully complementary bipolar technology with 50 GHz n-p-n transistors and 13 GHz p-n-p transistors, a power-delay product of 34 fJ (23.2 ps at 1.48 mW) has been achieved compared with 67 fJ (45 ps at 1.48 mW) for the n-p-n only ECL circuit. View full abstract»

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  • Distribution shape of two-dimensional DCT coefficients of natural images

    Publication Year: 1993 , Page(s): 1935 - 1936
    Cited by:  Papers (71)  |  Patents (25)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    The univariate distribution of DCT coefficients of natural images is investigated. The probability density function (PDF) of the coefficients is modelled with the generalised Gaussian function (GGF) which includes the Gaussian and the Laplacian PDF as special cases. The shape parameter of the GGF is estimated according to the maximum likelihood principle. chi 2 tests of fit showed that GGFs model the distribution of DCT coefficients more accurately than Laplacian PDFs. View full abstract»

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  • Measurement of material properties with a tunable resonant cavity

    Publication Year: 1993 , Page(s): 1936 - 1937
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    A tunable resonant cavity is used to measure the complex permittivity of dielectrics and the surface conductivity of metals with high precision. The analytical approximations, traditionally used in the cavity perturbation techniques, have been replaced with a rigorous numerical solution of the electromagnetic field distribution inside the rotationally symmetric cavity filled with inhomogeneous dielectrics. The measured values of the unloaded Q factor are compared with the numerically computed values over the tuning range. The least-squares data fitting procedure yields simultaneously the values of the loss tangent and the surface conductivity, and their standard deviations. View full abstract»

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  • Coplanar-waveguide test fixture for characterisation of high-speed digital circuits up to 40 Gbit/s

    Publication Year: 1993 , Page(s): 1939 - 1941
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (297 KB)  

    For the characterisation of high-speed digital ICs, the standard test fixtures or test boards are usually realised with the microstripline configuration. The input and output impedance of the signal ports are well matched to 50 Omega . Because of dispersion, mutual coupling and reflections at taper sections, which are necessary to produce a change in linewidth in the region where the device is bonded into the test circuit, the performance is limited to the lower gigahertz region. To overcome most of these problems many investigations are being carried out using coplanar-waveguide (CPW) structures. The authors demonstrate the advantage of CPW lines and describe a successful design of a CPW test fixture with low dispersion, a minimum of crosstalk and low reflections suitable for data rates up to 40 Gbit/s. View full abstract»

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Electronics Letters is internationally renowned for its rapid communication of new developments and emerging topics across the broad and interdisciplinary field of modern electronics and electrical engineering.

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Meet Our Editors

Editors-in-Chief

Professor Chris Toumazou
Director of the Biomedical Institute
Imperial College, London, UK

Professor Ian White
Head of Photonics Research
University of Cambridge, UK