摘要:

Intersymbol interference and timing extraction are crucial design factors in efficient digital transmission systems. The paper investigates the use of multisegment pretransmission pulse coding to control intersymbol interference, combined with high timing content line coding to ensure reliable low jitter self timing. Analysis and measurements (on a metallic-pair cable) are then used to make comparisons between various combinations of pulse and line coding methods.

DOI:10.1049/ip-i-2.1990.0001

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The authors propose to combine adaptive equalisation and differentially coherent reception. An appropriate LMS algorithm is deduced to adapt the equaliser. We determine the optimum equaliser coefficients which minimise the mean-squared error between the input to the threshold detector and the desired symbol. The system of equations to solve is not linear as in the coherent reception. It is of the third order and requires computer calculations. The error probability of the differential detector with and without equaliser is calculated for BPSK. Simulation results are also given.

DOI:10.1049/ip-i-2.1990.0002

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The theory of threshold reception in non-Gaussian noise is applied to synthesise a locally and asymptotically optimum diversity structure for the noncoherent reception of binary frequency-shift keying signals subject to amplitude fluctuations. The optimum threshold decision rule is obtained for arbitrary slow-fading laws on the diversity branches.With reference to Rayleigh distributed amplitude fluctuations, the performance of the proposed reception structure is evaluated for the general case of arbitrary noise distributions on the diversity channels.

DOI:10.1049/ip-i-2.1990.0003

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The behaviour of a first-order phase-locked loop is critically examined under conditions where it is tracking a carrier corrupted by discontinuous (square-wave) amplitude modulation. The transient response of the system is first derived for the simple case of a PLL without time delay, and a comparison is made with a series of practical results obtained from a first-order loop. The agreement between the predicted response and that observed in practice is found to be extremely good. The theoretical behaviour of the loop is further analysed for the case of a system incorporating time delay. It is shown that such delay is detrimental to the tracking performance of the loop, when it is necessary to track a carrier modulated in the manner outlined above.

DOI:10.1049/ip-i-2.1990.0004

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The paper describes a number of acquisition-aid schemes applicable to a tracking receiver, and discusses the relative merits of each, when applied to the proposed new split-loop tracking receiver. It is demonstrated that the more conventional designs of acquisition aid, currently in use on long-loop receivers, are less than optimum when applied to a split-loop receiver. A novel form of sweep acquisition aid, incorporating a feedback correction system, is described for application to a split-loop receiver. The operation of the system is described mathematically, along with its practical implementation and operation in an actual tracking receiver. This scheme is also shown to be applicable to conventional long-loop receivers.

DOI:10.1049/ip-i-2.1990.0005

出版商:IEE    

年代:1990

数据来源: IET

摘要:

We derive an expression for the error probability ofM-ary frequency shift keying with differential phase detector and narrowband receiver filter in the satellite mobile (Rician) channel which includes as special cases the Gaussian and land mobile (Rayleigh) channels. We compute the error probability as a function of various system parameters forM= 2, 4 and 8 symbols and the third order Butterworth receiver filter. The error probability increases with Doppler frequency and with the shift of the channel from Gaussian through Rician to Rayleigh. The optimum normalised bandwidth per bit is in the vicinity of one and the optimum modulation index for binary symbols is about 0.6. The threshold for quaternary symbols can be optimised to about 0.9 of the modulation index. For Rician and Rayleigh channels with non zero Doppler frequency there is an error floor, therefore may require diversity or coding in order to achieve a desired error probability.

DOI:10.1049/ip-i-2.1990.0006

出版商:IEE    

年代:1990

数据来源: IET

摘要:

In the paper a method is presented for the removal of impulsive disturbances from noisy speech and musical signals. The algorithm is based on a detection-interpolation scheme. The design of the impulsive noise detector subsystem is motivated by the observation that linear prediction systems are quite adequate for the modelling of speech signals whereas they can not model impulsive disturbances. It is shown that transforming the speech signal to the glottal excitation may result in significant reduction of the scale of the speech signal to almost that of the excitation signal whereas the scale of impulsive noise does not decrease. This can lead to a significant improvement in the detectability of the noise pulses. Further improvement may be obtained by the application of a matched filter to the noisy excitation signal. The signal samples that are obliterated by impulsive noise are discarded and interpolated. The interpolation method produces a least squared error estimate of the missing samples using speech samples in the vicinity of the missing block and an estimate of the LPC model of the signal. It is shown that the performance of the interpolation system improves significantly when the LPC model incorporates long term correlation structure in addition to the usual short term correlation parameters.

DOI:10.1049/ip-i-2.1990.0007

出版商:IEE    

年代:1990

数据来源: IET

摘要:

A new algorithm for detecting and/or decoding of signals in communication system is presented. The advantage of the proposed suboptimum algorithm with respect to the classical maximum likelihood detection (MLSE) method lies in the significant reduction in computation complexity attainable by associating a reliable information to each received signal. At the same time, the error probability is maintained close to MLSE levels through the proper selection of the reliability information. We describe the application of the proposed algorithm to some interesting cases, such as the detection of continuous phase modulations with and without combined channel coding, detection of Ungerboeck codes, use in conjunction with the Viterbi algorithm. In all cases, a net reduction in computation complexity with respect to the classical MLSE algorithm is achieved.

DOI:10.1049/ip-i-2.1990.0008

出版商:IEE    

年代:1990

数据来源: IET