摘要:

The theoretical bit error-rate prediction technique proposed by Bello and Esposito has been adapted to an FSK communication system employing a receiver which samples at the centres of received digits. Laboratory tests using a noise simulator capable of producing pulses with controllable amplitude, occurrence time and phase distributions have allowed verification of the predictions to be obtained within the range of impulse rates for which the error rate due to the contamination of an information digit by more than one noise pulse is negligible.

DOI:10.1049/ip-f-1.1981.0055

出版商:IEE    

年代:1981

数据来源: IET

摘要:

A previously developed technique for sampling FSK receivers has been extended so that it is applicable for average pulse rates up to several hundred per second when the pulse strengths are Rayleigh distributed. Laboratory tests have shown good agreement between predictions and measurements, and there are indications that the predictions based on an assumed Rayleigh distribution may be useful, as a guide, in some other cases.

DOI:10.1049/ip-f-1.1981.0056

出版商:IEE    

年代:1981

数据来源: IET

摘要:

The paper presents the analysis of a decision-directed tracking loop for a special class of input signals obtained by combining single-sideband modulation with class-4 partial-response signalling, which is well suited for data transmission. The analysis includes an evaluation of the phase function and probability density function of the phase error process for the loop. The theoretical results obtained are compared with computer simulation to verify the validity of this analysis.

DOI:10.1049/ip-f-1.1981.0059

出版商:IEE    

年代:1981

数据来源: IET

摘要:

Real-time signal processing applications are stimulating LSI chip designs for cost-effective digital filter implementations. One such device, the microprogrammable arithmetic element (MAE), is considered and its potential as a building block for different filter implementations is discussed. Direct-form and cascade MAE implementations of FIR and IIR filters are described and compared in terms of bandwidth, cost and chip efficiency.

DOI:10.1049/ip-f-1.1981.0060

出版商:IEE    

年代:1981

数据来源: IET

摘要:

The cosine transform is nowadays widely used in image data compression studies as a result of its observed near optimum performance with respect to variance redistribution andits property of reducing block edge effects which occur at extreme values of compression. The reason for its good performance for a widely used class of sources is now demonstrated theoretically by showing that it can be derived from the optimum (Karhunen-Loève) transform in the limiting case when the adjacent data-element correlation tends to unity.

DOI:10.1049/ip-f-1.1981.0061

出版商:IEE    

年代:1981

数据来源: IET

摘要:

In the paper, the effect of speech interference on the performance of long-loop phase-locked VHF SSB radio systems is evaluated, It is shown that unless the system's reference tone is adequately protected by suitable filtering in the transmitter's audio processing, the problem of ‘speech puffing’ may occur with severe degradationin intelligibility. Furthermore, residual FM modulation of the VCO's control line (the first local oscillator) through speech interference degrades the oscillator's output spectrum with possible reduction in adjacent-channel rejection. After analysing the effect of interfering sinusoidal signals on in-lock-loop per formance, filter design criteria are established for pilot-carrier and in-band-tone SSB systems, and the theoretically predicted results are verified experimentally. Finally, alternate phase-locked receiver configurations are suggested in an attempt to overcome first-oscillator spectrum degradation in long-loop receivers.

DOI:10.1049/ip-f-1.1981.0062

出版商:IEE    

年代:1981

数据来源: IET

摘要:

Fast and effective synchronisation of spread-spectrum modulated communication systems requires matched filtering in the receiver. The paper reports on the development of a spread-spectrum modem using surface-acoustic-wave devices to perform key processing tasks. The result is an efficient programmable matched-filter receiver well suited for burst-format message signalling.

DOI:10.1049/ip-f-1.1981.0063

出版商:IEE    

年代:1981

数据来源: IET

摘要:

The paper describes an AM and FM calibrator which produces AM and FM with a traceable accuracy and which can thus be used as a modulation standard. A PROM is used to store binary sequences which when filtered produce audio waveforms with precisely known characteristics. Using digital techniques, this PROM sequence can amplitude modulate or frequency modulate a carrier, resulting in AM or FM with a precisely known modulation depth or frequency deviation.

DOI:10.1049/ip-f-1.1981.0065

出版商:IEE    

年代:1981

数据来源: IET

摘要:

In the paper, two forms of feedforward automatic gain control circuit, i.e. lowpass and bandpass, are described and their performance limits discussed in respect of nonideal circuit parameters, receiver prefiltering decorrelation and propagation-medium time delay spread. The bandpass filter limited dynamics configuration is shown to have twice the fade suppression bandwidth of the lowpass filter limited dynamics form and is particularly suited for use in VHF and UHF full carrier AM and SSB mobile radio receivers. A series of field trials in which a bandpass limited dynamics feedforward automatic gain control circuit was fitted to the audio output of a 457 MHz SSB mobile radio system is described.

DOI:10.1049/ip-f-1.1981.0066

出版商:IEE    

年代:1981

数据来源: IET

摘要:

An automatic repeat request (ARQ) scheme which pre-empts the need for the retransmission of data is described. A detailed statistical analysis is carried out and numerical results are presented which show that, under a wide range of high error rate and/or long propagation delay conditions, considerable improvements in performance over the commonly used go-back-Nprotocol can be achieved with the scheme. The scheme has the advantage of being logically simple and should be capable of straightforward implementation as an extension of software handling the go-back-Nprotocol.

DOI:10.1049/ip-f-1.1981.0067

出版商:IEE    

年代:1981

数据来源: IET