摘要:

At the Delft University of Technology a high-resolutionS-band f.m.-c.w. radar system for remote sensing of the troposphere has been built to extend knowledge about layered and turbulent structures in clear air and to investigate the reflectivity levels of hydrometeors. Design considerations and performance characteristics of the radar are given. Separate antennas for transmitting and receiving on one fully steerable mount are used. The signal processing is performed with a minicomputer and uses microprogramming to a large extent. Preliminary results are given to illustrate the potentials of the radar.

DOI:10.1049/ip-f-1.1980.0061

出版商:IEE    

年代:1980

数据来源: IET

摘要:

Few results have been obtained in the construction of convolutional self-orthogonal codes (c.o.s.c.s), except for difference set codes, until recently. A new infinite class of cyclically decodable c.s.o.c.s has been discovered which are multiple error-correcting at extremely high rates.1The paper presents new cyclically decodable c.s.o.c.s based on cyclic coset arrays.

DOI:10.1049/ip-f-1.1980.0062

出版商:IEE    

年代:1980

数据来源: IET

摘要:

A method for calculating the individual group congestion and the overall loss in a sequentially hunted skipped grading which is offered unbalanced traffic is presented. Based on Wilkinson's equivalent random theory, the paper offers two approaches to the solution of the blocking equations, one iterative, and the other making use of Rapp's approximations. The values produced by both are compared with those obtained from simulation for a number of different gradings.

DOI:10.1049/ip-f-1.1980.0063

出版商:IEE    

年代:1980

数据来源: IET

摘要:

Formulas are presented for the computation of error probability of OQPSK and MSK with narrow-band filters in transmitter and receiver and various detector filters (matched filter, sampling detector, rectangular filter and half-rectangular filter). Numerical results are computed for the case when the filters in transmitter and receiver are identical Butterworth filters. The error probability is presented as a function of signal/noise ratio or normalised filter bandwidth with the filter order as a parameter. The conclusion is that with narrowband filters, MSK with a sampling detector or half-rectangular detector filter and OQPSK with a sampling detector are the best systems. Although MSK is slightly better than OQPSK, the difference in performance is insignificant for the range of bandwidths of practical interest.

DOI:10.1049/ip-f-1.1980.0064

出版商:IEE    

年代:1980

数据来源: IET

摘要:

A closed-form solution to the buffer design problem is presented by studying a queueing model with a hybrid input traffic arrival process (mixture of Poisson and burst Poisson processes), synchronous output and single server with random interruptions. The queueing model developed is of unified nature as it includes Poisson and burst Poisson arrival processes and the mixture of the two as well. It is shown that, at a modified offered load, the empty buffer probability in an infinite buffer equals that of a finite buffer with actual offered load as its input. The modified offered load is shown to be equal to the carried load of the finite buffer. Thus, it is shown that the expression for the buffer-content state probability of the finite buffer of any length can be directly deduced from that of the infinite buffer, and hence various performance parameters can be evaluated. An integrated digital voice-data system is taken as an example for the model developed. The relationships among buffer size, overflow probability and average message queueing delay due to buffering are portrayed on graphs with the average burst length, the traffic intensity and the input traffic mixture ratio taken as parameters. It is concluded that the burst nature of the input traffic is a very important factor in the buffer design problem.

DOI:10.1049/ip-f-1.1980.0065

出版商:IEE    

年代:1980

数据来源: IET

摘要:

A series of experiments under nonfading and simulated-fading conditions has produced curves showing how bit error rate (b.e.r.) varies as a function of carrier frequency offset in a quasisynchronous data transmission scheme. Both direct and subcarrier f.s.k. modulation have been used and the experiments have led to an understanding of the physical mechanisms which cause errors. Click noise is the major cause in the nonfading case and at low carrier offsets with fading. At higher offsets, the response of the discriminator to the individual fades becomes dominant, with f.m. capture effect also having an influence. The error rate depends crucially on the response of the data demodulator to these effects, and different types of demodulator can be expected to produce quite different error rates.

DOI:10.1049/ip-f-1.1980.0067

出版商:IEE    

年代:1980

数据来源: IET

摘要:

The paper describes the use of the maximum-entropy method to estimate the Doppler shift of a moving target in the presence of additive white noise or coloured noise consisting of clutter plus white noise. Computer simulation results are included which show that in a background of additive white noise a Doppler processor based on the maximum-entropy method is only slightly suboptimal with respect to a conventional Doppler processor based on the discrete Fourier transform, whereas in the presence of additive clutter with a narrow spectral width (e.g. ground clutter) it is markedly superior in performance to the conventional processor for the case of low Doppler targets.

DOI:10.1049/ip-f-1.1980.0068

出版商:IEE    

年代:1980

数据来源: IET

摘要:

Radar echoes were observed from rain clouds in a range interval of 60 to 65.6 n mile, over an azimuth interval of 41.8° to 54.2° (range sweep number 400–519), above the sea. The variation in the distribution of clouds was examined over a 50s period. It is then shown that weather clutter obeys a Weibull distribution.

DOI:10.1049/ip-f-1.1980.0069

出版商:IEE    

年代:1980

数据来源: IET

摘要:

Various methods of diversity reception are considered as a means of reducing the errors in mobile radio data systems caused by fading and ignition noise. Data modems designed for subcarrier and direct modulation of the carrier have been built, and both binary f.s.k. and p.s.k. have been used. Three dualdiversity receivers utilising switched diversity, predetection combining and postdetection combining have been implemented, and their effectiveness has been tested in both laboratory tests and field trials at v.h.f. Significant reductions in bit error rate have been achieved.

DOI:10.1049/ip-f-1.1980.0070

出版商:IEE    

年代:1980

数据来源: IET

摘要:

A new scheme for the adaptive equalisation of incoherently demodulated signals is presented. In the scheme the output from an envelope detector is fed into a tapped-delay-line filter and simultaneously into a simple phase-estimating circuit. An estimate of the intersymbol interference is obtained and this is then subtracted from an estimate of the signal appearing at the input to the envelope detector to obtain an estimate of the transmitted data. The theoretical basis for the operation of the system is derived, and some results obtained when using the system to equalise time-varying channels are presented.

DOI:10.1049/ip-f-1.1980.0071

出版商:IEE    

年代:1980

数据来源: IET