摘要:

The gain/scan characteristics of four different types of dual-reflector antenna are compared. The theoretical analysis is based on the receive mode of operation in which geometrical optics, geometrical theory of diffraction and physical-optics technique are applied. Measured results of one of the designed antenna are found to agree well with prediction.

DOI:10.1049/piee.1977.0230

出版商:IEE    

年代:1977

数据来源: IET

摘要:

Investigation of the polarisation properties of scattered electromagnetic waves from spheroidal raindrops in the microwave region has resulted in the discovery of a resonance effect at 6 GHz. The behaviour of the scattering amplitudes and crosspolarisation of several drop sizes are shown. It is further shown that such effects occur at millimetre wave frequencies for ice particles, an example being given at 30 GHz.

DOI:10.1049/piee.1977.0231

出版商:IEE    

年代:1977

数据来源: IET

摘要:

A system of three computer programs is described which process data from far-field amplitude antenna pattern measurements to give partial and total directivity mappings (where ‘partial directivity’ refers to one polarisation only). The measurement data is acquired by sampling the radiation distribution over a spherical region enclosing the test antenna, first in one polarisation and then in the orthogonal polarisation, so that two ‘spheres’ of information are contained in a measurement data set. A small binary/decimal conversion program processes the two parts of the data set individually, and a data package with a heading containing measurement specifications is then set up. The data package is processed by the main program which integrates to find the isotropic level and then the partial and total directivities, and prints out the values in tabular form. As well as the conversion and main programs, there is an optional program that prints out the contents of the data package in an easily viewable form. This is useful if the input data contains errors.

DOI:10.1049/piee.1977.0232

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The effects of current-mirror emitter degeneration on monolithic Norton amplifier operation are described. The limits on practical improvement in noise performance obtainable are discussed. An active filter is used to illustrate the substantial noise reduction that can be achieved over standard handbook designs, and the predictions are verified experimentally.

DOI:10.1049/piee.1977.0235

出版商:IEE    

年代:1977

数据来源: IET

摘要:

A theoretical analysis is made on the titled subject as an extension of the classical theory (elaborated by H. Bremmer) of the ionospheric propagation. A physical parameter, which is akin to the conventional convergence or divergence coefficient introduced by Bremmer, is formulated in an approximate integral representation which is applicable at low to negative angles of departure/arrival, and the integral is evaluated by numerical means. Part of the result obtained from this analysis is further applied to the estimation of the interhop polarisation coupling factor, which has been formulated by G.J. Phillips and P. Knight. Striking features emerging from, and the adequacy of, the present analysis are demonstrated with a typical example.

DOI:10.1049/piee.1977.0236

出版商:IEE    

年代:1977

数据来源: IET

摘要:

New formulas are offered for the calculation of the performance parameters of halfwave and fullwave rectifiers: average output voltage, effective and peak values of diode current, peak-peak ripple and ‘trough’ value of output voltage (the lower extreme of the ripple). These are expressed in terms of the impedance and frequency of the a.c. source, the size of the reservoir capacitor and the load current or the load resistance, depending on which is in practice constant. The formulas are convenient provided that an electronic calculator is available.

DOI:10.1049/piee.1977.0237

出版商:IEE    

年代:1977

数据来源: IET

摘要:

A generalised conception of multi-interval integration for the solution of the problem of interference suppression in integrating analogue-digital (a.d.) convertors is presented. Three types of multi-interval integration are described namely nonoverlapped, overlapped and combined. The characteristics of a number of corresponding integration techniques are given in tabular form for several indices of performance particularly chosen for comparison. Special attention is devoted to the increase of the line-frequency suppression. For several integration techniques, an exceptionally high line-frequency suppression, practically without loss in conversion speed, is obtained. Aspects of realisation are also discussed.

DOI:10.1049/piee.1977.0238

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The paper discusses the application of differential pulse-code modulation (d.p.c.m.) and hybrid d.p.c.m./p.c.m. coding as a means of reducing the bit rate required for broadcast-quality System I (Pal, 625-line, 5.5 MHz) video signals. In the d.p.c.m. codes investigated, each codeword indicated the difference in magnitude between a sample of a video signal and a prediction of this sample based on samples already transmitted in the same and/or previous line periods with a sampling frequency equal to three times the colour subcarrier frequency. The codes examined required the transmission of between 3 and 6 bits per sample. Subjective test results are given for the picture impairment caused by quantising errors and transmission errors. The tests on quantising errors indicated that d.p.c.m. could provide a saving of nearly 2 bits per sample compared with p.c.m. A comparison of subjective test results and measurements of the r.m.s. quantising errors for d.p.c.m. and p.c.m. indicates that the picture impairment corresponding to a given signal/noise ratio is similar for both d.p.c.m. and p.c.m.

DOI:10.1049/piee.1977.0239

出版商:IEE    

年代:1977

数据来源: IET

摘要:

A novel method of regeneration of digital phase-modulated (phase-shift keying) signals is proposed, analysed and demonstrated using a parametric-subharmonic oscillator (p.s.o.) as a phase-script logic element. This technique of regeneration proceeds at carrier frequency without the need for down-conversion. An analysis of the switching performance of such regenerators is presented and applied to two specific circuit realisations. A switch-on time of 2ns and switch-off time of 1.5ns have been measured with a varactor diode p.s.o. at 8.2 GHz, hence demonstrating the feasibility of regeneration at 150 Mbits. A working regenerator is demonstrated at 4 GHz with a measurement of signal-to-noise/error-rate performance at 10 Mbits.

DOI:10.1049/piee.1977.0240

出版商:IEE    

年代:1977

数据来源: IET

摘要:

This paper deals with the crossmodulation in ring modulators. By means of an approximate calculation the effective half-value of the e.m.f. of the undesired signal at the input of the ring modulator, giving rise to a crossmodulation factor of 1%, is investigated as a function of the maximum available power of the oscillator. The results of the theory used here show very good agreement with the measurements.

DOI:10.1049/piee.1977.0241

出版商:IEE    

年代:1977

数据来源: IET