DOI:10.1049/ree.1979.0024

出版商:IERE    

年代:1979

数据来源: IET

摘要:

A 13.57–15.0 GHz sweep measurement equipment designed to measure amplitude, differential phase, and differential gain of a propagation path is briefly described, and the qualities of the data are discussed. Statistics of fadings and intermodulation noise in the frequency band of 13.6 to 14.9 GHz from a 45 km l.o.s propagation path in Denmark are presented. The statistics cover the period July 1974 to July 1975. Both monthly and diurnal variations of the fading are given as well as the distribution of the fading durations. Separate statistics are given for multipath propagation and for precipitation attenuation. Distributions of the 1 minute and the 1 hour mean values of total noise power for the whole period, and for the worst month are presented. The monthly variations of these values are also presented. Based on the data it is concluded that this propagation path will satisfy the relevant part of the CCIR Recommendation 395–1, concerning the transmission quality in the worst month—provided the antennas are protected against wet snow and the system uses some type of diversity to cope with multipath propagation.

DOI:10.1049/ree.1979.0025

出版商:IERE    

年代:1979

数据来源: IET

摘要:

A potentially low cost amplifier module has been made using transistor chips with thin film, beam lead or chip components in a hybrid microwave integrated circuit.The design of this amplifier demonstrates a technique which has been devised to obtain input power match with minimum noise figure. This uses feedback to achieve the power match whilst maintaining, at the transistor input terminals, the source impedance required for minimum noise figure. The amplifier uses transistor chips from low-noise ‘slices’ of the Mullard BFR90, which, without feedback, would give a mismatch (v.s.w.r.) of > 3: Over a bandwidth of 300 MHz, centred on 1.5 GHz, the coincident conditions have been achieved, resulting in an amplifier noise figure of 3.5 dB and input v.s.w.r. < 1.25:1 for 50 ohm source. The gain of the two-stage matched amplifier is between 16 and 12 dB from 1.1 to 2.4 GHz.

DOI:10.1049/ree.1979.0026

出版商:IERE    

年代:1979

数据来源: IET

摘要:

The British Post Office is introducing digital transmission equipment into its telecommunications network. The opportunity arises to take advantage of plant to be installed for telephony purposes to act as bearer plant for non-speech services, e.g. digital data. The per-voice channel capacity of a digital system is known as a channel time-slot and this paper describes how access might be gained to this capacity for use by non-telephony services.

DOI:10.1049/ree.1979.0027

出版商:IERE    

年代:1979

数据来源: IET

摘要:

The methods by which the local oscillator signals for use in a modulation-type sector-scanning sonar system may be produced are briefly reviewed. To achieve good performance in practice, it is often necessary to incorporate many adjustments in the system. An alternative system employing mainly digital techniques is considered, the analysis of which reveals the potential for improvements in performance. A sector-scanning sonar requiring few adjustments has been constructed using these techniques.

DOI:10.1049/ree.1979.0029

出版商:IERE    

年代:1979

数据来源: IET

摘要:

A new class of all-pole transfer functions for pulse-forming networks based on the use of generalized Laguerre polynomials is introduced. It is shown that the two variable parameters, which are available with the generalized Laguerre polynomials, can always be adjusted so as to obtain an impulse response with any prescribed attenuation of transient overshoots. These filters, which may be referred to as generalized Laguerre filters, are shown to include as special cases Bessel filters, Gaussian filters and a recently derived class of transitional filters utilizing modified Bessel polynomials. A comparison with the Schiissler filters, designed for impulse response with equal ripple transient ringing is also presented. Tables are presented giving the pole locations of these filters for n = 3–7 and the transient overshoot attenuation of 20–60 dB in steps of 10 dB. Normalized element values for LC ladder realization with equal resistance terminations are also included.

DOI:10.1049/ree.1979.0030

出版商:IERE    

年代:1979

数据来源: IET