摘要:

The paper outlines the principles behind an approximating frequency synthesizer based on continued fractions to derive the data required for the addressable counters of the digital phase-locked loops. A hardware implementation is described based on a cheap microprocessor and calculator chip combination for the digital content and integrated circuit phase-locked loops for the analogue section. The prototype operates over the frequency octave 400<f<800 kHz with a resolution of 0.1 Hz.

DOI:10.1049/ree.1978.0080

出版商:IERE    

年代:1978

数据来源: IET

摘要:

Test signals consisting of a set of composite sinusoids have found increasing application recently in the non-linear control system testing field. This paper presents a new approach to the implementation of a multifrequency signal generator capitalizing on recent advances in digital techniques. The instrument generatesNsinusoids of programmable relative frequency over a very wide dynamic range, in excess of 10−4to 104Hz. Relative phase shift and amplitude ratio are also programmable. The new technique makes possible relative frequency jitter of zero as well as identical and low noise content for allNsinusoids. Extensive simulation studies have fully established zero relative phase error, and zero relative harmonic ratio error; both being prime conditions for accurate multifrequency test signals.

DOI:10.1049/ree.1978.0081

出版商:IERE    

年代:1978

数据来源: IET

摘要:

A common requirement in the design of data transmission filters is to provide a relatively large impulse (or pulse) response att=t0, and near-zero responses att=to+k(kany integer), in order to minimize intersymbol interference. The solution to this problem for impulsive inputs has been reported recently. This paper extends the results to pulse-type inputs. Numerical examples are given.

DOI:10.1049/ree.1978.0082

出版商:IERE    

年代:1978

数据来源: IET

摘要:

A simple mathematical model is used to predict co-channel and adjacent channel interference effects in land mobile radio, valid for flat urban terrain. Results obtained, although oversimplified compared with real-life mobile radio systems, yield insights into the properties of differing types of modulation.

DOI:10.1049/ree.1978.0083

出版商:IERE    

年代:1978

数据来源: IET

摘要:

The near-field broadside coupling between a pair of two-dimensional H-plane sectoral horns is derived using the method of overlapping regions in conjunction with Schwarz's procedure to solve the resulting integral equations by numerical iterations as well as the generalized scattering matrix technique. The primary advantage of the method is that it allows an arbitrary initial assumption of the aperture field distribution and reasonably corrects it in order to take into account the multiple scattering effects. It is shown that only a few iterations are required for typical coupling geometry and that the number of iterations and the convergence of the series' computations are improved for shorter horns and closer separation distances. Graphical results for the aperture field distributions for specific geometries are presented.

DOI:10.1049/ree.1978.0084

出版商:IERE    

年代:1978

数据来源: IET