摘要:

A theory of cascade synthesis is presented in which the basic zero-producing sections (C, D and Brune) are extracted in a unified manner without recourse to nonreciprocal or nonphysical sections. The element values of the various sections are given explicitly in terms of the extracted zeros of transmission, the value of the impedance function and its derivative at the extracted zero.

DOI:10.1049/piee.1970.0132

出版商:IEE    

年代:1970

数据来源: IET

摘要:

A 7-bit p.c.m. encoder for television, applying the straightforward principle of successive approximation and feedback, has been realised using discrete components. Although the paper represents primarily a feasibility study, the results obtained encourage further investigation using thin-film and hybrid technology.

DOI:10.1049/piee.1970.0133

出版商:IEE    

年代:1970

数据来源: IET

摘要:

A multiplication procedure is described which may be applied to the polynomial forms of nonlinear feedback shift registers to enable two or more factor polynomials to be replaced by a single higher-order nonlinear feedback shift register. The sequential behaviour of the product-feedback shift register is shown to be related to that of its factors in that its sequences may be reproduced by a sequential circuit involving a cascade of the factor-feedback shift registers.

DOI:10.1049/piee.1970.0134

出版商:IEE    

年代:1970

数据来源: IET

摘要:

The unbalance in computing speeds of the various components of present hybrid computers places a constraint on the maximum iteration rate, and hence minimum solution times, that can be achieved. This is particularly true with the mode switching of operational amplifiers, where the main limitations of practical devices are those of accuracy and bandwidth.The design of a 2-mode switch is presented, the criteria chosen being 0.1% accuracy and 10kHz bandwidth. The switch comprises m.o.s.t.s used in the feedback path of a cheap monolithic amplifier. The stability of such a switch is analysed and it is shown that an improved performance can be achieved by the use of feed-forward techniques.

DOI:10.1049/piee.1970.0135

出版商:IEE    

年代:1970

数据来源: IET

摘要:

In media with characteristics possessing finite discontinuities, the field problem can be treated by solving a single wave equation, the effect of discontinuities being contained in the coefficients in the equation. This provides an alternative to the conventional approach, in which field quantities are matched at the discontinuities. Two examples with discontinuities in the transverse and longitudinal directions are investigated: one is a periodic structure loaded with dielectric discs, each having a central hole, and the second is a cavity with a solid dielectric disc partially filling the central region. For both examples, a general solution is described and a 1st-mode approximation given in detail.

DOI:10.1049/piee.1970.0136

出版商:IEE    

年代:1970

数据来源: IET

摘要:

A finite-difference method, using the transverse field components as variables, is developed for calculating the properties of waveguides containing nonuniform dielectrics. It is shown how an essential consistency condition in the discretisation may be satisfied. Results are given for the dispersion of the quasi-TEM waves and the cutoff frequencies of higher waves in some typical problems. Other methods of calculation are discussed, and, in particular, it is shown that the use of the axial field components as variables complicates the problem.

DOI:10.1049/piee.1970.0137

出版商:IEE    

年代:1970

数据来源: IET

摘要:

Very wideband TEM-mode transmission-line quadrature hybrids having a small phase ripple and optimum Chebyshev coupling can be realised by compensating the phase characteristics of optimum Chebyshev asymmetric 3dB couplers by means of allpass networks. Numerical results are given in detailed tabular form which enable hybrids with bandwidths up to at least 12:1 to be designed readily without resorting to tandem connections of two looser couplers. Experimental results for a decade-band hybrid show good agreement with the theory.

DOI:10.1049/piee.1970.0138

出版商:IEE    

年代:1970

数据来源: IET

摘要:

The application of the angular spectrum of plane waves, previously shown by Robinson, and Hamid for the problem of mode propagation in a rectangular waveguide loaded with a single E plane dielectric slab, is extended to an arbitrary number of slabs. The technique employs ray optics and residue calculus and is developed to the point where considerable theoretical advantages are evident when dealing with the more general case of a waveguide loaded with an arbitrary number of lossy or lossless dielectric slabs and excitation by a discrete set of propagating modes or inhomogeneous line sources. To illustrate the procedure for the case of three slabs, the dispersion equation for the modes in one slab is derived and the computed eigenvalues are verified by comparison with the recent results of Gardiol, based on a matrix boundary-value solution, and Kashyap and Hamid, based on a perturbation analysis. The transverse electric-field distribution is extended to the other slabs so that the boundary conditions at the interface of two planar dielectric slabs are satisfied. Plots of the transverse electric field due to propagating modes for a particular case are also presented and shown to converge when only the first few modes are considered. It is found that the frequency bandwidth, defined as the separation between the cutoff frequencies of the dominant and next highest-order mode, may be increased or decreased over the unloaded waveguide depending on the physical dimensions and relative permittivity of the slabs.

DOI:10.1049/piee.1970.0139

出版商:IEE    

年代:1970

数据来源: IET

摘要:

Diffraction theory has been used to analyse a symmetrically truncated right-angle corner in a previous paper by Lewin and Crain. An inspection of the diffraction fields radiated by the conducting wedges which define this configuration has given insight into the symmetries which should be exhibited by this waveguide junction. It is emphasised here that, in a closed waveguide structure, all interaction terms must be taken into account to converge to a reliable solution. This has not been the case in solving open structures such as conducting strips in free space or open-ended waveguide horns. It is also seen that special care must be taken to account for fields in penumbra regions. This analysis reveals a symmetry of higher-mode generation by the corner when the height is an integral number of half wavelengths which could not otherwise be seen.

DOI:10.1049/piee.1970.0140

出版商:IEE    

年代:1970

数据来源: IET

摘要:

An investigation into the performance of spherical-reflector antennas with Gregorian correctors is described with particular reference to their application in satellite-communications ground stations. Feeds comprising corrugated scalar horns propagatinga balanced HE11hybrid mode are considered, this choice eliminates cross-polarisation components of field in the spherical-reflector aperture. The theoretical performance of the spherical reflector with various subreflector profiles is estimated by using the aperture-field method to calculate the antenna-gain factor, far-field radiation pattern and overall efficiency as functions of the subreflector and feed positions. An optimum subreflector profile is chosen on the basis of maximum overall efficiency for a particular feed and antenna-scan angle. It is concluded that, for conventional scalar horns, the side-lobe level of the far-field radiation pattern is rather high, being about −11.5 dB with a corresponding gain factor of 0.85 and an overall efficiency of 0.65 for a scan angle of ±7°. Much lower side-lobe levels can be achieved, together with high gain factors, but only with lower overall efficiency. The spherical-reflector-antenna performance is compared to that of a front-fed paraboloid with the same feed and a higher efficiency is predicted for the former antenna. Preliminary consideration is given to the design of a dualmode feed so as to provide an additional tracking pattern, also to initial mechanical-design aspects.

DOI:10.1049/piee.1970.0141

出版商:IEE    

年代:1970

数据来源: IET