摘要:

The paper gives a simple method of estimating the mutual interference that may arise between an earth station of a communication-satellite system and neighbouring line-of-sight radio-relay stations using the same frequency band, and suggests criteria for deciding whether a proposed mode of earth-station operation is compatible with the maximum permissible values of telephone-channel interference noise recommended by the CCIR. The effect on the interference of the motion of the earth-station aerial is considered in some detail for the principal types of orbit that the satellites being tracked might occupy. A number of examples are included to illustrate the application of the method to an earth station handling high-capacity f.d.m./f.m. transmissions in the 4Gc/s and 6Gc/s communication bands.

DOI:10.1049/piee.1965.0035

出版商:IEE    

年代:1965

数据来源: IET

摘要:

The excitation efficiencies due to a magnetic line source of the first four vertically polarised guided modes below a lossless sharply bounded ionosphere are investigated, for the case of propagation transverse to the external magnetic field. It is found that then= 0 mode is essentially a surface wave guided by the ionosphere/free-space boundary. Also, the results show that, for a source near the ionosphere boundary, the excitation of then= 0 mode can be several orders higher than that of then= 1 mode, even at the higher end of the v.l.f. range, with the result that then= 0 mode can become important in the guidance of energy at the higher end of the v.l.f. band for considerable distances from the source compared with that of then= 1 mode.

DOI:10.1049/piee.1965.0036

出版商:IEE    

年代:1965

数据来源: IET

摘要:

The radiation characteristics of an axially oriented electric dipole in an isotropic plasma column are investigated. Surface waves are found to be excited for frequencies of less than 1/√2 times the plasma frequency. The dependence of the power carried by the surface wave, as well as that carried by the space wave, on the frequency and the radius of the plasma column is examined. The surface waves are found to be excited with maximum efficiency at about half the plasma frequency. The radiation pattern in the far zone is evaluated and found to have, in general, a maximum in the broadside and a null in the end-fire directions. The normalised radiation resistance is found to vary as the square of the frequency for small column dimensions and high frequencies.

DOI:10.1049/piee.1965.0037

出版商:IEE    

年代:1965

数据来源: IET

摘要:

A description is given of measured field-strength characteristics on 186 and 174Mc/s over distances of 140 and 300km, respectively. The fading characteristics on the shorter path are consistent with the assumption that three propagation modes can be detected: a ground wave, a wave reflected at an elevated layer and a scattered component. The cumulative field-strength distribution can be interpreted in terms of the distribution of the mode components. On the longer path, the optimum layer height, corresponding to the greatest signals, is about half that of the intersection point of horizon rays on a 4/3-earth profile.No significant correlation was observed on either path between surface refractive index and monthly median field strength.

DOI:10.1049/piee.1965.0038

出版商:IEE    

年代:1965

数据来源: IET

摘要:

Closed-form expressions for the current distribution and impedance of an antenna in a parallel-plate region have been obtained by an integral-equation technique. The current distribution reveals a logarithmic singularity in the neighbourhood of the driving point because of the current emanating from the idealised delta-function generator. The effect of the feed-point singularity on the antenna characteristics has been investigated both theoretically and experimentally. Contrary to assumptions made by previous workers, it has been shown that the logarithmic term makes a marked contribution over a significant length of the antenna; a large empirical ‘gap correction’ is also shown to be necessary to bring the admittance of the theoretical model into good agreement with the experimental results. The implications and limitations involved in assuming an idealised delta-function generator for driving the antenna are discussed. The paper also accounts satisfactorily for certain anomalies in the behaviour of the antenna at resonance, which were noticed earlier by Lewin.Extensive experimental measurements have been made on the antenna, and a description of the apparatus is included in the paper. The experimental results agree well with theory.

DOI:10.1049/piee.1965.0039

出版商:IEE    

年代:1965

数据来源: IET

摘要:

We here consider electromagnetic waves guided by a plane surface impedance which is modulated periodically in time and space in the travelling-wave sense. The problem treated is a linearised statement of the nonlinear parametric interaction of waves on an open waveguide structure. In this linear treatment we take the rigorous approach formerly used on purely spatial periodic structures. We examine parametric-wave interactions of both the stable and the potentially unstable type. The regions of operation for bound surface waves, as opposed to radiating leaky waves, are determined rigorously for this structure. A region of operation called the ‘sonic’ region is found, which represents a form of an electromagnetic shock wave. This sonic region precludes, for the model chosen, the possibility of travelling-wave amplification along the length of the structure. The above results are obtained only from the complete treatment, including the effects of all time-space harmonics. Finally, the power-mixing principle for all harmonic waves is determined to be the Manley—Rowe power/frequency relation applied at the boundary surface.

DOI:10.1049/piee.1965.0040

出版商:IEE    

年代:1965

数据来源: IET

摘要:

Practical comparisons of magnetic-film storage cells suitable for word-organised matrixes show that the usual cell, formed by the orthogonal intersection of one word conductor and one digit conductor (1W1D), can be replaced advantageously by a cell involving a pair of word conductors, carrying opposite currents, and a single digit conductor (2W1D). Compared with 1W1D cells, 2W1D cells tolerate more skew of the easy axis of the film; interactions between 2W1D cells in adjacent words are substantially lower, and those between adjacent cells in the same word are similar; and noise during reading of 2W1D cells is low, whether coupling between word and sense conductors is due to capacitance or to distortion in substrate eddy currents near plate corners.A 2W1D-matrix module has been made that is compatible with a previously described 1W1D module.

DOI:10.1049/piee.1965.0041

出版商:IEE    

年代:1965

数据来源: IET

摘要:

A new tristable circuit is described. It is basically an Eccles-Jordan circuit arranged to have a third stable state in which both transistors operate in the active region. Switching from this centre-stable state to either of the other two states can be arranged to occur at a well defined level of triggering current. The circuit is particularly suitable for use as an output latch with certain types of digital-computer store or in ternary-logic circuits. The effects of component and supply-voltage tolerances are discussed.

DOI:10.1049/piee.1965.0042

出版商:IEE    

年代:1965

数据来源: IET

摘要:

Group-delay equalisers operating at microwave frequencies may find application in multicharinel-telephony radio-relay systems, e.g. in systems without translation to an intermediate frequency in repeaters. Studies to ascertain the feasibility of such equalisers operating in the 4 Gc/s band are described. Several equalisers have been designed and constructed in standard waveguide WG11, using a pair of identical bandpass ladder networks terminating a waveguide hybrid or a 3dB directional coupler. In all cases except one, the equalising networks had delay characteristics that were arbitrarily assumed; the exception was a network designed to equalise the group-delay performance, over a bandwidth of 20 Mc/s, of a pair of bandpass filters in tandem. Basic equaliser insertion losses of 0.5–2dB have been observed, the figure depending on the complexity of the network. The effect of temperature changes on the equaliser and filters in tandem resulted in the midband frequency of the equaliser shifting in step with the frequency of the filters, so that the group-delay performance remained equalised over a temperature range of 20degC. It is concluded that, although the performance of the equalisers is satisfactory, they are less flexible in operation and are mechanically bulky compared with intermediate-frequency equalisers.

DOI:10.1049/piee.1965.0043

出版商:IEE    

年代:1965

数据来源: IET

摘要:

TheQfactor of differentRCnetworks, commonly employed in anRCoscillator, has been the criterion of their selection for providing high frequency stability to the oscillator. In this paper, it is shown that the network with the highestQfactor does not provide maximum frequency stability in an oscillator with dual feedback paths. The parameters for optimum stability have been obtained for differentRCnetworks when used in an oscillator with dual feedback paths.

DOI:10.1049/piee.1965.0044

出版商:IEE    

年代:1965

数据来源: IET