摘要:

A general formulation is given for the problem of electromagnetic scattering by an object havingNterminal pairs (or ports) to whichNloads or anN-port network is connected. The theory is applicable to back scattering and bistatic scattering, reciprocal and nonreciprocal media, near-field and far-field scattering and passive and active loads. The representation is made in terms of both open-circuit impedance parameters and short-circuit admittance parameters. Variational formulas for all parameters are given. Specialisation to the case of planewave scattering is made. Relationships between scattering parameters and commonly defined antenna parameters are given. Several examples of applications of the theory are included.

DOI:10.1049/piee.1964.0111

出版商:IEE    

年代:1964

数据来源: IET

DOI:10.1049/piee.1964.0112

出版商:IEE    

年代:1964

数据来源: IET

摘要:

A quasioptical theory has been developed to produce an approximate solution of an H plane right-angled corner in overmoded rectangular waveguide operating in the H10mode. From this, the mode conversion in the forward and backward directions, the loss due to mode conversion, the reconversion effects and the frequency response, have been deduced. Measurements were made on two corners in waveguides of different sizes both operating at around 8.6mm. These show good agreement with the theory.

DOI:10.1049/piee.1964.0113

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The ring-and-bar slow-wave circuit is analysed using an approximate field-theory approach. The analysis takes into account the effect of surrounding shields, finite bar thickness and dielectric supports. For those cases where a comparison with an earlier and more rigorous theory is possible (thin bars, no supports), the agreement obtained is excellent. Extensive computations of both dispersion characteristics and impedances have been carried out, and are presented in a series of graphs.

DOI:10.1049/piee.1964.0114

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The development of efficient thermoelectric semiconductors such aspandntype bismuth telluride has given rise to a variety of applications of thermoelectric cooling in the field of instrumentation.3,4This paper is concerned with the application of thermoelectric cooling to a load in which the heat produced, by the microwave power absorbed, is balanced by the heat extracted thermoelectrically. By this means the load may be maintained at the temperature of its surroundings, in which case extraneous heat transfer is reduced to zero. A restriction is applied to the temperature drop across the thermoelements used, and it is shown that the cooling power required to balance the microwave power may then be evaluated from the Peltier coefficient and two values of direct current.A simple form of waveguide termination is described to which distributed cooling is applied. It is concluded that the type of waveguide load required, to approach the inherent accuracy of the method, will be closely approached as the wavelength decreases into the millimetre band.

DOI:10.1049/piee.1964.0115

出版商:IEE    

年代:1964

数据来源: IET

摘要:

In time-compression multiplex (t.c.m.) transmission, the signals of the channels are scanned and the samples are stored before being transmitted at high speed. In this way, the signals of a large number of channels can be sent over a single transmission path. Methods of time-compression multiplexing that are described include the use of a cathode-ray storage tube, a delay-line store and a gated-capacitor store. The function of the store is to change the order in which the samples of the channels occur in time. In the transmitted waveform, samples are arranged in groups. Each group comprises consecutive samples from a single channel and is separated by a short interval from the next group containing samples of another channel.It is shown that t.c.m. transmission requires less bandwidth than time-division multiplex transmission. As the time of storage is increased, the bandwidth required for t.c.m. decreases towards that for frequency-division multiplexing (f.d.m.). For storage times of the order of 10ms, the bandwidth needed for t.c.m. is little greater than that needed for f.d.m.It is shown that bandwidth limitation introduces attenuation distortion and a form of interference that is called grouping noise. However, this noise can be practically eliminated by transmitting redundant ‘guard’ samples before and after the group of signal samples of each channel. Another source of noise is store-switching noise. This can be eliminated by interweaving the scanning sequences of the stores.The feasibility of t.c.m. transmission was demonstrated by experiments on model systems using gated-capacitor stores. The development of practical t.c.m. systems depends on the availability of suitable stores. It appears that the cathode-ray storage tube may ultimately be the solution, but currently available tubes are inadequate.

DOI:10.1049/piee.1964.0116

出版商:IEE    

年代:1964

数据来源: IET

摘要:

In time-compression multiplex (t.c.m.) transmission, the signals of the channels are scanned and the samples are stored before being transmitted at high speed. A store that can be used in t.c.m. systems is described in the paper. Each channel sample is stored as charge on a capacitor. These capacitors are connected to common input and output leads through diode gates.A theoretical analysis is made of the operation of the store. It is shown that its frequency response is adversely affected by residual charges left by previous samples. These can be removed by using erase pulses. The theory was confirmed by experiments on a model store with 32 storage elements per channel. The leakage current of the diodes used was found to limit the noise performance of the store.

DOI:10.1049/piee.1964.0117

出版商:IEE    

年代:1964

数据来源: IET

摘要:

In time-compression multiplex (t.c.m.) transmission, the signals of the channels are scanned and the samples are stored before being transmitted at high speed. In this way, the signals of a large number of channels can be sent over a single transmission path. The number of telephone channels that can be transmitted can be at least doubled by the process called time-assignment speech interpolation (t.a.s.i.). This exploits the fact that, on average, each channel in a multiplex telephone system is transmitting speech for less than half the time.The addition of t.a.s.i. facilities to a t.c.m. system is relatively simple because the main t.a.s.i. requirement (switching of all speech signals) already exists as an inherent part of any t.c.m. system. Furthermore, the extra information which has to be transmitted (the channel identification information) can be incorporated in the standard t.c.m. signal with very little change in the bandwidth requirements.The simplest t.a.s.i. systems favour the lower-numbered channels, so that, in the event of more channels being active than there are transmission slots available, the same higher-numbered channels are always ‘frozen out’. In order to overcome this difficulty, a queue-control system is necessary. It can be made to balance the overload conditions such that the queuing channels always accept the back of the queue in time rotation. A queue controller for a t.c.m.-t.a.s.i. system consists of a logical array of conventional binary stores, gates and shift registers.

DOI:10.1049/piee.1964.0118

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The method of increasing the rate of transmission of information in block-coded digital systems, known as case coding, is analysed. The rate increase may be positive or negative depending on the number of messages, their selection probabilities and the coded output-symbol alphabet. The treatment is not restricted to binary alphabets. Problems in the implementation of the coding system, such as storage capacity, are discussed and a workable method of encoding is presented.

DOI:10.1049/piee.1964.0120

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The paper describes a novel form of magnetic-tape playback head which responds selectively to a particular wavelength of recorded signal. The use of this head is described for spectrum analysis and for detecting marker signals on standard tape recordings.

DOI:10.1049/piee.1964.0121

出版商:IEE    

年代:1964

数据来源: IET