DOI:10.1049/ji-3a-1.1946.0203

出版商:IEE    

年代:1946

数据来源: IET

摘要:

A description is given of a pulse-testing equipment for wide-band networks, together with examples of practical applications.The equipment contains a pulse generator, a time base with a display unit, and an amplifier preceded by an exploring probe-head. The pulse generator produces three types of pulse: one of length 0.02 microsec and amplitude 35 volts in a cable of 35 ohms; one of length 0.01 micro-sec and small amplitude; and one of amplitude variable from 50 microvolts to 0.5 volt. The time base produces a slow scan and a fast scan (5.0 microsec and 1.0 microsec sweep respectively). A phase shifter provides a continuous adjustment of the position of the pulse response along the trace. The main features of the amplifier are its wide band (32 Mc/s), its high gain (13.5 db per stage) and the adjustable capacitance attenuator in the probe head, which permits of the very low input capacitance of 1.8 μμF at maximum attenuation.The equipment is specially designed for the pulse testing of wide-band networks. The shape of the pulse response gives a great deal of information on the characteristics of the networks, which can usually be obtained only by laborious attenuation and phase measurements. Some typical examples are given:(a)Testing of lines and feeders; study of irregularities in cables and correct matching.(b)Testing of delay lines.(c)Testing of band-pass filters and relations between the pulse response and mismatch.(d)Testing of aerials and mismatching between feeders and aerials.(e)Study of feedback amplifiers. It is shown that the shape of the pulse response gives information on the degree of stability of the amplifier and on the frequency at which it may oscillate. This application is a typical example of the versatility of the pulse-testing technique.

DOI:10.1049/ji-3a-1.1946.0204

出版商:IEE    

年代:1946

数据来源: IET

DOI:10.1049/ji-3a-1.1946.0205

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The increasing number of radar sets employed in a large warship makes it desirable to synchronize the outgoing pulses in such a manner as to present them simultaneously on the various displays. The paper describes the development of a Master Trigger Unit for this purpose.While the unit in its final form was of specialized application, its design exemplifies a number of useful circuit techniques of general interest.

DOI:10.1049/ji-3a-1.1946.0206

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The paper describes a high-precision circuit for radar ranging which uses the now well-established method of controlling the range timing marker by means of a linear, continuous phase-shifting circuit. Its special features are the use of a pulsed quartz-crystal oscillator as the timing standard and the elimination of the separate, medium-precision timing circuit usually employed to select one range marker from the array potentially offered by the phase-shifting circuit.Appendices deal with some of the factors involved in the design of the circuit.

DOI:10.1049/ji-3a-1.1946.0207

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The paper discusses the design of special radar circuits for use where reduced weight and enhanced reliability are desired. It is concluded that in such instances the circuits form the core around which the rest of the design must be framed. Some of the problems which face the circuit designer are elaborated, the use of pulse ratings, tropic-proofed materials and miniature valves being particularly noted. Circuits are given which illustrate methods of material and dissipative economy. Mention is made of ancillary gear and of the importance attached to careful choice of the source of power, and its precise nature.

DOI:10.1049/ji-3a-1.1946.0208

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The Plan-Position Indicator (P.P.I.) is a form of radar display which gives a map-like presentation of the echoes from objects in the vicinity of the radar set. The antenna system of the radar set is highly directional and the beam is continuously rotated in order to give full angular cover. The display is generated by rotating about its starting point a time base which is intensity-modulated by the echo signals: the rotation is synchronous with the antenna rotation. The systems described in the paper were developed for use with airborne radar equipments in which the time-delay of the echoes is proportional to the distance from aircraft to reflecting object. This distance is called the slant range, whereas the range that it is required to display is the distance from the reflecting object to a point on the ground immediately below the aircraft, this distance being called the ground range. The correction to be applied to the delay time is a function of height and slant range and the paper describes several “height-correction” circuits.The display obtained in the aircraft will normally move across the face of the cathode-ray tube at a rate proportional to the velocity of the aircraft and some blurring of the presentation will therefore occur. Circuits are described which eliminate this motion of the display by shifting the centre of the display at a rate proportional to aircraft velocity, arrangements also being made, if desired, to maintain the North direction of the map-like presentation at a fixed angle on the tube for easy comparison with maps.The first part of this paper discusses methods of obtaining these displays using electrostatically-deflected tubes. The second part describes corresponding developments using electro-magnetically-deflected tubes. In each case several methods are described in outline and one in some detail.

DOI:10.1049/ji-3a-1.1946.0210

出版商:IEE    

年代:1946

数据来源: IET

DOI:10.1049/ji-3a-1.1946.0211

出版商:IEE    

年代:1946

数据来源: IET

摘要:

Automatic strobes and recurrence-frequency selectors are both systems devised for radar purposes in which a locally-generated repetitive pulse, called a “strobe,” is held in coincidence with an incoming repetitive pulse. In the automatic strobe, the incoming pulse is an echo of a pulse transmitted by the radar set. The function of the apparatus is that of holding the time interval elapsing between the occurrence of the transmitted pulse and the strobe pulse equal to that elapsing between the transmitted pulse and the echo pulse. This result is achieved by controlling the delay time between the transmitted pulse and the strobe pulse. The system may be used to indicate the range of a given echo continuously, since this delay time is a measure of the range of the object producing the echo. The circuit arrangements used allow the wanted echo to be selected from among others present at different ranges. Any modulation present in the selected echo may, therefore, be detected without interference from the others, which are rejected.In the recurrence-frequency selector, incoming pulses are not, in general, echoes, but are pulses received from a remote transmitter with a basically fixed repetition frequency which may, however, have small amounts of frequency- or phase-modulation superposed. In these circuits there is no local transmitter pulse, and the strobe pulses are derived from a local self-oscillator. The requirement is still to hold strobe pulses and incoming pulses in coincidence, but now the result is achieved by controlling the frequency of the local oscillator.In both cases a device is needed to detect the error in the timing of local pulses relative to the incoming pulses; this device is called a time discriminator, and practical examples are given. The resulting error signal is used to control either the delay time between transmitter and strobe pulses, or the frequency of the local oscillator.Both systems are analogous to automatic control systems met with in other branches of engineering, and after a brief introduction the paper goes on to summarize that part of the mathematics of control systems that is relevant to these particular applications. It is shown that some “processing” of the error signal is necessary before it can be used to give stable control with desirable characteristics. This processing is performed in a “function unit” and the various mathematical forms it can take are outlined. The realization of these forms is then discussed; feedback amplifiers are used for the purpose and suitable types are described in some detail.In both parts of the paper the closing Sections contain descriptions of practical circuits with some design detail. The predicted performance is verified experimentally.

DOI:10.1049/ji-3a-1.1946.0212

出版商:IEE    

年代:1946

数据来源: IET