DOI:10.1049/piee.1963.0001

出版商:IEE    

年代:1963

数据来源: IET

DOI:10.1049/piee.1963.0002

出版商:IEE    

年代:1963

数据来源: IET

摘要:

The ultra-sound image camera enables a visible image to be reproduced of the ultra-sound intensity distribution on the camera face. Coupled with acoustic lenses, and immersed in a suitable medium, the internal structure of substances or objects transparent to ultrasonic waves can be studied with the instrument. In its uses it is complementary to X-ray and to ultrasonic pulse-echo inspection methods. It has applications to the non-destructive testing of materials and engineering components, and also to medical diagnosis.An ultra-sound camera tube and complete viewing equipment have been built. The sensitivity for unity signal/noise ratio is 10−7W/cm2at the camera face, and the resolution is 0.5 mm at 4 Mc/s. It is one of several possible types of ultra-sound camera. The design is discussed, and directions into which further research and development might be taken are also considered.

DOI:10.1049/piee.1963.0003

出版商:IEE    

年代:1963

数据来源: IET

摘要:

The effect of ambient-temperature variations on the running voltage of a glow-discharge reference tube is considered. Previous theories by Jurriaanse and Benson and Chalmers have been modified to provide a new and more accurate method of calculating temperature coefficients of running voltage. To verify the theory it has been necessary to determine running-voltage changes with tube current for different pressures and temperatures using pure neon and various neon-argon gas fillings. The results of these measurements are presented and discussed, and have formed a basis for numerical calculations of some temperature coefficients.

DOI:10.1049/piee.1963.0004

出版商:IEE    

年代:1963

数据来源: IET

摘要:

The paper describes a jig primarily intended for the rapid measurement of the modulus of near-shortcircuit current gain of transistors in the frequency range 20–1000 Mc/s (though phase can also be measured if suitable phase-comparison gear is available). The jig needs no internal tuning adjustments and uses 5 Ω terminating resistors, so that the corrections needed to give true short-circuit current gain are usually negligible with present-day transistors. The plane of measurement is defined to an accuracy of about 1 mm and the measuring resistors are extended to this plane by means of suitable transmission lines. The transistor leads are accommodated in deep drillings, so that measurements can be made close to the transistor header without cropping leads. A novel method of current injection, using a double coaxial system, simulates an input transformer. Measurements made with a short-circuit from input to output terminals showed jig errors less than 0.2 dB over most of the frequency range, rising to about 0.5 dB at 1000 Mc/s. The paper describes constructional details of the jig, gives examples of measurements made with it, and describes a method, using a second jig, by which phase may be measured.

DOI:10.1049/piee.1963.0005

出版商:IEE    

年代:1963

数据来源: IET

摘要:

In connection with an investigation of r.f. discharges in magnetrons the measurement of interconductor voltage and lead current in the magnetron output by comparative methods using capacitive and loop probes is discussed. In practice loop-probe measurements are difficult to interpret, and an estimate of the current may not be possible. Some uncertainties may be avoided by representing the magnetron output by an equivalent circuit whose constants can be found from the probe measurements, and from which the current and voltage can be calculated.In the paper equivalent-circuit constants for a magnetron having a coaxial output are derived from ‘cold’ probe voltage measurements carried out using matched, short-circuit, and constant reflection terminations. The voltage and current at certain points in the valve are calculated for the power output and loading conditions under which discharges were observed in oscillation tests.The circuit representation is general, and the methods may be applied in principle to magnetron or cavity outputs different from the one described.

DOI:10.1049/piee.1963.0006

出版商:IEE    

年代:1963

数据来源: IET

摘要:

The investigation of switching and oscillation phenomena in tunnel diodes has a number of problems associated with it, one of which is the practical difficulty of observing the resulting fast waveforms. The analogue described in the paper facilitates the observation of these waveforms by slowing them down by several orders of magnitude. The parameters of the analogue are easily variable, thus enabling the tolerance of circuits to variations in tunnel-diode parameters to be readily ascertained. Further, the large magnitude of the parameters and the small bandwidth permit investigations of stability criteria, non-linear oscillations and switching to be carried out with ease.The linear stability criterion has been verified and demonstrated experimentally by the use of the analogue.A power-series expansion is assumed for the non-linear characteristics of a tunnel diode, and the steadystate oscillation for a simple series-oscillator configuration with a non-negligible series resistance has been analysed by using the perturbation method of Kryloff and Bogoliuoboff. The tendency for non-linear oscillators to oscillate at a frequency above that predicted by the linear theory has been theoretically explained. The well-known oscillation hysteresis in such oscillators has also been discussed, and some of the theoretical results have been verified experimentally.

DOI:10.1049/piee.1963.0007

出版商:IEE    

年代:1963

数据来源: IET

摘要:

The problems of measuring transmission (i.e. gain and phase shift) at frequencies in the range 10−3−102c/s are briefly reviewed, and an equipment which overcomes most of them is described. The oscillator is novel, and has the important property that its amplitude is immediately self-stabilizing. The phase-shifter is also novel, and is of a resistive-potentiometer type having a set of ganged brushes. It gives an adjustable phase shift with very little change in amplitude. The conditions in which a non-sinusoidal waveform lacks a specified set of harmonics are discussed in an Appendix.

DOI:10.1049/piee.1963.0008

出版商:IEE    

年代:1963

数据来源: IET

摘要:

A common method of measuring characteristics of waveguides for long-distance communication involves the use of millimicrosecond pulses in a multiple-reflection test; test waveguides of a few hundred feet in length are employed. The enormous bandwidth, typically 40 Gc/s, which must be covered constitutes a major difficulty because several thousand measurements are necessary if the guide is to be adequately tested. A programme of measurements would then take months to complete, so that not only daily, but seasonal, weather effects would have to be considered. In order to make complete tests possible, novel equipment capable of rapid graphical presentation has been developed.The construction of a swept-frequency receiver employing a backward-wave oscillator (b.w.o.) as both signal source and local oscillator is described. A square wave applied to the frequency-controlling electrode switches the b.w.o. into two states: signal frequency (100 ns duration) and local oscillator (1 ms duration). A graphical presentation is obtained by sweeping the b.w.o. slowly through its tuning range. Errors resulting from the inherent b.w.o. power variation with frequency are avoided by comparing the magnitude of the pulses, derived from multiple reflection in the guide under test, on a ratio basis. Pulses to be compared are gated into separate channels where they are converted into a suitable form for operating a commercial ratio meter. The output of the latter feeds a pen recorder. Facilities for providing frequency markers are incorporated. The apparatus provides a complete record of the frequency characteristics of the guide in about half-an-hour.

DOI:10.1049/piee.1963.0009

出版商:IEE    

年代:1963

数据来源: IET

摘要:

Lane and Evans have reported measurements on transverse-film bolometers and have analysed these to obtain values for the inductance of film. Their inductances are about 15% below those predicted by normal waveguide theory. It is shown in this paper that the discrepancy can be attributed to the presence of a capacitance associated with the glass strip on which the film is mounted. A further complication is the relative insensitiveness of the measured quantities to the film inductance. The results calculated using a modified circuit to allow for the capacitance give excellent agreement between the experimental and theoretical inductances, and it is concluded that there is no reason to doubt the validity of the usual inductance formula.

DOI:10.1049/piee.1963.0010

出版商:IEE    

年代:1963

数据来源: IET