GB2124392A

GB2124392A - Apparatus for monitoring power

Info

Publication number: GB2124392A
Application number: GB08221382A
Authority: GB
Inventors: John Alexander Duff; Dr John Arthur Broadhead
Original assignee: English Electric Valve Co Ltd
Current assignee: Teledyne UK Ltd
Priority date: 1982-07-23
Filing date: 1982-07-23
Publication date: 1984-02-15
Also published as: GB2124392B

Abstract

A power level detector device 9 acts to protect receiver circuits 8 from too high a level of incident power. When power at the device 9 is above a certain threshold level the gas contained by the device 9 generates an emission spectrum of electro- magnetic energy. This energy is detected by a photodetector 10 which produces an electrical signal to control the power of a transmitter 1 and hence the power transmitted to the receiver circuits 8. <IMAGE>

Description

SPECIFICATION Apparatus for monitoring power This invention relates to apparatus for monitoring power and more particularly for monitoring power levels to prevent them reaching a critical value of the critical value being maintained. By "monitoring" it is meant that an indication is given when a particular level of power exists. Such indication may be used purely to provide a warning of the situation or, of course, to initiate some control action.

This invention provides apparatus for monitoring power comprising a fluid of such nature that a characteristic spectrum of electromagnetic energy results when power of a certain magnitude is incident thereupon, means for subjecting said fluid to power to be monitored and means for detecting said spectrum.

Most fluids have certain states of their constituent atoms or molecules such that when energy is incident spectra may result. These could be, for example, emission, absorption or fluorescent spectra and may be discrete or continuous. By using certain characteristics of the spectra an indication of power levels may be given. A spectrum may be produced by electrons changing state and emitting or absorbing photons, or also, in the case of molecules, by interactions of rotational and vibrational states with incident energy.

Preferably the said characteristic spectrum that results is an emission spectrum. An emission spectrum is produced by electrons returning to lower energy states, after having been excited by incident energy, and in the process emitting photons having energies related to the spacing between the different levels. The production of an emission spectrum depends on a certain threshold power level being reached. Below this threshold of incident power no spectrum will result. Factors which affect the threshold level are the type of fluid, its pressure and its configuration in relation to incoming radiation. When it reaches the threshold value either, in the case of increasing power, a spectrum is produced, or, when power is decreasing, the emission spectrum ceases.An indication, for example a visual display for an operator, can thus be given when the magnitude of power incident on the fluid reaches the threshold value.

It is preferred that there is means for altering the power depending on the spectrum detected.

Thus when the power level is at a critical value as evinced by the threshold being reached the power could be reduced, switched off or increased.

It is also preferred that the means for detecting the spectrum includes a photodetector which produces an electrical signal representative of the electromagnetic energy detected. This can then be used as a control signal to alter the magnitude of incident power.

Preferably the fluid is contained within a plurality of tubes. These may be distributed throughout the field of incoming radiation and, for example, monitor standing waves in it. The plurality of tubes may contain different fluids or fluids at different pressures. Then, since the production of spectra in these tubes will occur at different threshold power values, the apparatus could be used as a power level monitor giving indications of more than one level.

According to a feature of this invention a receiver includes apparatus as described above.

Preferably said apparatus is arranged to control the level of power passing through the receiver circuits, preferably to the extent that if said level is too great said power is cut off.

According to another feature of this invention a transmitter includes apparatus as described above, preferably arranged to control the output power level of said transmitter in dependence upon the spectrum detected. Said last mentioned transmitter may be one in a system, such as a radar system, in which a received signal depends on the output of the transmitter.

The invention will be further described by way of example with reference to the accompanying drawing which is a block diagram of one radar apparatus in accordance with the present invention.

A transmitter 1 is controlled by a control circuit 2 and generates R.F. signals. These signals pass along a channel 3 to a duplexer 4 which routes them to an antenna 6.

The transmitted signals after being radiated from the antenna 6 are reflected by a target (not shown) and are received by the antenna 6.

The output of the antenna 6 is passed via the duplexer 4 through channel 7 (in practice a waveguide) to receiving circuits 8.

Within channel 7 is a power level detection device 9 which comprises a gas filled tube (not separately shown) exposed to energy passing through said channel 7 and, positioned to view said tube, a photodetector 10. The type of gas filling employed, its pressure and the positioning of the tube with respect to incident RF power are chosen such that, at a certain magnitude of incident power, excitation of electrons of the cotstituent molecules of the gas will occur, resulting in an emission spectrum being produced. This power level is chosen so that it is above normal operational power levels but below a critical value determined by power handling capabilities of other elements which deal with the received signal. If the magnitude of the incident power is at an acceptable level the device 9 does not come into operation, no emission spectra being produced.

However if the received signal is such that its power is above an acceptable level, the gas contained in the tube of the device 9 produces an emission spectrum. This is detected by photodetector 10 which converts the electromagnetic energy generated into an electrical signal and transmits it along a line 11 to a monitoring circuit 12. This produces a visual warning and transmits a signal to the control circuit 2 which acts to reduce the power of the transmitter 1.

When the power of the transmitter 1 is reduced, so also is the resulting power within receiver channel 7. When the last mentioned power is sufficiently reduced, the emission spectrum produced by the tube in device 9 ceases leaving the control of the transmitter power set at its new safe level.

As shown, also within receiver channel 7 is additional receiver protection means 1 3 as known perse e.g. a T.R. cell.

Whilst in the example described above photodetector 10 is incorporated with the gas filled tube as part of device 9, the photodetector may be remote with a light conductive path extending therebetween.

Claims

1. Apparatus for monitoring power comprising a fluid of such nature that a characteristic spectrum of electromagnetic energy results when power of a certain magnitude is incident thereupon, means for subjecting said fluid to power to be monitored and means for detecting said spectrum.

2. Apparatus as claimed in claim 1 and wherein the spectrum is an emission spectrum.

3. Apparatus as claimed in claim 1 or 2 and including means for altering the power depending on the spectrum detected.

4. Apparatus as claimed in any of the above claims and wherein the means for detecting the spectrum includes a photodetector which produces an electrical signal representative of the electromagnetic energy detected.

5. Apparatus as claimed in any preceding claim and wherein the fluid is contained within a plurality of tubes.

6. Apparatus as claimed in claim 5 and wherein the tubes of the said plurality are distributed throughout the field of incident power.

7. Apparatus as claimed in claim 5 or 6 and wherein the said plurality contains different fluids.

8. Apparatus as claimed in claim 5, 6 or 7 and wherein the said plurality contains fluid at different pressures.

9. A receiver including apparatus as claimed in any preceding claim.

10. A receiver as claimed in claim 9 and wherein said apparatus is arranged to control the lever of power passing through the receiver circuits.

1 A receiver as claimed in claim 10 and wherein if said level is too great said power is cut off.

12. A transmitter including apparatus as claimed in any preceding claim.

13. A transmitter as claimed in claim 12 and wherein said apparatus is arranged to control the output power of said transmitter in dependence upon the spectrum detected.

14. Apparatus as claimed in any preceding claim and wherein the power is at ratio frequency.

1 5. Apparatus substantially as illustrated in and described with reference to the accompanying drawing.