EP0065339A1
Expired / Lapsed
EP
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Radiometer
Assignee: Philips Electronics UK Ltd
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Filing: 1982-05-11
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Granted: —
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Expires: 2002-05-11
Abstract
Abstract In a total power radiometer an amplitude modulated noise signal is injected into the radiation signal before it is mixed down to an IF frequency in a mixer (12). After the IF signal has been amplified and detected it is applied to an input of a d.c. amplifier (20) to which stabilization of channel gain and d.c. drift are applied. The gain of the amplifier (20) is stabilized by modifying the amplitude of its feedback signal using a gain control signal which is derived from the 10 kHz modulated noise signal present in the output of the amplifier (20). In the case of stabilizing the d.c. drift, the input signal to the d.c. amplifier (20) from the IF detector (18) is interrupted whilst the d.c. offset error is sampled by a capacitor which is connected to a comparator, the charge on the comparator, is compared with a reference voltage and the output is applied to an input of the amplifier (20) to correct the drift.
Inventors
- 👤 Leslie Henry Guildford
- 👤 Stephen James Nightingale
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 06:43
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/3005; G; G01; G01K; G01K11/00; G01K11/006; H03F; H03F1/00; H03F1/30; H03F1/303; H03F1/304
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
128 words
A total power radiometer comprising an antenna for receiving a radiation signal, a source of an amplitude modulated noise signal having a frequency greater than the radiation signal to be detected, means for injecting the noise signal into the radiation signal, an IF stage for producing an IF signal, an IF detector and processing circuitry coupled to the IF detector and including means for producing a gain stabilised output signal, wherein the.processing circuitry further comprises means for separating the amplitude modulated noise signal from the detected radiation signal, comparing means for comparing the separated noise signal with a predetermined reference signal and producing a gain control signal and means for adjusting the sensitivity of the gain stabilised output signal producing means in response to said gain control signal.
Claim 2
Dependent Claim
128 words
A total power radiometer comprising an antenna for receiving a radiation signal, a source of an amplitude modulated noise signal having a frequency greater than the radiation signal to be detected, means for injecting the noise signal into the radiation signal, an IF stage for producing an IF signal, an IF detector and processing circuitry coupled to the IF detector and including means for producing a gain stabilised output signal, wherein the.processing circuitry further comprises means for separating the amplitude modulated noise signal from the detected radiation signal, comparing means for comparing the separated noise signal with a predetermined reference signal and producing a gain control signal and means for adjusting the sensitivity of the gain stabilised output signal producing means in response to said gain control signal.
Claim 3
Dependent Claim
42 words
A radiometer as claimed in Claim 1, wherein the means for producing a gain stabilised output signal comprises a d.c. amplifier having a feedback path and the means for adjusting the sensitivity of the d.c. amplifier is coupled to the feedback path.
Claim 4
Dependent Claim
48 words
A radiometer as claimed in Claim 2, wherein the means for adjusting the sensitivity of the d.c. amplifier comprises a field effect transistor having a gate electrode coupled to an output of the comparing means and a source-drain path connected to the feedback path of the d.c. amplifier.
Claim 5
Dependent Claim
77 words
A radiometer as claimed in Claim 2 or 3, further comprising a first switching means connected between the IF detector and an input of the d.c. amplifier, a d.c. drift correcting circuit coupled between an output of the d.c. amplifier and the input thereto, the drift correcting circuit including a second switching means, and logic means for controlling the first and second switching means such that when one is closed the other is open and vice versa.
Claim 6
Dependent Claim
69 words
A radiometer as claimed in Claim 4, wherein the drift correcting circuit includes a capacitor for storing a d.c. offset error sampled in response to the second switching means being closed and the first switching means being opened and a comparator for comparing the voltage on the capacitor with a reference voltage and producing a d.c. drift correcting signal which is applied to the input of the d.c. amplifier.
Claim 7
Dependent Claim
25 words
A radiometer as claimed in Claim 5, wherein the capacitor has a long time constant compared with the sampling time of the second switching means.
Claim 8
Dependent Claim
54 words
A radiometer as claimed in Claim 1, wherein the processing circuitry is of digital type and includes an analogue to digital converter (ADC) for converting.the detected IF signal to digital form, a programmed microcomputer coupled to the ADC and a digital to analogue converter for producing an analogue gain stabilized signal on its output.
Claim 9
Dependent Claim
21 words
A radiometer as claimed in any one of Claims 1 to 7, in which the modulated noise signal is injected continuously.
Claim 10
Dependent Claim
21 words
A radiometer as claimed in any one of Claims 1 to 7, in which the modulated noise signal is injected intermittently.
References Cited (Backward Citations)
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