Microwave sensor for detecting a discharge occurring in an electrical apparatus

• US 5,726,576 A
• Filed: 04/10/1996
• Issued: 03/10/1998
• Est. Priority Date: 04/10/1996
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Otani, Hiroshi, Miyata, Tomoyuki
• Primary Examiner(s): Nguyen, Vinh P.
• Assistant Examiner(s): Brown, Glenn W.
• Application Number:
  US08/630,817
• Time in Patent Office: 699 Days
• Field of Search: 324/520, 324/521, 324/536, 324/541, 324/544, 324/545, 324/546, 324/547, 324/551
• US Class Current: 324/536
• CPC Class Codes: G01R 29/0871 Complete apparatus or systems; circuits, e.g. receivers or amplifiers G01R29/0878, G01R29/0892 take precedence; dosimeters, warning devices G01R29/0857
• CPC Class Codes: G01R 29/0892 Details related to signal analysis or treatment; presenting results, e.g. displays; measuring specific signal features other than field strength, e.g. polarisation, field modes, phase, envelope, maximum value
• CPC Class Codes: G01R 31/12 Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing G01R31/08, G01R31/327 and G01R31/72 take precedence; measuring in plasmas G01R19/0061; measuring dielectric constants G01R27/2617; ESD, EMC or EMP testing of circuits G01R31/002

Abstract

A microwave sensor includes a case 1 of an object apparatus in which a discharge may occur; the object apparatus 2; an antenna 3 which is attached to the object apparatus case 1 and receives a microwave signal generated by a discharge; a signal processing unit 4 which is connected to the antenna 3, amplifies and detects the microwave signal, and amplifies the detected video signal; and an output terminal 13 through which the video signal is output.

Claims

1. A microwave sensor comprising:

an antenna unit which is to be placed in the vicinity of an electric apparatus and which receives a microwave signal generated by a discharge occurring in the electric apparatus;

a first band-pass filter that allows a predetermined frequency of the microwave signal received by said antenna unit to pass through said filter;

amplifying means for amplifying the microwave signal output from said first band-pass filter;

a second band-pass filter that removes noise produced by said amplifying means;

converting means for converting the microwave signal output from said second band-pass filter into a video signal; and

video amplifying means for amplifying the video signal output from said converting means.

2. A microwave sensor according to claim 1, further comprising, in a stage preceding said amplifying means, a limiter which, when the electromagnetic wave level of the microwave signal is greater than a predetermined value, limits the electromagnetic wave level of the microwave signal.

3. A microwave sensor according to claim 1, wherein said converting means comprises logarithmic amplifying and converting means for amplifying the intermediate-frequency signal output from said second band-pass filter, and for converting the signal into a video signal.

4. A microwave sensor according to claim 1, further comprising in a stage preceding said amplifying means:

coupling means for extracting a part of the microwave signal;

comparing means for comparing an electromagnetic wave level of the microwave signal extracted by said coupling means with a predetermined value;

attenuating means for attenuating the microwave signal; and

switching means for switching the microwave signal to said attenuating means, and, when the electromagnetic wave level of the microwave signal supplied to said comparing means is not lower than the predetermined value, said switching means is automatically switched to said attenuating means.

5. A microwave sensor according to claim 1, further comprising, in a stage preceding said amplifying means, interrupting means for, when the electromagnetic wave level of the microwave signal is greater than a predetermined value, interrupting the microwave signal, said interrupting means comprising a switch and a terminator.