Watching apparatus by means of a radar probe

• US 5,844,519 A
• Filed: 12/06/1996
• Issued: 12/01/1998
• Est. Priority Date: 12/06/1995
• Status: Expired due to Fees

• Current Assignee: Geberit Technik AG
• Original Assignee: Geberit Technik AG
• Inventors: Mauerhofer, Alex, Heierli, Jakob
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/761,304
• Time in Patent Office: 725 Days
• Field of Search: 342/27, 342/28, 342/61, 342/84, 342/85, 342/103, 342/114, 342/174, 342/203
• US Class Current: 342/28
• CPC Class Codes: G01S 13/04 Systems determining presence of a target based on relative movement of target G01S13/56
• CPC Class Codes: G01S 13/40 wherein the frequency of transmitted signal is adjusted to give a predetermined phase relationship

Abstract

The watching apparatus is provided with a radar probe, and is made such as to detect the presence of human beings. The radar probe includes a command unit and a branching element, inserted between an oscillator circuit and a transmitter stage, as well as a superposing circuit (5), in which a signal, derived from the radar transmitter, is superposed with an echo signal received by a receiver stage. The radar probe is made such as to work as an interference radar, and a delay circuit is inserted into the transmitter-receiver path between the branching element and the superposing circuit in order to increase the travelling time of the radar signal with respect to the branched off signal.

Claims

1. A watching device for contact-less control of a plumbing unit having a radar probe, the device comprising:

an actuating circuit connected to the plumbing unit;

an oscillator circuit generating an oscillating signal;

a branching element receiving said oscillating signal from said oscillating circuit, said branching element dividing said oscillating signal into a transmitting signal and a reference signal;

a radar transmitter receiving said transmitting signal from said branching element and emitting a radar wave;

a radar receiver receiving said radar wave and generating a receiver signal;

a superposing circuit combing said reference signal and said receiver signal to form an interference signal;

a delay circuit positioned in a path of said radar transmitter and receiver, and said delay circuit being positioned between said branching element and said superposing circuit for increasing a travel time along said path of said radar transmitter and receiver with respect to said reference signal;

a control unit for receiving said interference signal, and controlling said oscillator circuit to operate the radar probe as an interference radar to determine if an object is within an area of surveillance and said control unit generating an actuating signal applied to said actuation circuit.

2. Device according to claim 1, wherein:

said delay circuit has a delay time between 2 and 40 ns.

3. A device in accordance with claim 2, wherein:

a demodulator circuit is positioned between said superposing circuit and said control unit.

4. Device according to claim 3, wherein:

said control unit comprises a rectifier, connected at its input to an output of said demodulator circuit, said rectifier is connected via a comparator to a microprocessor which is connected to and controls the oscillator circuit.

5. Device according to claim 4, wherein:

said demodulator circuit comprises a demodulator and a following highpass filter;

said control unit comprises a low frequency oscillator, an output of said low frequency oscillator is connected to an input of the rectifier and to an input of the radar transmitter to form an auxiliary modulator.

6. Device according to claim 4 wherein:

said control unit includes a subtracting unit, inserted between the rectifier and the comparator and that a second input of the subtracting unit is connected via a digital/analog converter to the microprocessor, said subtracting unit suppressing background signals.

7. Device according to claim 6, wherein:

an analog/digital converter is inserted between the output of the rectifier and another input of the microprocessor for storing background signals.

8. Device according to claim 5, wherein:

said control unit includes, a subtracting unit, inserted between the rectifier and the comparator and that a second input of the subtracting unit is connected via a digital/analog converter to the microprocessor, said subtracting unit suppressing background signals.

9. A device in accordance with claim 2, wherein:

said radar receiver includes a receiver antenna;

said delay circuit is positioned in said radar receiver between said receiver antenna and said suppressing circuit.

10. Device according to claim 1, wherein:

said oscillator circuit comprises a frequency synthesizer, which is tunable to a variable frequency (fm) by the control unit, a voltage controlled oscillator is connected to an output of said frequency synthesizer.

11. Device according to claim 10, wherein:

said frequency synthesizer is made such as to work with one of a plurality of official frequencies, with a band width of 120 MHz and a step width of 50·

n kHz, where n is an integer between 4 and 20.

12. A device in accordance with claim 1, wherein:

a demodulator circuit is positioned between said superposing circuit and said control unit.

13. A device in accordance with claim 1, wherein:

said delay circuit increases an overall travel time of said transmitting and receiving signal along said path.