Method and system for presence detection

1. A system for presence control within a detection volume delimited by an inner radius and an outer radius from a center of said detection volume, said system comprising:

a microwave transmitter for transmitting microwaves from said center of said detection volume;

a microwave receiver for detecting microwave radiation reflected towards said center of said detection volume;

a first pulse generator generating a sequence of first pulses triggering the microwave transmitter, each first pulse having a length establishing a transmit interval of said microwave transmitter;

a second pulse generator receiving the sequence of first pulses and triggered by a trailing edge of each first pulse to generate a sequence of second pulses, each of the second pulses immediately following and non-concurrent with the respective preceding first pulse; and

a third pulse generator receiving the sequence of second pulses and triggered by a trailing edge of each second pulse to generate a sequence of third pulses triggering the microwave receiver and having a length to establish a receive interval thereof, each third pulse immediately following and non-concurrent with the respective preceding second pulse, whereby each second pulse has a length defining a time period pause between each first pulse and each respective following third pulse, and wherein the second pulse length added to the third pulse length is equal to a transmitter off-time separating the first pulses.

2. A method for presence detection within a detection volume delimited by an inner radius and an outer radius from a center of the detection volume, the method comprising:

providing a microwave transmitter for transmitting microwaves from the center of the detection volume;

providing a microwave receiver for detecting microwave radiation reflected towards the center of the detection volume;

operating a first pulse generator to generate a sequence of first pulses triggering the microwave transmitter to transmit, each first pulse having a length establishing a transmit interval of said microwave transmitter;

operating a second pulse generator to receive the sequence of first pulses and generate a sequence of second pulses when triggered by a trailing edge of each first pulse, each of the second pulses immediately following and non-concurrent with the respective preceding first pulse;

operating a third pulse generator to receive the sequence of second pulses and generate a sequence of third pulses when triggered by a trailing edge of each second pulse, each third pulse triggering the microwave receiver to receive and having a length to establish a receive interval thereof, each third pulse immediately following and non-concurrent with the respective preceding second pulse, whereby each second pulse has a length defining a time period pause between each first pulse and each respective following third pulse, and wherein the second pulse length added to the third pulse length is equal to a transmitter off-time separating the first pulses; and

determining the presence of a moving object within the detection volume based on properties of the microwave radiation being received by the microwave receiver.

3. The method according to claim 2 wherein the step of determining the presence of a moving object within the detection volume comprises using a Doppler motion sensor process.

4. The method according to claim 3 wherein it comprises:

controlling the length of said first pulses by means of a first pulse length detector; and

controlling the length of said third pulses by means of a third pulse length detector.

5. The method according to claim 4 wherein it comprises:

providing a measurement by said first pulse length detector which is fed to a first comparator which is controlled with a first target pulse length; and

providing a measurement by said third pulse length detector which is fed to a third comparator which is controlled with a third target pulse length.