Ultrasonic receiving circuit
First Claim
1. An ultrasonic occupancy sensor for detecting presence or absence of an occupant in a space, the occupancy sensor comprising:
- an ultrasonic transmitting circuit comprising an ultrasonic transmitting element for transmitting ultrasonic waves;
an ultrasonic receiving circuit comprising an ultrasonic receiving element for receiving ultrasonic waves and generating an ultrasonic input signal, a synchronous rectifier for generating a rectified signal from the input signal, and a filter circuit for filtering the rectified signal to generate a filtered signal, the synchronous rectifier comprising at least one amplifier circuit and at least one analog switch coupled to an output of the amplifier circuit for forming the rectified signal; and
a controller operable to drive the ultrasonic transmitting circuit with a drive signal to control an ultrasonic transmission frequency of the transmitted ultrasonic waves, the controller operable to render the analog switch conductive and non-conductive in phase with the drive signal to form the rectified signal, the controller further operable to receive the filtered signal and to determine that the space is occupied in response to the filtered signal.
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Accused Products
Abstract
An ultrasonic occupancy sensor for detecting presence or absence of an occupant in a space includes an ultrasonic receiving circuit having a synchronous rectifier that allows the circuit to detect small-magnitude ultrasonic waves having a Doppler shift. The sensor comprises an ultrasonic transmitter for transmitting ultrasonic waves at an ultrasonic operating frequency, and a controller that drives the transmitting circuit with complementary drive signals to control the ultrasonic operating frequency. The synchronous rectifier receives the drive signals from the controller and rectifies an amplified input signal to generate a rectified signal, which is filtered by a filter to generate a filtered signal. The controller receives the filtered signal and determines that the space is occupied if the magnitude of the filtered signal exceeds a threshold. The ultrasonic occupancy sensor may also include a low phase-noise oscillator circuit coupled to the controller for setting an internal operating frequency of the controller.
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Citations
28 Claims
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1. An ultrasonic occupancy sensor for detecting presence or absence of an occupant in a space, the occupancy sensor comprising:
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an ultrasonic transmitting circuit comprising an ultrasonic transmitting element for transmitting ultrasonic waves; an ultrasonic receiving circuit comprising an ultrasonic receiving element for receiving ultrasonic waves and generating an ultrasonic input signal, a synchronous rectifier for generating a rectified signal from the input signal, and a filter circuit for filtering the rectified signal to generate a filtered signal, the synchronous rectifier comprising at least one amplifier circuit and at least one analog switch coupled to an output of the amplifier circuit for forming the rectified signal; and a controller operable to drive the ultrasonic transmitting circuit with a drive signal to control an ultrasonic transmission frequency of the transmitted ultrasonic waves, the controller operable to render the analog switch conductive and non-conductive in phase with the drive signal to form the rectified signal, the controller further operable to receive the filtered signal and to determine that the space is occupied in response to the filtered signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An ultrasonic receiving circuit for detecting a presence or absence of an occupant in a space comprises:
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an ultrasonic receiving element for generating an ultrasonic input signal; a synchronous rectifier for generating a rectified signal from the input signal, the synchronous rectifier comprising at least one amplifier circuit and at least one analog switch coupled to an output of the amplifier circuit for forming the rectified signal; and a filter circuit for filtering the rectified signal to generate a filtered signal; wherein the analog switch is rendered conductive and non-conductive to form the rectified signal such that the filtered signal indicates the presence of the occupant in the space. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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Specification