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 for filtering the rectified signal to generate a filtered signal, the synchronous rectifier comprising a non-inverting amplifier and an inverting amplifier both receiving an amplified signal, the synchronous rectifier further comprising a first analog switch coupled to an output of the non-inverting amplifier and a second analog switch coupled to an output of the inverting amplifier, the first and second analog switches electrically coupled together 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 first and second analog switches conductive and non-conductive on a complementary basis such the outputs of the analog switches are mixed together to form the rectified signal, the controller further operable to receive the filtered signal and to determine that the space is occupied if a magnitude of the filtered signal exceeds a threshold.
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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
19 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 for filtering the rectified signal to generate a filtered signal, the synchronous rectifier comprising a non-inverting amplifier and an inverting amplifier both receiving an amplified signal, the synchronous rectifier further comprising a first analog switch coupled to an output of the non-inverting amplifier and a second analog switch coupled to an output of the inverting amplifier, the first and second analog switches electrically coupled together 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 first and second analog switches conductive and non-conductive on a complementary basis such the outputs of the analog switches are mixed together to form the rectified signal, the controller further operable to receive the filtered signal and to determine that the space is occupied if a magnitude of the filtered signal exceeds a threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. 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 the rectified signal from the input signal, and a filter for filtering the rectified signal to generate a filtered signal; a controller operable to drive the ultrasonic transmitting circuit with at least one drive signal to control an ultrasonic transmission frequency of the transmitted ultrasonic waves, the controller further operable to receive the filtered signal and to determine that the space is occupied if a magnitude of the filtered signal rises above an upper threshold or falls below a lower threshold; and a low phase-noise oscillator circuit coupled to the controller for setting an internal operating frequency of the controller, the ultrasonic transmission frequency of the transmitted ultrasonic waves being approximately equal to the internal operating frequency of the controller; wherein the synchronous rectifier also receives the drive signal from the controller, such that the filtered signal rises above the upper threshold or falls below the lower threshold when a received ultrasonic frequency of the received ultrasonic waves is different than the ultrasonic transmission frequency of the transmitted ultrasonic waves. - View Dependent Claims (12, 13, 14)
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15. 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 a non-inverting amplifier, an inverting amplifier, a first analog switch coupled to an output of the non-inverting amplifier, and a second analog switch coupled to an output of the inverting amplifier, the first and second analog switches electrically coupled together such that outputs of the analog switches are mixed together to form the rectified signal; and a filter for filtering the rectified signal to generate a filtered signal; wherein the filtered signal indicates the presence of the occupant in the space if a magnitude of the filtered signal exceeds a threshold. - View Dependent Claims (16, 17, 18, 19)
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Specification