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US 7,734,274 B2Granted
Narrow-band detections of a received signal
AssigneePreco Electronics, Inc.
InventorDouglas Todd Hayden
Life of this patent
Estimating the term…
Abstract
The frequency of an RF signal to be transmitted is modulated at the transmitting unit, and the modulation information is used by the receiving unit to filter out any unwanted noise. The modulation information may be used to retrieve associated filter coefficients that are used by the receiver to filter out the noise. Accordingly, for each transmit frequency, a multitude of filter coefficients stored in a memory are applied by the receiver to filter out the noise. The filtering operation may be performed after the received signal is downconverted from an RF to an audio signal.
Claims28
An apparatus comprising:
- a sampler configured to downconvert a received RF signal to an analog audio signal;
- an analog-to-digital converter configured to convert the analog audio signal to a digital audio signal;
- a memory having stored therein a plurality of filter coefficients each associated with a different RF signal transmission frequency;
- and
- a filter configured to filter out noise components present in the digital audio signal using one or more of the filter coefficients stored in the memory, wherein said filter coefficients are selected in accordance with a frequency shifting algorithm defining an amount of shift in frequency of an associated transmitted RF signal.
2 more elements
A method of filtering comprising:
- downconverting a received RF signal to an analog audio signal;
- converting the analog audio signal to a digital audio signal;
- varying a frequency characteristics of a filter in accordance with a plurality of stored filter coefficients to filter out noise components present in the converted digital audio signal;
- and
- varying said filter coefficients in response to a frequency shifting algorithm.
2 more elements
An apparatus comprising:
- a sampler configured to downconvert a received RF signal to an analog audio signal;
- a memory having stored therein a plurality of digitization rates each associated with a different RF signal transmission frequency;
- an analog-to-digital converter configured to convert the analog audio signal to a digital audio signal using one or more of the plurality of digitization rates stored in the memory;
- and
- a filter configured to filter out noise components present in the digitized audio signal, wherein said digitization rates are selected in accordance with a frequency shifting algorithm defining an amount of shift in frequency of an associated transmitted RF signal.
2 more elements
A method of filtering comprising:
- downconverting a received RF signal to an analog audio signal;
- varying digitization rates of said analog audio signal in accordance with one of a plurality of stored digitization rates in response to a frequency shifting algorithm;
- and
- filtering out noise components present in the digitized audio signal.
1 more element
An apparatus comprising:
- a sampler configured to downconvert a received RF signal to an analog audio signal;
- a plurality of filters, each filter characterized by a different center frequency;
- and
- a decoder responsive to a control signal to select one of the plurality of filters to filter out noise components present in the analog audio signal;
- wherein said control signal is varied in accordance with a frequency shifting algorithm defining an amount of shift in frequency of an associated transmitted RF signal.
2 more elements
An apparatus comprising:
- a sampler configured to downconvert a received RF signal to an analog audio signal;
- a plurality of filters, each filter characterized by a different center frequency;
- and
- a decoder responsive to a control signal to select one of the plurality of filters to filter out noise components present in the analog audio signal;
- wherein said control signal is varied in accordance with information obtained by periodically turning off a transmitter transmitting an associated RF signal, the variation in the control signal being representative of an amount of shift in frequency of the associated transmitted RF signal.
2 more elements
A method comprising:
- downconverting a received RF signal to an analog audio signal;
- selecting one of the plurality of filters in accordance with a frequency shifting algorithm defining an amount of shift in frequency of an associated transmitted RF signal, each of said filters being characterized by a different center frequency;
- and
- filtering out noise components present in the analog audio signal using the selected filter.
1 more element
A method comprising:
- downconverting a received RF signal to an analog audio signal;
- selecting one of the plurality of filters in accordance with information obtained by periodically turning off a transmitter transmitting an associated RF signal, the information being representative of an amount of shift in frequency of the associated transmitted RF signal;
- and
- filtering out noise components present in the analog audio signal using the selected filter.
1 more element
Dependencies are inferred from the claim text.