Method and apparatus for tuning a radio receiver with a radio transmitter
First Claim
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1. A wireless device, comprising:
- a crystal oscillator generating a reference frequency;
a radio circuit configured to operate according to the reference frequency and receive a wireless data signal from another wireless device;
a signal quality calculator configured to produce signal quality measurements according to a signal quality of the data signal, the signal quality correlated with an accuracy of the reference frequency but not indicative of a direction in which the reference frequency is offset from an operating frequency used to transmit the data signal;
wherein the signal quality measurements are independent of direct frequency measurements; and
a crystal oscillator trim circuit configured to trim the reference frequency of the crystal oscillator in response to the signal quality measurements, wherein the trim circuit is further configured to store a previous trimming direction for the reference frequency, and to selectively reverse the previous trimming direction when the signal quality measurements indicate that the previous trimming direction has worsened the signal quality.
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Abstract
Wireless devices transmit and receive radio signals based upon reference frequencies that are generated by reference frequency circuits. If the reference frequency in the transmitter is different from the reference frequency in the receiver, the radio signals may not be received properly or may not be capable of being received at all. A measurement circuit measures the amount of error or signal corruption in radio signals due to the reference frequency offset. A trimming circuit then tunes the reference frequency in the transmitter or receiver to reduce the reference frequency offset.
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Citations
20 Claims
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1. A wireless device, comprising:
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a crystal oscillator generating a reference frequency; a radio circuit configured to operate according to the reference frequency and receive a wireless data signal from another wireless device; a signal quality calculator configured to produce signal quality measurements according to a signal quality of the data signal, the signal quality correlated with an accuracy of the reference frequency but not indicative of a direction in which the reference frequency is offset from an operating frequency used to transmit the data signal; wherein the signal quality measurements are independent of direct frequency measurements; and a crystal oscillator trim circuit configured to trim the reference frequency of the crystal oscillator in response to the signal quality measurements, wherein the trim circuit is further configured to store a previous trimming direction for the reference frequency, and to selectively reverse the previous trimming direction when the signal quality measurements indicate that the previous trimming direction has worsened the signal quality. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of tuning a radio, comprising:
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determining an amount of corruption due to crystal oscillator reference frequency offset between transmitting and receiving devices by measuring a respective Bit Error Rate (BER) of each of a plurality of data transmissions between the transmitting and the receiving devices; adjusting the reference frequency in a first direction and storing the first direction as a saved direction when there is no previously saved BER measurement; and adjusting the reference frequency in a direction opposite that of the saved direction when there is the previously saved BER measurement and when the respective BER of a current one of the data transmissions is worse than the previously saved BER measurement. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A radio system, comprising:
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a radio receiver configured to receive and process a radio transmission according to a crystal oscillator frequency; a trimming circuit configured to selectively vary the crystal oscillator frequency; and
a processing element configured to;calculate a signal integrity for the received radio transmission; infer a frequency offset between the crystal oscillator frequency and a selected frequency corresponding to the calculated signal integrity, wherein the inference is independent of a direct frequency measurement; and adjust the trimming circuit in response to the inferred frequency offset corresponding to the calculated signal integrity, wherein a first adjustment is in a direction independent of a difference between the crystal oscillator frequency and a desired frequency, and wherein a subsequent adjustment is in a direction according to a difference between the signal integrity prior to the first adjustment and the signal integrity after the first adjustment. - View Dependent Claims (19, 20)
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Specification