| 摘要 |
Adaptive self-calibration of a radio tuner quickly compensates for temperature changes and other errors. The tuner includes a modified PLL with a reference signal generator to provide a reference signal with a desired frequency. A phase detector measures the phase difference between the reference signal and a feedback signal. An integrator integrates the phase detector's output signal over time and a summer sums the integrator's output signal along with an analog steering signal. The summer provides the summed output signal to an ICO that provides an output signal proportionate in frequency to the summed output signal. An amplifier uses the ICO's output signal to amplify an electromagnetic signal detected by an antenna. The amplifier provides its amplified signal to a demodulator and other circuitry of the tuner. The tuner additionally includes a divider connected between the ICO and the phase detector, to provide the feedback signal by dividing ICO's output signal by a predetermined number. The tuner also includes certain steering circuitry. During the initial operation of the tuner and in response to temperature and reference signal changes, a logic unit consults a memory device to select an analog pre-steering signal appropriate to the current reference signal and the current temperature. The logic unit provides this value to the summer for summing with the integrated signal. During ongoing operation of the tuner, the logic unit helps self-calibrate the tuner by sampling the integrator's output, and appropriately selecting a corrected steering signal to minimize the integrator's signal.
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