Method for lowpass filter calibration in a satellite receiver
First Claim
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1. A DBS receiver front end comprising:
- a tuner chip having a lowpass filter with a configurable cutoff frequency, wherein the tuner is configured to adjust the cutoff frequency based on a clock signal frequency of a clock signal, wherein the tuner chip is further configured to receive a receive signal, to convert the receive signal to a product signal, and to filter the product signal with the lowpass filter to provide a baseband signal; and
a demodulator/decoder chip coupled to receive the baseband signal and configured to convert the baseband signal to a decoded signal, wherein the demodulator/decoder chip is further configured to provide said clock signal,wherein the tuner chip further comprises a frequency-to-voltage converter coupled to convert the clock signal frequency into a control voltage which is applied to the lowpass filter to adjust the cutoff frequency.
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Abstract
An improved satellite receiver front end architecture having a tuner chip and a demodulator/decoder chip. The tuner chip includes a lowpass filter having a configurable cutoff frequency, and the tuner chip uses a frequency signal to provide accurate adjustment of the cutoff frequency. A clock signal having a clock frequency is converted into a control voltage which determines the cutoff frequency of the lowpass filter. Consequently, the cutoff frequency may be increased by increasing the clock frequency, or decreased by decreasing the clock frequency. This configuration provides for improved cutoff frequency control in the presence of signal interference.
77 Citations
12 Claims
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1. A DBS receiver front end comprising:
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a tuner chip having a lowpass filter with a configurable cutoff frequency, wherein the tuner is configured to adjust the cutoff frequency based on a clock signal frequency of a clock signal, wherein the tuner chip is further configured to receive a receive signal, to convert the receive signal to a product signal, and to filter the product signal with the lowpass filter to provide a baseband signal; and a demodulator/decoder chip coupled to receive the baseband signal and configured to convert the baseband signal to a decoded signal, wherein the demodulator/decoder chip is further configured to provide said clock signal, wherein the tuner chip further comprises a frequency-to-voltage converter coupled to convert the clock signal frequency into a control voltage which is applied to the lowpass filter to adjust the cutoff frequency. - View Dependent Claims (2)
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3. A DBS receiver front end comprising:
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a tuner chip having a lowpass filter with a configurable cutoff frequency, wherein the tuner is configured to adjust the cutoff frequency based on a clock signal frequency of a clock signal, wherein the tuner chip is further configured to receive a receive signal, to convert the receive signal to a product signal, and to filter the product signal with the lowpass filter to provide a baseband signal; and a demodulator/decoder chip coupled to receive the baseband signal and configured to convert the baseband signal to a decoded signal, wherein the demodulator/decoder chip is further configured to provide said clock signal, wherein the demodulator/decoder chip further comprises; a crystal oscillator configured to provide a timing signal having a crystal resonance frequency; a programmable divider coupled to receive the timing signal, wherein the programmable divider is configured to provide said clock signal by dividing the crystal resonance frequency by an adjustable constant. - View Dependent Claims (4, 5, 6)
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7. A tuner configured to receive a receive signal and convert the receive signal into a baseband signal, wherein the tuner comprises:
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a lowpass filter with an adjustable cutoff frequency to control a bandwidth of the baseband signal, wherein the cutoff frequency is determined by a control voltage; a frequency-to-voltage converter configured to receive a clock signal having a clock signal frequency, wherein the frequency to voltage converter is further configured to convert the clock signal frequency into the control voltage. - View Dependent Claims (8, 9, 10)
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11. A method for converting a receive signal to a baseband signal, wherein the method comprises:
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setting a tuning frequency signal to indicate a desired reception frequency; providing a clock signal frequency of a clock signal to indicate a desired reception bandwidth; determining a lowpass filter cutoff frequency from said clock signal frequency; receiving the receive signal; combining the tuning frequency signal with the receive signal to produce a product signal; and lowpass filtering the product signal to attenuate signal energy above the cutoff frequency, wherein said determining comprises; filtering the clock signal to produce a phase shifted signal; mixing the phase shifted signal with the clock signal to produce a mixed signal; and lowpass filtering the mixed signal to produce a cutoff frequency control voltage.
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12. A method for converting a receive signal to a baseband signal, wherein the method comprises:
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setting a tuning frequency signal to indicate a desired reception frequency; providing a clock signal frequency of a clock signal to indicate a desired reception bandwidth; determining a lowpass filter cutoff frequency from said clock signal frequency; receiving the receive signal; combining the tuning frequency signal with the receive signal to produce a product signal; and lowpass filtering the product signal to attenuate signal energy above the cutoff frequency, wherein said providing comprises; receiving a crystal oscillation signal; counting cycles in the crystal oscillation signal with a counter; and restarting the counter when a programmable value is reached.
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Specification