Claims
- 1. An integrated circuit formed on a semiconductor chip, comprising:
(a) a low pass filter circuit having a first resistor of a first resistance value and a capacitor of a first capacitance value, wherein said first resistance value and said first capacitance value determine a comer frequency of said filter; and (b) a tuning circuit having a second resistor of a second resistance value, a switched-capacitor of a third resistance value and a comparator that compares two voltage signals to produce a control signal, wherein said control signal adjusts said first and second resistance values as a function of said third resistance value.
- 2. The integrated circuit of claim 1, wherein a first one of said two voltage signals is coupled to said switched-capacitor and a second one of said two voltage signals is coupled to said first means such that said comer frequency of said filter is adjusted by varying at least one of said two voltage signals.
- 3. The integrated circuit of claim 1, further comprising a clock to control said switched-capacitor, wherein said corner frequency of said filter can be adjusted by varying frequency of said clock.
- 4. The integrated circuit of claim 1, wherein a first one of said two voltage signals is coupled to said switched-capacitor and a second one of said two voltage signals is coupled to said comparator, wherein said integrated circuit further comprises a clock having a frequency that controls said switched-capacitor, and wherein said comer frequency of said filter is adjusted by changing at least one of said two voltage signals, or by changing the frequency of said clock.
- 5. The integrated circuit of claim 1, wherein said low pass filter circuit further comprises an amplifier.
- 6. The integrated circuit of claim 5, wherein said low pass filter circuit comprises an inverting integrator.
- 7. The integrated circuit of claim 6, wherein said amplifier is an operational amplifier.
- 8. The integrated circuit of claim 1, wherein said control signal simultaneously adjusts said first and second resistance values.
- 9. The integrated circuit of claim 8, wherein said first and second resistance values are substantially the same.
- 10. The integrated circuit of claim 1, wherein said comparator comprises an amplifier and an analog-to-digital converter.
- 11. The integrated circuit of claim 10, wherein said amplifier is an operational amplifier.
- 12. The integrated circuit of claim 11, wherein said first resistor comprises a first plurality of selectable resistors, said second resistor comprises a second plurality of selectable resistors, and said control signal comprises a digital value that adjusts said first and second resistance values by selecting at least one particular resistor in each of said first and second plurality of selectable resistors.
- 13. The integrated circuit of claim 1, wherein said tuning circuit further comprises an amplifier having an inverting input, a non-inverting input coupled to ground and an output coupled to said comparator, said switched-capacitor being coupled between a first one of said two voltage signals and said inverting input, and said second resistor being coupled to said inverting input and said output.
- 14. The integrated circuit of claim 13, wherein said amplifier is an operational amplifier.
- 15. In an integrated circuit having a low pass filter circuit with a first resistor of a first resistance value and a capacitor of a first capacitance value, wherein the first resistance value and the first capacitance value determine a corner frequency of the filter, a method comprising:
(a) receiving two voltage signals at a tuning circuit having a second resistor of a second resistance value and a switched-capacitor of a third resistance value; (b) comparing the two voltage signals at the tuning circuit to produce a control signal; and (c) adjusting, using the control signal, the first and second resistance values as a function of the third resistance value, thereby adjusting the corner frequency fo the filter.
- 16. The method of claim 15, further comprising:
varying at least one of the two voltage signals to thereby adjust the corner frequency of the filter.
- 17. The method of claim 15, further comprising:
providing a clock signal to control the switched-capacitor; and varying a frequency of the clock signal to thereby adjust the corner frequency of the filter.
- 18. The method of claim 15, further comprising:
providing a clock signal to control the switched-capacitor; and at least one of varying frequency of the clock signal to thereby adjust the corner frequency of the filter; and varying at least one of the two voltage signals to thereby adjust the corner frequency of the filter.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Application No. 60/250,616, filed Nov. 29, 2000, titled “Fully Integrated Direct Conversion Satellite Receiver,” which is incorporated herein by reference. This application is also related to the following U.S. Non-Provisional applications, which are filed on the same date as the present application, and are herein incorporated-by-reference in their entireties:
[0002] “Integrated Direct Conversion Satellite Tuner”, Attorney Docket No. 1875.1210001; and
[0003] “Apparatus for Reducing Flicker Noise in a Mixer Circuit”, Attorney Docket No. 1875.1210003.
Provisional Applications (1)
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Number |
Date |
Country |
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60250616 |
Nov 2000 |
US |