Claims
- 1. A method, comprising:
(a) forming a filter through coupling a first resistor having a first resistance value and a capacitor having a first capacitance value; (b) setting a corner frequency of the filter using the first resistance value and the first capacitance value; and (c) forming a tuning device through coupling a second resistor having a second resistance value, a switched-capacitor having a third resistance value, and a comparator having an amplifier and a signal converter; and (d) comparing voltage signals using the comparator to produce a control signal that adjusts the first and second resistance values as a function of the third resistance value.
- 2. The method of claim 1, further comprising:
receiving a first one of the voltage signals from the switched-capacitor; receiving a second one of the voltage signals from a reference source; and adjusting the corner frequency of the filter through varying at least one of the first and second voltage signals.
- 3. The method of claim 1, further comprising:
using a clock to control the switched-capacitor, such that varying frequency of the clock adjusts the corner frequency.
- 4. The method of claim 1, further comprising:
receiving a first one of the voltage signals from the switched-capacitor; receiving a second one of the voltage signals from a reference source; using a frequency of a clock to control the switched-capacitor; and changing at least one of the first and second voltage signals or changing the frequency of the clock to adjust the corner frequency of the filter.
- 5. The method of claim 1, wherein step (a) further comprises coupling an amplifier to the resistor and the capacitor.
- 6. The method of claim 5, wherein step (a) further comprises configuring the amplifier as an inverting integrator.
- 7. The method of claim 5, wherein step (a) further comprises using an operational amplifier as the amplifier.
- 8. The method of claim 1, wherein step (d) further comprises using the control signal to substantially simultaneously adjust the first and second resistance values.
- 9. The method of claim 8, wherein step (d) further comprises adjusting the first and second resistance values, such that the first and second resistance values are substantially equal.
- 10. The method of claim 1, wherein step (c) further comprises using an operational amplifier as the amplifier.
- 11. The method of claim 1, further comprising:
coupling together a first plurality of selectable resistors to form the first resistor; coupling together a second plurality of selectable resistors to form the second resistor; using a digital value as the control signal; and adjusting the first and second resistance values by selecting at least one particular resistor in each of the first and second plurality of selectable resistors.
- 12. The method of claim 1, wherein step (c) further comprises:
providing an amplifier in the tuning device; coupling a non-inverting input of the amplifier in the tuning device to ground; coupling an output of the amplifier in the tuning device to the comparator; coupling the switched-capacitor between a first one of the voltage signals and the inverting input of the amplifier in the tuning device; and coupling the second resistor between the inverting input and the output of the amplifier in the tuning device.
- 13. The method of claim 12, wherein step (c) further comprises using an operational amplifier as the amplifier in the tuning device.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Ser. No. 09/995,795 (published as U.S. Pub. App. No. 2002/0190783 A1), filed Nov. 29, 2001, entitled “Low Pass Filter Corner Frequency Tuning Circuit And Method,” which claims the benefit of U.S. Provisional Application No. 60/250,616 (“the '616 Provisional”), filed Nov. 29, 2000, titled “Fully Integrated Direct Conversion Satellite Receiver,” which are both incorporated herein by reference in their entireties.
[0002] This application is also related to the following U.S. Non-Provisional applications, which are all incorporated by reference herein in their entireties.
[0003] U.S. Ser. No. 10/647,588, filed Aug. 26, 2003, which is a divisional of U.S. Ser. No. 09/995,695 (published as U.S. Pub. App. No. 2003/0045263 A1), filed Nov. 29, 2001, entitled “Integrated Direct Conversion Satellite Tuner,” which claimed benefit to the '616 provisional.
[0004] U.S. Ser. No. 09/995,690 (published as U.S. Pub. App. No. 2002/0120937 A1), filed Nov. 29, 2001, entitled “Apparatus for Reducing Flicker Noise in a Mixer Circuit,” which claimed benefit to the '616 provisional.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60250616 |
Nov 2000 |
US |
Continuations (1)
|
Number |
Date |
Country |
Parent |
09995795 |
Nov 2001 |
US |
Child |
10767424 |
Jan 2004 |
US |