FILTER SHAPING USING A SIGNAL CANCELLATION FUNCTION

• US 20100244943A1
• Filed: 03/27/2009
• Published: 09/30/2010
• Est. Priority Date: 03/27/2009
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Quellan, Inc. (Renesas Electronics Corporation)
• Inventors: Chen, Wei, Hahn, Wilhelm Steffen
• Granted Patent: US 8,380,771 B2
• Time in Patent Office: Days
• US Class Current: 327/553
• CPC Class Codes: G06F 17/00 Digital computing or data processing equipment or methods, specially adapted for specific functions information retrieval, database structures or file system structures therefor G06F16/00
• CPC Class Codes: H03H 11/1291 Current or voltage controlled filters
• CPC Class Codes: H03H 2011/0488 Notch or bandstop filters
• CPC Class Codes: H03K 5/125 Discriminating pulses measuring characteristics of individual pulses G01R29/02; separation of synchronising signals in television systems H04N5/08

Abstract

A signal filter and accompanying methods. In one embodiment, the filter includes a first mechanism for receiving a first signal. A second mechanism employs one or more modified representations of the first signal to cancel one or more frequency components of the first signal, yielding an output signal in response thereto. In a more specific embodiment, the first mechanism includes a splitter for receiving the first signal and splitting the first signal onto a first path and a second path. The second mechanism further includes one or more delay modules and one or more phase shifters in the first path and/or the second path. One or more controllable amplifiers are optionally included in the first path and/or the second path. The one or more delay modules, phase shifters, or amplifiers are responsive to one or more control signals from a controller. The controller is adapted to modify behavior of the second mechanism so that the filter is characterized by a desired frequency response.

Claims

1. A filter comprising:

first means for receiving a first signal; and

second means for employing one or more modified representations of the first signal to suppress one or more frequency components of the first signal, yielding an output signal in response thereto.

2. The filter of claim 1, wherein the first means includes a splitter adapted to receive the first signal and split the first signal onto a first path and a second path.

3. The filter of claim 2, wherein the second means includes one or more delay modules and one or more phase shifters in the first path and/or the second path.

4. The filter of claim 3, further including one or more amplifiers in the first path or the second path.

5. The filter of claim 4, wherein one or more of the one or more delay modules, phase shifters, or amplifiers are responsive to one or more control signals from a controller.

6. The filter of claim 5, wherein the controller is adapted to modify behavior of the second means so that filter is characterized by a desired frequency response.

7. The filter of claim 1, wherein the filter implements a controllable notch filter, the controllable notch filter being controllable in part via one or more controllable Variable Gain Amplifiers (VGAs) included in the second means, the one or more controllable VGAs affecting alignment of a modified representation of the first signal relative to the first signal itself.

8. The filter of claim 7, wherein the second means includes third means for combining the modified representation of the first signal with the first signal to yield an output signal, wherein the output signal is representative of the first signal with certain frequency components thereof cancelled or suppressed.

9. The filter of claim 7, wherein one or more instances of the notch filter are implemented in a combined filter that includes a second filter.

10. The filter of claim 9, wherein a transfer function or frequency response of the combined filter is characterized by an asymmetrical frequency response curve.

11. The filter of claim 9, wherein the second filter includes a bandpass filter.

12. The filter of claim 11, further including a controller in communication with the one or more instances of the notch filter.

13. The filter of claim 12, wherein the controller includes instructions for calibrating the combined filter to yield a combined desired transfer function based on one or more predetermined inputs to the controller.

14. The filter of claim 13, wherein the one or more predetermined inputs include temperature.

15. A filter comprising:

first means for receiving a first signal; and

second means for employing the first signal to selectively cancel a predetermined spectral component of the first signal to provide a desired frequency response of the filter.

16. A selective spectrum self-canceler filter comprising:

a splitter for separating an input signal into a first signal and a second signal; and

a frequency dependent aligner for selectively aligning a portion of a modified version of the second signal with the first signal so that when the first signal is combined with the second signal, the resulting output signal is representative of the input signal with cancelled frequency components.

17. The filter of claim 16, further including a controller in communication with the frequency dependent aligner.

18. The filter of claim 16, wherein the controller includes instructions for adjusting modification of the second signal by the frequency dependent aligner to selectively alter a frequency response of the filter.

19. The filter of claim 16, wherein the first signal is representative of a copy of the input signal.

20. The filter of claim 16, wherein the frequency dependent aligner includes a delay module adapted to shift a predetermined range of frequencies of the second signal relative to the first signal.

21. The filter of claim 20, wherein the delay module includes a bandpass filter.

22. The filter of claim 21, wherein the bandpass filter includes a Quality factor (Q) enhancer.

23. The filter of claim 20, wherein the frequency dependent aligner further includes a phase shifter coupled to the delay module, wherein the phase shifter is adapted to shift a phase of the second signal.

24. The filter of claim 23, wherein the phase shifter includes one or more controllable VGAs, the outputs of which affect alignment of the second signal relative to the first signal.

25. The filter of claim 24, further including a controller in communication with the phase shifter and the delay module, wherein the controller is adapted to adjust behavior of the delay module and the phase shifter to facilitate shaping a frequency response of the filter.

26. The filter of claim 25, wherein the controller receives the output signal and the input signal as inputs and provides control output to the one or more controllable VGAs and to one or more controllable capacitors or resistors of the delay module.

27. The filter of claim 26, wherein the controller further receives a temperature signal as input and includes instructions for adjusting behavior of the delay module and the phase shifter based on the temperature signal.

28. The filter of claim 23, wherein the phase shifter is coupled to an output of the delay module, the output of the phase shifter representative of a first version of the second signal.

31. The filter of claim 20, wherein the frequency dependent aligner further includes an In-phase/Quadrature (IQ) modulator adapted to modify the second signal by shifting a predetermined spectral component of the second signal relative to the first signal.

29. The filter of claim 29, further including an amplifier coupled to an output of the phase shifter for selectively amplifying the first version of the second signal and providing the modified version of the second signal in response thereto.

30. The filter of claim 29, wherein the delay module, phase shifter, and amplifier are configured to align the modified version of the second signal with the first signal to yield the output signal that has been modified in accordance with a desired transfer function of the filter.

32. A filter comprising:

a first module adapted to separate a first signal traveling along a first path into a second signal travelling along a second path and a third signal travelling along a third path;

a second module adapted to selectively shift a frequency component of the second signal relative to the third signal in accordance with a desired frequency response of the filter, resulting in one or more shifted signals in response thereto;

a third module adapted to combine the shifted signals into an output signal so that the filter is characterized by the desired frequency response.

33. The filter of claim 32, wherein the second module includes an adjustable phase shifter coupled to an adjustable delay module.

34. The filter of claim 32, wherein the desired frequency response includes a notched frequency response.

35. A method for implementing a filter with a desired transfer function, the method comprising:

determining a first notch frequency response;

determining a first bandpass frequency response;

determining a desired total frequency response; and

selectively combining one or more controllable notch filters characterized by one or more versions of the first notch frequency response with one or more bandpass filters characterized by one or more versions of the bandpass frequency response to yield a combined filter characterized by a version of the desired total frequency response.

36. The method of claim 35, wherein the one or more controllable notch filters include one or more selective spectrum self-canceler filters.

37. A method for filtering a signal, the method comprising:

receiving an input signal;

splitting the input signal onto a first path and a second path; and

selectively delaying and/or phase shifting a signal on the first path and/or the second path so that when signals on the first path and second path are combined, the resulting output signal exhibits desired spectral characteristics.