APPARATUS AND METHOD OF SELECTING COMPONENTS FOR A RECONFIGURABLE IMPEDANCE MATCH CIRCUIT

• US 20090167457A1
• Filed: 11/09/2006
• Published: 07/02/2009
• Est. Priority Date: 11/10/2005
• Status: Active Grant

• Current Assignee: Arizona Board of Regents (University of Arizona)
• Original Assignee: The Arizona BD of REG On Behalf of The University of AZ
• Inventors: Whatley, Richard B., Melde, Kathleen Lowe
• Granted Patent: US 8,067,997 B2
• Time in Patent Office: Days
• US Class Current: 333/32
• CPC Class Codes: H01P 5/04 with variable factor of coupling

Abstract

A method of selecting component values for an analog circuit includes identifying a cost function that evaluates similarity between an approximate frequency response function and a preferred frequency response function for at least one characteristic of the functions, determining the approximate frequency response function of the analog circuit based on an approximate component value, and changing the approximate component value based on a determined magnitude of similarity between the preferred frequency response function and the approximate frequency response function for the at least one characteristic. An impedance matching apparatus includes a mismatch detection circuit that produces a difference between source and load impedances, a match network controller that produces a control value based on the difference, and a reconfigurable varactor match network including at least one stub mounted varactor having a capacitance controlled by the control value to match the source and load impedances.

Claims

1. A method of selecting a component value for a component in an analog circuit, the method comprising steps of:

identifying a cost function that evaluates a magnitude of a similarity between an approximate frequency response function and a preferred frequency response function for at least one characteristic of the functions;

determining the approximate frequency response function of the analog circuit based on an approximate value of the component;

determining the magnitude of the similarity between the preferred frequency response function and the approximate frequency response function for the at least one characteristic of the functions; and

changing the approximate value of the component in the analog circuit based on the determined magnitude to select the component value.

2. The method of claim 1, further comprising:

decreasing the magnitude of the similarity prior to the changing when a value of the approximate frequency response function exceeds a predetermined threshold.

3. The method of claim 1, further comprising:

selecting the at least one characteristic of the functions to be at least one of a mean value of the function in a passband, a flatness value of the function in the passband, and a skewness value of the function in the passband.

4. The method of claim 3, further comprising:

determining the flatness value of the function in the passband based on the fourth statistical moment of the function in the passband.

5. The method of claim 3, further comprising:

determining the skewness value of the function in the passband based on the third statistical moment of the function in the passband.

6. The method of claim 3, further comprising:

determining the mean value of the function in the passband based on the first statistical moment of the function in the passband.

7. The method of claim 3, wherein the cost function is defined as:

$\mathrm{Cost}=a·<br><br><br><br>{\mathrm{\mu <br><br>}}_x<br><br>-b·<br><br><br><br>\frac{\sum <br><br>{\left(X-{\mathrm{\mu <br><br>}}_x\right)}^4}{N<br><br><br><br>{\mathrm{\sigma <br><br>}}_x^4}-3<br><br>-c·<br><br><br><br>\frac{\sum <br><br><br><br>X-{\mathrm{\mu <br><br>}}_x<br><br>}{N<br><br><br><br>{\mathrm{\sigma <br><br>}}_x^3}<br><br>-\mathrm{Penalty}$

where Cost is the magnitude of the similarity of the approximate and preferred frequency response functions, a is a weighting factor for the mean value of the approximate frequency response function, b is a weighting factor for the flatness value of the approximate frequency response function, c is a weighting factor for the skewness value of the approximate frequency response function, μ

_x is the mean value of the approximate frequency response function in the passband, X is a value of the approximate frequency response function in the passband, N is a number of values in the approximate frequency response function in the passband, σ

_x is the standard deviation of the approximate frequency response function in the passband, and Penalty is an amount of reduction of the magnitude of the similarity when the approximate frequency response function exceeds a predetermined threshold in the passband.

8. An impedance matching apparatus for matching an impedance of a source to an impedance of a load, the apparatus comprising:

a mismatch detection circuit connected to the load and configured to receive information regarding the impedance of the source, determine the impedance of the load, and produce a difference between the source and load impedances;

a match network controller configured to receive the difference between the source and load impedances from the mismatch detection circuit and produce a control value based on the difference; and

a matching network including a continuously variable impedance controlled by the control value to match the impedance of the source to the impedance of the load.

9. The apparatus of claim 8, wherein the matching network includes at least one varactor configured to be controlled by the control value from the match network to vary a capacitance of the varactor.

10. The apparatus of claim 9, wherein at least one of the at least one varactor is mounted on a stub.

11. The apparatus of claim 8, wherein the reconfigurable varactor match network includes plural shunt resonant stubs with a varactor in each stub, and the control value includes a varactor control voltage for each varactor.

12. The apparatus of claim 11, wherein the plural shunt resonant stubs are symmetrically arranged around a central resonator located in between the source and the load.

14. The apparatus of claim 8, wherein the mismatch detection circuit further comprises:

a first four port coupler including a first input port connected to the source, a first through port, a first coupled port, and a first isolated port;

a second four port coupler including a second input port connected to the first through port of the first four port coupler, a second through port connected to the load, a second coupled port, and a second isolated port connected to the first isolated port of the first four port coupler;

a current sensing resistor having a first end connected to the isolated port of the first four port coupler, the isolated port of the second four port coupler, and an anode of a first input diode;

the first input diode having a cathode connected to a first end of a first capacitor and a first end of a first input resistor;

the first capacitor having a second end connected to ground;

the first input resistor having a second end connected to a non-inverting input of a first operational amplifier, a cathode of a first output diode, and a first end of a first output resistor;

the first output diode having an anode connected to an output of the first operational amplifier;

the first operational amplifier having a non-inverting input connected to ground;

the first output resistor having a second end connected to ground;

a second input diode having an anode connected to the second coupled port of the second four port coupler and a first end of a voltage sensing resistor, and a cathode connected to a first end of a second capacitor and a first end of a second input resistor;

the voltage sensing resistor having a second end connected to ground;

the second capacitor having a second end connected to ground;

the second input resistor having a second end connected to a non-inverting input of a second operational amplifier, a first end of a second output resistor, and a cathode of a second output diode;

the second output diode having an anode connected to an output of the second operational amplifier;

the second output resistor having a second end connected to ground; and

the second operational amplifier having an inverting input connected to ground,

wherein a voltage difference between the outputs of the first and second operational amplifiers represents the magnitude of the impedance difference.

13. An impedance matching apparatus for matching an impedance of a source to an impedance of a load, the apparatus comprising:

a mismatch detection circuit connected to the load and configured to receive information regarding the impedance of the source, determine the impedance of the load, and produce a difference between the source and load impedances;

a match network controller configured to receive the difference between the source and load impedances from the mismatch detection circuit and produce a control value based on the difference; and

means connected between the source and the load for varying a continuously variable impedance based on the control value to match the impedance of the source with the impedance of the load.

15. A mismatch detection circuit configured to detect a magnitude of an impedance difference between an impedance of a source and an impedance of a load, the apparatus comprising:

a first four port coupler including a first input port connected to the source, a first through port, a first coupled port, and a first isolated port;

a second four port coupler including a second input port connected to the first through port of the first four port coupler, a second through port connected to the load, a second coupled port, and a second isolated port connected to the first isolated port of the first four port coupler;

a current sensing resistor having a first end connected to the isolated port of the first four port coupler, the isolated port of the second four port coupler, and an anode of a first input diode;

the first input diode having a cathode connected to a first end of a first capacitor and a first end of a first input resistor;

the first capacitor having a second end connected to ground;

the first input resistor having a second end connected to a non-inverting input of a first operational amplifier, a cathode of a first output diode, and a first end of a first output resistor;

the first output diode having an anode connected to an output of the first operational amplifier;

the first operational amplifier having a non-inverting input connected to ground;

the first output resistor having a second end connected to ground;

a second input diode having an anode connected to the second coupled port of the second four port coupler and a first end of a voltage sensing resistor, and a cathode connected to a first end of a second capacitor and a first end of a second input resistor;

the voltage sensing resistor having a second end connected to ground;

the second capacitor having a second end connected to ground;

the second input resistor having a second end connected to a non-inverting input of a second operational amplifier, a first end of a second output resistor, and a cathode of a second output diode;

the second output diode having an anode connected to an output of the second operational amplifier;

the second output resistor having a second end connected to ground; and

the second operational amplifier having an inverting input connected to ground,

wherein a voltage difference between the outputs of the first and second operational amplifiers represents the magnitude of the impedance difference.

16. A computer program product storing program instructions which, when executed by a computer to select a component value for a component in an analog circuit, result in the computer performing steps comprising:

identifying a cost function that evaluates a magnitude of a similarity between an approximate frequency response function and a preferred frequency response function for at least one characteristic of the functions;

determining the approximate frequency response function of the analog circuit based on an approximate value of the component;

determining the magnitude of the similarity between the preferred frequency response function and the approximate frequency response function for the at least one characteristic of the functions; and

changing the approximate value of the component in the analog circuit based on the determined magnitude to select the component value.

17. The computer program product of claim 16, wherein said program instructions result in the computer performing further steps comprising:

decreasing the magnitude of the similarity prior to the changing when a value of the approximate frequency response function exceeds a predetermined threshold.

18. The computer program product of claim 16, wherein said program instructions result in the computer performing further steps comprising:

selecting the at least one characteristic of the functions to be at least one of a mean value of the function in a passband, a flatness value of the function in the passband, and a skewness value of the function in the passband.

19. The computer program product of claim 18, wherein said program instructions result in the computer performing further steps comprising:

determining the flatness value of the function in the passband based on the fourth statistical moment of the function in the passband.

20. The computer program product of claim 18, wherein said program instructions result in the computer performing further steps comprising:

determining the skewness value of the function in the passband based on the third statistical moment of the function in the passband.

21. The computer program product of claim 18, wherein said program instructions result in the computer performing further steps comprising:

determining the mean value of the function in the passband based on the first statistical moment of the function in the passband.

22. The computer program product of claim 18, wherein said program instructions result in the computer performing the cost function, which is defined as:

$\mathrm{Cost}=a·<br><br><br><br>{\mathrm{\mu <br><br>}}_x<br><br>-b·<br><br><br><br>\frac{\sum <br><br>{\left(X-{\mathrm{\mu <br><br>}}_x\right)}^4}{N<br><br><br><br>{\mathrm{\sigma <br><br>}}_x^4}-3<br><br>-c·<br><br><br><br>\frac{\sum <br><br><br><br>X-{\mathrm{\mu <br><br>}}_x<br><br>}{N<br><br><br><br>{\mathrm{\sigma <br><br>}}_x^3}<br><br>-\mathrm{Penalty}$

where Cost is the magnitude of the similarity of the approximate and preferred frequency response functions, a is a weighting factor for the mean value of the approximate frequency response function, b is a weighting factor for the flatness value of the approximate frequency response function, c is a weighting factor for the skewness value of the approximate frequency response function, μ

_x is the mean value of the approximate frequency response function in the passband, X is a value of the approximate frequency response function in the passband, N is a number of values in the approximate frequency response function in the passband, σ

_x is the standard deviation of the approximate frequency response function in the passband, and Penalty is an amount of reduction of the magnitude of the similarity when the approximate frequency response function exceeds a predetermined threshold in the passband.