Calibration of step attenuator
View Patent ↗System and method for calibrating a step attenuator. N attenuation measurements of a step attenuator may be received, where the step attenuator includes M series-connected attenuation sections. Each attenuation section may be configured to switchably provide a respective level of attenuation, where N is greater than M, and where the step attenuator may be modeled via M+1 coefficients, including a coefficient for a no-attenuation state and respective coefficients for the attenuation sections. Values of the coefficients may be determined via least squares estimation using the N attenuation measurements, thereby calibrating the step attenuator.
1. A non-transitory computer accessible memory medium that stores program instructions executable by a processor to implement:
receiving N attenuation measurements of a step attenuator, wherein the step attenuator comprises M series-connected attenuation sections, wherein each attenuation section is configured to be switchable to provide a respective level of attenuation, wherein N is greater than M, and wherein the step attenuator is modeled via M+1 coefficients, comprising a coefficient for a no-attenuation state and respective coefficients for the attenuation sections; and
calibrating the step attenuator, wherein calibrating the step attenuator comprises determining, via least squares estimation using the N attenuation measurements, values of the coefficients.
2. The non-transitory computer accessible memory medium of claim 1 , wherein the program instructions are further executable to implement:
performing said receiving N attenuation measurements and said determining values of the coefficients for a respective input signal at each frequency of a plurality of frequencies.
3. The non-transitory computer accessible memory medium of claim 1 , wherein the step attenuator is controlled by an M-bit binary control index, wherein each bit is a respective binary attenuation index, and wherein M binary attenuation indices b 1 -b M respectively control the M attenuation sections.
4. The non-transitory computer accessible memory medium of claim 3 , wherein the program instructions are further executable to implement:
modeling the step attenuator as a linear combination of attenuation terms for the respective attenuation sections, comprising:
L i =k 0 +k 1 *b 1 +k 2 *b 2 + . . . +k M *b M ,
wherein k 0 -k M are the M+1 coefficients, and L i represents an attenuation measurement of the N attenuation measurements.
5. The non-transitory computer accessible memory medium of claim 4 , wherein said determining the values of the coefficients comprises solving a system of linear equations defined by an augmented control matrix, a coefficient vector k, and a measured attenuation vector L i=0 . . . N , comprising:
[
1
b
01
b
02
…
b
0
M
1
b
11
…
…
b
1
M
…
…
…
…
…
…
…
…
…
…
1
b
N
1
b
N
2
…
b
NM
]
[
k
0
k
1
…
…
k
M
]
=
[
L
0
L
1
…
…
L
N
]
,
wherein each matrix row specifies a respective activation pattern of the attenuation sections, wherein at least M+1 of the linear equations are linearly independent, and wherein L i is a respective attenuation measurement of the attenuation vector.
6. The non-transitory computer accessible memory medium of claim 5 , wherein the step attenuator is comprised in a device, wherein L i is a respective attenuation measurement for the device, including the step attenuator.
7. The non-transitory computer accessible memory medium of claim 5 , wherein N is greater than M+1, and wherein the system of linear equations is over-determined.
8. The non-transitory computer accessible memory medium of claim 1 , wherein the step attenuator is configurable to provide a range of attenuation values, wherein the attenuation measurements are made at respective attenuation values of the step attenuator within a specified sub-range of the range.
9. The non-transitory computer accessible memory medium of claim 8 , wherein the sub-range omits at least one lowest value of the range.
10. The non-transitory computer accessible memory medium of claim 8 , wherein the sub-range omits at least one highest value of the range.
11. A computer-implemented method for calibrating a step attenuator, comprising:
utilizing a computer to perform:
receiving N attenuation measurements of a step attenuator, wherein the step attenuator comprises M series-connected attenuation sections, wherein each attenuation section is configured to be switchable to provide a respective level of attenuation, wherein N is greater than M, and wherein the step attenuator is modeled via M+1 coefficients, comprising a coefficient for a no-attenuation state and respective coefficients for the attenuation sections; and
calibrating the step attenuator, wherein calibrating the step attenuator comprises determining, via least squares estimation using the N attenuation measurements, values of the coefficients.
12. The computer-implemented method of claim 11 , further comprising:
performing said receiving N attenuation measurements and said determining values of the coefficients for a respective input signal at each frequency of a plurality of frequencies.
13. The computer-implemented method of claim 11 , wherein the step attenuator is controlled by an M-bit binary control index, wherein each bit is a respective binary attenuation index, and wherein M binary attenuation indices b 1 -b M respectively control the M attenuation sections.
14. The computer-implemented method of claim 13 , wherein the program instructions are further executable to:
model the step attenuator as a linear combination of attenuation terms for the respective attenuation sections, comprising:
L i =k 0 +k 1 *b 1 +k 2 *b 2 + . . . +k M *b M ,
wherein k 0 -k M are the M+1 coefficients, and L i represents an attenuation measurement of the N attenuation measurements.
15. The computer-implemented method of claim 14 , wherein said determining the values of the coefficients comprises solving a system of linear equations defined by an augmented control matrix, a coefficient vector k, and a measured attenuation vector L i=0 . . . N , comprising:
[
1
b
01
b
02
…
b
0
M
1
b
11
…
…
b
1
M
…
…
…
…
…
…
…
…
…
…
1
b
N
1
b
N
2
…
b
NM
]
[
k
0
k
1
…
…
k
M
]
=
[
L
0
L
1
…
…
L
N
]
wherein each matrix row specifies a respective activation pattern of the attenuation sections, wherein at least M+1 of the linear equations are linearly independent, and wherein L i is a respective attenuation measurement of the attenuation vector.
16. The computer-implemented method of claim 15 , wherein the step attenuator is comprised in a device, wherein L i is a respective attenuation measurement for the device, including the step attenuator.
17. The computer-implemented method of claim 15 , wherein N is greater than M+1, and wherein the system of linear equations is over-determined.
18. The computer-implemented method of claim 11 , wherein the step attenuator is configurable to provide a range of attenuation values, wherein the attenuation measurements are made at respective attenuation values of the step attenuator within a specified sub-range of the range.
19. The computer-implemented method of claim 18 , wherein the sub-range omits at least one lowest value of the range.
20. The computer-implemented method of claim 18 , wherein the sub-range omits at least one highest value of the range.