Digital-to-analog converter with non-uniform resolution
A circuit includes a digital-to-analog converter with non-uniform resolution for converting a digital signal into an analog signal. The digital-to-analog converter includes high-resolution circuitry, reduced-resolution circuitry coupled to the high-resolution circuitry and a switch coupled to the high-resolution circuitry and to the reduced-resolution circuitry. The switch couples one of the high-resolution circuitry and the reduced-resolution circuitry to an output node. The circuit also includes a decoder coupled to the switch. The decoder receives the digital signal to control the switch.
1. A circuit, comprising:
a digital-to-analog converter having an input for receiving a digital signal;
a voltage-controlled oscillator coupled to the digital-to-analog converter, comprising a capacitor bank coupled to a plurality of switches for adjusting an operating range of the voltage-controlled oscillator; and
an operating range controller coupled to the voltage controlled oscillator configured to determine whether the digital signal at the digital-to-analog converter input corresponds to a designated operating range and control the plurality of switches to adjust the operating range of the voltage-controlled oscillator if the digital signal does not correspond to the designated operating range.
2. The circuit of claim 1 , wherein the designated operating range corresponds to a high-resolution operating region of the digital-to-analog converter.
3. The circuit of claim 1 , wherein the designated operating range comprises a range within a high-resolution operating region of the digital-to-analog converter.
4. The circuit of claim 1 , wherein the circuit is used in conjunction with a modulator.
5. The circuit of claim 1 , wherein the operating range controller adjusts the operating range by:
determining a first adjustment based on the digital signal; and
applying the first adjustment to the voltage-controlled oscillator.
6. The circuit of claim 5 , wherein the first adjustment is determined according to the equation
N
A
1
=
K
vco
(
H
z
/
LSB
)
×
(
N
DA
C
_
1
-
Center
)
K
acq
(
H
z
/
LSB
)
,
wherein N A1 is the first adjustment, K vco is a voltage-controlled oscillator gain or tuning sensitivity expressed in hertz (Hz) per least significant bit (LSB), K acq is a gain or tuning sensitivity of an acquisition code expressed in hertz (Hz) per least significant bit (LSB), N DAC — 1 is a first digital-to-analog converter input code value from the digital signal and Center is a code value corresponding to a center of the designated operating region.
7. The circuit of claim 5 , wherein the operating range controller:
determines whether an updated digital signal corresponds to the designated operating range;
determines a scaled second adjustment based on the first adjustment if the updated digital signal does not correspond to the designated operating range; and
applies the scaled second adjustment to the voltage-controlled oscillator if the updated digital signal does not correspond to the designated operating range.
8. The circuit of claim 7 , wherein the scaled second adjustment is determined according to the equation αN A2 , wherein αN A2 is the second scaled adjustment, wherein N A2 is a second adjustment and
α
=
N
A
1
N
A
1
-
N
A
2
,
wherein N A1 is the first adjustment.
9. The circuit of claim 8 , wherein the second adjustment is determined according to the equation
N
A
2
=
K
vco
(
H
z
/
LSB
)
×
(
N
DAC
_
2
-
Center
)
K
acq
(
H
z
/
LSB
)
,
wherein N A2 is the second adjustment, K vco is a voltage-controlled oscillator gain or tuning sensitivity expressed in hertz (Hz) per least significant bit (LSB), K acq is a gain or tuning sensitivity of an acquisition code expressed in hertz (Hz) per least significant bit (LSB), N DAC — 2 is a second digital-to-analog converter input code value and Center is a code value corresponding to a center of the designated operating region.
10. The circuit of claim 1 , wherein the digital-to-analog converter comprises high-resolution circuitry and reduced-resolution circuitry.
11. A method for controlling an operating range, comprising:
receiving a digital signal by a digital-to-analog converter and an operating range controller;
determining, by the operating range controller, whether the digital signal corresponds to a designated operating range; and
adjusting, by the operating range controller, the operating range of a voltage-controlled oscillator if the digital signal does not correspond to the designated operating range.
12. The method of claim 11 , wherein the designated operating range corresponds to a high-resolution operating region of the digital-to-analog converter.
13. The method of claim 11 , wherein the designated operating range comprises a range within a high-resolution operating region of the digital-to-analog converter.
14. The method of claim 11 , wherein the digital-to-analog converter, the operating range controller and the voltage-controlled oscillator are used in conjunction with a modulator.
15. The method of claim 11 , wherein the operating range controller adjusts the operating range by:
determining a first adjustment based on the digital signal; and
applying the first adjustment to the voltage-controlled oscillator.
16. The method of claim 15 , wherein the first adjustment is determined according to the equation
N
A
1
=
K
vco
(
H
z
/
LSB
)
×
(
N
DA
C
_
1
-
Center
)
K
acq
(
H
z
/
LSB
)
,
wherein N A1 is the first adjustment, K vco is a voltage-controlled oscillator gain or tuning sensitivity expressed in hertz (Hz) per least significant bit (LSB), K acq is a gain or tuning sensitivity of an acquisition code expressed in hertz (Hz) per least significant bit (LSB), N DAC — 1 is a first digital-to-analog converter input code value from the digital signal and Center is a code value corresponding to a center of the designated operating region.
17. The method of claim 15 , further comprising:
determining whether an updated digital signal corresponds to the designated operating range;
determining a scaled second adjustment based on the first adjustment if the updated digital signal does not correspond to the designated operating range; and
applying the scaled second adjustment to the voltage-controlled oscillator if the updated digital signal does not correspond to the designated operating range.
18. The method of claim 17 , wherein the scaled second adjustment is determined according to the equation αN A2 , wherein αN A2 is the second scaled adjustment, wherein N A2 is a second adjustment and
α
=
N
A
1
N
A
1
-
N
A
2
,
wherein N A1 is the first adjustment.
19. The method of claim 18 , wherein the second adjustment is determined according to the equation
N
A
2
=
K
vco
(
H
z
/
LSB
)
×
(
N
DAC
_
2
-
Center
)
K
acq
(
H
z
/
LSB
)
,
wherein N A2 is the second adjustment, K vco is a voltage-controlled oscillator gain or tuning sensitivity expressed in hertz (Hz) per least significant bit (LSB), K acq is a gain or tuning sensitivity of an acquisition code expressed in hertz (Hz) per least significant bit (LSB), N DAC — 2 is a second digital-to-analog converter input code value and Center is a code value corresponding to a center of the designated operating region.
20. The method of claim 11 , wherein the digital-to-analog converter comprises high-resolution circuitry and reduced-resolution circuitry.
21. A computer-program product for controlling an operating range comprising a non-transitory tangible computer-readable medium having instructions thereon for execution by a processor, the instructions comprising:
code causing an operating range controller to determine whether a digital signal corresponds to a designated operating range; and
code for causing the operating range controller to adjust the operating range of a voltage-controlled oscillator if the digital signal does not correspond to the designated operating range.
22. The computer-program product of claim 21 , wherein the designated operating range corresponds to a high-resolution operating region of a digital-to-analog converter.
23. The computer-program product of claim 21 , wherein the designated operating range comprises a range within a high-resolution operating region of the digital-to-analog converter.
24. The computer-program product of claim 21 , the instructions further comprising:
code for causing the operating range controller to determine a first adjustment based on the digital signal; and
code for causing the operating range controller to apply the first adjustment to the voltage-controlled oscillator.
25. The computer-program product of claim 24 , the instructions further comprising:
code for causing the operating range controller to determine whether an updated digital signal corresponds to the designated operating range;
code for causing the operating range controller to determine a scaled second adjustment based on the first adjustment if the updated digital signal does not correspond to the designated operating range; and
code for causing the operating range controller to apply the scaled second adjustment to the voltage-controlled oscillator if the updated digital signal does not correspond to the designated operating range.
26. An apparatus for controlling an operating range, comprising:
means for receiving a digital signal;
means for determining whether the digital signal corresponds to a designated operating range; and
means for adjusting an operating range of a voltage-controlled oscillator if the digital signal does not correspond to the designated operating range.
27. The apparatus of claim 26 , wherein the designated operating range corresponds to a high-resolution operating region of a digital-to-analog converter.
28. The apparatus of claim 26 , wherein the means for adjusting comprises:
means for determining a first adjustment based on the digital signal; and
means for applying the first adjustment to the voltage-controlled oscillator.
29. The apparatus of claim 28 , wherein the means for adjusting further comprises:
means for determining whether an updated digital signal corresponds to the designated operating range;
means for determining a scaled second adjustment based on the first adjustment if the updated digital signal does not correspond to the designated operating range; and
means for applying the scaled second adjustment to the voltage-controlled oscillator if the updated digital signal does not correspond to the designated operating range.