Multi-mode analog-to-digital converter
Techniques and devices provide analog-to-digital conversion at two or more signal frequencies or frequency bands and can be used to construct multi-mode analog-to-digital converters in various circuits, including receivers and transceivers for wireless communications and radio broadcast environments. Adjustable analog-to-digital converters based on the described techniques can be configured to adjust circuit parameters to adapt the technical specifications of different input signals at different signal frequencies or frequency bands, such as FM, HD-radio, and DAB radio signals in radio receiver applications.
1. An analog-to-digital converter comprising:
an adjustable resonator circuit having an integrator, said integrator producing an integrated analog signal based on an analog input signal;
a quantizer coupled to receive said integrated analog signal and producing a digital output based on said integrated analog signal;
a dither generator producing a random digital voltage output based on a digital data input at a rate determined by a rate of an input clock;
a digital-to-analog converter operable to produce a random current to said integrator based on said random digital voltage output.
2. The analog-to-digital converter of claim 1 , wherein said digital-to-analog converter converts said digital output of said quantizer into a first analog feedback current coupled to an input port of said integrator.
3. The analog-to-digital converter of claim 1 , wherein said integrator includes an operational amplifier having a capacitive feedback loop to form an operational amplifier integrator.
4. The analog-to-digital converter of claim 3 , further comprising a resistor coupled in said capacitive feedback loop of said operational amplifier.
5. The analog-to-digital converter of claim 3 , wherein said integrator includes an input operational amplifier receiving said analog input signal and producing an output to said operational amplifier integrator, said input operational amplifier having a capacitive feedback loop to form an input operational amplifier integrator.
6. The analog-to-digital converter of claim 5 , wherein said analog-to-digital converter includes another feedback loop that includes a second digital-to-analog converter converting said digital output of said quantizer into a second analog feedback current coupled to an input port of said input operational amplifier.
7. The analog-to-digital converter of claim 1 , wherein said dither generator is programmable to produce different random digital voltage outputs in response to different signal frequencies of said analog input signal.
8. The analog-to-digital converter of claim 1 , wherein said integrator includes one or more circuit components adjustable in response to different signal frequencies of said analog input signal.
9. The analog-to-digital converter of claim 1 , wherein a data rate of said digital data input is less than said rate of said input clock.
10. The analog-to-digital converter of claim 1 , further comprising an adjustable input resistor coupled to an input port of said integrator to adjust a signal gain of said integrator.
11. The analog-to-digital converter of claim 1 , wherein said integrator includes an adjustable resistor coupled between an input port and an output port of said integrator to change a frequency of a response of said analog-to-digital converter.
12. The analog-to-digital converter of claim 1 , further comprising a digital signal processing block coupled to receive a digital signal produced based on said digital output of said quantizer and configured to perform digital signal filtering on said digital signal.
13. An integrated circuit radio receiver comprising:
receiver circuitry receiving an input signal based on one of a plurality of different radio broadcast standards;
an analog-to-digital converter comprising:
an adjustable circuit having a first integrator producing an integrated analog signal based on an intermediate frequency (IF) analog signal produced by said receiver circuitry,
a quantizer producing a digital output based on said integrated analog signal;
a control circuit operable to control at least one adjustable circuit component of said adjustable circuit to adapt operation of said analog-to-digital converter to said input signal.
14. The integrated circuit radio receiver of claim 13 , wherein said control circuit controls said at least one adjustable circuit component to shift a frequency of a notch of a noise transfer function of said analog-to-digital converter to overlap with a frequency band of said intermediate frequency (IF) analog signal.
15. The integrated circuit radio receiver of claim 13 , wherein said adjustable circuit includes an adjustable resistor controlled by said control circuit to shift a frequency of a notch of a noise transfer function of said analog-to-digital converter.
16. The integrated circuit radio receiver of claim 13 , wherein said analog-to-digital converter includes a dither generator coupled to said control circuit, said dither generator comprising:
a digital dither generator producing a random digital voltage output based on a digital data input at a rate determined by a rate of an input clock, wherein a data rate of said digital data input is less than said rate of said input clock.
17. The integrated circuit radio receiver of claim 13 , wherein said adjustable circuit includes a second integrator coupled between said first integrator and said quantizer.
18. The integrated circuit radio receiver of claim 13 , wherein said analog-to-digital converter includes an adjustable input resistor coupled to said first integrator and controlled by said control circuit to adjust a gain of said analog-to-digital converter.
19. A method for operating a radio receiver, the method comprising:
identifying a radio mode in said radio receiver based on an indication signal received by an adjustable analog-to-digital converter, said adjustable analog-to-digital converter comprising an adjustable resonator circuit;
retrieving at least one value of at least one corresponding adjustable circuit component in said adjustable analog-to-digital converter;
adjusting said at least one corresponding adjustable circuit component to said at least one value to carry out an analog-to-digital converter operation at a frequency of said indication signal.
20. The method of claim 19 further comprising programming a dither generation block based on said indication signal to produce a corresponding digital dither signal configured for said radio mode.