SIGNAL PROCESSING SYSTEM USING DELTA-SIGMA MODULATION HAVING AN INTERNAL STABILIZER PATH WITH DIRECT OUTPUT-TO-INTEGRATOR CONNECTION
First Claim
1. A signal processing system comprising an analog-to-digital converter, the analog-to-digital converter comprising:
- a main loop filter having a transfer function HMAIN, the main loop filter comprising;
a signal input to receive an input signal;
a quantizer;
a first digital-to-analog converter coupled to the quantizer, the first digital-to-analog converter comprising a duty cycle modulator;
a finite impulse response filter coupled to the first digital-to-analog converter;
a first integrator coupled to the signal input, to an output of the finite impulse response filter, and to an input of the quantizer;
a second integrator coupled between the first integrator and the quantizer; and
a stabilizer loop having a transfer function HST, wherein the stabilizer loop includes a stabilizer path and the stabilizer path includes (i) an input coupled to an output of the quantizer and (ii) an output connected directly to an input of the second integrator;
wherein a target transfer function of the analog-to-digital converter is HT, and HT comprises a combination of HMAIN and HST.
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Abstract
A signal processing system includes an analog-to-digital delta sigma modulator with a duty cycle modulator and a finite impulse response (FIR) filter in a main loop feedback path of the delta sigma modulator. The duty cycle modulator and FIR filter can provide high performance filtering in the main loop feedback path. To prevent instability in the main loop caused by the duty cycle modulator and FIR filter, the delta sigma modulator also includes a stabilizer loop. Transfer functions of the main loop and the stabilizer loop combine to achieve a target transfer function for the analog-to-digital delta sigma modulator that provides for stable operation of the analog-to-digital delta sigma modulator. In at least one embodiment, the stabilizer loop includes a stabilizer path that provides output data directly to an integrator of the main loop filter.
54 Citations
22 Claims
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1. A signal processing system comprising an analog-to-digital converter, the analog-to-digital converter comprising:
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a main loop filter having a transfer function HMAIN, the main loop filter comprising; a signal input to receive an input signal; a quantizer; a first digital-to-analog converter coupled to the quantizer, the first digital-to-analog converter comprising a duty cycle modulator; a finite impulse response filter coupled to the first digital-to-analog converter; a first integrator coupled to the signal input, to an output of the finite impulse response filter, and to an input of the quantizer; a second integrator coupled between the first integrator and the quantizer; and a stabilizer loop having a transfer function HST, wherein the stabilizer loop includes a stabilizer path and the stabilizer path includes (i) an input coupled to an output of the quantizer and (ii) an output connected directly to an input of the second integrator; wherein a target transfer function of the analog-to-digital converter is HT, and HT comprises a combination of HMAIN and HST. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A signal processing system comprising an analog-to-digital converter having a target transfer function of HT, the analog-to-digital converter comprising:
a delta sigma modulator comprising; a quantizer to generate quantizer output data; a main loop filter to process input data and quantization feedback data in accordance with a transfer function Hmain, wherein the main loop filter comprises components for; receiving the input data; generating the quantization feedback data from the quantizer output data using (i) pulse width modulation to generate pulse width modulated output data and (ii) finite impulse response filtering of the pulse width modulated output data; combining the input signal with the quantization feedback data to generate an input_feedback signal; and processing the input_feedback signal using at least one integrator; an integrator coupled to the quantizer; and a stabilizer loop having a transfer function HST, wherein the stabilizer loop includes a stabilizer path, connected to the integrator, to process the quantizer output data and the stabilizer path comprises components to; receive the quantizer output data to generate stabilizer path output data; and supply the stabilizer path output data directly to the integrator; wherein the target transfer function HT comprises a combination of transfer functions HMAIN and HST. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A method for converting an analog input signal into a digital output signal, the method comprising:
converting the analog input signal into the digital output signal using a delta sigma modulator having a target transfer function HT, wherein the delta sigma modulator includes a main loop having a transfer function HMAIN and a stabilizer loop having a transfer function HST, and the target transfer function HT comprises a combination of transfer functions HMAIN and HST;
wherein converting the analog input signal comprises;determining a first signal from the analog input signal using the main loop of a delta sigma modulator, wherein the main loop includes (i) a quantizer feedback path comprising a duty cycle modulator coupled to a first finite impulse response filter and (ii) a signal path comprising an integrator; determining a stabilizer signal using the stabilizer loop of the delta sigma modulator, wherein the stabilizer loop includes a stabilizer path coupled across a quantizer of the delta sigma modulator and the stabilizer path includes a digital-to-analog converter and an output connected directly to the integrator of the main loop; generating a quantizer input signal from the first signal and the stabilizer signal; and quantizing the quantizer input signal. - View Dependent Claims (18)
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19. A method for converting an analog signal into a digital signal, the method comprising:
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receiving an input signal; processing the input signal using delta sigma modulation in accordance with a target transfer function HT, wherein the target transfer function HT is a function of a main loop transfer function HMAIN and a stabilizer loop transfer function HST, wherein processing the input signal using delta sigma modulation in accordance with the target transfer function HT further comprises; in a main loop of the delta sigma modulator; generating quantization feedback data from quantizer output data, wherein generating quantization feedback data from quantizer output data comprises; duty cycle modulating quantizer output data to generate pulse width modulated output data; and filtering the pulse width modulated output data with a finite impulse response filter; combining the input signal with the quantization feedback data to generate an input_feedback signal; and processing the input_feedback signal using at least one integrator to generate a main loop output signal; in a stabilizer loop of the delta sigma modulator; processing the quantizer output data to generate a stabilizer path output signal using a digital-to-analog converter; and supplying the stabilizer path output signal directly to an integrator of the main loop; and combining the main loop output signal and the stabilizer path output signal to generate a main loop_stabilizer signal; and generating a quantization output signal using the main loop_stabilizer signal. - View Dependent Claims (20, 21, 22)
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Specification