Four-order sigma-delta modulator

Details Four-order sigma-delta modulator Four-order sigma-delta modulator

2002-06-11

2003-07-01

Young, Brian (Department: 2819)

Coded data generation or conversion

Analog to or from digital conversion

Differential encoder and/or decoder

C341S144000, C341S155000

Reexamination Certificate

active

06587063

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention:
The invention relates to an four-order sigma-delta modulator, which implements a feedback and a feedforward configuration, so that the desired noise transfer function is carried out by adjusting the coefficients of the feedback and the feedforward.
2. Description of the Related Art:
With proper design, the sigma-delta modulator can have the advantages of high resolution, simple circuit, no additional trimming circuit and high tolerance for device replacement. As is well-known in sigma-delta modulators, SNR is dependent on the oversampling ratio, the sigma-delta modulator order and quantizer resolution. Theoretically, doubling the oversampling ratio should result in a 3 dB improvement in SNR, and increasing the order of the sigma-delta modulator by one should produce another 6 dB improvement in SNR within the desired bandwidth. A 1-bit (two value) increase in quantizer resolution should yield another 6 dB. Therefore, such a sigma-delta modulator is widely applied in situations requiring higher SNR. As well, digital communication has been growing rapidly during the past few years. For development of digital communication, a three order or more sigma-delta modulator has become a popular design area.
As shown in
FIG. 1
, a typical high-order sigma-delta modulator feeds back the digital signal Y from an A/D quantizer
108
to the input terminals respectively to the integrators
102
,
104
and
106
through a D/A converter
110
, so as to form a desired three-order or more noise transfer function. Such a structure can have different noise transfer functions by adjusting the integrator's output coefficients. However, the feedback configuration in the sigma-delta modulator will cause overload and introduce a complicated circuit when implementing the desired noise transfer function, even though it can have higher resolution and higher SNR with higher orders.
SUMMARY OF THE INVENTION
Accordingly, an object of the invention is to provide a four-order sigma-delta modulator, which implements a feedback and a feedforward configuration, so that the desired noise transfer function is carried out by adjusting the coefficients of the feedback and the feedforward.
To realize the above object, the invention provides a four-order sigma-delta modulator comprising: an analog-to-digital converter, to output a digital modulation signal; a digital-to-analog converter, to convert the digital modulation signal into an analog signal and generate a feedback signal; a first integrating network, to receive an external input signal and the feedback signal and generate a first output signal; a second integrating network, connected in series with the first integrating network, to receive the first output signal and a feedback gain signal with a first feedback gain factor, generated by gaining the feedback signal by the first feedback gain factor, and generate a second output signal; a third integrating network, connected in series with the second integrating network, to receive the second output signal and generate a third output signal; a fourth integrating network, connected in series with the third integrating network, to receive the third output signal and a feedback gain signal with a second feedback gain factor, generated by gaining the feedback signal by the second feedback gain factor, and generate a fourth output signal; and an adder, combining a feedforward output signal with a feedforward gain factor, generated by gaining the second output signal by the feedforward gain factor, and a modulation output signal with a modulation gain factor, generated by gaining the fourth output signal by the modulation gain factor, to generate a desired noise transfer function, and outputting a noise transfer signal to the digital-to-analog converter.


REFERENCES:
patent: 5623263 (1997-04-01), Kuo et al.
patent: 5673044 (1997-09-01), Pellon
patent: 5682160 (1997-10-01), Ribner et al.
patent: 5859603 (1999-01-01), Noguchi et al.
patent: 6057793 (2000-05-01), Gong et al.

Affiliated with

Also associated with

Rating

Four-order sigma-delta modulator does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Four-order sigma-delta modulator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Four-order sigma-delta modulator will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3046916