Non-return-to-zero DAC using reference sine wave signals

Details Non-return-to-zero DAC using reference sine wave signals Non-return-to-zero DAC using reference sine wave signals

2001-04-03

2002-10-15

Tokar, Michael (Department: 2819)

Coded data generation or conversion

Digital code to digital code converters

To or from nrz codes

C341S143000

Reexamination Certificate

active

06466143

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a high resolution, high order delta signal digital-to-analog converter. Specifically, a feed forward DAC is disclosed for converting a digital signal to a low noise analog signal which minimizes the effects of clock jitter on the noise floor of the analog signal.
Radio frequency communications systems such as cellular telephone systems employ significant amounts of digital processing to both transmit and receive signals. On the transmit side, information is processed on a digital level and only at the final radio frequency carrier level is the signal converted to an analog signal. The analog signal is then mixed with an RF carrier of the cellular telephone system for transmission.
The digital data processed below the radio frequency signal band is upwards to 16 bits wide. The high resolution digital signal may then be converted to a lower order bit signal using a digital signal modulator. However, it is desirable to maintain the same signal-to-noise ratio so that the reconverted signal on the receive side maintains the same resolution as the original digital signal.
The process of converting the digital signal to an analog signal introduces noise in the signal thereby limiting the resolution of the converted signal. The noise is strongly affected by the amount of phase jitter in the data being converted by the digital analog converter. Phase jitter on the incoming digital data to the DAC is the result of the phase jitter on the system clock which affects the digital data bit transitions producing the phase noise modulation. The phase noise modulation contributes to the noise floor of the resulting analog signal limiting the ability to obtain a high resolution of the analog signal level.
The present invention is directed to a DAC which maintains the high resolution of an incoming digital signal which is converted into an analog signal.
SUMMARY OF THE INVENTION
In carrying out the invention, a non return to zero (NRZ) SIN digital-to-analog converter (DAC) is provided for converting a digital input signal to an analog signal. The NRZ SIN digital-to-analog converter provides an sine wave output in response to a first state of a digital signal proportional to 1+COS 2&pgr;f(t), and in response to a second state of the digital signal, a sine wave signal proportional to −1−COS 2&pgr;f(t).
A second SIN digital to analog converter receives a delayed version of the digital signal. The output of the second SIN digital converter is phase shifted with respect to the output of the first sign digital converter, and the respective output signals are combined to produce a non-return to zero (NRZ) output voltage. The NRZ output voltage contains less high frequency content than produced by a return to zero (RZ) SIN DAC, and the only significant phase noise which results from phase jitter occurs during data transitions.


REFERENCES:
patent: 4975699 (1990-12-01), Frey
patent: 4983972 (1991-01-01), Mills
patent: 5056118 (1991-10-01), Sun
patent: 5528239 (1996-06-01), Swanson et al.
patent: 5557635 (1996-09-01), Laird
patent: 5610606 (1997-03-01), Fukunaga et al.
patent: 5701106 (1997-12-01), Pikkarainen et al.
patent: 6114981 (2000-09-01), Nagata
patent: 6121910 (2000-09-01), Khoury et al.
patent: 6324236 (2001-11-01), Bladh
Flikkema, Paul G., and Davisson, Lee D., Detection of Baseband Signals Using a Delta Modulator, May 1988,IEEE Transactions on Information Theory, vol. 34, No. 3, pp 537-543.
Flikkema, Paul G.; Davisson, Lee D. “Detection of Baseband Signals Using a Delta Modulator”, IEEE Transactions on Information Theory, vol. 335, No. 3, May 1988, pp. 537-543.
W. Gao and W.M. Snelgrove, “A 950-MHz IF Second-Order Integrated LC Bandpass Delta-Sigma Modulator,” May 1998,IEEE Journal of Solid-State Circuits, vol. 33, No. 5.
O. Shoaei and W.M. Snelgrove, “Design and Implementatioin of a Tunable 40 MHz-70 MHz Gm-C Bandpass &Dgr;&Egr;Modulator,” Jul. 1997,IEEE Transactions on Circuits and Systems-II: Analog and Digital Signal Processing, vol. 44, No. 7.

Affiliated with

Also associated with

Rating

Non-return-to-zero DAC using reference sine wave signals does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Non-return-to-zero DAC using reference sine wave signals, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-return-to-zero DAC using reference sine wave signals will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2997511