Coded data generation or conversion – Analog to or from digital conversion – Differential encoder and/or decoder
Reexamination Certificate
1999-02-18
2001-12-11
JeanPierre, Peguy (Department: 2819)
Coded data generation or conversion
Analog to or from digital conversion
Differential encoder and/or decoder
C341S155000, C327S058000, C333S173000
Reexamination Certificate
active
06329939
ABSTRACT:
FIELD OF INVENTION
The present invention relates to minimizing mismatch in a complex filter, and more specifically to minimizing mismatch in a complex feedforward loop filter in a complex sigma-delta modulator.
BACKGROUND OF THE INVENTION
Digital processing of signals is usually more cost effective and provides higher performance than analog processing. Analog to digital (A/D) converters, therefore, are used in many systems. Many modern radio systems, for example, use digital signal processing techniques to achieve higher performance, and as such, require high performance analog to digital converters.
There are a number of different analog to digital (A/D) converters known in the art, such as flash A/D, successive approximation, pulse code modulation (PCM) conversion, oversampled PCM conversion, and sigma-delta modulation A/D conversion. Generally speaking, the best performance is achieved by sigma-delta modulation techniques.
Sigma-delta modulation A/D conversion achieves higher resolution than many of the other techniques. In essence, sigma-delta modulation improves the resolution by increasing the signal to noise ration (SNR) in the A/D converter, which results in increased resolution. The SNR increases due to oversampling, which spreads the noise over a large bandwidth, and due to a complex feedforward loop filter, which further reduces the noise in the band of interest by forcing some of the inband noise out of band. The extra performance of sigma-delta modulation A/D converters is obtained at the expense of high circuit speeds as compared to other A/D converters. This being the case, however, by using a complex transfer function for the complex feedforward loop filter the circuit speed requirements are less as compared to using a real transfer function. A complex sigma-delta modulation A/D converter uses such a complex filter.
Typical complex sigma-delta modulation A/D converter performance has been limited by mismatches in the circuit technology. In complex sigma-delta modulation A/D converters there are effectively two separate channels for the real and imaginary inputs to the complex feedforward loop filter. Any mismatch between the two channels causes the signals at the negative frequencies to ‘fold’ into the desired signal band, which degrades performance. Therefore, and image frequency can be aliased on top of the desired signal.
Therefore, in order to exploit the high resolution and moderate circuit speed achieved by complex sigma-delta modulation A/D converters, a method and apparatus for minimizing the mismatch in the complex feedforward loop filter is needed.
SUMMARY OF THE INVENTION
The invention is directed to a method and apparatus for minimizing the mismatch in a complex filter.
An advantage of the invention is minimized mismatch error caused by imperfections in the complex filter, thereby enhancing the performance of the complex filter.
According to the invention, there is provided a complex filtering method in a complex filter having at least two stages and at least one mismatch error after the first stage. The method includes the step of averaging the mismatch error by integrating a real input signal and an imaginary input signal using a single integrator.
Another embodiment of the invention is a complex filter including means for implementing a transfer function substantially equal to
1
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1
1
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-
1
.
REFERENCES:
patent: 3881100 (1975-04-01), Works et al.
patent: 4067014 (1978-01-01), Wheeler et al.
patent: 4835482 (1989-05-01), Tamakoshi et al.
patent: 5134401 (1992-07-01), Mccarteny et al.
patent: 5140325 (1992-08-01), Tsai-Chung et al.
patent: 5148166 (1992-09-01), Ribner
patent: 5162799 (1992-11-01), Tanimoto
patent: 5233551 (1993-08-01), White
patent: 5283578 (1994-02-01), Ribner
patent: 5311370 (1994-05-01), Takayama
patent: 5381357 (1995-01-01), Wedgwood et al.
patent: 5392043 (1995-02-01), Ribner
patent: 5442353 (1995-08-01), Jackson
patent: 5444414 (1995-08-01), Delano
patent: 5451901 (1995-09-01), Welland
patent: 5574452 (1996-11-01), Longo et al.
patent: 5608400 (1997-03-01), Pellon
patent: 5844442 (1998-12-01), Brehmer
patent: 6225928 (2001-05-01), Green
An Overview of Sigma-Delta Converters from theIEEE Signal Processing Magazine; Pervez M. Aziz, et al.; Jan. 1996; pp. 61-84.
Complex Bandpass &Dgr;&Sgr; Converter for Digital Radio; J. Jantzi, et al.; University of Toronto and Carleton University; pp. 453-456.
Performance of Complex Noise Transfer Functions In Bandwidth and Multi Band Sigma Systems from theIEEE; Pervez M. Aziz, et al.; Dept. of Electrical Engineering, Univ. of PA; 1995; pp. 641-644.
The Effects of Mismatch in Complex Bandpass Modulators; S. A. Jantzi, et al.; The University of Toronto, Dept. of Electrical and Computer Eng.; 1996; pp. 227-230.
Complex-signal sigma-delta modulators for quadrature bandpass A/D conversion from theMicroelectronics Journal27; Victor da Fonte Dias; 1996; pp. 505-524.
Fenk et al., “Low-noise, low-voltage, low-power IF gain controlled amplifiers for wireless communication,” Siemens AG, 1996, pp. 27-45.
Crols et al., “Low-IF Topologies for High-Performance Analog Front Ends of Fully Integrated Receivers, ” IEEE Trans. on Circuits and Systems II-Analog and Digital Signal Processing, vol. 45, No. 3, Mar. 1998, pp. 269-282.
Crawley et al., “Designing Operational Transconductance Amplifiers for Low Voltage Operation, ” IEEE International Symposium on Circuits and Systems, May 1993, pp. 1455-1458.
MacRobbie Edward William
Snelgrove William Martin
Swaminathan Ashok
Jean-Pierre Peguy
Jeanglaude Jean B.
Philsar Semiconductor Inc.
Thomas Kayden Horstemeyer & Risley, L.L.P.
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