Pulse or digital communications – Synchronizers – Synchronizing the sampling time of digital data
Reexamination Certificate
1997-10-08
2001-04-17
Pham, Chi (Department: 2631)
Pulse or digital communications
Synchronizers
Synchronizing the sampling time of digital data
C327S045000
Reexamination Certificate
active
06219394
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to digital frequency discrimination.
2. State of the Art
Frequency discrimination is important in digital radio communications, in particular in any digital FM radio receiver. Frequency discrimination is typically performed using analog circuitry, e.g. an IQ frequency discriminator. Analog frequency discriminators have substantial drawbacks. In the case of an IQ frequency discriminator, the discriminator requires a number of analog components, two A/D conversions and a numerical arctangent operation, rendering the circuit quite complex.
Known methods exist for producing a value representing the instantaneous frequency of a signal using only digital logic elements. Various such methods are described in U.S. Pat. No. 5,084,669, incorporated herein by reference. In particular, the foregoing patent describes a digital circuit for determining the instantaneous phase of a signal, from which the instantaneous frequency may be obtained if desired. Although the implementation of the circuit is all digital, it is quite involved. An improved method and apparatus for determining in a simple, all-digital manner the instantaneous frequency of a signal would therefore likely be well-received by those skilled in the art.
SUMMARY OF THE INVENTION
The present invention, generally speaking, provides a very simple, all-digital method and apparatus for determining the ratio of frequencies of two signals. One of the signals may be a known reference frequency, allowing the instantaneous frequency of an unknown input signal to be readily determined. A frequency sampling technique is employed that produces a stream of digital bits which contains information regarding the ratio of frequencies. From the stream of digital bits is formed a digital word indicative of the ratio of frequencies. The digital word may be formed using a digital filter. Advantageously, an extensive body of digital filtering techniques applicable to Sigma-Delta (sometimes referred to as Delta-Sigma) A/D converters may be applied directly to the digital stream. By using an appropriately-chosen weighting function, high accuracy may be obtained.
REFERENCES:
patent: 4468794 (1984-08-01), Waters et al.
patent: 4527145 (1985-07-01), Haussmann et al.
patent: 4764923 (1988-08-01), Forth et al.
patent: 5398007 (1995-03-01), Ymazaki et al.
patent: 5398029 (1995-03-01), Toyama et al.
patent: 5513209 (1996-04-01), Holm
patent: 5557647 (1996-09-01), Kushige et al.
patent: 5615235 (1997-03-01), Kakuishi et al.
patent: 5664165 (1997-09-01), Curry et al.
patent: 5796995 (1998-08-01), Nasserbakht et al.
Hovin et al., “Delta-Sigma Modulators Using Frequency-Modulated Intermediate Values”,IEEE Journal of Solid-State Circuiuts,32:1, pp. 13-22 (1997).
Hovin et al., “A Narrow-Band Delta-Sigma Frequency-to-Digital Converter”, IEEE International Symposium on circuits and Systems, pp. 77-80 (1997).
Hovin et al., “Novel second-order &Dgr;-&Sgr; modulator/frequency-to-digital converter”,Electronics Letters,31:2, pp. 81-82 (1995).
Corrielus Jean B
Pham Chi
Tropian Inc.
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