Pulse or digital communications – Receivers – Angle modulation
Reexamination Certificate
1998-10-02
2003-08-26
Pham, Chi (Department: 2631)
Pulse or digital communications
Receivers
Angle modulation
C455S339000
Reexamination Certificate
active
06611569
ABSTRACT:
This application claims priority under 35 U.S.C. §§119 and/or 365 to 9703617-2 filed in Sweden on Oct. 3, 1997; the entire content of which is hereby incorporated by reference.
TECHNICAL FIELD
The present invention relates to a down/up-converter and a down/up-conversion method for high/low frequency signals.
BACKGROUND OF THE INVENTION
Down- and up-conversion is used in, for example, single sideband demodulators and modulators. A common technique (see [1]) for demodulation involves a mixer, which multiplies the incoming signal with two 90° phase-shifted sinusoidal signals, and a Hilbert filter for one of the resulting components (in-phase or quadrature component). The output signal from the Hilbert filter is then added or subtracted to or from the other component, depending on whether the lower or upper sideband is desired. Modulation is performed by using the same elements in the reverse order.
A drawback of this technique is that it is very difficult to design a lowpass Hilbert filter both in analog and digital form. Furthermore, in practice it may be difficult to perform the down-conversion to or up-conversion from baseband in one step (for example, cellular telephony systems often operate with carrier frequencies of the order of 1 GHz).
SUMMARY OF THE INVENTION
An object of the present invention is to provide an apparatus and method that avoids Hilbert filters.
Another object is to perform the down- or up-conversion in several mixing steps.
These objects are achieved with an apparatus and method in accordance with the appended claims.
Briefly, the present invention is based on the insight that complex filters automatically provide a 90° phase-shift between real and imaginary components of a complex signal. This feature, when combined with a second mixer, may be used to eliminate the undesirable Hilbert filter of the prior art. At the same time a two step conversion involving two mixers is obtained.
REFERENCES:
patent: 3949309 (1976-04-01), Pecar
patent: 4458216 (1984-07-01), Bingham
patent: 4710814 (1987-12-01), Gassmann et al.
patent: 4736390 (1988-04-01), Ward et al.
patent: 4803700 (1989-02-01), Dewey et al.
patent: 5473280 (1995-12-01), Ohnishi et al.
patent: 5517529 (1996-05-01), Stehlik
patent: 5749051 (1998-05-01), Dent
patent: 5786782 (1998-07-01), Ostman et al.
patent: 5821782 (1998-10-01), Carloni et al.
patent: 5825242 (1998-10-01), Prodan et al.
patent: 5903609 (1999-05-01), Kool et al.
patent: 5956620 (1999-09-01), Lazaris-Brunner et al.
patent: 6035186 (2000-03-01), Moore et al.
patent: 6215828 (2001-04-01), Signell et al.
patent: 6275540 (2001-08-01), Barrett et al.
patent: 0 502 449 (1992-09-01), None
patent: 2 176 356 (1986-12-01), None
patent: 98/11672 (1998-03-01), None
Jantzi, S.; Martin, K.; Snelgrove, M.; Sedra, A.; “A Complex Bandpass Delta-Sigma Converter for Digital Radio”, 1994 IEEE International Symposium, vol.: 5, May 30-Jun. 2, 1994; pp. 453-456 vol. 5.*
Hambley, Allan R., “An Introduction to Communication Systems”,Computer Science Press, pp82&103.
Signell, Svante, et al., “Design and Analysis of Bilinear Digital Ladder Filters”,IEEE Transactions on Circuits and Systems, pp1-13.
Bracewell, Ronald N., “The Fourier Transform and its Applications”McGraw-Hill Book Company, pp107&267.
Schier Thorsten
Signell Svante
Pham Chi
Telefonaktiebolaget LM Ericsson (publ)
Tran Khanh Cong
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