Class-B biased gilbert cells and quadrature modulators

Details Class-B biased gilbert cells and quadrature modulators Class-B biased gilbert cells and quadrature modulators

2000-06-22

2004-07-27

Mis, David (Department: 2817)

Modulators

Miscellaneous

C332S103000, C332S149000, C327S359000, C375S295000, C375S298000, C455S333000

Reexamination Certificate

active

06768391

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to modulator or mixer circuits and related methods, and more particularly to Gilbert cell modulators and related methods.
Modulation systems and methods are widely used in transmitters to modulate information including voice and/or data onto a carrier. The carrier may be a final carrier or an intermediate carrier. The carrier frequency can be in UHF, VHF, RF, microwave or any other frequency band. Modulators are also referred to as “mixers” or “multipliers”. For example, in a mobile terminal, a modulator may be used in the transmitter thereof, to modulate an input signal (voice and/or data) for wireless transmission.
A particular type of modulator which is widely used is the “Gilbert Multiplier Cell” also referred to as the “Gilbert modulator”, the “Gilbert cell” or the “Gilbert mixer”. The Gilbert Multiplier Cell includes an emitter coupled transistor pair, also referred to as the “lower transistors” or “driver transistors”, which is coupled to a pair of cross-coupled emitter-coupled transistor pairs, also referred to as the “upper transistors”, “switch transistors” or “active mixer transistors”. One set of cross-coupled, emitter-coupled transistor pairs of the upper transistors and one of the lower transistors also is referred to as a “long-tailed pair”. A data input, which can include an analog or digital voice and/or data input, is coupled to the emitter-coupled transistor pair. A local oscillator is coupled to the pair of cross-coupled, emitter-coupled transistor pairs, to produce a modulated output.
Gilbert Multiplier Cells are described in U.S. Pat. No. 4,156,283 to Gilbert entitled
Multiplier Circuit
. The Gilbert Multiplier Cell also is extensively described and analyzed in Section 10.3 of the textbook
Analysis and Design of Analog Integrated Circuits
by Paul Gray and Robert Meyer, John Wiley and Sons, NY, 1993, pp. 670-675, the disclosure of which is incorporated herein by reference.
A pair of Gilbert Multiplier Cells may be used to produce a quadraphase modulator, also known as an “IC/IQ modulator”, an “I/Q quadrature modulator” or a “quadrature modulator”. Quadraphase modulators are described in U.S. Pat. No. 5,574,755, to Persico entitled
I/Q Quadraphase Modulator Circuit
, U.S. Pat. No. 5,530,722 to coinventor Dent, entitled
Quadrature Modulator With Integrated Distributed-RC Filters
and U.S. Pat. No. 5,847,623 to coinventor Hadjichristos entitled
Low Noise Gilbert Multiplier Cells and Quadrature Modulators
, the disclosures all of which are hereby incorporated herein by reference in their entirety.
SUMMARY OF THE INVENTION
Embodiments of the present invention can provide quadrature modulators that comprise a quadrature splitter and a pair of Gilbert Multiplier Cells coupled to the quadrature splitter that are biased in Class-B. As is well known to those having skill in the art, a Class-B circuit is biased at zero DC current so that a transistor in a Class-B stage conducts for only half of the cycle of an input sine wave. In contrast, a Class-A circuit is biased at a current that is greater than the amplitude of the signal current, so that a transistor in Class-A conducts for the entire cycle of the input signal. The quiescent current bias in the Gilbert Multiplier Cells may be substantially zero. Accordingly, reduced power consumption may be provided.
Each of the Gilbert Multiplier Cells may comprise a pair of cross-coupled, emitter-coupled transistor pairs and a driver circuit that is coupled to at least one of the emitter-coupled transistor pairs and that is biased in Class-B. The driver circuit may include at least one current mirror circuit that is coupled to at least one of the emitter-coupled transistor pairs. The driver circuit also may comprise at least one current source that selectively applies current to at least one of the emitter-coupled transistor pairs, more specifically by selectively applying current to the at least one current mirror circuit. Accordingly, the Gilbert Multiplier Cell is biased in Class-B.


REFERENCES:
patent: 4156283 (1979-05-01), Gilbert
patent: 5495194 (1996-02-01), Sugawara
patent: 5530722 (1996-06-01), Dent
patent: 5574755 (1996-11-01), Persico
patent: 5805987 (1998-09-01), Kamase
patent: 5847623 (1998-12-01), Hadjichristos
patent: 5920810 (1999-07-01), Finol et al.
patent: 6037825 (2000-03-01), Kung
patent: 0 073 929 (1983-03-01), None
patent: 2 291 753 (1996-01-01), None
patent: WO 96/08865 (1996-03-01), None
Gray et al.,Analysis and Design of Analog Integrated Circuit, Third Edition, John Wiley & Sons, Inc., 1993, pp. 670-675.
TIA/EIA-136-133-A Draft Text,Digital Traffic Channel Layer 3, Aug. 31, 1999.
TIA/EIA-136-131-A Draft Text,Digital Traffic Channel Layer 1, Aug. 31, 1999.
TIA/EIA-136-000-A Draft Text,List of Parts, Aug. 31, 1999.
International Search Report, PCT/US01/18077, Oct. 29, 2002.

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