Telecommunications – Receiver or analog modulated signal frequency converter – Frequency modifying or conversion
Reexamination Certificate
1999-05-27
2001-05-08
To, Doris H. (Department: 2682)
Telecommunications
Receiver or analog modulated signal frequency converter
Frequency modifying or conversion
C455S333000, C327S357000, C332S178000
Reexamination Certificate
active
06230001
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to radio communications equipment and more specifically to radio frequency (RF) mixers used in RF equipment.
Radio communications equipment use mixers to convert a signal from a low frequency to a high frequency or a high frequency to a low frequency by mixing the signal with a local oscillator signal. The local oscillator frequency can be above or below the frequency of the desire signal to produce a sum and a difference frequency one of which is the frequency of interest.
Mixer performance is critical to the overall performance of the RF equipment. Mixer performance is especially critical in receiver applications where the dynamic range of the receiver is limited by the mixer. Mixers must have good linearity or intermodulation performance characteristics, wide dynamic range, low power consumption, low noise figure, and offer conversion gain in some applications.
Direct conversion or homodyne receivers convert the RF signal directly to baseband or a zero intermediate frequency (IF). Mixers for this application require low second or even-order distortion products, good balance, and low 1/f noise. Diode ring mixers are not suitable for direct conversion receiver applications since they have poor balance, require high injection levels, and have a conversion loss. Active mixers such as the Gilbert cell fabricated in gallium arsenide (GaAs) heterojunction bipolar transistor (HBT) technology offer some performance advantages over passive diode mixers. However these active mixer designs are expensive and suffer from 1/f noise problems and other low frequency discrete noise spurs due to GaAs processing issues. These mixers also have high power consumption and larger than desired noise figures.
What is needed for direct conversion and other receiver applications is a mixer that has no anomalous low frequency spurs, has low distortion, has significantly reduced power consumption, lower noise figure, good balance, and low cost.
SUMMARY OF THE INVENTION
An active commutated double balanced mixer is disclosed. The active commutated double balanced mixer comprises a transformer with a primary connected to an RF input signal to be up or down converted and a secondary with a center tap connected to ground. A first resistor is used with a first end connected to a first end terminal of the transformer secondary. A second resistor is used with a first end connected to a second end terminal of the transformer secondary. A quad transistor core is connected to a second end of the first resistor and a 180 degree out of phase RF input connected to a second end of the second resistor, a local oscillator input, a power supply input, and an intermediate frequency output.
It is an object of the present invention to provide a mixer that has low intermodulation distortion, reduced power consumption, good balance, and good amplitude modulation (AM) demodulation performance.
It is an advantage of the present invention that bipolar junction transistor and field effect transistor technology can be used.
It is an advantage of the present invention that silicon bipolar junction transistor technology is utilized to lower cost.
It is another advantage of the present invention using silicon bipolar junction transistor technology that spurious low frequency noise is reduced.
It is a feature of the present invention to provide the performance needed for direct conversion receiver applications.
REFERENCES:
patent: 4268916 (1981-05-01), Kusakabe
patent: 4704738 (1987-11-01), Graziadei et al.
patent: 5847623 (1998-12-01), Hadjichristos
patent: 6026286 (2000-02-01), Long
“Single Sideband Systems And Circuit”, McGraw Hill, Second Edition, pp. 149-155, William E. Sabin and Edgar O. Schoenike.
Eppele Kyle
Jensen Nathan O.
O'Shaughnessy J. P.
Rockwell Collins, Inc.
To Doris H.
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