Low power radio telephone image reject mixer

Details Low power radio telephone image reject mixer Low power radio telephone image reject mixer

2000-06-30

2004-02-03

Tran, P. (Department: 2685)

Telecommunications

Receiver or analog modulated signal frequency converter

Frequency modifying or conversion

C455S302000, C455S327000, C455S333000, C455S323000, C327S359000, C327S361000

Reexamination Certificate

active

06687494

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to the radio telephone art. Specifically, an image reject mixer is provided which draws a minimum of current to preserve the battery life for the radio telephone.
Image rejection mixers solve a common problem of interfering signals experienced by cellular radio telephone receivers. Using a hetrodyne conversion system, the conversion of the input radio frequency signal to an intermediate frequency signal may simultaneously produce undesirable mixing products called spurs which interferes with the conversion of the signal of interest. The most common type of spur encountered in the frequency conversion is an image, i.e., the product of converting an adjacent signal at a lower frequency to a mixing product which interferes with the immediate frequency signal produced by the signal of interest.
A common technique used to reject spurs or images is to use a filter that prevents the radio frequency signal adjacent the radio frequency of interest from entering the frequency conversion circuitry. Filters, however, are large, costly, and may consume an undesirable amount of current from the battery. Another approach to the image problem is to use special phasing techniques which cancel out the image. These image reject mixers, while effective in rejecting the image, also suffer from high current consumption which reduces the battery life. It is therefore desirable to provide an image rejection mixer which can operate at low current, thereby saving battery power, while preserving the lineary and noise performance of the frequency conversion circuit.
SUMMARY OF THE INVENTION
In accordance with the invention, first and second doubly balanced mixers are provided which convert a common radio frequency signal to an intermediate frequency signal. The first doubly balanced mixer produces a pair of differential currents which represent the sum and difference of the local oscillator signal and a radio frequency signal. A second doubly balanced mixer frequency converts the same radio frequency signal producing a pair of differential currents representing the sum and difference of the radio frequency signal, using a ninety degree phase shifted version of the local oscillator signal. The first and second pairs of differential signals are combined in a quadrature combining circuit to produce a differential intermediate frequency signal substantially free of signal images.


REFERENCES:
patent: 3805163 (1974-04-01), Hata et al.
patent: 4584715 (1986-04-01), Baars et al.
patent: 5033110 (1991-07-01), Harman
patent: 5140198 (1992-08-01), Atherly et al.
patent: 5794131 (1998-08-01), Cairns
patent: 5870670 (1999-02-01), Ripley et al.
patent: 5950119 (1999-09-01), McGeehan et al.
patent: 5973576 (1999-10-01), Ariie
patent: 6029059 (2000-02-01), Bojer
patent: 6226509 (2001-05-01), Mole et al.
patent: 6308058 (2001-10-01), Souetinov et al.
patent: 6313688 (2001-11-01), Lee et al.
patent: 6343211 (2002-01-01), Thodesen et al.

Affiliated with

Also associated with

Rating

Low power radio telephone image reject mixer does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Low power radio telephone image reject mixer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low power radio telephone image reject mixer will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3335587