Patent ID: 6496545
Filing Date: 2002-12-17
Classification: H03C,H03D,H04L

Abstract:
A single sideband mixer system comprising:first and second 90 degree phase shifters, each one of said phase shifters being of an all-pass type and each one having an input port and an output port; input circuitry for applying a first input frequency (&ohgr;1) to the input port of the first phase shifter for producing at its output port a first frequency signal equal to A1cos &ohgr;1t and a second frequency signal equal to B1sin(&ohgr;1t+&thgr;1); wherein the first phase shifter is of the type which causes A1 to be substantially equal to B1; input circuitry for applying a second input frequency (&ohgr;2) to the input port of the second phase shifter for producing at its output port a third frequency signal equal to A2cos &ohgr;2t and a fourth frequency signal equal to B2sin(&ohgr;2t+&thgr;2); wherein the second phase shifter is of the type which causes A2 to be substantially equal to B2; wherein &thgr;1 defines the angle by which the first and second frequency signals deviate from being orthogonal to each other; wherein &thgr;2 defines the angle by which the third and fourth frequency signals deviate from being orthogonal to each other; first and second mixer circuits, each mixer circuit having two inputs and an output at which is produced a signal which is a function of the product of its two inputs; coupling circuitry for applying one frequency signal from each of said first and second phase shifters to the inputs of the first mixer circuit and for applying the other frequency signal from each one of said first and second phase shifters to the inputs of the second mixer circuit; combining circuitry for combining the outputs of the two mixers to produce an output signal which is a function of either the sum or the difference of the first and second input frequencies; and wherein said first and second phase shifters are formed on and within the same integrated circuit; wherein each one of said first and second phase shifters includes resistive-capacitance (RC) networks for generating the first and second frequency signals so they are generally orthogonal to each other at the operating frequency of the first phase shifter and the third and fourth frequency signals so they are generally orthogonal to each other at the operating frequency of the second phase shifter; and wherein the first and second phase shifters are formed in close proximity to each other on said IC to ensure that any variation in the components of the first and second phase shifters track each other.