Patent ID: 6731917
Filing Date: 2004-05-04
Classification: H03D,H04B

Abstract:
An apparatus comprising:a first signal generating circuit operable to generate first and second modulating signals at a first frequency, said first and second modulating signals having a phase difference; a second signal generating circuit operable to generate third and fourth modulating signals at a second frequency, and having a phase control portion operable to facilitate adjustment of a phase difference between said third and fourth modulating signals; a third signal generating circuit operable to generate fifth and sixth modulating signals at a third frequency, and having a phase control portion operable to facilitate adjustment of a phase difference between said fifth and sixth modulating signals; a first modulation stage operable to generate intermediate signals by using said first and second modulating signals to modulate an input signal; a second modulation stage operable to generate intermediate signals by selectively using said third, fourth, fifth and sixth modulating signals to modulate said intermediate signals from said first modulation stage; a combining section operable to generate first and second output signals which are each a function of selected said intermediate signals from said second modulation stage; and phase control circuitry operable to control said phase control portions of said first and second signal generating circuits so as to substantially avoid an image component in each of said first and second output signals; wherein said first modulation stage Includes a first modulating circuit which is operable to generate a first intermediate signal by using said first modulating signal to modulate the input signal, and a second modulating circuit which is operable to generate a second intermediate signal by using said second modulating signal to modulate the input signal, said first and second intermediate signals each being one of said intermediate signals generated by said first modulation stage; wherein said second modulation stage includes a third modulating circuit which is operable to generate a third intermediate signal by using said third modulating signal to modulate said first intermediate signal, a fourth modulating circuit which is operable to generate a fourth intermediate signal by using said fourth modulating signal to modulate said second intermediate signal, a fifth modulating circuit which is operable to generate a fifth intermediate signal by using said fifth modulating signal to modulate said second intermediate signal, and a sixth modulating circuit which is operable to generate a sixth intermediate signal by using said sixth modulating signal to modulate said first intermediate signal, said third, fourth, fifth, and sixth intermediate signals each being one of said intermediate signals generated by said second modulation stage; wherein said combining section includes a first combining circuit which is operable to generate said first output signal as a function of each of said third and fourth intermediate signals, and a second combining circuit which is operable to generate said second output signal as a function of each of said fifth and sixth intermediate signals; wherein said phase control circuitry controls said phase control portion of said second signal generating circuit so as to substantially avoid an image component in said first output signal, and controls said phase control portion of said third signal generating circuit so as to substantially avoid an image component in said second output signal; and wherein said phase control circuitry is responsive to said first output signal and controls said phase control portion of said second signal generating circuit as a function of said first output signal, and is responsive to said second output signal and controls said phase control portion of said third signal generating circuit as a function of said second output signal.