Structure and method for super FET mixer having logic-gate generated FET square-wave switching signal

In a mixer having at least one FET mixing element, a method for generating a mixer output signal using a local oscillator switching signal to switch said FET mixing element between ON and OFF conduction states and reduce distortion in said mixer output signal;

• said method comprising the steps of:
• receiving a first substantially sinusoidal signal at a first frequency and a second signal;
• generating substantially 180-degree phase separated signals at said first frequency from said received first sinusoidal signal;
• generating a voltage potential isolated differential signal pair at said first frequency from said phase separated signals;
• generating a substantially square-wave signal at said first frequency from said differential signal pair;
• driving said at least one FET mixing element with said substantially square wave signal as a mixer local oscillator signal so that said FET is in an ON conduction state when said square wave output signal is at a first amplitude level and is in an OFF conduction state when said square wave is at a second amplitude level;
• said substantially square-wave signal having a slew rate between said first and second amplitude levels minimizing the period of time said at least one FET mixing element is in an intermediate conduction state between said ON and OFF states;
• and
• generating said mixer output signal as a product of said second signal and said substantially square-wave signal;
• distortion in said mixer output signal being reduced by minimizing the period of time spent by said FET mixing element in transition between said ON and OFF FET conduction states.

A mixer comprising:

• a phase splitter circuit receiving an external local oscillator signal and generating first and second phase separated signals at a local oscillator frequency having substantially 180 degree phase difference between each other;
• an isolation circuit generating first and second differential signal pairs from said first and second phase separated signals;
• a square wave signal generation circuit generating first and second square waves respectively from said first and second differential signal pairs;
• a first switching device and a second switching device receiving said first and second square wave signals and a mixer input signal and generating a mixer output signal, each said square wave signal having a slew rate leading and trailing signal edge such that said first switching device switches ON when said second switching device switches OFF to minimize the period of time spent in transition between ON and OFF conduction states of the switching devices;
• and
• a signal separation circuit for separating said mixer output signal from said mixer input signal.

In a mixer having a signal mixing element, a method for generating a low-distortion mixer output signal comprising the steps of:

• receiving a first sinusoidal signal;
• generating two 180-degree phase separated signals from said received first sinusoidal signal;
• generating a pair of voltage isolated differential signals from said each of said phase separated signals;
• receiving said pairs of differential signals and generating a substantially square-wave mixer switching signal at a local oscillator frequency from said two-pairs of differential signals;
• driving said signal mixing element with said square-wave signal to drive said signal mixing element to either an ON conduction state when said square-wave signal is at a first signal level or an OFF conduction state when said square-wave signal is at a second signal level to minimize the period of time said signal mixing element generates distortion components while in an intermediate conduction state between said ON and OFF conduction states;
• and
• generating said mixer output signal as a product of said square-wave signal at said local oscillator frequency and a second input signal, distortion signal components in said mixer output signal being reduced by virtue of having reduced the period of time spent in transition between said ON and OFF FET conduction states.