Gate circuit provides improved timing alignment among 25% duty-cycle non-overlapping local oscillator signals for a quadrature mixer

It is known to de-skew differential local oscillator signals with cross coupled inverters (fig.1, 9 & 11). The present invention develops the technique to provide 25% duty-cycle non-overlapping waveforms. A synthesizer (fig.4, 205) generates a plurality of waveforms. Inverters (fig.4, 210A-D) receive the waveforms from the synthesizer. The inverters provide quadrature Local Oscillator (LO) clock waveforms LO_0, LO_90, LO_180 and LO_270 at their outputs. The clock waveforms are coupled to de-skewing circuit 220, comprising NOR gates 220A-D. The output of each NOR gate 220A D may be connected to a respective clock waveform line LO_(0-270) from the output of an inverter. Each NOR gate has three inputs and may receive clock waveforms from each of the three clock signal lines to which its output is not connected. Negotiation (contention) between the outputs of the inverters and the outputs of the NOR gates can improve the signal timing. Each clock signal line thus passes through the de-skewing circuit 220 responsive to the three other waveforms being at logic "0". The clock signals drive a quadrature switching mixer (fig.4, 215).