Mitel Semiconductor Limited

Stephen P Graham

Viatcheslav Igorevich Souetinov

An image reject mixer arrangement comprises a transconductor first and second mixer cores and first and second phase shifters and and a summer or combiner 7. The mixer arrangement receives a single-ended RF voltage signal on a terminal a differential local oscillator signal on I-LO terminals indicated at and a 90&deg; phase shifted differential local oscillator signal on Q-LO terminals and provides differential IF output signals on output terminals From the output of the transconductor to the output of the combiner the image reject mixer arrangement carries signals in what can be described as a &ldquo;current mode&rdquo;, i.e. it is the current, not the voltage, which conveys the desired signal. In this current mode, it is advantageous to provide each active circuit block with a high output impedance and a low input impedance wherever possible. This is achieved by the cascode connection of the transistors of the transconductor with the transistors of the mixer cores and and the cascode connection of the transistors of the of the mixer cores and with the transistors of the combiner This is advantageous in providing improved noise performance, linearity and current consumption in comparison with cascade connected mixer arrangement circuit blocks.

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Swindon, United Kingdom

Stephen P Graham