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Design Notes

Differential Gilbert_Cell_Mixer

This project demonstrates the new differential probe measurement feature of the AWR Design Environment and the improved performance of the Harmonic Balance simulator.

To show the speed improvements and support for fairly complex circuits a differential Gilbert Cell mixer is used.  This mixer design also includes driver stages, output stages and current sources.   

Overview

The schematic, “Gilbert_Cell_Mixer” contains 22 transistors in a DC coupled design.  Several of these transistors are set up to control the current through the differential stages.  The use of annotation to display the device current helps the designer check that each stage is operating at the correct bias point.

The LO signal is amplified and then applied to the upper quad set of switching transistors.  The signal also undergoes some amplification and is applied to the lower differential amplifier.  The mixer uses a differential output.

Gilbert_Cell_Mixer

Two methods of making the differential measurement are demonstrated in the schematic, “Gilbert_Cell_Mixer”.  A simple voltage measurement is made using a V_METER.  This element is found in the MeasDevices node in the element tree.  A second method is also used as an alternative.  Here we use two probes and make use of the differential probe measurement VtimeD.  The use of probes simplifies the process of making differential measurements, a V_METER elements needs to have wires that join this element to the various circuit nodes.

Schematic - Gilbert_Cell_Mixer

Graph - IF Voltage

Graph - LO Voltage

Graph - Spectrum at Different Input Power Levels