Mixer using four quadrant multiplier with reactive feedback elements

A mixer comprising:

• a first differential amplifier having a common emitter node;
• a second differential amplifier having a common emitter node, the first differential amplifier cross connected with the second differential amplifier;
• a first transistor having a collector coupled to the common emitter node of the first differential amplifier;
• a second transistor having a collector coupled to the common emitter node of the second differential amplifier;
• a first shunt feedback reactance element coupled between a base and the collector of the first transistor, the first shunt feedback reactance element includes a first resistance-capacitance element;
• and
• a second shunt feedback reactance element coupled between a base and the collector of the second transistor, the second shunt feedback reactance element includes a second resistance-capacitance element.

A mixer comprising:

• a first differential amplifier having a common emitter node;
• a second differential amplifier having a common emitter node, the second differential amplifier cross connected with the first differential amplifier;
• a first output node coupled to a first collector of the first differential amplifier, the first collector cross connected with a first collector of the second differential amplifier;
• a second output node coupled to a second collector of the second differential amplifier, the second collector cross connected with a second collector of the first differential amplifier;
• a first transistor having a collector coupled to the common emitter node of the first differential amplifier;
• a second transistor having a collector coupled to the common emitter node of the second differential amplifier;
• a shunt feedback reactance element coupled between a base of the first transistor and the first output node;
• and
• another shunt feedback reactance element coupled between a base of the second transistor and the second output node.

A modified Gilbert cell comprising:

• a first differential amplifier having a common emitter node;
• a second differential amplifier having a common emitter node, the second differential amplifier cross connected with the first differential amplifier;
• a first transistor coupled to the common emitter node of the first differential amplifier;
• a second transistor coupled to the common emitter node of the second differential amplifier;
• and
• first and second reactance elements coupled to the respective first and second transistors so that the Gilbert cell has a conversion gain of less than 20 dB and a noise figure of less than 7 dB while operating at an input frequency in a range between 500 MHz and 2,000 MHz.

A modified Gilbert cell comprising:

• a first differential amplifier having a common emitter node;
• a second differential amplifier having a common emitter node the second differential amplifier cross connected with the first differential amplifier;
• a first transistor coupled to the common emitter node of the first differential amplifier;
• a second transistor coupled to the common emitter node of the second differential amplifier;
• and
• first and second reactance elements coupled to the respective first and second transistors so that the Gilbert cell has an input compression point of greater than −7 dBm and a noise figure of less than 7 dB while operating at an input frequency in a range between 500 MHz and 2,000 MHz.

A method of making a modified Gilbert cell, a Gilbert cell comprising a first differential amplifier having a first common emitter node and a second differential amplifier having a second common emitter node, the second differential amplifier cross connected with the first differential amplifier, a first transistor coupled to the first common emitter node, a second transistor coupled to the second common emitter node, and a mixer common node, the method of making comprising the steps of:

• providing a first series feedback reactance element coupled between an emitter of the first transistor and the mixer common node;
• providing a second series feedback reactance element coupled between an emitter of the second transistor and the mixer common node;
• providing a first shunt feedback reactance element coupled between a base and a collector of the first transistor, the first shunt feedback reactance element includes a first resistance-capacitance element;
• and
• providing a second shunt feedback reactance element coupled between a base and a collector of the second transistor, the second shunt feedback reactance element includes a second resistance-capacitance element.