QUADRATURE MIXER CIRCUIT
A mixer is disclosed. In one embodiment, the mixer includes a polyphase filter that generates linear quadrature signals. The mixer also includes a potentiometric mixer that performs a frequency-conversion operation on the quadrature signal. According to the embodiments disclosed herein, the output of the potentiometric mixer has high linearity.
1 . A circuit comprising:
a polyphase filter that generates linear quadrature signals; and
a mixer circuit, wherein the mixer circuit comprises:
a plurality of transistors coupled to the output of the polyphase filter, wherein the plurality of transistors receive the linear quadrature signals from the polyphase filter and perform a frequency-conversion operation on the quadrature signals; and
at least one differential amplifier coupled to outputs the plurality of transistors, wherein an output of the at least one differential amplifier has high linearity.
2 - 3 . (canceled)
4 . The circuit of claim 1 wherein the output voltage swing of the mixer circuit is rail-to-rail.
5 . The circuit of claim 1 wherein the polyphase filter passively generates quadrature signals from an input signal and performs a 90-degree split on the input signal.
6 . The circuit of claim 1 wherein the frequency-conversion operation is a down-conversion operation.
7 . The circuit of claim 1 wherein the output voltage swing of the mixer circuit is limited by the output linearity of the differential amplifier.
8 . The circuit of claim 1 wherein the polyphase filter comprises at least two inputs.
9 . The circuit of claim 1 wherein the polyphase filter comprises a plurality of inputs.
10 . The circuit of claim 1 wherein the mixer circuit comprises at least one LO input.
11 . The circuit of claim 1 wherein the mixer circuit comprises a plurality of LO inputs.
12 . A method comprising:
generating linear quadrature signals using a polyphase filter; and
performing a frequency-conversion operation on the quadrature signals using a mixer circuit, wherein the mixer circuit comprises a plurality of transistors coupled to the output of the polyphase filter, wherein the plurality of transistors receive the linear quadrature signals from the polyphase filter and perform the frequency-conversion operation on the quadrature signals; and
at least one differential amplifier coupled to outputs the plurality of transistors, wherein an output of the at least one differential amplifier has high linearity.
13 - 14 . (canceled)
15 . The method of claim 12 wherein the output voltage swing of the mixer circuit is rail-to-rail.
16 . The method of claim 12 wherein the polyphase filter passively generates quadrature signals from an input signal and performs a 90-degree split on the input signal.
17 . The method of claim 12 wherein the frequency-conversion operation is a down-conversion operation.
18 . The method of claim 12 wherein the output voltage swing of the mixer circuit is limited by the output linearity of the differential amplifier.
19 . The method of claim 12 wherein the polyphase filter comprises at least one input.
20 . The method of claim 12 wherein the polyphase filter comprises a plurality of inputs.