Low voltage double balanced mixer
First Claim
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1. A mixer circuit arrangement, comprising:
- a) an amplifier stage having a single-ended input and a single-ended output;
b) a mixer core having first and second current signal inputs, first and second local oscillator inputs, and first and second differential outputs, the first current signal input of the mixer core being connected to the output of the amplifier stage;
c) a bias circuit having an output and a ground connection, the bias circuit comprising a source of DC current between the output of the bias circuit and the ground connection, the output of the bias circuit being connected to the second current signal input of the mixer core;
d) a capacitor having first and second electrodes connected to respective ones of the output and the ground connection of the bias circuit; and
e) a local oscillator driver circuit having a first oscillator input, and first and second outputs having a common mode output impedance and being connected respectively to the first and second local oscillator inputs of the mixer core, the first and second local oscillator inputs ofthe mixer core having a lower input impedance as compared to the common mode output impedance of the first and second outputs of the local oscillator driver circuit.
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Abstract
Mixer circuit 300 receives a single-ended rf voltage signal on terminal 330 and a bias potential on terminal 361. Transistor 301 functions as a transconductance amplifier and presents a current signal, representative of the input voltage signal, to mixer core 391. Inductor 310 provides noiseless degeneration in the base-emitter circuit of transistor 301. Local oscillator driver 393 is configured such that its common mode output impedance is higher than the input impedance of transistors 305 and 306. In this way, phase splitting is carried out within the mixer core 391 itself and less transistors are needed. Mixer circuit 300 thereby requires less voltage headroom than prior art mixers.
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Citations
10 Claims
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1. A mixer circuit arrangement, comprising:
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a) an amplifier stage having a single-ended input and a single-ended output;
b) a mixer core having first and second current signal inputs, first and second local oscillator inputs, and first and second differential outputs, the first current signal input of the mixer core being connected to the output of the amplifier stage;
c) a bias circuit having an output and a ground connection, the bias circuit comprising a source of DC current between the output of the bias circuit and the ground connection, the output of the bias circuit being connected to the second current signal input of the mixer core;
d) a capacitor having first and second electrodes connected to respective ones of the output and the ground connection of the bias circuit; and
e) a local oscillator driver circuit having a first oscillator input, and first and second outputs having a common mode output impedance and being connected respectively to the first and second local oscillator inputs of the mixer core, the first and second local oscillator inputs ofthe mixer core having a lower input impedance as compared to the common mode output impedance of the first and second outputs of the local oscillator driver circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification