Mixer and temperature compensation method thereof

Abstract

A mixer includes a switching circuit, a first transistor, a second transistor, a bias circuit, and a compensation current source. The first transistor has a first terminal coupled to a first endpoint of the switching circuit, a control terminal, and a second terminal coupled to a ground terminal. The second transistor has a first terminal coupled to a second endpoint of the switching circuit, a control terminal, and a second terminal coupled to a ground terminal. The bias circuit adjusts the first conductance value of the first transistor and the second conductance value of the second transistor using a bias current. The compensation current source supplies compensation current to the first transistor and the second transistor respectively according to the internal resistance value of the bias circuit. The compensation current further adjusts the first and second conductance values ​​to prevent them from changing due to the operating temperature of the mixer.

Claims

1. A mixer, comprising: a switching circuit; a first transistor having a first terminal coupled to a first endpoint of the switching circuit, a control terminal, and a second terminal coupled to a ground terminal; a second transistor having a first terminal coupled to a second endpoint of the switching circuit, a control terminal, and a second terminal coupled to the ground terminal; a bias circuit coupled to the control terminal of the first transistor and the control terminal of the second transistor, for adjusting a first conductance value of the first transistor and a second conductance value of the second transistor using a bias current; and a compensation current source coupled to the first terminal of the first transistor and the first terminal of the second transistor, for supplying a compensation current to the first transistor and the second transistor respectively according to an internal resistance value of the bias circuit, wherein the compensation current is used to further adjust the first conductance value and the second conductance value so that the first conductance value and the second conductance value are not affected by an operating temperature of the mixer.

2. The mixer as claimed in claim 1, wherein the bias circuit sets a bias voltage through the bias current and transmits the bias voltage to the control terminal of the first transistor and the control terminal of the second transistor.

3. The mixer as claimed in claim 2, wherein the bias circuit comprises: a third transistor having a first terminal for receiving an operating voltage, a control terminal, and a second terminal; a fourth transistor having a first terminal and a control terminal coupled to the second terminal of the third transistor, and a second terminal; a fifth transistor having a first terminal for receiving the operating voltage, a control terminal coupled to the control terminal of the third transistor, and a second terminal; a sixth transistor having a first terminal coupled to the second terminal of the fifth transistor, a control terminal coupled to the control terminal of the fourth transistor, and a second terminal; a seventh transistor having a first terminal for receiving the operating voltage, a control terminal coupled to the control terminal of the third transistor, and a second terminal coupled to the control terminal of the first transistor; and an eighth transistor having a first terminal coupled to the second terminal of the seventh transistor, a control terminal, and a second terminal coupled to the ground terminal; A first bipolar transistor having a first terminal coupled to the second terminal of the fourth transistor, and a control terminal and a second terminal coupled to the ground terminal; a second bipolar transistor having a first terminal, and a control terminal and a second terminal coupled to the ground terminal; and a first resistor having a first terminal coupled to the second terminal of the sixth transistor, and a second terminal coupled to the second bipolar transistor.

4. The mixer as claimed in claim 3, wherein the internal resistance of the bias circuit is the resistance value of the first resistor.

5. The mixer as claimed in claim 4, wherein the bias current is generated according to the following formula: where is the bias current, is a threshold voltage, is the internal resistance value, and is the ratio of the second bipolar transistor to the first bipolar transistor.

6. The mixer as claimed in claim 1, wherein the compensation current source comprises: a second resistor; an operational amplifier having a first input terminal receiving a reference voltage, a second input terminal coupled to the second resistor, and an output terminal; a ninth transistor having a first terminal receiving the reference voltage, a control terminal coupled to the output terminal of the operational amplifier, and a second terminal coupled to the second resistor; at least one tenth transistor having a first terminal receiving the reference voltage, a control terminal coupled to the output terminal of the operational amplifier, and a second terminal; and at least one switch having a first terminal coupled to the second terminal of the at least one tenth transistor, and a second terminal coupled to the first terminal of the first transistor.

7. The mixer as claimed in claim 6, wherein the resistance value of the second resistor of the compensation current source is equal to the internal resistance value of the bias circuit.

8. The mixer as claimed in claim 1, wherein the first transistor and the second transistor are used to convert an input signal pair into current, and the switching circuit modulates the input signal pair converted into current through an oscillating signal pair, thereby generating a mixing signal pair.

9. A mixer, comprising: a switching circuit; a first transistor having a first terminal coupled to a first endpoint of the switching circuit, a control terminal, and a second terminal coupled to a ground terminal; a second transistor having a first terminal coupled to a second endpoint of the switching circuit, a control terminal, and a second terminal coupled to the ground terminal; a first bias circuit coupled to the control terminal of the first transistor for adjusting a first conductance value of the first transistor using a first bias current; a second bias circuit coupled to the control terminal of the second transistor for adjusting a second conductance value of the second transistor using a second bias current; a first compensation current source coupled to the first terminal of the first transistor for supplying a first compensation current to the first transistor according to a first internal resistance value of the first bias circuit; and a second compensation current source coupled to the first terminal of the second transistor for supplying a second compensation current to the second transistor according to a second internal resistance value of the second bias circuit. The first compensation current is used to further adjust the first conductance value so that the first conductance value is not affected by the operating temperature of the mixer. The second compensation current is used to further adjust the second conductance value so that the second conductance value is not affected by the operating temperature. The first internal resistance value is different from the second internal resistance value.

10. A temperature compensation method applicable to a mixer, wherein the mixer includes a switching circuit, a first transistor, and a second transistor, the temperature compensation method comprising: generating a bias current through a bias circuit; adjusting a first conductance value of the first transistor and a second conductance value of the second transistor according to the bias current; supplying a compensation current to the first transistor and the second transistor respectively through a compensation current source, wherein the compensation current is set according to an internal resistance value of the bias circuit; and further adjusting the first conductance value and the second conductance value using the compensation current, so that the first conductance value and the second conductance value are not affected by an operating temperature of the mixer.

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