Quadrature mixer circuit and RF communication semiconductor integrated circuit

Abstract

A quadrature mixer circuit and an RF communication semiconductor integrated circuit capable of suppressing variations in secondary distortion while reducing the current consumption are provided. In a quadrature mixer circuit, even if local signals different by 90 degrees inputted to the bases of I transistors and Q transistors have large amplitudes, interference is suppressed by I resistors, Q resistors, and capacitors. Also, since the capacitors are provided, changes in bias current values can be suppressed. Accordingly, variations in secondary distortion can be suppressed. Furthermore, the capacitors combine current outputs of a differential circuit formed of I transistors and the resistor and a differential circuit formed of Q transistors and the resistor. Therefore, current consumption can also be reduced.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a block diagram showing one example of a quadrature mixer circuit according to one embodiment of the present invention;

FIG. 2 is a block diagram showing one example of a quadrature mixer circuit according to a first conventional example; and

FIG. 3 is a block diagram showing one example of a quadrature mixer circuit according to a second conventional example.

Claims

1. A quadrature mixer circuit comprising: an input terminal;first and second voltage-current converter circuits having a same function to convert a signal voltage from said input terminal to a signal current;a first DC current source which supplies a bias current to said first voltage-current converter circuit;a second DC current source which supplies a bias current to said second voltage-current converter circuit;a local signal oscillator;a 90-degree phase-shift circuit which outputs a local signal of said local signal oscillator with a phase advanced or delayed by 90 degrees;a first current combiner circuit which outputs, as a first output current, a sum current of a first output current of said first voltage-current converter circuit and a second output AC current of said second voltage-current converter circuit;a second current combiner circuit which outputs, as a second output current, a sum current of a first output AC current of said first voltage-current converter circuit and a second output current of said second voltage-current converter circuit;a first current switching circuit which switches the first output current of said first current combiner circuit at a timing of the local signal of said local signal oscillator;a second current switching circuit which switches the second output current of said second current combiner circuit at a timing of the local signal which is an output from said 90-degree phase-shift circuit;a first current-voltage converter circuit which converts an output signal current of said first current switching circuit to a voltage signal; anda second current-voltage converter circuit which converts an output signal current of said second current switching circuit to a voltage signal.

2. The quadrature mixer circuit according to claim 1, wherein an amplitude of a voltage at an output terminal of the first output current of said first current combiner circuit is different from an amplitude of a voltage at an output terminal of the second output current of said second current combiner circuit.

3. The quadrature mixer circuit according to claim 2, wherein a sum of the bias current of said first voltage-current converter circuit and the bias current of said second voltage-current converter circuit is equal to or larger than a sum of a bias current of said first current switching circuit and a bias current of said second current switching circuit.

4. An RF communication semiconductor integrated circuit which includes a Gilbert-cell-type quadrature mixer circuit comprising: a first differential circuit which receives an RF receive signal voltage or an IF receive signal voltage converted from the RF receive signal voltage to convert it to first and second RF receive signal currents different in phase by 180 degrees or first and second IF receive signal currents different in phase by 180 degrees;a second differential circuit which receives an RF receive signal voltage or an IF receive signal voltage converted from the RF receive signal voltage to convert it to third and fourth RF receive signal currents different in phase by 180 degrees or third and fourth IF receive signal currents different in phase by 180 degrees;a local signal oscillator;a 90-degree phase-shift circuit which outputs a local signal of said local signal oscillator with a phase advanced or delayed by 90 degrees;a third differential circuit which has a first current input terminal receiving a current input, receives the local signal of said local signal oscillator to switch the current inputted to said first current input terminal at a timing of said local signal oscillator, and converts the current to first and second I output signal currents different in phase by 180 degrees;a fourth differential circuit which has a second current input terminal receiving a current input, receives the local signal of said local signal oscillator to switch the current inputted to said second current input terminal at a timing different in phase by 180 degrees from said local signal oscillator, and converts the current to third and fourth I output signal currents different in phase by 180 degrees;a fifth differential circuit which has a third current input terminal receiving a current input, receives the local signal which is the output of said 90-degree phase-shift circuit to switch the current inputted to said third current input terminal at a timing of the local signal which is the output of said 90-degree phase-shift circuit, and converts the current to first and second Q output signal currents different in phase by 180 degrees;a sixth differential circuit which has a fourth current input terminal receiving a current input, receives the local signal which is the output of said 90-degree phase-shift circuit to switch the current inputted to said fourth current input terminal at a timing different in phase by 180 degrees from the local signal which is the output of said 90-degree phase-shift circuit, and converts the current to third and fourth Q output signal currents different in phase by 180 degrees;a first I signal current adding and coupling unit which adds and couples said first I output signal current and said third I output signal current to output a fifth I signal current;a second I signal current adding and coupling unit which adds and couples said second I output signal current and said fourth I output signal current to output a sixth I signal current;a first Q signal current adding and coupling unit which adds and couples said first Q output signal current and said third Q output signal current to output a fifth Q signal current; anda second Q signal current adding and coupling unit which adds and couples said second Q output signal current and said fourth Q output signal current to output a sixth Q signal current,wherein the first RF receive signal current or the first IF receive signal current of said first differential circuit is coupled to said first current input terminal via a first voltage drop element,the third RF receive signal current or the third IF receive signal current of said second differential circuit is coupled to said third current input terminal via a second voltage drop element, and the first RF receive signal current or the first IF receive signal current is added and coupled to the third RF receive signal current or the third IF receive signal current by using a first capacitor,the second RF receive signal current or the second IF receive signal current of said first differential circuit is coupled to said second current input terminal via a third voltage drop element, andthe fourth RF receive signal current or the fourth IF receive signal current of said second differential circuit is coupled to said fourth current input terminal via a fourth voltage drop element, and the second RF receive signal current or the second IF receive signal current is added and coupled to the fourth RF receive signal current or the fourth IF receive signal current by using a second capacitor.