KR100812228B1 - Double balanced frequency mixer using miller effect - Google Patents

Abstract

A double balanced frequency mixer using a miller effect is provided to improve an integration of a chip by minimizing a noise generated from a constant current source using a miller effect and reducing a total chip area. A double balanced frequency mixer using a miller effect includes amplifying transistors(M11,M12), switching transistors(M13-M16), a constant current source(IBIAS), and buffers(B1,B2). The amplifying transistors amplify RF+ signal and RF- signal having a complementary phase inputted to a gate electrode, and output the amplified signal to a drain electrode. The switching transistors are connected to the drain electrode of the amplifying transistors in a symmetrically parallel. The switching transistors switch the amplified RF+ and RF- signals outputted from the drain electrode of the amplifying transistors in response to an LO+ signal and an LO- signal having a complementary phase. The switching transistors output complementary IF+ and IF- signals. The constant current sources have first and second transistors of which first and second capacitors are connected to the gate electrode. The constant current sources provide a current to the amplifying transistor through the first and second transistors in response to a power voltage. The buffers feedback a part of the IF+ and IF- signals outputted from the switching transistors to the first and second capacitors connected to the gate electrode of the first and second transistors.

Description

Double balanced frequency mixer using miller effect

1 is a schematic circuit diagram of a conventional dual balanced frequency mixer.

2 is a schematic circuit diagram of a dual balanced frequency mixer using the Miller effect according to the present invention.

3 is a circuit diagram for explaining the Miller effect.

4 is a graph showing the noise figure of both side bands in the first band band (3432MHz) in the dual balanced frequency mixer using the Miller effect according to the present invention.

5 is a graph showing the noise figure of both side bands in various bands in the dual balanced frequency mixer using the Miller effect according to the present invention.

6 is a view showing the result of comparing the characteristics of the dual balanced frequency mixer and the conventional double balanced frequency mixer using the Miller effect according to the present invention.

* Explanation of symbols for the main parts of the drawings *

100, 100 ': input terminal transistor section

200, 200 ': output transistor section

110: RF + signal input terminal

120: RF- signal input terminal

210, 220: LO + signal input terminal

230: LO- signal input terminal

M11, M12: field effect transistor for driving amplification

M13, M14, M15, M16: Field effect transistor for switching

M17, M18: Field effect transistor for bleeding

R1, R2: resistance

L: Inductor

B1, B2: buffer

C1, C2: Capacitor

The present invention relates to a dual balanced frequency mixer using the Miller effect, and more particularly, to a technique for implementing a dual balanced frequency mixer having low noise characteristics by reducing the noise generated in the current source using the Miller effect. .

Recently, interest in ultra wideband (UWB) communication systems that can share frequency without mutual interference with narrowband and broadband systems such as mobile communication, satellite communication, and broadcasting for the effective use of limited frequency resources, have.

The ultra-wideband communication system uses a weak radio wave of -41 dBm / MHz or less over a very wide radio frequency (RF) band of 3.1 to 10.6 GHz to share the frequency without interfering with the existing wireless system. It has the advantage of being able to obtain a high data rate of 1Gbps in the near field.

In such an ultra-wideband communication system, a frequency mixer is generally used at a receiving end to shift information of an arbitrary frequency component to another frequency band in order to receive all signals of a wide frequency band.

Frequency mixers are largely classified into single-ended frequency mixers and balanced frequency mixers. Balanced mixers are again single balanced frequency mixers and double balanced frequency mixers. Separated by.

1 is a circuit diagram of a conventional dual balanced frequency mixer, briefly explaining its configuration and operation principle as follows.

As shown in FIG. 1, the dual balanced frequency mixer includes an RF + signal having a phase complementary to each other, an input stage transistor unit 100 that receives and amplifies the RF + signal through a gate, and an LO + signal having complementary phases to each other. And an output terminal transistor unit 200 which receives an LO- signal as a gate and intercepts an amplified RF + signal and an RF- signal output from the input terminal transistor unit 100 and outputs an IF + signal and an IF- signal, respectively.

The mixer of the double balance structure as described above has excellent linearity due to improved spurious response due to its structural characteristics, and has an advantage of simple matching circuit.

However, as shown in FIG. 1, one constant current source I _BIAS is used in the dual balanced frequency mixer, and the constant current source I _BIAS is composed of transistors M21, M22, and M23 which are active elements. The transistors M21, M22, and M23 have a problem in that the overall noise figure of the mixer is increased.

As a method for solving the noise problem caused by the constant current source (I _BIAS ), a method of removing the noise signal by connecting the bypass capacitor (C _p ) as shown in Figure 1, but in this case a large area Due to the bypass capacitor (C _p ) that occupies, not only the area of the chip is increased but also the power consumption is increased and linearity is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to use a Miller effect to minimize the noise generated from the constant current source while reducing the total chip area to achieve a dual balanced frequency mixer To provide.

In order to achieve the above object, the dual balanced frequency mixer using the Miller effect according to the present invention includes a driving amplifying transistor for amplifying an RF + signal and an RF- signal having mutually complementary phases input to a gate electrode and outputting the RF + signal to a drain electrode; An amplified RF + signal output from the drain electrode of the driving amplifying transistor in response to an LO + signal and a LO- signal having a phase complementary to each other by being symmetrically connected in parallel to the drain electrode of the driving amplifying transistor; A switching transistor for interrupting the RF- signal and outputting a complementary IF + signal and an IF- signal; A constant current source including first and second transistors having first and second capacitors connected to gate electrodes, respectively, and supplying current to the driving amplifying transistor through the first and second transistors according to application of a power voltage; And a buffer for returning a part of the IF + signal and the IF− signal output from the switching transistor to the first and second capacitors connected to the gate electrodes of the first and second transistors, respectively.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a schematic circuit diagram of a dual balanced frequency mixer using the Miller effect according to the present invention, in which R _L denotes a load resistor and V _DD denotes a power supply terminal.

As shown in FIG. 2, the dual balanced frequency mixer using the Miller effect according to the present invention includes an input stage transistor unit 100 ′ which receives RF + signals and RF- signals having a phase complementary to each other and is amplified, respectively. And receiving the LO + signal and the LO- signal having complementary phases as gates, intermittently amplifying the amplified RF + signal and the RF- signal output from the input transistor unit 100 'and outputting them as IF + signals and IF- signals, respectively. And a capacitor C1, C2 connected to the gates of the transistors M21, M22 of the constant current source I _BIAS through the buffers B1, B2. ), And the capacitance (capacitance) of the capacitors C1 and C2 is amplified by the Miller effect.

The input terminal transistor unit 100 'includes an input terminal 110 for inputting an RF + signal, an input terminal 120 for inputting an RF + signal, and a driving amplification field effect transistor for receiving and amplifying the RF + signal through a gate. M11 and a drive amplification field effect transistor M12 for receiving and amplifying the RF- signal through a gate.

The output terminal transistor unit 200 ′ includes input terminals 210 and 220 for inputting an LO + signal, an input terminal 230 for inputting an LO− signal, an output terminal 240 for outputting an IF + signal, and an IF−. The output terminal 250 for outputting a signal and the symmetrical parallel connection to the drain electrode of the field effect transistor M11 reversely drive each other and shift the RF signal output from the drain electrode by a local oscillation frequency input to the gate electrode. A local oscillation frequency in which the switching field effect transistors M13 and M14 and the drain electrode of the field effect transistor M12 are symmetrically connected in parallel to each other to reversely drive each other, and the RF signal output from the drain electrode is input to the gate electrode. Switching field effect transistors (M15, M16) and double balanced frequency mixers as bleeding current sources for improved conversion gain and linear characteristics. And a small field-effect transistor (M17, M18) for releasing that, comprises an inductor (L) to remove the noise signal generated by the bleeding field effect transistor (M17, M18) for.

The bleeding field effect transistor M17 is connected in parallel with the switching transistors M13 and M14 to apply a drain current corresponding to the DC voltage applied to its gate-source terminal to the drain terminal of the driving amplifying transistor M11. The circuit is supplied as a bleeding current, and at the same time, AC is complementary to the drive amplifying transistor M11 to reduce the amount of current flowing through the switching transistors M13 and M14. Similarly, the bleeding field effect transistor M18 is connected in parallel with the switching transistors M15 and M16 to supply a drain current corresponding to the DC voltage applied to its gate-source terminal of the driving amplifying transistor M12. The circuit is supplied as a bleeding current to the drain stage, and at the same time, AC is complementary to the driving amplifying transistor M12 to reduce the amount of current flowing through the switching transistors M15 and M16. .

When such bleeding field effect transistors M17 and M18 are used in a double balanced mixer, an inductor L for removing noise signals generated by the bleeding field effect transistors M17 and M18 is preferably included. Do.

Meanwhile, the present invention returns the IF + signal and the IF- signal to the small capacitors C1 and C2 connected to the gates of the transistors M21 and M22 through the buffers B1 and B2, respectively, and the capacitor is caused by the Miller effect. The biggest characteristic of the capacitance of (C1, C2) is to be amplified, so that the Miller effect is briefly described as follows to help the present invention.

3 is a circuit diagram illustrating the Miller effect used in the present invention, where -A is the gain of the amplifier, X is the input terminal, Y is the output terminal, and C _F is the capacitance of the capacitor.

As shown in Fig. 3, the Miller effect refers to the effect that the capacitance C _F of the capacitor connected between the input and output terminals of the amplifying circuit whose gain is -A is seen as C _F (1 + A) from the input side.

Accordingly, in the present invention, as shown in FIG. 2, the capacitor C1 and C2 having a small size are connected to the gates of the transistors M21 and M22 constituting the constant current source I _BIAS using the Miller effect. The feedback circuit was configured to return the IF + signal and the IF− signal to the capacitors C1 and C2 through the buffers B1 and B2 to amplify the capacitance of the capacitors C1 and C2 by the Miller effect. .

That is, according to such a feedback circuit configuration, a large capacitance can be obtained by only small capacitors C1 and C2, and thus low-frequency noise generated in transistors M21 and M22 constituting the constant current source I _BIAS . It can be reduced even by the small capacitors C1 and C2. In addition, by using the capacitors C1 and C2 of small size, the total chip area can be reduced and integration can be achieved.

Hereinafter, the operation of the dual balanced frequency mixer according to the present invention will be described in detail.

Referring back to FIG. 2, the RF + signal having the positive phase input to the input terminal 110 is input to the gate terminal of the field effect transistor M11 and amplified and then at the drain terminal of the field effect transistor M11. It is output as an RF- signal having a negative phase and transferred to the common source terminal of the field effect transistors M13 and M14. The RF- signal input to the input terminal 120 is input to the gate terminal of the field effect transistor M12. After the amplification, the signal is outputted as an RF + signal from the drain terminal of the field effect transistor M12 and transferred to the common source terminal of the field effect transistors M15 and M16.

In addition, the LO + signal having the positive phase input to the input terminal 210 is intermittently inputted to the gate terminal of the field effect transistor M13, and the RF- signal transmitted from the source terminal of the field effect transistor M13 to the drain terminal is intermittent. In addition, the LO + signal input to the input terminal 220 is input to the gate terminal of the field effect transistor M16 to intercept the RF + signal transferred from the source terminal of the field effect transistor M16 to the drain terminal. In addition, the LO- signal having the negative phase input to the input terminal 230 is input to the gate terminal of the field effect transistors M14 and M15 and is transferred to the drain terminal from the source terminal of the field effect transistor M14. The RF + signal transmitted from the source terminal to the drain terminal of the signal and the field effect transistor M15 is interrupted.

As a result of the intermittent action, the IF + signal having a positive phase which is a component corresponding to the frequency difference between the RF signal and the LO signal to the drain terminal of the field effect transistor M15 is passed to the output terminal 240 through the buffer B1. The IF- signal having a negative phase, which is a component corresponding to the frequency difference between the RF signal and the LO signal, is output to the output terminal 250 through the buffer B2 to the drain terminal of the field effect transistor M14.

At this time, some of the IF + signals output from the buffer B1 are fed back to the capacitor C1 connected to the gate of the transistor M21 of the constant current source I _BIAS , and likewise, output from the buffer B2. Some of the IF− signals are fed back to capacitor C2 connected to the gate of transistor M22 of constant current source I _BIAS .

As the IF + signal and the IF- signal are fed back to the capacitors C1 and C2 through the buffers B1 and B2, the capacitances of the capacitors C1 and C2 are amplified by the above-described Miller effect. Only the capacitors C1 and C2 of the transistors can reduce noise in the low frequency band generated by the transistors M21 and M22 of the constant current source I _BIAS . In addition, the use of a capacitor of a small size makes it possible to reduce the total chip area for integration.

4 is a graph showing the noise figure of the double-side band in the first band band (3432MHz) in the dual balanced frequency mixer using the Miller effect according to the present invention.

As can be seen in Figure 4, it can be seen that the noise figure of the dual balanced frequency mixer using the Miller effect is improved by about 6 dB compared to the case of not using the Miller effect, which is the capacitance of the capacitor (C1, C2) by the Miller effect This is because amplification reduces the noise in the low frequency band.

FIG. 5 is a graph showing the noise figure of both side wave bands in various band bands in the dual balanced frequency mixer using the Miller effect according to the present invention. As shown in FIG. 5, the dual balanced frequency mixer according to the present invention is a Miller. It can be seen that the effect can effectively reduce the noise of the low frequency band in various band bands.

6 shows a result of comparing the characteristics of the dual balanced frequency mixer using the Miller effect according to the present invention and the conventional dual balanced frequency mixer, in which the total noise figure of the receiving end of the ultra wideband communication system is 6.6 dB and Starting at 4.125 MHz, we measured the noise figure at 4 MHz and the noise figure at 264 MHz.

As can be seen in Figure 6, the dual balanced frequency mixer using the Miller effect according to the present invention compared to the conventional double balanced frequency mixer, the conversion gain and leakage index, etc. can be seen that the noise figure is improved. This is because noise in the low frequency band is reduced by capacitance amplification of the capacitors C1 and C2 by the Miller effect.

So far, the present invention has been described with reference to the preferred embodiments, and those skilled in the art to which the present invention belongs may be embodied in a modified form without departing from the essential characteristics of the present invention. You will understand. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

As described above, according to the present invention, in the dual balanced frequency mixer, even a small capacitor can effectively reduce the noise generated from the constant current source by using the Miller effect, thereby reducing the total chip area to achieve integration. It can work.

Claims (6)

A driving amplifying transistor for amplifying and outputting an RF + signal and an RF- signal having mutually complementary phases input to the gate electrode to a drain electrode; An amplified RF + signal output from the drain electrode of the driving amplifying transistor in response to an LO + signal and a LO- signal having a phase complementary to each other by being symmetrically connected in parallel to the drain electrode of the driving amplifying transistor; A switching transistor for interrupting the RF- signal and outputting a complementary IF + signal and an IF- signal; A constant current source including first and second transistors having first and second capacitors connected to gate electrodes, respectively, and supplying current to the driving amplifying transistor through the first and second transistors according to application of a power voltage; And And a buffer for returning a part of the IF + signal and the IF- signal output from the switching transistor to the first and second capacitors connected to the gate electrodes of the first and second transistors, respectively. Frequency mixer. The method of claim 1, 2. The dual balanced frequency mixer using the Miller effect, wherein the capacitance of the first and second capacitors connected to the gate electrodes of the first and second transistors is amplified by the Miller effect. The method of claim 1, It is connected in parallel with the switching transistor and supplies a drain current corresponding to the DC voltage applied to its gate-source terminal as a bleeding current to the drain terminal of the driving amplifying transistor, and operates complementarily with the driving amplifying transistor. And a bleeding transistor for reducing the amount of current flowing through the switching transistor. 4. The dual balanced frequency mixer using the Miller effect of claim 3, further comprising an inductor for removing noise generated in the bleeding transistor. The method of claim 1, The power supply voltage is connected to the drain electrode of the first transistor through a resistor, the gate electrode of the second transistor is connected to the gate electrode, and the ground is connected to the source electrode, the dual balanced frequency mixer using the Miller effect. The method according to claim 1 or 5, The source electrode of the transistor for driving amplification is connected to the drain electrode of the second transistor, the gate electrode of the first transistor is connected to the gate electrode, and the ground electrode is connected to the source electrode. Frequency mixer.

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