KR100345456B1 - Frequency Mixer for Microwave Monolithic Integrated Circuits - Google Patents

Abstract

The present invention provides a frequency mixer for microwave monolithic integrated circuits operating in a high frequency band having low power consumption, low noise, high gain and excellent signal separation between terminals and small size. The frequency mixer comprises: a first and a second matching circuit unit for receiving a local oscillator signal and a high frequency signal, respectively; A frequency core circuit unit which receives the frequency signals outputted from the first and second matching circuit units, mixes them, and converts them into intermediate frequency signals having new frequency components; And a low band filtering circuit unit for low band filtering the intermediate frequency signal output from the frequency core circuit unit to output a final intermediate frequency signal, wherein the frequency core circuit unit is respectively output from the first and second matching circuit units. Input means in the form of a cascode for receiving a local oscillator signal and said high frequency signal; Amplifying means for outputting said complementary intermediate frequency signal after performing an amplifying operation in response to said local oscillator signal and said high frequency signal from said input means; And an output matching means for receiving the complementary intermediate frequency signal from the amplifying means, removing the in-phase signal, mixing frequencies, and outputting the mixed frequency to the low band filtering circuit portion.

Description

Frequency Mixers for Microwave Monolithic Integrated Circuits

The present invention modulates or mixes a small high frequency signal (hereinafter referred to as RF) with a large local oscillation signal (hereinafter referred to as LO) and generates a new frequency component. The present invention relates to a frequency mixer for converting a signal into a signal, and more particularly to a frequency mixer for a microwave monolithic integrated circuit (MMIC).

As is well known, MMIC is a circuit in which active and passive elements are integrated together on the same semiconductor substrate. Therefore, when the circuit is MMIC than the circuit using the individual unit elements, the spacing between the elements can be reduced, thereby greatly reducing the size and weight of the circuit, and also due to the packaging of the unit elements. By eliminating a parasitic component inherently, the performance of the frequency bandwidth can be greatly improved. In order to enable mass production of cheap and simple wireless / mobile communication devices (eg, mobile communication terminals) that are currently required, inexpensive, reproducible, high-frequency components of recent wireless / mobile communication devices The trend is to change. As the manufacturing cost of MMIC increases mainly in proportion to its size, reducing the size of MMIC is the biggest problem in MMIC.

On the other hand, the microwave frequency mixer is the most useful part of the RF components of the transmitting and receiving terminals, and modulates or mixes a small RF signal into a LO signal having a large signal size, and thus the sum and difference between the RF signal and the LO signal frequency ( That is, the device converts an intermediate frequency signal (Intermediate Frequency, hereinafter IF) or a signal having frequency components of a product. The receiver uses a down conversion mixer that converts the RF signal into an IF signal, and the up converter uses an up conversion mixer that converts the IF signal into an RF signal.

In general, the required characteristics of the microwave frequency mixer used at the receiving end are 1) low noise characteristics, 2) high gain, 3) good linearity due to low cross-modulation distortion and low intermodulation distortion, and so on. ) Excellent signal isolation between the input and output terminals of the mixer, 5) low production cost and small size, and 6) low power consumption. The demand for such characteristics is that a small capacity capacitor is used to reduce the weight of the mobile terminal. Therefore, the use of low power consumption components becomes essential to increase the usage time of the mobile phone. In order to manufacture a terminal, it is necessary to reduce the size of the parts used. In addition, as the number of mobile telephone subscribers increases, there is a need for terminals having better transmission and reception characteristics (especially low noise characteristics and high linearity).

Frequency mixers are classified into single-ended mixers and mixers of balanced structure, and the mixers of balanced structure are divided into single balanced mixers and dual balanced mixers.

1 is a circuit diagram of a frequency mixer of a dual balance structure, the configuration and operation principle of which will be described next. LO signals LO + and LO- are complementarily applied to the gates of transistors 106 and 112 and transistors 108 and 110, respectively, and complementary RF signals RF + and RF- are transistors 114. , 116 respectively. The IF signals are complementarily drawn from the transistors 106 and 110 and the drain terminals of the transistors 108 and 112.

The mixer of the dual balance structure has an excellent linearity due to the improved spurious response due to its structural characteristics, and has the advantage of having a simple matching circuit.However, many elements are used in the circuit configuration to increase the size of the circuit. It has the disadvantage of using a large, relatively large power consumption. In addition, since many active elements are used at the input stage, the noise characteristics are high.

On the other hand, a mixer having a single output structure is divided into a mixer using a single transistor and a mixer composed of a cascode type, and a mixer having a cascode structure shows excellent performance in terms of separation between terminals and gain.

2 is a circuit diagram of a mixer of a cascode structure in which an LO signal is applied to the gate of the transistor 204, an RF signal is applied to the gate of the transistor 202, and an IF signal is drawn out of the drain of the transistor 204. It is configured to be. In the figure, the capacitors 203 and 204 are capacitors for local oscillator signal input and capacitors for high frequency input, respectively.

The mixer of such single output cascode structure uses relatively low power consumption due to the small size of the circuit due to the simple structure, but exhibits inferior performance compared to the mixer of the balanced structure in terms of linearity. A mixer usually has a low noise characteristic compared to a mixer having a balanced structure by configuring the input stage as a common source structure.

Therefore, it is difficult to satisfy the above-mentioned characteristics of the microwave frequency mixer used in the mobile communication device with the mixer having the balance structure and the single output cascode structure. A mixer was needed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is a frequency for MMIC operating in an RF frequency range with low power consumption, low noise characteristics, high gain and excellent signal separation between terminals and small size. The purpose is to provide a mixer.

1 is a circuit diagram of a frequency mixer of a dual balance structure.

2 is a circuit diagram of a mixer of the cascode structure.

3 is a block diagram of a frequency mixer according to the present invention.

4 is an internal circuit diagram of the mixer core circuit of FIG. 3 according to the present invention;

* Description of the main parts of the drawing

400: cascode type input unit

410: gate ground type amplifier

420: output matching part of the push pull structure

430: gate bias circuit

According to an aspect of the present invention, there is provided a frequency mixer, including: first and second matching circuits configured to receive a local oscillator signal and a high frequency signal, respectively; A frequency core circuit unit which receives the frequency signals outputted from the first and second matching circuit units, mixes them, and converts them into intermediate frequency signals having new frequency components; And a low band filtering circuit unit for low band filtering the intermediate frequency signal output from the frequency core circuit unit to output a final intermediate frequency signal, wherein the frequency core circuit unit is respectively output from the first and second matching circuit units. Input means in the form of a cascode for receiving a local oscillator signal and said high frequency signal; Amplifying means for outputting said complementary intermediate frequency signal after performing an amplifying operation in response to said local oscillator signal and said high frequency signal from said input means; And an output matching means for receiving the complementary intermediate frequency signal from the amplifying means, removing an in-phase signal, mixing frequencies, and outputting the mixed frequency to the low band filtering circuit portion.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. do.

3 is a block diagram of a frequency mixer according to the present invention.

As shown in the figure, the frequency mixer of the present invention receives and mixes the matching circuits 301 and 302 that receive the LO signal and the RF signal, respectively, and the frequency signals output from the matching circuits 301 and 302, respectively. The mixer core circuit 303 converts and outputs a signal having a component, and the low band filter 304 for low band filtering the frequency signal output from the mixer core circuit 303 and outputting the IF signal as an IF signal. Here, in the case of a down conversion mixer, the LO signal frequency and the IF signal frequency are significantly separated so that the LO signal can be easily removed using a low band filter 304 having a small size and a simple circuit.

4 is an internal circuit diagram of the mixer core circuit portion according to the present invention.

Referring to FIG. 4, the mixer core circuit unit according to the present invention has a cascode input unit 400 receiving LO and RF signals from the matching circuits 301 and 302, and different gates for generating IF complementary signals. A gate ground amplifier having a width 410, an output matcher 420 having a push pull structure for improving the overall gain and linearity of the mixer, the input unit 400, and the gate ground amplifier 410 ) And a gate bias circuit 430 generating a gate bias voltage input to the output matching unit 420.

More specifically, the cascode type input unit 400 may include an input terminal 401 receiving an RF signal, an input terminal 401 connected to a gate terminal, a source terminal grounded, and a LO signal. An input terminal 403 and a source terminal connected to the drain terminal of the transistor 402 and a gate terminal connected to the input terminal 403 are applied to each gate terminal of the transistors 402 and 404. The gate bias voltage output from the gate bias circuit 430 is applied. The capacitor 405 is connected between the input terminal 401 and the gate terminal of the transistor 402, and the capacitor 406 is also connected between the input terminal 403 and the gate terminal of the transistor 404. At this time, the capacitor 405 is a so-called high frequency input capacitor that blocks a DC current and passes only a high frequency component, and the capacitor 406 is a so-called intermediate frequency input capacitor that blocks a DC current and passes only an intermediate frequency component.

In addition, the gate ground voltage amplifier 410 has a source bias voltage connected to a drain terminal of the transistor 402 and a drain terminal of the transistor 404, and output from the gate bias circuit 430 to a common gate terminal. The transistors 411 and 412 to be applied, and the ground capacitor 413 connected between the gate terminal and the ground power supply terminal of the transistor 411, the drain bias voltage (Vdd1) is connected to the inductor (414, 415) Through the drain terminals of the transistors 411 and 412, respectively.

Finally, the output matcher 420 of the push pull structure includes a transistor 421 having a drain terminal of the transistor 412 connected to a gate terminal and a drain bias voltage Vdd2 applied to the drain terminal, and a transistor; The drain terminal of the 411 is connected to the gate terminal and the source terminal is connected to the ground power supply terminal 422 and the output terminal 423 for outputting the IF signal, the source terminal and the transistor ( An output terminal 423 is connected to the drain terminal of 422. A capacitor 424 is connected between the output terminal 423, the source terminal of the transistor 421, and the drain terminal of the transistor 422. The capacitor 425 is connected between the drain terminal of the transistor 412 and the gate terminal of the transistor 421, and the capacitor 426 is connected between the drain terminal of the transistor 411 and the gate terminal of the transistor 422. do.

At this time, the transistor 402 is biased in the linear region and the other transistors 404, 412, and 411 are saturated in the saturation region by the gate bias circuit 430 and the drain bias voltage Vdd1.

The principle of operation of the frequency mixer according to the present invention is described next.

The LO signal is applied to the gate terminal of the transistor 404 and the RF signal is applied to the gate terminal of the transistor 402. IF signals complementary to each other are drawn from the drain terminals of the transistors 412 and 411 and applied to the gate terminals of the transistors 421 and 422 of the output matching unit 420, respectively, so that the source of the transistor 421 and the transistor 422 are applied. The drain of is converted to the same phase at the connected portion and summed and outputted.

In detail, the RF signal applied to the gate terminal of the transistor 402 is amplified and then output from the drain terminal of the transistor 402 to the source terminal of the transistor 404 and input to the gate terminal of the transistor 404. The LO signal changes the operating point of transistor 402 coupled to the source terminal of transistor 404. That is, when a LO signal having a positive period is input to the gate terminal of the transistor 404, the operating point of the transistor 402 moves to a saturation region having a large transconductance, thereby greatly amplifying the input RF signal. When a LO signal having a negative period is input to the gate terminal of, the operating point of the transistor 402 moves to a saturation region having a small transconductance, thereby amplifying the input RF signal small, thereby mixing the RF signal with the LO signal. At this time, the RF signal at the drain terminal of the transistor 404 and the RF signal at the drain terminal of the transistor 402 are in phase with each other, whereas the LO signal at the drain terminal of the transistor 404 and the transistor 402 are different from each other. The LO signal at the drain end is reversed in phase. Accordingly, among the signals coming to the drain terminals of the transistors 404 and 402, the IF signal determined by the product of the RF signal and the LO signal is also reversed in phase. The IF signals drawn from the drain terminals of the transistors 404 and 402, respectively, are different in size because the transistor 404 acts as a gate grounding amplifier for the IF signal. The gate-grounded transistors 412 and 411 are adjusted by adjusting the gate widths of the gate-grounded transistors 412 and 411 in order to make IF signals having different magnitudes and opposite phases into complementary signals having the same magnitude and opposite phases. By adjusting the amplification factor of, IF signals complementary to each other are extracted from the drain terminals of the transistor 412 and the transistor 411.

The transistors 421 and 422 of the output matching unit 420 of the push-pull structure remove the signals input in phase and add the complementary signals to each other to increase their magnitude, thereby simultaneously improving gain and linearity. Perform. Therefore, RF signals input in phase are effectively attenuated, and IF signals, which are complementary signals, are amplified to increase the gain of the mixer as a whole.

In addition, the frequency mixer circuit of the present invention is configured such that the LO signal and the RF signal are applied to the gate terminals of the different transistors 404 and 402, respectively, so that the signal separation between the input signals is excellent, and the RF signal is a source ground type. The input noise figure is also improved by being configured to be applied to the gate of transistor 402.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

The present invention made as described above, the output of the push-pull structure for improving the overall gain and linearity of the cascode type input unit, the gate grounding amplifier and the frequency mixer configured to have different gate widths to generate the IF complementary signal It is composed of matching parts, and has an excellent effect of realizing a low power consumption, low noise characteristics, high gain, excellent signal separation between terminals, and a small sized frequency mixer.

Claims (13)

In the frequency mixer, First and second matching circuit sections for receiving a local oscillator signal and a high frequency signal, respectively; A frequency core circuit unit which receives the frequency signals outputted from the first and second matching circuit units, mixes them, and converts them into intermediate frequency signals having new frequency components; And And a low band filtering circuit unit for low band filtering the intermediate frequency signal output from the frequency core circuit unit to output the final intermediate frequency signal. The frequency core circuit unit, Input means in the form of a cascode for receiving the local oscillator signal and the high frequency signal respectively output from the first and second matching circuit portions; Amplifying means for outputting two intermediate frequency signals complementary to each other after performing an amplifying operation in response to the local oscillator signal and the high frequency signal from the input means; And And a push-pull structure output matching means for receiving two mutually complementary intermediate frequency signals from the amplifying means, removing in-phase signals, and then mixing the frequencies and outputting the mixed-frequency signals to the low band filtering circuit portion. Frequency mixer comprising a. The frequency core circuit of claim 1, And a gate bias voltage generating means for generating a gate bias voltage input to said input means, said amplifying means and said output matching means. The method of claim 2, wherein the input means, A high frequency signal input terminal receiving the high frequency signal; A first transistor having a gate terminal connected to the high frequency signal input terminal and a source terminal grounded; A local oscillator signal input terminal receiving the local oscillator signal; And A second transistor having a source terminal connected to the drain terminal of the first transistor and a gate terminal connected to the local oscillator signal input terminal; And a gate bias voltage from said gate bias voltage generating means is applied to each gate terminal of said first and second transistors. The method of claim 3, wherein the input means, A first capacitor connected between the high frequency signal input terminal and a gate terminal of the first transistor; And A second capacitor connected between the local oscillator signal input and a gate of a transistor A frequency mixer comprising a further. The method of claim 3, wherein the amplifying means, A third transistor connected between a drain terminal of the first transistor and a first drain bias voltage terminal and having a gate terminal connected to a ground power supply terminal; And A fourth transistor connected between the drain terminal of the second transistor and the first drain bias voltage terminal and having a gate terminal connected to a ground power supply terminal; And a gate bias voltage from the gate bias voltage generating means is applied to each gate terminal of the third and fourth transistors. The method according to claim 5, wherein the amplifying means, And a grounding capacitor connected between the gate terminal and the ground power supply terminal of the third transistor. The method according to claim 5, wherein the amplifying means, A first inductor connected between the drain terminal of the third transistor and the first drain bias voltage terminal; And A second inductor connected between the drain terminal of the fourth transistor and the first drain bias voltage terminal A frequency mixer comprising a further. The method of claim 5, wherein the amplifying means, And amplification factor by adjusting the gate widths of the third and fourth transistors. The method of claim 5, wherein the output matching means, Fifth and sixth transistors connected in series between a second drain bias voltage terminal and a ground power supply terminal, each gate terminal of which is connected to a drain terminal of the fourth transistor and a drain terminal of the third transistor; And An output terminal connected to a source terminal of the fifth transistor and a drain terminal of the sixth transistor to output the intermediate frequency signal Frequency mixer comprising a. The method of claim 9, wherein the output matching means, A capacitor connected between the source terminal of the fifth transistor and the drain terminal of the sixth transistor and the output terminal Frequency mixer comprising a. The method of claim 9, wherein the first to sixth transistors, A frequency mixer, characterized in that the metal semiconductor field-effect transistor (Metal Semiconductor Field-Effect Transistor). The method of claim 9, wherein the first to sixth transistors, A frequency mixer, characterized in that the metal oxide semiconductor field-effect transistor (MOSFET). The method of claim 9, wherein the first to sixth transistors, A frequency mixer, characterized in that a bipolar transistor (Bipolar transistor).