CN114499414B - A Bidirectional Active Mixer Based on Complementary MOS Transistor - Google Patents

Abstract

The invention belongs to the technical field of bidirectional transceivers, and particularly provides a bidirectional active mixer based on a complementary MOS (metal oxide semiconductor) tube, which is used for solving the problems that the conventional passive annular mixer can introduce larger loss, needs larger local oscillation signal and the like in a link. The invention connects PMOS tube and NMOS tube in parallel to form a MOS tube pair, and four MOS tube pairs form a double-balanced active mixer structure; in each MOS tube pair, the source electrode of the NMOS is connected with the drain electrode of the PMOS to be connected with a radio frequency signal, the drain electrode of the NMOS is connected with the source electrode of the PMOS to be connected with an intermediate frequency signal, and the grid electrode of the NMOS is applied with an inverted local oscillation signal; the radio frequency signal is changed into an intermediate frequency signal to be output from the source electrode to the drain electrode of the NMOS, and the intermediate frequency signal is changed into the radio frequency signal to be output from the source electrode to the drain electrode of the PMOS, so that the bidirectional mixing is realized, and the frequency conversion mode is switched without additional switch control; meanwhile, the invention has the structure of the common gate amplifier and positive feedback, can provide gain while realizing bidirectional mixing, and improves the link performance.

Description

A Bidirectional Active Mixer Based on Complementary MOS Transistor

technical field

The invention belongs to the technical field of bidirectional transceivers, relates to a mixer as a key module in a radio frequency link, and specifically provides a bidirectional active mixer based on complementary MOS transistors.

Background technique

With the development of wireless communication technology and the application of phased array technology, two-way transceiver technology is gradually applied to radio frequency chips; The input matching network is shared, the active transistor part is combined and laid out, and other modules such as the driver amplifier are also designed to share the matching network and support the structure of bidirectional signal transmission, and finally become a link, which only requires half the original area, so it can be applied to A phased array chip with a higher level of integration.

As a key module in the radio frequency link, the mixer realizes the conversion between the intermediate frequency signal and the radio frequency signal; in the design of the mixer module, gain is a very important indicator, and a high gain mixer can better drive the next stage, reducing the design pressure on the amplifier. In the design of a two-way mixer, it is necessary to use a mixer that can not only complete the up-conversion of the intermediate frequency signal to the radio frequency signal, but also reversely convert the radio frequency signal into the intermediate frequency signal for down-conversion.

At present, most common active mixers are of Gilbert architecture, which requires a signal to be input from the gate of the transconductance MOS transistor and a signal to be output from the drain of the switch transistor, but the signal cannot be transmitted from the MOS transistor after inversion. Gate output, so it is usually not possible to make a bidirectional structure. The common mixers that can be used in two-way receivers are mainly passive ring mixers. The schematic diagram of the circuit is shown in Figure 1; where the drains and sources of M1-M4 are respectively biased at the same potential , one end is connected to the radio frequency signal, the other end is connected to the intermediate frequency signal, the gate is controlled by the local oscillator signal, and the bias is near the threshold voltage; since the voltage between the source and the drain is the same, no DC current flows, and no external power supply is required, so it is called wireless. source mixer. In this structure, due to the structural symmetry of the source and drain of the MOS transistor, when the signal potentials at both ends are the same, they can be approximately regarded as equivalent, and the signal can be from the source to the drain or from the drain To the source; therefore, under the action of the local oscillator signal, the signal can not only up-convert the intermediate frequency signal to the RF signal, but also down-convert the RF signal to the intermediate frequency signal in the reverse direction, so as to realize two-way mixing.

However, although the above-mentioned passive ring mixer can realize bidirectional signal conversion, there are still many problems, and the corresponding disadvantages are as follows:

1) The passive ring mixer has a large loss: the passive ring mixer has no active amplification structure, so it can only cause signal attenuation. If only the MOS tube in the mixer is regarded as an ideal lossless switch, The loss is at least 4dB; due to the discontinuity of the MOS tube switching state and the resistivity of the MOS tube in the conduction state, the core part of the passive ring mixer usually loses more than 6dB. Combined with the matching network of the front and rear stages, the loss will only More; therefore, the above-mentioned passive ring mixer will cause the gain of the entire link to be greatly reduced, affecting the overall communication performance;

2) The passive ring mixer requires a larger local oscillator signal: due to the high loss characteristics of the passive ring mixer, it needs to be optimized in the direction of low loss during the design process, which means using a larger MOS tube , the corresponding parasitic capacitance also increases; therefore, the mixer needs a larger local oscillator signal to drive the switching conversion of the mixer, resulting in an increase in the output power demand of the local oscillator link, and at the same time increases the overall power of the chip. consumption.

Contents of the invention

The purpose of the present invention is to provide a bidirectional active mixer based on complementary MOS transistors to solve the problems that the existing passive ring mixer will introduce a large loss in the link and require a large local oscillator signal. The present invention proposes a new structure, which connects complementary PMOS transistors and NMOS transistors in parallel to form an active mixer with switching stages, which can realize bidirectional signal frequency conversion through complementary characteristics, and does not require additional switch control signals to switch the mixer In the frequency state, the connection structure of the common gate provides positive gain and reduces the dependence on the power of the local oscillator, thereby realizing a bidirectional mixer with gain, which helps to improve the performance of the bidirectional transceiver.

To achieve the above object, the technical solution adopted in the present invention is:

A bidirectional active mixer based on complementary MOS tubes, characterized in that it includes: switch tubes, transformers transformer1 and transformer2, and tail current source M9; wherein,

The switch tubes include: NMOS tubes M1, M4, M5, M8 and PMOS tubes M2, M3, M6, M7, the drain of the NMOS tube M1, the source of the PMOS tube M2, the drain of the NMOS tube M5 and the PMOS tube The sources of the tube M6 are all connected, the source of the PMOS tube M3, the drain of the NMOS tube M4, the source of the PMOS tube M7, and the drain of the NMOS tube M8 are all connected; the NMOS tube M1, the PMOS tube M3, The gates of the PMOS transistor M6 and the NMOS transistor M8 are connected to the positive local oscillator signal LO+, the gates of the PMOS transistor M2, the NMOS transistor M4, the NMOS transistor M5 and the PMOS transistor M7 are connected to the negative local oscillator signal LO-; the gates of the NMOS transistor M1 The source, the drain of the PMOS transistor M2, the source of the NMOS transistor M3 are all connected to the drain of the PMOS transistor M4, the drain of the PMOS transistor M6, the source of the NMOS transistor M5, the drain of the PMOS transistor M7, the NMOS The sources of the tube M8 are connected;

The primary coil of the transformer transformer1 is connected to the intermediate frequency signal (IF+, IF-), the secondary coil of the transformer transformer1 is connected between the drains of the NMOS transistor M1 and the NMOS transistor M8, and the center tap is connected to the voltage V _dd ; the primary coil of the transformer transformer2 is connected to For radio frequency signals (RF+, RF-), the secondary coil of the transformer transformer2 is connected between the sources of the MOS transistor M2 and the MOS transistor M3, and the drain of the tail current source M9; the gate of the tail current source M9 is connected to the bias voltage V _bias1 , the source is grounded.

Further, the structural dimensions of the NMOS transistors M1 , M4 , M5 and M8 are the same, and the structural dimensions of the PMOS transistors M2 , M3 , M6 and M7 are the same.

Further, the bidirectional active mixer satisfies the conditions:

Among them, V _dd is the power supply voltage, V _LO,dc is the DC level of the local oscillator signal connected to the gates of the MOS transistors M1-M8, V _thp is the threshold voltage of the PMOS transistor, V _thn is the threshold voltage of the NMOS transistor, V _{ds, M9} is the source-drain voltage difference of the tail current source M9.

Further, the tail current source M9 adopts an NMOS transistor.

The beneficial effects of the present invention are:

The invention provides a bidirectional active mixer based on complementary MOS transistors, which improves the traditional double-balanced active mixer, and can realize both up-conversion and reverse down-conversion, thereby achieving the effect of bidirectional mixing , can greatly reduce the chip area when applied to a two-way radio frequency transceiver; and, the present invention has a common gate amplifier and a positive feedback structure, compared with a passive ring mixer, it can provide gain while realizing two-way mixing, and improve link performance.

More specifically, the bidirectional active mixer of the present invention has the following advantages:

1. The present invention adopts a bidirectional active mixer based on complementary MOS tubes, and connects PMOS tubes and NMOS tubes in parallel to form a pair of MOS tubes, and a total of four MOS tube pairs form a double-balanced active mixer structure; each The MOS tube is centered, the source of the NMOS is connected to the drain of the PMOS to access the RF signal, the drain of the NMOS is connected to the source of the PMOS to access the intermediate frequency signal, and the gate is applied with an inverted local oscillator signal; the RF signal is from the corresponding transformer Entering and passing through the source of the NMOS to the drain becomes an intermediate frequency signal output, and the intermediate frequency signal enters from the corresponding transformer and passes through the source of the PMOS to the drain to become a radio frequency signal output, which realizes two-way mixing;

2. In the present invention, by introducing a tail current source, both the NMOS tube and the PMOS tube are biased near the threshold voltage, so there is no need for additional switch control to switch the frequency conversion mode, and the up- and down-conversion are both in the same circuit working state;

3. The two-way active mixer of the present invention presents the form of a common grid when it is working, and the gates of the NMOS transistors and PMOS transistors in parallel are applied with anti-phase signals, and positive feedback is introduced to make up for the gain defect of the PMOS transistors, and can be used in Amplify the signal while mixing to improve link performance.

Description of drawings

FIG. 1 is a circuit schematic diagram of a conventional passive ring mixer.

FIG. 2 is a schematic circuit diagram of a bidirectional active mixer based on complementary MOS transistors in the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

This embodiment proposes a bidirectional active mixer based on complementary MOS transistors, which retains the switch part of the traditional Gilbert type active mixer, connects NMOS and PMOS in parallel, and applies an inverting phase to the gate. Vibrate signal, realize the two-way frequency conversion with gain; The circuit schematic diagram of the two-way active mixer based on complementary MOS tube of the present invention is as shown in Figure 2, the mixer switch mainly made of the MOS tube of M1-M8 tube, two transformers transformer1 and transformer2 connected to signal input and output, and tail current source M9; more specifically:

The drain of the NMOS transistor M1, the source of the PMOS transistor M2, the drain of the NMOS transistor M5 are connected to the source of the PMOS transistor M6, the source of the PMOS transistor M3, the drain of the NMOS transistor M4, the PMOS transistor The source of M7 and the drain of NMOS transistor M8 are all connected; the gates of the NMOS transistor M1, PMOS transistor M3, PMOS transistor M6 and NMOS transistor M8 are connected to the positive local oscillator signal LO+, and the PMOS transistor M2, NMOS transistor M4, The gates of the NMOS transistor M5 and the PMOS transistor M7 are connected to the negative local oscillator signal LO-; the source of the NMOS transistor M1, the drain of the PMOS transistor M2, the source of the NMOS transistor M3 are connected to the drain of the PMOS transistor M4, The drain of the PMOS transistor M6, the source of the NMOS transistor M5, the drain of the PMOS transistor M7, and the source of the NMOS transistor M8 are all connected;

The primary coil of the transformer transformer1 is connected to the intermediate frequency signal (IF+, IF-), the secondary coil of the transformer transformer1 is connected between the drains of the NMOS transistor M1 and the NMOS transistor M8, and the center tap is connected to the voltage V _dd ; the primary coil of the transformer transformer2 is connected to For radio frequency signals (RF+, RF-), the secondary coil of the transformer transformer2 is connected between the sources of the MOS transistor M2 and the MOS transistor M3, and the drain of the tail current source M9; the gate of the tail current source M9 is connected to the bias voltage V _bias1 , the source is grounded.

In terms of working principle:

The present invention is mainly composed of a mixer switching tube composed of M1-8 MOS tubes, two transformers transformer1 and transformer2 connecting signal input and output, and a tail current source M9;

The MOS tubes M1-M8 in the circuit shown in Figure 2 are the switching tubes of the mixer, forming a double-balanced mixing structure; among them, M1, M4, M5, and M8 are NMOS tubes, and M2, M3, M6, and M7 are PMOS tubes, NMOS tubes and PMOS tubes are connected in parallel, the source of each pair of NMOS tubes is connected to the drain of the PMOS tube, the drain of the NMOS tube is connected to the source of the PMOS tube, and the gate is applied with an anti-phase local oscillator Signal; the intermediate frequency signal is connected by the transformer transformer1, and the radio frequency signal is connected by the transformer transformer2. The two transformers are connected to the center tap of the secondary coil on the side of the MOS tube M1-M8, respectively connected to the bias V _dd and the tail current source; in the center tap At , the differential signals on both sides cancel, which can be regarded as AC ground, so the bias circuit will not affect the core part of the mixer.

In order for the mixer to achieve up-and-down mixing without switching states, it is necessary to connect the bias voltage of the local oscillator signal of the gate of the MOS transistor to the source of the PMOS transistor and the source of the NMOS transistor. The voltage difference is equal to the threshold of the two MOS transistors. Voltage:

Among them, V _dd is the power supply voltage, V _LO,dc is the DC level of the local oscillator signal connected to the gates of the MOS transistors M1-M8, V _thp is the threshold voltage of the PMOS transistor, V _thn is the threshold voltage of the NMOS transistor, V _{ds, M9} is the source-drain voltage difference of the MOS transistor M9;

Since most of the current CMOS processes, the power supply voltage is greater than the sum of the absolute value of the threshold voltage of the NMOS tube and the PMOS tube, it is necessary to add a tail current source M9 to compensate the voltage difference through the voltage drop of its drain and source, so that Both NMOS tube and PMOS tube can be biased near the switch state; because NMOS has higher carrier mobility, it can provide the same large current while occupying a smaller area than PMOS, so M9 uses NMOS tube; because the two The MOS tubes are all biased near the switching state, and the switching state can be switched by applying a large local oscillator signal to realize frequency mixing.

When the radio frequency signal enters from transformer2, it is connected to the sources of four NMOS transistors, which is equivalent to a common grid amplifier for radio frequency signals. To transformer1 output; due to the reverse connection of the local oscillator signal, when the NMOS tube is turned on, the PMOS tube will also be turned on, and the drain terminal of the PMOS tube is connected to the RF signal. According to the small signal characteristics of the MOS tube, the RF signal will see a resistance value Large small-signal resistance and a small amount of parasitic capacitance, so the radio frequency signal will not pass through the high-impedance PMOS tube but will pass through the NMOS tube; and when both MOS tubes are turned on, the source of the PMOS tube can be down-converted The potential change of the obtained intermediate frequency signal is positively fed back to the radio frequency end, which equivalently increases the gain of the mixer;

In the same way, after the intermediate frequency signal enters from transformer1, it is connected to the sources of four PMOS transistors, which is equivalent to a common grid amplifier for the intermediate frequency signal. The pole is connected to the transformer2 output; the intermediate frequency signal will see high resistance at the NMOS tube, so it will not be fed through from the NMOS tube, and the potential change of the source of the NMOS tube can be positively fed back to the intermediate frequency terminal of the drain when the NMOS tube is turned on. thereby increasing the gain;

In addition, the P-type doped MOS tube has low carrier mobility. In the millimeter wave frequency band, if the parallel NMOS tube and the PMOS tube gate are applied with the same phase local oscillator signal, when the PMOS tube is turned on, the NMOS tube is completely turned off. If it is off, only the PMOS tube participates in the amplification effect, and the active mixer of the PMOS switch tube has no obvious advantage in gain performance compared with the passive ring mixer of the NMOS tube; Pole applies the anti-phase local oscillator signal, and compensates the PMOS gain defect by introducing positive feedback, so that the mixer also has better gain performance in the process of up-conversion.

The above is only a specific embodiment of the present invention. Any feature disclosed in this specification, unless specifically stated, can be replaced by other equivalent or alternative features with similar purposes; all the disclosed features, or All method or process steps may be combined in any way, except for mutually exclusive features and/or steps.

Claims (3)

1. A bidirectional active mixer based on complementary MOS transistors, characterized in that it comprises: switch tubes, transformer transformer1 and transformer2, and tail current source M9; wherein, The switch tubes include: NMOS tubes M1, M4, M5, M8 and PMOS tubes M2, M3, M6, M7, the drain of the NMOS tube M1, the source of the PMOS tube M2, the drain of the NMOS tube M5 and the PMOS tube The sources of the tube M6 are all connected, the source of the PMOS tube M3, the drain of the NMOS tube M4, the source of the PMOS tube M7, and the drain of the NMOS tube M8 are all connected; the NMOS tube M1, the PMOS tube M3, The gates of the PMOS transistor M6 and the NMOS transistor M8 are connected to the positive local oscillator signal LO+, the gates of the PMOS transistor M2, the NMOS transistor M4, the NMOS transistor M5 and the PMOS transistor M7 are connected to the negative local oscillator signal LO-; the gates of the NMOS transistor M1 The source, the drain of the PMOS transistor M2, the source of the NMOS transistor M3 are all connected to the drain of the PMOS transistor M4, the drain of the PMOS transistor M6, the source of the NMOS transistor M5, the drain of the PMOS transistor M7, the NMOS The sources of the tube M8 are connected; The primary coil of the transformer transformer1 is connected to the intermediate frequency signal (IF+, IF-), the secondary coil of the transformer transformer1 is connected between the drains of the NMOS transistor M1 and the NMOS transistor M8, and the center tap is connected to the voltage V _dd ; the primary coil of the transformer transformer2 is connected to For radio frequency signals (RF+, RF-), the secondary coil of the transformer transformer2 is connected between the sources of the NMOS transistor M1 and the NMOS transistor M8, and the center tap is connected to the drain of the tail current source M9; the gate of the tail current source M9 is connected to the bias set the voltage V _bias1 , and the source is grounded; The bidirectional active mixer satisfies the condition:

Wherein, V _dd is the power supply voltage, V _LO,dc is the DC level of the local oscillator signal connected to the gates of the MOS transistors M1-M8, V _thp is the threshold voltage of the PMOS transistor, V _thn is the threshold voltage of the NMOS transistor, V _{ds, M9} is the source-drain voltage difference of the tail current source M9. 2. The bidirectional active mixer based on complementary MOS transistors according to claim 1 is characterized in that, the structural dimensions of said NMOS transistors M1, M4, M5, M8 are the same, and the PMOS transistors M2, M3, M6, M7 The structural dimensions are the same. 3. The bidirectional active mixer based on complementary MOS transistors according to claim 1, wherein the tail current source M9 is an NMOS transistor.

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