CN104702219B - A kind of single ended input double balanced passive mixers - Google Patents

Abstract

The invention discloses a double-balanced passive mixer with single-end input, which includes a balun transconductance stage, a passive local oscillator switch and a transimpedance amplifier; the balun transconductance stage adopts a single bias current to realize a dual The transconductance stage circuit with differential current output, the transconductance stage uses the impedance transfer effect of the passive local oscillator switch to pull down the output impedance of the transconductance stage at the local oscillator frequency and constructs a similar AC virtual ground; when the input voltage changes, the transconductance stage The conduits draw currents from the differential output terminals respectively, so as to realize the function of single-channel bias current and dual-channel differential current output. The invention saves half of the transconductance stage current, realizes the same equivalent transconductance, significantly reduces power consumption, and is also suitable for passive mixers in single-end input and differential output applications.

Description

A single-ended input double-balanced passive mixer

technical field

The invention relates to a low-power single-end input double-balanced passive mixer, which belongs to the technical field of mixers.

Background technique

In the RF receiving system, the mixer is responsible for converting the RF signal to the baseband or intermediate frequency band. It is the core module in the receiving chain. considerable share. Therefore, in order to realize the low power consumption of the whole receiving circuit, it is very critical to optimize the power consumption design of the mixer. From the perspective of the structure of the RF front-end, in order to directly couple with the antenna in many cases, the low-noise amplifier of the RF front-end adopts a single-ended input and single-ended output structure. From the point of view of performance and port isolation, the mixer should adopt a differential double-balanced structure. In this case, a single-ended input double-balanced mixer is required to match the LNA. A more common way is to connect a conventional fully differential mixer into a pseudo-differential way. However, from the perspective of power consumption, the pseudo-differential way wastes the bias current of one of the transconductance branches, which affects the efficiency.

Contents of the invention

Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a single-ended input double-balanced passive mixer, which saves half of the transconductance stage current, realizes the same equivalent transconductance, and significantly reduces Power consumption, while suitable for single-ended input, passive mixer for differential output applications.

Technical solution: In order to achieve the above object, the technical solution adopted in the present invention is: a single-ended input double-balanced passive mixer, including a balun transconductance stage, a passive local oscillator switch and a transimpedance amplifier; the transconductance The stage is responsible for converting the input RF voltage into RF current; the passive local oscillator switch performs frequency conversion on the RF current; the transimpedance amplifier is responsible for converting the intermediate frequency current into the output intermediate frequency voltage, and the balun transconductance stage adopts a single bias The current realizes the transconductance stage circuit with dual differential current output. The transconductance stage uses the impedance transfer effect of the passive local oscillator switch to pull down the output impedance of the transconductance stage at the local oscillator frequency and constructs a similar AC virtual ground; when the input voltage When changing, the transconductor draws current from the differential output end respectively, realizing the function of single-channel bias current and dual-channel differential current output.

The balun transconductance stage includes a first transconductance amplifier (A1), first, second and third NMOS transistors, a first PMOS transistor, the input voltage is connected to the gate of the third NMOS transistor (MN3), and the third NMOS transistor (MN3) The source of the tube (MN3) is connected to the drain of the second NMOS tube (MN2); the source of the second NMOS tube (MN2) is grounded, and the gate is connected to the gate of the first NMOS tube (MN1); the first NMOS tube The source of (MN1) is grounded, and the gate and drain are connected to the negative terminal of the reference current source, and the positive terminal of the reference current source is connected to the power supply; the drain of the third NMOS transistor (MN3) is connected to the first PMOS transistor (MP1) Drain, the source of the first PMOS transistor (MP1) is connected to the power supply, and the gate is connected to the output terminal of the first transconductance amplifier (A1); the negative input terminal of the first transconductance amplifier (A1) is connected to the reference voltage, and the positive The input terminal is connected to the positive terminal of the first resistor (R1), and the negative terminal of the first resistor (R1) is connected to the drain of the first PMOS transistor (MP1); the positive terminal of the second resistor (R2) is connected to the first transconductance amplifier ( A1) is connected to the positive input terminal, and the negative terminal of the second resistor (R2) is connected to the gate of the third NMOS transistor (MN3).

The passive local oscillator switch includes first and second capacitors; the positive end of the first capacitor (C1) is connected to the drain of the third NMOS transistor (MN3), and the negative end is connected to the drain of the second PMOS transistor (MP2). source and the source of the third PMOS transistor (MP3); the positive end of the second capacitor (C2) is connected to the source of the third NMOS transistor (MN3), and the negative end is connected to the source of the fourth PMOS transistor (MP4) and The source of the fifth PMOS transistor (MP5).

The transimpedance amplifier comprises a second transconductance amplifier (A2), the drain of the second PMOS transistor (MP2) and the drain of the fourth PMOS transistor (MP4) are connected to the negative input of the second transconductance amplifier (A2) end, the drain of the third PMOS transistor (MP3) and the drain of the fifth PMOS transistor (MP5) are connected to the positive input of the second transconductance amplifier (A2); the second transconductance amplifier (A2) and the fifth PMOS transistor The gate of (MP5) is connected to the negative pole of the local oscillator signal, and the grids of the third PMOS transistor (MP3) and the fourth PMOS transistor (MP4) are connected to the positive pole of the local oscillator signal; the positive terminal of the third resistor (R3) is connected to the third capacitor ( The positive terminal of C3) is connected to the positive input terminal of the second transconductance amplifier (A2), and the negative terminal of the third resistor (R3) and the negative terminal of the third capacitor (C3) are connected to the negative output of the second transconductance amplifier (A2). terminal; the positive terminal of the fourth resistor (R4) and the positive terminal of the fourth capacitor (C4) are connected to the negative input terminal of the second transconductance amplifier (A2), and the negative terminal of the fourth resistor (R4) is connected to the fourth capacitor (C4) ) is connected to the positive output terminal of the second transconductance amplifier (A2).

Beneficial effects: Compared with the prior art, the single-ended input double-balanced passive mixer provided by the present invention has the following effects:

Since the balun transconductance stage uses a single bias current to realize a transconductance stage circuit with dual differential current output, the transconductance stage uses the impedance transfer effect of the passive local oscillator switch to pull down the transconductance at the local oscillator frequency. Level output impedance and structure similar to AC virtual ground; when the input voltage changes, the transconductor pulls current from the differential output end respectively to realize the function of single-channel bias current and dual-channel differential current output. The PMOS current source and the NMOS current source are connected in series respectively, and the impedance change effect of the passive mixing switch is used to pull down the output impedance of the transconductance stage at the local oscillator frequency and construct an approximate AC virtual ground. The change of the input voltage will cause the transconductance The current changes, and because the current flowing into the power supply and ground of the transconductance stage is fixed, and the impedance of the source and drain of the transconductance to the local oscillator switch is low enough, the radio frequency current generated by it is injected into the local oscillator switch stage, its The source and drain currents are equal in magnitude and opposite in phase. Compared with the traditional differential structure with the same transconductance value, its bias current can be reduced by half.

It can be known from the above that the present invention is suitable for passive mixers in single-ended input and differential output applications. The mixer uses a single bias current to realize the effect of dual differential current output, saves half of the transconductance stage current, realizes the same equivalent transconductance, and significantly reduces power consumption.

Description of drawings

Fig. 1 is the low power consumption single-ended input double-balanced passive mixer circuit diagram of the present invention;

Fig. 2 is the low power consumption single-ended input double-balanced passive mixer conversion gain curve of the present invention with input frequency;

detailed description

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

A single-ended input double-balanced passive mixer, as shown in Figure 1, the mixer is composed of a balun transconductance stage, a local oscillator switch and a transimpedance amplifier; it is different from the traditional passive mixer in terms of functional modules The frequency converter is consistent: the transconductance stage is responsible for converting the input radio frequency voltage into radio frequency current; the passive local oscillator switch performs frequency conversion on the radio frequency current; the transimpedance amplifier is responsible for converting the intermediate frequency current into the output intermediate frequency voltage. The balun transconductance stage adopts a single bias current to realize a transconductance stage circuit with dual differential current output. The transconductance stage uses the impedance transfer effect of the passive local oscillator switch to pull down the transconductance stage at the local oscillator frequency. The output impedance and structure are similar to the AC virtual ground; when the input voltage changes, the transconductors pull currents from the differential output terminals respectively, realizing the function of single-channel bias current and dual-channel differential current output.

The balun transconductance stage includes a first transconductance amplifier (A1), first, second and third NMOS transistors, a first PMOS transistor, the input voltage is connected to the gate of the third NMOS transistor (MN3), and the third NMOS transistor (MN3) The source of the tube (MN3) is connected to the drain of the second NMOS tube (MN2); the source of the second NMOS tube (MN2) is grounded, and the gate is connected to the gate of the first NMOS tube (MN1); the first NMOS tube The source of (MN1) is grounded, and the gate and drain are connected to the negative terminal of the reference current source, and the positive terminal of the reference current source is connected to the power supply; the drain of the third NMOS transistor (MN3) is connected to the first PMOS transistor (MP1) Drain, the source of the first PMOS transistor (MP1) is connected to the power supply, and the gate is connected to the output terminal of the first transconductance amplifier (A1); the negative input terminal of the first transconductance amplifier (A1) is connected to the reference voltage, and the positive The input terminal is connected to the positive terminal of the first resistor (R1), and the negative terminal of the first resistor (R1) is connected to the drain of the first PMOS transistor (MP1); the positive terminal of the second resistor (R2) is connected to the first transconductance amplifier ( A1) is connected to the positive input terminal, and the negative terminal of the second resistor (R2) is connected to the gate of the third NMOS transistor (MN3).

The passive local oscillator switch includes first and second capacitors; the positive end of the first capacitor (C1) is connected to the drain of the third NMOS transistor (MN3), and the negative end is connected to the drain of the second PMOS transistor (MP2). source and the source of the third PMOS transistor (MP3); the positive end of the second capacitor (C2) is connected to the source of the third NMOS transistor (MN3), and the negative end is connected to the source of the fourth PMOS transistor (MP4) and The source of the fifth PMOS transistor (MP5).

The transimpedance amplifier comprises a second transconductance amplifier (A2), the drain of the second PMOS transistor (MP2) and the drain of the fourth PMOS transistor (MP4) are connected to the negative input of the second transconductance amplifier (A2) end, the drain of the third PMOS transistor (MP3) and the drain of the fifth PMOS transistor (MP5) are connected to the positive input of the second transconductance amplifier (A2); the second transconductance amplifier (A2) and the fifth PMOS transistor The gate of (MP5) is connected to the negative pole of the local oscillator signal, and the grids of the third PMOS transistor (MP3) and the fourth PMOS transistor (MP4) are connected to the positive pole of the local oscillator signal; the positive terminal of the third resistor (R3) is connected to the third capacitor ( The positive terminal of C3) is connected to the positive input terminal of the second transconductance amplifier (A2), and the negative terminal of the third resistor (R3) and the negative terminal of the third capacitor (C3) are connected to the negative output of the second transconductance amplifier (A2). terminal; the positive terminal of the fourth resistor (R4) and the positive terminal of the fourth capacitor (C4) are connected to the negative input terminal of the second transconductance amplifier (A2), and the negative terminal of the fourth resistor (R4) is connected to the fourth capacitor (C4) ) is connected to the positive output terminal of the second transconductance amplifier (A2).

As shown in Figure 2, it is the conversion gain curve of the low-power single-ended input double-balanced passive mixer of the present embodiment, and its local oscillator frequency is 1GHz; The conversion gain is about 24dB.

It can be known from the above that the innovation of this embodiment is mainly reflected in the design of the transconductance stage. Traditional differential transconductance stages consist of separate differential branches whose output RF currents have opposite polarities and are respectively injected into the differential branches of the local oscillator switch. In order to ensure bandwidth and noise performance, the bias current of the transconductance stage occupies a large proportion in the mixer, so if the current of the transconductance stage can be reduced, the overall power consumption of the mixer can be significantly reduced. The present invention proposes a transconductance level circuit that adopts a single-way bias current to realize dual-way differential current output; the circuit connects a PMOS current source and an NMOS current source in series above and below an NMOS transconductor, and utilizes the impedance of a passive mixing switch The effect of the change is to pull down the output impedance of the transconductance stage at the local oscillator frequency and construct an approximate AC virtual ground. The change of the input voltage will cause the change of the transconductance current, and the current flowing into the power supply and the ground due to the transconductance stage is fixed, and The impedance of the source and drain of the transconductor looking into the local oscillator switch is low enough, so the RF current generated by it is injected into the local oscillator switch stage, and the source and drain currents are equal in magnitude and opposite in phase. In a passive mixer, the transconductance stage typically accounts for the vast majority of the current consumption, and its bias current can be reduced by half compared to a traditional differential structure with the same transconductance value. That is, the present invention saves half of the transconductance stage current and significantly reduces the overall power consumption.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.

Claims (3)

1. a kind of single ended input double balanced passive mixers, including balun transconductance stage, passive local oscillator switch and trans-impedance amplifier； It is radio-frequency current that the transconductance stage, which is responsible for input radio frequency photovoltaic conversion,；Passive local oscillator switch carries out frequency conversion work to the radio-frequency current With；Trans-impedance amplifier is then responsible for electric current of intermediate frequency changing into output voltage of intermediate frequency, it is characterised in that：The balun transconductance stage is used Single channel bias current realizes the transconductance stage circuit of two-way difference current output, and the impedance that the transconductance stage is switched using passive local oscillator is removed Shifting is acted on, and transconductance stage output impedance is dragged down at local frequency and similar exchange virtual earth is constructed；When input voltage changes, mutual conductance Pipe realizes that single channel bias current realizes the function of two-way difference current output respectively from difference output end pull electric current；The bar Human relations transconductance stage includes the first trsanscondutance amplifier（A1）, first, second, third NMOS tube, the first PMOS, input voltage connects the 3rd NMOS tube（MN3）Grid, the 3rd NMOS tube（MN3）Source electrode connect the second NMOS tube（MN2）Drain electrode；Second NMOS tube （MN2）Source ground, and grid connects the first NMOS tube（MN1）Grid；First NMOS tube（MN1）Source ground, and grid Pole and drain electrode connect the negative terminal of reference current source, the positive termination power of reference current source；3rd NMOS tube（MN3）Drain electrode connect first PMOS（MP1）Drain electrode, the first PMOS（MP1）Source electrode connect power supply, and grid connects the first trsanscondutance amplifier（A1）It is defeated Go out end；First trsanscondutance amplifier（A1）Negative input termination reference voltage, and positive input termination first resistor（R1）Anode, One resistance（R1）Negative terminal connect the first PMOS（MP1）Drain electrode；Second resistance（R2）Anode and the first trsanscondutance amplifier （A1）Positive input terminal be connected, second resistance（R2）Negative terminal and the 3rd NMOS tube（MN3）Grid be connected.

2. single ended input double balanced passive mixers according to claim 1, it is characterised in that：The passive local oscillator switch Including first, second electric capacity；First electric capacity（C1）Anode connect the 3rd NMOS tube（MN3）Drain electrode, and negative terminal connects second PMOS（MP2）Source electrode and the 3rd PMOS（MP3）Source electrode；Second electric capacity（C2）Anode connect the 3rd NMOS tube （MN3）Source electrode, and negative terminal connects the 4th PMOS（MP4）Source electrode and the 5th PMOS（MP5）Source electrode.

3. single ended input double balanced passive mixers according to claim 2, it is characterised in that：The trans-impedance amplifier bag Include the second trsanscondutance amplifier（A2）, second PMOS（MP2）Drain electrode and the 4th PMOS（MP4）Drain electrode connect second across Lead amplifier（A2）Negative input end, the 3rd PMOS（MP3）Drain electrode and the 5th PMOS（MP5）Drain electrode connect the second mutual conductance Amplifier（A2）Positive input terminal；Second trsanscondutance amplifier（A2）With the 5th PMOS（MP5）Grid connect local oscillation signal negative pole, 3rd PMOS（MP3）With the 4th PMOS（MP4）Grid connect local oscillation signal positive pole；3rd resistor（R3）Anode and the 3rd Electric capacity（C3）The trsanscondutance amplifier of positive termination second（A2）Positive input terminal, 3rd resistor（R3）Negative terminal and the 3rd electric capacity（C3） Negative terminal connect the second trsanscondutance amplifier（A2）Negative output terminal；4th resistance（R4）Anode and the 4th electric capacity（C4）Positive termination Second trsanscondutance amplifier（A2）Negative input end, the 4th resistance（R4）Negative terminal and the 4th electric capacity（C4）Negative terminal connect the second mutual conductance Amplifier（A2）Positive output end.