Radio frequency mixer with complementary structure

Abstract

The invention discloses a radio frequency mixer with a complementary structure, which comprises four NMOS (N-channel Metal Oxide Semiconductor) transistors, four PMOS (P-channel Metal Oxide Semiconductor) transistors, two resistors, two capacitors and a power supply voltage, the four NMOS transistors and the four PMOS transistors are configured in parallel in a complementary pair form, and the source electrodes of the NMOS transistors and the source electrodes of the PMOS transistors are connected to a differential radio frequency input signal; the resistor is used for providing bias voltage for the transistor and is directly connected with power supply voltage, and the capacitor is used for alternating current coupling and grounding; a local oscillator input signal controls the grid conduction state of the NMOS transistor and the PMOS transistor, and the differential radio frequency input signal is converted into a differential intermediate frequency output signal through the frequency mixing effect. According to the invention, the NMOS transistors and the PMOS transistors are configured in parallel in the form of complementary pairs, the NMOS transistors and the PMOS transistors provide transconductance at the same time, and the loads of the NMOS transistors and the PMOS transistors are favorable for improving the overall gain of the circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit design, and particularly to a radio frequency mixer with a complementary structure. Background Art

[0002] A radio frequency mixer is an indispensable component in modern wireless communication systems, which plays a role in converting frequencies during the signal receiving and transmitting processes; at the receiving end, the mixer down-converts the received high-frequency radio frequency signal (RF) to an intermediate frequency (IF) that is easier to process or directly to a baseband signal; while at the transmitting end, it is responsible for up-converting the modulated intermediate frequency or baseband signal to the required radio frequency for transmission; this conversion process is crucial for achieving a high-performance and highly reliable communication link and is widely used in cellular telephone networks, satellite communications, radar systems, and various wireless connection technologies.

[0003] Currently, an active mixer structure widely used is based on the Gilbert cell design; by using differential pair transistors to amplify the input radio frequency signal and a switch transistor array controlled by a local oscillator (LO) to perform the mixing operation; finally, through a load composed of a parallel combination of a resistor and a capacitor, an intermediate frequency output signal is generated; the Gilbert cell can provide relatively high gain, good linearity, and relatively low noise.

[0004] However, the Gilbert cell also has defects. Its gain is limited by the transistor transconductance and load impedance under a given power consumption condition, which not only limits the highest operating frequency but may also result in an overly low output operating point voltage; in addition, since the load needs to pass a direct current static current, a load resistor with an overly large resistance value cannot be used, which further restricts the improvement of the gain.

[0005] Therefore, it is necessary to improve a radio frequency mixer with a complementary structure in the prior art to solve the above problems. Summary of the Invention

[0006] The present invention overcomes the deficiencies of the prior art and provides a radio frequency mixer with a complementary structure, aiming to solve the problems of limited gain, limited highest operating frequency, and overly low output operating point voltage in the Gilbert cell mixer in the prior art.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a radio frequency mixer with a complementary structure, including: four NMOS transistors, four PMOS transistors, two resistors, two capacitors, and a power supply voltage, characterized in that;

[0008] The four NMOS transistors and the four PMOS transistors are configured in parallel in a complementary pair form, and the source electrodes of the NMOS transistors and the PMOS transistors are connected to a differential radio frequency input signal;

[0009] The resistor is used to provide a bias voltage for the transistor and is directly connected to the power supply voltage, and the capacitor is used for AC coupling and grounded;

[0010] The local oscillator input signal controls the gate conduction states of the NMOS transistor and the PMOS transistor, and converts the differential RF input signal into a differential IF output signal through the mixing effect.

[0011] In a preferred embodiment of the present invention, the resistor includes: resistor R1 and resistor R2. Resistor R1 is connected to the differential RF input signal RF_IN+, and resistor R2 is connected to the differential RF input signal RF_IN- and is directly connected to the power supply voltage.

[0012] In a preferred embodiment of the present invention, the capacitor includes: capacitor C1 and capacitor C2. Capacitor C1 is connected to the differential RF input signal RF_IN+, and capacitor C2 is connected to the differential RF input signal RF_IN- and isolates the DC component through grounding.

[0013] In a preferred embodiment of the present invention, the drains of the NMOS transistor and the PMOS transistor form a current path through cross-connection, where the drain of the NMOS transistor is connected to another NMOS transistor, and the drain of the PMOS transistor is connected to another PMOS transistor.

[0014] In a preferred embodiment of the present invention, the local oscillator input signals LO_IN+ and LO_IN- respectively control the gates of the NMOS transistor and the PMOS transistor in the complementary pair, forming a switching operation with opposite phases.

[0015] In a preferred embodiment of the present invention, the differential IF output signals IF_OUT+ and IF_OUT- are respectively output from the drains of the PMOS transistor and the NMOS transistor, and the signal consistency is enhanced through a common-mode interference suppression structure.

[0016] In a preferred embodiment of the present invention, the NMOS transistor and the PMOS transistor in the complementary pair form a differential amplification structure through a shared source connection.

[0017] In a preferred embodiment of the present invention, all the transistors of the mixer adopt a symmetric layout design.

[0018] The present invention solves the defects existing in the background technology, and the present invention has the following beneficial effects:

[0019] (1) The present invention proposes a radio frequency mixer with a complementary structure. By using four NMOS transistors and four PMOS transistors configured in parallel in a complementary pair, combined with resistors to provide bias voltage and capacitors for AC coupling, effective mixing of differential radio frequency input signals is achieved. The drains of the NMOS and PMOS transistors are cross-connected to form a current path. At the same time, the local oscillator input signal controls the on-state of the transistor gates to complete frequency conversion and output differential intermediate frequency signals. In addition, all transistors are designed with a symmetric layout, optimizing the high-frequency response characteristics and reducing the influence of process variations. This technical solution not only improves the gain and switching speed of the mixer, but also enhances signal consistency and anti-interference ability. Compared with the prior art, the performance of the mixer is significantly improved without increasing power consumption.

[0020] (2) In the present invention, the NMOS transistors and PMOS transistors are configured in parallel in a complementary pair. The NMOS transistors and PMOS transistors simultaneously provide transconductance and act as loads for each other. During the mixing process, the drains of the NMOS transistors and PMOS transistors are cross-connected to form a current path. The two types of transistors work simultaneously and act as loads for each other, which helps to improve the overall gain of the circuit. Compared with the prior art, it further achieves the effect of increasing the transconductance to improve the gain without increasing current consumption.

[0021] (3) In the present invention, a current path is formed by cross-connecting the drains of the NMOS transistors and PMOS transistors. The drain of an NMOS transistor is connected to another NMOS transistor, and the drain of a PMOS transistor is connected to another PMOS transistor. This cross-connection method enables the NMOS transistors and PMOS transistors to work better together, forming an effective current loop and improving the mixing efficiency. Compared with the prior art, it further achieves the effects of improving the mixing efficiency and optimizing the circuit performance.

[0022] (4) In the present invention, all transistors are designed with a symmetric layout. This symmetric layout can reduce the influence of process variations on the circuit performance, enabling the circuit to have better consistency and stability during high-frequency operation. At the same time, the symmetric layout also helps to optimize the high-frequency response characteristics and reduce the influence of parasitic parameters. Compared with the prior art, it further achieves the effects of improving the circuit reliability and optimizing the high-frequency performance.

[0023] (5) The present invention controls the gate conduction states of NMOS transistors and PMOS transistors through the local oscillator input signal. The local oscillator input signals LO_IN+ and LO_IN- respectively control the gates of the NMOS transistor and the PMOS transistor in the complementary pair, forming switching operations with opposite phases. This control method enables the NMOS transistor and the PMOS transistor to quickly switch according to the phase change of the local oscillator signal, thereby achieving efficient mixing operation. Compared with the prior art, the effects of improving the mixing accuracy and reducing signal distortion are further achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 is the circuit structure diagram of the preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0027] Many specific details are set forth in the following description in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0028] In the description of the present application, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the protection scope of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Therefore, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0029] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "mounted", "connected", "coupled" shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0030] Application Overview:

[0031] Traditional Gilbert cell active mixers perform well in terms of gain, linearity, and noise suppression, but they also have some inherent limitations; under the power consumption limit, the performance improvement of this circuit is restricted by the transistor transconductance and load impedance, which not only limits the highest operating frequency that the circuit can support but also may cause a drop in the output voltage level; for field-effect transistors, their transconductance, and for bipolar transistors, the current gain, are the key factors determining the gain. These parameters not only depend on the current used but also are related to the physical size of the transistors. However, an overly large transistor size will limit the highest operating frequency that the circuit can reach. Large-size transistors usually come with larger parasitic capacitances, thus slowing down the switching speed.

[0032] Secondly, in order to maintain the necessary DC quiescent current, the selection of the load resistor is strictly restricted. An overly high resistance value will result in insufficient operating point voltage of the output signal, thereby affecting the dynamic range and overall performance of the system.

[0033] To solve the above problems, the present application proposes a novel complementary - structure radio - frequency mixer to solve the above problems, achieve a balance among gain, frequency response, and output level, and optimize the circuit.

[0034] Exemplary device:

[0035] As Figure 1 shown, a complementary - structure radio - frequency mixer includes: a power supply voltage, four NMOS transistors M1, M3, M5, M7 and four PMOS transistors M2, M4, M6, M8, as well as two resistors R1, R2 and two capacitors C1, C2;

[0036] The resistors are used to provide appropriate bias voltages for the transistors;

[0037] The two resistors are connected in parallel, the two resistors are directly connected to the power supply voltage, and the two resistors are respectively connected to a pair of differential radio - frequency input signals;

[0038] The differential radio - frequency input signal is a commonly used signal - transmission method in radio - frequency circuits. It uses a pair of wires to transmit two signals with opposite phases and equal amplitudes. Differential - signal transmission helps reduce electromagnetic radiation. The current directions on the two wires are opposite, and the generated magnetic fields will cancel each other out.

[0039] In one embodiment, specifically, resistor R1 is connected to differential radio - frequency input signal RF_IN +, and resistor R2 is connected to differential radio - frequency input signal RF_IN -;

[0040] The capacitors are used for AC coupling, isolating the DC component, preventing DC current from flowing into the radio - frequency signal path, and allowing AC signals to pass through;

[0041] The two capacitors are connected in parallel, the two capacitors are grounded, and the two capacitors are respectively connected to a pair of differential radio - frequency input signals;

[0042] In one embodiment, specifically, capacitor C1 is connected to differential radio - frequency input signal RF_IN +, and resistor C2 is connected to differential radio - frequency input signal RF_IN -;

[0043] The differential radio - frequency input signals connected by the capacitors are the same as those connected by the resistors.

[0044] The power supply voltage provides the necessary energy for the entire circuit, driving all circuit elements to work properly;

[0045] Grounding provides a reference potential for the circuit, stabilizing the circuit operation.

[0046] The NMOS transistors and PMOS transistors are configured in complementary pairs and are connected in parallel, which can reduce the limitation of the transistor size on the maximum operating frequency of the circuit;

[0047] Four NMOS transistors and four PMOS transistors are configured in parallel in complementary pairs. The sources of the NMOS transistors and the PMOS transistors are connected to a differential radio frequency input signal. The NMOS transistors and the PMOS transistors in the complementary pairs form a differential amplification structure through a shared source connection, which is used to amplify the input radio frequency signal and participate in the mixing process.

[0048] The drains of the NMOS transistors and the PMOS transistors form a current path through cross-connection, where the drain of an NMOS transistor is connected to another NMOS transistor, and the drain of a PMOS transistor is connected to another PMOS transistor.

[0049] The PMOS and NMOS transistors simultaneously provide transconductance and act as loads for each other. A larger transconductance is provided without increasing current consumption, thereby improving the gain of the mixer. The two types of transistors work simultaneously and act as loads for each other. Compared with a resistive load, this load will not form an excessive DC voltage drop due to excessive impedance, which helps to improve the overall gain of the circuit. The amplifier tube in the prior art is implemented with NMOS + PMOS. Since the NMOS and PMOS can use the same static bias, a larger transconductance can be provided without increasing current. The parallel configuration of the NMOS transistors and the PMOS transistors improves the switching speed by reducing parasitic capacitance, and at the same time increases the transconductance without increasing current consumption to improve the gain.

[0050] The local oscillator input signals LO_IN+ and LO_IN- are key signal inputs in the radio frequency mixer circuit, which are used to generate a stable frequency reference signal. The local oscillator input signals LO_IN+ and LO_IN- respectively control the gates of the NMOS transistors and the PMOS transistors in the complementary pairs to form a switching operation with opposite phases.

[0051] During the operation of the mixer, the local oscillator input signal is mixed with the received differential radio frequency input signal to generate intermediate frequency signals IF_OUT+ and IF_OUT-, thereby realizing frequency conversion. The differential intermediate frequency output signals IF_OUT+ and IF_OUT- are respectively output from the drains of the PMOS transistors and the NMOS transistors, and the signal consistency is enhanced through a common-mode interference suppression structure.

[0052] All the transistors of the mixer adopt a symmetric layout design to reduce the influence of process deviation on the circuit performance and optimize the high-frequency response characteristics.

[0053] In one embodiment, the NMOS transistor M1 and the PMOS transistor M2 are in parallel, and the sources of the NMOS transistor M1 and the PMOS transistor M2 are connected to the radio frequency input RF_IN+ through a resistor R1.

[0054] The gate of NMOS transistor M1 is connected to the local oscillator input signal LO_IN-, controlling its conduction and cutoff, thereby realizing signal mixing. The drain of NMOS transistor M1 is connected to NMOS transistor M3, forming a current path;

[0055] The gate of PMOS transistor M2 is connected to the local oscillator input signal LO_IN+, and the drain of PMOS transistor M2 is connected to PMOS transistor M4, forming a current path;

[0056] NMOS transistor M1 and PMOS transistor M2 form a differential pair, amplifying the input radio frequency signal and participating in the mixing process.

[0057] NMOS transistor M5 and PMOS transistor M6 are in parallel. The sources of NMOS transistor M5 and PMOS transistor M6 are connected to the radio frequency input RF_IN- through resistor R2;

[0058] The gate of NMOS transistor M5 is connected to the local oscillator input signal LO_IN+, and the drain of NMOS transistor M5 is connected to NMOS transistor M7, forming a current path;

[0059] The gate of PMOS transistor M6 is connected to the local oscillator input signal LO_IN-, and the drain of PMOS transistor M6 is connected to PMOS transistor M8, forming a current path;

[0060] NMOS transistor M5 and PMOS transistor M6 form a differential pair, amplifying the input radio frequency signal and participating in the mixing process.

[0061] NMOS transistors M1 and M5 output the intermediate frequency signal IF_OUT-, and PMOS transistors M2 and M6 output the intermediate frequency signal IF_OUT+.

[0062] IF_OUT+ and IF_OUT- are differential intermediate frequency output circuits, enhancing the consistency against common mode interference.

[0063] NMOS transistor M3 and PMOS transistor M4 are in parallel. The sources of NMOS transistor M3 and PMOS transistor M4 are connected to the radio frequency input RF_IN+ through capacitor C1. NMOS transistor M3 and PMOS transistor M4 further amplify and mix the RF_IN+ signal;

[0064] The gate of NMOS transistor M3 is connected to the local oscillator input signal LO_IN+, controlling its conduction and cutoff, and jointly completing signal mixing with NMOS transistor M1. The drain of NMOS transistor M3 is connected to capacitor C1;

[0065] The gate of PMOS transistor M4 is connected to the local oscillator input signal LO_IN-, and the drain of PMOS transistor M4 is connected to capacitor C1 to form a current path.

[0066] NMOS transistor M3 and PMOS transistor M4 form a differential pair to amplify the input radio frequency signal and participate in the mixing process.

[0067] NMOS transistor M7 and PMOS transistor M8 are in parallel. The sources of NMOS transistor M7 and PMOS transistor M8 are connected to the radio frequency input RF_IN- through capacitor C2, and NMOS transistor M7 and PMOS transistor M8 further amplify and mix the RF_IN- signal.

[0068] The gate of NMOS transistor M7 is connected to the local oscillator input signal LO_IN- to control its on and off states, and together with NMOS transistor M5, it completes the signal mixing. The drain of NMOS transistor M7 is connected to capacitor C2.

[0069] The gate of PMOS transistor M8 is connected to the local oscillator input signal LO_IN+, and the drain of PMOS transistor M8 is connected to capacitor C2 to form a current path.

[0070] NMOS transistor M7 and PMOS transistor M8 form a differential pair to amplify the input radio frequency signal and participate in the mixing process.

[0071] All of the above transistors adopt the minimum gate length design to reduce parasitic capacitance.

[0072] Based on the ideal embodiments of the present invention as inspiration, through the above description, relevant personnel can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and must be determined according to the scope of the claims.

Claims

1. A radio frequency mixer of complementary structure, comprising: Four NMOS transistors and four PMOS transistors, two resistors and two capacitors and a power supply voltage, characterized in that; The four NMOS transistors and the four PMOS transistors are configured in parallel in a complementary pair, and the sources of the NMOS transistors and the PMOS transistors are connected to a differential RF input signal; The resistor is used to provide a bias voltage for the transistor and is directly connected to the power supply voltage, and the capacitor is used for AC coupling and is grounded; The local oscillator input signal controls the gate conduction state of the NMOS transistor and the PMOS transistor, and converts the differential radio frequency input signal into a differential intermediate frequency output signal through mixing.

2. The complementary structure radio frequency mixer according to claim 1, characterized in that: The resistors include: a resistor R1 and a resistor R2, wherein the resistor R1 is connected to a differential radio frequency input signal RF_IN+, and the resistor R2 is connected to a differential radio frequency input signal RF_IN- and is directly connected to a power supply voltage.

3. The complementary structure radio frequency mixer according to claim 1, characterized in that: The capacitor includes: a capacitor C1 and a capacitor C2. The capacitor C1 is connected to a differential radio frequency input signal RF_IN+, and the capacitor C2 is connected to a differential radio frequency input signal RF_IN-, and a DC component is isolated by grounding.

4. The complementary structure radio frequency mixer according to claim 1, characterized in that: The drains of the NMOS transistor and the PMOS transistor form a current path through cross-connection, wherein the drain of the NMOS transistor is connected to another NMOS transistor, and the drain of the PMOS transistor is connected to another PMOS transistor.

5. The complementary structure radio frequency mixer according to claim 1, characterized in that: The local oscillator input signals LO_IN+ and LO_IN- respectively control the gates of the NMOS transistor and the PMOS transistor in the complementary pair, forming a switching operation with opposite phases.

6. The complementary structure radio frequency mixer according to claim 1, characterized in that: The differential intermediate frequency output signals IF_OUT+ and IF_OUT- are outputted from the drains of the PMOS transistor and the NMOS transistor respectively, and the signal consistency is enhanced through the common mode interference suppression structure.

7. The complementary structure radio frequency mixer according to claim 1, characterized in that: The NMOS transistor and the PMOS transistor in the complementary pair are connected through a shared source to form a differential amplifier structure.

8. The complementary structure radio frequency mixer according to claim 1, characterized in that: All transistors of the mixer are designed with a symmetrical layout.

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