CN107231130B

CN107231130B - Up-converter based on transconductance tube local oscillator switch fusion structure

Info

Publication number: CN107231130B
Application number: CN201710372268.1A
Authority: CN
Inventors: 陈超; 吴建辉; 李红
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2017-05-24
Filing date: 2017-05-24
Publication date: 2020-06-30
Anticipated expiration: 2037-05-24
Also published as: CN107231130A

Abstract

The invention discloses an up-converter based on a transconductance tube and local oscillator switch fusion structure, wherein a local oscillator switch is fused with a transconductance tube, and the local oscillator switch tube generates intermediate-frequency current and performs periodic switching on the intermediate-frequency current; the radio frequency local oscillation signal acts on the local oscillation transistor in a capacitive coupling mode, and the intermediate frequency signal provides bias voltage for the local oscillation transistor through an operational amplifier negative feedback loop; the bias voltage is connected with the grid through a resistor, so that the isolation of the local oscillation signal and the intermediate frequency signal is realized; the circuit realizes input voltage and current conversion in a mode of bridging resistors at two ends of the differential pair, thereby ensuring higher linearity. The invention reduces the number of stacked transistors of the traditional mixing circuit from three to two, thereby obviously easing the voltage margin; the actual grid voltage of the local oscillation switch tube is the sum of the output voltage of the error amplifier and the oscillation amplitude of the local oscillation signal, so that the source voltage of the local oscillation switch tube can be further increased, the output impedance of the tail current source is improved, and higher voltage oscillation amplitude can be accommodated.

Description

Up-converter based on transconductance tube local oscillator switch fusion structure

Technical Field

The invention relates to an up-converter, in particular to an up-converter based on a transconductance tube local oscillator switch fusion structure.

Background

The up-converter is a core module in the rf transmission link, which is responsible for moving the analog baseband signal to the carrier frequency, and usually has a high linearity to prevent the output spectrum from spreading. The traditional up-conversion structure generally uses OTA and feedback to realize high-linearity voltage-current conversion, directly transmits input voltage to two ends of a resistor to be converted into linear current, and then carries out frequency domain conversion on the current through a local oscillator switch stage. The traditional structure is respectively stacked with a current source, a transconductance stage, a local oscillator switch stage and a load stage from top to bottom. Under near-threshold voltage conditions, the output voltage of the OTA must not be lower than the sum of the two overdrive voltages, the threshold voltage, and the input signal swing. Considering that there is still some voltage drop between the output voltage and the power supply voltage of the OTA, it is difficult to obtain a voltage margin for proper operation with this structure. If the tail current source is biased in the linear region and the signal swing is reduced to maintain circuit function, the conversion gain and linearity will suffer from severe degradation.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problems, the invention provides an up-converter based on a transconductance tube local oscillator switch fusion structure, which can work under a power supply voltage below 0.6V and keep higher conversion gain and linearity.

The technical scheme is as follows: in order to realize the purpose of the invention, the technical scheme adopted by the invention is as follows: an up-converter based on a transconductance tube local oscillator switch fusion structure comprises a local oscillator switch and a transconductance tube, wherein the local oscillator switch is in RC coupling and generates intermediate-frequency current and carries out periodic switching on the intermediate-frequency current; the local oscillation signal acts on the transistor in a capacitive coupling mode, and the intermediate frequency signal provides bias voltage for the transistor through an operational amplifier negative feedback loop; the bias voltage is connected with the grid electrode of the transistor through a resistor, so that the isolation of the local oscillation signal and the intermediate frequency signal is realized; the circuit realizes input voltage-current conversion by connecting a resistor across the differential pair.

An up-converter based on a local oscillator switch fusion structure of a transconductance tube comprises a first N-type metal oxide transistor, a second N-type metal oxide transistor, a third N-type metal oxide transistor, a fourth N-type metal oxide transistor, a fifth N-type metal oxide transistor, a sixth N-type metal oxide transistor, a first error amplifier, a second error amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, a first inductor and a second inductor.

The source electrode of the first N-type metal oxide transistor is grounded, the grid electrode of the first N-type metal oxide transistor is connected with a first bias voltage, and the drain electrode of the first N-type metal oxide transistor is connected with the negative input end of the first error amplifier; the positive input end of the first error amplifier is connected with the anode of an input intermediate frequency signal, and the output end of the first error amplifier is connected with the cathode of the second resistor; the positive electrode of the second resistor is connected with the grid electrode of the third N-type metal oxide transistor, the source electrode of the third N-type metal oxide transistor is connected with the drain electrode of the first N-type metal oxide transistor, and the drain electrode of the third N-type metal oxide transistor is connected with the output positive electrode of the mixer; the positive end of the second capacitor is connected with the negative electrode of the local oscillation signal, and the negative end of the second capacitor is connected with the grid electrode of the third N-type metal oxide transistor; the source electrode of the fourth N-type metal oxide transistor is connected with the drain electrode of the first N-type metal oxide transistor, the drain electrode of the fourth N-type metal oxide transistor is connected with the output cathode of the up-converter, the grid electrode of the fourth N-type metal oxide transistor is connected with the anode of the third resistor, and the cathode of the third resistor is connected with the output end of the first error amplifier; the anode of the third capacitor is connected with the anode of the local oscillator signal, and the cathode of the third capacitor is connected with the grid electrode of the fourth N-type metal oxide transistor; the source electrode of the second N-type metal oxide transistor is grounded, the grid electrode of the second N-type metal oxide transistor is connected with a first bias voltage, the drain electrode of the second N-type metal oxide transistor is connected with the anode of the first resistor, and the cathode of the first resistor is connected with the drain electrode of the first N-type metal oxide transistor; the anode of the first capacitor is connected with the drain electrode of the first N-type metal oxide transistor, and the cathode of the first capacitor is connected with the drain electrode of the second N-type metal oxide transistor; the negative input end of the second error amplifier is connected with the drain electrode of the second N-type metal oxide transistor, and the positive input end of the second error amplifier is connected with the negative electrode of the input intermediate frequency signal; the output end of the second error amplifier is connected with the cathode of a fifth resistor, and the anode of the fifth resistor is connected with the grid electrode of a sixth N-type metal oxide transistor; the source electrode of the sixth N-type metal oxide transistor is connected with the drain electrode of the second N-type metal oxide transistor, and the drain electrode of the sixth N-type metal oxide transistor is connected with the output cathode of the up-converter; the anode of the fifth capacitor is connected with the cathode of the local oscillator signal, and the cathode of the fifth capacitor is connected with the grid electrode of the sixth N-type metal oxide transistor; the source electrode of the fifth N-type metal oxide transistor is connected with the drain electrode of the second N-type metal oxide transistor, the drain electrode of the fifth N-type metal oxide transistor is connected with the output anode of the up-converter, the grid electrode of the fifth N-type metal oxide transistor is connected with the cathode of the fourth resistor, and the anode of the fourth resistor is connected with the output end of the second error amplifier; the anode of the fourth capacitor is connected with the anode of the local oscillator signal, and the cathode of the fourth capacitor is connected with the grid electrode of the fifth N-type metal oxide transistor; the positive pole of the first inductor is connected with the output positive pole of the up-converter, and the negative pole of the first inductor is connected with the power supply; the positive electrode of the sixth capacitor is connected with the output positive electrode of the up-converter, and the negative electrode of the sixth capacitor is connected with the power supply; the positive pole of the second inductor is connected with the output negative pole of the up-converter, and the negative pole of the second inductor is connected with the power supply; the positive pole of the seventh capacitor is connected with the output negative pole of the up-converter, and the negative pole of the seventh capacitor is connected with the power supply.

Has the advantages that: compared with the prior art, the invention has the following effects: (1) the fusion idea of the transconductance tube/the local oscillator switch is provided, and the problem that the traditional linear transconductance up-converter cannot work under the condition of low voltage is solved; (2) the actual grid voltage of the local oscillation switch tube is the sum of the output voltage of the error amplifier and the oscillation amplitude of the local oscillation signal, so that even if the output voltage of the error amplifier is limited by the power supply voltage, the source voltage of the local oscillation switch tube can still be raised to about half of the power supply voltage, thereby improving the output impedance of the tail current source and accommodating higher input voltage oscillation amplitude.

Drawings

Fig. 1 is a circuit diagram of an up-converter based on a transconductance tube local oscillator switch fusion structure according to the present invention;

fig. 2 is a time domain waveform diagram of the input signal, the voltage across the transconductance resistor, and the local oscillator transistor gate voltage according to the present invention.

Detailed Description

The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.

As shown in fig. 1, the upconverter based on the transconductance tube and local oscillator switch fusion structure according to the present invention fuses the local oscillator switch function and the transconductance tube, where the local oscillator switch is in an RC coupling mode, a radio frequency local oscillator signal is coupled to a local oscillator tube gate through a capacitor, and an error amplifier dynamically adjusts a bias voltage of the local oscillator tube through a coupling resistor, so as to ensure that an intermediate frequency voltage at two ends of the resistor is consistent with an input signal, so that a current flowing through the local oscillator switch is proportional to the input voltage. Because the frequency difference between the intermediate frequency signal and the local oscillation signal is very large, the leakage signal from the local oscillation signal to the output end of the OTA can be effectively removed by the filter capacitors at the two ends of the resistor; and the coupling resistor with higher resistance value is isolated between the OTA output voltage and the local oscillation signal, so that the interference between the signals is avoided.

As shown in fig. 1, an up-converter based on a cross-conduit local oscillator switch fusion structure can operate at a low voltage, and includes: a first N-type metal oxide transistor (hereinafter referred to as NMOS transistor) N1, a second NMOS transistor N2, a third NMOS transistor N3, a fourth NMOS transistor N4, a fifth NMOS transistor N5, a sixth NMOS transistor N6, a first error amplifier a1, a second error amplifier a2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, a first inductor L1, and a second inductor L2.

The source of the first NMOS transistor N1 is grounded, the gate of N1 is connected with a first bias voltage, and the drain of N1 is connected with the negative input end of the first error amplifier A1; the positive input end of the first error amplifier A1 is connected with the positive electrode of the input intermediate frequency signal, and the output end of A1 is connected with the negative electrode of the second resistor R2; the anode of the second resistor R2 is connected with the grid of the third NMOS tube N3, the source of N3 is connected with the drain of N1, and the drain of N3 is connected with the output anode of the mixer; the positive end of the second capacitor C2 is connected with the negative pole of the local oscillation signal, and the negative end of the second capacitor C2 is connected with the grid of the N3; the source electrode of the fourth NMOS tube N4 is connected with the drain electrode of the N1, the drain electrode of the N4 is connected with the negative electrode of the output of the up-converter, the grid electrode of the N4 is connected with the positive electrode of the third resistor R3, and the negative electrode of the R3 is connected with the output end of the A1; the anode of the third capacitor C3 is connected with the anode of the local oscillation signal, and the cathode of the third capacitor C3 is connected with the grid of the N4; the source electrode of the second NMOS tube N2 is grounded, the grid electrode of N2 is connected with a first bias voltage, the drain electrode of N2 is connected with the anode of a first resistor R1, and the cathode of R1 is connected with the drain electrode of N1; the anode of the first capacitor C1 is connected with the drain of the N1, and the cathode of the first capacitor C1 is connected with the drain of the N2; the negative input end of the second error amplifier A2 is connected with the drain electrode of the N2, and the positive input end of A2 is connected with the negative electrode of the input intermediate frequency signal; the output end of A2 is connected with the cathode of a fifth resistor R5, and the anode of R5 is connected with the gate of a sixth NMOS transistor N6; the source electrode of the sixth NMOS tube N6 is connected with the drain electrode of the N2, and the drain electrode of the N6 is connected with the output cathode of the up-converter; the positive electrode of the fifth capacitor C5 is connected with the negative electrode of the local oscillation signal, and the negative electrode of the C5 is connected with the grid electrode of the N6; the source electrode of a fifth NMOS tube N5 is connected with the drain electrode of N2, the drain electrode of N5 is connected with the output anode of the up-converter, the grid electrode of N5 is connected with the cathode of a fourth resistor R4, and the anode of the fourth resistor R4 is connected with the output end of A2; the positive electrode of the fourth capacitor C4 is connected with the positive electrode of the local oscillation signal, and the negative electrode of the C4 is connected with the grid electrode of the N5; the positive pole of the first inductor L1 is connected with the output positive pole of the up-converter, and the negative pole of the L1 is connected with the power supply; the positive electrode of the sixth capacitor C6 is connected with the output positive electrode of the up-converter, and the negative electrode of the C6 is connected with the power supply; the positive pole of the second inductor L2 is connected with the output negative pole of the up-converter, and the negative pole of the L2 is connected with the power supply; the positive electrode of the seventh capacitor C7 is connected with the negative electrode of the output of the up-converter, and the negative electrode of the C7 is connected with the power supply.

The invention endows the local oscillator switch tube with double functions of intermediate frequency transconductance and the local oscillator switch, on one hand, the voltage margin is directly improved by reducing the number of stacked transistors; on the other hand, because the actual grid voltage of the local oscillation switch tube is the sum of the output voltage of the OTA and the oscillation amplitude of the local oscillation signal, the source voltage of the local oscillation switch tube can be further increased, thereby improving the output impedance of the tail current source and accommodating higher voltage oscillation amplitude, and ensuring the linearity and conversion gain.

Fig. 2 shows time domain waveforms of an input signal, voltages at two ends of a transconductance resistor, and a gate voltage of a local oscillator tube of the transconductor tube local oscillator switch fusion structure upconverter according to the present invention. It can be seen that under the action of the negative feedback loop, the voltage at the two ends of the resistor always changes along with the input voltage, so that the linear relation between the intermediate frequency current entering the local oscillation switch and the input voltage is ensured. The local oscillation signal directly acts on a grid electrode of the local oscillation switch tube through a capacitor, the envelope of the local oscillation signal is controlled by the output voltage of the error amplifier, and the shape of the envelope is basically consistent with that of the input signal; the peak value of the grid voltage can exceed the power supply voltage of 0.6V, the output voltage of the error amplifier does not exceed 0.5V, the drain voltage of the tail current tube is always above 0.25V, and the sufficient voltage margin of each configuration in the circuit can be ensured.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. The utility model provides an up converter based on transconductance tube local oscillator switch fuses structure which characterized in that: the system comprises a local oscillator switch and a cross-over pipe, wherein the local oscillator switch is in RC coupling and generates intermediate-frequency current and periodically switches the intermediate-frequency current; the local oscillation signal acts on the transistor in a capacitive coupling mode, and the intermediate frequency signal provides bias voltage for the transistor through an operational amplifier negative feedback loop; the bias voltage is connected with the grid electrode of the transistor through a resistor, so that the isolation of the local oscillation signal and the intermediate frequency signal is realized; the circuit realizes input voltage-current conversion in a mode of bridging resistors at two ends of a differential pair;

the up-converter comprises a first N-type metal oxide transistor (N1), a second N-type metal oxide transistor (N2), a third N-type metal oxide transistor (N3), a fourth N-type metal oxide transistor (N4), a fifth N-type metal oxide transistor (N5), a sixth N-type metal oxide transistor (N6), a first error amplifier (A1), a second error amplifier (A2), a first resistor (R1), a second resistor (R2), a third resistor (R3), a fourth resistor (R4), a fifth resistor (R5), a first capacitor (C1), a second capacitor (C2), a third capacitor (C3), a fourth capacitor (C4), a fifth capacitor (C5), a sixth capacitor (C6), a seventh capacitor (C7), a first inductor (L1) and a second inductor (L2);

wherein the source of the first NMOS transistor (N1) is grounded, the gate of the first NMOS transistor (N1) is connected to a first bias voltage, and the drain of the first NMOS transistor (N1) is connected to the negative input terminal of the first error amplifier (A1); the positive input end of the first error amplifier (A1) is connected with the positive electrode of the input intermediate frequency signal, and the output end of the first error amplifier (A1) is connected with the negative electrode of the second resistor (R2); the anode of the second resistor (R2) is connected with the grid of the third N-type metal oxide transistor (N3), the source of the third N-type metal oxide transistor (N3) is connected with the drain of the first N-type metal oxide transistor (N1), and the drain of the third N-type metal oxide transistor (N3) is connected with the output anode of the mixer; the positive end of the second capacitor (C2) is connected with the negative pole of the local oscillator signal, and the negative end of the second capacitor (C2) is connected with the grid of the third N-type metal oxide transistor (N3); the source electrode of the fourth N-type metal oxide transistor (N4) is connected with the drain electrode of the first N-type metal oxide transistor (N1), the drain electrode of the fourth N-type metal oxide transistor (N4) is connected with the negative electrode of the output of the up-converter, the grid electrode of the fourth N-type metal oxide transistor (N4) is connected with the positive electrode of the third resistor (R3), and the negative electrode of the third resistor (R3) is connected with the output end of the first error amplifier (A1); the anode of the third capacitor (C3) is connected with the anode of the local oscillator signal, and the cathode of the third capacitor (C3) is connected with the grid of the fourth N-type metal oxide transistor (N4); the source electrode of the second N-type metal oxide transistor (N2) is grounded, the grid electrode of the second N-type metal oxide transistor (N2) is connected with a first bias voltage, the drain electrode of the second N-type metal oxide transistor (N2) is connected with the positive electrode of the first resistor (R1), and the negative electrode of the first resistor (R1) is connected with the drain electrode of the first N-type metal oxide transistor (N1); the anode of the first capacitor (C1) is connected with the drain of the first N-type metal oxide transistor (N1), and the cathode of the first capacitor (C1) is connected with the drain of the second N-type metal oxide transistor (N2); the negative input end of the second error amplifier (A2) is connected with the drain electrode of the second N-type metal oxide transistor (N2), and the positive input end of the second error amplifier (A2) is connected with the negative electrode of the input intermediate frequency signal; the output end of the second error amplifier (A2) is connected with the cathode of a fifth resistor (R5), and the anode of the fifth resistor (R5) is connected with the grid electrode of a sixth N-type metal oxide transistor (N6); the source electrode of the sixth N-type metal oxide transistor (N6) is connected with the drain electrode of the second N-type metal oxide transistor (N2), and the drain electrode of the sixth N-type metal oxide transistor (N6) is connected with the output negative electrode of the up-converter; the positive electrode of the fifth capacitor (C5) is connected with the negative electrode of the local oscillator signal, and the negative electrode of the fifth capacitor (C5) is connected with the grid electrode of the sixth N-type metal oxide transistor (N6); the source electrode of the fifth N-type metal oxide transistor (N5) is connected with the drain electrode of the second N-type metal oxide transistor (N2), the drain electrode of the fifth N-type metal oxide transistor (N5) is connected with the output anode of the up-converter, the grid electrode of the fifth N-type metal oxide transistor (N5) is connected with the cathode of the fourth resistor (R4), and the anode of the fourth resistor (R4) is connected with the output end of the second error amplifier (A2); the positive electrode of the fourth capacitor (C4) is connected with the positive electrode of the local oscillator signal, and the negative electrode of the fourth capacitor (C4) is connected with the grid electrode of the fifth N-type metal oxide transistor (N5); the positive pole of the first inductor (L1) is connected with the output positive pole of the up-converter, and the negative pole of the first inductor (L1) is connected with the power supply; the positive electrode of the sixth capacitor (C6) is connected with the output positive electrode of the up-converter, and the negative electrode of the sixth capacitor (C6) is connected with the power supply; the positive pole of the second inductor (L2) is connected with the output negative pole of the up-converter, and the negative pole of the second inductor (L2) is connected with the power supply; the positive electrode of the seventh capacitor (C7) is connected with the output negative electrode of the up-converter, and the negative electrode of the seventh capacitor (C7) is connected with the power supply.