Radio frequency low-noise amplifier with wave trapping function

Abstract

The invention discloses a radio frequency low-noise amplifier with a trap function. The radio frequency low-noise amplifier comprises a single-ended input matching circuit, a single-ended to differential circuit, a cascode differential amplification circuit, a biasing circuit and a trap circuit, the single-end input matching circuit is an input end of the low noise amplifier and provides a performance compromise scheme of gain matching and noise matching in a working frequency band, the single-end to differential circuit realizes conversion from a single end to a differential signal, and the cascode differential circuit realizes differential high-gain amplification. The bias circuit provides stable bias voltage for an MOS tube in the cascode circuit, and the stability of the bias voltage in the whole working temperature range is achieved through constant-temperature bias current provided by the band-gap reference circuit. According to the low-noise amplifier, the trap circuit is additionally arranged, so that the low-noise amplifier can realize an attenuation function at a strong interference signal frequency, the transmission of interference signals is inhibited, and nonlinear distortion of the amplifier circuit caused by the strong interference signals is effectively prevented.

Description

TECHNICAL FIELD

[0001] The application relates to the field of radio frequency integrated circuits, in particular to a radio frequency low noise amplifier with a trap function. BACKGROUND

[0002] The low noise amplifier is located at the front end of a radio frequency receiver, amplifies the weak signal received by an antenna, and the gain and noise performance thereof determines the sensitivity of the entire receiver, and is one of the key modules in the radio frequency receiver, especially a satellite positioning communication receiver with high sensitivity requirements.

[0003] For a Beidou satellite short message communication radio frequency transceiver chip, the receiving channel and the transmitting channel are integrated in the same chip, the transmitting power of the Beidou short message is usually greater than 3W or more, and the transmitting moment will cause very strong interference to the receiving channel, therefore, the low noise amplifier at the front end of the receiving channel needs to have strong anti-interference capability in addition to amplifying the extremely weak satellite signal below the noise floor. A cavity filter module is used in the S frequency point receiving channel of a Beidou short message transceiving radio frequency front end system disclosed in the Chinese utility model patent specification CN222423675U. A small-sized Beidou short message terminal radio frequency circuit is disclosed in a Chinese patent with the patent number CN1159873320A, and a three-stage high out-of-band suppression filter is used in the receiving antenna radio frequency circuit to improve the anti-interference capability. Such technologies are all solutions of using an off-chip filter to suppress strong interference, and are not suitable for chip integration. A radio frequency low noise amplifier is disclosed in a Chinese patent with the patent number CN118413198A, and a trap circuit is added at the input end of the LNA signal path, but the input matching is affected, and the matching circuit is complex. Therefore, a new low noise amplifier is urgently needed to solve the above technical problems. SUMMARY

[0004] The purpose of the application is to provide a radio frequency low noise amplifier with a trap function, which is used to improve the suppression capability of strong interference signals.

[0005] The radio frequency low noise amplifier with a trap function comprises a single-ended input matching circuit, a single-ended to differential circuit, a common source and common gate differential amplification circuit, a bias circuit and a trap circuit. The single-ended input matching circuit is the input end of the low noise amplifier, and provides a performance compromise scheme of gain matching and noise matching in the working frequency band. The single-ended to differential circuit realizes the conversion of single-ended signals to differential signals. The common source and common gate differential amplification circuit realizes differential high gain amplification. The bias circuit provides a stable bias voltage for the MOS tube in the common source and common gate circuit. The constant temperature biasing current provided by the band gap reference circuit realizes the stability of the bias voltage in the entire working temperature range.

[0006] Further, the single-ended input matching circuit comprises an inductor L1 and a capacitor C1, and RFIN is a radio frequency input signal of a low noise amplifier, connected with the inductor L1, and the other end of the inductor L1 is connected with the capacitor C1, and the other end of the capacitor C1 is connected with the gate of the MOS transistor M4.

[0007] Further, the single-ended to differential circuit is realized by taking the MOS transistor M4 as a first-stage amplifier, and the inductor L3 and the capacitor C2 are connected at both ends to form a load circuit, one end of which is connected with the power supply voltage VCC, and the other end is connected with the drain of the MOS transistor M4 and one end of the capacitor C3; the source of the MOS transistor M4 is connected with the inductor L2 and one end of the capacitor C4, and the other end of the inductor L2 is grounded, realizing source feedback; the capacitors C3 and C4 are connected with the differential amplifier circuit of the subsequent stage as blocking capacitors, thereby realizing the conversion from single-ended to differential.

[0008] Further, the common-source common-gate differential amplifier circuit comprises the capacitors C3 and C4 connected with the gates of the MOS transistors M5 and M6 respectively, the source of the MOS transistor M5 is connected with the source of the MOS transistor M6 and one end of the inductor L4, realizing a differential amplifier pair, and the other end of the inductor L4 is grounded. The drain of the MOS transistor M5 is connected with the source of the MOS transistor M7, and the drain of the MOS transistor M6 is connected with the source of the MOS transistor M8; the drain of the MOS transistor M7 is connected with one end of the inductor L5 and the capacitor C5, generating an output signal RFOUTp, and the drain of the MOS transistor M8 is connected with one end of the inductor L6 and the capacitor C6, generating an output signal RFOUTn, and the RFOUTp and the RFOUTn constitute a differential signal output; the other end of the inductor L5 and the capacitor C5 is connected with the power supply voltage VCC, and the other end of the inductor L6 and the capacitor C6 is connected with the power supply voltage VCC, forming a differential load circuit; the gates of the MOS transistors M7 and M8 are connected with the resistors R6 and R7 respectively, and a stable bias voltage is provided by a bias circuit, used for realizing the amplification of the differential common-source common-gate circuit.

[0009] Further, the trap circuit comprises a first-stage trap circuit and a second-stage trap circuit, and the two-stage trap circuit provides a high trap rejection ratio.

[0010] Further, the first-stage trap circuit comprises the capacitor C7 connected at one end with the drain of the MOS transistor M5 and the source of the MOS transistor M7, and at the other end with the inductor L7 and the capacitor C8, and the inductor L7 and the capacitor C8 form a parallel circuit, and the other end of the capacitor C8 is connected with one end of the capacitor C9, and the other end of the capacitor C9 is connected with the drain of the MOS transistor M6 and the source of the MOS transistor M8.

[0011] Further, the second-stage trap circuit comprises the capacitor C10 connected at one end with the RFOUTp, and at the other end with the inductor L8 and the capacitor C11, and the inductor L8 and the capacitor C11 form a parallel circuit, and the other end of the capacitor C11 is connected with one end of the capacitor C12, and the other end of the capacitor C12 is connected with the RFOUTn.

[0012] Furthermore, the bandgap reference circuit is used to generate a current bias signal for low temperature drift. It is connected to the gate and drain of M1 through resistor R1 to form a bias voltage, and connected to the gate of M4 through resistor R2 to provide a gate-source bias voltage for M4. It is connected to the gates of M5 and M6 through resistors R3 and R4 respectively to provide gate-source bias voltages for M5 and M6.

[0013] Furthermore, the bias circuit provides gate bias voltages to M7 and M8 respectively through resistors R6 and R7. The gate and drain of M1 are connected to the gate of M2, the drain of M2 is connected to the source of M3, and the gate and drain of M3 are interconnected and connected to the power supply voltage VCC through resistor R5 to form a bias voltage signal.

[0014] Furthermore, the power supply voltage VCC of the low-noise amplifier is 1.8V.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0016] (1) The present invention adopts a two-stage circuit structure with single-ended input and differential output, which simplifies the input matching circuit and suppresses common-mode interference signals. The differential output can be directly connected to the subsequent mixer. By adding a notch filter circuit, the low-noise amplifier can achieve attenuation at the frequency of strong interference signals, suppress the transmission of interference signals, effectively prevent the nonlinear distortion caused by strong interference signals to the amplifier circuit itself, and avoid the amplifier circuit from amplifying and entering the subsequent circuit, causing the subsequent circuit to fail.

[0017] (2) The circuit of the present invention is used in the Beidou satellite communication radio frequency chip. The circuit of the invention is located at the front end of the receiving channel of the Beidou radio frequency chip. The frequency range of the received signal is 2483.5MHz-2500MHz. The Beidou chip also integrates the L-band transmitting channel with a transmitting power of 10dBm. When the chip transmits the signal, it will generate strong interference signals to the receiving channel. Through the present invention, the on-chip receiving channel can achieve a suppression effect of nearly 70dB against the strong interference signal of the L-band, which greatly improves the anti-interference capability of the Beidou communication radio frequency chip. Attached Figure Description

[0018] Figure 1 This is a circuit diagram of the low-noise amplifier with notch filtering function of the present invention;

[0019] Figure 2 This is a simulation diagram of the gain and notch filtering effect of the low-noise amplifier with notch filtering function of the present invention. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0021] like Figure 1As shown, the present invention includes a single-ended input matching circuit, a single-ended to differential circuit, a common-source cascode differential amplifier circuit, a bias circuit, and a notch filter circuit.

[0022] The single-ended input matching circuit serves as the input of the low-noise amplifier, providing a performance trade-off between gain matching and noise matching within the operating frequency band, achieving optimal single-ended 50-ohm matching.

[0023] The single-ended to differential circuit realizes the conversion from single-ended to differential signal. The differential signal has a good suppression effect on common-mode noise, which can reduce the noise figure of the amplifier and thus improve the overall noise figure of the RF receiver.

[0024] The cascode differential circuit achieves differential high-gain amplification, which is used to improve the overall circuit gain. At the same time, it can effectively suppress common-mode interference signals and can be directly connected to the subsequent differential mixer.

[0025] The bias circuit is used to provide a stable bias voltage to the MOSFET in the common source cascode circuit. The constant temperature bias current provided by the bandgap reference circuit ensures that the bias voltage is stable throughout the entire operating temperature range.

[0026] The notch filter circuit uses a two-stage LC notch filter to suppress strong interference signals. At the frequency of the interference signal, the amplifier provides attenuation.

[0027] RFIN is the radio frequency input signal of the low-noise amplifier, which is connected to inductor L1. The other end of inductor L1 is connected to capacitor C1, and the other end of C1 is connected to the gate of MOSFET M4. Inductor L1 and capacitor C1 form a single-ended input matching circuit to obtain the best gain and noise matching of single-ended 50 ohms.

[0028] M4 serves as the first-stage amplifier transistor, achieving single-ended to differential conversion. Inductor L3 and capacitor C2 are connected at both ends to form a load circuit; one end of L3 is connected to the power supply voltage VCC, and the other end is connected to the drain of M4 and also to one end of capacitor C3. The source of M4 is connected to inductor L2 and one end of capacitor C4, while the other end of inductor L2 is grounded, achieving source-level feedback. C3 and C4 act as DC blocking capacitors connected to the subsequent differential amplifier circuit, thus achieving single-ended to differential conversion and providing a certain gain.

[0029] Capacitors C3 and C4 are connected to the gates of MOSFETs M5 and M6, respectively. The source of M5 is connected to the source of M6, and also to one end of inductor L4, forming a differential amplifier pair. The other end of inductor L4 is grounded. The drain of M5 is connected to the source of M7, and the drain of M6 is connected to the source of M8. The drain of M7 is connected to one end of L5 and C5, generating the output signal RFOUTp. The drain of M8 is connected to one end of L6 and C6, generating the output signal RFOUTn. RFOUTp and RFOUTn constitute the differential signal output. The other ends of L5 and C5, and the other ends of L6 and C6 are connected to the power supply voltage VCC, forming a differential load circuit. The gates of M7 and M8 are connected to resistors R6 and R7, respectively, with a stable bias voltage provided by the bias circuit for differential cascode amplification.

[0030] One end of capacitor C7 is connected to the drain of M5 and the source of M7, and the other end is connected to inductor L7 and capacitor C8. L7 and C8 form a parallel circuit. The other end of capacitor C7 is connected to one end of capacitor C9. The other end of capacitor C9 is connected to the drain of M6 and the source of M8. This is used to form a first-stage notch circuit at the source-drain connection of the differential cascode circuit. One end of capacitor C10 is connected to RFOUTp, and the other end is connected to inductor L8 and capacitor C11. L8 and C11 form a parallel circuit. The other end of capacitor C10 is connected to one end of capacitor C12. The other end of capacitor C12 is connected to RFOUTn. This is used to form a second-stage notch circuit at the load of the differential cascode circuit. The two-stage notch circuit provides a high notch rejection ratio.

[0031] The bandgap reference circuit is used to generate a current bias signal for low temperature drift. It is connected to the gate and drain of M1 through resistor R1 to form a bias voltage. It is connected to the gate of M4 through resistor R2 to provide a gate-source bias voltage for M4. It is connected to the gates of M5 and M6 through resistors R3 and R4 respectively to provide gate-source bias voltages for M5 and M6.

[0032] The gate and drain of MI are connected to the gate of M2, the drain of M2 is connected to the source of M3, the gate and drain of M3 are interconnected and connected to the power supply voltage VCC through resistor R5 to form a bias voltage signal, and the gate bias voltage is provided to M7 and M8 through resistors R6 and R7 respectively.

[0033] In this embodiment of the invention, the RF low-noise amplifier uses a 1.8V power supply (VCC). Simulation tests have shown that... Figure 2 As shown, the S21 gain curve of the amplifier is displayed. M1 marks the notch rejection effect of the amplifier at 1.6 GHz, and M2 marks the gain effect of the amplifier at 2.5 GHz. The rejection effect at 1.6 GHz can reach 68.98 dB.

Claims

1. A radio frequency low-noise amplifier with notch filtering function, characterized in that, It includes a single-ended input matching circuit, a single-ended to differential circuit, a common-source cascode differential amplifier circuit, a bias circuit, and a notch filter circuit. The single-ended input matching circuit is the input terminal of the low-noise amplifier, providing a performance trade-off between gain matching and noise matching within the operating frequency band. The single-ended to differential circuit realizes the conversion from single-ended to differential signals. The common-source cascode differential circuit realizes differential high-gain amplification. The bias circuit provides a stable bias voltage to the MOSFET in the common-source cascode circuit. Through the constant-temperature bias current provided by the bandgap reference circuit, the bias voltage is stabilized throughout the entire operating temperature range.

2. The RF low-noise amplifier with notch filtering function according to claim 1, characterized in that, The single-ended input matching circuit includes an inductor L1 and a capacitor C1. RFIN is the radio frequency input signal of the low-noise amplifier and is connected to the inductor L1. The other end of the inductor L1 is connected to the capacitor C1, and the other end of C1 is connected to the gate of the MOSFET M4.

3. The RF low-noise amplifier with notch filtering function according to claim 1, characterized in that, The single-ended to differential circuit is implemented using M4 as the first-stage amplifier transistor. The two ends of inductor L3 and capacitor C2 are connected to form a load circuit, with one end connected to the power supply voltage VCC and the other end connected to the drain of M4 and one end of capacitor C3. The source of M4 is connected to inductor L2 and one end of capacitor C4, while the other end of inductor L2 is grounded to achieve source feedback. C3 and C4 are connected as DC blocking capacitors to the subsequent differential amplifier circuit, thereby realizing the single-ended to differential conversion.

4. The RF low-noise amplifier with notch filtering function according to claim 1, characterized in that, The common-source cascode differential amplifier circuit includes capacitors C3 and C4 connected to the gates of MOSFETs M5 and M6, respectively. The source of M5 is connected to the source of M6 and also to one end of inductor L4, forming a differential amplifier pair. The other end of inductor L4 is grounded. The drain of M5 is connected to the source of M7, and the drain of M6 is connected to the source of M8. The drain of M7 is connected to one end of L5 and C5, generating the output signal RFOUTp. The drain of M8 is connected to one end of L6 and C6, generating the output signal RFOUTn. RFOUTp and RFOUTn constitute the differential signal output. The other ends of L5 and C5 are connected to the power supply voltage VCC, and the other ends of L6 and C6 are connected to the power supply voltage VCC, forming a differential load circuit. The gates of M7 and M8 are connected to resistors R6 and R7, respectively, and a stable bias voltage is provided by a bias circuit to realize the differential common-source cascode circuit amplification.

5. The RF low-noise amplifier with notch filtering function according to claim 1, characterized in that, The notch circuit includes a first-stage notch circuit and a second-stage notch circuit, and the two-stage notch circuit provides a high notch rejection ratio.

6. The RF low-noise amplifier with notch filtering function according to claim 5, characterized in that, The first-stage notch filter circuit includes a capacitor C7, one end of which is connected to the drain of M5 and the source of M7, and the other end of which is connected to the inductor L7 and the capacitor C8, with L7 and C8 forming a parallel circuit. The other end of the capacitor C7 is connected to one end of the capacitor C9, and the other end of the capacitor C9 is connected to the drain of M6 and the source of M8.

7. The RF low-noise amplifier with notch filtering function according to claim 5, characterized in that, The second-stage notch filter circuit includes a capacitor C10, one end of which is connected to RFOUTp, and the other end of which is connected to an inductor L8 and a capacitor C11, forming a parallel circuit. The other end of the capacitor C10 is connected to one end of a capacitor C12, and the other end of the capacitor C12 is connected to RFOUTn.

8. The RF low-noise amplifier with notch filtering function according to claim 1, characterized in that, The bandgap reference circuit is used to generate a current bias signal for low temperature drift. It is connected to the gate and drain of M1 through resistor R1 to form a bias voltage. It is connected to the gate of M4 through resistor R2 to provide a gate-source bias voltage for M4. It is connected to the gates of M5 and M6 through resistors R3 and R4 respectively to provide gate-source bias voltages for M5 and M6.

9. The RF low-noise amplifier with notch filtering function according to claim 1, characterized in that, The bias circuit provides gate bias voltages to M7 and M8 through resistors R6 and R7 respectively. The gate and drain of M1 are connected to the gate of M2, the drain of M2 is connected to the source of M3, and the gate and drain of M3 are interconnected and connected to the power supply voltage VCC through resistor R5 to form a bias voltage signal.

10. The RF low-noise amplifier with notch filtering function according to claim 1, characterized in that, The low-noise amplifier is powered by a 1.8V supply voltage (VCC).

Images