Broadband resistance feedback gain variable low-noise amplifier

Abstract

The invention provides a broadband resistance feedback gain variable low-noise amplifier. The broadband resistance feedback gain variable low-noise amplifier is provided with an input matching unit, an amplifying unit, a feedback unit, a load unit and a gain switching unit. A radio frequency input single-end signal is connected with the input matching unit, the output of the input matching unit is connected with the amplification unit, the amplification unit is connected to the input of the feedback unit, the feedback unit is connected to the input of the input matching unit, the amplification unit is simultaneously connected to the output load unit, and the output load unit outputs a radio frequency double-end radio frequency signal. The gain switching unit is connected to the feedback unit and the load unit. According to the broadband resistance feedback low-noise amplifier, the transistor M4 and the resistor M4 are added on the basis of a traditional gain switching scheme, the value of a feedback resistor is reduced while the impedance of a load end is reduced, the broadband characteristic of S11 is maintained while the gain is reduced, and the broadband resistance feedback low-noise amplifier with the switchable gain is achieved.

Description

Technical Field

[0001] The invention belongs to the field of radio frequency integrated circuits, and in particular relates to a broadband resistor feedback gain variable low noise amplifier. Background Art

[0002] In communication systems, it is often necessary to use a circuit called a low-noise amplifier as the first stage of the receiving link to preliminarily amplify the signal of a certain frequency band, while ensuring sufficient gain and introducing low noise. At present, there are many communication standards and a wide range of operating frequency bands, and broadband low-noise amplifiers have gradually become a design hotspot. Among them, the resistive feedback common-source amplifier has a simple structure and can provide excellent noise performance while achieving broadband characteristics. It is often used to design broadband low-noise amplifiers. In addition, in order to cope with input signals of different powers at the input end of the receiver, it is often necessary to design the low-noise amplifier into different gain levels, and the design of the resistive feedback common-source amplifier gain switching scheme has become a major difficulty.

[0003] like Figure 1 The figure shows a resistor feedback common source low noise amplifier using a traditional gain switching scheme. A resistor R3 is connected in parallel to the load end of the resistor feedback common source low noise amplifier, and the on and off of the transistor M3 is controlled by the control signal V1, thereby controlling the gain of the amplifier. This scheme can indeed reduce the gain of the low noise amplifier, but in the resistor feedback common source low noise amplifier, the feedback resistor R1 connects the load network and the input end, and the change in the load network impedance will directly change the performance of the input matching, resulting in the input matching being unable to maintain broadband characteristics. Figure 2 The following are the S-parameter simulation results of the high-gain and low-gain common-source feedback low-noise amplifier using this solution. In high-gain mode, the low-noise amplifier maintains a gain of about 15dB within 2.5-6GHz, and S11 is less than -10dB. In low-gain mode, although the gain of this solution drops to 8dB and maintains broadband characteristics within 2.5-6GHz, S11 deteriorates to -5.6dB within 2.5-6GHz, and the portion less than -10dB is only 4.4-6GHz, which greatly reduces the input matching bandwidth. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the traditional resistor feedback common source low noise amplifier gain switching scheme and provide a gain switching scheme to reduce the gain of the resistor feedback common source low noise amplifier while maintaining the broadband characteristics of input matching.

[0005] The technical solution adopted by the present invention is as follows: a broadband resistance feedback gain variable low noise amplifier, characterized in that: an input matching unit, an amplifying unit, a feedback unit, a load unit and a gain switching unit are provided. The RF input single-ended signal is connected to the input matching unit, the output of the input matching unit is connected to the amplifying unit, the amplifying unit is connected to the input of the feedback unit, the feedback unit is connected to the input of the input matching unit, the amplifying unit is simultaneously connected to the output load unit, the output load unit outputs a RF double-ended RF signal, and the gain switching unit is connected to the feedback unit and the load unit.

[0006] The input matching unit includes an inductor L1 and an inductor L2, one end of the inductor L1 is respectively connected to the RF input signal and one end of C1 in the feedback unit, the other end of the inductor L1 is connected to the gate of the transistor M1 in the amplification unit, one end of the inductor L2 is connected to the source of the transistor M1 in the amplification unit, and the other end of the inductor L2 is grounded;

[0007] The amplification unit includes a transistor M1 and a transistor M2, the gate of the transistor M1 is connected to the other end of the inductor L1 in the input matching unit and the bias voltage VG, the source of the transistor M1 is connected to one end of the inductor L2 in the input matching unit, the drain of the transistor M1 is connected to the source of the transistor M2, the gate of the transistor M2 is connected to the power supply, and the drain of the transistor M2 is respectively connected to one end of R1 in the feedback unit, one end of the capacitor C2 in the load unit, and one end of the inductor L3 in the transformer T1 in the load unit;

[0008] The feedback unit includes a resistor R1 and a capacitor C1, one end of the resistor R1 is respectively connected to the drain of the transistor M2 in the amplification unit, one end of C2 in the load unit and one end of the first inductor L3 in the transformer T1 in the load unit, the other end of the resistor R1 is connected to one end of the capacitor C1, and the other end of the capacitor C1 is connected to one end of the inductor L1 in the input matching unit;

[0009] The load unit includes capacitors C2 and C3, a resistor R2, and a transformer T1. The transformer T1 includes inductors L3 and L4. One end of the capacitor C2 is respectively connected to the drain of the transistor M2 in the amplification unit, one end of R1 in the feedback unit, and one end of the inductor L3. The other end of the capacitor C2 is connected to a power supply. One end of the inductor L3 is respectively connected to the drain of the transistor M2 in the amplification unit, one end of R1 in the feedback unit, and one end of the capacitor C2. The other end of the inductor L3 is connected to a power supply. One end of the inductor L4 is respectively connected to one end of the capacitor C3 and the resistor R2. The other end of the inductor L4 is respectively connected to the other end of the capacitor C3 and the resistor R2. Both ends of the inductor L4, the capacitor C3, and the resistor R2 are connected to both ends of the RF output signal.

[0010] The gain switching unit includes transistors M3, M4, resistors R3 and R4. The source of transistor M3 is connected to the power supply.

[0011] ———The gate of transistor M3 is connected to the control signal V1, the drain of transistor M3 is connected to one end of resistor R3, the other end of resistor R3 is connected to the drain of transistor M2 in the amplifying unit, the drain of transistor M4 is connected to the drain of transistor M2 in the amplifying unit, the gate of transistor M4 is connected to the control signal V1, the source of transistor M4 is connected to one end of resistor R4, and the other end of resistor R4 is connected to one end of capacitor C1 in the feedback unit.

[0012] Advantages and significant effects of the present invention:

[0013] The broadband resistor feedback variable gain low noise amplifier proposed by the present invention adds a transistor M4 and a resistor M4 to the traditional gain switching scheme, reduces the value of the feedback resistor while reducing the load end impedance, maintains the broadband characteristics of S11 while reducing the gain, and realizes a broadband resistor feedback low noise amplifier with switchable gain. The present invention switches the feedback coefficient of the feedback unit and the impedance of the load unit through the gain switching unit, and can simultaneously realize the broadband characteristics of gain and input matching when the gain is switched. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a resistor feedback common source low noise amplifier using a traditional gain switching scheme;

[0015] Figure 2 It is the S-parameter simulation result of the resistor feedback common-source low noise amplifier using the traditional gain switching scheme;

[0016] Figure 3 is a circuit block diagram of a low noise amplifier of the present invention;

[0017] Figure 4 It is a circuit schematic diagram of the low noise amplifier of the present invention;

[0018] Figure 5 are the S parameter simulation results of different gain levels of the low noise amplifier of the present invention;

[0019] Figure 6 It is the noise coefficient simulation result of different gain levels of the low noise amplifier of the present invention. DETAILED DESCRIPTION

[0020] See also Figure 3 The present invention is provided with an input matching unit 1, an amplifying unit 2, a feedback unit 3, a load unit 4 and a gain switching unit 5. The RF input single-ended signal is connected to the input matching unit 1, the output of the input matching unit 1 is connected to the amplifying unit, the amplifying unit 2 is connected to the input of the feedback unit 3, the feedback unit 3 is connected to the input of the input matching unit 1, the amplifying unit 2 is simultaneously connected to the output load unit 4, the output load unit 4 outputs the RF double-ended RF signal, and the gain switching unit is connected to the feedback unit and the load unit.

[0021] See also Figure 4 , the RF input signal passes through the input matching unit 1, and is amplified by the amplifier unit 2. A part of the amplified signal passes through the feedback unit 3 to the input signal, and the other part passes through the load unit 4 to finally output the RF output signal. The gain switching unit controls the high and low gain switching of the low noise amplifier through the signal V1. Among them: the matching unit 1 is provided with inductors L1 and L2; the amplifier unit 2 is provided with NMOS tubes M1 and M2; the feedback unit 3 is provided with a resistor R1 and a capacitor C1; the load unit 4 is provided with capacitors C2 and C3, a resistor R2 and a transformer T1, and the transformer T1 includes inductors L3 and L4; the gain switching unit 5 is provided with a PMOS tube M3, an NMOS tube M4, and resistors R3 and R4. The connection relationship of the circuit is as follows:

[0022] The RF input signal is respectively connected to the inductor L1 of the input matching unit 1 and the capacitor C1 in the feedback unit 3, the inductor L1 is connected to the gate of the transistor M1 in the amplification unit 2, the source of the transistor M1 is connected to the inductor L2, the inductor L2 is grounded, the drain of the transistor M1 is connected to the source of the transistor M2, the gate of the transistor M1 is connected to the bias voltage VG, the gate of the transistor M2 is connected to the power supply voltage, the bias voltage of the transistor M2 is provided by the power supply voltage, the drain of the transistor M2 is respectively connected to the resistor R1 in the feedback unit 3, the capacitor C2 in the load unit 4 and the inductor L3 in the transformer T1, the resistor R1 in the feedback unit is connected to the capacitor C1, the capacitor C2 in the load unit and the inductor L3 in the transformer T1 are connected to the power supply voltage, the inductor L4 in the transformer T1 and the capacitor C3 and the resistor R2 are connected in parallel, and are simultaneously connected to the output RF signal, the source of the transistor M3 is connected to the power supply, and the gate of the transistor M3 is connected to the control signal The drain of transistor M3 is connected to one end of resistor R3, the other end of resistor R3 is connected to the drain of transistor M2 in the amplifying unit, the drain of transistor M4 is connected to the drain of transistor M2 in the amplifying unit, the gate of transistor M4 is connected to the control signal V1, the source of transistor M4 is connected to one end of resistor R4, and the other end of resistor R4 is connected to one end of capacitor C1 in the feedback unit.

[0023] The present invention introduces a transistor M4 and a resistor R4, and while reducing the gain of the resistor feedback common-source low-noise amplifier, maintains the broadband characteristics of input matching in a low-gain mode, thereby realizing a gain-switchable broadband resistor feedback low-noise amplifier. Figure 5 The S parameter simulation results of the low noise amplifier of the present invention at different gain levels are shown. It can be seen that in the high gain mode, S21 is about 15dB in 2.5-6GHz, S11 is less than -10 in 2.5-6GHz, and in the low gain mode, S21 is about 8dB in 2.5-6GHz, S11 is less than -11dB in 2.5-6GHz. In addition, the low noise amplifier achieves a lower noise figure. Figure 6The figure shows the noise figure simulation results of different gain levels. In the high gain mode, the noise figure is less than 1.43 in the range of 2.5-6GHz. In the low gain mode, the noise figure is less than 2.22 in the range of 2.5-6GHz.

Claims

1. A broadband resistor feedback gain variable low noise amplifier, characterized in that: It includes an input matching unit, an amplifying unit, a feedback unit, a load unit and a gain switching unit; the RF input single-ended signal is connected to the input of the input matching unit, the output of the input matching unit is connected to the input of the amplifying unit, the output of the amplifying unit is respectively connected to the inputs of the feedback unit and the load unit, the output of the feedback unit is connected to the input of the input matching unit, and the load unit outputs a RF double-ended RF signal; the gain switching unit is connected to the feedback unit and the load unit, and the feedback coefficient of the feedback unit and the impedance of the load unit are switched through the gain switching unit.

2. A broadband resistive feedback variable gain low noise amplifier according to claim 1, characterized in that: The input matching unit includes an inductor L1 and an inductor L2, one end of the inductor L1 is respectively connected to the RF input single-ended signal and one end of C1 in the feedback unit, the other end of the inductor L1 is connected to the gate of the transistor M1 in the amplification unit, one end of the inductor L2 is connected to the source of the transistor M1 in the amplification unit, and the other end of the inductor L2 is grounded; The amplifying unit includes a transistor M1 and a transistor M2, the gate of the transistor M1 is connected to the other end of the inductor L1 in the input matching unit and the bias voltage VG, the source of the transistor M1 is connected to one end of the inductor L2 in the input matching unit, the drain of the transistor M1 is connected to the source of the transistor M2, the gate of the transistor M2 is connected to the power supply, and the drain of the transistor M2 is respectively connected to one end of R1 in the feedback unit, one end of the capacitor C2 in the load unit, and one end of the inductor L3 in the transformer T1 in the load unit; The feedback unit includes a resistor R1 and a capacitor C1, one end of the resistor R1 is respectively connected to the drain of the transistor M2 in the amplification unit, one end of C2 in the load unit and one end of the first inductor L3 in the transformer T1 in the load unit, the other end of the resistor R1 is connected to one end of the capacitor C1, and the other end of the capacitor C1 is connected to one end of the inductor L1 in the input matching unit; The load unit includes capacitors C2 and C3, a resistor R2, and a transformer T1. The transformer T1 includes inductors L3 and L4. One end of the capacitor C2 is respectively connected to the drain of the transistor M2 in the amplification unit, one end of R1 in the feedback unit, and one end of the inductor L3. The other end of the capacitor C2 is connected to the power supply. One end of the inductor L3 is respectively connected to the drain of the transistor M2 in the amplification unit, one end of R1 in the feedback unit, and one end of the capacitor C2. The other end of the inductor L3 is connected to the power supply. One end of the inductor L4 is respectively connected to one end of the capacitor C3 and the resistor R2. The other end of the inductor L4 is respectively connected to the other end of the capacitor C3 and the resistor R2. Both ends of the inductor L4, the capacitor C3, and the resistor R2 are connected to both ends of the RF output signal.

3. A broadband resistive feedback variable gain low noise amplifier according to claim 2, characterized in that: The gain switching unit includes transistors M3, M4, resistors R3 and R4, the source of transistor M3 is connected to the power supply, The gate of transistor M3 is connected to the control signal The drain of transistor M3 is connected to one end of resistor R3, the other end of resistor R3 is connected to the drain of transistor M2 in the amplifying unit, the drain of transistor M4 is connected to the drain of transistor M2 in the amplifying unit, the gate of transistor M4 is connected to the control signal V1, the source of transistor M4 is connected to one end of resistor R4, and the other end of resistor R4 is connected to one end of capacitor C1 in the feedback unit.

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