Negative feedback low-noise amplifier with working frequency band capable of being digitally controlled

Abstract

The invention discloses a negative feedback low-noise amplifier capable of digitally controlling a working frequency band. RFin is connected with a positive end of L1 and a positive end of C0 and is connected with V0; the negative end of the L1 is connected with GND; the negative end of C0, the positive end of L2 and the positive end of C1 are connected with V1; the negative end of the L2 is connected with the GND; the negative end of C1, the negative end of L3, the positive end of R1 and the grid electrode of M1 are connected with V2; the positive end of the L3, the negative end of the C2 and the VG are connected with the V3; the negative end of the C2 is connected with the GND; the positive end of R1 is connected with the source electrode of M2; the grid electrode of M2 is connected with the negative electrode of R2; the positive electrode of R2 is connected with VC; the drain electrode of M2 is connected with the positive end of L4; the source electrode of the M1 is connected with the positive end of the L8; the negative end of the L1 is connected with the GND; the drain electrode of M1, the negative end of L4, the negative end of L5 and the positive end of C5 are connected with V5; the positive end of the L5, the negative end of the C4 and the VD are connected with the V4; the positive end of the C4 is connected to the GND; the negative end of C5, the positive end of L6 and the positive end of C6 are connected with V6; the negative end of the L6 is connected with the GND; the negative end of the C6 is connected with the positive end of the L7 and the positive end of the C7 is connected with the V7; the negative end of the L7 is connected with the GND; the negative end of the C7 is connected with the RFout; through digital signal control, on the premise of not sacrificing performance, the working frequency of the low-noise amplifier can be switched, and signals with different frequencies can be received.

Description

Technical Field

[0001] The invention relates to the technical field of radio frequency circuits, in particular to a negative feedback low noise amplifier with a digitally controllable working frequency band. Background Art

[0002] In recent years, with the development and upgrading of information technology, the application of wireless communication technology has become more and more extensive. As a key unit of the wireless communication system, the performance of the transceiver determines the communication quality of the entire wireless system. Among them, the low noise amplifier is a key component of the RF front end. It is located at the front end of the entire receiver system. As the first active amplifier in the receiving link, its performance directly determines the performance of the receiving system.

[0003] The signals received by the low noise amplifier are often different frequency points within a certain frequency range, rather than the entire frequency range. For example, the operating frequency of WiFi4 is 2.4GHz, and the operating frequency of WiFi5 is 5GHz. The operating frequency of the traditional low noise amplifier is designed to be within the entire frequency range including the operating frequency point. Although the operating frequency bandwidth is wide, other performance of the low noise amplifier is weakened, especially the gain. If the circuit gain needs to be increased, it can only be achieved by cascading multiple circuits, which will increase the complexity and physical size of the circuit.

[0004] In order to achieve broadband design for receiving discrete channel signals, traditional low noise amplifiers often need to sacrifice other performance of the low noise amplifier or increase circuit complexity and design complexity. Summary of the invention

[0005] The purpose of the present invention is to provide a negative feedback low noise amplifier with digitally controllable working frequency band. The present invention has the advantages of being able to switch working frequency and receive signals of different frequencies without sacrificing other performances.

[0006] The technical solution of the present invention is: a negative feedback low noise amplifier with digitally controllable working frequency band, wherein the RF input terminal, the positive terminal of the first inductor and the positive terminal of the zeroth capacitor are all connected to V0; the negative terminal of the first inductor is connected to GND;

[0007] The negative end of the zero capacitor, the positive end of the second inductor and the positive end of the first capacitor are all connected to V1; the negative end of the second inductor is connected to GND;

[0008] The negative end of the first capacitor, the negative end of the third inductor, the positive end of the first resistor and the gate of the first effect tube are all connected to V2; the positive end of the third inductor, the negative end of the second capacitor and the gate bias voltage input terminal are all connected to V3; the negative end of the second capacitor is connected to GND;

[0009] The positive end of the first resistor is connected to the source of the second effect tube; the gate of the second effect tube is connected to the negative electrode of the second resistor; the positive electrode of the second resistor is connected to the circuit control voltage enable terminal; the drain of the second effect tube is connected to the positive end of the fourth inductor;

[0010] The source of the No. 1 effect tube is connected to the positive end of the No. 8 inductor; the negative end of the No. 1 inductor is connected to GND; the drain of the No. 1 effect tube, the negative end of the No. 4 inductor, the negative end of the No. 5 inductor and the positive end of the No. 5 capacitor are all connected to V5;

[0011] The positive end of the fifth inductor, the negative end of the fourth capacitor and the drain bias voltage input terminal are all connected to V4; the positive end of the fourth capacitor is connected to GND;

[0012] The negative end of the fifth capacitor, the positive end of the sixth inductor and the positive end of the sixth capacitor are all connected to V6; the negative end of the sixth inductor is connected to GND;

[0013] The negative end of the sixth capacitor, the positive end of the seventh inductor and the positive end of the seventh capacitor are all connected to V7; the negative end of the seventh inductor is connected to GND; the negative end of the seventh capacitor is connected to the RF output terminal.

[0014] In the aforementioned negative feedback low noise amplifier with digitally controllable working frequency band, the first effect transistor and the second effect transistor are both N-type enhancement field effect transistors under the gallium arsenide semiconductor compound pHEMT process.

[0015] In the aforementioned negative feedback low noise amplifier with digitally controllable working frequency band, the first effect tube is a low noise amplifier transistor, and the second effect tube is a switch transistor.

[0016] In the aforementioned negative feedback low noise amplifier with digitally controllable working frequency band, the first resistor and the second resistor are metallic resistors, and the resistance values ​​of the first resistor and the second resistor are different.

[0017] In the aforementioned negative feedback low noise amplifier with digitally controllable operating frequency band, the capacitance values ​​of the first capacitor, the second capacitor, the third capacitor, the fourth capacitor, the fifth capacitor and the sixth capacitor are different.

[0018] In the aforementioned negative feedback low noise amplifier with digitally controllable working frequency band, the inductance values ​​of the inductor No. 1, inductor No. 2, inductor No. 3, inductor No. 4, inductor No. 5, inductor No. 6, inductor No. 7 and inductor No. 8 are different.

[0019] Compared with the prior art, the present invention designs a negative feedback low noise amplifier with digitally controllable working frequency band, that is, through the control of digital signals, the low noise amplifier can work at different frequencies with the same high gain; it solves the problem that the low noise amplifier is designed as a broadband low noise amplifier due to the need to cover different working frequencies, resulting in reduced gain. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a circuit schematic diagram of the present invention;

[0021] Figure 2 It is a schematic diagram of transistor on-off equivalent of the present invention;

[0022] Figure 3 It is a simplified model of the transistor negative feedback circuit of the present invention;

[0023] Figure 4 is a gain comparison diagram of the low noise amplifier in the 2.4 GHz and 5 GHz modes according to an embodiment of the present invention;

[0024] Figure 5 is the noise figure of the low noise amplifier at 2.4 GHz according to an embodiment of the present invention;

[0025] Figure 6 is the reflection coefficient of the low noise amplifier at 2.4 GHz in an embodiment of the present invention;

[0026] Figure 7 is the noise coefficient of the low noise amplifier at 5 GHz according to an embodiment of the present invention;

[0027] Figure 8 is the reflection coefficient of the low noise amplifier of the embodiment of the present invention at 5 GHz.

[0028] Markings in the accompanying drawings: M1-effect transistor No. 1, M2-effect transistor No. 2, R1-first resistor, R2-second resistor, C0-zeroth capacitor, C1-first capacitor, C2-second capacitor, C3-third capacitor, C4-fourth capacitor, C5-fifth capacitor, C6-sixth capacitor, C7-seventh capacitor, L1-inductor No. 1, L2-inductor No. 2, L3-inductor No. 3, L4-inductor No. 4, L5-inductor No. 5, L6-inductor No. 6, L7-inductor No. 7, L8-inductor No. 8, RFin-RF input, RFout-RF output, VG-gate bias voltage input, VD-drain bias voltage input, VC-circuit control voltage enable. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the present invention.

[0030] Embodiment. A negative feedback low noise amplifier with digitally controllable operating frequency band, such as Figure 1 As shown, the RF input terminal RFin, the positive end of the first inductor L1 and the positive end of the zeroth capacitor C0 are all connected to V0; the negative end of the first inductor L1 is connected to GND;

[0031] The negative end of the zero capacitor C0, the positive end of the second inductor L2 and the positive end of the first capacitor C1 are all connected to V1; the negative end of the second inductor L2 is connected to GND;

[0032] The negative end of the first capacitor C1, the negative end of the third inductor L3, the positive end of the first resistor R1 and the gate of the first effect transistor M1 are all connected to V2; the positive end of the third inductor L3, the negative end of the second capacitor C2 and the gate bias voltage input terminal VG are all connected to V3; the negative end of the second capacitor C2 is connected to GND;

[0033] The positive end of the first resistor R1 is connected to the source of the second effect tube M2; the gate of the second effect tube M2 is connected to the negative electrode of the second resistor R2; the positive electrode of the second resistor R2 is connected to the circuit control voltage enable terminal VC; the drain of the second effect tube M2 is connected to the positive end of the fourth inductor L4;

[0034] The source of the first effect tube M1 is connected to the positive end of the eighth inductor L8; the negative end of the first inductor L1 is connected to GND; the drain of the first effect tube M1, the negative end of the fourth inductor L4, the negative end of the fifth inductor L5 and the positive end of the fifth capacitor C5 are all connected to V5;

[0035] The positive end of the fifth inductor L5, the negative end of the fourth capacitor C4 and the drain bias voltage input terminal VD are all connected to V4; the positive end of the fourth capacitor C4 is connected to GND;

[0036] The negative end of the fifth capacitor C5, the positive end of the sixth inductor L6 and the positive end of the sixth capacitor C6 are all connected to V6; the negative end of the sixth inductor L6 is connected to GND;

[0037] The negative end of the sixth capacitor C6, the positive end of the seventh inductor L7 and the positive end of the seventh capacitor C7 are all connected to V7; the negative end of the seventh inductor L7 is connected to GND; the negative end of the seventh capacitor C7 is connected to the RF output terminal RFout.

[0038] The first effect transistor M1 and the second effect transistor M2 are both N-type enhancement mode field effect transistors under the pHEMT process of gallium arsenide semiconductor compound.

[0039] The first effect transistor M1 is a low noise amplifier transistor, and the second effect transistor M2 is a switch transistor.

[0040] The first resistor R1 and the second resistor R2 are metallic resistors, and the first resistor R1 and the second resistor R2 have different resistance values.

[0041] The capacitance values ​​of the first capacitor C1 , the second capacitor C2 , the third capacitor C3 , the fourth capacitor C4 , the fifth capacitor C5 , and the sixth capacitor C6 are different.

[0042] The inductance values ​​of the inductor No. 1 L1 , the inductor No. 2 L2 , the inductor No. 3 L3 , the inductor No. 4 L4 , the inductor No. 5 L5 , the inductor No. 6 L6 , the inductor No. 7 L7 , and the inductor No. 8 L8 are different.

[0043] Implementation principle:

[0044] The digital control of the present invention is realized by switching on and off the transistor. In order to analyze the control function of the switch transistor more simply and intuitively, the working state of the switch transistor can be simplified to be equivalent to Figure 2 shown.

[0045] When the gate-source voltage V gs Greater than the transistor threshold voltage V th When the transistor is turned on, the transistor can be equivalent to an on-resistance R on , whose size is:

[0046]

[0047] Where μ is the electron mobility of the transistor, C ox is the gate oxide capacitance per unit area of ​​the transistor, W is the gate width of the transistor, and L is the gate length of the transistor. From formula (1), it can be seen that when the transistor is turned on, the on-resistance of the transistor is inversely proportional to the width-to-length ratio of the transistor.

[0048] When the gate-source voltage V gs Less than the transistor's turn-on voltage V th When the transistor is cut off, the transistor can be equivalent to the series-parallel connection of gate, drain and source capacitors, and a turn-off capacitor C off To express:

[0049]

[0050] Among them, C gs is the gate-source capacitance of the transistor, C gd is the gate-drain capacitance of the transistor, C ds is the drain-source capacitance of the transistor.

[0051] When the gate-source voltage V gs Greater than the transistor threshold voltage V th When the switch transistor M2 is turned on, it can be equivalent to a very small on-resistance, which together with the resistor R1 forms a feedback resistor R f :

[0052] R f =R1+R on (3)

[0053] On-resistance R on The size is about a few ohms.

[0054] At this time, the low noise amplifier structure is a resistor parallel feedback structure, and its transistor negative feedback circuit simplified model is as follows: Figure 3 As shown;

[0055] Ignore the gate-source capacitance C gs The influence of can be obtained as follows:

[0056]

[0057] The corresponding S parameters are

[0058]

[0059]

[0060]

[0061] Where Z0 is the characteristic impedance, R f is the resistance of the parallel negative feedback resistor.

[0062] In the case of matching, S 11 =S 22 =0, that is, input-output VSWR=1, then:

[0063]

[0064]

[0065] As shown in equation (6), the gain of the parallel negative feedback amplifier is mainly determined by R f The decision has nothing to do with frequency.

[0066] In this way, by adjusting the feedback resistor R f To adjust the gain, you can also adjust the gain flatness of the circuit.

[0067] When the gate-source voltage V gs Less than the transistor's turn-on voltage V th When , the switch transistor M2 is turned off, the feedback resistor is disconnected, and the circuit structure of the low noise amplifier is a source negative feedback low noise amplifier structure. This structure can increase the circuit gain and has good noise performance.

[0068] In summary, when M2 is turned on, the low noise amplifier operates at frequency f1; when M2 is turned off, the low noise amplifier operates at frequency f2. Therefore, the operating frequency band of the negative feedback low noise amplifier can be digitally controlled.

[0069] like Figure 4-8As shown, the present invention designs and implements a negative feedback low noise amplifier with digitally controllable working frequency band. The working frequencies of the final simulation results of the circuit are 2.4GHz and 5GHz respectively. At 2.4GHz, the noise figure nf(2) = 0.953, the gain S(2,1) = 7.203dB, S(1,1) = -17.645dB, S(2,2) = -22.724dB; at 5GHz, the noise figure nf(2) = 0.327, the gain S(2,1) = 7.029dB, S(1,1) = -14.688dB, S(2,2) = -15.745dB.

[0070] Therefore, it can be used for WIFI4, WiFi5 and WiFi6 receiving front ends.

Claims

1. A negative feedback low noise amplifier with digitally controllable operating frequency band, characterized in that: The RF input terminal (RFin), the positive terminal of the first inductor (L1) and the positive terminal of the zeroth capacitor (C0) are all connected to V0; the negative terminal of the first inductor (L1) is connected to GND; The negative end of the zero capacitor (C0), the positive end of the second inductor (L2) and the positive end of the first capacitor (C1) are all connected to V1; the negative end of the second inductor (L2) is connected to GND; The negative end of the first capacitor (C1), the negative end of the third inductor (L3), the positive end of the first resistor (R1) and the gate of the first effect transistor (M1) are all connected to V2; the positive end of the third inductor (L3), the negative end of the second capacitor (C2) and the gate bias voltage input terminal (VG) are all connected to V3; the negative end of the second capacitor (C2) is connected to GND; The positive end of the first resistor (R1) is connected to the source of the second effect tube (M2); the gate of the second effect tube (M2) is connected to the negative electrode of the second resistor (R2); the positive electrode of the second resistor (R2) is connected to the circuit control voltage enable terminal (VC); the drain of the second effect tube (M2) is connected to the positive end of the fourth inductor (L4); The source of the first effect tube (M1) is connected to the positive end of the eighth inductor (L8); the negative end of the first inductor (L1) is connected to GND; the drain of the first effect tube (M1), the negative end of the fourth inductor (L4), the negative end of the fifth inductor (L5) and the positive end of the fifth capacitor (C5) are all connected to V5; The positive end of the fifth inductor (L5), the negative end of the fourth capacitor (C4) and the drain bias voltage input terminal (VD) are all connected to V4; the positive end of the fourth capacitor (C4) is connected to GND; The negative end of the fifth capacitor (C5), the positive end of the sixth inductor (L6) and the positive end of the sixth capacitor (C6) are all connected to V6; the negative end of the sixth inductor (L6) is connected to GND; The negative end of the sixth capacitor (C6), the positive end of the seventh inductor (L7) and the positive end of the seventh capacitor (C7) are all connected to V7; the negative end of the seventh inductor (L7) is connected to GND; the negative end of the seventh capacitor (C7) is connected to the RF output terminal (RFout).

2. A negative feedback low noise amplifier with digitally controllable operating frequency band according to claim 1, characterized in that: The first effect transistor (M1) and the second effect transistor (M2) are both N-type enhancement field effect transistors under the gallium arsenide semiconductor compound pHEMT process.

3. A negative feedback low noise amplifier with digitally controllable operating frequency band according to claim 2, characterized in that: The first effect transistor (M1) is a low noise amplifier transistor, and the second effect transistor (M2) is a switch transistor.

4. The negative feedback low noise amplifier with digitally controllable operating frequency band according to claim 1, characterized in that: The first resistor (R1) and the second resistor (R2) are metallic resistors, and the first resistor (R1) and the second resistor (R2) have different resistance values.

5. The negative feedback low noise amplifier with digitally controllable working frequency band according to claim 1, characterized in that: The capacitance values ​​of the first capacitor (C1), the second capacitor (C2), the third capacitor (C3), the fourth capacitor (C4), the fifth capacitor (C5), and the sixth capacitor (C6) are different.

6. The negative feedback low noise amplifier with digitally controllable working frequency band according to claim 1, characterized in that: The inductance values ​​of the inductor No. 1 (L1), the inductor No. 2 (L2), the inductor No. 3 (L3), the inductor No. 4 (L4), the inductor No. 5 (L5), the inductor No. 6 (L6), the inductor No. 7 (L7), and the inductor No. 8 (L8) are different.

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