CN115913130A - A Reconfigurable Broadband Low Noise Amplifier Structure - Google Patents

Abstract

A low noise amplifier structure capable of reconstructing broadband comprises a field effect tube M1, wherein the grid electrode of the field effect tube M1 is connected with a radio frequency input end RFin, the drain electrode of the field effect tube M is connected with a radio frequency output end RFout, and the source electrode of the field effect tube M is grounded after being connected with an inductor L3 in series; the feedback circuit further comprises a feedback switch SW1, a feedback switch SW2, a resistor R1 and a capacitor C2, wherein the feedback switch SW1, the feedback switch SW2 and the resistor R1 are sequentially connected in series to form a feedback branch, and two ends of the feedback branch are respectively connected with the grid electrode and the drain electrode of the field effect tube M1; the capacitor C2 is connected in series between the drain of the field effect transistor M1 and the radio frequency output terminal RFout. The invention is suitable for various processes, can adjust the width of the FET and expands the bandwidth of the LNA circuit by optimizing matching, so that the LNA circuit can obtain enough gain and linearity and low noise coefficient in a working frequency band.

Description

A Reconfigurable Broadband Low Noise Amplifier Structure

technical field

The invention relates to the technical field of radio frequency front-end integrated circuits in the communication industry, in particular to a reconfigurable broadband low-noise amplifier structure.

Background technique

With the rapid development and evolution of 5G communications, spectrum resources are becoming increasingly scarce. In order to meet the needs of different frequency bands in the modern communication field, in some applications such as high-speed transceivers, instrument systems, high-resolution radar and imaging systems, the RF front-end needs to meet multi-frequency or broadband work.

Wideband Low Noise Amplifier (LNA) is an important part of system receivers, providing them with higher sensitivity and bandwidth, and because the system works on broadband, it meets the requirements of high gain, low noise figure (NF) and good linearity The design of wideband LNA is challenging, and reconfigurable technology will become a research hotspot in the industry.

The circuit connection method of a type of amplifier structure in the prior art is shown in Figure 1, which adopts the adjustment method of the RC feedback circuit, specifically, the inductor and capacitor connected in series are connected from the drain to the gate of the transistor pole feedback branch. Since the weak signal transmitted by the antenna is directly received, and in order to suppress the impact of the noise of the subsequent stage circuit on the total noise, the LNA needs sufficient gain; however, if a traditional RC feedback circuit is added to each stage of the amplifying circuit, although the bandwidth can be expanded, it will be This leads to serious gain loss, adding only one level will make the bandwidth unable to meet the demand and not flexible enough.

Contents of the invention

The main purpose of the present invention is to propose a reconfigurable broadband low noise amplifier structure, through the FET feedback switch, the amplifier can be reconfigured to achieve broadband LNA, so that it can be applied to more operating frequency bands, aiming to solve the above-mentioned traditional The existing RC feedback network has the problems of low gain and insufficient bandwidth expansion.

In order to achieve the above object, the present invention proposes a reconfigurable broadband low-noise amplifier structure, including a field effect transistor M1, its gate is connected with the radio frequency input terminal RFin, its drain is connected with the radio frequency output terminal RFout, and its source Connect the inductance L3 in series and ground it;

It also includes a feedback switch SW1, a feedback switch SW2, a resistor R1, a capacitor C2 and a capacitor C3, the feedback switch SW1, the feedback switch SW2 and the resistor R1 are sequentially connected in series to form a feedback branch, and the two ends of the feedback branch are respectively connected to the field effect transistor Gate and drain connections of M1;

The capacitor C2 is connected in parallel to both ends of the feedback switch SW2, and the capacitor C3 is connected in series between the drain of the field effect transistor M1 and the RF output terminal RFout.

Preferably, an inductor L2 is also included, and the feedback switch SW1, the feedback switch SW2, the resistor R1 and the inductor L2 are sequentially connected in series to form a feedback branch, and the two ends of the feedback branch are respectively connected to the gate and drain of the field effect transistor M1 .

Preferably, a capacitor C1 is further included, and the capacitor C1 is connected in series between the gate of the field effect transistor M1 and the radio frequency input terminal RFin.

Preferably, an inductor L1 is also included, one end of the inductor L1 is connected between the capacitor C1 and the gate of the field effect transistor M1, and the other end of the inductor L1 is connected to the bias voltage Vbias

Preferably, a capacitor C4 is further included, one end of the capacitor C3 is connected between the capacitor C3 and the radio frequency output terminal RFout, and the other end of the capacitor C4 is grounded.

Preferably, an inductor L4 is further included, one end of the inductor L4 is connected between the capacitor C3 and the drain of the field effect transistor M1, and the other end of the inductor L4 is connected to the working voltage Vdd.

The invention is applicable to various processes, can adjust the width of the FET and expand the bandwidth of the LNA circuit by optimizing matching, so that it can obtain sufficient gain and linearity and a low noise figure in the working frequency band; by switching the power supply voltage of the FET, the LNA can be controlled Switching of the operating frequency band, and even if there is a mismatch between devices and random errors in process manufacturing or the chip has been packaged, the circuit matching can be adjusted by changing the power supply voltage.

Description of drawings

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 that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained according to the structures shown in these drawings without creative effort.

Fig. 1 is the amplifier structure that adopts RC feedback circuit in the prior art;

Fig. 2 is a schematic circuit structure diagram of an embodiment of the low noise amplifier structure of the present invention;

Fig. 3 is the substantive circuit structure schematic diagram when the feedback switch of FET among the present invention is in conduction state;

FIG. 4 is a schematic diagram of the actual circuit structure when the feedback switch of the FET is in the off state in the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

It should be noted that if there is a directional indication (such as up, down, left, right, front, back...) in the embodiment of the present invention, the directional indication is only used to explain the position in a certain posture (as shown in the accompanying drawing). If the specific posture changes, the directional indication will also change accordingly.

In addition, if there are descriptions involving "first", "second" and so on in the embodiments of the present invention, the descriptions of "first", "second" and so on are only for descriptive purposes, and should not be interpreted as indicating or implying Its relative importance or implicitly indicates the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In addition, the technical solutions of the various embodiments can be combined with each other, but it must be based on the realization of those skilled in the art. When the combination of technical solutions is contradictory or cannot be realized, it should be considered that the combination of technical solutions does not exist , nor within the scope of protection required by the present invention.

The solutions of the present invention will be further described below in conjunction with FIGS. 2-4 and related embodiments.

As shown in Figure 2, a reconfigurable broadband low-noise amplifier structure includes a field effect transistor M1, its gate is connected to the RF input terminal RFin, its drain is connected to the RF output terminal RFout, and its source is connected in series with an inductor Ground after L3;

It also includes a feedback switch SW1, a feedback switch SW2, a resistor R1, a capacitor C2 and a capacitor C3, the feedback switch SW1, the feedback switch SW2 and the resistor R1 are sequentially connected in series to form a feedback branch, and the two ends of the feedback branch are respectively connected to the field effect transistor Gate and drain connections of M1;

The capacitor C2 is connected in parallel to both ends of the feedback switch SW2, and the capacitor C3 is connected in series between the drain of the field effect transistor M1 and the RF output terminal RFout.

The present invention utilizes the FET feedback switch of high FOM (figure of merit), and the amplifier structure can be reconfigured to realize high gain, low noise figure (NF) and good linear broadband LNA, and its working principle is specifically as follows:

As shown in Figure 3, when the feedback switch of the FET is in the on state, the FET works in the Deep-triode Region, which is equivalent to a series resistance, defined as the on-resistance Ron, which can be initially summarized by the following formula:

Among them, L and W refer to the length and width of the FET gate (gate), V _GS refers to the gate-source voltage, and Vth represents the threshold voltage; K is a constant representing the multiplication factor, and different types of FETs have different values. From the formula (1) we can see that Ron is inversely proportional to the width W of the FET.

As shown in Figure 4, when the feedback switch of the FET is in the off state, the FET works in the cut-off state (Cut-offRegion), and there is a parasitic capacitance between the gate, drain and source of the FET, making it equivalent to a series Capacitance, defined as the off-capacitance Coff, can be initially summarized by the following formula:

C _off ＝C _gd //C _gs +C _other ＝WC _t +C _other (2)

Among them, W refers to the gate width of the FET, Cgd and Cgs refer to the equivalent gate-drain and gate-source capacitances, which are proportional to the tube width W, and Ct is the total equivalent gate-drain and gate-source capacitance per unit gate width Value; Cother refers to the sum of other capacitance parasitic effects, such as body or substrate parasitic coupling. From the formula (2) we can see that Coff is proportional to the width W of the FET.

FOM=BV2/Ron, BV is the breakdown voltage, high FOM value means higher breakdown voltage and lower on-resistance Ron.

From the above analysis, it can be seen that the FET is used as an adjustable switch. When the FET is in the on state, the width of the FET and the gate-source voltage can be adjusted to change the value of the on-resistance Ron. When the FET is in the off state, the FET can be adjusted. The width changes the value of the off-capacitor Coff,

Specifically as shown in Figure 2, the FET feedback switch is added to the feedback branch from the drain to the gate of the transistor. When SW1 is turned off, the off-capacitor is connected in series with C2, and the capacitance decreases. When SW2 is off, its off-capacitance Connected in parallel with C2, the capacitance increases; when SW1 is turned on, its on-resistance is connected in parallel with C2 and then connected in series with R1, when SW2 is turned on, its on-resistance is connected in series with R1, and the resistance value increases. Therefore, the switching of the working frequency band of the LNA can be controlled by switching or changing the FET power supply voltage, and the matching can be optimized to obtain sufficient gain, linearity and low noise figure in the working frequency band.

Further, it also includes an inductor L2, the feedback switch SW1, the feedback switch SW2, the resistor R1 and the inductor L2 are sequentially connected in series to form a feedback branch, and the two ends of the feedback branch are respectively connected to the gate and drain of the field effect transistor M1 , the inductor L2 plays a role in adjusting the matching in the feedback branch.

Further, a capacitor C1 is further included, and the capacitor C1 is connected in series between the gate of the field effect transistor M1 and the radio frequency input terminal RFin.

Further, it also includes an inductor L1, one end of the inductor L1 is connected between the capacitor C1 and the gate of the field effect transistor M1, the other end of the inductor L1 is connected to the bias voltage Vbias, and the inductor L1 prevents the radio frequency signal (RFin) from entering the power supply ( Vbias) and play a matching role.

Further, a capacitor C4 is further included, one end of the capacitor C4 is connected between the capacitor C3 and the radio frequency output terminal RFout, and the other end of the capacitor C4 is grounded.

Further, an inductance L4 is also included, one end of the inductance L4 is connected between the capacitor C3 and the drain of the field effect transistor M1, the other end of the inductance L4 is connected to the working voltage Vdd, and the inductance L4 prevents the radio frequency signal flowing out of the drain from entering the power supply ( Vdd) and play a matching role.

The invention is applicable to various processes, can adjust the width of the FET and expand the bandwidth of the LNA circuit by optimizing matching, so that it can obtain sufficient gain and linearity and a low noise figure in the working frequency band; by switching the power supply voltage of the FET, the LNA can be controlled Switching of the operating frequency band, and even if there is a mismatch between devices and random errors in process manufacturing or the chip has been packaged, the circuit matching can be adjusted by changing the power supply voltage.

The above is only a preferred embodiment of the present invention, and does not therefore limit the patent scope of the present invention. Under the inventive concept of the present invention, the equivalent structural transformation made by using the description of the present invention and the contents of the accompanying drawings, or direct/indirect use All other relevant technical fields are included in the patent protection scope of the present invention.

Claims (6)

1. A low-noise amplifier structure of reconfigurable broadband is characterized in that: comprise FET M1, its gate is connected with radio frequency input end RFin, its drain is connected with radio frequency output end RFout, its source is connected in series with inductance Ground after L3; It also includes a feedback switch SW1, a feedback switch SW2, a resistor R1, a capacitor C2 and a capacitor C3, the feedback switch SW1, the feedback switch SW2 and the resistor R1 are sequentially connected in series to form a feedback branch, and the two ends of the feedback branch are respectively connected to the field effect transistor Gate and drain connections of M1; The capacitor C2 is connected in parallel to both ends of the feedback switch SW2, and the capacitor C3 is connected in series between the drain of the field effect transistor M1 and the RF output terminal RFout. 2. The low noise amplifier structure according to claim 1, characterized in that: it also includes an inductor L2, a feedback switch SW1, a feedback switch SW2, a resistor R1 and an inductor L2 are sequentially connected in series to form a feedback branch, and the feedback branch of the The two ends are respectively connected to the gate and the drain of the field effect transistor M1. 3 . The low noise amplifier structure according to claim 1 , further comprising a capacitor C1 connected in series between the gate of the field effect transistor M1 and the radio frequency input terminal RFin. 4. The low noise amplifier structure according to claim 3, characterized in that: it also includes an inductor L1, one end of the inductor L1 is connected between the capacitor C1 and the gate of the field effect transistor M1, and the other end of the inductor L1 is connected to the bias The voltage Vbias is connected. 5. The low noise amplifier structure according to claim 1, further comprising a capacitor C4, one end of the capacitor C4 is connected between the capacitor C3 and the radio frequency output terminal RFout, and the other end of the capacitor C4 is grounded. 6. The low noise amplifier structure according to claim 1, characterized in that: it also includes an inductor L4, one end of the inductor L4 is connected between the capacitor C3 and the drain of the field effect transistor M1, and the other end of the inductor L4 is connected to the operating voltage Vdd connection.

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