WO2012142893A1

WO2012142893A1 - Low noise amplifier protection switch

Info

Publication number: WO2012142893A1
Application number: PCT/CN2012/072480
Authority: WO
Inventors: 孙涵; 张煜; 李春阳; 阮金龙
Original assignee: 中兴通讯股份有限公司
Priority date: 2011-04-22
Filing date: 2012-03-16
Publication date: 2012-10-26
Also published as: CN102291090A

Abstract

Disclosed is a low noise amplifier protection switch. The common end of the switch is connected to an antenna, the transmitting end is connected to a load, and the receiving end is connected to a low noise amplifier. The common end is connected to the transmitting end via at least a first group of diodes and connected to the receiving end via at least a second group of diodes, wherein both the first group of diodes and the second group of diodes include diodes connected in parallel. The low noise amplifier protection switch solves the problem that the current low noise amplifier protection switch has small power capacity and low reliability, thus achieving the effect of improving power capacity and reliability.

Description

TECHNICAL FIELD The present invention relates to the field of communications, and in particular to a low noise amplifier protection switch. BACKGROUND OF THE INVENTION A low noise amplifier (referred to as a low noise amplifier) protection switch works as follows: Time division duplex system (Time

Division Duplex (TDD) When the amplifier is working in the power amplifier emission state, the function of this switch is to isolate the low noise of the receiving link and transmit the reflected RF signal to the RF power load. The function of high-frequency RF and protection of low noise is called low noise protection switch. In the low noise receiving state, this switch isolates the load. At this time, the low noise path is turned on to complete the reception amplification. As shown in FIG. 1, in the prior art, it is used in a time division duplex system (Time Division Duplex, referred to as

The low noise amplifier protection switch in TDD) is located between the circulator 3 port and the Low Noise Amplifier (LNA) in the circuit distribution, and controls the RF signal from the Circulator 3 port. The circulator 3 port is a radio port common to the downlink power reflection link and the uplink receiving link. The port 1 of the circulator is connected to a power amplifier (PA), and the port 2 (antenna, ANT for short). Connected, the low noise protection switch is connected to the LNA and the load respectively. At present, there are already series of switching circuit modules and devices developed for TDD power amplifiers and low noise amplifier units. The switch circuit modules have a small area occupied by printed circuit boards (PCBs) and the medium used. The substrate has the advantage of high thermal conductivity compared to ordinary PCB boards. However, the internal soldering process is complicated, and the internal devices are connected by gold wires, so the power capacity is small, the reliability is low, and the cost is also high. SUMMARY OF THE INVENTION The present invention provides a low noise amplifier protection switch to solve at least one of the problems of low power capacity and low reliability of the low noise protection switch in the prior art. According to an aspect of the present invention, a low noise amplifier protection switch is provided, wherein a common end of the switch is connected to the antenna, a transmitting end of the switch is connected to the load, a receiving end of the switch is connected to the low noise amplifier, and the common end is passed through at least one first The group diode is connected to the transmitting end, and the common terminal is connected to the receiving end by at least one second group of diodes, wherein the first group of diodes and the second group of diodes each comprise a diode connected in parallel. Preferably, the low noise amplifier protection switch further comprises: a third diode, one end of the third diode is connected between the second group of diodes and the receiving end, and the other end of the third diode is connected to the ground. Preferably, the number of diodes in at least two of the first set of diodes is different. Preferably, the number of diodes in at least two of the second set of diodes is different. Preferably, each of the first set of diodes and the second set of diodes comprises at least two diodes. Preferably, the first set of diodes is different in number from the second set of diodes. Preferably, the diodes are connected by a microstrip line. Preferably, the microstrip line length is less than 1/4 wavelength. Preferably, the diode is a plastic PIN diode. Preferably, the anode of the diode in the first group of diodes connected to the common terminal is connected to the common terminal, the cathode of the diode in the first group of diodes connected to the transmitting terminal is connected to the emitter end, and the second group of diodes connected to the common terminal The anode of the diode is connected to the common terminal, and the cathode of the diode of the second group of diodes connected to the receiving terminal is connected to the receiving end. Through the invention, the impedance is reduced by parallel diodes, and the problem of low power capacity and low reliability of the low noise protection switch in the prior art is solved, thereby achieving the effect of improving power capacity and reliability. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are set to illustrate,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a low noise amplifier protection switch circuit connection in a TDD power amplifier according to the related art; FIG. 2 is a preferred circuit diagram of a low noise amplifier protection switch according to an embodiment of the present invention; Another circuit diagram of the low noise amplifier protection switch. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. In the embodiment of the present invention, the switch for parallel connection of the diodes must use a 1/4 wavelength impedance conversion line. In order to adapt to the trend of miniaturization of the power amplifier board, the design is performed from the serial switch circuit of the diode. Embodiment 1 FIG. 2 is a preferred circuit diagram of a low noise amplifier protection switch according to an embodiment of the present invention, wherein the common terminal A of the low noise amplifier protection switch of FIG. 2 is connected to an antenna (ANT), and the transmitting end T of the switch is connected to Load D4, the receiving end R of the switch is connected to the low noise amplifier (LNA), the common terminal A is connected to the transmitting terminal T through at least one first group diode, and the common terminal is connected to the receiving terminal R through at least one second group diode, wherein The first set of diodes and the second set of diodes each comprise a parallel diode, the first set of diodes comprising VD7 and VD8 in parallel, and the second set of diodes comprising VD9 and VD10 in parallel. Wherein, if a plurality of diode pairs are included, the first group of diodes are connected in series, and the second group of diodes are connected in series. Preferably, the anode of the diode in the first group of diodes connected to the common terminal A is connected to the common terminal A, and the cathode of the diode in the first group of diodes connected to the transmitting terminal T is connected to the transmitting terminal T, and is connected to the common terminal A. The anode of the diode in the second set of diodes is connected to the common terminal A, and the cathode of the diode in the second group of diodes connected to the receiving terminal R is connected to the receiving terminal R. That is, the anodes of VD7 and DU8 are connected to the common terminal A, the cathode is connected to the emitter terminal T, the anodes of VD9 and DU10 are connected to the common terminal A, and the cathode is connected to the receiving terminal R. In the preferred embodiment, the impedance is reduced by parallel diodes, which solves the problem of low power capacity and low reliability of the low noise protection switch in the prior art, thereby achieving the effect of improving power capacity and reliability. Preferably, the low noise amplifier protection switch further comprises: a third diode VD13, one end of the third diode VD13 is connected between the second group of diodes and the receiving end R, and the other end of the third diode VD13 is connected to Ground. In the preferred embodiment, the third diode VD13 is employed to increase the isolation of the low noise amplifier protection switching circuit. In this embodiment, since the branch of the switch connected low noise amplifier (LNA) has high isolation requirement, when the antenna is open, the third diode VD13 is positively turned on, and when the high power signal reaches a high power load, The isolation between the low noise amplifier and the low noise amplifier is increased. At the same time, the number of the third diodes can be increased or decreased according to the requirements of the isolation index, and the use is flexible. When the transmitting branch of the switch is working, that is, the branch of the common terminal A to the transmitting terminal T is turned on, and the RF signal returned from the antenna port (ANT) is transmitted to the load terminal D4 through the left branch, and the right branch is now The parallel diodes are reverse biased off. At the same time, the diode VD13 is turned on, and the RF signal reflected from the antenna port (ANT) to the right branch passes through the VD13 to the ground, thereby improving the isolation and protecting the low noise. When the receiving branch of the switch is working, that is, the branch of the common terminal A to the receiving terminal R is turned on, and the anodes of the parallel diodes VD9 and VD10 are both positively biased, and the low noise amplifier (LNA) is turned on. The VD13 anode obtains a reverse bias voltage and reverse bias cutoff. The purpose of this reverse bias voltage is to ensure that the introduced insertion loss is minimized. The parallel diodes (VD7, VD8) of the transmitting branch are reverse biased. Preferably, the number of diodes in at least two of the first set of diodes is different. In the preferred embodiment, the same function of the different switching circuits is achieved by selecting different numbers of diodes, and the reliability and power capacity of the switching circuit are improved. Of course, the invention is not limited thereto, and the number of diodes in each diode pair may be the same. Preferably, the number of diodes in at least two of the second set of diodes is different. In the preferred embodiment, the same function of the different switching circuits is achieved by selecting different numbers of diodes, and the reliability and power capacity of the switching circuit are improved. Of course, the invention is not limited thereto, and the number of diodes in each diode pair may be the same. Preferably, each of the first set of diodes and the second set of diodes comprises at least two diodes. In the preferred embodiment, since the switching circuit is relatively inferior in heat dissipation compared with the integrated circuit module, in order to ensure the power transmission capability of the antenna to the link, it is necessary to reduce the insertion loss of the diode, and the switch with higher requirements is required. The insertion loss index of the circuit satisfies the requirement by increasing the number of parallel connections of the PIN diodes. The parallel use of such multiple diodes can improve the reliability of the switching circuit and increase the power capacity of the switching circuit. Preferably, the first set of diodes is different in number from the second set of diodes. In the preferred embodiment, by increasing the number of parallel PIN diode pairs in the circuit, that is, multiple sets of parallel diodes are used in series, the number of diodes can be flexibly controlled according to the requirements of the isolation index. Of course, the invention is not limited thereto, and the number of the first group of diodes and the second group of diodes may be the same. Preferably, the above diodes are connected by a microstrip line. In the preferred embodiment, since the loss (PD) of the diode is converted into heat, the heat is transmitted to the distal end along the microstrip conductor and on the other hand to the ground plane through the medium under the microstrip conductor (the environment) ). Clearly, the farther away from the PIN die, the less heat is transferred across the microstrip, and the smaller the temperature gradient across the microstrip. When the length of the microstrip line reaches a certain distance, the temperature of the microstrip line is independent of the tube, which can achieve the purpose of not affecting the heat dissipation of the diode. For the short microstrip line length between the diodes, a balanced voltage can be obtained for the diodes in series, and the microstrip line length between the diodes is calculated according to design requirements. Preferably, the microstrip line length is less than 1/4 wavelength, which is the wavelength at which electromagnetic waves are transmitted in the microstrip line. Preferably, the diode is a plastic PIN diode. In the preferred embodiment, a plastic PIN diode is used to ensure a low insertion loss to achieve a lower impedance. While the various indicators of the low noise amplifier switch protection circuit meet the requirements of use, it provides a reliable working environment for the power amplification path and the low noise path. At the same time, the complexity of the existing integrated switch module soldering process can be avoided, and the cost of the switch can be reduced. The low-noise protection switch for the TDD power amplifier can be provided with high power, high isolation, high stability, and adjustable architecture according to different index requirements. Circuit. Based on the circuit structure shown in FIG. 2, the following is a further description of how to select a PIN diode: In the preferred embodiment, a PIN diode having a large intrinsic thickness and a large junction is selected. When the diode is turned on, the difference is low. In the low noise amplifier branch, in order to improve the isolation of the switching circuit, the PIN diode VD13 connected in parallel to the ground is selected as a PIN diode with a large intrinsic thickness and a large junction. Although the equivalent capacitance value is large when it is reverse biased, it is suitable to select a PIN diode of this characteristic from the viewpoint of improving the isolation of the circuit by the forward conduction. After conducting comparison tests of PIN diodes in parallel and serial S-parameters of different manufacturers, comprehensive isolation, insertion loss, number of circuit components, etc., select appropriate PIN diodes on the two working branches of the switching circuit to construct the present invention. The low noise amplifier protection switch in the embodiment. Embodiment 2 FIG. 3 is another circuit diagram of a low noise amplifier protection switch according to an embodiment of the present invention, wherein a common terminal A of the switch is connected to the antenna ANT0_CIR, a transmitting end T of the switch is connected to the load D4, and a receiving end R of the switch is connected. To the low noise amplifier LNA0_1, the common terminal A is connected to the transmitting terminal T through two diode pairs, that is, a diode pair (or a group of diodes) including diodes VD7 and VD8 and a diode pair including diodes VD5 and VD6 (or one) Group diode), the common terminal 连接 is connected to the receiving terminal R through two diode pairs, that is, a diode pair including parallel diodes VD9 and VD10 and a diode pair including parallel diodes VD11 and VD12, including parallel diodes VD7 and VD8 The diode pair is connected in series with a diode pair comprising diodes VD5 and VD6 in parallel, comprising a diode pair of diodes VD9 and VD10 connected in parallel and a diode pair comprising diodes VD11 and VD12 connected in parallel. Preferably, the diodes VD7 and VD8 connected to the common terminal A and the anodes of the diodes VD5 and VD6 are connected to the common terminal A, the cathode is connected to the emitter terminal T, the diodes VD9 and VD10 connected to the common terminal A, and the anodes of the diodes VD11 and VD12. Connected to the common terminal A, the cathode is connected to the receiving terminal R. Of course, the present embodiment is merely an example, and the present invention is not limited to the above structure, wherein the number of diode pairs between the common terminal A and the transmitting terminal T may be greater than two, and the diode between the common terminal A and the receiving terminal R The number of pairs may also be greater than two. The polarity of the diode pair may be set such that the cathode is disposed at the transmitting end T or the receiving end R direction according to the circuit, the anode is disposed at the common end A direction, or the cathode is disposed at the common end A direction. , The anode is disposed at the transmitting end T or the receiving end R direction. Of course, the number of diodes connected in parallel in each diode pair can also be set to different quantities as needed. As shown in Figure 3, in this switching circuit, a voltage of 3.3V is often supplied. When the transmitting branch of the switch is working, when POW_RSW_H0_B is pulled to ground, POW_RSW_L0_B is raised to a high level of 28V. At this time, a group of parallel diodes VD7 and VD8 on the branch circuit obtain a 3.3V positive bias voltage and divide the voltage by 0.7V. Another group of parallel diodes VD5, VD6 anode obtains 2.6V positive bias voltage, the left branch of the switch circuit is turned on, and the RF signal reflected back from the antenna port ANT0_CIR is transmitted to the load terminal D4 through the left branch. Because POW_RSW_L0_B is raised to a high level of 28V at this time, the two sets of parallel diodes of the right branch are turned off. At the same time, the diode VD13 connected in parallel with the LNA0_1 terminal is turned on, and the RF signal reflected from the antenna port to the right channel passes through the VD13 to the ground, thereby achieving the purpose of improving isolation and protecting low noise. When the receiving branch of the switch is operating, POW_RSW_H0_B is raised to 28V when POW_RSW_H0_B is pulled to ground. At this time, the two sets of parallel diodes VD9, VD10, VD11, and VD12 on the right branch have a 3.3V positive bias voltage, and the low noise amplifier LNA0_1 is turned on. The VD13 anode obtains a reverse bias voltage of 28V and reverse biased off. At this time, the purpose of turning on the 28V reverse bias voltage is to ensure that the insertion loss introduced is minimized. At the same time, the parallel diodes VD7 and VD8 of the TX branch are reverse biased. Of course, this embodiment only describes how to reduce the difference and improve the isolation. The complete low noise protection switch circuit should also include a bypass capacitor, a RF inductor, a power supply bypass capacitor, and a bias resistor. It will not be described in detail in the present invention. Of course, in the present invention, in order to ensure the speed of the switch and reduce the power consumption of the driving circuit, it is necessary to add a driving circuit. In the driver circuit, the PP bipolar transistor is used instead of the pull-up resistor, which can effectively increase the speed of the switch. From the above description, it can be seen that the present invention achieves the following technical effects: With a new circuit layout method, after fully analyzing the characteristics of the packaged PIN diode, the heat conduction characteristics of the microstrip line, and the DC feed network, Circuit size, heat dissipation performance, high power, high isolation, low insertion loss, and the design of ordinary PCB board, Surface Mounted Technology (SMT) processing technology, low reliability The noise amplifier protects the switching circuit. Moreover, the structure of the circuit can be adjusted according to the index requirements of different products for the switching circuit. At the same time, compared with the existing integrated switch module, the PIN diode technology has the advantages of high maturity, low cost, simple welding process, and uses ordinary PCB board and SMT processing technology, which is suitable for mass production, and finally achieves performance and cost. Good combination. At the same time, depending on the power capacity, different requirements for isolation and insertion loss indicators, appropriate increase or decrease of diodes, to achieve diversified needs of base station products; to ensure the convenience and flexibility of use. At the same time, it is also possible to adapt to the requirements of different frequency bands by changing the inductance and capacitance of the parallel connection. The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

Claim

A low noise amplifier protection switch, a common end of the switch is connected to an antenna, a transmitting end of the switch is connected to a load, a receiving end of the switch is connected to a low noise amplifier, and the common end passes at least one A set of diodes is coupled to the transmit end, the common end coupled to the receive end by at least one second set of diodes, wherein the first set of diodes and the second set of diodes each comprise a diode in parallel.

2. The switch according to claim 1, further comprising: a third diode, one end of the third diode being connected between the second group of diodes and the receiving end, the The other end of the triple diode is connected to ground.

3. The switch of claim 1 wherein the number of diodes in at least two of said first set of diodes is different.

4. The switch of claim 1, wherein the number of diodes in at least two of the second set of diodes is different.

5. The switch of claim 1 wherein each of said first set of diodes and said second set of diodes comprises at least two diodes.

6. The switch of claim 1, wherein the first set of diodes is different in number from the second set of diodes. The switch according to claim 1, wherein said diodes are connected by a microstrip line. The switch according to claim 7, wherein said microstrip line length is less than 1/4 wavelength. The switch according to any one of claims 1-8, wherein the diode is a plastic PIN diode. The switch according to any one of claims 1 to 8, wherein an anode of a diode of said first group of diodes connected to said common terminal is connected to said common terminal, said said terminal being connected to said transmitting end a cathode of a diode of the first group of diodes is connected to the transmitting end, and an anode of a diode of the second group of diodes connected to the common terminal is connected to the common end, and the said terminal is connected to the receiving end A cathode of a diode in the second set of diodes is coupled to the receiving end.