CN220173218U - Radio frequency switch circuit - Google Patents

Abstract

The utility model provides a radio frequency switch circuit, which is characterized by comprising: n series-stacked radio frequency switching unit circuits, where N is an integer greater than 1, a control circuit configured to provide control voltages to the radio frequency switching unit circuits to be in different operating states, wherein the radio frequency switching unit circuits include a first switching leg, a second switching leg, and a third switching leg connected in parallel, the first switching leg being configured as a primary radio frequency path, the second switching leg being configured as a forward withstand voltage compensation circuit, and the third switching leg being configured as a reverse withstand voltage compensation circuit.

Description

Radio frequency switch circuit

Technical Field

The present utility model relates to radio frequency integrated circuits, and more particularly to a radio frequency switching circuit.

Background

A radio frequency switching circuit is a circuit used in a wireless communication system that can switch signal transmission paths between multiple antennas and a single radio frequency receiver or transmitter. The radio frequency switching circuit is typically comprised of a radio frequency switching leg circuit and a switching control circuit. The radio frequency switch branch circuit can connect or isolate the input and output ports between different antennas, thereby controlling the path of the signal flow. The switch control circuit is used for controlling the working state of the radio frequency switch unit circuit so as to realize seamless switching between the antennas, thereby optimizing the performance of the wireless communication system. According to different application scenarios, the radio frequency switch circuit can be divided into a transmitting switch circuit, a receiving switch circuit, an antenna tuning switch circuit and the like.

The radio frequency switch circuit chip used in mobile terminals at present mainly uses a CMOS SOI (Silicon-On-Insulator) process, and is hereinafter called SOI radio frequency switch circuit. The SOI radio frequency switch circuit is a radio frequency switch circuit based on silicon-insulator-Silicon (SOI) technology, and has the characteristics of low insertion loss, high isolation, high switching speed and the like. The SOI radio frequency switch circuit is widely applied to antenna aperture tuning, and can realize multi-frequency band tuning and bandwidth enhancement of an antenna. The use of SOI radio frequency switching circuits in antenna aperture tuning is typically to incorporate tunable elements, such as tunable capacitors or inductors, into the antenna and then to control the switching states of these elements using the SOI radio frequency switching circuit. By varying the capacitance or inductance value of the tunable element, multi-band tuning and bandwidth enhancement of the antenna can be achieved. In particular, SOI radio frequency switching circuits are commonly used to implement single antenna multi-band tuning. In this case, a tunable capacitor or inductor is added to the antenna, and the capacitance or inductance value of the tunable element can be changed by controlling the switching state of the SOI radio frequency switching circuit, so as to realize multi-band tuning of the antenna. For example, in an LTE tri-band antenna system, the SOI radio frequency switching circuit may control three tunable elements to achieve tuning and bandwidth enhancement for the three bands of high, medium and low. In a word, the SOI radio frequency switch circuit has wide application in antenna aperture tuning, and can realize multi-frequency band tuning and bandwidth enhancement of the antenna.

The radio frequency antenna tuning switch circuit chip in the prior art is usually implemented by adopting a CMOS SOI process. The control mode of the switch is to use positive voltage and negative voltage control, namely when the switch is opened, the transistor gate electrode is controlled by the positive voltage, and when the switch is closed, the transistor gate electrode is controlled by the negative voltage. The main indexes of the radio frequency antenna switching circuit comprise indexes such as insertion loss, isolation, harmonic wave, power bearing capacity, voltage withstanding and the like. For the antenna tuning switch, because the antenna port is connected with the antenna tuning switch, strict requirements are provided for voltage withstanding indexes, voltage withstanding values are in different grades such as 45V, 60V and 80V according to different positions of the antenna tuning switch connected with the antenna, and in the actual product design, radio frequency switch chips in different models can be designed according to different voltage withstanding values. The single transistor breakdown voltage bv_fet of a CMOS SOI process is typically less than 3.5V. To be able to withstand the rf voltage swing at maximum transmit power, CMOS SOI antenna tuning switch circuits are typically designed in the form of a series stack of multiple transistors, as shown in fig. 1. Fig. 1 is a circuit schematic diagram showing an N-level stacked rf switching leg, where the withstand voltage value of the rf switching circuit depends on the voltage withstand capability of the off-state leg, and the power withstand capability of the off-state leg, that is, the withstand voltage capability, can be improved by increasing the number of stacked transistor stages of the off-state switching leg, and generally, the n=14 stacked cascade can withstand voltage 45V, the n=20 stacked cascade can withstand voltage 60V, and the n=26 stacked cascade can withstand voltage 80V.

Defining the breakdown voltage of a single transistor in the off state as VB_fet, n transistors are theoretically stacked in series, and the total breakdown voltage BV is shown in the following formula 1:

BV＝n×VB_fet (1)

in fact, the equivalent circuit of the switching branch in the off state is shown in fig. 2, due to the presence of parasitic capacitance of the transistor to ground. Fig. 2 is a schematic diagram showing an equivalent circuit of an N-stage series stacked radio frequency switch leg in an off-isolation state. The parasitic capacitance causes the voltage division of each stacked transistor to be uneven, the voltage drop of each transistor gradually decreases from the signal input terminal to the GND terminal, and the transistor sees the largest voltage drop at the signal input terminal, which limits the total breakdown voltage of the switching branches of the stacked transistors, and the total breakdown voltage BV of the n series-stacked transistors is shown in the following formula 2:

where Cds is the source-drain equivalent capacitance of the transistor, cgnd is the capacitance to ground of the transistor, and α is determined by equations 3 and 4 as follows:

fig. 3 is a graph showing the breakdown voltage BV versus the number of stacks according to equations 1 and 2. Referring to fig. 3, after the number of stacks reaches a certain number, the switching leg breakdown voltage BV does not continue to increase but is in a saturated state.

In order to solve the above problem, the capacitance value of Cds of each stage transistor is compensated, so that the equivalent Cds of each stage transistor are equal, and the voltage withstand value of the switch branch can be further improved. The above design ensures that the voltage swing of each transistor is uniform. For example, when the D terminal of fig. 1 is connected to the antenna signal terminal and the S terminal is GND, the transistor voltage swing VDS of each stage is uniform when seen from the D terminal to the S terminal in the off state by optimizing the size of each stage transistor such that the size of each stage transistor is gradually decreased from the D terminal to the S terminal. Fig. 4 is a schematic diagram showing the voltage swing VDS of each stage transistor after compensation of the capacitance value of the transistor Cds. As shown with reference to fig. 4, after compensation, the transistor voltage swing VDS of each stage is uniform.

According to the scheme, the radio frequency switch circuit with higher voltage withstand capability can be obtained by optimally designing the size of each stage of transistor. However, one disadvantage of the above solution is that Cds compensation can only be performed in one direction, if the S-terminal and the D-terminal are switched in directions, i.e. the S-terminal is connected to the antenna signal terminal and the D-terminal is connected to ground, the voltage swing VDS of the transistor of each stage will become non-uniform, the voltage swing of the transistor near the signal terminal is larger, and the signal swing of the transistor near the GND terminal is smaller. Fig. 5 is a schematic diagram of the voltage swing VDS of each stage transistor after the capacitance of the transistor Cds is compensated in reverse. Referring to fig. 5, the transistor voltage swing VDS of each stage becomes non-uniform. The breakdown voltage BV of the rf switching circuit thus designed reaches a certain value, which results in saturation of the region, i.e., the situation described in the above formula 2 and fig. 3 occurs.

The withstand voltage compensation scheme of the radio frequency switch circuit can only carry out unidirectional compensation. In fact, antenna tuning switches have a variety of applications. Taking a single pole four throw SP4T switch as an example, fig. 6 is a schematic diagram showing a first application scenario of the antenna tuning switch circuit. In the first application scenario, the port of the antenna ANT of the SP4T is connected to the antenna, and the voltage-withstanding compensation design of the radio frequency switch circuit is to compensate from the D-terminal to the S-terminal. Fig. 7 is a schematic diagram showing a second application scenario of the antenna tuning switch circuit. In the second application scenario, the port of the antenna ANT of the SP4T is grounded, and the voltage-withstanding compensation design of the radio frequency switch circuit is to compensate in the direction from the S terminal to the D terminal. Because of the different compensation directions, two types of chips, called SP4T and 4XSPST, respectively, will generally be required.

Disclosure of Invention

The utility model provides a radio frequency switch circuit, which can realize the voltage withstand compensation of the radio frequency switch branch in two directions, and the voltage withstand value of the radio frequency switch circuit is the same in the two application scenes of forward compensation and reverse compensation. The antenna tuning switch circuit applying the scheme of the utility model can be used as SP4T or 4XSPST, and can realize that a single product is adapted to scenes of various antenna tuning applications, thereby further optimizing BOM list and cost of a mobile terminal bill of materials.

An aspect of the present utility model proposes a radio frequency switching circuit comprising: n series-stacked radio frequency switching unit circuits, where N is an integer greater than 1, a control circuit configured to provide control voltages to the radio frequency switching unit circuits to be in different operating states, wherein the radio frequency switching unit circuits include a first switching leg, a second switching leg, and a third switching leg connected in parallel, the first switching leg being configured as a primary radio frequency path, the second switching leg being configured as a forward withstand voltage compensation circuit, and the third switching leg being configured as a reverse withstand voltage compensation circuit.

An aspect of the utility model proposes a radio frequency switching circuit, wherein the first switching branch comprises a first transistor configured with its gate connected to a first control port of the radio frequency switching unit circuit, its drain connected to a first output port of the radio frequency switching unit circuit, and its source connected to a second output port of the radio frequency switching unit circuit.

An aspect of the utility model proposes a radio frequency switching circuit, wherein the second switching branch comprises a first compensation transistor and a first switching transistor, the first compensation transistor being configured with its gate connected to the second control port of the radio frequency switching unit circuit, its drain connected to the first output port of the radio frequency switching unit circuit, and its source connected to the drain of the first switching transistor; the first switching transistor is configured with its gate connected to the third control port of the radio frequency switching unit circuit and its source connected to the second output port of the radio frequency switching unit circuit.

An aspect of the utility model proposes a radio frequency switching circuit, wherein the size of the first compensation transistor is configured to be larger than the size of the first switching transistor.

An aspect of the utility model proposes a radio frequency switching circuit, wherein the third switching branch comprises a second compensation transistor and a second switching transistor, the second compensation transistor being configured with its gate connected to the fourth control port of the radio frequency switching unit circuit, its drain connected to the first output port of the radio frequency switching unit circuit, and its source connected to the drain of the second switching transistor; the second switching transistor is configured with its gate connected to the fifth control port of the radio frequency switching unit circuit and its source connected to the second output port of the radio frequency switching unit circuit.

An aspect of the utility model proposes a radio frequency switching circuit, wherein the size of the second compensation transistor is configured to be larger than the size of the second switching transistor.

An aspect of the utility model proposes a radio frequency switch circuit, wherein the control circuit is configured to control the radio frequency switch unit control circuit to be in a conducting state, a first isolation state or a second isolation state.

An aspect of the present utility model proposes a radio frequency switching circuit, wherein, in a conducting state, the control circuit provides a conducting voltage to a first transistor of a first switching branch; providing a turn-on voltage to the first compensation transistor and the first switching transistor of the second switching branch; and providing an on-voltage to the second compensation transistor and the second switching transistor of the third switching branch.

An aspect of the present utility model proposes a radio frequency switching circuit, wherein, in a first isolation state, the control circuit provides an off-voltage to a first transistor of a first switching branch; providing an off-voltage to a first compensation transistor of the second switching branch and an on-voltage to the first switching transistor; and providing an on voltage to the second compensation transistor of the third switching branch and an off voltage to the second switching transistor.

An aspect of the present utility model proposes a radio frequency switching circuit, wherein, in a second isolation state, the control circuit provides an off-voltage to a first transistor of a first switching branch; providing an on voltage to a first compensation transistor of the second switching branch and an off voltage to the first switching transistor; and providing an off voltage to the second compensation transistor of the third switching branch and an on voltage to the second switching transistor.

Drawings

FIG. 1 is a circuit schematic diagram showing an N-level stacked radio frequency switching leg;

FIG. 2 is a schematic diagram showing an equivalent circuit of N stages of serially stacked RF switch legs in an off isolation state;

FIG. 3 is a graph showing the breakdown voltage BV versus the number of stacks according to equations 1 and 2;

FIG. 4 is a schematic diagram showing the voltage swing VDS of each stage transistor after compensation of the capacitance of the transistor Cds;

FIG. 5 is a schematic diagram of the voltage swing VDS of each stage transistor after the capacitance of the transistor Cds is compensated in reverse;

fig. 6 is a schematic diagram showing a first application scenario of an antenna tuning switch circuit;

fig. 7 is a schematic diagram showing a second application scenario of the antenna tuning switch circuit;

FIG. 8 is a schematic diagram illustrating a radio frequency switching circuit according to an embodiment of the present utility model;

FIG. 9 is a schematic diagram of a standard transistor switch cell circuit designed using a CMOS SOI process in accordance with an embodiment of the present utility model;

fig. 10 is a schematic diagram showing an equivalent circuit of the on state of the transistor switching unit circuit;

fig. 11 is a schematic diagram showing an equivalent circuit of an off state of a transistor switching unit circuit;

fig. 12 is a schematic diagram showing an equivalent circuit diagram of a radio frequency switch cell circuit in an isolated state 1 according to an embodiment of the present utility model;

FIG. 13 is a schematic diagram of an application scenario of a RF switch circuit according to an embodiment of the present utility model;

fig. 14 is a schematic diagram showing an equivalent circuit of forward withstand voltage compensation of a 2-stage stacked radio frequency switching circuit according to an embodiment of the present utility model;

fig. 15 is a schematic diagram showing an equivalent circuit of reverse withstand voltage compensation of a 2-stage stacked radio frequency switching circuit according to an embodiment of the present utility model;

fig. 16 is a schematic diagram showing the structure of a radio frequency switching circuit according to an embodiment of the present utility model; and

fig. 17 is a schematic diagram illustrating a radio frequency switching system according to an embodiment of the present utility model.

Detailed Description

Before proceeding with the following detailed description, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The terms "coupled," "connected," and derivatives thereof, refer to any direct or indirect communication or connection between two or more elements, whether or not those elements are in physical contact with one another. The terms "transmit," "receive," and "communicate," and derivatives thereof, encompass both direct and indirect communication. The terms "include" and "comprise," as well as derivatives thereof, mean inclusion without limitation. The term "or" is inclusive, meaning and/or. The phrase "associated with … …" and its derivatives are intended to include, be included in, interconnect with, contain within … …, connect or connect with … …, couple or couple with … …, communicate with … …, mate, interleave, juxtapose, approximate, bind or bind with … …, have attributes, have relationships or have relationships with … …, etc. The term "controller" refers to any device, system, or portion thereof that controls at least one operation. Such a controller may be implemented in hardware, or a combination of hardware and software and/or firmware. The functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. The phrase "at least one," when used with a list of items, means that different combinations of one or more of the listed items may be used, and that only one item in the list may be required. For example, "at least one of A, B, C" includes any one of the following combinations: A. b, C, A and B, A and C, B and C, A and B and C.

Definitions for other specific words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior as well as future uses of such defined words and phrases.

In this patent document, the application combinations of modules and the division levels of sub-modules are for illustration only, and the application combinations of modules and the division levels of sub-modules may have different manners without departing from the scope of the disclosure.

Fig. 8 is a schematic diagram illustrating a radio frequency switching circuit according to an embodiment of the present utility model.

Referring to fig. 8, the present utility model provides a radio frequency switching circuit formed by stacking N stages of radio frequency switching unit circuits in series, where N is an integer greater than 1. The radio frequency switch unit circuit comprises a first switch branch, a second switch branch and a third switch branch, and the three switch branches are connected in parallel. The first switch branch is formed by a transistor M1, a drain terminal of the transistor M1 is connected to the port P1, a source terminal of the transistor M1 is connected to the port P2, and a gate of the transistor M1 is connected to the port G1. The second switch branch is formed by a transistor M2A, M B, the drain terminal of the transistor M2A is connected to the port P1, the source terminal of the transistor M2A is connected to the drain terminal of the transistor M2B, the source terminal of the transistor M2B is connected to the port P2, the gate terminal of the transistor M2A is connected to the port G2A, and the gate terminal of the transistor M2B is connected to the port G2B. The third switch branch is formed by a transistor M3A, M B, the drain terminal of the transistor M3A is connected to the port P1, the source terminal of the transistor M3A is connected to the drain terminal of the transistor M3B, the source terminal of the transistor M3B is connected to the port P2, the gate terminal of the transistor M3A is connected to the port G3A, and the gate terminal of the transistor M3B is connected to the port G2B. The first switch branch is a main radio frequency path, and the size of the transistor M1 is determined according to practical application scenarios. When forward is defined as from the P1 end to the P2 end, the RF signal is seen from the P1 end, and the P2 end is grounded. When the reverse direction is defined from the P2 end to the P1 end, the radio frequency signal is seen from the P2 end, and the P1 end is grounded. The second switching branch serves as a forward withstand voltage compensation circuit, i.e. the radio frequency swing of the antenna signal is seen from the drain of M1, M2A is a compensation transistor of smaller size relative to M1, and transistor M2B serves to control the second branch to be turned on and off of smaller size relative to M2A. The third switching leg acts as a reverse withstand voltage compensation circuit, i.e. the radio frequency swing of the antenna signal seen from the source of M1, M3A is a compensation transistor of smaller size relative to M1, and transistor M3B acts to control the third leg to turn on and off of smaller size relative to M3A. By connecting the above-mentioned radio frequency switch units in series, an N-stage stacked structure is formed, where N is an integer greater than 1, as shown in fig. 16. Fig. 16 is a schematic diagram showing the structure of a radio frequency switching circuit according to an embodiment of the present utility model. By configuring different grid control voltages, the radio frequency switch circuit can realize bidirectional withstand voltage compensation of radio frequency switch branches, so that voltage swing of transistors stacked at each stage is uniform in forward application and reverse application, and the total breakdown voltage value of the radio frequency switch circuit is improved.

Fig. 9 is a schematic diagram of a standard transistor switch cell circuit designed using a CMOS SOI process in accordance with an embodiment of the present utility model.

Referring to fig. 9, the transistor switching unit circuit includes: there is a four port NMOS transistor, a transistor Gate (Gate) series resistor Rg, a series resistor Rds between the Source and Drain terminals of the transistor (Drain Source), and a Body terminal of the transistor (Body) series resistor Rb. The transistor switch unit circuit has 4 ports, namely a G terminal, a D terminal, a B terminal and an S terminal. By applying different control voltages to the G-terminal and the B-terminal, the operating state of the transistor switching unit can be controlled. When the transistor switching unit is in an on state, for example, a voltage of 2.5V (on voltage) may be applied to the G terminal, and a voltage of 0V may be applied to the B terminal. A simplified equivalent circuit of the transistor switch unit in the on state is shown in fig. 10, which has an on-state resistance Ron equivalent to the total resistance of the sum of the resistances between the D terminal and the S terminal. It will be appreciated that the parasitic capacitance and parasitic inductance of the on-state of the transistor switch cell are associated with existing switch cell circuits, however, they are not shown in fig. 10 because the parasitic capacitance and parasitic inductance of the on-state are relatively small. When the transistor switching unit is in an off state, for example, a voltage of-2.5V (off voltage) may be applied to the G terminal, and a voltage of-2.5V may be applied to the B terminal. A simplified equivalent circuit of the transistor switching unit in the off state is shown in fig. 11, which has a capacitance Coff in the off state. It will be appreciated that other parasitic capacitances and parasitic inductances of the transistor switch cell off-state are associated with existing switch cell circuits, however, they are not shown in fig. 11 because they are relatively small.

Table 1 shows control logic of a radio frequency switching unit circuit according to an embodiment of the present utility model. Referring to table 1, the radio frequency switch unit circuit has three operating states: on state, isolated state 1 and isolated state 2. Although examples of the control voltages 2.5V (on voltage) and-2.5V (off voltage) are shown in table 1, it should be understood by those skilled in the art that the present utility model is not limited to the above examples. Other control voltage values, such as 2V and-2V, may be used depending on the application, and modifications and adjustments to the control voltage are also within the scope of the present utility model.

In table 1, the control voltage of the Body terminal (Body) of the switching unit is not listed, and it will be understood by those skilled in the art that the control of the Body terminal may be configured to vary with the gate control voltage, for example, when the transistor gate control voltage is 2.5V, the control voltage of the Body terminal thereof is 0V; when the transistor gate control voltage is-2.5V, the control voltage at its body is-2.5V. According to an embodiment of the present utility model, the control voltages defined in table 1 may be implemented by an additional logic control circuit, which is not limited by the present utility model.

TABLE 1

Referring to table 1, the isolation state 1 is defined as a forward withstand voltage compensation state, i.e., a radio frequency swing of the antenna signal is seen from the drain (P1 port) of the transistor M1 of fig. 8. According to the transistor operation states defined in table 1, in the isolation state 1, the equivalent circuit diagram of the radio frequency switch unit circuit of fig. 8 is shown in fig. 12 (a). The transistor M1 is equivalent to a capacitor C1, the transistor M2A is equivalent to a capacitor C2A, the transistor M2B is equivalent to a resistor R2B, the transistor M3A is equivalent to a resistor R3A, and the transistor M3B is equivalent to a capacitor C3B. It will be appreciated by those skilled in the art that other parasitic capacitances and parasitic inductances of the transistor switch cells of the isolation state 1 are associated with existing switch cell circuits, however, because the other parasitic capacitances and parasitic inductances of the off state are relatively small, they are not shown in fig. 12. According to the principle of equivalent exchange of series-parallel impedance, the series connection relation of C2A, R B can be converted into the parallel connection relation of C2A and R2B_P. Similarly, the series connection relationship of C3B, R a can be converted into a parallel connection relationship of C3B and r3a_p, as shown in (B) of fig. 12.

In the following, a 65nm cmos SOI process is taken as an example, and it is assumed that the dimension of M1 is 5mm, the dimension of M2a is 2mm, and the dimensions of M2B and M3A, M B are 100um, and those skilled in the art will understand that the above values may be changed correspondingly according to the process, and the comparison of the present utility model is not limited. According to the definition above, c1=0.8 pF, c2a=0.33 pF, c3b=0.017 pF, r2b=5Ω and r3a=5Ω. At frequency=1 GHz, the Q2 value of the series RC network consisting of C2A and R2B is 96.6 and the Q3 value of the series RC network consisting of C3B and R3A is 2000. The Q value is much higher than 10. The following equations 5 and 6 can be derived from the principle of equivalent interchange of series-parallel impedances:

R2B _P ≈Q2 ² ×R2B＝46kΩ (5)

R3A _P ≈Q2 ² ×R2B＝20MΩ (6)

by combining the capacitor and the resistor of the equivalent circuit (b) of fig. 12, the equivalent circuit diagram of which is shown in (C) of fig. 12, in which c4=0.347pf and r4=46 kΩ, it can be seen that in the isolated state 1, the equivalent capacitance and resistance value of the radio frequency switch unit circuit can be adjusted by adjusting the transistor M2A.

Fig. 13 is a schematic diagram of an application scenario of a radio frequency switch circuit according to an embodiment of the present utility model. Referring to fig. 13, it is assumed that the signal source has a 50Ω load, which is also a 50Ω system, and the radio frequency signal is signal-transmitted in a 50Ω radio frequency transmission line system. When the radio frequency switch unit circuit is in the isolation state 1, the radio frequency system is a 50Ω transmission line system, the calculated resistance R4 impedance value is far greater than 50Ω, and R4 is high-resistance for the 50Ω radio frequency transmission line system, so that the radio frequency switch unit circuit does not affect the transmission signal. Resistor R4 may further be eliminated to simplify the equivalent circuit structure. The equivalent circuit of the radio frequency switch unit circuit in the isolation state 1 is that the capacitors C1 and C4 are connected in parallel. The radio frequency switch unit circuits are stacked in series to realize higher withstand voltage.

Fig. 14 is a schematic diagram showing an equivalent circuit of forward withstand voltage compensation of a 2-stage stacked radio frequency switching circuit according to an embodiment of the present utility model. It will be appreciated by those skilled in the art that fig. 14 illustrates a 2-level stack as an example, however, the present utility model is not limited to a 2-level stack and may be extended to an N-level stack where N is a natural number greater than 1.

Referring to fig. 14, each stage of the radio frequency switching unit circuit is in an isolated state 1, and includes two capacitors c1_x and c4_x, where x is a stage number, c1_x is an off equivalent capacitor of the first switching leg transistor M1, and c4_x is an equivalent capacitor of the second switching leg and the third switching leg in the isolated state 1. The value of m2a_x can be adjusted through simulation design, and the value of c4_x, that is, the values of c4_1 and c4_2 in fig. 14, can be further adjusted, so that the forward uniform voltage-withstanding compensation of the two-stage stacked radio frequency switch unit circuit is further realized.

The reverse withstand voltage compensation state in the isolation state 2 can be analyzed with reference to the above analysis. Fig. 15 is a schematic diagram showing an equivalent circuit of reverse withstand voltage compensation of a 2-stage stacked radio frequency switching circuit according to an embodiment of the present utility model. It will be appreciated by those skilled in the art that fig. 15 illustrates a 2-level stack, however, the utility model is not limited to a 2-level stack, and may be extended to an N-level stack, where N is a natural number greater than 1.

Referring to FIG. 15, consider a 65nm CMOS SOI process as an example, where M1 has a dimension of 5mm, M3A has a dimension of 2mm, and M2A and M2B, M B have dimensions of 100um. Each stage of the radio frequency switching unit circuit is in an isolated state 2 and comprises two capacitors c1_x and c5_x, wherein x is a stage number, c1_x is an off equivalent capacitor of the first switching leg transistor M1, and c5_x is an equivalent capacitor of the second switching leg and the third switching leg in the isolated state 2. The value of m3a_x can be adjusted through simulation design, and the value of c5_x, that is, the values of c5_1 and c5_2 in fig. 15, can be further adjusted, so that the reverse uniform withstand voltage compensation of the two-stage stacked radio frequency switch unit circuit is further realized.

C4_x and c5_x are capacitors with different capacitance values, and the capacitance value of each stage can be achieved by optimizing the values of transistors m2a_x and m3a_x through a simulation design. The radio frequency switch circuit can compensate a positive withstand voltage value in an isolation state 1 and can compensate a negative withstand voltage value in an isolation state 2.

The control manner related to the above utility model may be implemented by an additional logic control circuit, for example, by a switch controller, which is not limited in this regard and will not be described herein.

According to an embodiment of the present utility model, an N-level stacked radio frequency switching circuit may be provided. According to the radio frequency switch circuit provided by the embodiment of the utility model, the radio frequency switch branch can be subjected to bidirectional withstand voltage compensation, and the voltage division value of each stage can be uniform, so that the total breakdown voltage value of the radio frequency switch circuit is improved. The radio frequency switch circuit provided by the embodiment of the utility model can be applied to voltage-resistant antenna tuning switch products such as 45V/60V/80V and the like.

Fig. 17 is a schematic diagram illustrating a radio frequency switching system according to an embodiment of the present utility model. Referring to fig. 17, the radio frequency switching system includes a switch controller 1701 and a radio frequency switching circuit 1702. Wherein the rf switch circuit 1702 comprises the N-stage rf switch cell circuit described above stacked in series, wherein N is an integer greater than 1, and wherein the switch controller 1701 is configured to provide a control voltage to the transistors in the rf switch cell circuit to control the rf switch cell circuit to operate in the on state, the off state 1, or the off state 2.

Although the present disclosure has been described with exemplary embodiments, various changes and modifications may be suggested to one skilled in the art. The disclosure is intended to embrace such alterations and modifications that fall within the scope of the appended claims.

Any description of the present utility model should not be construed as implying that any particular element, step, or function is a necessary element to be included in the scope of the claims. The scope of patented subject matter is defined only by the claims.

Claims (10)

1. A radio frequency switching circuit, comprising:

n series-stacked RF switch unit circuits, N being an integer greater than 1,

a control circuit configured to provide a control voltage to the radio frequency switch unit circuit to cause it to be in different operating states,

the radio frequency switching unit circuit includes a first switching leg, a second switching leg, and a third switching leg connected in parallel, the first switching leg being configured as a main radio frequency path, the second switching leg being configured as a forward withstand voltage compensation circuit, and the third switching leg being configured as a reverse withstand voltage compensation circuit.

2. The radio frequency switching circuit of claim 1, wherein the first switching leg comprises a first transistor configured with its gate connected to a first control port of the radio frequency switching unit circuit, its drain connected to a first output port of the radio frequency switching unit circuit, and its source connected to a second output port of the radio frequency switching unit circuit.

3. The radio frequency switching circuit according to claim 1, wherein the second switching leg comprises a first compensation transistor and a first switching transistor,

the first compensation transistor is configured with its gate connected to the second control port of the radio frequency switch unit circuit, its drain connected to the first output port of the radio frequency switch unit circuit, and its source connected to the drain of the first switch transistor;

the first switching transistor is configured with its gate connected to the third control port of the radio frequency switching unit circuit and its source connected to the second output port of the radio frequency switching unit circuit.

4. The radio frequency switching circuit of claim 3, wherein the size of the first compensation transistor is configured to be larger than the size of the first switching transistor.

5. The radio frequency switching circuit according to claim 1, wherein the third switching leg comprises a second compensation transistor and a second switching transistor,

the second compensation transistor is configured with its gate connected to the fourth control port of the radio frequency switch unit circuit, its drain connected to the first output port of the radio frequency switch unit circuit, and its source connected to the drain of the second switch transistor;

the second switching transistor is configured with its gate connected to the fifth control port of the radio frequency switching unit circuit and its source connected to the second output port of the radio frequency switching unit circuit.

6. The radio frequency switching circuit of claim 5, wherein the size of the second compensation transistor is configured to be larger than the size of the second switching transistor.

7. The radio frequency switching circuit of claim 1, wherein the control circuit is configured to control the radio frequency switching unit circuit to be in a conductive state, a first isolated state, or a second isolated state.

8. The radio frequency switching circuit of claim 7, wherein in the on state, the control circuit provides an on voltage to the first transistor of the first switching leg; providing a turn-on voltage to the first compensation transistor and the first switching transistor of the second switching branch; and providing an on-voltage to the second compensation transistor and the second switching transistor of the third switching branch.

9. The radio frequency switching circuit of claim 7, wherein in the first isolation state, the control circuit provides an off voltage to the first transistor of the first switching leg; providing an off-voltage to a first compensation transistor of the second switching branch and an on-voltage to the first switching transistor; and providing an on voltage to the second compensation transistor of the third switching branch and an off voltage to the second switching transistor.

10. The radio frequency switching circuit of claim 7, wherein in the second isolation state, the control circuit provides an off voltage to the first transistor of the first switching leg; providing an on voltage to a first compensation transistor of the second switching branch and an off voltage to the first switching transistor; and providing an off voltage to the second compensation transistor of the third switching branch and an on voltage to the second switching transistor.