A gallium arsenide radio frequency switch circuit

Abstract

This invention provides a gallium arsenide (GaAs) radio frequency (RF) switch circuit, including a first and a second voltage divider circuit. The first voltage divider circuit divides the input voltage VC1 into VC1a and VC1b. When VC1=0, VC1a=VC1b=0; when VC1≠0, VC1b=VC1. VC1a is regulated according to the input power at the common terminal. VC1b is connected to a corresponding transistor. VC1a is connected to a corresponding gate. The second voltage divider circuit divides the input voltage VC2 into VC2a and VC2b. When VC2=0, VC2a=VC2b=0; when VC2≠0, VC2b=VC2. VC2a is regulated according to the common maximum input power. VC2b is connected to a corresponding transistor. VC2a is connected to a corresponding transistor. This invention, while improving its safe operating range, can withstand greater process fluctuations and improve switch reliability.

Description

Technical Field

[0001] This invention belongs to the field of remote sensing integrated circuit technology, and particularly relates to a gallium arsenide radio frequency switch circuit. Background Technology

[0002] As a core control component in wireless communication systems, the power capacity of radio frequency (RF) switches directly determines the system's signal processing capability and reliability. With the evolution of 5G and future communication standards, the number of communication frequency bands has increased significantly, and modulation schemes have become increasingly complex (such as Orthogonal Frequency Division Multiple Access), generating signals with high peak-to-average power ratios (PAPR). This places extremely high demands on the power handling capability and linearity of RF switches. Especially in the miniaturization design of mobile terminals, the main antenna switch needs to support multi-band operation within a small size, requiring a power handling capability of +40 dBm (i.e., 10 watts) to ensure stable operation under harsh conditions such as circuit losses and antenna mismatch.

[0003] However, the power capacity of RF switches based on traditional gallium arsenide (GaAs) technology is often limited by process conditions. The main bottleneck lies in the breakdown voltage (BV) of GaAs devices, meaning the voltage difference between the drain and gate must be less than BV. To ensure that GaAs devices operate within a safe voltage range, the switch control voltage must be set very carefully. In practical applications, due to factors such as device parasitic effects and process condition fluctuations, it is necessary to avoid subjecting the switch to its maximum withstand voltage, and the turn-off voltage often needs to have a margin. This limitation restricts the performance of traditional RF switches in high-power applications, making it difficult to meet the ever-increasing demand for high performance. Summary of the Invention

[0004] Purpose of the invention: In order to solve the problems existing in the prior art, the present invention provides a gallium arsenide radio frequency switch circuit.

[0005] Technical Solution: This invention discloses a gallium arsenide (GaAs) radio frequency (RF) switch circuit, including a GaAs RF switch comprising a first to an eighth transistor; a second, a first, a fifth, and a sixth transistor connected in series, with the source of the second transistor connected to the RF1 RF terminal and the source of the sixth transistor connected to the RF2 RF terminal; the drains of the first and fifth transistors connected to a common terminal; a third and a fourth transistor connected in series and then grounded, with the drain of the third transistor connected to the RF1 RF terminal; a seventh and an eighth transistor connected in series and then grounded, with the drain of the seventh transistor connected to the RF2 RF terminal; the GaAs RF switch circuit also includes first and second voltage divider circuits.

[0006] The first voltage divider circuit divides the input voltage VC1 into VC1a and VC1b. When VC1=0, VC1a=VC1b=0; when VC1≠0, VC1b=VC1. VC1a is regulated according to the input power at the common terminal. VC1b is connected to the gates of the second and eighth transistors; VC1a is connected to the gates of the first and seventh transistors.

[0007] The second voltage divider circuit divides the input voltage VC2 into VC2a and VC2b. When VC2=0, VC2a=VC2b=0; when VC2≠0, VC2b=VC2. VC2a is regulated according to the common maximum input power. VC2b is connected to the gates of the sixth and fourth transistors; VC2a is connected to the gates of the fifth and third transistors.

[0008] Furthermore, the first voltage divider circuit and the second voltage divider circuit have the same structure, both including a first resistor and a voltage-controlled rheostat. The positive terminal of the input power supply serves as the first output terminal, with an output voltage of VC1b / VC2b. The positive terminal of the input power supply is connected to one end of the voltage-controlled rheostat, and the other end of the voltage-controlled rheostat serves as the second output terminal, with an output voltage of VC1a / VC2a.

[0009] Furthermore, it also includes a power detection circuit for detecting the input power at the common terminal, and the distance between the power detection circuit and the common terminal is less than a preset distance.

[0010] Furthermore, the power detection circuit includes a microstrip line, a diode, and an RC low-pass filter circuit connected in sequence. Radio frequency energy is conducted to the microstrip line through the main path via spatial coupling. The coupled energy is rectified by the diode and filtered by the RC low-pass filter to form a voltage Vdet. The voltage-controlled rheostat is controlled based on the voltage Vdet.

[0011] Beneficial effects: This invention provides different voltages to the switching transistors without changing the GaAs process and without altering the original circuit structure, improving the switch's voltage withstand capability and increasing its output power capability, enabling its application in higher power scenarios. Simultaneously, it expands its safe operating range, allowing it to withstand greater process fluctuations and improving switch reliability. Attached Figure Description

[0012] Figure 1 This is a circuit diagram of a traditional single-pole double-throw (SPDD) RF switch.

[0013] Figure 2 The circuit diagram shows the circuit after the turn-off voltage VC2 is divided into two groups.

[0014] Figure 3 This is a circuit diagram of the overall radio frequency switch structure of the present invention.

[0015] Figure 4Timing diagrams of the two control voltages VC1a and VC1b generated for this invention.

[0016] Figure 5 This is a power detection circuit. Detailed Implementation

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] A classic single-pole double-throw radio frequency switch structure is as follows: Figure 1 As shown. The RFC common port has RF1 and RF2 as radio frequency ports, and S1-S8 as switching transistors. S1, S2, S5, and S6 are series switches, while S3, S4, S7, and S8 are parallel switches. V1 and V2 are switch control signals; a high level indicates the switch is on, and a low level indicates the switch is off, with their high and low levels being inversely related.

[0019] When RF1 is on and RF2 is off, the RF signal is input from the common terminal RFC. VC1 controls S1 and S2 to open, and the signal is transmitted to RF1. VC2 controls S3 and S4 to close, preventing signal leakage to ground. On the other side, VC2 controls S5 and S6 to close, preventing signal leakage to RF2. VC1 controls S7 and S8 to open, further preventing signal leakage. As shown in the diagram, both the series and parallel transistors use a stacked configuration, a typical structure for improving isolation. In this structure, S3 and S5 are the turn-off transistors closest to the power transmission path, with the largest power and voltage difference on both sides of their switches. S4 and S6 are located behind S3 and S5, respectively, and their power is buffered, so the voltage they withstand is necessarily less than that of S3 and S5. S3 and S5 directly face the maximum voltage difference on the signal path, and their drain-source voltage stress is much greater than that of S4 / S6. Under prolonged high voltage stress, device aging is accelerated, increasing the risk of failures such as gate oxide breakdown and hot carrier injection, thus reducing switch lifespan and long-term reliability. High voltage stress brings the operating point of S3 / S5 closer to the device's nonlinear region, easily generating harmonic distortion and intermodulation products. This directly affects the linearity of the RF switch, posing a serious performance bottleneck for high-power, high-sensitivity communication systems. To withstand higher voltages, S3 and S5 typically require larger device sizes, leading to larger parasitic capacitances and reduced switch isolation and bandwidth.

[0020] Therefore, in this embodiment, it is conceived to divide the turn-off voltage VC2 into two groups: VC2a and VC2b. VC2a uses the recommended -5V voltage, and VC2b uses -8V voltage, thereby obtaining a better cutoff state and improving switching performance. Specifically, as follows... Figure 2As shown in the diagram. Although the above solution can improve switching performance, it increases the number of external control voltage interfaces from 2 to 4, which is not practical.

[0021] This invention provides a structural unit that can provide different control voltages without adding additional interfaces. For example... Figure 3 As shown, the external interface provides a control voltage VC1 / 0V. When 0V is provided, VC1a = VC1b = 0V, and the switching transistor is turned on. When VC1 is provided, VC1b = VC1, and the voltage-controlled rheostat R_Vdet and the resistor divide the voltage to generate VC1a. The resistance value of the voltage-controlled rheostat is determined by its voltage Vdet. Vdet comes from the input power of the RFC. When the input power is low, R_Vdet is small, VC1a is close to VC1b, providing a larger voltage (absolute value), allowing the switching transistor to be turned off more completely; when the input power is high, R_Vdet is large, VC1a is far from VC1b, providing a smaller voltage (absolute value). Figure 4 This invention provides two control voltages, VC1a and VC1b, generated according to the present invention. VC1a is applied to S1 and directly withstands the power from the RFC. Using a lower voltage for VC1a effectively prevents device breakdown. VC1b is applied to S2 and withstands even less power than S1, allowing for the use of a higher voltage to improve switch isolation. The greatest advantage of this invention is that it generates two different control voltages by coupling the power at the RFC terminal without introducing an additional control power supply. The VC1a voltage decreases as the power of the RFC increases, ensuring switch safety under high power conditions without excessively sacrificing switch isolation under low power conditions.

[0022] An external interface provides a control voltage VC2 / 0V. When 0V is provided, VC2a = VC2b = 0V, and the switching transistor is turned on. When VC2 is provided, VC2b = VC2, and the voltage-controlled rheostat R_Vdet and the resistor divide the voltage to generate VC2a. The resistance value of the rheostat is determined by its voltage Vdet. Vdet comes from the input power of the RFC. When the input power is low, R_Vdet is small, VC2a is close to VC2b, providing a larger voltage (absolute value), allowing the switching transistor to be turned off more completely; when the input power is high, R_Vdet is large, VC2a is far from VC2b, providing a smaller voltage (absolute value), allowing the switching transistor to withstand a smaller voltage, making the device safer.

[0023] The power detection circuit in this embodiment detects power through electromagnetic coupling. It outputs a voltage proportional to the detected power. The electromagnetic coupling effect near the RFC port is small and can be ignored. Figure 5The RFPath shown represents the power passing through the main path RFC. The RF coupler is a microstrip line very close to the main path, allowing RF energy to be conducted from the main path to the RF coupler via spatial coupling. The distance and length between the two determine the amount of coupled energy. Generally, a coupling coefficient of 20dB or higher is chosen, meaning the coupled energy is <1%, to reduce interference to the main path. The coupled energy, after diode rectification and RC low-pass filtering, forms a voltage Vdet. This voltage value is affected by the magnitude of the coupled energy and the filter coefficient, and is generally controlled within 0.5~3V. A traditional voltage-controlled variable resistor is then connected, using a PMOS (or other similar functional device) to increase the resistance as the control voltage increases. The adjustable resistance range is 10ohm~1Mohm. Resistors and capacitors are used to maintain circuit stability.

[0024] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A gallium arsenide (GaAs) radio frequency (RF) switch circuit, comprising a GaAs RF switch, wherein the GaAs RF switch comprises a first to an eighth transistor; a second, a third, a fifth, and a sixth transistor connected in series, wherein the source of the second transistor is connected to an RF1 RF terminal, the source of the sixth transistor is connected to an RF2 RF terminal, and the drains of the first and fifth transistors are connected to a common terminal; a third and a fourth transistor are connected in series and then grounded, the drain of the third transistor being connected to the RF1 RF terminal; a seventh and an eighth transistor are connected in series and then grounded, the drain of the seventh transistor being connected to the RF2 RF terminal; characterized in that, The gallium arsenide radio frequency switch circuit also includes a first and a second voltage divider circuit; The first voltage divider circuit divides the input voltage VC1 into VC1a and VC1b. When VC1=0, VC1a=VC1b=0; when VC1≠0, VC1b=VC1. VC1a is regulated according to the input power at the common terminal. VC1b is connected to the gates of the second and eighth transistors; VC1a is connected to the gates of the first and seventh transistors. The second voltage divider circuit divides the input voltage VC2 into VC2a and VC2b. When VC2=0, VC2a=VC2b=0; when VC2≠0, VC2b=VC2. VC2a is regulated according to the common maximum input power. VC2b is connected to the gates of the sixth and fourth transistors. VC2a connects to the gates of the fifth and third transistors.

2. The gallium arsenide radio frequency switch circuit according to claim 1, characterized in that, The first voltage divider circuit and the second voltage divider circuit have the same structure, both including a first resistor and a voltage-controlled rheostat. The positive terminal of the input power supply is used as the first output terminal, with an output voltage of VC1b / VC2b. The positive terminal of the input power supply is connected to one end of the voltage-controlled rheostat, and the other end of the voltage-controlled rheostat is used as the second output terminal, with an output voltage of VC1a / VC2a.

3. A gallium arsenide radio frequency switch circuit according to claim 2, characterized in that, It also includes a power detection circuit for detecting the input power at the common terminal. The distance between the power detection circuit and the common terminal is less than a preset distance.

4. A gallium arsenide radio frequency switch circuit according to claim 3, characterized in that, The power detection circuit includes a microstrip line, a diode, and an RC low-pass filter circuit connected in sequence. Radio frequency energy is conducted to the microstrip line through the main path via spatial coupling. The coupled energy is rectified by the diode and filtered by the RC low-pass filter to form a voltage Vdet. The voltage-controlled rheostat is controlled based on the voltage Vdet.

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