Transmitting end antenna switch based on three-coil transformer
By using a transmitting antenna switch based on a three-coil transformer in the RF communication system, and using the third coil controlled by the switch to adjust the impedance in different modes, the traditional switching area is solved, and the traditional switching area is achieved, and the good switching effect of low loss and high impedance is achieved, and the chip area is reduced.
Patent Information
- Application Number
- CN202510214549.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-26
- Publication Date
- 2025-05-09
AI Technical Summary
In the existing RF communication systems, traditional transmitter antenna switches occupy a large chip area, have high losses and low closing impedance, resulting in large leakage loss and deterioration of noise coefficient in the reception mode.
Using a transmitting end antenna switch based on a three-coil transformer, the third coil controlled by the switch is introduced, and the loss is cut off in the transmit mode, the closing impedance is increased in the reception mode, and the chip area is reduced by the laminated structure.
Low loss in transmit mode and high shutdown impedance in receive mode are achieved, reducing leakage loss of received signals, improving the noise performance of the system, and significantly reducing the chip area.
Smart Images
Figure CN119966439A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of radio frequency communication integrated circuits, and in particular to a transmitting end antenna switch based on a three-coil transformer. Background Art
[0002] In radio frequency transceiver systems, time division multiplexing systems are widely used, and time division multiplexing systems require single-pole double-throw switches to switch the state of transmission and reception. Traditional transmit switches usually cascade a discrete single-pole double-throw switch at the output end of the power amplifier, but this type of switch often occupies a large chip area and has large losses. Therefore, the transmit switch at the antenna port has always been a difficult point in system design. In recent designs, in order to avoid this problem, the switch at the output end of the power amplifier is often removed. However, as the frequency increases, the parasitic effects of the power amplifier become increasingly obvious. If the output switch of the power amplifier is removed, the off impedance of the power amplifier will be extremely low, resulting in a large leakage loss in the receiving mode, which deteriorates the noise figure of the low-noise amplifier. Therefore, this patent proposes a transmit switch based on a three-coil transformer to solve the above problems. Summary of the invention
[0003] Technical problem: The purpose of the present invention is to provide a transmitting antenna switch based on a three-coil transformer. In view of the problems of large area, high loss and low closed impedance of the current antenna switch, a transmitting antenna switch with compact area, low loss and high closed impedance is proposed to ensure low loss in the transmitting mode and high impedance in the receiving mode, thereby achieving a good transmitting and receiving switching effect.
[0004] Technical solution: A transmitting antenna switch based on a three-coil transformer of the present invention includes a primary coil of a transformer, a secondary coil of a transformer, a coupling coil, an RF power amplifier, and an RF switch; wherein, two ends of the primary coil of the transformer are connected to the output end of the RF power amplifier, two ends of the secondary coil of the transformer are respectively connected to the antenna and the ground, two ends of the coupling coil are connected to two ends of the RF switch, and the coupling coil is coupled with the primary coil of the transformer and the secondary coil of the transformer at the same time to form a complete transmitting antenna switch.
[0005] The primary coil of the transformer, the secondary coil of the transformer and the coupling coil are stacked structures, the primary coil of the transformer is located in the middle layer, the secondary coil of the transformer is located in the upper layer, and the coupling coil is located in the bottom layer. This stacked structure greatly reduces the area of the traditional antenna switch.
[0006] The coupling coefficient between the primary coil of the transformer and the secondary coil of the transformer is k12, the coupling coefficient between the primary coil of the transformer and the coupling coil is k13, and the coupling coefficient between the secondary coil of the transformer and the coupling coil is k23.
[0007] The primary coil of the transformer and the secondary coil of the transformer and the coupling coefficient k12 constitute an output matching network of the radio frequency power amplifier.
[0008] The coupling coil is turned on and off by a radio frequency switch; in the transmission mode, the radio frequency switch does not affect the working state of the power amplifier PA.
[0009] In the transmitting mode, the RF switch is disconnected, the coupling coil is open-circuited, the coupling between the coupling coil and the primary coil of the transformer has little effect on the primary coil of the transformer, and the coupling between the coupling coil and the secondary coil of the transformer has little effect on the secondary coil of the transformer.
[0010] In the receiving mode, the RF switch is turned on, the RF power amplifier is turned off, and the coupling coil is short-circuited. The coupling coil affects the inductance of the primary coil of the transformer through the coupling coefficient k13, and the coupling coil affects the inductance of the secondary coil of the transformer through the coupling coefficient k23; the closing impedance of the RF power amplifier is increased and the leakage of the received signal is reduced.
[0011] In the receiving mode, the off impedance of the RF power amplifier is increased to γ times of the original value.
[0012]
[0013] The RF switch is implemented by a transistor M1. The on and off of the RF switch (SW) is realized by a control signal B1 connected to the gate of the transistor M1 through a large resistor R1. When the control signal B1 is at a high level, the transistor M1 is turned on, and when the control signal B1 is at a low level, the transistor M1 is turned off.
[0014] In the transmitting mode, the control signal B1 is set to a low level 0, and the control signal is transmitted to the gate of the transistor M1 through the large resistor R1. At this time, the transistor M1 is disconnected and the coupling coil is open.
[0015] The radio frequency transmitting circuit includes at least one transmitting end antenna switch based on a three-coil transformer.
[0016] Beneficial effects: The purpose of the present invention is to provide a transmitting antenna switch based on a three-coil transformer. A third coil controlled by a switch is introduced on the basis of a traditional two-coil transformer. The switch is disconnected in the transmitting mode, which reduces the influence of the third coil on the two-coil transformer and reduces the loss. When the switch is turned on in the receiving mode, the impedance conversion ratio of the two coils can be adjusted, reducing the leakage of the received signal. At the same time, the present invention adopts a stacked transformer structure in the layout, which reduces the chip area and has a high engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 A transmitting end antenna switch based on a three-coil transformer of the present invention;
[0018] Figure 2 It is a schematic diagram of the circuit structure of the radio frequency switch SW;
[0019] Figure 3 is an equivalent circuit diagram of the present invention in the transmission mode;
[0020] Figure 4 is the equivalent circuit diagram of the switchless structure in the receiving mode;
[0021] Figure 5 is an equivalent circuit diagram of the present invention in a receiving mode;
[0022] Figure 6 This is a specific implementation layout structure of the present invention.
[0023] The figure includes: the primary coil L1 of the transformer, the secondary coil L2 of the transformer, the coupling coil L3, the RF power amplifier PA, the RF switch SW, the antenna ANT, the control signal B1, the large resistor R1, and the transistor M1. DETAILED DESCRIPTION
[0024] In order to better understand the purpose, structure and function of the present invention, the transmitting end antenna switch based on the three-coil transformer of the present invention is further described in detail below in conjunction with the accompanying drawings. The embodiments of the switch adjustable capacitor of the present invention shown in the accompanying drawings and described according to the accompanying drawings are only exemplary, and the present invention is not limited to these embodiments.
[0025] like Figure 1 As shown, the transmitting antenna switch based on the three-coil transformer of the present invention includes a primary coil L1 of the transformer, a secondary coil L2 of the transformer, a coupling coil L3 coupled with the primary coil L1 of the transformer and the secondary coil L2 of the transformer, an RF power amplifier PA, and an RF switch SW; wherein, two ends of the primary coil L1 of the transformer are connected to the output end of the RF power amplifier PA, two ends of the secondary coil L2 of the transformer are respectively connected to the antenna ANT and the ground, two ends of the coupling coil L3 are connected to two ends of the RF switch SW, and the coupling coil L3 is coupled with the primary coil L1 of the transformer and the secondary coil L2 of the transformer at the same time to form a complete transmitting antenna switch. The coupling coefficient between the primary coil L1 of the transformer and the secondary coil L2 of the transformer is k12, the coupling coefficient between the primary coil L1 of the transformer and the coupling coil L3 is k13, the coupling coefficient between the secondary coil L2 of the transformer and the coupling coil L3 is k23, both ends of the primary coil L1 of the transformer are connected to the output end of the RF power amplifier PA, both ends of the coupling coil L3 are connected to the RF switch SW, one end of the secondary coil L2 of the transformer is connected to the ground, and the other end is connected to the antenna ANT;
[0026] like Figure 2 As shown, the RF switch SW is implemented by a transistor M1, and the on and off of the switch is realized by the control signal B1 connected to the gate of the transistor M1 through a large resistor R1. When the control signal B1 is at a high level, the transistor M1 is turned on, and when the control signal B1 is at a low level, the transistor M1 is turned off.
[0027] like Figure 3 As shown, in the transmission mode, the control signal B1 is set to a low level 0, and the control signal is transmitted to the gate of the transistor M1 through the large resistor R1, so the transistor M1 is disconnected, the coupling coil L3 is open, and the coupling coil L3 has little effect on the primary coil L1 of the transformer, and the coupling coil L3 has little effect on the secondary coil L2 of the transformer. The primary coil L1 of the transformer and the secondary coil L2 of the transformer and the coupling coefficient k12 complete the output matching of the RF power amplifier PA, and the transistor M1 only introduces very low loss.
[0028] like Figure 4 As shown, in the receiving mode, if a switchless structure is adopted, that is, the third coil switch is not introduced, when the power amplifier is turned off, its off impedance Roff is low, which will introduce serious leakage loss.
[0029] like Figure 5 As shown, in the receiving mode, the control signal B1 is set to a high level 1, and the control signal is transmitted to the gate of the transistor M1 through the large resistor R1, so the transistor M1 is turned on, the coupling coil L3 is short-circuited, and the power amplifier is turned off. The coupling coil L3 affects the primary coil L1 of the transformer through the coupling coefficient k13, and the coupling coil L3 affects the secondary coil L2 of the transformer through the coupling coefficient k23, thereby increasing the off impedance Roff of the RF power amplifier PA to Figure 4 The received signal leakage is reduced by γ times of Roff. γ is calculated as:
[0030] like Figure 6 As shown, in the specific implementation diagram, the primary coil L1 of the transformer, the secondary coil L2 of the transformer, and the coupling coil L3 are a stacked structure, the primary coil L1 of the transformer is located in the middle layer, the secondary coil L2 of the transformer is located in the upper layer, and the coupling coil L3 is located in the bottom layer. This stacked structure greatly reduces the area of the traditional antenna switch.
[0031] Through the above description, it can be further determined that the advantages of the present invention are: 1) in the transmitting mode, the switch only introduces very low loss; 2) in the receiving mode, the switch can increase the off impedance of the power amplifier and reduce the leakage of the received signal; 3) the three-coil transformer switch adopts a stacked structure, which reduces the area of the traditional switch.
Claims
1. A transmitting end antenna switch based on a three-coil transformer, characterized in that: The transmitting switch based on the three-coil transformer comprises a primary coil (L1) of the transformer, a secondary coil (L2) of the transformer, a coupling coil (L3), a radio frequency power amplifier (PA), and a radio frequency switch (SW); wherein two ends of the primary coil (L1) of the transformer are connected to the output end of the radio frequency power amplifier (PA), two ends of the secondary coil (L2) of the transformer are respectively connected to an antenna (ANT) and a ground, two ends of the coupling coil (L3) are connected to two ends of the radio frequency switch (SW), and the coupling coil (L3) is coupled with the primary coil (L1) of the transformer and the secondary coil (L2) of the transformer at the same time to form a complete transmitting end antenna switch.
2. The transmitting end antenna switch based on a three-coil transformer according to claim 1, characterized in that: The primary coil (L1) of the transformer, the secondary coil (L2) of the transformer, and the coupling coil (L3) are a stacked structure, wherein the primary coil (L1) of the transformer is located in the middle layer, the secondary coil (L2) of the transformer is located in the upper layer, and the coupling coil (L3) is located in the bottom layer. This stacked structure greatly reduces the area of a traditional antenna switch.
3. A transmitting end antenna switch based on a three-coil transformer according to claim 1 or 2, characterized in that: The coupling coefficient between the primary coil (L1) of the transformer and the secondary coil (L2) of the transformer is k12, the coupling coefficient between the primary coil (L1) of the transformer and the coupling coil (L3) is k13, and the coupling coefficient between the secondary coil (L2) of the transformer and the coupling coil (L3) is k23.
4. The transmitting end antenna switch based on a three-coil transformer according to claim 3, characterized in that: The primary coil (L1) of the transformer and the secondary coil (L2) of the transformer and a coupling coefficient of k12 form an output matching network of a radio frequency power amplifier (PA).
5. The transmitting end antenna switch based on a three-coil transformer according to claim 3, characterized in that: The coupling coil (L3) is turned on and off by a radio frequency switch (SW); in a transmission mode, the radio frequency switch (SW) does not affect the working state of a power amplifier PA.
6. The transmitting end antenna switch based on a three-coil transformer according to claim 3, characterized in that: In the transmission mode, the radio frequency switch (SW) is disconnected, the coupling coil (L3) is open-circuited, the coupling between the coupling coil (L3) and the primary coil (L1) of the transformer has little effect on the primary coil (L1) of the transformer, and the coupling between the coupling coil (L3) and the secondary coil (L2) of the transformer has little effect on the secondary coil (L2) of the transformer.
7. The transmitting end antenna switch based on a three-coil transformer according to claim 3, characterized in that: In the receiving mode, the radio frequency switch (SW) is turned on, the radio frequency power amplifier (PA) is turned off, the coupling coil (L3) is short-circuited, the coupling coil (L3) affects the inductance of the primary coil (L1) of the transformer through a coupling coefficient k13, and the coupling coil (L3) affects the inductance of the secondary coil (L2) of the transformer through a coupling coefficient k23; the closing impedance of the radio frequency power amplifier (PA) is increased, and the leakage of the received signal is reduced.
8. The transmitting end antenna switch based on a three-coil transformer according to claim 7, characterized in that: In the receiving mode, the off impedance of the RF power amplifier (PA) is increased to γ times of the original value.
9. The transmitting end antenna switch based on a three-coil transformer according to claim 3, characterized in that: The RF switch (SW) is implemented by a transistor M1. The on and off of the RF switch (SW) is realized by a control signal B1 connected to the gate of the transistor M1 through a large resistor R1. When the control signal B1 is at a high level, the transistor M1 is turned on, and when the control signal B1 is at a low level, the transistor M1 is turned off.
10. The transmitting end antenna switch based on a three-coil transformer according to claim 6, characterized in that: In the transmitting mode, the control signal B1 is set to a low level 0, and the control signal is transmitted to the gate of the transistor M1 through the large resistor R1. At this time, the transistor M1 is disconnected and the coupling coil (L3) is open.