Notch circuit and power amplifier module

Abstract

The present invention provides a notch circuit and a power amplifier module. The notch circuit is electrically connected to a first power amplifier. The first power amplifier amplifies a first input transmission signal to generate a first output transmission signal. The notch circuit includes an inductor and a capacitor. The inductor is electrically connected to the first power amplifier. The inductor receives a first power supply voltage. The amplitude of the first power supply voltage varies with the first input transmission signal. The capacitor is electrically connected to the inductor. When the modulation frequency of the first power supply voltage corresponds to the stop band of the notch circuit, the first output transmission signal is attenuated. The notch circuit and the power amplifier module according to the present invention can reduce the side effects caused by self-interference in the transceiver.

Description

Technical Field

[0001] The present disclosure relates generally to notch circuits and power amplifier modules, and more particularly, to notch circuits and power amplifier modules capable of reducing self-interference effects in transceivers. Background Art

[0002] Nowadays, consumer electronic devices are equipped with communication functions and transceivers are widely used. Figure 1 1 is a schematic diagram illustrating a transceiver having a transmitter and a receiver. The transceiver 10 includes a transmitter (Tx) 11 for transmitting an output transmission signal (output transmission signal) Tx_out and a receiver (Rx) 13 for receiving an input reception signal (input reception signal) Rx_in.

[0003] In current cellular systems, the transmission band and the reception band are usually spaced apart at a small interval, so that some of the output transmission signals Tx_out are received by the receiver 13. The output transmission signals Tx_out cause interference to the receiver 13, and thus the quality of the input reception signal Rx_in is degraded. In other words, the receiver 13 may suffer from self-interference originating from the transmitter 11. Figure 1 and Figure 2 .

[0004] Figure 2 1 is a schematic spectrum diagram illustrating the self-interference phenomenon. The horizontal axis represents frequency and the vertical axis represents signal strength. Curves L1 and L2 represent output transmission signals Tx_out having two different center frequencies F_txa and F_txb, respectively. The receiver 13 provides a band pass function, and curve L3 represents the receiver frequency band of the receiver 13.

[0005] Assume that the center frequency F_txa is lower than the center frequency F_txb, and the center frequency F_txb is lower than the center frequency F_rx of the receiver frequency band.

[0006] Therefore, the slope portion of the curve L2 partially overlaps with the curve L3 . This means that the output transmission signal Tx_out with the center frequency F_txb has a relatively strong strength when received by the receiver 13 , and may cause serious self-interference to the receiver 13 .

[0007] On the other hand, curve L3 does not cover the slope portion of curve L1 but covers the flat portion of curve L1. This means that the output transmission signal Tx_out having the center frequency F_txa has a weaker strength when received by the receiver 13 and is less likely to cause self-interference to the receiver 13.

[0008] exist Figure 2 In the embodiment, it is assumed that the center frequency F_txa, F_txb of the output transmission signal Tx_out is lower than the center frequency F_rx of the receiver frequency band. In practical applications, the center frequency of the output transmission signal Tx_out can be lower or higher than the center frequency F_rx of the receiver frequency band. However, self-interference phenomenon exists in both cases.

[0009] The center frequency of the output transmission signal Tx_out and the center frequency of the receiver frequency band are defined by the communication standard (e.g., 4G, 5G). However, due to limited frequency band resources, it becomes increasingly difficult to separate the center frequency of the output transmission signal Tx_out from the receiver frequency band. Therefore, the center frequency of the output transmission signal Tx_out and the center frequency of the receiver frequency band become closer, and self-interference tends to become an inevitable phenomenon. Summary of the invention

[0010] In view of this, the present disclosure proposes a trap circuit and a power amplifier module to solve the above problems.

[0011] According to one embodiment, a notch circuit is provided. The notch circuit is electrically connected to a first power amplifier. The first power amplifier amplifies a first input transmission signal to generate a first output transmission signal. The notch circuit includes an inductor and a capacitor. The inductor is electrically connected to the first power amplifier. The inductor receives a first power supply voltage (Vpa). The amplitude of the first power supply voltage (Vpa) varies with the first input transmission signal (Tx_in). The capacitor is electrically connected to the inductor. When the modulation frequency of the first power supply voltage (Vpa) corresponds to the stop band of the notch circuit, the first output transmission signal (Tx_out1) is attenuated.

[0012] According to another embodiment, a power amplifier module is provided. The power amplifier module includes a power amplifier and a trap circuit. The power amplifier receives a first power supply voltage (Vpa). In addition, the power amplifier amplifies an input transmission signal (Tx_in) based on the first power supply voltage (Vpa) to generate an output transmission signal (Tx_out1). The amplitude of the first power supply voltage (Vpa) varies with the input transmission signal (Tx_in). The trap circuit is electrically connected to the power amplifier. The trap circuit includes an inductor and a capacitor. The inductor is electrically connected to the power amplifier. The inductor receives the first power supply voltage (Vpa). The capacitor is electrically connected to the inductor. When the modulation frequency of the first power supply voltage (Vpa) corresponds to a stop band, the output transmission signal (Tx_out1) is attenuated.

[0013] The notch circuit and the power amplifier module according to the present invention can reduce the side effects caused by self-interference in the transceiver.

[0014] These and other objects of the present invention will no doubt become apparent to those of ordinary skill in the art after reading the following detailed description of the preferred embodiments illustrated in the various drawings and figures. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In the following detailed description, for the purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. However, it is apparent that one or more embodiments may be practiced without these specific details. In other cases, well-known structures and devices are schematically shown to simplify the drawings.

[0016] Figure 1 is a schematic diagram illustrating a transceiver having a transmitter and a receiver.

[0017] Figure 2 is a schematic spectrum diagram illustrating the self-interference phenomenon.

[0018] Figure 3 is a schematic diagram illustrating a power amplifier used at the output stage of a transmitter.

[0019] Figure 4A and Figure 4B is a schematic diagram illustrating power consumption of a power amplifier corresponding to different types of power supply voltages Vpa.

[0020] Figure 5 is a schematic diagram illustrating a power amplifier module used in an output stage of a transmitter according to an embodiment of the present disclosure.

[0021] Figure 6 is a schematic diagram illustrating an operation mode of a power amplifier module according to an embodiment of the present disclosure when a notch circuit is enabled.

[0022] Figure 7 is a schematic diagram illustrating an operation mode of a power amplifier module according to an embodiment of the present disclosure when a notch circuit is disabled. DETAILED DESCRIPTION

[0023] Certain words are used in the specification and claims to refer to specific components. It should be understood by those skilled in the art that electronic equipment manufacturers may use different terms to refer to the same component. The specification and claims do not distinguish components by differences in name, but by differences in the functions of the components. The term "including" mentioned throughout the specification and claims is an open-ended term and should be interpreted as "including but not limited to". In addition, the term "coupled" is used herein to include any direct and indirect electrical connection means. Therefore, if the text describes a first device as being electrically connected to a second device, it means that the first device can be directly connected to the second device, or indirectly connected to the second device through other devices or connection means.

[0024] As described above, the presence of self-interference may endanger the operation of the receiver, and it is difficult to eliminate the self-interference phenomenon by separating the output transmission signal Tx_out and the center frequency of the receiver band. Therefore, a notch circuit and a power amplifier module are provided in the present disclosure to reduce the side effects caused by self-interference.

[0025] Figure 3 is a schematic diagram illustrating a power amplifier used at the output stage of a transmitter. The power amplifier PA21a receives and amplifies an input transmission signal Tx_in to generate an output transmission signal Tx_out. The power amplifier 21a operates based on a power supply voltage Vpa. However, using a power amplifier may result in more self-interference to the receiver.

[0026] Figure 4A and Figure 4B is a schematic diagram illustrating power consumption of a power amplifier corresponding to different types of power supply voltages Vpa. Figure 4A In the case of Vpa, the power supply voltage Vpa is a constant voltage. Figure 4B In the example, the power supply voltage Vpa is the envelope tracking signal. That is, Figure 4B The amplitude of the power supply voltage Vpa in varies with the input transmission signal Tx_in.

[0027] exist Figure 4A and Figure 4B In FIG. 1 , the area indicated by the diagonal lines (area Ppa) represents the actual power consumption of the power amplifier 21a, and the area indicated by the dotted lines ( Figure 4A The area Pc and Figure 4B The area Pet in represents the power provided to the power amplifier 21a but not used by the power amplifier 21a. Figure 4A The area Pc and Figure 4B The area Pet in represents unnecessary power consumption or wasted power consumption. Obviously, Figure 4A The area Pc is greater than Figure 4B The area in Pet, Figure 4A The power consumption wasted in Figure 4B Wasted power consumption.

[0028] Since power consumption is a major concern for portable devices, it is preferred to use an envelope tracking signal as the power supply voltage Vpa. However, using an envelope tracking signal may worsen the self-interference phenomenon.

[0029] Modern wireless communication standards support multiple frequency bands, which can be divided into high frequency band, mid frequency band and low frequency band according to the frequency.

[0030] When the power amplifier operates in the low frequency band, the interval between the center frequency of the output transmission signal Tx_out and the center frequency of the receiver frequency band is relatively narrow (e.g., 40 MHz). When the power amplifier operates in the high frequency band or the medium frequency band, the interval between the center frequency of the output transmission signal Tx_out and the center frequency of the receiver frequency band is relatively wide (e.g., 100 MHz to 200 MHz). The wider the frequency interval between the center frequency of the output transmission signal Tx_out and the center frequency of the receiver frequency band, the smaller the chance of the self-interference phenomenon. Therefore, special attention should be paid to the self-interference phenomenon in the low frequency band.

[0031] Figure 5 is a schematic diagram illustrating a power amplifier module used in an output stage of a transmitter according to an embodiment of the present disclosure. The power amplifier module 32 is used together with the envelope tracking module 30, which provides an envelope tracking signal as a power supply voltage Vpa. The envelope tracking signal is a modulated signal with a modulation bandwidth. In response to changes in the input transmission signal Tx_in, the amplitude of the envelope tracking signal can be dynamically adjusted. The power amplifier module 32 receives the power supply voltage Vpa and the switch control signal Ssw from the envelope tracking module 30.

[0032] The power amplifier module 32 includes amplifiers 31a and 31b, a switch sw and a notch circuit (band-stop or band-rejection filter) 321. When the notch circuit is enabled and when the modulation frequency of the power supply voltage (Vpa) corresponds to the stopband, the output transmission signal (Tx_out) is attenuated. The stopband corresponds to a frequency band where self-interference is likely to occur. For example, the stopband is between 30MHz and 60MHz.

[0033] The trap circuit 321 includes a capacitor C and an inductor L electrically connected in series. The inductor L is electrically connected to the power supply voltage terminal Nv and receives the power supply voltage Vpa. The capacitor C is electrically connected to the inductor L and the switch sw. Depending on the desired center frequency of the stop band, the capacitance value of the capacitor C and the inductance value of the inductor L can be deliberately selected / determined.

[0034] When the notch circuit 321 is enabled by the switch sw, the output transmission signal Tx_out at most frequencies remains substantially unchanged. Meanwhile, when the modulation frequency of the power supply corresponds to the stop band, the intensity of the output transmission signal Tx_out is attenuated to a very low level.

[0035] As described above, the power supply voltage Vpa is an envelope tracking signal with a modulation bandwidth. Therefore, once the notch circuit 321 is enabled and in operation, the power supply voltage Vpa is filtered out when the modulation frequency of the power supply voltage Vpa corresponds to the stop band of the notch circuit 321. According to an embodiment of the present disclosure, the stop band of the notch circuit 321 corresponds to the overlapping frequency range of the output transmission signal Tx_out and the receiver frequency band of the receiver 13.

[0036] In the specification, the power amplifier 31a corresponds to the low frequency band, and the power amplifier 31b corresponds to the middle frequency band and / or the high frequency band. The power amplifier 31a receives and amplifies the input transmission signal Tx_in1 to generate the output transmission signal Tx_out1. The power amplifier 31b receives and amplifies the input transmission signal Tx_in2 to generate the output transmission signal Tx_out2.

[0037] The modulation bandwidth of power supply voltage Vpa is less than the frequency interval (frequencyseparation) corresponding to low frequency band. The frequency interval corresponding to low frequency band is defined as the frequency interval between the center frequency of output transmission signal Tx_out1 and the center frequency of receiver frequency band corresponding to low frequency band. Similarly, the modulation bandwidth of power supply voltage Vpa is less than the frequency interval corresponding to intermediate frequency band and / or high frequency band. The frequency interval corresponding to intermediate frequency band and / or high frequency band is defined as the frequency interval between the center frequency of output transmission signal Tx_out2 and the center frequency of receiver frequency band corresponding to intermediate frequency band and / or high frequency band. In addition, the frequency interval corresponding to low frequency band is less than the frequency interval corresponding to intermediate frequency band and / or high frequency band.

[0038] In practical applications, the center frequency of the output transmission signal Tx_out1 may be higher or lower than the center frequency of the receiver frequency band corresponding to the low frequency band. In addition, the center frequency of the output transmission signal Tx_out2 may be higher or lower than the center frequency of the receiver frequency band corresponding to the mid-frequency band and / or the high-frequency band.

[0039] According to an embodiment of the present disclosure, depending on the operating mode of the transceiver, the power amplifiers 31a, 31b are selectively or alternatively enabled. When the transceiver operates in an operating mode in which a low frequency band is selected for wireless communication, the power amplifier 31a is enabled and the power amplifier 31b is disabled. On the other hand, when the transceiver operates in an operating mode in which a mid-frequency band and / or a high frequency band is selected for wireless communication, the power amplifier 31a is disabled and the power amplifier 31b is enabled.

[0040] In practical applications, the number of power amplifiers in the power amplifier module 32 is not limited. For example, in the case where the power amplifier module 32 includes only one power amplifier, the switch sw may be omitted, and the capacitor C may be electrically connected to the ground terminal Gnd.

[0041] The switch sw is electrically connected to the envelope tracking module 30, the capacitor C and the ground terminal Gnd. The switch sw is controlled by the switch signal Ssw to selectively enable / disable the trap circuit 321. In the specification, the switch sw is assumed to be an NMOS transistor. Therefore, when the gate terminal of the switch sw is at a high voltage level, the switch sw is turned on, and vice versa. The implementation of the switch sw and its control mechanism may be different in actual applications.

[0042] As described above, the notch circuit 321 is provided to reduce self-interference, and when the transceiver operates in the low frequency band, the self-interference phenomenon is more serious. Therefore, when the transceiver operates in the low frequency band, the notch circuit 321 is enabled to reduce self-interference.

[0043] Figure 6 is a schematic diagram illustrating an operation mode of a power amplifier module according to an embodiment of the present disclosure when a notch circuit is enabled. The power amplifier 31a is enabled and the power amplifier 31b is disabled. Operating based on a power supply voltage Vpa, the power amplifier 31a receives and amplifies an input transmission signal Tx_in1 to generate an output transmission signal Tx_out1. The amplitude of the power supply voltage Vpa varies with the input transmission signal Tx_in1.

[0044] When the transceiver operates in the low frequency band, the switch control signal Ssw is at a high voltage level H, and the notch circuit 321 is enabled. By adopting the notch circuit 321, the self-interference caused by the output transmission signal Tx_out1 can be significantly reduced.

[0045] Figure 7is a schematic diagram illustrating an operating mode of a power amplifier module according to an embodiment of the present disclosure when a trap circuit is disabled. The power amplifier 31b is enabled and the power amplifier 31a is disabled. The power amplifier 31b operates based on the power supply voltage Vpa, receives and amplifies the input transmission signal Tx_in2 to generate the output transmission signal Tx_out2. The amplitude of the power supply voltage Vpa varies with the input transmission signal Tx_in2.

[0046] When the transceiver operates in the mid-band and / or high-band, the switch control signal Ssw is at a low voltage level L, and the trap circuit 321 is disabled. Since the self-interference is not serious in the mid-band and / or high-band, Figure 7 The middle notch circuit 321 is disabled.

[0047] The operation and status of components and signals related to power amplifier module 32 are summarized in the following table.

[0048] sheet

[0049]

[0050] The physical implementation and location of the trap circuit 321, the switch sw and the power amplifiers 31a, 31b are not limited. For example, the trap circuit 321, the switch sw and the power amplifiers 31a, 31b can be integrated into the same circuit module or the same semiconductor chip (integrated circuit). Optionally, the trap circuit, the switch sw and the power amplifier can be placed separately in a printed circuit board (PCB).

[0051] According to an embodiment of the present disclosure, using a power amplifier module, a transceiver can dynamically turn on / off a notch circuit in response to different frequency bands. For situations where the self-interference level is high, the notch circuit is enabled to reduce the self-interference. For situations where the self-interference level is low, the notch circuit will be disabled.

[0052] It will be apparent to those skilled in the art that various modifications and variations may be made to the disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with the true scope of the disclosure being indicated by the following claims and their equivalents.

Claims

1. A trap circuit electrically connected to a first power amplifier, the first power amplifier being configured to amplify a first input transmission signal to generate a first output transmission signal, wherein: The trap circuit comprises: an inductor electrically connected to the first power amplifier and configured to receive a first power supply voltage, wherein a magnitude of the first power supply voltage varies with the first input transmission signal; and a capacitor electrically connected to the inductor, wherein the first output transmission signal is attenuated when a modulation frequency of the first supply voltage corresponds to a stop band of the notch circuit; The modulation bandwidth of the first power supply voltage is smaller than a first frequency interval between a center frequency of the first output transmission signal and a center frequency of a first receiver frequency band.

2. The trap circuit according to claim 1, characterized in that: The first power supply voltage is provided by an envelope tracking module.

3. The trap circuit according to claim 1, characterized in that: The capacitor is electrically connected to a second supply voltage.

4. The trap circuit according to claim 1, characterized in that: The trap circuit is also electrically connected to the second power amplifier.

5. The trap circuit according to claim 4, characterized in that: The second power amplifier receives and amplifies a second input transmission signal and generates a second output transmission signal accordingly.

6. The trap circuit according to claim 5, characterized in that: The first output transmission signal corresponds to a first frequency band, and The second output transmission signal corresponds to a second frequency band, wherein the first frequency band is lower than the second frequency band.

7. The trap circuit according to claim 4, characterized in that: The trap circuit is electrically connected to a switch, and the switch is electrically connected to a second supply voltage, wherein the switch is configured to selectively enable the trap circuit.

8. The trap circuit according to claim 7, characterized in that: When the first power amplifier is enabled and the second power amplifier is disabled, the switch is turned on and the trap circuit is enabled; as well as When the first power amplifier is disabled and the second power amplifier is enabled, the switch is open and the notch circuit is disabled.

9. The trap circuit according to claim 1, characterized in that: The center frequency of the first output transmission signal is lower or higher than the center frequency of the first receiver frequency band.

10. The trap circuit according to claim 1, characterized in that: The first frequency spacing is smaller than a second frequency spacing between a center frequency of the second output transmission signal and a center frequency of the second receiver frequency band.

11. The trap circuit according to claim 1, characterized in that: The inductance of the inductor and the capacitance of the capacitor are related to the stop band, and the stop band is between 30 MHz and 60 MHz.

12. A power amplifier module, comprising: a power amplifier configured to receive a first power supply voltage and amplify an input transmission signal based on the first power supply voltage to generate an output transmission signal, wherein the amplitude of the first power supply voltage varies with the input transmission signal; and A trap circuit, electrically connected to the power amplifier, comprising: an inductor electrically connected to the power amplifier and configured to receive the first supply voltage; and a capacitor electrically connected to the inductor, wherein the output transmission signal is attenuated when a modulation frequency of the first supply voltage corresponds to a stop band of the notch circuit; The modulation bandwidth of the first power supply voltage is smaller than the frequency interval between the center frequency of the output transmission signal and the center frequency of the receiver frequency band.

13. The power amplifier module according to claim 12, characterized in that: The power amplifier module is electrically connected to the envelope tracking module, and the first power supply voltage is provided by the envelope tracking module.

14. The power amplifier module according to claim 12, characterized in that: Also includes: A switch, electrically connected to the capacitor and a second supply voltage, is configured to selectively enable the trap circuit.

15. The power amplifier module according to claim 14, characterized in that: The trap circuit, the switch and the power amplifier are integrated into an integrated circuit or are placed on a printed circuit board separately.

16. The power amplifier module according to claim 12, characterized in that: The inductance of the inductor and the capacitance of the capacitor are related to the stop band, and the stop band is between 30 MHz and 60 MHz.

17. A transceiver, comprising: A transmitter, the transmitter comprising a power amplifier module, the power amplifier module comprising a power amplifier and a trap circuit, wherein: The power amplifier receives an input transmission signal and amplifies the input transmission signal to generate an output transmission signal, the power supply voltage of the power amplifier is an envelope tracking signal, the amplitude of which varies with the input transmission signal of the power amplifier, The notch circuit has a stop band electrically connected to a supply voltage of the power amplifier, a receiver having a receiver frequency band; wherein a stop band of the notch circuit corresponds to an overlapping frequency range of the output transmission signal and a receiver frequency band of the receiver; The modulation bandwidth of the power supply voltage is smaller than the frequency interval between the center frequency of the output transmission signal and the center frequency of the receiver frequency band.

18. The transceiver according to claim 17, wherein: The trap circuit includes an inductor and a capacitor coupled in series, A first end of the inductor is coupled to a power supply voltage of the power amplifier, and a second end of the inductor is coupled to the capacitor.

19. The transceiver according to claim 18, wherein: The trap circuit is electrically connected to a switch configured to selectively enable the trap circuit.

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