CN117579021A - Filter circuit and wireless device - Google Patents

Abstract

The embodiment of the invention discloses a filter circuit and wireless equipment, wherein a capacitor module and a filter are arranged in the filter circuit, the capacitor module has self-resonant frequency matched with the harmonic frequency of a radio frequency signal provided by a radio frequency circuit, the capacitor module is used for carrying out harmonic suppression on the radio frequency signal to obtain a signal to be filtered, and then the filter is used for carrying out filtering treatment on the signal to be filtered to obtain a transmitting signal. Therefore, the harmonic suppression can be effectively carried out on the radio frequency signals, the quality of the transmitted signals can be improved, and the filter circuit is simple and easy to realize and has higher applicability.

Description

Filter circuit and wireless device

Technical Field

The present invention relates to the field of electronic power technology, and in particular, to a filter circuit and a wireless device.

Background

With the continuous development of electronic power technology and the improvement of integrated circuit level, electronic devices (such as mobile phones and tablet computers) have more and more functions, so that people's daily life is more convenient. In order to improve the user experience of the electronic device, the electronic device is continuously evolving towards multiple frequency bands, multiple systems, high communication quality, large screen duty ratio, high battery capacity, multiple product functions and the like, so that the design integration level of the electronic device is higher and higher, and the area of a radio frequency main board of the electronic device is greatly reduced, that is, the layout space of a radio frequency circuit in the electronic device is smaller and smaller. As layout space decreases, radio frequency signals often generate larger harmonic terms during processing, thereby generating spurious radiation (RadioSpectrum Emission, RSE) signals, which severely affects the communication quality of the radio frequency signals.

In the prior art, a shielding case is generally used for harmonic suppression. In particular, metallic shields may be provided for harmonic rejection in components of the radio frequency circuit (e.g., power amplifiers, digital signal processors, etc.).

On the one hand, in the prior art, a mode of adopting a shielding case to inhibit harmonic waves cannot effectively inhibit the harmonic waves; on the other hand, the shielding case in the prior art increases the design complexity of the radio frequency circuit, and therefore the limitation is high.

Disclosure of Invention

In view of this, the embodiment of the invention provides a filter circuit and a wireless device, which can effectively perform harmonic suppression on a radio frequency signal, can improve the quality of a transmitted signal, and has the advantages of simple and easy implementation and higher applicability.

In a first aspect, an embodiment of the present invention provides a filter circuit, including:

the capacitor module is used for carrying out harmonic suppression on the radio frequency signal provided by the radio frequency circuit so as to obtain a signal to be filtered;

the filter is coupled with the capacitor module and is used for filtering the signal to be filtered so as to obtain a transmitting signal;

the capacitor module has a self-resonant frequency matched with the harmonic frequency of the radio frequency signal.

In some embodiments, the radio frequency signal has a different harmonic frequency, the capacitive module includes a number of capacitors equal to the number of harmonic frequencies, each capacitor having a self-resonant frequency that matches each harmonic frequency.

In some embodiments, the filter circuit further comprises:

and the impedance matching circuit is coupled with the capacitor module and the filter and is used for carrying out impedance transformation based on the additional impedance generated by the capacitor module so as to match the output impedance of the radio frequency circuit.

In some embodiments, the filter comprises:

and the band-pass filter is used for carrying out filtering processing on the signal to be filtered so as to obtain the transmitting signal in a preset frequency range.

In some embodiments, the impedance matching circuit comprises:

an inductor coupled between an input of the band pass filter and an output of the radio frequency circuit;

a first capacitor coupled between an input terminal of the band-pass filter and a ground terminal;

and the second capacitor is coupled between the output end of the radio frequency circuit and the ground end.

In some embodiments, the radio frequency circuit comprises:

and the Bluetooth chip is coupled with the inductor and is used for providing the radio frequency signal.

In some embodiments, the capacitive module comprises:

and the third capacitor is coupled between the output end of the radio frequency circuit and the ground end.

In a second aspect, an embodiment of the present invention provides a wireless device, including:

a radio frequency circuit for providing a radio frequency signal;

the filter circuit of the first aspect.

In some embodiments, the wireless device further comprises:

and the signal sending circuit is coupled with the filtering circuit and is used for transmitting the transmitting signal provided by the filtering circuit to the receiving equipment.

In some embodiments, the signaling circuit includes:

a radio frequency interface coupled between the filter circuit and an antenna for transmitting the transmit signal to the antenna;

and an antenna for transmitting the transmission signal to the receiving device.

According to the embodiment of the invention, the capacitor module and the filter are arranged in the filter circuit, the capacitor module has the self-resonant frequency matched with the harmonic frequency of the radio frequency signal provided by the radio frequency circuit, the capacitor module is used for carrying out harmonic suppression on the radio frequency signal to obtain the signal to be filtered, and the filter is used for carrying out filtering treatment on the signal to be filtered to obtain the transmitting signal. Therefore, the harmonic suppression can be effectively carried out on the radio frequency signals, the quality of the transmitted signals can be improved, and the filter circuit is simple and easy to realize and has higher applicability.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 is a circuit diagram of a filter circuit according to an embodiment of the present invention;

FIG. 2 is a circuit diagram of a filter circuit according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of the operating frequency and the capacitive impedance of the capacitor according to the embodiment of the present invention;

FIG. 4 is a schematic diagram of the operating frequency and inductive impedance of a capacitor according to an embodiment of the present invention;

fig. 5 is an equivalent circuit diagram of a filter circuit according to an embodiment of the present invention.

Detailed Description

The present application is described below based on examples, but the present application is not limited to only these examples. In the following detailed description of the present application, certain specific details are set forth in detail. The present application will be fully understood by those skilled in the art without a description of these details. Well-known methods, procedures, flows, components and circuits have not been described in detail so as not to obscure the nature of the present application.

Moreover, those of ordinary skill in the art will appreciate that the drawings are provided herein for illustrative purposes and that the drawings are not necessarily drawn to scale.

Meanwhile, it should be understood that in the following description, "circuit" refers to a conductive loop constituted by at least one element or sub-circuit through electrical connection or electromagnetic connection. When an element or circuit is referred to as being "connected to" another element or being "connected between" two nodes, it can be directly coupled or connected to the other element or intervening elements may be present and the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled to" or "directly connected to" another element, it means that there are no intervening elements present between the two.

Unless the context clearly requires otherwise, the words "comprise," "comprising," and the like throughout the application are to be construed as including but not being exclusive or exhaustive; that is, it is the meaning of "including but not limited to".

In the description of the present application, it should be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Furthermore, in the description of the present application, unless otherwise indicated, the meaning of "a plurality" is two or more.

In the following description, an example in which the filter circuit is applied to a bluetooth headset (i.e., a wireless device) will be described. It will be appreciated that the filter circuit of this embodiment may also be designed for use in a variety of devices requiring harmonic suppression. For example, the filter circuit may be disposed in an electronic device such as an intelligent home device (e.g., an intelligent desk lamp, etc.), an intelligent bracelet, a bluetooth headset, a bluetooth remote controller, etc.

Fig. 1 is a circuit diagram of a filter circuit according to an embodiment of the present invention. As shown in fig. 1, the filter circuit includes a filter 1 and a capacitor module 2. Wherein, the filter 1 is coupled to the capacitor module 2.

In this embodiment, the capacitor module 2 may perform harmonic suppression on the radio frequency signal provided by the radio frequency circuit to obtain a signal to be filtered, and transmit the signal to be filtered to the filter 1. The filter 1 may then filter the signal to be filtered to obtain the transmit signal.

In this embodiment, since the mode of harmonic suppression using the shielding case in the prior art cannot effectively suppress the harmonic, and the shielding case increases the complexity of designing the radio frequency circuit, the limitation is higher. For this case, the present embodiment sets the capacitor module 2 in the filter circuit, and the capacitor module 2 has a self-resonant frequency (Self Resonant Frequency, SRF) matched with the harmonic frequency of the radio frequency signal. That is, the self-resonant frequency corresponding to the capacitor module 2 is determined according to the harmonic frequency of the radio frequency signal, so that the capacitor module 2 can effectively perform harmonic suppression on the radio frequency signal.

In this embodiment, the harmonic frequency of the harmonic signal carried by the radio frequency signal output by the radio frequency circuit may be detected in advance by the detection device. Detection devices such as spectrum analyzers (e.g., real-time spectrum analyzer (Real Time Spectrum Analyzer, RTSA), scan-tuned spectrum analyzer (Sweep Tuned Spectrum Analyzer, STSA), etc.), radio frequency analyzers, and the like. Wherein the spectrum analyzer may analyze the spectral characteristics of the radio frequency signal in the frequency domain to determine the harmonic frequencies of the radio frequency signal. The RF analyzer is one kind of instrument based on frequency spectrum analysis and phase measurement, and may be used in measuring the frequency, amplitude, phase and other parameters of RF signal to determine the harmonic frequency of RF signal.

Optionally, the filter circuit further includes a controller, and the controller is connected with the radio frequency circuit, and the controller can detect the harmonic frequency of the radio frequency signal provided by the radio frequency circuit in real time. The controller may be an electronic device with functions of signal detection, signal processing, data storage, etc. The controller may be implemented by an MCU (Microcontroller Unit, micro control unit), an FPGA (Field-Programmable Gate Array, field programmable gate array), an ASIC (Application Specific Integrated Circuit, application-specific integrated circuit), a CPU (Central Process Unit, central processing unit), or the like.

In this embodiment, since the rf signal may generate a harmonic signal when it is processed by components such as a Power Amplifier (PA) and a digital signal processor (Digital Signal Processing, DSP) in the rf circuit, the self-resonant frequency matched with the capacitor module 2 may be determined according to the detected harmonic frequency of the rf signal output by the rf circuit, and then a capacitor having the self-resonant frequency is set in the capacitor module 2, so that the capacitor module 2 may effectively perform harmonic suppression on the rf signal.

Alternatively, the controller may control the capacitor having a self-resonant frequency matching the real-time detected harmonic frequency to perform harmonic suppression on the radio frequency signal, wherein the capacitor module 2 includes the capacitor. That is, the harmonic wave carried by the radio frequency signal may be generated by a component in the radio frequency circuit, and may also be generated by an environmental factor (for example, there are other bluetooth devices, wi-Fi devices, etc. near the wireless device, and the bluetooth devices, wi-Fi devices, etc. are close to or partially overlapped with the operating frequency of the wireless device in the frequency spectrum, and may generate a harmonic signal), for this case, the embodiment may determine in advance the harmonic frequency of the harmonic signal caused by the environmental factor (for example, place the bluetooth devices, wi-Fi devices, etc. near the wireless device, and detect the harmonic frequency of the harmonic signal carried by the radio frequency signal output by the radio frequency circuit of the wireless device through the detection device), and then set a capacitor having a self-resonant frequency matched with the harmonic frequency in the capacitor module 2, so that the controller may determine the corresponding capacitor in the capacitor module 2 according to the harmonic frequency detected in real time to perform harmonic suppression. In the following description, the generation of harmonic signals by components in a radio frequency circuit is illustrated as an example.

According to the embodiment of the invention, the capacitor module and the filter are arranged in the filter circuit, the capacitor module has the self-resonant frequency matched with the harmonic frequency of the radio frequency signal provided by the radio frequency circuit, the capacitor module is used for carrying out harmonic suppression on the radio frequency signal to obtain the signal to be filtered, and the filter is used for carrying out filtering treatment on the signal to be filtered to obtain the transmitting signal. Therefore, the harmonic suppression can be effectively carried out on the radio frequency signals, the quality of the transmitted signals can be improved, and the filter circuit is simple and easy to realize and has higher applicability.

Fig. 2 is a circuit diagram of a filter circuit according to an embodiment of the present invention. As shown in fig. 2, the filter circuit 100 further includes an impedance matching circuit 3. The impedance matching circuit 3 is coupled between the capacitor module 2 and the filter 1. Wherein the filter circuit 100 may be provided in a wireless device.

In the present embodiment, the wireless device includes a filter circuit 100, a signal transmission circuit 200, and a radio frequency circuit 300. The capacitor module 2 of the filter circuit 100 is coupled to the rf circuit 300. The filter 1 in the filter circuit 100 is coupled between the signal transmitting circuit 200 and the impedance matching circuit 3.

In this embodiment, the radio frequency circuit 300 is configured to generate a radio frequency signal for processing by the filter circuit 100 and the signal transmitting circuit 200 and transmitting the processed signal to the receiving device. The receiving device may be an electronic device having functions of information processing, information transmission, information storage, and the like, such as a mobile phone, a tablet computer, a television, and the like.

Optionally, the radio frequency circuit 300 includes a Bluetooth chip (e.g., BT chip (BT), BLE chip (Bluetooth Low Energy ), etc.), a signal processing circuit (e.g., flash circuit, etc., which may be used to store Firmware (i.e., firmware), configuration information (e.g., unique identification information of the wireless device, pairing (i.e., communication connection) parameters of the wireless device and the receiving device), etc.), a Bluetooth chip I/O interface (i.e., IN/OUT interface), a power amplifier, etc.

Alternatively, the radio frequency circuit 300 may generate the radio frequency signal in a variety of ways. For example, in the case of voice communication, the wireless device is a bluetooth headset, the bluetooth chip may convert the audio information of the user into a digital signal through an analog-to-digital converter (Analog to Digital Converter, ADC), and then process the digital signal through a digital signal processor (Digital Signal Processing, DSP) (for example, the digital signal processor mixes the digital signal with a frequency provided by a radio frequency oscillator through a mixer) to obtain a radio frequency signal, so as to transmit the radio frequency signal to the mobile phone after processing the radio frequency signal through the filter circuit 100 and the signal transmitting circuit 200. For another example, the wireless device is a bluetooth remote controller, and the wireless device includes a key, where the key is used to trigger a control signal, and after the user triggers the key, the bluetooth chip can convert the control signal into a radio frequency signal, amplify the radio frequency signal through a power amplifier, and then process the radio frequency signal through the filter circuit 100 and the signal transmitting circuit 200 and transmit the radio frequency signal to the television.

It should be noted that, in the process of generating the radio frequency signal by the radio frequency circuit 300, due to the nonlinear devices such as the power amplifier, the Flash circuit, the mixer of the bluetooth chip, etc. in the radio frequency circuit 300, harmonic signals may be generated and radiated outwards when the signal passes through these nonlinear devices, and these harmonic signals may be referred to as RSE signals. The RSE signal may cause electromagnetic interference to other devices/circuits, thereby affecting the electrical performance of the other devices or circuits, and thus the rf circuit 300 may carry harmonic signals when generating the rf signal. Wherein the harmonic signals are, for example, second harmonic signals, third harmonic signals, fifth harmonic signals, etc. The order of the harmonic signal characterizes the ratio of the harmonic frequency of the harmonic signal to the fundamental frequency.

In this embodiment, considering that harmonic frequencies of harmonic signals generated by different nonlinear devices of the radio frequency circuit 300 may be different, for this case, the embodiment may detect in advance one or more harmonic frequencies (a plurality of harmonic frequencies, for example, harmonic frequencies of harmonic signals of different orders) of the radio frequency signal output by the radio frequency circuit 300, and then set a plurality of capacitors as many as the number of harmonic frequencies in the capacitor module 2, each capacitor having a self-resonant frequency matched with the corresponding harmonic frequency.

For example, the harmonic frequencies of the output RF signals of the RF circuit 300 are f _a 、f _b And f _c Three capacitors a11, b11 and c11, respectively, may be provided in the capacitor module 2. Capacitor a11 has a frequency f equal to the harmonic frequency _a The self-resonant frequency a12 and the capacitor b11 are matched with the harmonic frequency f _b Self-resonant frequency b12 matched, capacitor c11 having a frequency f corresponding to the harmonic frequency _c A matched self-resonant frequency c12.

It should be noted that, the capacitor having a self-resonant frequency that matches a certain harmonic frequency may mean that the self-resonant frequency of the capacitor is the same as the certain harmonic frequency, or that the self-resonant frequency of the capacitor is close to the certain harmonic frequency (i.e., the self-resonant frequency of the capacitor is within a predetermined range of the certain harmonic frequency, or the difference between the self-resonant frequency of the capacitor and the certain harmonic frequency is less than a threshold value). That is, considering that it may not be possible to determine a capacitance having the same self-resonance frequency as the harmonic frequency, for this case, a capacitance having a self-resonance frequency close to the harmonic frequency may be selected. Further, the impedance of the capacitor includes a capacitive impedance and an inductive impedance. A schematic diagram of the operating frequency and the capacitive impedance of the capacitor can be referred to fig. 3. A schematic diagram of the operating frequency and inductive impedance of the capacitor can be referred to in fig. 4.

Fig. 3 and fig. 4 are schematic diagrams of the operating frequency and the capacitive impedance of the capacitor and the operating frequency and the inductive impedance of the capacitor, respectively, in the embodiment of the invention. Referring first to FIG. 3, as the operating frequency of the capacitor increases, i.e., the operating frequency of the capacitor approaches the self-resonant frequency f _s In the course of (a), the capacitive impedance z of the capacitor ₁ Continuously decreasing. When the working frequency of the capacitor is equal to the self-resonant frequency f _s When this capacitance can be equivalent to a resistance. Further, in FIG. 4, the operating frequency of the capacitor exceeds the self-resonant frequency f _s Then, as the operating frequency of the capacitor increases, the inductive impedance of the capacitor increases, and the capacitor can be equivalently an inductor. Therefore, a capacitor with a self-resonant frequency matched with the harmonic frequency can be arranged on the capacitor module 2, and the capacitor is grounded, so that the capacitor module 2 can filter harmonic signals with different harmonic frequencies in the radio frequency signals. Therefore, the harmonic suppression can be effectively carried out on the radio frequency signals, the quality of the transmitted signals can be improved, and the filter circuit is simple and easy to realize and has higher applicability.

In this embodiment, in order to effectively perform harmonic suppression on the radio frequency signal, the present embodiment performs harmonic suppression on the radio frequency signal by using a capacitor module having a self-resonant frequency matched with the harmonic frequency, but the additional impedance generated by the capacitor module changes the output impedance of the radio frequency circuit. For this case, the present embodiment performs impedance transformation based on the additional impedance generated by the capacitor module 2 by the impedance matching circuit 3 to match the output impedance of the radio frequency circuit 300.

For example, the rf circuit 300 may be first connected to the filter 1 to detect the first output impedance of the rf circuit 300. The rf circuit 300 is then connected to the filter 1 through the capacitor module 2 to detect the second output impedance of the rf circuit 300. The additional impedance generated by the capacitor module 2 is the difference between the second output impedance and the first output impedance. And the impedance matching circuit 3 is correspondingly arranged according to the additional impedance generated by the capacitor module 2, so that the impedance matching circuit 3 performs impedance transformation based on the additional impedance generated by the capacitor module 2, and further transforms the output impedance of the radio frequency circuit 300 into a first output impedance to realize impedance matching.

Optionally, the impedance matching circuit 3 may be implemented by electronic components such as a capacitor, an inductor, a resistor, an adjustable capacitor, and an adjustable inductor.

In this embodiment, the capacitor module 2 may transmit the signal to be filtered after harmonic suppression to the filter 1 through the impedance matching circuit 3, and the filter 1 performs filtering processing on the signal to be filtered to obtain a transmission signal in a predetermined frequency range.

In the present embodiment, the Filter 1 may include a Band Pass Filter (BPF). A band-pass filter belongs to a device that allows a signal of a specific frequency band to pass therethrough while filtering signals of other frequency bands than the specific frequency band. For example, the band-pass filter includes a low-pass filter and a high-pass filter, and since the low-pass filter allows a signal lower than a certain cutoff frequency to pass therethrough and the high-pass filter allows a signal higher than a certain cutoff frequency to pass therethrough, the cutoff frequency of the low-pass filter may be set to a, and the cutoff frequency of the high-pass filter may be set to B, and the cutoff frequency a is greater than the cutoff frequency B, and the band-pass filter may filter a signal to be filtered to obtain a transmission signal in the frequency range of B to a.

Optionally, the band-pass filter is further configured to perform filtering processing and harmonic suppression on the signal to be filtered, so as to obtain a transmission signal in a predetermined frequency range. That is, the harmonic suppression is performed on the signal to be filtered again through the band-pass filter, so that the accuracy of the harmonic suppression is improved.

In this embodiment, the signal transmitting circuit 200 includes a radio frequency interface and an antenna. The radio frequency interface is coupled between the antenna and the filter 1 of the filter circuit 100, the filter 1 transmits the transmission signal to the antenna through the radio frequency interface, so that the antenna transmits the transmission signal to the receiving device in a wireless manner. Wherein the radio frequency interface is for example an antenna interface (Antenna hardware interface, ANT).

In the following description, the radio frequency interface, i.e., the antenna interface, in the signal transmission circuit 200 is taken as an example, and the radio frequency circuit 300 includes a bluetooth chip. Specifically, the equivalent circuit diagram of the filter circuit of the present embodiment may refer to fig. 5.

Fig. 5 is an equivalent circuit diagram of a filter circuit according to an embodiment of the present invention. As shown in fig. 5, the signal transmission circuit 200 includes an antenna interface ANT. The filter 1 includes a band-pass filter 11, and the band-pass filter 11 includes a first ground port GND1, a second ground port GND2, an input terminal IN, and an output terminal OUT. The impedance matching circuit 3 includes an inductor L and a first capacitor C ₁ And a second capacitor C ₂ . The capacitor module 2 includes a third capacitor C ₃ . The radio frequency circuit 300 includes a bluetooth chip 310. The bluetooth chip 310 includes an output terminal TRX (Transmit Receive X, transmit receive channel) and a third ground port GND3.

In the present embodiment, the first ground port GND1 and the second ground port GND2 of the band-pass filter 11 are commonly connected, that is, connected to the same ground, which can improve electromagnetic compatibility (Electromagnetic Compatibility, EMC) and can improve the performance of the band-pass filter 11.

IN the present embodiment, the inductor L is coupled between the input terminal IN of the band-pass filter 11 and the output terminal TRX of the bluetooth chip 310 IN the radio frequency circuit 300.

First capacitor C ₁ Coupled between the input IN of the band-pass filter 11 and ground.

Second capacitor C ₂ Coupled between the output terminal TRX of the Bluetooth chip 310 and the ground terminal in the RF circuit 300, wherein the first capacitor C ₁ Coupled to the ground and the second capacitor C ₂ The coupled ground terminals are different.

Third capacitor C ₃ An output terminal TRX of the Bluetooth chip 310 coupled to the RF circuit 300 and groundedBetween the ends, wherein a third capacitance C ₃ Coupled to the ground and the second capacitor C ₂ The coupled ground terminals are the same.

The output terminal TRX of the bluetooth chip 310 is coupled to the inductor L, and the third ground port GND3 is grounded.

In this embodiment, the resonant frequency of the radio frequency signal output by the bluetooth chip 310 may be detected in advance, and then the third capacitor C having the self-resonant frequency matched with the resonant frequency may be determined ₃ . It is easy to understand that if the bluetooth chip 310 outputs a radio frequency signal with different harmonic frequencies, a plurality of capacitors with the same number of harmonic frequencies may be disposed in the capacitor module 2, each capacitor having a self-resonant frequency matching each harmonic frequency. That is, a capacitor matched with the harmonic frequency of the harmonic signal generated by the radiation source (i.e. the element generating the harmonic signal, such as the bluetooth chip 310) is added to be grounded near the radiation source, and when the harmonic signal carried by the radio frequency signal passes through the link, the capacitor is equivalent to a resistor by utilizing the self-resonant frequency characteristic of the capacitor, so that the harmonic signal is conducted to the ground, thereby realizing effective harmonic suppression.

In the present embodiment, the third capacitor C ₃ Harmonic suppression is performed on the radio frequency signal output by the Bluetooth chip 310 to obtain a signal to be filtered, and a third capacitor C ₃ The signal to be filtered is sent to the input IN of the band-pass filter 11 through the impedance matching circuit 3. The band-pass filter 11 performs filtering processing on the signal to be filtered to obtain a transmission signal in a fixed frequency range, so that the transmission signal is transmitted to an antenna through an antenna interface ANT via an output end OUT, and the antenna transmits the transmission signal to receiving equipment. Wherein the impedance matching circuit 3 is used for matching the third capacitor C ₃ The generated additional impedance is impedance transformed to match the output impedance of the bluetooth chip 310.

For example, the Bluetooth chip 310 is a BT chip, and the third capacitor C ₃ The self-resonant frequency SRF of (i.e. megahertz) is 12134.75MHz, the third capacitance C ₃ Model GJM0225C1C1R0WB01, third capacitor C ₃ The capacitance value of (a) is 1pF (i.e., picofarad). The inductance value of the inductance L is, for example, 3nH (i.e., nanohenry), the first capacitance C ₁ Capacitance value of (2)A second capacitor C of 3pF ₂ The capacitance value of (2) is 3pF.

Optionally, in this embodiment, the impedance matching circuit 3 includes an inductance L and a first capacitance C ₁ And a second capacitor C ₂ An example is described. It will be appreciated that the impedance matching circuit 3 may also be implemented by an adjustable capacitance, an adjustable inductance, etc. Specifically, different harmonic frequencies corresponding to different harmonic signals may be predetermined, and a plurality of capacitors having the same number as the harmonic frequencies are disposed in the capacitor module 2, where each capacitor has a self-resonant frequency matched with the corresponding harmonic frequency. One end of each capacitor is connected to a corresponding radiation source (such as output terminal TRX of Bluetooth chip 310) of radio frequency circuit 300, and the other end of each capacitor is connected to a ground terminal (the ground terminal and second capacitor C) via a corresponding controlled switch (such as radio frequency switch) ₂ The same ground terminal). The controller can detect the harmonic frequency of the radio frequency signal provided by the radio frequency circuit 300 in real time, determine the matched self-resonant frequency according to the harmonic frequency detected in real time, and further determine the corresponding target capacitance from the plurality of capacitances in the capacitance module 2 according to the self-resonant frequency, so that it is easy to understand that the self-resonant frequency of the target capacitance is matched with the harmonic frequency. And then the controller controls the corresponding controlled switch of the target capacitor to be conducted, so that the target capacitor is conducted to be grounded through the corresponding controlled switch, and the radio frequency signal is accurately subjected to harmonic suppression through the target capacitor. The controller may also detect the output impedance of the radio frequency circuit 300 and adjust the capacitance value of the adjustable capacitance according to a predetermined generated additional impedance of the target capacitance and/or the inductance value of the adjustable inductance to perform an impedance transformation to match the output impedance of the radio frequency circuit 300. Therefore, the filter circuit of the embodiment can effectively inhibit harmonic signals caused by environmental factors, and has higher universality.

The foregoing description is only of the preferred embodiments of the present application and is not intended to limit the same, but rather, various modifications and variations may be made by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. that fall within the spirit and principles of the present application are intended to be included within the scope of the present application.

Claims (10)

1. A filter circuit, the filter circuit comprising:

the capacitor module is used for carrying out harmonic suppression on the radio frequency signal provided by the radio frequency circuit so as to obtain a signal to be filtered;

the filter is coupled with the capacitor module and is used for filtering the signal to be filtered so as to obtain a transmitting signal;

the capacitor module has a self-resonant frequency matched with the harmonic frequency of the radio frequency signal.

2. The filter circuit of claim 1, wherein the radio frequency signal has a different harmonic frequency, the capacitor module comprising a number of capacitors equal to the number of harmonic frequencies, each capacitor having a self-resonant frequency that matches each harmonic frequency.

3. The filter circuit of claim 1, wherein the filter circuit further comprises:

and the impedance matching circuit is coupled with the capacitor module and the filter and is used for carrying out impedance transformation based on the additional impedance generated by the capacitor module so as to match the output impedance of the radio frequency circuit.

4. A filter circuit according to claim 3, wherein the filter comprises:

and the band-pass filter is used for carrying out filtering processing on the signal to be filtered so as to obtain the transmitting signal in a preset frequency range.

5. The filter circuit of claim 4, wherein the impedance matching circuit comprises:

an inductor coupled between an input of the band pass filter and an output of the radio frequency circuit;

a first capacitor coupled between an input terminal of the band-pass filter and a ground terminal;

and the second capacitor is coupled between the output end of the radio frequency circuit and the ground end.

6. The filter circuit of claim 5, wherein the radio frequency circuit comprises:

and the Bluetooth chip is coupled with the inductor and is used for providing the radio frequency signal.

7. The filter circuit of claim 5 or 6, wherein the capacitor module comprises:

and the third capacitor is coupled between the output end of the radio frequency circuit and the ground end.

8. A wireless device, the wireless device comprising:

a radio frequency circuit for providing a radio frequency signal;

a filter circuit as claimed in any one of claims 1 to 7.

9. The wireless device of claim 8, wherein the wireless device further comprises:

and the signal sending circuit is coupled with the filtering circuit and is used for transmitting the transmitting signal provided by the filtering circuit to the receiving equipment.

10. The wireless device of claim 9, wherein the signal transmission circuit comprises:

a radio frequency interface coupled between the filter circuit and an antenna for transmitting the transmit signal to the antenna;

and an antenna for transmitting the transmission signal to the receiving device.