A low-pass filter with reconfigurable bandwidth

Abstract

The present invention discloses a bandwidth-reconfigurable low-pass filter, comprising: a resonant circuit, a control circuit, and a filter circuit; wherein the resonant circuit and the control circuit constitute a magnetically coupled resonator; the magnetically coupled resonator is used to generate a tunable zero point to change the passband of the filter; the filter circuit changes its passband based on the tunable zero point generated by the magnetically coupled resonator, with the passband range specifically determined by the tunable zero point; by changing the control voltage of the control circuit to change the tunable zero point, the passband width of the low-pass filter is changed, thereby achieving reconfiguration of the low-pass filter. The present invention utilizes the resonant circuit and the control circuit to form a magnetically coupled resonator. Simply by changing the control voltage introduced by the magnetically coupled resonator, the passband width of the filter can be changed, and the filter has a large reconfiguration range; the magnetically coupled resonator achieves bandwidth reconfiguration using only a small layout area.

Description

Technical Field

[0001] The present invention belongs to the field of integrated circuits, and in particular relates to a low-pass filter with reconfigurable bandwidth. Background Art

[0002] With the rapid development of the information industry and wireless communication systems, the RF front-end requires sufficient dynamic range to operate normally in multiple frequency bands. In different usage scenarios, filter modules are required to select different frequency bands, so filters with strong reconfiguration capabilities are more popular. Traditional reconfigurable solutions, such as integrating broadband active devices and narrowband passive devices, mostly adopt a multi-channel parallel structure, and achieve reconfiguration by selecting components through switches. The disadvantages of this solution are very obvious. The entire module involves many devices, and most scenarios only require a single frequency band for communication, which can easily lead to waste of hardware resources and increased costs. Therefore, reconfigurable, low-cost, and miniaturized devices are becoming increasingly popular and are one of the key technologies in the current field of RF reconfiguration.

[0003] Public patent 202211703631.0, entitled "Transmission zero point tunable filter based on through silicon via technology", proposes a three-stacked filter with high integration, good out-of-band suppression characteristics and in-passband characteristics, but it cannot achieve continuous adjustment of the transmission zero point.

[0004] Pingyue Song and other researchers published a paper titled "RF filter synthesis based on passively coupled N-path resonators" in the IEEE Journal of Solid-State Circuits. The paper proposes an N-channel filter that avoids charge sharing by introducing spiral inductors, achieving a wide frequency range and improving frequency selectivity. However, the filter involves numerous modules, making miniaturization difficult. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a low-pass filter with reconfigurable bandwidth. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0006] The present invention provides a low-pass filter with reconfigurable bandwidth, comprising:

[0007] Resonant circuit, control circuit and filter circuit; wherein,

[0008] The resonant circuit and the control circuit constitute a magnetic coupling resonator;

[0009] The magnetically coupled resonator is used to generate a tunable zero point;

[0010] The filter circuit determines its own passband width based on the tunable zero point, and combines with the magnetic coupling resonator to filter the input signal and output the filtered signal;

[0011] The tunable zero point is changed by changing the control voltage of the control circuit, so that the passband width of the low-pass filter is changed, thereby achieving bandwidth reconstruction of the low-pass filter.

[0012] In one embodiment of the present invention, the resonant circuit includes:

[0013] Inductor L1 and capacitor C1; where,

[0014] The first end of the inductor L1 is connected to the input end of the filter circuit, and the second end is connected to the first end of the capacitor C1;

[0015] The capacitor C1 is grounded via a second terminal.

[0016] In one embodiment of the present invention, the control circuit includes:

[0017] Inductor L2, control power supply V C , resistor R L2 and resistor R S2 ;in,

[0018] The first end of the inductor L2 is connected to the control power supply V C The first end is connected to the resistor R L2 The first end of the connection;

[0019] The control power supply V C The second end of the resistor R S2 The first end of the connection;

[0020] The resistor R L2 The second end of is grounded;

[0021] The resistor R S2 The second end is grounded.

[0022] In one embodiment of the present invention, the inductor L1 and the inductor L2 are coupled to each other to form a tunable inductor.

[0023] In one embodiment of the present invention, changing the control voltage of the control circuit to change the tunable zero point includes:

[0024] By changing the control power supply V C The control voltage is changed to change the voltage ratio β between the control power supply and the power supply, thereby changing the current in the inductor L2, so that the current coupled into the inductor L1 changes, thereby changing the tunable zero point.

[0025] In one embodiment of the present invention, the control power supply V C The frequency is the same as the frequency of the input signal.

[0026] In one embodiment of the present invention, a filter circuit includes:

[0027] Inductor L3, capacitor C2, capacitor C3 and capacitor C4; wherein,

[0028] The first end of the inductor L3 is connected to the first end of the capacitor C2, and the second end is connected to the first end of the capacitor C4;

[0029] The first end of the capacitor C2 serves as the input end of the filter circuit, and the second end is grounded;

[0030] The first end of the capacitor C3 is connected to the first end of the inductor L3, and the second end is connected to the second end of the inductor L3;

[0031] The first end of the capacitor C4 serves as the output end of the filter circuit, and the second end is grounded.

[0032] In one embodiment of the present invention, the bandwidth reconfigurable low-pass filter is formed by cascading the magnetic coupling resonator and the filter circuit.

[0033] Beneficial effects of the present invention:

[0034] In the solution provided by the present invention, a magnetically coupled resonator is formed by utilizing a resonant circuit and a control circuit. The passband width of the low-pass filter can be changed by simply changing the control voltage introduced by the magnetically coupled resonator, and the solution has a large reconfiguration range. The magnetically coupled resonator realizes a reconfigurable function using only a small layout area. Furthermore, since only passive components are used, the parasitic resistance of the components is small, the loss generated to the signal is low, and the stopband is suppressed by two zero points outside the broadband, thereby having a good out-of-band suppression effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic structural diagram of a bandwidth-reconfigurable low-pass filter provided by an embodiment of the present invention;

[0036] Figure 2 A schematic structural diagram of a magnetic coupling resonator provided by an embodiment of the present invention;

[0037] Figure 3 A schematic diagram of the change of the scattering parameter S21 corresponding to different voltages in a control circuit of a bandwidth reconfigurable low-pass filter provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0039] The embodiment of the present invention provides a low-pass filter with reconfigurable bandwidth, such as Figure 1 As shown, this may include:

[0040] Resonant circuit, control circuit and filter circuit; wherein,

[0041] The resonant circuit and the control circuit constitute a magnetic coupling resonator;

[0042] a magnetically coupled resonator for generating a tunable zero;

[0043] The filter circuit determines its own passband width based on the tunable zero point, combines with the magnetic coupling resonator, filters the input signal, and outputs the filtered signal;

[0044] The control voltage of the control circuit is changed to change the tunable zero point, thereby changing the passband width of the low-pass filter, thereby achieving bandwidth reconstruction of the low-pass filter.

[0045] The bandwidth-reconfigurable low-pass filter provided in an embodiment of the present invention utilizes a resonant circuit and a control circuit to form a magnetically coupled resonator, cascades the magnetically coupled resonator with the filter circuit, and realizes the change of the tunable zero point of the magnetically coupled resonator through magnetic coupling technology, further realizes the change of the tunable zero point inserted into the passband of the low-pass filter, and ultimately realizes the change of the passband, thereby achieving good filtering effect while also having good out-of-band suppression.

[0046] To facilitate understanding, various modules of the bandwidth reconfigurable low-pass filter provided by the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0047] Resonant circuit

[0048] Resonant circuits, such as Figure 1 As shown, this may include:

[0049] Inductor L1 and capacitor C1; where,

[0050] A first end of the inductor L1 is connected to the input end of the filter circuit, and a second end is connected to the first end of the capacitor C1;

[0051] The capacitor C1 is grounded via a second terminal.

[0052] It can be understood that the resonant circuit is composed of an inductor L1 and a capacitor C1 connected in series, and the resonant circuit is connected in parallel to the filter circuit.

[0053] Control circuit

[0054] Control circuits, such as Figure 1As shown, this may include:

[0055] Inductor L2, control power supply V C , resistor R L2 and resistor R S2 ;in,

[0056] The first end of the inductor L2 is connected to the control power supply V C The first end is connected to the resistor R L2 The first end of the connection;

[0057] Control power supply V C The second end of the resistor R S2 The first end of the connection;

[0058] Resistor R L2 The second end of is grounded;

[0059] Resistor R S2 The second end is grounded.

[0060] It can be understood that the control circuit includes an inductor L2 and a control power supply V C The structure composed of series connections and the corresponding resistors connected to each other.

[0061] Control power supply V C The frequency is the same as the input signal frequency.

[0062] Inductor L1 and inductor L2 are coupled to each other to form a tunable inductor. The resonant circuit and the control circuit form a magnetically coupled resonator. For a schematic diagram of the structure of the magnetically coupled resonator, see Figure 2 As shown. The magnetic coupling resonator can change the passband width of the filter by generating a zero point through resonance. The control power supply V of the control circuit in the magnetic coupling resonator can be changed by changing C The corresponding voltage changes the resonant frequency.

[0063] It can be understood that in the resonant circuit, the inductor L1 and the capacitor C1 are connected in series to form a series resonant circuit. When no coupling is introduced, a fixed zero point will be generated. After the control loop is introduced, the equivalent inductance value of the inductor L1 changes due to the magnetic coupling effect, thereby changing the inductance value of the capacitor C1 that generates resonance, and further causing the zero point generated by the resonance to change accordingly.

[0064] Specifically, changing the control voltage of the control circuit to change the tunable zero point may include:

[0065] By changing the control power supply V C The control voltage changes the voltage ratio β between the control power supply and the power supply, changes the current in the inductor L2, and causes the current coupled into the inductor L1 to change, thereby changing the tunable zero point.

[0066] When the control power supply V C When the control voltage changes, the current in the inductor L2 changes, causing the current coupled into the inductor L1 to change, which changes the intensity of the magnetic coupling effect, changes the equivalent inductance, and ultimately causes a corresponding change in the resonance point.

[0067] As can be understood, the low-pass filter proposed in the embodiment of the present invention requires only one tunable inductor, significantly reducing circuit area and improving integration compared to traditional low-pass filters. The magnetic coupling technology enables rapid and precise inductance adjustment, improving the accuracy and speed of bandwidth adjustment. Furthermore, the tunable inductor based on magnetic coupling has a large tuning range, enabling the reconfigurable low-pass filter to achieve wide-range bandwidth reconfiguration. While traditional reconfigurable low-pass filters are affected by their own varactor diodes and active modules, making it difficult to achieve high operating frequencies, the reconfigurable low-pass filter proposed in the embodiment of the present invention utilizes a tuning method based on the magnetic coupling effect, enabling higher operating frequencies.

[0068] filter circuit

[0069] Preferably, the filter circuit, such as Figure 1 As shown, this may include:

[0070] Inductor L3, capacitor C2, capacitor C3 and capacitor C4; wherein,

[0071] A first end of the inductor L3 is connected to a first end of the capacitor C2, and a second end of the inductor L3 is connected to a first end of the capacitor C4;

[0072] The first end of the capacitor C2 serves as the input end of the filter circuit, and the second end is grounded;

[0073] A first end of the capacitor C3 is connected to a first end of the inductor L3, and a second end of the capacitor C3 is connected to a second end of the inductor L3;

[0074] A first end of the capacitor C4 serves as an output end of the filter circuit, and a second end thereof is grounded.

[0075] The bandwidth reconfigurable low-pass filter is composed of a magnetically coupled resonator and a cascaded filter circuit.

[0076] It is understood that the input end of the filter circuit is connected to the output end of the resonant circuit. The filter circuit filters the preliminary processed signal based on the tunable zero point generated by the magnetic coupling resonator and outputs the filtered signal. By changing the control voltage of the control circuit to change the tunable zero point generated by the magnetic coupling resonator, the bandwidth of the low-pass filter is changed, thereby achieving reconstruction of the low-pass filter. The specific filter circuit can be any filter circuit that can achieve filtering processing, and the structure proposed in the embodiment of the present invention should not be understood as a limitation on the filter circuit.

[0077] It can be understood that the low-pass filter is composed of a magnetic coupling resonator and a filter circuit cascade. This structure allows the zero point generated by the magnetic coupling resonator to be introduced into the filter circuit by changing the control power supply V in the control circuit. C The corresponding control voltage realizes the tunability of the zero point, and finally realizes the change of the passband. The low-pass filter provided by the embodiment of the present invention has the advantages of flat passband, good transition band characteristics, and a narrower transition band.

[0078] from Figure 1 As can be seen from the figure, the specific connection structure of the bandwidth reconfigurable low-pass filter proposed in the embodiment of the present invention includes, from left to right, an input end, a resonant circuit, a control circuit, a filter circuit, and an output end; wherein,

[0079] The input terminal is connected in series with the grounded resistor R S1 and input signal source V S constitute;

[0080] The resonant circuit is composed of an inductor L1 and a capacitor C1 connected in series, wherein the capacitor C1 is grounded;

[0081] The control circuit consists of resistors R connected in series L2 , inductor L2, control power supply V C and resistor R S2 Composition; Among them, the inductor L2 is grounded, the resistor R S2 grounding;

[0082] The filter circuit is composed of a capacitor C2, an inductor L3 and a capacitor C3, and a capacitor C4 connected in parallel; wherein the capacitor C2 is grounded, and the capacitor C4 is grounded;

[0083] The output terminal is connected to the ground by a resistor R L1 constitute.

[0084] It is understandable that in order to avoid the magnetic coupling effect from introducing noise and deteriorating the filtering effect, it is considered to directly cascade the resonant circuit and the output end, and to choose to use a filter circuit to separate the two.

[0085] In order to effectively demonstrate the beneficial effects of the bandwidth reconfigurable low-pass filter proposed in the embodiment of the present invention, experiments are conducted on the scattering parameter S21 of the control circuit of the bandwidth reconfigurable low-pass filter at different voltages.

[0086] Specifically, for the control circuit of the bandwidth reconfigurable low-pass filter, the corresponding change diagram of the scattering parameter S21 under different voltages is shown in FIG. Figure 3 , V C Indicates the voltage amplitude corresponding to the control voltage, Freq indicates the frequency, Figure 3 It can be seen that ω Z Indicates the tunable zero point. The scattering parameter S21 below -3dB can be considered as the filtered signal, and the scattering parameter S21 above -3dB can be considered as the effective signal. Under the voltage, the range of the filtered signal will also change accordingly, and the position of the tunable zero point will also change with the change of voltage, from Figure 3 The changes in the tunable zero point and bandwidth can be clearly seen in FIG, which directly proves the effectiveness of the bandwidth reconfigurable low-pass filter proposed in the embodiment of the present invention.

[0087] The bandwidth-reconfigurable low-pass filter proposed in an embodiment of the present invention utilizes a resonant circuit and a control circuit to form a magnetically coupled resonator. The bandwidth of the filter can be changed simply by changing the control voltage introduced by the magnetically coupled resonator, and has a large reconfiguration range. The magnetically coupled resonator achieves the reconfiguration function using only a small layout area. Furthermore, since only passive components are used, the device parasitic resistance is small, the loss to the signal is low, and the two zero points suppress the stopband outside the broadband, thereby having a good out-of-band suppression effect.

[0088] It should be noted that, in the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A bandwidth reconfigurable low-pass filter, characterized in that: include: Resonant circuit, control circuit and filter circuit; wherein, The resonant circuit and the control circuit constitute a magnetic coupling resonator; The magnetically coupled resonator is used to generate a tunable zero point; The filter circuit determines its own passband width based on the tunable zero point, and combines with the magnetic coupling resonator to filter the input signal and output the filtered signal; The tunable zero point is changed by changing the control voltage of the control circuit, so that the passband width of the low-pass filter is changed, thereby achieving bandwidth reconstruction of the low-pass filter.

2. The bandwidth reconfigurable low-pass filter according to claim 1, characterized in that: The resonant circuit comprises: Inductor L1 and capacitor C1; where, The first end of the inductor L1 is connected to the input end of the filter circuit, and the second end is connected to the first end of the capacitor C1; The capacitor C1 is grounded via a second terminal.

3. The bandwidth reconfigurable low-pass filter according to claim 2, characterized in that: The control circuit comprises: Inductor L2, control power supply V C , resistor R L2 and resistor R S2 ;in, The first end of the inductor L2 is connected to the control power supply V C The first end is connected to the resistor R L2 The first end of the connection; The control power supply V C The second end of the resistor R S2 The first end of the connection; The resistor R L2 The second end of is grounded; The resistor R S2 The second end is grounded.

4. The bandwidth reconfigurable low-pass filter according to claim 3, characterized in that: The inductor L1 and the inductor L2 are coupled to each other to form a tunable inductor.

5. The bandwidth reconfigurable low-pass filter according to claim 3, characterized in that: Changing the control voltage of the control circuit to change the tunable zero point includes: By changing the control power supply V C The control voltage is changed to change the voltage ratio β between the control power supply and the power supply, thereby changing the current in the inductor L2, so that the current coupled into the inductor L1 changes, thereby changing the tunable zero point.

6. The bandwidth reconfigurable low-pass filter according to claim 3, characterized in that: The control power supply V C The frequency is the same as the frequency of the input signal.

7. The bandwidth reconfigurable low-pass filter according to claim 1, characterized in that: The filter circuit comprises: Inductor L3, capacitor C2, capacitor C3 and capacitor C4; wherein, The first end of the inductor L3 is connected to the first end of the capacitor C2, and the second end is connected to the first end of the capacitor C4; The first end of the capacitor C2 serves as the input end of the filter circuit, and the second end is grounded; The first end of the capacitor C3 is connected to the first end of the inductor L3, and the second end is connected to the second end of the inductor L3; The first end of the capacitor C4 serves as the output end of the filter circuit, and the second end is grounded.

8. The bandwidth reconfigurable low-pass filter according to claim 1, characterized in that: The bandwidth reconfigurable low-pass filter is composed of the magnetic coupling resonator and the filter circuit in cascade connection.

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