Low-pass filter with reconfigurable bandwidth

Abstract

The invention discloses a low-pass filter with reconfigurable bandwidth. The low-pass filter comprises a resonance circuit, a control circuit and a filter circuit, wherein the resonance circuit and the control circuit form a magnetic coupling resonator; the magnetic coupling resonator is used for generating a passband of the tunable zero change filter; according to the filter circuit, a passband is changed based on a tunable zero point generated by a magnetic coupling resonator, and specifically, the passband range is determined by the tunable zero point; 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, and the reconstruction of the low-pass filter is realized. The resonant circuit and the control circuit are utilized to form the magnetic coupling resonator, the passband width of the filter can be changed only by changing the control voltage introduced by the magnetic coupling resonator, and a large reconstruction range is achieved; according to the magnetic coupling resonator, the bandwidth reconstruction function can be realized only by using a small layout area.

Description

Technical Field

[0001] The 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 needs sufficient dynamic range to work properly in multiple frequency bands. In different usage scenarios, the filter module is required to select different frequency bands, so filters with strong reconfigurable capabilities are more popular. Traditional reconfigurable solutions such as integrated broadband active devices and narrowband passive devices mostly adopt a multi-channel parallel structure, and reconfiguration is achieved 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 more and more popular and are one of the key technologies in the current RF reconfigurable field.

[0003] The patent 202211703631.0, with the patent name "Transmission zero point adjustable filter based on through silicon via technology", proposes a three-digit stacked filter with high integration and 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 proposed an N-channel filter that avoids charge sharing by introducing spiral inductors, which not only achieves wide range variation but also improves frequency selectivity. However, it involves many modules and is difficult to miniaturize. 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 by the following technical solution:

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

[0007] A resonant circuit, a control circuit and a 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, performs filtering processing on the input signal in combination with the magnetic coupling resonator, and outputs the filtered signal;

[0011] The control voltage of the control circuit is changed to change the tunable zero point, 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 comprises:

[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 comprises:

[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 A first end is connected;

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

[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, the tunable zero point is changed by changing the control voltage of the control circuit, comprising:

[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, and the current in the inductor L2 is changed, so that the current coupled into the inductor L1 changes, so as to change 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 comprises:

[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 of the inductor L3 is connected to the first end of the capacitor C4;

[0029] The first end of the capacitor C2 is used 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 of the capacitor C3 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, a bandwidth reconfigurable low-pass filter is formed by cascading the magnetically coupled resonator and the filter circuit.

[0033] Beneficial effects of the present invention:

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

[0035] Figure 1 A schematic diagram of the structure 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 changes in a 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 is further described in detail below with reference to specific embodiments, 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] A resonant circuit, a control circuit and a 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, so that the passband width of the low-pass filter is changed, thereby realizing the bandwidth reconstruction of the low-pass filter.

[0045] The bandwidth reconfigurable low-pass filter provided in the embodiment of the present invention utilizes a resonant circuit and a control circuit to form a magnetically coupled resonator, cascades the magnetically coupled resonator and 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 finally realizes the change of the passband, while achieving good filtering effect and good out-of-band suppression.

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

[0047] Resonance 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 an input end of the filter circuit, and a second end of the inductor L1 is connected to a 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 A first end is connected;

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

[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 formed by series connection and the corresponding resistors connected to each other.

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

[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 magnetic coupling resonator. For a structural diagram of the magnetic coupling 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 achieves a change in 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, which in turn causes a corresponding change in the zero point generated by the resonance.

[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 strength of the magnetic coupling effect, changes the equivalent inductance, and ultimately causes a corresponding change in the resonance point.

[0067] It can be understood that the low-pass filter proposed in the embodiment of the present invention only needs one tunable inductor, which significantly reduces the circuit area and improves the integration compared with the traditional low-pass filter; the magnetic coupling technology is used to achieve fast and accurate inductance value adjustment, which improves the accuracy and speed of bandwidth adjustment; and the tunable inductor based on magnetic coupling has the characteristics of a large tuning range, so that the reconfigurable low-pass filter can achieve wide-range bandwidth reconstruction. Since the traditional reconfigurable low-pass filter is affected by its own varactor diode and active module, it is difficult to achieve a high operating frequency, and the reconfigurable low-pass filter proposed in the embodiment of the present invention adopts a tuning method based on the magnetic coupling effect, which can achieve a higher operating frequency.

[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 is used 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 can be understood that the input end of the filter circuit is connected to the output end of the resonant circuit, and the filter circuit performs filtering processing on 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 realizing the reconstruction of the low-pass filter. The specific filter circuit can be any filter circuit that can realize 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 It can be seen that 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 end consists of a series 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 Inductor L2 is grounded, 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 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 with the output end, but to choose to use a filter circuit to separate the two.

[0085] In order to 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 in the bandwidth reconfigurable low-pass filter at different voltages.

[0086] Specifically, for the control circuit of the bandwidth reconfigurable low-pass filter, the schematic diagram of the change of the scattering parameter S21 corresponding to different voltages can be seen in 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 the 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 the 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 by only changing the control voltage introduced by the magnetically coupled resonator, and has a large reconstruction range. The magnetically coupled resonator realizes the reconstruction function using only a small layout area. Furthermore, since only passive components are used, the parasitic resistance of the device is small, the loss generated to the signal is low, and the stopband is suppressed by two zero points outside the broadband, which has 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 only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

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

Claims

1. A bandwidth reconfigurable low-pass filter, characterized in that: include: A resonant circuit, a control circuit and a 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, combines with the magnetic coupling resonator, filters the input signal, and outputs the filtered signal; The control voltage of the control circuit is changed to change the tunable zero point, so that the passband width of the low-pass filter is changed, thereby achieving bandwidth reconstruction of the low-pass filter.

2. A 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. A 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 A first end is connected; The control power supply V C The second end of the resistor R S2 A first end is connected; The resistor R L2 The second end of is grounded; The resistor R S2 The second end is grounded.

4. A 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: The step of changing the tunable zero point by changing the control voltage of the control circuit comprises: 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, and the current in the inductor L2 is changed, so that the current coupled into the inductor L1 changes, so as to change 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 of the inductor L3 is connected to the first end of the capacitor C4; The first end of the capacitor C2 is used 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 of the capacitor C3 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 formed by cascading the magnetic coupling resonator and the filter circuit.

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