WO2020125341A1

WO2020125341A1 - Filter unit having coupling inductor, filter, and electronic device

Info

Publication number: WO2020125341A1
Application number: PCT/CN2019/120978
Authority: WO
Inventors: 庞慰; 蔡华林
Original assignee: 天津大学; 诺思(天津)微系统有限责任公司
Priority date: 2018-12-18
Filing date: 2019-11-26
Publication date: 2020-06-25
Also published as: CN111342789B; CN111342789A

Abstract

The present invention relates to an LC filter unit, comprising: a first filtering part comprising a first inductor and a first capacitive device that are connected in parallel; and a second filtering part comprising a second inductor and a second capacitive device that are connected in parallel, wherein the first inductor and the second inductor are suitable for coupling to form a coupling inductor; the first capacitive device and the second capacitive device may be a resonator; an Fs frequency of the resonator is outside of a passband of the filter unit, and an Fp frequency of the resonator falls within the passband; and the resonator may be an FBAR resonator. The present invention further relates to a filter having the filter unit, and an electronic device having the filter unit or the filter.

Description

Filter unit with coupling inductor, filter and electronic equipment

Technical field

Embodiments of the present invention relate to the semiconductor field, and in particular, to a filter unit, a filter with the filter unit, and an electronic device with the filter or the filter unit.

Background technique

With the popularization of the Internet of Things, smart devices and 5G communication, the demand for high-speed transmission is becoming increasingly urgent. There is a direct correspondence between the communication rate and the channel bandwidth. Increasing the communication channel bandwidth is the most direct and effective way to increase the transmission rate. Therefore, the broadband system occupies a very important position in the next-generation communication system. The bandwidth and transmission performance of the communication channel depends on the selection of a specific communication bandwidth by the radio frequency front end, especially the radio frequency filter. Therefore, the broadband high-performance filter has become a bottleneck for implementing a broadband system.

Since the piezoelectric filter has a small piezoelectric coupling coefficient, and the piezoelectric coupling coefficient directly corresponds to the bandwidth, it is difficult for such a filter to realize a high-bandwidth filter.

The LC filter can achieve a larger bandwidth, but due to the limitation of the quality factor, the performance gap is larger than that of the piezoelectric filter. In addition, for the LC filter, because multiple passive devices are implemented on the substrate, and high bandwidth requires larger inductance, the filter size is greatly increased and the cost is increased; and the coupling between the devices will make the filter performance deterioration.

Summary of the invention

In order to alleviate or solve at least one aspect of using the above problems in the prior art, the present invention is proposed.

According to an aspect of an embodiment of the present invention, an LC filter unit is proposed, including: a first filter section including a first inductor and a first capacitive device connected in parallel; and a second filter section including a parallel connection The second inductor and the second capacitive device, wherein: the first inductor and the second inductor are suitable for coupling to form a coupled inductor.

Optionally, the first inductance and the second inductance are coupled to each other in a manner of cross-winding in the same layer or in two-layer winding. Further, the filter unit is provided on the LTCC substrate.

Optionally, the first inductance and the second inductance realize coupling mutual inductance in a mutual inductance manner of discrete devices.

Optionally, a third capacitive device is connected between the same end of the first inductor and the second inductor. Further, the third capacitive device is a third resonator.

Optionally, the first capacitive device and the second capacitive device are a capacitor, a series or parallel resonance form of a capacitor and an inductor, or a resonator.

Optionally, the first capacitive device and the second capacitive device are parallel capacitors, and each filter section further includes a parallel resonator connected in parallel with the parallel capacitor, and the Fs frequency of the parallel resonator is in the filter unit Outside the pass band of the parallel resonator, and the Fp frequency of the parallel resonator falls within the pass band; or the first capacitive device and the second capacitive device are parallel resonators, and the Fs frequency of the parallel resonator Outside the pass band of the filter unit, and the Fp frequency of the parallel resonator falls within the pass band.

Optionally, the first capacitive device and the second capacitive device are parallel capacitors, and each filter section further includes a parallel resonator connected in parallel with the parallel capacitor, and a series connected in parallel with the parallel capacitor connected in parallel and the parallel resonator A resonator, and the Fs frequency of the series resonator is within the passband of the filter unit, and the Fp frequency of the series resonator is outside the passband of the filter unit; or the first capacitive device and The second capacitive device is a parallel resonator, and each filter section further includes a series resonator connected in series with the parallel resonator and the corresponding inductor in parallel, and the Fs frequency of the series resonator is within the pass band of the filter unit And the Fp frequency of the series resonator is outside the pass band of the filter unit. Further, at least two of the series resonator and the parallel resonator have different resonance frequencies from each other.

Optionally, each filter section further includes a series capacitor connected in parallel with the parallel capacitor and the parallel resonator. Further, the capacitance values of at least two capacitors in the series capacitor and the parallel capacitor are different from each other.

Optionally, the first capacitive device and the second capacitive device are resonators.

Optionally, the Fs frequency of the resonator is outside the pass band of the filter unit, and the Fp frequency of the resonator falls within the pass band.

Optionally, the resonator is an FBAR resonator, a SAW resonator or a BAW resonator.

Optionally, in all the filter units described above, one end of the first inductor and the first capacitive device is grounded; and both ends of the second inductor form a differential signal, or one end of the second inductor and the second capacitive device is grounded.

Embodiments of the present invention also relate to a filter, including the filter unit described above.

Embodiments of the present invention also relate to an electronic device, including the aforementioned filter or the aforementioned filter unit.

BRIEF DESCRIPTION

The following description and drawings can better help to understand these and other features and advantages in the various embodiments disclosed in the present invention. The same reference numerals in the figures always denote the same parts, among which:

FIG. 1 is a schematic structural diagram of a filter unit in the prior art;

2a is a schematic diagram of a filter unit according to an exemplary embodiment of the present invention, and FIG. 2b is an equivalent circuit diagram of the filter unit in FIG. 2a;

3 is a schematic diagram of a filter unit according to an exemplary embodiment of the present invention;

4 is a schematic diagram of a filter unit according to an exemplary embodiment of the present invention;

5 is a schematic diagram of a filter unit according to an exemplary embodiment of the present invention;

6 is a schematic diagram of a filter unit according to an exemplary embodiment of the present invention;

7 is a schematic diagram of a filter unit according to an exemplary embodiment of the present invention;

8 is a schematic diagram of a filter unit according to an exemplary embodiment of the present invention;

9 is a schematic diagram of inductive coupling according to an exemplary embodiment of the present invention;

10a is a schematic top view of an inductive coupling according to an exemplary embodiment of the present invention, and FIG. 10b is a schematic perspective view corresponding to FIG. 10a;

11 is a schematic diagram of inductive coupling according to an exemplary embodiment of the present invention;

12 is a schematic diagram of a filter according to an exemplary embodiment of the present invention;

FIG. 13 exemplarily shows simulation results of a filter using the filter unit in FIG. 8 in which high bandwidth is realized;

FIG. 14 exemplarily shows simulation results of a filter using the filter unit in FIG. 3, in which high bandwidth and high roll-off are achieved;

15 is a schematic diagram illustrating the introduction of the resonator to improve roll-off and out-of-band suppression; and

Figures 16a, 16b, and 16c respectively show schematic diagrams of packaging using an LTCC substrate to implement an LC filter, a discrete component to implement an LC filter, and an IPD to implement an LC filter.

detailed description

The technical solutions of the present invention will be further specifically described below through the embodiments and the accompanying drawings. In the description, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the drawings is intended to explain the general inventive concept of the present invention, and should not be construed as a limitation of the present invention.

FIG. 2a is a schematic diagram of a filter unit according to an exemplary embodiment of the present invention. As shown in Figure 2a, the two inductors L1 and L2 are coupled to each other, and the capacitors C1 and C2 and the resonators R1 and R2 are connected in parallel. Figure 2a is used as the basic unit of a filter to design a high-bandwidth filter.

Passive LC components can be implemented as discrete components, see for example Figure 16b, where the resonator is packaged as a separate die.

The implementation form of passive LC components can be IPD, as shown in Figure 16c, where the resonator is packaged as a separate die.

Passive LC components can be implemented in LTCC or organic packaging substrates, as shown in Figure 16a, where the LTCC substrate is used to implement LC, and the resonator is packaged together as a separate die.

The realization form of passive LC components can also be realized by PCB. For example, the resonator may be connected to the substrate or the PCB board by wire bonding or Flipchip.

In the present invention, the resonator may be in the form of FBAR, SAW, BAW or other resonators.

FIG. 2b is an equivalent circuit diagram of the filter unit in FIG. 2a. In Figure 2b:

LL1=[(L1-M)*(L2-M)+(L2-M)*M+(L1-M)*M]/(L2-M),

LL2=[(L1-M)*(L2-M)+(L2-M)*M+(L1-M)*M]/(L1-M),

LM=[(L1-M)*(L2-M)+(L2-M)*M+(L1-M)*M]/M.

Based on the above, it can be known that when L1=L2, LL1=L1+M and LL2=L2+M.

Therefore, when M is positively coupled, the inductance value of LL1 is greater than the original L1. At this time, the effect of L1+M can be obtained by using the inductance value of L1, so the winding size of the inductor can be reduced.

On the other hand, as the size of the inductor is larger, the self-resonant frequency is lower, and when the self-resonant frequency is approached, the inductance value fluctuates violently and the performance deteriorates, so it is desirable to avoid the self-resonant frequency close to the passband region of the filter, which limits The bandwidth of the filter. The use of a smaller inductor can greatly extend the self-resonant frequency relative to the passband of the filter, helping to achieve higher bandwidth.

Although the above description of achieving high bandwidth is based on the embodiments of FIGS. 2a and 2b, the technical effects of obtaining high bandwidth can also be applied to other embodiments of the present invention, such as the embodiments of FIGS. 3-8.

Although FIG. 13 exemplarily shows the simulation results of the filter using the filter unit in FIG. 8, in which a high bandwidth is achieved, but since FIG. 8 is the same as in FIG. 2a, both use inductive coupling, which The technical effect can also be applied to other embodiments based on the present invention in the present invention.

FIG. 3 is a schematic diagram of a filter unit according to an exemplary embodiment of the present invention. In Fig. 2a, the resonance of the inductance and the capacitance generates resonance points in and out of the band. The resonator itself is a capacitor. The capacitor can also be removed according to the bandwidth and suppression of the filter, and the structure of Fig. 3 is adopted. Specifically, The difference between Fig. 3 and Fig. 2a is that the capacitors C1 and C2 in Fig. 2a are removed.

FIG. 4 is a schematic diagram of a filter unit according to an exemplary embodiment of the present invention, and is also a modified embodiment of FIG. 2a. As shown in Figure 4, the filter unit also adds series resonators R3 and R4. Although not shown, the capacitors C1 and C2 in FIG. 4 can also be removed.

FIG. 5 is a schematic diagram of a filter unit according to an exemplary embodiment of the present invention, and is also a modified embodiment of FIG. 2a. As shown in Figure 5, the filter unit also adds series capacitors C3 and C4. In addition, a capacitor C5 is added in FIG. 5. Each of the capacitors C1-C5 can be replaced with a series or parallel resonance form of a capacitor inductance or a resonator. When the capacitor C5 is replaced with a resonator, in addition to the capacitance effect of the resonator, an additional resonance frequency point can be generated at the frequencies Fs and Fp of the resonator, which can be used to improve suppression or roll-off.

FIG. 6 is a schematic diagram of a filter unit according to an exemplary embodiment of the present invention, and is also a modified embodiment of FIG. 2a. As shown in FIG. 6, the frequencies of the resonators R1 and R2 may be different.

7 is a schematic diagram of a filter unit according to an exemplary embodiment of the present invention, and is also a modified embodiment of FIG. 2a. In Figure 2a, it is single-ended to single-ended. In Figure 7, it is from single-ended to differential. As shown in Figure 7, the middle of the inductor L2 is a virtual ground, and the signal is coupled through mutual inductance. The upper and lower ends of the inductor L2 form a differential signal to achieve a single-ended to differential conversion. As can be understood, the structure in FIG. 7 can also reversely convert from differential to single-ended.

FIG. 8 is a schematic diagram of a filter unit according to an exemplary embodiment of the present invention, which is a modified embodiment of FIG. 3. As shown in FIG. 8, the resonator in FIG. 3 is replaced with a capacitor. FIG. 13 is a schematic diagram of the simulation results of the filter using the structure in FIG. 8 in which a high bandwidth of 4.7 GHz is realized.

The following illustrates by way of example the coupling of the inductors L1 and L2.

9 is a schematic diagram of inductive coupling according to an exemplary embodiment of the present invention. As shown in FIG. 9, the two inductors (solid and dashed lines are two coupled inductors, the solid line corresponds to, for example, the inductor L1 in FIG. 2a, and the dotted line corresponds to the inductor L2 in FIG. 2a), the two inductors occupy only one inductor area . In addition, through the use of coupled inductance, additional mutual inductance is generated, and at the same time as one of the components of the filter, the number of originals is further reduced.

By adjusting the spacing of the traces, the coupling coefficient can be adjusted to ensure the design requirements.

For example, as shown in Figures 16a, 16b, and 16c, this structure can be implemented by IPD, LTCC, or other substrates and PCBs. By winding on the same layer, the two coils are coupled to each other to achieve mutual inductance. The size of the coupling coefficient is adjusted by adjusting the distance between the two coils of the solid line and the dotted line.

FIG. 10a is a schematic top view of an inductive coupling according to an exemplary embodiment of the present invention, and FIG. 10b is a schematic perspective view corresponding to FIG. 10a.

In FIGS. 10a and 10b, two inductors (solid lines and dashed lines are two coupling inductances, solid lines correspond to, for example, inductance L1 in FIG. 2a, and dashed lines correspond to, for example, inductance L2 in FIG. 2a). Similarly, as shown in Figs. 16a, 16b, and 16c, the inductance corresponding to the solid line and the inductance corresponding to the dashed line can be realized by IPD, LTCC, or other substrates and PCBs. They are located on the upper and lower layers of the three-dimensional structure, with the dielectric layer in the middle. To realize the mutual inductance structure in the filter. The mutual inductance can be adjusted by the thickness of the upper and lower layers.

11 is a schematic diagram of inductive coupling according to an exemplary embodiment of the present invention. In Fig. 11, the coupled inductance is realized by mutual inductance of discrete devices.

12 is a schematic diagram of a filter according to an exemplary embodiment of the present invention, which shows that the filter uses a filter unit. As shown in FIG. 12, the filter also includes the necessary matching circuit, and the mutual inductance M1, M2 and coupling capacitance of the components between the various filter units.

In the present invention, the use of inductive coupling reduces the use of passive devices, and the use of coupling can reduce the limitation of the distance of passive devices. At the same time, the inductance used is small, so the size of the device is greatly reduced. Helps achieve high bandwidth.

Furthermore, in the present invention, by replacing the capacitance in the LC filter in the prior art by using a resonator, especially an FBAR resonator, or by adding a resonator, especially FBAR, in parallel with the capacitance in the LC filter in the prior art In the case of resonators, when the Fs frequency of the resonator is outside the pass band and the Fp frequency falls within the pass band of the filter unit, the filter can improve the roll-off of the pass band while obtaining a high bandwidth.

FIG. 14 exemplarily shows simulation results of a filter using the filter unit in FIG. 3, in which high bandwidth and high roll-off are realized.

In Figure 3, a resonator is used to replace the capacitor in the existing LC filter. As shown in Fig. 14, a transmission zero is formed on the left side of the passband, and a faster roll-off is formed in the range of 100MHz. Because the resonator is equivalent to a capacitor other than Fs and Fp, a small impedance at the Fs frequency, and a large impedance at the Fp frequency point, using a resonator parallel structure, at the Fs frequency, most of the signal from resonance The transmitter is flowing away, so there is less transmission signal, and there is greater suppression of the signal of Fs. Therefore, setting this frequency outside the band of the filter can greatly improve the out-of-band suppression performance; for the frequency of Fp, because the impedance is very high Therefore, most of the frequency of Fp is transmitted through the filter. Therefore, setting Fp within the band of the filter will not affect the insertion loss. And the Q value of the resonator is higher, and the conversion from Fs to Fp is faster, so better roll-off characteristics can be achieved.

By adjusting the frequency of the resonator, the transmission zero point and the position of out-of-band suppression can be set to ensure that the required frequency point can be better suppressed.

Similarly, the introduction of resonators on the right side of the passband can also improve roll-off and suppression. In Fig. 14, the 10GHz position on the right side of the passband is the zero pole generated by the resonator's high-order resonance frequency. By controlling the resonator's high-order frequency, it is possible to ensure sufficient suppression of specific frequencies at high frequencies.

It should be noted that, in the present invention, the single resonator shown in the drawings may be an actual resonator or an equivalent resonator composed of multiple resonators electrically connected; similarly, in In the present invention, the single capacitor shown in the drawings may be an actual capacitor or an equivalent capacitor formed by the equivalent of one or more devices; similarly, a single inductor may also be an equivalent inductance. These are all within the protection scope of the present invention.

FIG. 15 is a schematic diagram illustrating the introduction of resonators to improve roll-off and out-of-band suppression. The frequency of the resonator is high, and the impedance of the resonator has a rapid change from low to high near the resonance frequency. When used in parallel, the high impedance has little effect on the in-band, and the low impedance forms the zero point of signal transmission. Because the impedance changes quickly, the transmission curve has a faster roll-off. Through series and parallel connection of multiple frequency resonators, an out-of-band stop band with a certain bandwidth can be formed. In addition to the position of Fs and Fp, the resonator acts as a capacitor, which is similar to the ordinary capacitor, but at the frequency of Fs and Fp, there will be changes in high and low impedance. Therefore, this change can improve out-of-band suppression and roll-off characteristic. In the above figure, 3GHz and 10GHz are realized by using the impedance characteristics of the resonator's series resonance frequency Fs and parallel resonance frequency Fp.

Embodiments of the present invention also relate to an electronic device, including the above-mentioned filter unit or filter. It should be noted that the electronic devices here include but are not limited to intermediate products such as radio frequency front-ends, filter amplification modules, and terminal products such as mobile phones, WIFI, and drones.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that these embodiments can be changed without departing from the principle and spirit of the present invention. The appended claims and their equivalents are limited.

Claims

An LC filter unit, including:

A first filter unit, including a first inductor and a first capacitive device connected in parallel; and

The second filter unit includes a second inductor and a second capacitive device connected in parallel,

among them:

The first inductor and the second inductor are suitable for coupling to form a coupled inductor.
The filter unit according to claim 1, wherein:

The first inductance and the second inductance realize coupling mutual inductance in the manner of cross-winding in the same layer or in two-layer winding.
The filter unit according to claim 2, wherein:

The filter unit is provided on the LTCC substrate.
The filter unit according to claim 1, wherein:

The first inductance and the second inductance realize coupling mutual inductance in a mutual inductance manner of discrete devices.
The filter unit according to claim 1, wherein:

A third capacitive device is connected between the same end of the first inductor and the second inductor.
The filter unit according to claim 5, wherein:

The third capacitive device is a third resonator.
The filter unit according to any one of claims 1 to 4, wherein:

The first capacitive device and the second capacitive device are capacitors, a series or parallel resonance form of a capacitor and an inductor, or a resonator.
The filter unit according to claim 7, wherein:

The first capacitive device and the second capacitive device are parallel capacitors, and each filter section further includes a parallel resonator connected in parallel with the parallel capacitor. The Fs frequency of the parallel resonator is within the pass band of the filter unit And the Fp frequency of the parallel resonator falls within the passband; or

The first capacitive device and the second capacitive device are parallel resonators, the Fs frequency of the parallel resonator is outside the pass band of the filter unit, and the Fp frequency of the parallel resonator falls into the pass In-band.
The filter unit according to claim 8, wherein:

The first capacitive device and the second capacitive device are parallel capacitors, and each filter section further includes a parallel resonator connected in parallel with the parallel capacitor and a series resonator connected in series with the parallel parallel capacitor and parallel resonator, and The Fs frequency of the series resonator is within the passband of the filter unit, and the Fp frequency of the series resonator is outside the passband of the filter unit; or

The first capacitive device and the second capacitive device are parallel resonators, each filter section further includes a series resonator connected in series with the parallel parallel resonator and a corresponding inductor, and the Fs frequency of the series resonator Is within the pass band of the filter unit, and the Fp frequency of the series resonator is outside the pass band of the filter unit.
The filter unit according to claim 9, wherein:

The resonance frequencies of at least two of the series resonator and the parallel resonator are different from each other.
The filter unit according to claim 8, wherein:

Each filter section also includes a series capacitor connected in parallel with the parallel capacitor and the parallel resonator.
The filter unit according to claim 11, wherein:

The capacitance values of at least two of the series capacitance and the parallel capacitance are different from each other.
The filter unit according to claim 7, wherein:

The first capacitive device and the second capacitive device are resonators; and

The Fs frequency of the resonator is outside the pass band of the filter unit, and the Fp frequency of the resonator falls within the pass band.
The filter unit according to claim 13, wherein:

The resonator is an FBAR resonator.
The filter unit according to claim 13, wherein:

The resonator is a SAW resonator or a BAW resonator.
The filter unit according to claim 1, wherein:

One end of the first inductor and the first capacitive device is grounded; and

The two ends of the second inductor form a differential signal, or the second inductor and one end of the second capacitive device are grounded.
A filter comprising the filter unit according to any one of claims 1-16.
An electronic device comprising the filter according to claim 17 or the filter unit according to any one of claims 1-16.