CN115955213A - Duplexer for improving out-of-band far-end multiple frequency suppression - Google Patents

Abstract

The invention discloses a duplexer for improving out-of-band far-end multi-frequency suppression, which can improve the out-of-band far-end suppression level of a transmitting filter, particularly the suppression level below minus 45dB at a frequency multiplication position of 3 times and achieve the suppression level below minus 30dB outside the whole high-end band while ensuring the isolation of the transmitting passband in a receiving passband by connecting a parallel branch in the transmitting filter with a suppression branch resonator in common without increasing the volume and connecting the parallel branch in common with the suppression branch resonator and the rest parallel arm resonators in common with the ground. In addition, the invention can increase the number of the heat dissipation grounding through holes when the signal passes through the parallel resonator by connecting one parallel branch in the transmitting filter with the restraining branch resonator in common and not with the rest grounding terminal of the transmitting filter in common, thereby obtaining higher power capacity.

Description

A duplexer for improving out-of-band remote multiplier rejection

technical field

The invention belongs to the technical field of surface acoustic wave filters, and in particular relates to the design of a duplexer for improving out-of-band and remote-end multi-frequency suppression.

Background technique

In the current wireless communication, the RF front-end is one of the most important module circuits. The filter in the RF front-end, especially the duplexer, is an important module in the front-end module. The duplexer is usually composed of two groups of band-pass filters with different frequencies. The device is composed of a transmit passband filter and a receive passband filter. In a radio frequency system, the performance of the transmit filter plays a pivotal role in the entire system. Improving its suppression level can not only greatly reduce signal interference, but also reduce the use of peripheral components. Therefore, the low passband insertion loss, high stopband rejection, and passband edge steepness of the transmit passband filter have become the main technical indicators for duplexer performance.

In the existing duplexer design, the transmit passband filter is a ladder structure filter. The ladder filter itself has the problem of large area occupancy, and it is necessary to introduce additional components to improve specific performance such as roll-off characteristics and insertion loss. More inductance, capacitance, coupling and other structures. How to ensure sufficient power capacity without increasing the filter area, and at the same time ensure the isolation of the filter in the transmit and receive frequency bands, and the suppression of the far-end multi-octave of the transmit filter to a certain level, is the researcher. Committed to the direction of research and urgent problems to be solved.

Contents of the invention

The purpose of the present invention is to propose a duplexer that enhances out-of-band remote multiplier suppression, without increasing the area of the transmit filter, ensuring that the suppression and isolation of the transmit passband filter in the receive passband are available In order to improve the suppression level at the multi-multiple frequency at the far end outside the band of the transmit filter, and at the same time ensure that the duplexer structure has sufficient power capacity.

The technical solution of the present invention is: a duplexer for improving out-of-band remote multi-frequency suppression, including a piezoelectric substrate, an antenna terminal arranged on the piezoelectric substrate, a transmitting filter terminal and a receiving filter terminal, and the antenna terminal A transmit filter is provided between the antenna terminal and the transmit filter terminal, and a receive filter is provided between the antenna terminal and the receive filter terminal.

Further, the receiving filter includes a series arm resonator S1, a fifth-order DMS filter and a series arm resonator S2 connected in series, one end of the series arm resonator S1 is connected to the antenna terminal, and the other end of the series arm resonator S1 is connected to the fifth-order DMS filter. A parallel arm resonator P1 is connected between the input ends, one end of the series arm resonator S2 is connected to the receiving filter terminal, and a parallel arm resonator P2 is connected between the other end and the output end of the fifth-order DMS filter, and the parallel arm resonant The resonator P1, the parallel arm resonator P2 and the fifth-order DMS filter are connected to the common ground through the first ground terminal.

Further, the transmit filter includes a series arm resonator S3, a series arm resonator S4, a series arm resonator S5, and a series arm resonator S6 connected in series, one end of the series arm resonator S3 is connected to the transmit filter terminal, and the series arm One end of the resonator S6 is connected to the antenna terminal, a parallel arm resonator P3 is connected between the series arm resonator S3 and the series arm resonator S4, and a parallel arm resonator P4 is connected between the series arm resonator S4 and the series arm resonator S5 , the parallel arm resonator P3 and the parallel arm resonator P4 are connected to the common ground through the second ground terminal, the parallel arm resonator P5 and the suppression branch are connected between the series arm resonator S5 and the series arm resonator S6, and the suppression branch includes The interconnected suppression branch parallel resonator P6 and the series inductor, the parallel arm resonator P5 and the suppression branch parallel resonator P6 are connected in parallel, and are connected to the common ground through the third ground terminal.

Further, the duplexer also includes a first ground terminal, a second ground terminal, a third ground terminal and a fourth ground terminal, the first ground terminal and the second ground terminal are connected together to form the first ground terminal, and the third ground terminal serves as The second ground terminal and the fourth ground terminal serve as the third ground terminal.

Further, the resonators in the transmitting filter and the receiving filter are surface acoustic wave resonators.

Further, the series resonant frequency formed by the equivalent capacitance and the series inductance of the parallel resonator P6 of the suppression branch is located at the edge of the passband of the receiving filter.

The beneficial effects of the present invention are:

(1) In the duplexer provided by the present invention, without increasing the volume, a parallel branch in the transmitting filter is connected to the common ground of the suppression branch resonator, and is not shared with the rest of the parallel arm resonators , while ensuring the isolation of the transmit filter in the receive passband, the out-of-band and far-end rejection level of the transmit filter can be improved, especially at the 3rd octave position, which can achieve a rejection below -45dB, and in the entire High-end out-of-band reaches rejection levels below -30dB.

(2) The present invention connects a parallel branch in the transmitting filter to the common ground of the suppressing branch resonator, and does not share the ground with the rest of the ground terminals of the transmitting filter, so that the heat dissipation can be increased when the signal passes through the parallel resonator The number of ground vias, thus resulting in higher power handling.

Description of drawings

FIG. 1 is a schematic structural diagram of a duplexer for improving out-of-band remote multi-frequency suppression provided by an embodiment of the present invention.

FIG. 2 is a circuit diagram of a duplexer for improving out-of-band remote multiplier suppression provided by an embodiment of the present invention.

FIG. 3 is a schematic structural diagram of a duplexer provided in a comparative example of the present invention.

FIG. 4 is a circuit diagram of a duplexer provided in a comparative example of the present invention.

FIG. 5 is a schematic diagram showing the comparison of the far-end rejection curves of the transmit filter of the embodiment of the present invention and the comparative example.

FIG. 6 is a schematic diagram showing a comparison of near-end S-parameter curves of an embodiment of the present invention and a comparative example.

FIG. 7 is a schematic diagram showing a comparison of loss amplification between the embodiment of the present invention and the comparative example.

Description of reference signs: 1-antenna terminal, 2-transmission filter terminal, 3-reception filter terminal, 4-first ground terminal, 5-second ground terminal, 6-third ground terminal, 7-fourth ground terminals.

Detailed ways

Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the implementations shown and described in the drawings are only exemplary, intended to explain the principle and spirit of the present invention, rather than limit the scope of the present invention.

Example:

An embodiment of the present invention provides a duplexer that enhances out-of-band remote multiple frequency suppression, as shown in Figure 1 and Figure 2, including a piezoelectric substrate, an antenna terminal 1 disposed on the piezoelectric substrate, a transmission filter The transmitter terminal 2 and the receiving filter terminal 3, the transmitting filter is arranged between the antenna terminal 1 and the transmitting filter terminal 2, and the receiving filter is arranged between the antenna terminal 1 and the receiving filter terminal 3.

In the embodiment of the present invention, the receiving filter includes a series arm resonator S1, a fifth-order DMS filter, and a series arm resonator S2 connected in series. One end of the series arm resonator S1 is connected to the antenna terminal 1, and the other end of the series arm resonator S1 is connected to the fifth-order DMS filter. A parallel arm resonator P1 is connected between the input ends of the DMS filter, one end of the series arm resonator S2 is connected to the receiving filter terminal 3, and a parallel arm resonator is connected between the other end and the output end of the fifth-order DMS filter P2, the parallel arm resonator P1, the parallel arm resonator P2 and the fifth-order DMS filter are commonly connected through the first ground terminal.

In the embodiment of the present invention, the transmit filter includes a series arm resonator S3, a series arm resonator S4, a series arm resonator S5, and a series arm resonator S6 connected in series, and one end of the series arm resonator S3 is connected to the transmit filter terminal 2. One end of the series arm resonator S6 is connected to the antenna terminal 1, a parallel arm resonator P3 is connected between the series arm resonator S3 and the series arm resonator S4, and a parallel arm resonator P3 is connected between the series arm resonator S4 and the series arm resonator S5. The parallel arm resonator P4, the parallel arm resonator P3 and the parallel arm resonator P4 are commonly connected through the second ground terminal, and the parallel arm resonator P5 and the suppression branch are connected between the series arm resonator S5 and the series arm resonator S6 , the suppression branch includes interconnected suppression branch parallel resonators P6 and series inductors (not shown in the figure), the parallel arm resonator P5 and the suppression branch parallel resonator P6 are connected in parallel, and are connected to the common ground through the third ground terminal , so that the signal can pass through the third ground terminal to increase heat dissipation and ensure sufficient power capacity.

In the embodiment of the present invention, the duplexer further includes a first ground terminal 4, a second ground terminal 5, a third ground terminal 6, and a fourth ground terminal 7, and the first ground terminal 4 and the second ground terminal 5 are connected in common to form a second One ground terminal, the third ground terminal 6 serves as the second ground terminal, and the fourth ground terminal 7 serves as the third ground terminal. The ground terminal of the transmitting filter and the ground terminal of the receiving filter are not connected on the piezoelectric substrate, that is, the first ground terminal 4 and the second ground terminal 5 are connected in common, and the third ground terminal 6 and the fourth ground terminal 7 are separately grounded. The isolation of the duplexer can maintain good performance.

In the embodiment of the present invention, the resonators in the transmit filter and the receive filter are surface acoustic wave resonators.

In the embodiment of the present invention, the series resonant frequency formed by the equivalent capacitance and the series inductance of the parallel resonator P6 of the suppression branch is located at the edge of the passband of the receiving filter.

Comparative example:

In order to further illustrate the performance and effect of a duplexer that improves out-of-band remote multi-frequency suppression provided by the embodiment of the present invention, a comparative example is now used for comparison and description. As shown in Figure 3 and Figure 4, in the comparative example, the structure of the receiving filter is exactly the same as in the embodiment, and the suppressing branch parallel resonator P6 in the transmitting filter is arranged between the series arm resonator S4 and the series arm resonator S5 Between, and in parallel with the parallel arm resonator P4, and the suppression branch parallel resonator P6 is grounded separately, the parallel arm resonator P3, the parallel arm resonator P4 and the parallel arm resonator P5 are connected to the common ground, and all the parallel arm resonators are connected to On the same ground, when the signal passes through, it is likely to cause heat accumulation, resulting in deterioration of device performance, that is, relatively low power capacity.

FIG. 5 is a schematic diagram showing the comparison of the far-end rejection curves of the transmission filter of the embodiment of the present invention and the comparative example, wherein the solid line is the embodiment, and the dotted line is the comparative example. It can be seen that outside the entire transmit filter band, the suppression level of the embodiment is below -30dB, especially at the triple frequency place, the suppression degree reaches -45dB, while the far-end suppression linearity in the comparative example deteriorates, only at the triple frequency place There is a suppression level of -20dB, and it reaches a suppression level of -10dB at 3GHz, which will bring users an unsatisfactory performance experience.

This is because the three parallel arm resonators of the transmit filter in the comparative example are connected to the common ground, which is equivalent to three capacitors connected in parallel. After parallel connection, the total capacitance value is the sum of each parallel capacitor, C=C _P3 +C _P4 +C _P5 , according to the calculation formula f=1/(2π√LC) of the resonant frequency of the LC circuit, the larger C is, the smaller the resonant frequency f is, which corresponds to the 1.0GHz recessed position of the dotted line in Figure 5. However, in the embodiment, the parallel arm resonator P5 and the suppression branch parallel resonator P6 are connected to the common ground, and are not shared with the rest of the parallel arm resonators, then the capacitance of the LC circuit is C=C _P3 +C _P4 , so the corresponding The resonant frequency f becomes larger, corresponding to the 1.8GHz notch on the graph.

FIG. 6 is a schematic diagram showing the comparison of the near-end S parameter curves of the transmission filter of the embodiment of the present invention and the comparison example, wherein the solid line is the embodiment, and the dotted line is the comparison example. It can be seen that the suppression degree of the embodiment and the comparative example is at a level close to 60dB in the receiving passband, and because the suppression branch parallel resonator P6 is introduced, the deep zero point of the product at the edge of the receiving passband at 746MHz can be reached, reaching ideal suppression. At the same time, outside the low frequency band of the transmission passband, the suppression level of the embodiment is -30dB, and the suppression level of the comparative example is only -20dB.

FIG. 7 is a schematic diagram showing the comparison of loss amplification between the embodiment of the present invention and the comparative example, wherein the solid line is the embodiment, and the dotted line is the comparative example. It can be seen that the embodiment has more margin at the low frequency of the transmission passband than the comparative example.

Those skilled in the art will appreciate that the embodiments described here are to help readers understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical revelations disclosed in the present invention without departing from the essence of the present invention, and these modifications and combinations are still within the protection scope of the present invention.

Claims (6)

1. A duplexer that promotes out-of-band remote multiple-frequency suppression, is characterized in that it comprises a piezoelectric substrate, an antenna terminal (1) that is arranged on the piezoelectric substrate, a transmit filter terminal (2) and A receiving filter terminal (3), a transmitting filter is arranged between the antenna terminal (1) and the transmitting filter terminal (2), and a transmitting filter is arranged between the antenna terminal (1) and the receiving filter terminal (3). receive filter. 2. The duplexer for boosting out-of-band remote multiple-frequency suppression according to claim 1, wherein the receiving filter comprises a series arm resonator S1, a fifth-order DMS filter and a series connection in series Arm resonator S2, one end of the series arm resonator S1 is connected to the antenna terminal (1), and a parallel arm resonator P1 is connected between the other end and the input end of the fifth-order DMS filter, and the series arm resonator S2 One end of is connected to the receiving filter terminal (3), and a parallel arm resonator P2 is connected between the other end and the output end of the fifth-order DMS filter, the parallel arm resonator P1, the parallel arm resonator P2 and the fifth-order DMS The filter is connected to the common ground through the first ground terminal. 3. The duplexer for boosting out-of-band remote multiple-frequency suppression according to claim 2, wherein the transmit filter comprises series-arm resonators S3, series-arm resonators S4, series-connected Arm resonator S5 and series arm resonator S6, one end of the series arm resonator S3 is connected to the transmit filter terminal (2), one end of the series arm resonator S6 is connected to the antenna terminal (1), and the series arm resonant A parallel arm resonator P3 is connected between the series arm resonator S3 and the series arm resonator S4, a parallel arm resonator P4 is connected between the series arm resonator S4 and the series arm resonator S5, and the parallel arm resonator P3 and the parallel arm resonator The arm resonator P4 is connected to the common ground through the second ground terminal, the parallel arm resonator P5 and the suppression branch are connected between the series arm resonator S5 and the series arm resonator S6, and the suppression branch includes interconnected suppression The branch parallel resonator P6 and the series inductor, the parallel arm resonator P5 and the suppression branch parallel resonator P6 are connected in parallel, and are connected to the common ground through the third ground terminal. 4. The duplexer for boosting out-of-band remote multiple frequency multiplication suppression according to claim 3, wherein the duplexer also includes a first ground terminal (4), a second ground terminal (5), The third ground terminal (6) and the fourth ground terminal (7), the first ground terminal (4) and the second ground terminal (5) are jointly connected to form a first ground terminal, and the third ground terminal (6) As the second ground terminal, the fourth ground terminal (7) serves as the third ground terminal. 5. The duplexer for improving out-of-band remote multi-frequency suppression according to claim 3, wherein the resonators in the transmitting filter and the receiving filter are both surface acoustic wave resonators. 6. The duplexer for boosting out-of-band remote multi-frequency suppression according to claim 3, wherein the series resonant frequency formed by the equivalent capacitance and series inductance of the suppression branch parallel resonator P6 is located at the position of the edge of the passband of the receive filter.

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