CN115149967A

CN115149967A - Cellular communication system filter and local area network signal extractor and communication device

Info

Publication number: CN115149967A
Application number: CN202110342136.0A
Authority: CN
Inventors: 蔡华林
Original assignee: ROFS Microsystem Tianjin Co Ltd
Current assignee: ROFS Microsystem Tianjin Co Ltd
Priority date: 2021-03-30
Filing date: 2021-03-30
Publication date: 2022-10-04
Anticipated expiration: 2041-03-30
Also published as: CN115149967B

Abstract

The invention discloses a cellular communication system (CELL) filter, a local area network signal extractor and a communication device. The filter has an antenna end and an output end, and includes first to fourth inductors and first to fourth resonators, wherein: the first inductor, the first resonator, the second resonator and the second inductor are sequentially connected in series between the antenna end and the output end; the first ends of the third resonator, the third inductor and the fourth resonator are positioned between the first resonator and the second resonator, and the second ends of the third resonator, the third inductor and the fourth resonator are grounded through the fourth inductor or the second ends of the third resonator, the third inductor and the fourth resonator are grounded through the inductors respectively. By adopting the technical scheme of the invention, the insertion loss of the low-frequency and high-frequency bands of the CELL filter and the inhibition of the CELL filter on the WiFi band are facilitated to be improved, and in addition, the insertion loss of the WiFi filter is also improved to a certain extent.

Description

Cellular communication system filter and local area network signal extractor and communication device

Technical Field

The present invention relates to the field of filter technology, and in particular, to a cellular communication system filter, a local area network signal extractor, and a communication device.

Background

In the WiFi extractor, the CELL filter is used for filtering interference signals of a WiFi frequency band (2402-2482 MHz), inhibiting the interference signals as high as possible and simultaneously having lower insertion loss on signals of other frequency bands. In a communication system, the lowest frequency is generally as low as 699MHz, and with the rapid development of 5G communication, signals in a 3400-3600MHz frequency band need to be compatible, so that signals in the frequency band also need to have insertion loss as low as possible. Under the condition of WiFi inhibition as high as possible, the filter is required to have wider bandwidth (699-3600 MHz) and ensure better insertion loss performance. Fig. 1 is a schematic diagram of the structure of a WiFi extractor relevant to the present invention. As shown in fig. 1, the WiFi extractor includes two filters, one is a CELL filter, and the other is a WiFi filter, one end of the two filters is connected to the antenna ANT, and the other end is respectively a respective port CELL _ OUT and a port WiFi _ OUT.

The signal frequency band passed by the WiFi filter is 2402MHz-2482MHz, and signals of other frequency bands are filtered. Signals passing through the CELL frequency band are signals except 2402MHz-2482MHz in the 699MHz-3600MHz frequency band. The CELL filter is used for inhibiting WiFi signals as much as possible, and the smaller the insertion loss of a WiFi frequency band is, the better the insertion loss of the WiFi frequency band is; the WiFi filter has the function that the insertion loss of the WiFi frequency band is smaller, the insertion loss is better, and signals of other frequency bands are restrained as much as possible. As shown in fig. 2A and 2B, fig. 2A and 2B are a graph illustrating a CELL filter and a WiFi filter in the prior art, respectively.

The existing extractor structure is difficult to be compatible with the lowest frequency and the highest frequency under the condition of meeting WiFi frequency band suppression, the 3.6GHz insertion loss is poor under the condition of meeting the insertion loss of 699MHz, and the 699MHz insertion loss is poor under the condition of meeting the insertion loss of 3600 MHz. Meanwhile, the impedance mismatch of a frequency point close to the CELL filter and WiFi is serious, and the insertion loss is poor at 2378MHz (which is a B40 frequency band) and 2496MHz (which is a B41 frequency band). The insertion loss deterioration of each frequency point deteriorates the signal-to-noise ratio of the signal, and for reducing the signal transmission rate and increasing the system power consumption, the insertion loss of the frequency point needs to be improved.

Disclosure of Invention

In view of the above, the present invention provides a filter and a local area network signal extractor for a cellular communication system and a communication device, so as to solve the above problems in the prior art. The invention provides the following technical scheme:

a cellular communication system (CELL) filter having an antenna end and an output end, the CELL filter comprising first to fourth inductors and first to fourth resonators, wherein: the first inductor, the first resonator, the second resonator and the second inductor are sequentially connected in series between the antenna end and the output end; the first ends of the third resonator, the third inductor and the fourth resonator are positioned between the first resonator and the second resonator, and the second ends of the third resonator, the third inductor and the fourth resonator are grounded through the fourth inductor or the second ends of the third resonator, the third inductor and the fourth resonator are grounded through the inductors respectively.

Optionally, a fifth inductor is further included, and a first end of the fifth inductor is connected to the first end of the third inductor, and a second end of the fifth inductor is connected to the first end of the third or fourth resonator.

Optionally, one or more of the first to fourth resonators further have an inductance connected in parallel across them.

Optionally, the resonator further comprises a fifth resonator and a sixth inductor, the fifth resonator has a first end connected to a connection point of the second resonator and the second inductor or to a connection point of the first resonator and the second resonator, and a second end grounded via the sixth inductor.

Optionally, an inductor is connected in parallel across the second resonator.

Optionally, the first inductance is between 3nH and 4.5nH, the second inductance is between 1.5nH and 5nH, and the third inductance is between 7nH and 20 nH; or the first inductance is between 3.2nH and 4nH, the second inductance is between 2nH and 4nH, and the third inductance is between 8.5nH and 15nH.

Optionally, the frequencies of the first resonator and the second resonator are less than the frequencies of the third resonator and the fourth resonator.

Optionally, a frequency difference between the first resonator and the second resonator is greater than 60MHz; the frequency difference of the third resonator and the fourth resonator is between 5MHz and 25MHz, or between 10MHz and 20 MHz.

Optionally, the resonator is an acoustic wave resonator.

A local area network signal extractor comprises a band-pass filter used for extracting local area network signals, and the local area network signal extractor also comprises a CELL filter.

A communication device comprising a CELL filter according to the invention or comprising a local area network signal extractor according to claim 10.

According to the technical scheme of the invention, a new extractor topological structure is adopted, and the insertion loss of the CELL filter in low-frequency and high-frequency bands is improved by setting inductance values, resonator frequency and the like, the inhibition of the CELL filter on a WiFi frequency band is improved, and the insertion loss of the WiFi filter is also improved. In addition, the electromechanical coupling coefficient of the resonator in the CELL filter can be set to be larger than that of the resonator in the WiFi filter, for example, the former is (1,1.5) times larger than that of the latter, which is beneficial to improving the insertion loss of adjacent frequency points with the WiFi.

Drawings

For purposes of illustration and not limitation, the present invention will now be described in accordance with its preferred embodiments, particularly with reference to the accompanying drawings, in which:

fig. 1 is a schematic diagram of the structure of a WiFi extractor relevant to the present invention;

FIGS. 2A and 2B are a graph of a CELL filter and a WiFi filter, respectively, according to the prior art;

FIG. 3 is a schematic diagram of a circuit of a CELL filter according to an embodiment of the present invention;

FIGS. 4A-4C are schematic diagrams of circuits of three CELL filters according to embodiments of the present invention;

FIGS. 5A and 5B are schematic diagrams of the circuitry of two CELL filters according to embodiments of the present invention;

FIGS. 6A and 6B are schematic and partially enlarged views of the insertion loss variation at high frequency of the corresponding CELL filter when the inductance L1 is greater than 4nH, respectively, according to the embodiment of the present invention;

fig. 6C is a schematic diagram of the variation of the corresponding insertion loss of the WiFi filter when the inductance L1 is less than 3.2nH according to the embodiment of the present invention;

FIG. 7A is a schematic diagram showing a partial enlargement of the variation of the insertion loss at high frequency of the corresponding CELL filter when the inductance L2 is greater than and less than 1.5nH according to the embodiment of the present invention;

FIG. 7B is a diagram illustrating the variation of the insertion loss of the frequency band of the corresponding CELL filter near the WiFi filter when the inductance L2 is greater than 5nH according to the embodiment of the present invention;

FIG. 8A is a diagram illustrating the variation of insertion loss at low frequency of a corresponding CELL filter when L3 is greater than and less than 7nH, according to an embodiment of the present invention;

FIG. 8B is a schematic diagram of a partial enlargement of the variation of the insertion loss at low frequency of the corresponding CELL filter when L3 is greater than 20nH according to the embodiment of the present invention;

FIG. 9 is a schematic diagram of a CELL filter WiFi band and corresponding resonant impedance in accordance with an embodiment of the present invention;

fig. 10A and 10B are schematic diagrams of frequency difference settings of resonator Res3 and resonator Res4, respectively, versus WiFi rejection variation in a CELL filter according to an embodiment of the present invention.

Detailed Description

In the embodiment of the invention, a new WiFi extractor (comprising a CELL band elimination filter and a WiFi band-pass filter) topological structure is provided, and better extractor performance is obtained by setting parameters such as inductance, resonator frequency, resonator electromechanical coupling coefficient and the like. The embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 3 is a schematic diagram of a circuit of a CELL filter according to an embodiment of the present invention. As shown in fig. 3, the main components of the CELL filter are shown in the dashed box, including inductors L1 to L4 and resonators Res1 to Res4. The inductor L1 is connected with an antenna terminal ANT, and the inductor L2 is connected with a port CELL _ OUT of the CELL filter. The resonators in embodiments of the present invention may be acoustic wave resonators, including bulk acoustic wave resonators and surface acoustic wave resonators. The connection point of the resonators Res1 and Res2 is also connected to the resonators Res3 and Res4 and the first end of the inductor L3, and the second ends of the three are grounded through the inductor L4.

The three inductors L1, L2 and L3 are mainly used for improving the insertion loss of the low-frequency end and the high-frequency end of the CELL filter. With respect to the reasonable range of inductance of the three, L1 is preferably greater than 3nH and less than 4.5nH, L2 is preferably greater than 1.5nH and less than 5nH, L3 is preferably greater than 7nH and less than 20nH, more preferably, L1 is greater than 3.2nH and less than 4nH, L2 is greater than 2nH and less than 4nH, and L3 is greater than 8.5nH and less than 15nH. The frequency of the resonators Res1 and Res2 is less than the frequency of the resonators Res3 and Res4 and the frequency difference of the resonators Res1 and Res2 is greater than 60MHz, the frequency difference of the resonators Res3 and Res4 is between 5MHz-25MHz, preferably between 10MHz-20 MHz.

Fig. 4A to 4C are schematic diagrams of circuits of three CELL filters according to an embodiment of the present invention. Compared with fig. 3, an inductance L5 is added in fig. 4A to 4C, and the inductance L5 may be specifically located between the resonator Res3 and the first end of the inductance L3 (as shown in fig. 4A), may be located between the resonator Res4 and the first end of the inductance L3 (as shown in fig. 4B), or may be connected in parallel with the resonator Res2 (as shown in fig. 4C).

Fig. 5A and 5B are schematic diagrams of the circuitry of two CELL filters according to embodiments of the present invention. As shown in fig. 5A, the main difference from fig. 3 is that resonators Res3 and Res4 are grounded via inductances La and Lb, respectively. The structure shown in fig. 5B is obtained by adding a resonator Res5 and an inductor Lc connected in series to the structure shown in fig. 5A, the resonator Res5 being connected to a connection point between the inductor L2 and the resonator Res2, and the inductor Lc being grounded. The resonator Res5 may also be connected to the junction of the resonators Res1 and Res2 and grounded via an inductance Lc.

The performance and structure of the WiFi extractor in the embodiment of the present invention will be further explained by taking the structure shown in fig. 3 as an example. Fig. 6A and 6B are a schematic diagram and a partially enlarged view of the insertion loss variation at high frequency of the corresponding CELL filter when the inductance L1 is greater than 4nH according to the embodiment of the present invention, respectively. Fig. 6C is a schematic diagram of the variation of the insertion loss of the WiFi filter when the inductance L1 is less than 3.2nH according to the embodiment of the present invention. In the graphs of fig. 6A to 6C, the thick line corresponds to an L1 sensitivity value of 3.2 to 4nH, and the thin line corresponds to an L1 sensitivity value of 3.2 to 4 nH. When the inductance value of L1 is less than 3.2nH, the insertion loss at the left side of the passband of the corresponding WiFi filter is greatly deteriorated, and when the inductance value of L1 is more than 4nH, the insertion loss at the high frequency position of the corresponding CELL filter is greatly deteriorated.

Fig. 7A is a schematic diagram of a partial enlargement of the variation of the insertion loss at high frequency of the corresponding CELL filter when the inductance L2 is greater than and less than 1.5nH, according to an embodiment of the present invention. In the graph of fig. 7A, the solid line corresponds to the case where the L2 inductance is greater than 1.5nH, and the dashed line corresponds to the case where the L2 inductance is less than 1.5nH, and it can be seen that L2 is preferably greater than 1.5nH, which contributes to obtaining better high-frequency insertion loss performance.

Fig. 7B is a schematic diagram illustrating a variation of the insertion loss of the corresponding CELL filter near the WiFi filter frequency band when the inductance L2 is greater than 5nH according to an embodiment of the present invention. It can be seen from the figure that when L2 is too large, the insertion loss will deteriorate, and the two curves in the figure, in which the thin line is located below the thick line, correspond to the case of deterioration, and the thick line corresponds to the case where L2 is within the aforementioned reasonable range.

Fig. 8A is a schematic diagram of the variation of the insertion loss at low frequencies of the corresponding CELL filter when L3 is greater than and less than 7nH, according to an embodiment of the present invention. The graph is a partially enlarged curve, wherein a thick line corresponds to the case that the L3 inductance is greater than 7nH, and a thin line corresponds to the case that the L3 inductance is less than 7nH, and it can be seen from the graph that L3 needs to be greater than 7nH to ensure good low-frequency insertion loss.

Fig. 8B is a schematic diagram of a local enlargement of the variation of the insertion loss at low frequency of the corresponding CELL filter when L3 is greater than 20nH according to the embodiment of the present invention. It can be seen that when L3 is too large, the insertion loss is deteriorated, and the thin curve corresponds to the deterioration, and the thick curve corresponds to the case where L3 is within the above reasonable range.

FIG. 9 is a schematic diagram of a CELL filter WiFi band and corresponding resonant impedance in accordance with an embodiment of the present invention. In the graph shown in fig. 9, the thick solid line 6 is a CELL filter, and it can be seen that there is a certain suppression in the WiFi frequency band (2402-2482 MHz). The thin line 1 and the thin line 2, i.e. the impedance peaks at 2.4GHz and 2.482GHz are the impedance curves of Res2 and Res1, respectively, and the thin line 3 and the thin line 4, i.e. the impedance peaks at 2.5GHz and 2.515GHz are the impedance curves of Res4 and Res 3. Res1 and Res2 anti-resonance frequency (Fp, that is impedance peak) should be less than Res3 and Res4 anti-resonance frequency, because Res1 and Res2 are series resonators, fp point will form 2.402GHz to 2.482GHz suppression in CELL filter, and Res3 and Res4 are parallel resonators, form high impedance above 2.482GHz, therefore form 2.482GHz frequency pass band in CELL filter. Therefore, in the embodiment of the invention, the frequency of Res1 and Res2 is set to be less than the frequency of Res3 and Res4. Because a certain suppression bandwidth is ensured, the frequency difference between Res1 and Res2 is required to be larger than 60MHz, preferably larger than 75MHz. The frequency difference between the Res3 and Res4 resonant bins (i.e., the bins with the lowest impedance) forms a structure in circle 5 on the thick solid line, which helps to improve rejection.

Fig. 10A and fig. 10B are schematic diagrams of frequency difference setting versus WiFi rejection variation of the resonator Res3 and the resonator Res4 in the CELL filter according to the embodiment of the present invention, wherein a thick line is a curve where the frequency difference is between 10MHz and 20MHz, a thin line in fig. 10A is a curve where the frequency difference is less than 10MHz, and a thin line in fig. 10B is a curve where the frequency difference is greater than 20MHz, respectively, and it can be seen from the graphs that the rejection is better when the frequency difference is between 10MHz and 20 MHz.

The CELL filter in the embodiment of the present invention may be applied to a local area network signal extractor, and the extractor further includes a band pass filter for extracting a local area network signal. The above CELL filter or local area network signal extractor, when applied to a communication device, helps to improve the performance of the latter.

According to the technical scheme of the embodiment of the invention, a new extractor topological structure is adopted, and the insertion loss of the CELL filter in low-frequency and high-frequency bands is improved by setting inductance values, resonator frequency and the like, the inhibition of the CELL filter on a WiFi frequency band is improved, and the insertion loss of the WiFi filter is also improved; meanwhile, the insertion loss of frequency points adjacent to WiFi can be improved by setting the proportion of the electromechanical coupling coefficients of the resonators in the CELL filter and the resonators of the WiFi filter.

The above-described embodiments should not be construed as limiting the scope of the invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions can occur, depending on design requirements and other factors. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A cellular communication system (CELL) filter having an antenna end and an output end, the CELL filter comprising first to fourth inductors and first to fourth resonators, wherein:

the first inductor, the first resonator, the second resonator and the second inductor are sequentially connected in series between the antenna end and the output end;

the first ends of the third resonator, the third inductor and the fourth resonator are positioned between the first resonator and the second resonator, and the second ends of the third resonator, the third inductor and the fourth resonator are grounded through the fourth inductor or the second ends of the third resonator, the third inductor and the fourth resonator are grounded through the inductors respectively.

2. The CELL filter of claim 1, further comprising a fifth inductor having a first terminal connected to the first terminal of the third inductor and a second terminal connected to the first terminal of the third or fourth resonator.

3. The CELL filter of claim 1, wherein one or more of the first through fourth resonators further have an inductor connected in parallel across them.

4. The CELL filter of claim 1 further comprising a fifth resonator and a sixth inductor, the fifth resonator having a first end connected to a connection point of the second resonator to the second inductor or to a connection point of the first resonator to the second resonator and a second end connected to ground via the sixth inductor.

5. The CELL filter of claim 1 wherein an inductor is connected in parallel across the second resonator.

6. The CELL filter according to any one of claims 1 to 5,

the first inductance is between 3nH and 4.5nH, the second inductance is between 1.5nH and 5nH, and the third inductance is between 7nH and 20 nH;

or the first inductance is between 3.2nH and 4nH, the second inductance is between 2nH and 4nH, and the third inductance is between 8.5nH and 15nH.

7. The CELL filter of any one of claims 1 to 5, wherein the frequencies of the first and second resonators are less than the frequencies of the third and fourth resonators.

8. The CELL filter of claim 7,

the frequency difference of the first resonator and the second resonator is larger than 60MHz;

the frequency difference between the third resonator and the fourth resonator is between 5MHz and 25MHz, or between 10MHz and 20 MHz.

9. The CELL filter according to any one of claims 1 to 5 wherein the resonators are acoustic wave resonators.

10. A local area network signal extractor comprising a band pass filter for extracting a local area network signal, wherein the local area network signal extractor further comprises a CELL filter according to any one of claims 1 to 9.

11. A communication device comprising the CELL filter of any one of claims 1 to 9 or comprising the local area network signal extractor of claim 10.