CN115149967B

CN115149967B - Cellular communication system filter and local area network signal extractor and communication device

Info

Publication number: CN115149967B
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: 2023-11-21
Anticipated expiration: 2041-03-30
Also published as: CN115149967A

Abstract

A cellular communication system (CELL) filter and local area network signal extractor and communication device are disclosed. 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 third resonator, the third inductor and the fourth resonator have first ends located between the first resonator and the second resonator, and second ends thereof are grounded through the fourth inductor or the second ends thereof are respectively grounded through the inductors. By adopting the technical scheme of the invention, the insertion loss of the CELL filter in the low frequency band and the high frequency band and the inhibition of the CELL filter to the WiFi frequency band are improved, and in addition, the insertion loss of the WiFi filter is 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 WiFi frequency bands (2402-2482 MHz), suppressing the interference signals as much as possible, and simultaneously, having lower insertion loss for 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 the 3400-3600MHz frequency band need to be compatible, so that the signals in the frequency band also need to have the lowest insertion loss as possible. This requires a wider bandwidth (699-3600 MHz) for the filter with as much WiFi rejection as possible, ensuring 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 one is a WiFi filter, one end of the two filters is connected to the antenna ANT, and the other end is a respective port cell_out and wifi_out.

The WiFi filter passes 2402MHz-2482MHz signals, and signals in other frequency bands are filtered. The CELL frequency band is passed by signals of 699MHz-3600MHz except 2402MHz-2482 MHz. The CELL filter has the function of restraining WiFi signals as much as possible, and meanwhile, the smaller the insertion loss is, the better the insertion loss is; the WiFi filter has the function of reducing the insertion loss of the WiFi frequency band, and suppressing signals of other frequency bands as much as possible. As shown in fig. 2A and 2B, fig. 2A and 2B are a typical curve diagram of a CELL filter and a typical curve diagram of a WiFi filter in the prior art, respectively.

The current extractor structure is difficult to be compatible with the lowest and highest frequencies under the condition of meeting WiFi frequency range inhibition, and under the condition of meeting 699MHz insertion loss, 3.6GHz insertion loss can be poor, and similarly, under the condition of meeting 3600MHz insertion loss, 699MHz insertion loss can be poor. Meanwhile, the impedance mismatch of frequency points close to the CELL filter and the WiFi is serious, and the insertion loss is poor at 2378MHz (B40 frequency band) and 2496MHz (B41 frequency band). The degradation of the insertion loss of each frequency point will deteriorate the signal-to-noise ratio of the signal, and the system power consumption will be increased by reducing the signal transmission rate, so that the insertion loss of the frequency point needs to be improved.

Disclosure of Invention

In view of the above, the present invention proposes a cellular communication system filter and a lan signal extractor and a communication device to solve the above-mentioned 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, 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 third resonator, the third inductor and the fourth resonator have first ends located between the first resonator and the second resonator, and second ends thereof are grounded through the fourth inductor or the second ends thereof are respectively grounded through the inductors.

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

Optionally, one or more of the first to fourth resonators are further connected in parallel with an inductance at both ends thereof.

Optionally, the device further comprises a fifth resonator and a sixth inductor, the first end of the fifth resonator is 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 the second end is grounded via the sixth inductor.

Optionally, the two ends of the second resonator are connected with an inductor in parallel.

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; alternatively, 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 smaller than the frequencies of the third resonator and the fourth resonator.

Optionally, the frequency difference between the first resonator and the second resonator is greater than 60MHz; the frequency difference between 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 comprising a band pass filter for extracting local area network signals, said local area network signal extractor further comprising a CELL filter according to the present invention.

A communication device comprising the CELL filter of the present invention or comprising the local area network signal extractor of claim 10.

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

Drawings

For purposes of illustration and not limitation, the 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 in connection with the present invention;

FIGS. 2A and 2B are a typical curve diagram of a CELL filter and a typical curve diagram of a WiFi filter, respectively, in the prior art;

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

fig. 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 circuits of two CELL filters according to embodiments of the present invention;

FIGS. 6A and 6B are schematic and partial enlarged views, respectively, of the corresponding CELL filter insertion loss variation at high frequencies when the inductance L1 is greater than 4nH, in accordance with an embodiment of the present invention;

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

FIG. 7A is a partially enlarged schematic illustration of the variation of insertion loss at high frequencies of a corresponding CELL filter when the inductance L2 is greater than and less than 1.5nH in accordance with an embodiment of the present invention;

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

FIG. 8A is a schematic diagram of a change in insertion loss at low frequencies of a corresponding CELL filter when L3 is greater than and less than 7nH, in accordance with an embodiment of the present invention;

FIG. 8B is a partially enlarged schematic illustration of a change in insertion loss at low frequencies of a corresponding CELL filter when L3 is greater than 20nH in accordance with an embodiment of the present invention;

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

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

Detailed Description

In the embodiment of the invention, a novel WiFi extractor (comprising a CELL band-stop filter and a WiFi band-pass filter) topological structure is provided, and better extractor performance is obtained through setting parameters such as inductance, resonator frequency, resonator electromechanical coupling coefficient and the like. Embodiments of the present invention are illustrated in the following drawings.

Fig. 3 is a schematic diagram of a circuit of a CELL filter according to an embodiment of the invention. As shown in fig. 3, main elements of the CELL filter, including inductors L1 to L4 and resonators Res1 to Res4, are included in a dashed box. Wherein the inductance L1 is connected to the antenna end ANT, and the inductance L2 is connected to the port cell_out of the CELL filter. The resonator in the embodiment of the present invention may be an acoustic wave resonator including a bulk acoustic wave resonator and a surface acoustic wave resonator. The connection of the resonators Res1 and Res2 is also connected to both the resonators Res3 and Res4 and to the first end of the inductor L3, the second ends of all three being connected to ground via 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. For a reasonable range of inductance values for the three, where 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 smaller than the frequency of the resonators Res3 and Res4, and the frequency difference between the resonators Res1 and Res2 is greater than 60MHz, and the frequency difference between the resonators Res3 and Res4 is between 5MHz and 25MHz, preferably between 10MHz and 20 MHz.

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

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

The performance and structure of the WiFi extractor in the embodiments of the present invention will be further described below with reference to the structure shown in fig. 3. Fig. 6A and 6B are schematic diagrams and partial enlarged views of the corresponding CELL filter insertion loss variation at high frequencies when the inductance L1 is greater than 4nH, respectively, according to an embodiment of the present invention. Fig. 6C is a schematic diagram of a variation of the insertion loss of the corresponding WiFi filter when the inductance L1 is less than 3.2nH according to an embodiment of the invention. In each of the graphs of fig. 6A to 6C, the thick line corresponds to the L1 inductance value of 3.2 to 4nH, and the thin line corresponds to the L1 inductance value of not 3.2 to 4 nH. When the inductance value of L1 is smaller 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 larger than 4nH, the insertion loss at the high frequency of the corresponding CELL filter is greatly deteriorated.

Fig. 7A is a partially enlarged schematic illustration of the variation of insertion loss at high frequencies of the corresponding CELL filter when the inductance L2 is greater than and less than 1.5nH in accordance with an embodiment of the 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 dotted line corresponds to the case where the L2 inductance is less than 1.5nH, it can be seen that L2 is preferably greater than 1.5nH, which helps to obtain better high-frequency insertion loss performance.

Fig. 7B is a schematic diagram illustrating a change in frequency band insertion loss of a corresponding CELL filter adjacent to a WiFi filter when the inductance L2 is greater than 5nH according to an embodiment of the present invention. As can be seen from the figure, when L2 is too large, the insertion loss is deteriorated, and 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 that L2 is within the aforementioned reasonable range.

Fig. 8A is a schematic diagram of a change in insertion loss at low frequencies of a corresponding CELL filter when L3 is greater than and less than 7nH, according to an embodiment of the invention. The graph is a locally amplified curve, wherein the thick line corresponds to the case that the inductance of L3 is larger than 7nH, and the thin line corresponds to the case that the inductance of L3 is smaller than 7nH, and as can be seen from the graph, L3 needs to be larger than 7nH to ensure that the low-frequency insertion loss is better.

Fig. 8B is a partially enlarged schematic illustration of the variation of insertion loss at low frequencies of the corresponding CELL filter when L3 is greater than 20nH in accordance with an embodiment of the invention. It can be seen that when L3 is too large, the insertion loss will be deteriorated, and the thin curve corresponds to the deterioration condition in the figure, and the thick curve corresponds to the L3 in the reasonable range.

Fig. 9 is a schematic diagram of a WiFi frequency band and corresponding resonant impedance of a CELL filter according to an embodiment of the 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 some suppression in the WiFi frequency band (2402 to 2482 MHz). Thin line 1 and thin line 2, i.e. the impedance curves Res2 and Res1 with the highest impedance at 2.4GHz and 2.482GHz, respectively, and thin line 3 and thin line 4, i.e. the impedance curves Res4 and Res3 with the highest impedance at 2.5GHz and 2.515GHz frequencies. The antiresonant frequencies of Res1 and Res2 (Fp, i.e., the highest impedance point) are less than those of Res3 and Res4 because Res1 and Res2 are series resonators, the Fp point will form a rejection of 2.402GHz to 2.482GHz in the CELL filter, while Res3 and Res4 are parallel resonators, forming a high impedance above 2.482GHz, thus forming a passband above 2.482GHz in the CELL filter. The frequencies of Res1 and Res2 are set to be less than those of Res3 and Res4 in the embodiment of the present invention. Since a certain suppression bandwidth is to be ensured, it is necessary that the frequency difference between Res1 and Res2 is larger than 60MHz, preferably larger than 75MHz. The frequency difference of the resonance frequency points Res3 and Res4 (i.e. the frequency points with the lowest impedance) forms a structure on the bold line in circle 5, contributing to improved rejection.

Fig. 10A and 10B are schematic diagrams of curves of frequency difference settings of the resonator Res3 and the resonator Res4 in the CELL filter according to the embodiment of the present invention, respectively, in which the thick line is a curve with a frequency difference between 10MHz and 20MHz, the thin line in fig. 10A is a curve with a frequency difference less than 10MHz, and the thin line in fig. 10B is a curve with a frequency difference greater than 20MHz, and it can be seen from the figures that the suppression is better when the frequency difference is between 10MHz and 20 MHz.

The CELL filter in the embodiment of the invention can be applied to a local area network signal extractor, and the extractor also comprises a band-pass filter for extracting local area network signals. The above-described CELL filter or local area network signal extractor helps to improve the performance of the latter when applied to a communication device.

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

The above embodiments do not limit the scope of the present invention. It will be apparent to those skilled in the art that various modifications, combinations, sub-combinations and alternatives can occur depending upon design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of the present invention.

Claims

1. A cellular communication system (CELL) filter having an antenna end and an output, 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, and other resonators are not connected in series between the first resonator and the second resonator;

the third resonator, the third inductor and the fourth resonator have first ends located between the first resonator and the second resonator, and second ends thereof are grounded through the fourth inductor or the second ends thereof are respectively grounded through the inductors.

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 are further connected in parallel across an inductance.

4. The CELL filter of claim 1, further comprising a fifth resonator and a sixth inductor, wherein 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 wherein the second end is grounded via the sixth inductor.

5. The CELL filter of claim 1, wherein the second resonator has an inductance connected in parallel across the second resonator.

6. The CELL filter of any of claims 1-5,

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;

alternatively, 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 1-5, wherein the frequencies of the first resonator and the second resonator are less than the frequencies of the third resonator and the fourth resonator.

8. The CELL filter as set forth in claim 7, wherein,

the frequency difference between the first resonator and the second resonator is greater 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 of any one of claims 1-5, wherein the resonator is an acoustic wave resonator.

10. A local area network signal extractor comprising a band pass filter for extracting local area network signals, wherein the local area network signal extractor further comprises the CELL filter of 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.