CN115051716A

CN115051716A - Multiplexer and communication device

Info

Publication number: CN115051716A
Application number: CN202110255040.0A
Authority: CN
Inventors: 柴竹青
Original assignee: ROFS Microsystem Tianjin Co Ltd
Current assignee: ROFS Microsystem Tianjin Co Ltd
Priority date: 2021-03-09
Filing date: 2021-03-09
Publication date: 2022-09-13
Anticipated expiration: 2041-03-09
Also published as: CN115051716B

Abstract

The invention discloses a multiplexer and communication equipment, which can simultaneously improve the isolation degree and the power capacity of the multiplexer, wherein the multiplexer comprises a plurality of transmitting branches and a plurality of receiving branches, each transmitting branch comprises a first bridge, a second bridge, a first transmitting filter and a second transmitting filter, and each receiving branch comprises a receiving filter; the multiple transmitting branches are connected IN series through the ISO port and the IN port of the second bridge IN the adjacent transmitting branches, the IN port of the second bridge of the transmitting branch positioned at the head position is connected with the antenna of the multiplexer, the ISO port of the second bridge of the transmitting branch positioned at the tail position is connected to the first end of the receiving filter of each receiving branch, and the second end of the receiving filter of each receiving branch is connected to each receiving end of the multiplexer.

Description

Multiplexer and communication device

Technical Field

The present invention relates to the field of filter technologies, and in particular, to a multiplexer and a communication device.

Background

With the development of wireless communication technology, the demand of data transmission rate is higher and higher, and the data transmission rate corresponds to high utilization rate of spectrum resources and complexity of spectrum. The complexity of the communication protocol puts strict requirements on the performance of each module of the radio frequency system, and the radio frequency filter plays a crucial role in the radio frequency front-end module, and can filter out-of-band interference and noise to meet the requirements of the radio frequency system and the communication protocol on the signal-to-noise ratio, improve the communication quality and improve the user experience. Meanwhile, the system has higher requirements on the performance of the filter and the volume size, and the acoustic wave filter can just meet the requirements. The acoustic wave resonator generates resonance using the piezoelectric effect of the piezoelectric crystal. Since resonance is generated by mechanical waves, rather than electromagnetic waves as a source of resonance, the wavelength of mechanical waves is much shorter than the wavelength of electromagnetic waves. Therefore, the size of the acoustic wave resonator and the filter formed by the acoustic wave resonator is greatly reduced compared with the size of a traditional electromagnetic filter. On the other hand, since the crystal growth of the piezoelectric crystal can be well controlled at present, the loss of the resonator is extremely small, the quality factor is high, and the complicated design requirements such as a steep transition zone, low insertion loss and the like can be met. Because the acoustic wave filter has the characteristics of small size, high roll-off, low insertion loss and the like, the acoustic wave filter taking the acoustic wave filter as the core is widely applied to communication systems.

In the future 5G communication, the small base station system becomes an important component, the small base station system will use a higher transmitting frequency, the power of the transmitted signal will be inevitably increased due to the spatial attenuation, and a higher requirement on the receiving and transmitting isolation will be inevitably provided in order to improve the sensitivity of the receiver, so the small base station system will inevitably require a small filter and a multiplexer, a high power capacity, a high isolation and a low cost, the present base station system mainly uses a cavity filter and a cavity multiplexer, the filter and the multiplexer of the cavity structure have small insertion loss, good out-of-band rejection and high isolation, but one of the obvious defects is a large size, a high processing cost and difficult wide application in the future 5G communication, and the acoustic wave filter and the multiplexer have the characteristics of good insertion loss, high out-of-band rejection and low cost, but one of the obvious defects is a poor power capacity, at present, the power capacity is only about 1.5W, and the requirement of future 5G communication is difficult to adapt. Therefore, how to use the acoustic wave filter technology, in addition to increasing the isolation of the multiplexer, it is still a technical problem to be solved to increase the power capacity of the multiplexer to a large extent.

At present, the conventional technical means for realizing a quadruplex device is to connect two duplexers in parallel, as shown in fig. 1, and fig. 1 is a schematic diagram of a circuit of a quadruplex device according to the prior art. In the duplexer shown in fig. 1, the first duplexer covers one transmitting frequency band and one receiving frequency band, and the second duplexer covers one other transmitting frequency band and one other receiving frequency band, although the topology is simple, the performance of the duplexer is completely determined by the performance of the duplexer, if the isolation of the duplexer is poor, and the power capacity of the topology is completely determined by the power capacity of the filter constituting the duplexer, so the power capacity is also poor, and it is difficult to meet the application of 5G in the future.

Aiming at the current situation that the multiplexer isolation degree of the current conventional topological structure is only 60dB, the power capacity is only about 1.5W, and the current situation is difficult to be suitable for a future 5G small base station system.

Disclosure of Invention

In view of the above, the present invention provides a multiplexer and a communication device, which can simultaneously increase the isolation and the power capacity of the multiplexer, wherein the isolation can be increased by about 20dB to about 30dB, and the power capacity can be increased by about 1 time.

The invention provides the following technical scheme:

a multiplexer comprises a plurality of transmitting branches and a plurality of receiving branches, wherein each transmitting branch comprises a first bridge, a second bridge, a first transmitting filter and a second transmitting filter, and each receiving branch comprises a receiving filter; IN each transmitting branch, a 0-degree port of the first bridge is grounded through a resistor, a-90-degree port of the first bridge is connected with a transmitting port, a first transmitting filter is connected between an IN port of the first bridge and a 0-degree port of the second bridge IN a bridging mode, and a second transmitting filter is connected between an ISO port of the first bridge and a-90-degree port of the second bridge IN a bridging mode; the multiple transmitting branches are connected IN series through the ISO port and the IN port of the second bridge IN the adjacent transmitting branches, the IN port of the second bridge of the transmitting branch positioned at the head is connected with the antenna of the multiplexer, the ISO port of the second bridge of the transmitting branch positioned at the tail is connected to the first end of the receiving filter of each receiving branch, and the second end of the receiving filter of each receiving branch is connected to each receiving end of the multiplexer.

Optionally, the ISO port of the second bridge of the transmitting branch located at the last bit is further connected to a first end of a matching circuit, and a second end of the matching circuit is grounded.

Optionally, the filter is an acoustic wave filter.

Optionally, in the same transmission branch, the first transmission filter and the second transmission filter have the same structure; the communication frequency bands of the first transmitting filters in different transmitting branches are different; the communication frequency band of each receiving filter has no common frequency point.

Optionally, in the same transmitting branch, the electrical lengths of the paths between the first bridge and the second bridge are identical.

A multiplexer comprises a plurality of transmitting branches and a plurality of receiving branches, wherein each transmitting branch comprises a power divider, a 90-degree phase shifter, a first transmitting filter, a second transmitting filter and an electric bridge, and each receiving branch comprises a receiving filter; in each path of transmitting branch, the input end of the power divider is connected with a transmitting port, the first output end of the power divider, the 90-degree phase shifter, the first transmitting filter and the 0-degree port of the electric bridge are sequentially connected in series, and the second output end of the power divider, the second transmitting filter and the-90-degree port of the electric bridge are sequentially connected in series; the multiple transmitting branches are connected IN series through the ISO port and the IN port of the electric bridge IN the adjacent transmitting branches, the IN port of the electric bridge of the transmitting branch positioned at the head is connected with the antenna of the multiplexer, the ISO port of the electric bridge of the transmitting branch positioned at the tail is connected to the first end of the receiving filter of each receiving branch, and the second end of the receiving filter of each receiving branch is connected to each receiving end of the multiplexer.

Optionally, the ISO port of the bridge of the transmitting branch at the last bit is also connected to a first end of the matching circuit, and a second end of the matching circuit is grounded.

Optionally, the filter is an acoustic wave filter.

Optionally, the transmit filters in the same transmit branch are of the same structure; the communication frequency bands of the transmitting filters in different transmitting branches are different; the communication frequency band of each receiving filter has no common frequency point.

Optionally, in the same transmitting branch, the electrical lengths of the paths between the power divider and the bridge are the same.

A communication device comprising a multiplexer according to the present invention.

By adopting the technical scheme of the invention, the multiplexer not only can effectively improve the power capacity of the transmitting channel, but also can improve the isolation between transmitting and receiving.

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 a circuit of a quadplexer in accordance with the prior art;

FIG. 2 is a schematic diagram of a quad-plexer configuration according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a 90 degree bridge associated with an embodiment of the present invention;

FIG. 4 is a table listing the phase relationship between the ports of the 90 degree bridge;

FIG. 5 is a diagram of the TX and RX frequency band isolation contrast of band 1 in the quadplexer of FIG. 2;

FIG. 6 is a diagram of the TX and RX frequency band isolation contrast of band 3 in the quadplexer of FIG. 2;

FIG. 7 is a diagram of cross-isolation contrast between TX and RX bands for band 3 and band 1 in the quadplexer of FIG. 2;

FIG. 8 is a diagram of cross-isolation contrast between TX and RX bands for band 1 and band 3 in the quadplexer of FIG. 2;

fig. 9 is a schematic diagram of the structure of a hexaplexer according to an embodiment of the present invention;

FIG. 10 is a diagram illustrating the structure of a multiplexer according to an embodiment of the present invention;

fig. 11 is a diagram illustrating another structure of a multiplexer according to an embodiment of the present invention.

Detailed Description

The technical scheme of the invention is explained in the following by combining the attached drawings. Fig. 2 is a schematic view of the structure of a quadruplexer according to an embodiment of the present invention. The quadplexer in fig. 2 mainly consists of 4 90-degree bridges and 6 filters, and has two transmitting terminals TX1 and TX2, two receiving terminals RX1 and RX2, and one antenna terminal. Wherein 4 90-degree bridges are completely the same, namely bridge 1, bridge 2, bridge 3 and bridge 4. The 6 filters are a transmission filter 11, a transmission filter 12, a transmission filter 21, a transmission filter 22, a reception filter 1, and a reception filter 2, respectively. Where the transmit filter 11 and the transmit filter 12 are two identical filters and the transmit filter 21 and the transmit filter 22 are two identical filters. The transmission filter 11, the transmission filter 21, the reception filter 1, and the reception filter 2 are filters of different communication bands, and have no overlapping part of the pass bands on the spectrum. Taking the quadplexer composed of band 1 and band 3 as an example, the transmission filter 11 and the transmission filter 12 may be band 1 transmit path filters, the transmission filter 21 and the transmission filter 22 may be band 3 transmit path filters, the reception filter 1 may be a band 1 reception path filter, and the reception filter 2 may be a band 3 reception path filter.

The isolation of the multiplexer is explained here as follows: taking the quadplexer as an example, it is only required that the first transmitting port TX1 has isolation from the first receiving port RX1 and the second receiving port RX2, and the second transmitting port TX2 has isolation from the first receiving port RX1 and the second receiving port RX 2. The first transmitting port TX1 has no isolation requirement with the second transmitting port TX2, and the first receiving port RX1 has no isolation requirement with the second receiving port RX 2.

Fig. 3 is a schematic diagram of a 90-degree bridge associated with an embodiment of the present invention. As shown in fig. 3, the 90-degree bridge has 4 ports, which are J1, J2, J3 and J4, respectively, if J1 is used as an input terminal, the J4 port is an isolation terminal, J2 and J3 are output terminals, output signals of the two ports are equal in amplitude and 90-degree in phase difference, specifically, the output of the J3 port is 0 degree, the output of the J2 port is-90 degree, and the J4 port theoretically has no signal output, but in reality, only limited isolation can be achieved, so that a weak signal leaks out. The 90-degree bridge is reciprocal, any one port can be used as an input port, and the corresponding isolation port and output port can be changed along with the change of the IN port. Fig. 4 is a table listing the phase relationship between the ports of the 90 degree bridge.

The quadplexer shown in fig. 2 includes two transmitting branches, and each transmitting branch includes two bridges and two transmitting filters. Taking the first transmitting branch as an example, the first transmitting branch includes a bridge 1 and a bridge 2, and a transmitting filter 11 and a transmitting filter 12, and the connection relationship is shown in the figure. The ground resistance R in the figure may be 50 ohms. The bridge 2 and the bridge 4 are connected IN series through an ISO port of the bridge 2 and an IN port of the bridge 4, the IN port of the bridge 2 is connected with an antenna, and the ISO port of the bridge 4 can be connected with the receiving filter 1 and the receiving filter 2 respectively and can be grounded through a matching circuit.

The quadruplex device employs the structure shown in fig. 2, which is useful for improving the isolation between transmission and reception, as will be described below. When the transmitting signals are analyzed, the isolation of TX1 to RX1 and RX2, and the isolation of TX2 to RX1 and RX2 are analyzed.

The signal transmitted from the first transmit port TX1, with the initial phase denoted as P, is divided into two signals after passing through the bridge 1, i.e., a signal S1 from the IN port of the bridge 1 and a signal S2 from the ISO port. According to the bridge principle, the Phase (S1) of the signal S1 coming out from the IN port of the bridge 1 is delayed by 90 degrees, and the Phase (S2) of the signal S2 coming out from the ISO port of the bridge 1 is unchanged, i.e., Phase (S1) ═ P-90 °, and Phase (S2) ═ P-0 °. The signal S1 and the signal S2 continue to be transmitted into the 1 port of the transmission filter 11 and the 1 port of the transmission filter 12, respectively. The two signals respectively enter a 0-degree port and a-90-degree port of the bridge 2 after passing through the transmitting filter 11 and the transmitting filter 12. Since the transmission filter 11 and the transmission filter 12 are filters having the same structure, the phase change of the output signal after passing through the two filters is the same. According to the bridge principle, because the ISO port of the bridge 2 is connected with the IN port of the bridge 4, and the other three ports of the bridge 4 are respectively connected with the transmitting filter 21, the transmitting filter 22, the receiving filter 1 and the receiving filter 2, since the passband frequencies of all the transmitting filters and all the receiving filters are different and do not overlap with each other, i.e. all the filters have no common frequency point, the 3 ports are equivalent to external high-impedance devices, then the IN port of the bridge 4 will present a high-impedance state, and further the ISO port of the bridge 2 is equivalent to an external high-impedance device, so most of the signal energy of the signal S1 and the signal S2 will come out from the IN port of the bridge 2 to enter the antenna and be transmitted out after passing through the bridge 2. And a small portion of the energy of signals S1 and S2 may leak out of the ISO port of bridge 2. Because the ISO port of the bridge has an isolation function, a signal leaked from the ISO port of the bridge 2 is attenuated by an amount equivalent to the isolation value of the bridge, so that the transmitting and receiving isolation can be improved. The isolation of the existing bridge product is about 20dB to 25dB, so the isolation of the receiving and transmitting can be improved by 20dB to 25dB by only considering the isolation effect of the bridge.

The Phase (S1) of the signal S1 coming out from the IN port of the bridge 2 is unchanged, and the Phase (S2) of the signal S2 is delayed by 90 degrees, that is, the Phase (S1) is P-90 ° -0 ° -P-90 °, the Phase (S2) is P-0 ° -90 ° -P-90 °, that is, the Phase of the signal S1 coming out from the IN port of the bridge 2 is the same as that of the signal S2, the amplitude of the signal is the same, and the signal can be synthesized into one signal and transmitted from an antenna. The Phase (S1) of the signal S1 leaked from the ISO port of the bridge 2 is delayed by 90 degrees, the Phase (S2) of the signal S2 is unchanged, i.e., the Phase (S1) is P-90 ° -P-180 °, the Phase (S2) is P-0 ° -P-0 °, i.e., the Phase of the signal S1 and the Phase of the signal S2 leaked from the ISO port of the bridge 2 are different by 180 degrees and have the same amplitude, and the two signals theoretically completely cancel each other, so that the isolation between TX1 and RX1 and RX2 is improved.

Therefore, the principle of improving the isolation between transmitting and receiving can be summarized as the following two points: (1) the bridge has an isolation function; (2) by utilizing the characteristics of the bridge, two paths of signals leaked from the transmitting end TX1 to the receiving end have the same amplitude and 180-degree phase difference, and then are mutually counteracted.

The following analyzes the isolation of RX1 from TX1 and TX2, and RX2 from TX1 and TX2 when the antenna receives signals.

The received signal (whether RX1 or RX2) from the antenna enters bridge 2 from the IN port of bridge 2, and most of the energy comes out from the ISO port of bridge 2 and then enters bridge 4 from the IN port of bridge 4. A small portion of the energy leaks out of the 0 degree port and the-90 degree port through the bridge 2. Because the 0-degree port and the-90-degree port of the bridge 2 are respectively connected with the transmitting filter 11 and the transmitting filter 12, for receiving signals, the 0-degree port and the-90-degree port of the bridge 2 are equivalent to external high-impedance devices. IN this case, according to the bridge principle, the signal coming from the IN port of the bridge 2 is divided into two paths, which come out from the 0-degree port and the-90-degree port of the bridge 2, respectively, and each path of signal is attenuated by the isolation of the bridge, which is equivalent to the isolation of the bridge, and is about 20 to 25 dB. The isolation between transceiving is improved by 20 to 25 dB. Similarly, when most of the received signal energy from the ISO port of the bridge 2 enters the bridge 4 from the IN port of the bridge 4, the energy leaking to the transmitting end is also isolated by the bridge, and attenuated by about 20 to 25 dB. After the received signal comes out from the ISO port of the bridge 4, the received signal enters a corresponding receiving filter through a matching circuit.

Fig. 5 is a diagram illustrating the TX and RX frequency band isolation contrast of band 1 in the quadplexer shown in fig. 2. Fig. 6 is a diagram illustrating the TX and RX frequency band isolation contrast of band 3 in the quadplexer shown in fig. 2. Fig. 7 is a diagram illustrating cross-isolation contrast between TX and RX bands of band 3 and 1 in the quadplexer shown in fig. 2. Fig. 8 is a diagram illustrating cross-isolation contrast between TX and RX bands of band 1 and 3 in the quadplexer shown in fig. 2. In the above figures, the solid line corresponds to a prior art quadplexer, the dashed line corresponds to a quadplexer in the embodiment of the present invention, the quadplexer is a quadplexer composed of a frequency band 1 and a frequency band 3, TX1 is a transmitting end of the frequency band 1, and the frequency band is 2110MHz to 2170 MHz; RX1 is the receiving end of frequency band 1, the frequency band is 1920MHz-1980 MHz; TX2 is the transmitting end of frequency band 3, the frequency band is 1805MHz-1880 MHz; RX2 is the receiving end of band 3, and the frequency band is 1710MHz-1785 MHz. From the simulation results, the isolation of the quadruplex can be improved by about 20 to 30dB by adopting the structure of the embodiment of the invention.

The quadruplex device applies the structure shown in fig. 2 and is also beneficial to improving the transmission power capacity, because the transmission signal passes through the bridge, the transmission signal is divided into two paths, and the power of each path of signal is reduced by 1 time compared with the transmission signal, namely, the power borne by each filter is only half of the transmission signal. For example, if the limit power of the single-branch filter is 1W, the power capacity of the multiplexer formed in the prior art is 1W, while the power capacity of the multiplexer of the present invention is 2W, i.e. the topology of the present invention can increase the power capacity of the quadruplex by 1. To ensure that the signals combine or cancel each other, the electrical lengths of the two paths between bridge 1 and bridge 2, as shown in the figure, are kept consistent. Likewise, the electrical lengths of the two paths between bridge 3 and bridge 4, as shown in the figure, are also kept the same.

The structure of the above-described quadruplex multiplexer can be extended to a hexaplexer or a multiplexer as shown in fig. 9 and 10. Fig. 9 is a schematic diagram of a structure of a hexaplexer according to an embodiment of the present invention, and fig. 10 is a schematic diagram of a structure of a multiplexer according to an embodiment of the present invention, in which a general structure including n transmitting branches and n receiving branches is shown. It can be seen that the bridge at the transmitting end is used to divide a signal into two paths with equal power, wherein the phase of one path is delayed by 90 degrees from that of the other path, so that the bridge can be replaced by a power divider and a 90-degree phase shifter, taking the structure shown in fig. 10 as an example, the structure shown in fig. 11 can be formed, and fig. 11 is a schematic diagram of another multiplexer structure according to an embodiment of the present invention. As shown in fig. 11, the electric bridge at the transmitting end is replaced by a power divider and a 90-degree phase shifter, where the input end of the power divider is connected to the transmitting port, and the two output ends are respectively connected to the 90-degree phase shifter and a transmitting filter.

By adopting the technical scheme of the embodiment of the invention, the multiplexer not only can effectively improve the power capacity of the transmitting channel, but also can improve the isolation between transmitting and receiving.

The above-described embodiments should not be construed as limiting the scope of the invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may 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 multiplexer includes a plurality of transmitting branches and a plurality of receiving branches,

each transmitting branch comprises a first bridge, a second bridge, a first transmitting filter and a second transmitting filter, and each receiving branch comprises a receiving filter;

IN each transmitting branch, a 0-degree port of the first bridge is grounded through a resistor, a-90-degree port of the first bridge is connected with a transmitting port, a first transmitting filter is connected between an IN port of the first bridge and a 0-degree port of the second bridge IN a bridging mode, and a second transmitting filter is connected between an ISO port of the first bridge and a-90-degree port of the second bridge IN a bridging mode;

the multiple transmitting branches are connected IN series through the ISO port and the IN port of the second bridge IN the adjacent transmitting branches, the IN port of the second bridge of the transmitting branch positioned at the head is connected with the antenna of the multiplexer, the ISO port of the second bridge of the transmitting branch positioned at the tail is connected to the first end of the receiving filter of each receiving branch, and the second end of the receiving filter of each receiving branch is connected to each receiving end of the multiplexer.

2. The multiplexer of claim 1, wherein the ISO port of the second bridge located in the last transmit branch is further connected to a first terminal of a matching circuit, a second terminal of the matching circuit being connected to ground.

3. The multiplexer of claim 1 or 2, wherein the filter is an acoustic filter.

4. The multiplexer of claim 1 or 2,

in the same transmitting branch, the first transmitting filter and the second transmitting filter have the same structure;

the communication frequency bands of the first transmitting filters in different transmitting branches are different;

the communication frequency band of each filter has no common frequency point.

5. The multiplexer of claim 1 or 2, wherein the electrical lengths of the respective paths between the first bridge and the second bridge are the same in the same transmit branch.

6. A multiplexer includes a plurality of transmitting branches and a plurality of receiving branches,

each transmitting branch comprises a power divider, a 90-degree phase shifter, a first transmitting filter, a second transmitting filter and an electric bridge, and each receiving branch comprises a receiving filter;

in each path of transmitting branch, the input end of the power divider is connected with a transmitting port, the first output end of the power divider, the 90-degree phase shifter, the first transmitting filter and the 0-degree port of the electric bridge are sequentially connected in series, and the second output end of the power divider, the second transmitting filter and the-90-degree port of the electric bridge are sequentially connected in series;

the multiple transmitting branches are connected IN series through ISO ports and IN ports of the bridges IN the adjacent transmitting branches, the IN port of the bridge of the transmitting branch positioned at the head position is connected with the antenna of the multiplexer, the ISO port of the bridge of the transmitting branch positioned at the tail position is connected to the first end of the receiving filter of each receiving branch, and the second end of the receiving filter of each receiving branch is connected to each receiving end of the multiplexer.

7. The multiplexer of claim 6, wherein the ISO port of the bridge of the transmit branch at the last bit is further coupled to a first terminal of a matching circuit, a second terminal of the matching circuit being coupled to ground.

8. The multiplexer of claim 6 or 7, wherein the filter is an acoustic filter.

9. The multiplexer of claim 6 or 7, wherein,

the transmitting filters in the same transmitting branch have the same structure;

the communication frequency bands of the transmitting filters in different transmitting branches are different;

the communication band of each receiving filter has no common frequency point.

10. The multiplexer of claim 6 or 7, wherein the electrical lengths of the paths between the power divider and the bridge are the same in the same transmit branch.

11. A communication device comprising a multiplexer according to any one of claims 1 to 10.