CN115051716B

CN115051716B - Multiplexer and communication device

Info

Publication number: CN115051716B
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: 2023-11-28
Anticipated expiration: 2041-03-09
Also published as: CN115051716A

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 transmission branches and a plurality of receiving branches, each transmission branch comprises a first electric bridge, a second electric bridge, a first transmission filter and a second transmission filter, and each receiving branch comprises a receiving filter; the multi-path transmitting branch is connected IN series through the ISO port and the IN port of the second bridge IN the adjacent transmitting branch, the IN port of the second bridge of the transmitting branch positioned at the first position is connected with the antenna of the multiplexer, the ISO port of the second bridge of the transmitting branch positioned at the last position is connected to the first end of the receiving filter of each path of receiving branch, and the second end of the receiving filter of each path of 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 technology, and in particular, to a multiplexer and a communication device.

Background

With the development of wireless communication technology, requirements on data transmission rates are increasing, and high utilization of spectrum resources and complexity of spectrum correspond to the data transmission rates. 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 vital role in the radio frequency front-end module, so that out-of-band interference and noise can be filtered out to meet the requirements of the radio frequency system and the communication protocol on signal to noise ratio, the communication quality is improved, and the user experience is improved. Meanwhile, the system has higher requirements on the performance of the filter, and also has higher requirements on 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, not electromagnetic waves, as a source of resonance, the wavelength of the mechanical waves is much shorter than the wavelength of the electromagnetic waves. Thus, the volume of the acoustic wave resonator and its constituent filters is greatly reduced relative to conventional electromagnetic filters. On the other hand, the crystal orientation 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 complex design requirements of steep transition zone, low insertion loss and the like can be met. Because of the characteristics of small size, high roll-off, low insertion loss and the like, the acoustic wave filter with the acoustic wave filter as a core is widely applied to communication systems.

In future 5G communication, the small base station system will use higher transmitting frequency, and due to space attenuation, the small base station system will necessarily increase the power of the transmitting signal, in order to increase the sensitivity of the receiver, it will necessarily put higher requirements on the transmit-receive isolation, so the small base station system will necessarily require smaller size of the filter and multiplexer, higher power capacity, higher isolation, lower cost, and the main use of the cavity filter and cavity multiplexer in the base station system at present is small insertion loss, good out-of-band rejection and high isolation of the filter and multiplexer in the cavity structure, but one significant disadvantage is that the size is larger, the processing cost is high, and it is difficult to be widely applied in future 5G communication, while the sound wave filter and multiplexer features good insertion loss, high out-of-band rejection and lower cost, but one significant disadvantage is that the power capacity is worse, and the current power capacity is only about 1.5W, so it is difficult to adapt to the requirements of future 5G communication. Therefore, how to use the acoustic wave filter technology to increase the isolation of the multiplexer and also to greatly increase the power capacity thereof is still a technical problem to be solved.

At present, a conventional technical means for implementing a quad-multiplexer is to connect two duplexers in parallel, as shown in fig. 1, and fig. 1 is a schematic diagram of a circuit of a quad-multiplexer according to the prior art. In the quad-multiplexer shown in fig. 1, the first duplexer covers one transmitting frequency band and one receiving frequency band, the second duplexer covers one other transmitting frequency band and one other receiving frequency band, and such a topology is simple, but the performance of the quad-multiplexer is completely determined by the performance of the duplexer, if the isolation of the duplexer is poor, the isolation of the quad-multiplexer is poor, and at the same time, the power capacity of such a topology is completely determined by the power capacity of the filters constituting the duplexer, so the power capacity is poor, and it is difficult to satisfy future 5G applications.

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

Disclosure of Invention

In view of this, the present invention provides a multiplexer and a communication device, which can simultaneously increase the isolation and the power capacity of the multiplexer, the isolation can be increased by about 20dB to 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 electric bridge, a second electric bridge, a first transmitting filter and a second transmitting filter, and each receiving branch comprises a receiving filter; IN each path of transmitting branch, the 0 degree port of the first bridge is grounded through a resistor, the-90 degree port is connected with the transmitting port, the first transmitting filter is connected between the IN port of the first bridge and the 0 degree port of the second bridge IN a bridging manner, and the second transmitting filter is connected between the ISO port of the first bridge and the-90 degree port of the second bridge IN a bridging manner; the multi-path transmitting branch is connected IN series through the ISO port and the IN port of the second bridge IN the adjacent transmitting branch, the IN port of the second bridge of the transmitting branch positioned at the first position is connected with the antenna of the multiplexer, the ISO port of the second bridge of the transmitting branch positioned at the last 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.

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

Optionally, the filter is an acoustic wave filter.

Optionally, 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 transmission filters in different transmission branches are different; the communication frequency bands of the receiving filters have no common frequency point.

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

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 a 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 the 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 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 bridge are sequentially connected in series; the multi-path transmitting branch is connected IN series through the ISO port and the IN port of the bridge IN the adjacent transmitting branch, the IN port of the bridge of the transmitting branch positioned at the first position is connected with the antenna of the multiplexer, the ISO port of the bridge of the transmitting branch positioned at the last position is connected to the first end of the receiving filter of each path of receiving branch, and the second end of the receiving filter of each path of receiving branch is connected to each receiving end of the multiplexer.

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

Optionally, the filter is an acoustic wave filter.

Optionally, the transmitting filters in the same transmitting branch are identical in structure; the communication frequency bands of the transmission filters in different transmission branches are different; the communication frequency bands of the receiving filters have no common frequency point.

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

A communication device comprising a multiplexer according to the 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 the receiving and transmitting.

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 a circuit of a quad-worker according to the prior art;

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

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

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

FIG. 5 is a diagram showing the comparison between the TX and RX band isolation of band 1 in the quad-band device shown in FIG. 2;

FIG. 6 is a diagram showing the comparison between the TX and RX band isolation of band 3 in the quad-band device shown in FIG. 2;

FIG. 7 is a schematic diagram showing cross isolation between TX in band 3 and RX in band 1 in the quad-band device shown in FIG. 2;

FIG. 8 is a schematic diagram showing cross isolation contrast between TX in band 1 and RX in band 3 in the quad-band device shown in FIG. 2;

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

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

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

Detailed Description

The technical scheme of the invention is described below with reference to the accompanying drawings. Fig. 2 is a schematic diagram of the structure of a quad-pod according to an embodiment of the present invention. The quad in fig. 2 is mainly composed 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 the 4 90-degree electric bridges are identical and are respectively an electric bridge 1, an electric bridge 2, an electric bridge 3 and an electric bridge 4. The 6 filters are respectively a transmitting filter 11, a transmitting filter 12, a transmitting filter 21, a transmitting filter 22, a receiving filter 1, and a receiving filter 2. Wherein the transmission filter 11 and the transmission filter 12 are two identical filters and the transmission filter 21 and the transmission 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 the pass bands do not overlap each other in the frequency spectrum. Taking the quad filter composed of band 1 and band 3 as an example, the transmit filter 11 and the transmit filter 12 may be band 1 transmit path filters, the transmit filter 21 and the transmit filter 22 may be band 3 transmit path filters, the receive filter 1 may be band 1 receive path filters, and the receive filter 2 may be band 3 receive path filters.

The isolation of the multiplexer is explained here: taking a quad as an example, only the first transmitting port TX1 is isolated from the first receiving port RX1 and the second receiving port RX2, and the second transmitting port TX2 is isolated from the first receiving port RX1 and the second receiving port RX 2. The first transmitting port TX1 and the second transmitting port TX2 have no isolation requirement, and the first receiving port RX1 and the second receiving port RX2 have no isolation requirement.

Fig. 3 is a schematic diagram of a 90 degree bridge in connection with an embodiment of the present invention. As shown in FIG. 3, the 90 degree bridge has 4 ports, namely J1, J2, J3 and J4, if J1 is used as an input end, the J4 port is an isolation end, and J2 and J3 are output ends, the output signals of the two ports have equal amplitude and 90 degrees phase difference, specifically, the output of the J3 port is 0 degree, the output of the J2 end is-90 degrees, and the J4 end has no signal output theoretically, but in reality, only limited isolation can be achieved, so weak signals leak out. The 90 degree bridge is reciprocal and either port can be used as an input, and the corresponding isolation and output will also change with the IN port. Fig. 4 is a table listing the phase relationship between ports of the 90 degree bridge.

The quad-combiner shown in fig. 2 includes two transmitting branches, each of which includes two bridges and two transmitting filters. Taking the first path of transmitting branch as an example, the first path of transmitting branch comprises a bridge 1 and a bridge 2, and a transmitting filter 11 and a transmitting filter 12, and the connection relation 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 the ISO port of the bridge 2 and the IN port of the bridge 4, the IN port of the bridge 2 is connected to the antenna, and the ISO port of the bridge 4 is connected to the receiving filter 1 and the receiving filter 2, respectively, and may be grounded via a matching circuit.

The quad applies the configuration shown in fig. 2, which is described below, to help improve the transmit-receive isolation. When the transmitted signal is analyzed first, the isolation of TX1 to RX1 and RX2, and TX2 to RX1 and RX2 is measured.

The signal transmitted from the first transmission port TX1, with an initial phase denoted as P, is split into two signals after passing through the bridge 1, which are the signal S1 coming out of the IN port and the signal S2 coming out of the ISO port of the bridge 1, respectively. According to the bridge principle, the Phase (S1) of the signal S1 coming out of the IN port of the bridge 1 is delayed by 90 degrees, and the Phase (S2) of the signal S2 coming out of the ISO port of the bridge 1 is unchanged, i.e. Phase (S1) =p-90 °, phase (S2) =p-0 °. Signal S1 and signal S2 continue to pass into port 1 of transmit filter 11 and port 1 of transmit filter 12, respectively. The two signals respectively pass through the transmitting filter 11 and the transmitting filter 12 and then respectively enter the 0-degree port and the-90-degree port of the bridge 2. Since the transmission filter 11 and the transmission filter 12 are filters having the same structure, the phase changes of the output signals after passing through the two filters are the same. According to the bridge principle, since the ISO port of the bridge 2 is connected to the IN port of the bridge 4, and the other three ports of the bridge 4 are respectively connected to 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 each other, that is, the filters have no common frequency point, the 3 ports are equivalent to external high-resistance devices, the IN port of the bridge 4 will present a high-resistance state, and the ISO port of the bridge 2 is equivalent to an external high-resistance device, so that 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 emitted after passing through the bridge 2. While a small portion of the energy of the signal S1 and the signal S2 will leak out of the ISO port of the bridge 2. Because the ISO port of the bridge has an isolation function, the signal leaked from the ISO port of the bridge 2 is attenuated, and the attenuation value is equivalent to the isolation value of the bridge, so that the transceiving isolation can be improved. The isolation of the existing bridge product is approximately 20dB to 25dB, so that the receiving and transmitting isolation can be improved by 20dB to 25dB by simply considering the isolation effect of the bridge.

The Phase (S1) of the signal S1 coming out of the IN port of the bridge 2 is unchanged, the Phase (S2) of the signal S2 is delayed by 90 degrees, that is, phase (S1) =p-90 ° -0 ° =p-90 °, phase (S2) =p-0 ° -90 ° =p-90 °, that is, the Phase of the signal S1 coming out of the IN port of the bridge 2 is identical to the Phase of the signal S2, and the amplitude is identical, and the signal S2 can be synthesized into a single signal to be emitted from the antenna. The Phase (S1) of the signal S1 leaking from the ISO port of the bridge 2 is delayed by 90 degrees, the Phase (S2) of the signal S2 is unchanged, i.e. Phase (S1) =p-90 ° -90 ° =p-180 °, phase (S2) =p-0 ° -0 ° =p-0 °, i.e. the Phase of the signal S1 leaking from the ISO port of the bridge 2 is 180 degrees different from the Phase of the signal S2, the amplitudes are the same, and the two signals can completely cancel each other theoretically, thereby improving the isolation between TX1 and RX 2.

The principle of improving the transmit-receive isolation can be categorized into the following two points: (1) the bridge itself has an isolating effect; (2) By utilizing the characteristics of the bridge, the two paths of signals leaked from the transmitting end TX1 to the receiving end have the same amplitude and 180 degrees phase difference so as to cancel each other.

The isolation of RX1 to TX1 and TX2, RX2 to TX1 and TX2 is analyzed as follows.

The received signals received from the antenna (whether RX1 and RX 2) enter bridge 2 from the IN port of bridge 2, and most of the energy again exits 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 through the bridge 2 from the 0 degree port and the-90 degree port. 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 a received signal, the 0 degree port and the-90 degree port of the bridge 2 are equivalent to external high-resistance devices. IN this case, according to the bridge principle, the signal coming IN from the IN port of the bridge 2 is divided into two paths by work and comes 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 action of the bridge, and the attenuation value is equivalent to the isolation value of the bridge and is about 20 to 25dB. The isolation between transceivers is improved by 20 to 25dB. Similarly, most of the received signal energy from the ISO port of bridge 2 is attenuated by about 20 to 25dB by the isolation of the bridge when it enters bridge 4 from the IN port of bridge 4, and the energy that leaks to the transmit end. The received signal, after coming out of the ISO port of the bridge 4, enters the corresponding receiving filter through the matching circuit.

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

The quad-filter application of the configuration shown in fig. 2 also helps to increase the transmit power capacity because the transmit signal is split into two paths after passing through the bridge, each path of signal having a power reduced by a factor of 1 compared to the transmit signal, i.e., each filter receives only half of the transmit signal. For example, if the limit power of a single filter is 1W, the power capacity of the multiplexer formed by the prior art is 1W, and 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 quad-multiplexer by 1 time. To ensure that the signals can combine or cancel each other, the electrical lengths of the two paths between bridge 1 and bridge 2 as shown in the figure remain identical. Likewise, the electrical lengths of the two paths shown in the figure between bridge 3 and bridge 4 are also kept uniform.

The structure of the above-described quadplexer may be extended to a hexaplexer or a multiplexer as shown in fig. 9 and 10. Fig. 9 is a schematic diagram of the structure of a multiplexer according to an embodiment of the present invention, and fig. 10 is a schematic diagram of the 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 function of the bridge at the transmitting end is to divide the equal power of a signal into two paths, wherein the phase of one path is delayed by 90 degrees compared with the other path, so that a power divider and a 90-degree phase shifter can be used to replace the bridge, 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 the structure of another multiplexer according to the embodiment of the present invention. As shown in fig. 11, the bridge at the transmitting end is replaced by a power divider and a 90-degree phase shifter, the input end of the power divider is connected with the transmitting port, and the two output ends are respectively connected with 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 the receiving and transmitting.

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 multiplexer comprising 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 path of transmitting branch, the 0 degree port of the first bridge is grounded through a resistor, the-90 degree port is connected with the transmitting port, the first transmitting filter is connected between the IN port of the first bridge and the 0 degree port of the second bridge IN a bridging manner, and the second transmitting filter is connected between the ISO port of the first bridge and the-90 degree port of the second bridge IN a bridging manner;

the multi-path transmitting branch is connected IN series through an ISO port and an IN port of a second bridge IN the adjacent transmitting branch, the IN port of the second bridge of the transmitting branch positioned at the first position is connected with an antenna of the multiplexer, the ISO port of the second bridge of the transmitting branch positioned at the last position is connected to the first end of a 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;

the ISO port of the second bridge of the transmitting branch at the last position is also connected with the first end of the matching circuit, and the second end of the matching circuit is grounded;

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, and the communication frequency bands of the filters in the multiplexer have no common frequency point.

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

3. The multiplexer of claim 1, wherein the electrical lengths of the paths between the first bridge and the second bridge are uniform in the same transmit branch.

4. A multiplexer comprising a plurality of transmitting branches and a plurality of receiving branches, wherein,

each path of 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 path of receiving branch comprises a receiving filter;

in each path of transmitting branch, the input end of the power divider is connected with the 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 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 bridge are sequentially connected in series;

the multi-channel transmitting branch is connected IN series through the ISO port and the IN port of the bridge IN the adjacent transmitting branch, the IN port of the bridge of the transmitting branch positioned at the first position is connected with the antenna of the multiplexer, the ISO port of the bridge of the transmitting branch positioned at the last 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;

the ISO port of the bridge of the last transmitting branch is also connected with the first end of a matching circuit, the second end of the matching circuit is grounded

5. The multiplexer of claim 4, wherein the filter is an acoustic wave filter.

6. The multiplexer of claim 4, wherein the electrical lengths of the paths between the power divider and the bridge are uniform in the same transmit branch.

7. A communication device comprising a multiplexer according to any one of claims 1 to 6.