CN115051716B - Multiplexer and communication device - Google Patents

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

Multiplexers and communications equipment

Technical field

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

Background technique

With the development of wireless communication technology, people have higher and higher requirements for data transmission rate. Corresponding to the data transmission rate is the high utilization of spectrum resources and the complexity of spectrum. The complexity of communication protocols has put forward strict requirements on the performance of each module of the radio frequency system. In the radio frequency front-end module, the radio frequency filter plays a vital role. It can filter out out-of-band interference and noise to meet the requirements of the radio frequency system and The communication protocol has requirements for signal-to-noise ratio, improves communication quality, and enhances user experience. At the same time, in addition to having high requirements on filter performance, the system also has high requirements on volume and size, and acoustic wave filters can just meet these requirements. Acoustic resonators use the piezoelectric effect of piezoelectric crystals to generate resonance. Since resonance is generated by mechanical waves rather than electromagnetic waves as the source of resonance, the wavelength of mechanical waves is much shorter than that of electromagnetic waves. Therefore, the volume of the acoustic resonator and the filter it consists of is greatly reduced compared with the size of the traditional electromagnetic filter. On the other hand, since the crystallographic growth of piezoelectric crystals can currently be well controlled, the resonator has extremely small losses and a high quality factor, and can cope with complex design requirements such as steep transition zones and low insertion loss. Due to the characteristics of small size, high roll-off, and low insertion loss of acoustic wave filters, acoustic wave filters with this core have been widely used in communication systems.

In future 5G communications, the small base station system will become an important component. The small base station system will use a higher transmission frequency. Due to spatial attenuation, the power of the transmitted signal will inevitably be increased. In order to improve the sensitivity of the receiver, it will inevitably Transceiver isolation puts forward higher requirements, so future small base station systems will inevitably require small filters and multiplexers, high power capacity, high isolation, and low cost. Currently, cavities are mainly used in base station systems. Filters and cavity multiplexers. Filters and multiplexers with cavity structures have small insertion loss, good out-of-band suppression, and high isolation. However, one of their significant disadvantages is that they are large in size and have high processing costs, making it difficult to use them in the future. Acoustic filters and multiplexers are widely used in 5G communications. The characteristics of acoustic wave filters and multiplexers are good insertion loss, high out-of-band suppression, and low cost. However, one of their significant shortcomings is poor power capacity. The current power capacity is only about 1.5W. , it is difficult to adapt to the requirements of future 5G communications. Therefore, how to use acoustic wave filter technology to not only improve the isolation of the multiplexer but also significantly increase its power capacity is still a technical problem to be solved.

At present, the conventional technical means for realizing a quadplexer is to connect two duplexers in parallel, as shown in Figure 1. Figure 1 is a schematic diagram of a circuit of a quadplexer in the prior art. In the quadplexer shown in Figure 1, the first duplexer covers one transmit frequency band and one receive frequency band, and the second duplexer covers another transmit frequency band and another receive frequency band. Although this topology is simple, it The performance of the quadplexer is completely determined by the performance of the duplexer. If the isolation of the duplexer is poor, the isolation of the quadplexer must be poor. At the same time, the power capacity of such a topology is completely determined by the filtering that constitutes the duplexer. The power capacity of the device is also poor, so it is difficult to meet future 5G applications.

The isolation of multiplexers for the current conventional topology is only 60dB, and the power capacity is only about 1.5W, which is difficult to apply to the current status of future 5G small base station systems.

Contents of the invention

In view of this, the present invention proposes a multiplexer and communication equipment that can simultaneously improve the isolation and 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 present invention provides the following technical solutions:

A multiplexer includes multiple transmitting branches and multiple receiving branches. Each transmitting branch includes a first electric bridge and a second electric bridge as well as a first transmitting filter and a second transmitting filter. Each receiving branch The branch contains a receiving filter; in each transmitting branch, the 0-degree port of the first bridge is connected to ground through a resistor, the -90-degree port is connected to the transmit port, the IN port of the first bridge and the 0-degree port of the second bridge The first transmit filter is connected across the ISO port of the first bridge and the -90 degree port of the second bridge. The second transmit filter is connected between the ISO port of the first bridge and the -90 degree port of the second bridge; the multi-channel transmit branch passes through the adjacent transmit branch. The ISO port and IN port of the second bridge are connected in series, the IN port of the second bridge of the transmitting branch located at the first position is connected to the antenna of the multiplexer, and the second electric bridge of the transmitting branch located at the last position The ISO port 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 the first end of the matching circuit, and the second end of the matching circuit 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 transmitting filters in different transmitting branches are different; the communication frequency bands of each receiving filter are different. common frequency point.

Optionally, in the same transmitting branch, the electrical lengths of each path between the first electric bridge and the second electric bridge are consistent.

A multiplexer includes multiple transmit branches and multiple receive branches. Each transmit branch includes a power divider, a 90-degree phase shifter, a first transmit filter, a second transmit filter, and a bridge. Each receiving branch includes a receiving filter; in each transmitting branch, the input end of the power divider is connected to the transmit port, the first output end of the power divider, the 90-degree phase shifter, the first transmit filter, and the bridge The 0-degree ports are connected in series, and the second output end of the power divider, the second transmit filter, and the -90-degree port of the bridge are connected in series; the multi-channel transmit branches are connected in series through the bridges in the adjacent transmit branches. The ISO port and the IN port are connected in series. The IN port of the bridge of the transmitting branch located at the first position is connected to the antenna of the multiplexer. The ISO port of the bridge of the transmitting branch located at the last position is connected to the receiving branch of each channel. The first end of the receiving filter and the second end of the receiving filter of each receiving branch are connected to each receiving end of the multiplexer.

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

Optionally, the filter is an acoustic wave filter.

Optionally, 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; and the communication frequency bands of the receiving filters have no common frequency points.

Optionally, in the same transmitting branch, the electrical lengths of each path between the power splitter and the electric bridge are consistent.

A communication device, characterized by including the multiplexer of the present invention.

Using the technical solution of the present invention, the multiplexer can not only effectively increase the power capacity of the transmitting channel, but also improve the isolation between the transmitter and the receiver.

Description of the drawings

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

Figure 1 is a schematic diagram of a circuit of a quadplexer in the prior art;

Figure 2 is a schematic diagram of the structure of a quadplexer according to an embodiment of the present invention;

Figure 3 is a schematic diagram of a 90-degree electric bridge related to an embodiment of the present invention;

Figure 4 is a list of the phase relationships between the ports of the 90-degree bridge;

Figure 5 is a schematic diagram illustrating the isolation comparison between the TX and RX bands in frequency band 1 of the quadplexer shown in Figure 2;

Figure 6 is a schematic diagram illustrating the isolation comparison between the TX and RX bands in frequency band 3 of the quadplexer shown in Figure 2;

Figure 7 is a schematic diagram of the cross-isolation comparison between the TX of band 3 and the RX band of band 1 in the quadplexer shown in Figure 2;

Figure 8 is a schematic diagram illustrating the comparison of cross-isolation between the TX of frequency band 1 and the RX frequency band of frequency band 3 in the quadplexer shown in Figure 2;

Figure 9 is a schematic diagram of the structure of a six-plexer according to an embodiment of the present invention;

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

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

Detailed ways

The technical solution of the present invention will be described below with reference to the accompanying drawings. Figure 2 is a schematic diagram of the structure of a quadplexer according to an embodiment of the present invention. The quadplexer in Figure 2 is mainly composed of four 90-degree bridges and six filters. The quadplexer has two transmitting ends TX1 and TX2, two receiving ends RX1 and RX2, and an antenna end. Four of the 90-degree bridges are identical, namely bridge 1, bridge 2, bridge 3, and bridge 4. The six filters are transmit filter 11, transmit filter 12, transmit filter 21, transmit filter Filter 22, receive filter 1, receive filter 2. 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 transmitting filter 11, the transmitting filter 21, the receiving filter 1, and the receiving filter 2 are filters in different communication frequency bands, and the passbands of the frequency spectrum do not overlap with each other. Taking the quadplexer composed of frequency band 1 and frequency band 3 as an example, the transmission filter 11 and the transmission filter 12 can be the frequency band 1 transmission path filter, and the transmission filter 21 and the transmission filter 22 can be the frequency band 3 transmission path filter. Receive filter 1 may be a band 1 receive path filter, and receive filter 2 may be a band 3 receive path filter.

Here is an explanation of the isolation of the multiplexer: Taking the quadplexer as an example, only the first transmit port TX1 is required to have isolation from the first receive port RX1 and the second receive port RX2, and the second transmit port TX2 is required to be isolated from the first receive port RX1. The receiving port RX1 and the second receiving port RX2 have isolation. The first transmitting port TX1 and the second transmitting port TX2 have no isolation requirements, and the first receiving port RX1 and the second receiving port RX2 have no isolation requirements.

Figure 3 is a schematic diagram of a 90 degree bridge related to an embodiment of the present invention. As shown in Figure 3, the 90-degree bridge has 4 ports, namely J1, J2, J3, and J4. If J1 is used as the input terminal, the J4 port is the isolation terminal, and J2 and J3 are the output terminals. The output signal amplitudes are equal and the phase difference is 90 degrees. Specifically, the J3 port output is 0 degrees, the J2 terminal output is -90 degrees, and the J4 terminal theoretically has no signal output, but in reality only limited isolation can be achieved, so there will be a weak The signal leaks out. The 90-degree bridge is reciprocal, any port can be used as an input terminal, and the corresponding isolation terminal and output terminal will also change as the IN port changes. Figure 4 is a list of the phase relationships between the ports of a 90-degree bridge.

The quadplexer shown in Figure 2 contains two transmit branches, and each transmit branch contains two bridges and two transmit filters. Taking the first transmit branch as an example, it includes bridge 1 and bridge 2 as well as transmit filters 11 and 12. The connection relationship is as shown in the figure. The ground resistance R in the figure can be 50 ohms. Bridge 2 and Bridge 4 are connected in series through the ISO port of Bridge 2 and the IN port of Bridge 4. The IN port of Bridge 2 is connected to the antenna. The ISO port of Bridge 4 is connected to receiving filter 1 and receiving filter 2 respectively. connection, also via a matching circuit to ground.

The quadplexer uses the structure shown in Figure 2 to help improve the isolation between transmitting and receiving, as explained below. First analyze the isolation of TX1 to RX1 and RX2, and TX2 to RX1 and RX2 when transmitting signals.

The signal transmitted from the first transmission port TX1 has an initial phase marked as P. After passing through the bridge 1, it is divided into two signals, namely the signal S1 coming out of the IN port of the bridge 1 and the signal S2 coming out of the ISO port. According to the bridge principle, the phase Phase (S1) of the signal S1 coming out of the IN port of bridge 1 will be delayed by 90 degrees, and the phase Phase (S2) of the signal S2 coming out of the ISO port of bridge 1 will not change, that is, Phase (S1)=P-90°, Phase (S2)=P-0°. Signal S1 and signal S2 continue to transmit into port 1 of the transmit filter 11 and port 1 of the transmit filter 12 respectively. After passing through the transmission filter 11 and the transmission filter 12 respectively, these two signals enter the 0 degree port and the -90 degree port of the bridge 2 respectively. Because the transmission filter 11 and the transmission filter 12 are filters with the same structure, the phase changes of the output signals after passing through the two filters are the same. According to the bridge principle, because the ISO port of bridge 2 is connected to the IN port of bridge 4, the other three ports of bridge 4 are respectively connected to transmit filter 21, transmit filter 22, receive filter 1 and receive filter 2 connections, since the passband frequencies of all transmit filters and all receive filters are different and they do not overlap, that is, the filters have no common frequency points, so these 3 ports are equivalent to external high-impedance devices. , then the IN port of bridge 4 will be in a high-impedance state, and the ISO port of bridge 2 is equivalent to an external high-impedance device. Therefore, most of the signal energy of signal S1 and signal S2 will flow from bridge 2 after passing through bridge 2. The IN port comes out into the antenna and transmits out. A small part of the energy of signal S1 and signal S2 will leak out from the ISO port of bridge 2. Because the ISO port of the bridge itself has an isolation effect, the signal leaking from the ISO port of bridge 2 will attenuate, and the attenuation value is equivalent to the isolation value of the bridge, so the transmitting and receiving isolation can be improved. The isolation of existing bridge products is about 20dB to 25dB, so simply considering the isolation effect of the bridge, the transmitting and receiving isolation can be improved by 20dB to 25dB.

The phase Phase (S1) of the signal S1 coming out of the IN port of bridge 2 remains unchanged, and the phase Phase (S2) of the signal S2 will be delayed by 90 degrees, that is, Phase (S1) = P-90°-0° = P- 90°, Phase(S2)=P-0°-90°=P-90°, that is, the signal S1 and the signal S2 coming out of the IN port of bridge 2 have the same phase and the same amplitude, and can be synthesized into one signal, from The antenna transmits. The phase Phase (S1) of the signal S1 leaked from the ISO port of the bridge 2 will be delayed by 90 degrees, and the phase Phase (S2) of the signal S2 will not change, that is, Phase (S1) = P-90°-90° = P -180°, Phase(S2)=P-0°-0°=P-0°, that is, the phase difference between signal S1 and signal S2 leaked from the ISO port of bridge 2 is 180 degrees, and the amplitude is the same. The signals will theoretically completely cancel each other out, improving the isolation between TX1 and RX1 and RX2.

Therefore, the principle of improving the isolation of transmitting and receiving can be attributed to the following two points: (1) The bridge itself has the function of isolation; (2) The characteristics of the bridge are used to make the two signals leaked from the transmitting end TX1 to the receiving end have the same amplitude and phase The difference is 180 degrees and cancel each other out.

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 received from the antenna (both RX1 and RX2) 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 the bridge from the IN port of bridge 4 4. A small amount of energy leaks out through 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 connected to the transmit filter 11 and the transmit filter 12 respectively, for the received signal, 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 principle of the bridge, the signal entering from the 2IN port of the bridge will be divided into two channels and come out from the 0 degree port and the -90 degree port of bridge 2 respectively, and will be isolated by the bridge. Each signal will be attenuated, and the attenuation value is equivalent to the isolation value of the bridge, which is about 20 to 25dB. Therefore, the isolation between transmitter and receiver is increased by 20 to 25dB. In the same way, when most of the received signal energy from the ISO port of bridge 2 enters bridge 4 from the IN port of bridge 4, the energy leaked to the transmitter will also be isolated by the bridge and attenuate by about 20 to 25dB. After the received signal comes out from the ISO port of bridge 4, it enters the corresponding receiving filter through the matching circuit.

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

The quadplexer application of the structure shown in Figure 2 also helps to improve the transmission power capacity. This is because after the transmission signal passes through the bridge, the transmission signal is divided into two channels, and the power of each channel signal is reduced by 1 times compared with the transmission signal. , that is, the power that each filter withstands is only half of the transmitted signal. For example, if the limit power of a single filter is 1W, then the power capacity of the multiplexer formed by the existing technology is 1W, while the power capacity of the multiplexer of the present invention is 2W, that is, the topology of the present invention The power capacity of the quadplexer can be doubled. In order to ensure that the signals can be synthesized or cancel each other, the electrical lengths of the two paths between bridge 1 and bridge 2 as shown in the figure must be consistent. In the same way, the electrical lengths of the two paths between bridge 3 and bridge 4 as shown in the figure must also be consistent.

The structure of the above four-plexer can be expanded to a six-plexer or multiplexer, as shown in Figures 9 and 10. Figure 9 is a schematic diagram of the structure of a six-multiplexer according to an embodiment of the present invention. Figure 10 is a schematic diagram of the structure of a multiplexer according to an embodiment of the present invention. It shows a general structure, including n transmit branches. path and n receiving branches. It can be seen that the function of the bridge at the transmitting end is to divide a signal into two channels of equal power. The phase of one channel is 90 degrees later than the other channel. Therefore, a power divider and a 90-degree phase shifter can be used to replace the bridge. Taking the structure shown in Figure 10 as an example, the structure shown in Figure 11 can be formed. Figure 11 is a schematic diagram of the structure of another multiplexer according to an embodiment of the present invention. As shown in Figure 11, the transmitter bridge is replaced by a power divider and a 90-degree phase shifter. The input end of the power divider is connected to the transmit port, and the two output ends are connected to a 90-degree phase shifter and a transmit filter respectively.

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

The above-mentioned specific embodiments do not constitute a limitation on the scope of the present invention. It will 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 modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (7)

1. A multiplexer, including multiple transmitting branches and multiple receiving branches, characterized in that, Each transmitting branch includes a first electric bridge and a second electric bridge and a first transmitting filter and a second transmitting filter, and each receiving branch includes a receiving filter; In each transmit branch, the 0-degree port of the first bridge is connected to the ground through a resistor, the -90-degree port is connected to the transmit port, and the first transmitter is connected between the IN port of the first bridge and the 0-degree port of the second bridge. Filter, the second transmit filter is connected across the ISO port of the first bridge and the -90 degree port of the second bridge; The multiple transmit branches are connected in series through the ISO port and IN port of the second bridge in the adjacent transmit branch, and the IN port of the second bridge of the first transmit branch is connected to the antenna of the multiplexer , the ISO port of the second bridge of the last transmitting branch 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 the multiple Each receiving end of the device; The ISO port of the second bridge of the last transmitting branch is also connected to the first end of the matching circuit, and the second end of the matching circuit is grounded; In the same transmit branch, the first transmit filter and the second transmit filter have the same structure. The first transmit filters in different transmit branches have different communication frequency bands. The communication frequency bands of each filter in the multiplexer are The frequency bands have no common frequency point. 2. The multiplexer of claim 1, wherein the filter is an acoustic wave filter. 3. The multiplexer according to claim 1, wherein in the same transmitting branch, the electrical lengths of the paths between the first bridge and the second bridge are consistent. 4. A multiplexer, including multiple transmitting branches and multiple receiving branches, characterized in that, Each transmit branch includes a power divider, a 90-degree phase shifter, a first transmit filter, a second transmit filter, and a bridge; each receive branch includes a receive filter; In each transmit branch, the input end of the power splitter is connected to the transmit port. The first output end of the power divider, the 90-degree phase shifter, the first transmit filter, and the 0-degree port of the bridge are connected in series. The second output end, the second emission filter, and the -90 degree port of the bridge are connected in series; The multi-channel transmitting branches are connected in series through the ISO port and IN port of the bridge in the adjacent transmitting branch. The IN port of the bridge of the transmitting branch located at the first position is connected to the antenna of the multiplexer, and the IN port of the bridge at the last position is connected. The ISO port of the bridge of the transmitting branch 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 located at the last transmitting branch is also connected to the first end of the matching circuit, and the second end of the matching circuit is grounded. In the same transmit branch, the first transmit filter and the second transmit filter have the same structure. The first transmit filters in different transmit branches have different communication frequency bands. The communication frequency bands of each filter in the multiplexer are The frequency bands have no common frequency points. 5. The multiplexer according to claim 4, characterized in that the filter is an acoustic wave filter. 6. The multiplexer according to claim 4, characterized in that, in the same transmitting branch, the electrical lengths of each path between the power splitter and the electric bridge are consistent. 7. A communication device, characterized by comprising the multiplexer according to any one of claims 1 to 6.