Multiplexer and data communication equipment
By designing a phase cancellation mechanism for transmission lines in the multiplexer, the problem of insufficient isolation between channels in the prior art is solved, and the effect of improving isolation is achieved without using high-order filters.
Patent Information
- Application Number
- CN202511137702.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-14
- Publication Date
- 2025-12-09
AI Technical Summary
In existing technologies, multiplexers cannot effectively improve the isolation between channels without using high-order filters, especially in scenarios with extremely narrow guard bands where performance is low.
By designing a specific circuit structure and utilizing the phase change generated by the transmission line, the power of different transmission branches can be made to be of the same magnitude but 180 degrees out of phase, thus canceling each other out, thereby improving isolation performance and avoiding reliance on high-order filters.
Without increasing filter complexity and cost, the isolation between channels of the multiplexer is significantly improved, meeting the high isolation requirements of mobile communication systems.
Smart Images
Figure CN121098282A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of communication technology, and in particular to a multiplexer and a data communication device. Background Technology
[0002] With the development of mobile communication technology, the diversification of spectrum resources and the efficient utilization of spectrum have become core industry requirements, and the realization of these requirements is inseparable from the accurate separation and processing of multi-band signals. As a key component for separating multi-band signals, the performance of multiplexers directly affects the utilization efficiency of spectrum resources. Among them, the inter-channel isolation is the core indicator for evaluating the performance of multiplexers.
[0003] In related technologies, high-order filters are used to achieve high channel isolation in multiplexers. However, using high-order filters presents challenges such as high cost and design complexity. Furthermore, high-order filters may fail in scenarios with extremely narrow guard bands, leading to lower reliability of the multiplexer.
[0004] Therefore, how to improve the inter-channel isolation of a multiplexer without using high-order filters has become an urgent problem to be solved. Summary of the Invention
[0005] This application provides a multiplexer and a data communication device, which aims to improve the inter-channel isolation of the multiplexer without using high-order filters.
[0006] In a first aspect, this application provides a multiplexer, comprising: a first common terminal, a first filter, a first transmission line, a second filter, a second transmission line, and a first resistor. The first common terminal is used to receive a first communication signal, which includes signals across multiple frequency bands. A first end of the first transmission line is connected to the first common terminal, a second end of the first transmission line is connected to the input terminal of the first filter, and the output terminal of the first filter is used to output signals of a first frequency band. The electrical length of the first transmission line is 1 / 4 wavelength corresponding to the center frequency of the first frequency band. A first end of the second transmission line is connected to the first common terminal, a second end of the second transmission line is connected to the input terminal of the second filter, and the output terminal of the second filter is used to output signals of a second frequency band. The electrical length of the second transmission line is 1 / 4 wavelength corresponding to the center frequency of the second frequency band. The first resistor is connected between the second ends of the first and second transmission lines.
[0007] The technical solution provided in this application brings at least the following beneficial effects:
[0008] When the first communication signal is transmitted from the first common terminal to the output terminals of the first and second filters, if there is signal leakage at the output terminal of the first filter (which can be understood as the output terminal of the first filter injecting interference signals into the multiplexer), the interference signal will be split into two parts: the first part flows through the first resistor to the input terminal of the second filter, and the second part flows through the first transmission line, the first common terminal, and the second transmission line to the input terminal of the second filter. Since the electrical length of the first transmission line is 1 / 4 wavelength corresponding to the center frequency of the first frequency band, the phase of the second part of the signal will shift by 90 degrees when it passes through the first transmission line. Similarly, the phase of the second part of the signal will also shift by 90 degrees when it passes through the second transmission line. Therefore, the phase of the second part of the signal is shifted by 180 degrees compared to the first part of the signal. Thus, when the first part of the signal and the second part of the signal meet at the input terminal of the second filter, they will cancel out some of the interference signals, thereby greatly improving the isolation between the output terminals of the first and second filters, and achieving improved inter-channel isolation of the multiplexer without using higher-order filters.
[0009] One possible implementation is that the sum of the equivalent resistance of the first transmission line and the equivalent resistance of the second transmission line is equal to the resistance of the first resistor.
[0010] Another possible implementation is that the characteristic impedance of the first transmission line is equal to the characteristic impedance of the second transmission line.
[0011] Another possible implementation of the multiplexer includes a third transmission line, a fourth transmission line, and a second resistor. The third transmission line is connected between the second end of the first transmission line and the input of the first filter. The fourth transmission line is connected between the second end of the second transmission line and the input of the second filter. The second resistor is connected between the input of the first filter and the input of the second filter. The electrical length of the third transmission line is one-quarter of the wavelength corresponding to the center frequency of the first frequency band, and the electrical length of the fourth transmission line is one-quarter of the wavelength corresponding to the center frequency of the second frequency band.
[0012] Another possible implementation is that the sum of the equivalent resistances of the first transmission line, the second transmission line, the third transmission line, the fourth transmission line, and the first resistor is equal to the resistance of the second resistor.
[0013] Another possible implementation is that the characteristic impedance of the third transmission line is equal to the characteristic impedance of the fourth transmission line.
[0014] Another possible implementation involves impedance matching between the first common terminal, the output of the first filter, and the output of the second filter.
[0015] Another possible implementation is that the first filter is a dual bandpass filter or a bandpass filter.
[0016] Another possible implementation of the multiplexer includes a first duplexer and a second duplexer. The input of the first duplexer is used to receive the second communication signal, the first output of the first duplexer is connected to a first common terminal, the second output of the first duplexer is connected to the input of the second duplexer, and the first output of the first duplexer is used to output the first communication signal.
[0017] Secondly, this application provides a data communication device, which includes a multiplexer and a modem. The multiplexer is the same as described in the first aspect or any possible implementation of the first aspect. The output of the multiplexer is connected to the input of the modem, which is used to demodulate the received signal.
[0018] The beneficial effects of the second aspect mentioned above are described in the corresponding description of the first aspect, and will not be repeated here. Attached Figure Description
[0019] Figure 1 A schematic diagram illustrating the frequency resource distribution of a communication signal, provided for related technologies;
[0020] Figure 2 A circuit topology diagram of a multiplexer provided for related technologies;
[0021] Figure 3 A schematic diagram of another circuit topology for a multiplexer provided for related technologies;
[0022] Figure 4 A circuit topology diagram of a duplexer is provided for related technologies;
[0023] Figure 5 An isolation characteristic diagram of a duplexer provided for related technologies;
[0024] Figure 6 A schematic diagram showing the distribution of frequency resources occupied by another communication signal provided for related technologies;
[0025] Figure 7 A schematic diagram of another circuit topology for a multiplexer provided for related technologies;
[0026] Figure 8 A schematic diagram of the actual operating frequency of a multiplexer provided for related technologies;
[0027] Figure 9 A schematic diagram of another circuit topology for a duplexer provided for related technologies;
[0028] Figure 10 Another isolation characteristic diagram of a duplexer provided for related technologies;
[0029] Figure 11 A circuit topology diagram of a multiplexer provided in this application;
[0030] Figure 12 A schematic diagram of another circuit topology for a multiplexer provided in this application;
[0031] Figure 13 A schematic diagram of the circuit topology of another multiplexer provided in this application;
[0032] Figure 14 The insertion loss and isolation characteristics of a multiplexer provided in this application;
[0033] Figure 15 A reflection loss diagram of a multiplexer provided in this application;
[0034] Figure 16 The insertion loss and isolation characteristics of a multiplexer provided in this application;
[0035] Figure 17 This is a schematic diagram of the circuit topology of a data communication device provided in this application. Detailed Implementation
[0036] The following is a detailed description of a call detail record (CDR) data recording method provided in this application, with reference to the accompanying drawings.
[0037] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.
[0038] The terms "first" and "second," etc., used in the specification and drawings of this application are used to distinguish different objects or to distinguish different treatments of the same object, rather than to describe a specific order of objects.
[0039] Furthermore, the terms "comprising" and "having," and any variations thereof, used in the description of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include other steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.
[0040] It should be noted that in the embodiments of this application, the words "exemplary" or "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design scheme described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of the words "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.
[0041] To facilitate a clear description of the technical solutions of the embodiments of this application, the terms "first" and "second" are used in the embodiments of this application to distinguish the same or similar items with essentially the same function and effect. Those skilled in the art can understand that the terms "first" and "second" are not intended to limit the quantity or execution order.
[0042] In the description of this application, unless otherwise stated, "a plurality of" means two or more.
[0043] Before introducing the embodiments of this application, the application scenarios involved in this application will be described first.
[0044] like Figure 1 The diagram illustrates the frequency resource distribution of a communication signal according to related technologies. Bands 1 through 4 represent different frequency bands. Band 1 uses frequencies f1 to f2, Band 2 uses frequencies f3 to f4, Band 3 uses frequencies f5 to f6, and Band 4 uses frequencies f7 to f8. f2 to f3 are guard bands for Bands 1 and 2, f4 to f5 are guard bands for Bands 2 and 3, and f6 to f7 are guard bands for Bands 3 and 4.
[0045] Received and distributed via a public terminal, such as Figure 1 In the case of the communication signal shown, a multiplexer (or multi-band divider filter) is inevitably required.
[0046] The application scenarios of the embodiments of this application have been introduced above. The multiplexers in related technologies are described below.
[0047] like Figure 2 The diagram shows a circuit topology of a multiplexer provided by related technologies. Figure 2 The four bandpass filters (BPF1, BPF2, BPF3 and BPF4) are directly combined into a common port COM.
[0048] Specifically, the passband of BPF1 covers the frequency range f1 to f2 of Band 1, the passband of BPF2 covers the frequency range f3 to f4 of Band 2, the passband of BPF3 covers the frequency range f5 to f6 of Band 3, and the passband of BPF4 covers the frequency range f7 to f8 of Band 4. The passbands of each filter are separated by guard bands (f2 to f3, f4 to f5, f6 to f7), forming sequentially arranged independent frequency ranges, thereby achieving selective filtering and separation of signals in different frequency bands.
[0049] This type of multiplexer is mainly used in high-power wireless communication devices, such as base stations or repeaters, and is primarily applied to metal cavity filters.
[0050] However, since each bandpass filter has its own characteristic impedance, while the impedance of the common port COM is fixed, when multiple bandpass filters with different characteristic impedances are directly connected to the same common port COM, the impedance at the port cannot be matched with the impedance of all bandpass filters at the same time, so impedance mismatch will inevitably occur.
[0051] like Figure 3 The diagram shows a circuit topology of another multiplexer provided by related technologies. Figure 3 The multiplexer in the circuit consists of three duplexers (first duplexer D1, second duplexer D2, and third duplexer D3). The second duplexer D2 consists of two bandpass filters (BPF1 and BPF2), and the third duplexer D3 also consists of two bandpass filters (BPF3 and BPF4).
[0052] The common port COM of the first duplexer D1 is used to receive communication signals. The first duplexer D1 separates the low-frequency and high-frequency signals from the received communication signals. The low-frequency signal is output through the low-frequency port L, and the high-frequency signal is output through the high-frequency port H. The low-frequency signal is then separated into Band 1 and Band 2 signals by the second duplexer D2. The high-frequency signal is then separated into Band 3 and Band 4 signals by the third duplexer D3.
[0053] because Figure 3 This type of multiplexer has a simple structure, so impedance mismatch can be easily solved using low-temperature co-fired ceramic (LTCC) technology.
[0054] However, key indicators for evaluating the performance of multiplexers also include inter-channel isolation. Higher inter-channel isolation usually indicates better performance of the multiplexer. Therefore, how to improve the inter-channel isolation of multiplexers is an urgent problem to be solved.
[0055] like Figure 4 The diagram shows a circuit topology of a duplexer provided by related technologies. Figure 4 The first duplexer D1 has three terminals, namely P1, P2 and P3. P2 is used to output low-frequency signals and P3 is used to output high-frequency signals. The isolation between P2 and P3 can characterize the performance characteristics of the first duplexer D1.
[0056] like Figure 5 The diagram shows the isolation characteristics of a duplexer provided by related technologies. The first curve represents the transmission characteristic curve from P1 to P2, which is the low-frequency transmission characteristic curve. The second curve represents the transmission characteristic curve from P1 to P3, which is the high-frequency transmission characteristic curve.
[0057] Depend on Figure 5 As can be seen, the first curve has a larger value (close to 0dB) in the low-frequency range, indicating that the signal loss is smaller at this point; the value decreases as the frequency increases, indicating that the signal loss is greater at this point. This shows that the signal transmitted by P1-P2 experiences less attenuation in the low-frequency range and greater attenuation in the high-frequency range. Similarly, the change in the second curve shows that the signal transmitted by P1-P3 experiences greater attenuation in the low-frequency range and less attenuation in the high-frequency range.
[0058] The third curve represents the signal isolation between P2 and P3, which is... Figure 5 It can be seen that the isolation between P2 and P3 is highly correlated with the attenuation characteristics of the relative frequency band. For example, when the frequency is less than 1.6 GHz, the isolation between P2 and P3 corresponds to the change in the high-frequency transmission characteristic curve (the second curve). When the frequency is greater than 1.6 GHz, the isolation between P2 and P3 corresponds to the change in the low-frequency transmission characteristic curve (the first curve).
[0059] Therefore, to achieve high isolation in a multiplexer, a relatively high attenuation characteristic is required in the corresponding frequency band. To achieve high attenuation characteristics in the filters within the multiplexer, a high filter order is typically required, which increases filter size, manufacturing difficulty, and cost. Higher-order filters are also necessary in the following situations.
[0060] like Figure 6 The diagram shows the frequency resource distribution of another communication signal provided by related technologies. Figure 6 The frequency band Band3 was split into Band3' and Band3', and another frequency band, Band4, was added between them. That is... Figure 6 The actual frequency layout in the code is five frequency bands, but the multiplexer is configured with four frequency bands, which reduces the construction cost of the multiplexer. The circuit topology of the multiplexer can be as follows: Figure 7 .
[0061] like Figure 7 The diagram shows a circuit topology of another multiplexer provided by related technologies. In the diagram, BPF1, BPF2 and BPF4 are bandpass filters of different frequency bands, and DualBPF3 is a dual bandpass filter that allows signals with bandwidths of Band3' and Band3" to pass through. Figure 7 (a) and Figure 7 The only difference in (b) is the multiplexer structure.
[0062] Figure 8 This diagram illustrates the actual operating frequency of a multiplexer for related technologies. Band 4 exists between Band 3' and Band 3" and has a guard band of only tens of MHz. Therefore, in this example, a high-order filter is necessary to filter out Band 4.
[0063] Figure 9 A schematic diagram of another duplexer circuit topology provided for related technologies. Figure 9 yes Figure 7 Part of the multiplexer, also for the purpose of realizing Figure 8 This is a duplexer that separates the Band3 and Band4 frequencies. The duplexer includes three terminals (P1, P2, and P3), where P1 is used to receive signals, P2 is used to output signals in the Band3 frequency band, and P3 is used to output signals in the Band4 frequency band.
[0064] like Figure 10 The figure shown is an isolation characteristic diagram of a multiplexer provided by related technologies. Figure 10 for Figure 9 The diagram shows the isolation characteristics of a medium-duplexer. The fourth curve represents the insertion loss between P1 and P2, the fifth curve represents the insertion loss between P1 and P3, and the sixth curve represents the isolation between P2 and P3. From... Figure 10 It can be seen that the isolation characteristics are 30dB or lower in some bands of band 3 and band 4, and it is difficult to achieve the 40dB or higher isolation typically required by mobile systems.
[0065] In summary, existing technologies use high-order filters to improve the isolation of multiplexers, but this increases filter size, manufacturing difficulty, and cost.
[0066] To address the aforementioned technical problems, this application provides a multiplexer and a data communication device. The core idea is to design a specific circuit structure that utilizes the phase change generated during transmission line transmission to ensure that the power of different transmission branches is equal in magnitude but 180 degrees out of phase, thus canceling each other out. This independently improves the isolation performance between different frequency bands, rather than simply relying on increasing the filter order. This effectively enhances isolation in narrow protection bandwidth scenarios, overcoming the limitations of existing technologies. The 180-degree phase shift is the key mechanism for achieving power cancellation and improved isolation, ensuring that high isolation requirements are met without excessive reliance on high-order filters.
[0067] The embodiments provided in this application will now be described in detail with reference to the accompanying drawings.
[0068] like Figure 11 The diagram shows a circuit topology of a multiplexer 10 provided in this application. The multiplexer 10 includes: a first common terminal G, a first filter F1, a first transmission line L1, a second filter F2, a second transmission line L2, and a first resistor R1.
[0069] The first common terminal G is used to receive the first communication signal S1, which includes signals from multiple frequency bands. The signals from the multiple frequency bands include signals from the first frequency band Band1 and signals from the second frequency band Band2.
[0070] The first end of the first transmission line L1 is connected to the first common terminal G, the second end of the first transmission line L1 is connected to the input terminal of the first filter F1, the output terminal of the first filter F1 is used to output the signal of the first frequency band Band1, and the electrical length of the first transmission line L1 is 1 / 4 wavelength corresponding to the center frequency of the first frequency band Band1.
[0071] The first end of the second transmission line L2 is connected to the first common terminal G, and the second end of the second transmission line L2 is connected to the input terminal of the second filter F2. The output terminal of the second filter F2 is used to output the signal of the second frequency band Band2. The electrical length of the second transmission line L2 is 1 / 4 wavelength corresponding to the center frequency of the second frequency band Band2. The first resistor R1 is connected between the second end of the first transmission line L1 and the second end of the second transmission line L2.
[0072] In one possible implementation, the first filter F1 is a dual bandpass filter or a bandpass filter.
[0073] A dual bandpass filter allows signals from two frequency bands to pass through while blocking signals from other frequency bands. It can adapt to complex frequency layouts (such as...). Figure 8The dual bandpass filter (Band3' and Band3") precisely filters out specific dual-band signals, meeting the needs of communication systems for multi-band signal processing. Furthermore, the dual bandpass filter can process two band signals in a single device, effectively reducing the number of components, shrinking circuit size, increasing system integration, and reducing circuit complexity compared to using a standard bandpass filter.
[0074] The first resistor R1 plays a role in electrical balance in the multiplexer 10. It can reduce circuit imbalance caused by the characteristic difference between the first transmission line L1 and the second transmission line L2, frequency fluctuations or manufacturing errors, and ensure that the isolation and insertion loss performance remain stable within the target frequency band (Band1 and Band2), avoiding sudden changes in characteristics or deterioration of indicators.
[0075] Let A be the connection point of the first transmission line L1, the first filter F1 and the first resistor R1, and B be the connection point of the second transmission line L2, the second filter F2 and the first resistor.
[0076] When the first communication signal S1 is transmitted from the first common terminal G to the output terminals of the first filter F1 and the second filter F2, if there is signal leakage at the output terminal of the first filter F1 (which can be understood as the output terminal of the first filter F1 injecting an interference signal POW into the multiplexer 10), the interference signal POW will be branched into two parts: the first part is POW1, which flows to node B through the first resistor R1; the second part is POW2, which is in phase with POW1. POW2 also flows to node B through the first transmission line L1, the first common terminal G, and the second transmission line L2. Since the electrical length of the first transmission line L1 is 1 / 4 wavelength corresponding to the center frequency of the first frequency band, the phase of POW2 will shift by 90 degrees when it passes through the first transmission line L1. Similarly, the phase will shift by another 90 degrees when it passes through the second transmission line L2. Therefore, POW3 after passing through the second transmission line L2 has a phase shift of 180 degrees compared to POW1. Therefore, when POW3 and POW1 meet at node B, they cancel out some of the interference signals, forming POW4. The smaller POW4 is, the better the isolation. This greatly improves the isolation between the output of the first filter F1 and the output of the second filter F2, achieving improved inter-channel isolation of the multiplexer 10 without using higher-order filters.
[0077] One possible implementation is that the sum of the equivalent resistance of the first transmission line L1 and the equivalent resistance of the second transmission line L2 is equal to the resistance of the first resistor R1.
[0078] In the embodiments of this application, see also Figure 11When the sum of the equivalent resistance of the first transmission line L1 and the equivalent resistance of the second transmission line L2 is equal to the resistance of the first resistor R1, the power of POW will be equally divided at node A. That is, the power of POW1 is equal to the power of POW2. POW3 only changes 180 degrees in phase compared to POW2, and its magnitude remains unchanged, so the power of POW3 is also equal to the power of POW1. Therefore, when POW1 and POW3 meet at node B, they are equal in magnitude but 180 degrees out of phase, thus completely canceling each other out and significantly improving the inter-channel isolation of the multiplexer 10.
[0079] Another possible implementation is that the characteristic impedance of the first transmission line L1 is equal to the characteristic impedance of the second transmission line L2.
[0080] In this embodiment, when the characteristic impedance of the first transmission line L1 is equal to the characteristic impedance of the second transmission line L2, the power of the communication signal S input to the first common terminal G can be evenly distributed to the first transmission line L1 and the second transmission line L2, ensuring that the signal transmission branches corresponding to Band1 and Band2 obtain balanced power transmission, and avoiding excessive signal attenuation or unstable performance in a certain frequency band due to uneven power distribution.
[0081] In addition, since the first resistor R1 plays a role in electrical balance in the multiplexer 10, making the characteristic impedance of the first transmission line L1 equal to the characteristic impedance of the second transmission line L2 helps to achieve impedance matching of the entire multiplexer 10 (between the first common terminal G and the two transmission branches), reduce signal reflection, reduce reflection loss, and improve the overall transmission efficiency of the circuit.
[0082] In addition, making the characteristic impedance of the first transmission line L1 equal to that of the second transmission line L2 can also enhance the stability of isolation and avoid phase shift instability caused by impedance differences, which would affect the isolation effect.
[0083] Another possible implementation, such as Figure 12 The diagram shown is a circuit topology diagram of another multiplexer provided in this application. The multiplexer 10 also includes: a third transmission line L3, a fourth transmission line L4, and a second resistor R2.
[0084] The third transmission line L3 is connected between the second end of the first transmission line L1 and the input terminal of the first filter F1. The fourth transmission line L4 is connected between the second end of the second transmission line L2 and the input terminal of the second filter F2. The second resistor R2 is connected between the input terminals of the first filter F1 and the second filter F2. The electrical length of the third transmission line L3 is 1 / 4 wavelength corresponding to the center frequency of the first frequency band (Band 1), and the electrical length of the fourth transmission line L4 is 1 / 4 wavelength corresponding to the center frequency of the second frequency band (Band 2).
[0085] The embodiments of this application, by adding a third transmission line L3, a fourth transmission line L4, and a second resistor R2, can form a multi-level structure with the original first transmission line L1, second transmission line L2, and first resistor R1, respectively, to perform impedance matching and phase adjustment for different frequency bands, thereby covering a wider frequency range and ensuring good isolation, insertion loss, and reflection loss characteristics in a wider frequency band.
[0086] Another possible implementation, see [link to previous section] Figure 12 The sum of the equivalent resistances of the first transmission line L1, the second transmission line L2, the third transmission line L3, the fourth transmission line L4, and the first resistor R1 is equal to the resistance of the second resistor R2.
[0087] Depend on Figure 12 It can be seen that the circuit consisting of the first transmission line L1, the second transmission line L2, the third transmission line L3, the fourth transmission line L4 and the first resistor R1 is connected in parallel with the second resistor R2. Therefore, the sum of the equivalent resistance values of the first transmission line L1, the second transmission line L2, the third transmission line L3, the fourth transmission line L4 and the first resistor R1 is equal to the resistance value of the second resistor R2, which makes the power of POW equally distributed, that is, the power of POW1 and the power of POW2 are equal.
[0088] See also Figure 12 The circuit consisting of the first transmission line L1, the second transmission line L2, the third transmission line L3, the fourth transmission line L4, the first resistor R1, and the second resistor R2 can be called the isolation boost circuit 101.
[0089] Another possible implementation is that the characteristic impedance of the third transmission line L3 is equal to the characteristic impedance of the fourth transmission line L4.
[0090] The beneficial effects of the embodiments of this application are the same as those when the characteristic impedance of the first transmission line L1 is equal to the characteristic impedance of the second transmission line L2, so they will not be repeated here.
[0091] Another possible implementation involves impedance matching between the first common terminal G, the output of the first filter F1, and the output of the second filter F2.
[0092] Impedance matching reduces signal reflection caused by impedance mismatch during signal transmission between the three terminals, thereby reducing reflection loss. It also ensures that signals in each frequency band (Band 1 and Band 2) can be transmitted with high efficiency, meeting the signal transmission quality requirements of mobile communication devices.
[0093] For example, see [link to previous article] Figure 12The first common terminal G, the output of the first filter F1, and the output of the second filter F2 are all matched to Z0 = 50Ω. The impedance of the first transmission line L1 is Z1, and the impedance of the second transmission line L2 is Z2, Z1 = Z2. The impedance of the third transmission line L3 is Z3, and the impedance of the fourth transmission line L4 is Z4, Z3 = Z4. The impedance of the circuits at nodes A and B closest to the first common terminal G is denoted as Z5. The impedance of the circuits across the second resistor R2 closest to the first common terminal G is denoted as Z6. For impedance matching, Z1 = (2 * Z0 * Z5). 0.5 *Z6 can also make Z5 and Z6 impedance matched to each other, thereby ultimately matching the impedance of the first common terminal G, the output of the first filter F1, and the output of the second filter F2.
[0094] Furthermore, the first resistor R1 and the second resistor R2 serve to balance the electrical properties. These values can be optimally set using the operating frequency bandwidth of the circuit simulator and the bandwidth required to achieve isolation. A wider bandwidth ensured by isolation results in a lower maximum isolation, while a narrower bandwidth ensured by isolation results in a higher maximum isolation. Therefore, the characteristic impedances Z1 and Z2, and the resistors R1 and R2 can be optimized based on the desired isolation and reflection loss characteristics.
[0095] Another possible implementation, such as Figure 13 The diagram shows a circuit topology of another multiplexer 10 provided in this application. The multiplexer 10 further includes a first duplexer D1 and a second duplexer D2. The input terminal of the first duplexer D1 is used to receive the second communication signal S2. The first output terminal of the first duplexer D1 is connected to the first common terminal G. The second output terminal of the first duplexer D1 is connected to the input terminal of the second duplexer D2. The first output terminal of the first duplexer D1 is used to output the first communication signal S1.
[0096] Another possible implementation is that the first duplexer D1 can be a three-terminal dual-frequency filter. The three-terminal dual-frequency filter can split the second communication signal S2 into two frequency bands: a high-frequency band and a low-frequency band. In this embodiment, the first communication signal S1 should be a high-frequency band signal.
[0097] The second duplexer D2 includes a third filter F3 and a fourth filter F4. Its connection method is as follows: Figure 13 As shown, the output of the third filter F3 is used to output the signal of the third frequency band Band3, and the output of the fourth filter F4 is used to output the signal of the fourth frequency band Band4.
[0098] Figure 14 The insertion loss and isolation characteristics of an isolation boost circuit 101 provided in this application are shown in the figure. Figure 14Taking a center frequency of 2.05 GHz, Z1 = Z2 = 84.1 Ω, Z3 = Z4 = 225 Ω, R1 = 86.1 Ω, and R2 = 225 Ω as an example, the following is an illustration. Figure 14 The bandwidth in the figure indicates that the isolated boost circuit 101 operates at the bandwidth shown in the figure.
[0099] Combination Figure 12 Let's take a look. Figure 14 The first curve represents the insertion loss from the first common terminal G to the output of the first filter F1 and from the first common terminal G to the output of the second filter F2, reflecting the transmission efficiency of the first communication signal S1 from the first common terminal to the two branch ports. The lower the loss (the closer the value is to 0), the better. The second curve represents the isolation between the output of the first filter F1 and the output of the second filter F2, reflecting the signal shielding effect between the two branch ports. The higher the isolation (the smaller the value, i.e., the more negative), the better. Figure 14 Within the medium bandwidth range, the values of the second curve are all less than -30dB, so the multiplexer of this application can significantly improve the isolation of the multiplexer 10.
[0100] Figure 15 A reflection loss diagram of a multiplexer provided in this application. Figure 15 Using a center frequency of 2.05GHz, Z1 = Z2 = 84.1Ω, Z3 = Z4 = 225Ω, R1 = 86.1Ω, and R2 = 225Ω as an example, the following diagram will be provided. Figure 15 The bandwidth in the figure indicates that the isolated boost circuit 101 operates at the bandwidth shown in the figure.
[0101] Combination Figure 12 Let's take a look. Figure 15 The first curve represents the reflection loss at the first common terminal, and the second curve represents the reflection loss at the output terminals of the first filter F1 and the second filter F2. Reflection loss reflects the degree of reflection of the first communication signal S1 at the two branch ports. Figure 15 Within the displayed bandwidth range, the reflection loss of these ports is greater than approximately 30dB, indicating good impedance matching.
[0102] Figure 16 This application provides an insertion loss and isolation characteristic diagram for a multiplexer. The first curve represents the isolation between the output terminals of the first filter F1 and the second filter F2. The second curve represents the insertion loss from the first common terminal G to the output terminal of the first filter F1. The third curve represents the insertion loss from the first common terminal G to the output terminal of the second filter F2. A more negative insertion loss indicates higher transmission efficiency, and a more negative isolation indicates higher isolation.
[0103] contrast Figure 16 and Figure 10It can be seen that the isolation of the multiplexer 10 in this application is improved by about 25 to 35 dB, which greatly improves the isolation of the multiplexer 10.
[0104] like Figure 17 The diagram shown is a circuit topology schematic of a data communication device 1 provided in this application. The data communication device includes a multiplexer 10 and a modem 20. The multiplexer 10 is... Figures 11-13 The multiplexer 10 shown in any of the figures has its output connected to the input of the modem 20, which is used to demodulate the received signal.
[0105] The above detailed description of the data communication device 1 and the analysis of its beneficial effects can be applied to the multiplexer 10 in the embodiments of this application, and will not be repeated here.
[0106] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A multiplexer, characterized in that, include: A first common terminal is used to receive a first communication signal, the first communication signal including signals of multiple frequency bands; A first filter and a first transmission line, wherein a first end of the first transmission line is connected to a first common terminal, a second end of the first transmission line is connected to the input terminal of the first filter, the output terminal of the first filter is used to output a signal of a first frequency band, and the electrical length of the first transmission line is 1 / 4 wavelength corresponding to the center frequency of the first frequency band. The second filter and the second transmission line have a first end connected to the first common end and a second end connected to the input end of the second filter. The output end of the second filter is used to output a signal of the second frequency band. The electrical length of the second transmission line is 1 / 4 wavelength corresponding to the center frequency of the second frequency band. A first resistor is connected between the second end of the first transmission line and the second end of the second transmission line.
2. The multiplexer according to claim 1, characterized in that, The sum of the equivalent resistance of the first transmission line and the equivalent resistance of the second transmission line is equal to the resistance of the first resistor.
3. The multiplexer according to claim 2, characterized in that, The characteristic impedance of the first transmission line is equal to the characteristic impedance of the second transmission line.
4. The multiplexer according to any one of claims 1-3, characterized in that, The multiplexer also includes: A third transmission line is connected between the second end of the first transmission line and the input end of the first filter; A fourth transmission line is connected between the second end of the second transmission line and the input end of the second filter; The second resistor is connected between the input terminal of the first filter and the input terminal of the second filter; The electrical length of the third transmission line is 1 / 4 wavelength corresponding to the center frequency of the first frequency band, and the electrical length of the fourth transmission line is 1 / 4 wavelength corresponding to the center frequency of the second frequency band.
5. The multiplexer according to claim 4, characterized in that, The sum of the equivalent resistance values of the first transmission line, the second transmission line, the third transmission line, the fourth transmission line, and the first resistor is equal to the resistance value of the second resistor.
6. The multiplexer according to claim 5, characterized in that, The characteristic impedance of the third transmission line is equal to the characteristic impedance of the fourth transmission line.
7. The multiplexer according to claim 6, characterized in that, The impedance matching of the first common terminal, the output terminal of the first filter, and the output terminal of the second filter.
8. The multiplexer according to claim 7, characterized in that, The first filter is a dual bandpass filter or a bandpass filter.
9. The multiplexer according to claim 8, characterized in that, The multiplexer also includes: A first duplexer and a second duplexer, wherein the input terminal of the first duplexer is used to receive a second communication signal, the first output terminal of the first duplexer is connected to the first common terminal, the second output terminal of the first duplexer is connected to the input terminal of the second duplexer, and the first output terminal of the first duplexer is used to output the first communication signal.
10. A data communication device, characterized in that, The data communication device includes a multiplexer and a modem as described in any one of claims 1-9, wherein the output of the multiplexer is connected to the input of the modem, and the modem is used to demodulate the received signal.