RF splitters and combiners are key passive components used to distribute or combine signals in RF systems. They play an important role in wireless communications, radar, test equipment, and other applications that require precise control of signal distribution and combination. The following is a detailed introduction to RF splitters and combiners, including their working principles, main types, and design considerations.

　　RF Splitter

　　Function:

　　Power distribution: Splits an input signal into two or more equal or unequal output signals.

　　Isolation: Ensures high isolation between output ports to reduce mutual interference.

　　Phase relationship: Some types of splitters can maintain a specific phase relationship between output signals.

　　Application:

　　Used in multi-antenna receiving systems such as distributed antenna systems (DAS) and multiple-input multiple-output (MIMO) systems.

　　In test equipment, it is used to monitor different characteristics of the same signal simultaneously.

　　Main types

　　Wilkinson Power Divider:

　　Features: Low insertion loss, high isolation, good phase matching.

　　Structure: It consists of two branches of equal impedance, each branch is connected to a quarter-wavelength matching resistor to absorb unbalanced signals.

　　Branchline Coupler:

　　Features: It provides 90-degree phase shift and is suitable for applications such as orthogonal modulation and demodulation.

　　Structure: Power distribution is achieved at the intersection through two mutually perpendicular transmission lines.

　　Microstrip Splitter:

　　Features: Miniaturized design, easy to integrate into PCB.

　　Structure: It is manufactured using microstrip line technology on printed circuit boards and is suitable for high-frequency band applications.

　　Hybrid Couplers:

　　Features: In addition to power distribution, it can also be used to monitor signal levels.

　　Structure: For example, a 3 dB bridge can evenly divide power and maintain a certain phase difference.

　　RF Combiner

　　Function:

　　Power synthesis: Combine signals from multiple input ports into one output signal.

　　Matching network: Ensure impedance matching of each input port to optimize transmission efficiency and reduce reflections.

　　Isolation: Prevents unwanted coupling or interference between input signals.

　　Applications:

　　In base stations, multiple transmitter signals of different frequency bands are combined onto one antenna.

　　In mobile communication devices, signals of Wi-Fi, Bluetooth and other wireless technologies are integrated.

　　Main types

　　Wilkinson Combiner:

　　Features: Same as power divider, but for reverse operation.

　　Circulator:

　　Features: Unidirectional transmission characteristics, signals can only be transmitted from one port to the next port in a predetermined direction.

　　Applications: Used as an isolator to protect amplifiers from reflections, or to build a duplexer.

　　Magic-T:

　　Features: Combining the advantages of E-plane and H-plane T-type connectors, it can effectively combine signals from different directions without reflection.

　　Applications: Suitable for power synthesis and signal separation in waveguide systems.

　　Design considerations

　　Frequency range: Select products that meet the operating frequency range to ensure stable performance throughout the frequency band.

　　Insertion loss: Minimize insertion loss to maintain high signal strength.

　　Isolation: For multi-port devices, high isolation helps reduce interference between different signals.

　　Phase consistency: In some applications, such as phased array antenna systems, a strict and consistent phase relationship needs to be maintained.

　　Power handling capability: Select the appropriate model according to the maximum expected power level, especially in transmitter applications.

　　Environmental adaptability: Equipment used outdoors should have a good level of protection, such as waterproof and dustproof.

　　Manufacturing process

　　The production of RF splitters and combiners involves precise microwave engineering technology and material science. Common manufacturing processes include:

　　Microstrip and stripline technology: used to build efficient miniaturized circuits.

　　Surface mount technology (SMT): suitable for mass production and automated assembly.

　　Ceramic substrates and metal shields: provide excellent electrical performance and mechanical stability.

　　Welding and brazing: ensure a strong and reliable electrical connection between components.

　　Testing and calibration: The finished product must undergo rigorous testing to ensure that it meets the specifications and is adjusted to the best performance during the calibration process.

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