Satellite Communication Dedicated RF Power Splitter/Combiner Technology and Applications

　　I. Specific Requirements for Satellite Communication Scenarios

　　The requirements for RF splitters/combiners in satellite communication systems (including ground stations, onboard equipment, and user terminals) differ significantly from other scenarios, focusing on three core dimensions: "fidelity transmission of weak signals," "low loss across the entire link," and "extreme environment tolerance."

　　Signal Characteristics Adaptation: Satellite downlink signals are weak (typically -90 to -120 dBm), requiring splitters/combiners to retain signal power to the maximum extent possible, avoiding additional losses that could degrade the signal-to-noise ratio; uplink signals need to be stably synthesized to prevent multi-channel crosstalk from affecting transmission efficiency.

　　Frequency band coverage requirements: Compatibility with mainstream satellite communication frequency bands is required, including C-band (3.7~4.2GHz, commonly used by ground stations), Ku-band (11.7~12.75GHz, broadband satellites), and Ka-band (17.7~21.2GHz, high-throughput satellites). Some low-Earth orbit satellite systems also need to cover the L-band (1~2GHz). Wideband devices must achieve low-loss transmission across the entire 2~20GHz frequency band.

　　Extreme environmental challenges: Ground station equipment must withstand a wide temperature range of -40℃ to +65℃, strong winds and sandstorms (IP66 protection), and lightning strikes. Onboard equipment must withstand alternating temperatures of -55℃ to +125℃, space radiation (total dose ≥100krad), vacuum environments (below 10⁻⁵Pa), and strong vibrations during launch (1000Hz/20g).

　　II. Satellite-Grade Standards for Core Performance Indicators

　　1. Electrical Performance Indicators (Far Exceeding Industrial-Grade Requirements)

　　Insertion Loss (IL): Ground station C/Ku band splitters IL≤0.3dB (2 channels); Ka band IL needs to be controlled ≤0.5dB due to increased high-frequency loss; IL fluctuation of onboard devices across the entire temperature range (-55℃~+125℃) ≤±0.1dB to avoid signal attenuation fluctuations caused by temperature.

　　Isolation: Multi-channel combiners (e.g., 4-channel combiners) have an isolation ≥35dB to prevent uplink signal crosstalk between different user terminals. Especially in Ka band high-throughput satellite systems, isolation needs to be increased to ≥40dB to avoid adjacent channel interference.

　　Phase Consistency: For splitters配套 with phased array antennas, the phase difference between each port is ≤±1° (Ka band) to ensure beamforming accuracy; the phase temperature coefficient is ≤0.01°/℃ to reduce the impact of temperature on phase stability.

　　VSWR: Input/output port VSWR ≤ 1.25 (full band); for high-power ground station scenarios (e.g., 100W uplink), VSWR must be ≤ 1.2 to avoid reflected power damaging the front-end power amplifier.

　　2. Environmental and Reliability Indicators (Satellite-level Certification Requirements)

　　Radiation Resistance: Onboard devices must pass total dose radiation testing (100 klad (Si)) and single-event effect testing, with IL change ≤ 0.2 dB after radiation and no functional failure; ground station equipment must be resistant to electromagnetic radiation (compliant with EN 302 307 standards), with power fluctuation ≤ ±0.5 dB in strong electromagnetic environments (e.g., radar interference).

　　Thermal Environment Adaptability: Onboard devices employ passive heat dissipation design, with an operating junction temperature ≤ 105℃, and no risk of thermal runaway in a vacuum environment (10⁻⁵ Pa); ground station equipment must support low-temperature startup at -40℃, with stable performance within 30 minutes after startup.

　　Mechanical reliability: Spaceborne components passed random vibration tests (10~2000Hz/20g) and impact tests (1000g/0.5ms) without structural deformation; ground station outdoor equipment passed IP66 protection tests, showed no corrosion after 500 hours of salt spray testing, and exhibited no degradation in electrical performance.

　　III. Satellite Communication Dedicated Technical Solution Design

　　1. Topology Selection and Optimization

　　Low-Loss Ground Station Solution: Wilkinson topology is preferred, with the following optimizations to reduce losses:

　　Transmission lines use oxygen-free copper strips (conductivity 5.8×10⁷ S/m) with gold plating (thickness ≥3μm) to reduce high-frequency skin effect losses;

　　Isolation resistors are high-frequency thin-film resistors (operating frequency ≥20GHz), with power redundancy designed to be 3 times the actual power consumption to avoid increased losses due to overheating;

　　The substrate uses low-dissipation high-frequency materials (such as Rogers RO4003C, tanδ=0.0027) to reduce dielectric loss, especially in the Ka band, reducing additional losses by 0.1~0.2dB.

　　Spaceborne Miniaturization Solution: The branch-line coupler topology is implemented using LTCC (Low Temperature Co-fired Ceramic) technology, offering the following advantages: Multi-layer integrated structure: Transmission lines, resistors, and capacitors are integrated within the ceramic substrate, reducing the volume by 60% compared to traditional PCB solutions (e.g., a 4-way splitter ≤ 15mm × 10mm × 3mm); High thermal conductivity of the ceramic substrate (Al₂O₃ ceramic approximately 20W/m・K), suitable for spaceborne passive heat dissipation requirements and preventing temperature accumulation; Low dielectric loss tangent (tanδ < 0.001), with radiation loss ≤ 0.1dB in the Ka band, meeting the requirements for weak signal transmission in space.

　　2. Satellite-Grade Adaptable Material System: Spaceborne Component Materials: The outer shell uses titanium alloy (low density, radiation resistant); the transmission lines are plated with pure silver (corrosion resistant, low loss); and the solder joints use gold-tin alloy (melting point 280℃, adaptable to a wide temperature range), avoiding the brittleness of traditional tin-lead solder at -55℃.

　　Ground station outdoor equipment materials: The outer shell is made of 316L stainless steel (resistant to wind and sand abrasion, and salt spray); the internal transmission lines use silver-plated copper cores (low loss); and the connectors are SMA-J type sealed connectors (IP66 protection, waterproof and dustproof), suitable for harsh outdoor environments.

　　3. Extreme Environment Resistant Structural Design

　　Spaceborne Thermal Management: Transmission lines are laid out to conform to the heat dissipation path of the ceramic substrate. Gold thermal pads are used between key heat-generating components (such as isolation resistors) and the substrate to keep local temperatures below 85°C.

　　Ground Station Lightning Protection Design: A gas discharge tube (breakdown voltage 60V) is connected in series at the splitter input port, and a varistor is connected in parallel to resist lightning strikes (10/700μs waveform, 10kA current) to prevent device damage.

　　Vibration Hardening: The internal components of spaceborne devices are encapsulated using a potting process (silicone rubber potting, hardness 50 Shore A) to fix transmission lines and components and prevent poor contact caused by vibration. Metal vibration damping brackets are installed inside the ground station equipment to reduce vibration transmissibility in the 10~2000Hz frequency band (≤20%). IV. Satellite Communication-Specific Testing and Certification

　　1. Core Test Items (Compliant with Satellite Communication Standards)

　　Ground Station Testing:

　　Full-Band IL and Isolation Test: Using a vector network analyzer (VNA, such as Keysight N5247A) covering 2~20GHz, one test point is taken every 100MHz to ensure that the full-band performance meets the standards;

　　High-Power Aging Test: Continuously operate at rated power (e.g., 50W CW) for 1000 hours, with IL fluctuation ≤ ±0.1dB, verifying long-term stability;

　　Rain Attenuation Compensation Test: Simulate a heavy rain environment (rainfall 100mm/h), test the IL change of the splitter in a humid environment, which must be ≤0.1dB to ensure stable communication of the ground station in rainy weather.

　　Spaceborne Device Testing:

　　Vacuum Thermal Cycling Test: The device was cycled 50 times (-55℃ to +125℃) within a vacuum chamber (10⁻⁵Pa), with each cycle lasting 2 hours. After the test, the IL change was ≤ ±0.15dB.

　　Radiation Test: The device was irradiated with a total dose of 100krad (Si) from a Cobalt-60 radiation source. After the test, the phase uniformity change was ≤ ±0.5°, with no functional failure.

　　Single-Particle Effect Test: A heavy-ion accelerator was used to simulate a single-particle environment in space, verifying that the device exhibited no latch-up when the LET (linear energy transfer) value was ≥80MeV・cm²/mg.

　　2. Key Certification Standards

　　Ground station equipment must comply with ETSI EN 302 307 (Satellite Earth Station RF Equipment Standard) and FCC Part 25 (US Satellite Communication Equipment Certification); Onboard components must comply with ECSS (European Space Standardization Cooperation) standards, such as ECSS-Q-70-02 (Component Selection and Control) and ECSS-E-20-07 (Mechanical Environment Testing).

　　V. Typical Application Scenarios and Cases

　　1. Ground Station Multi-Band Combiner (C/Ku Dual-Band)

　　Application Requirements: The ground station receiving antenna must simultaneously receive C-band (3.7~4.2GHz) and Ku-band (11.7~12.75GHz) satellite signals, which are then combined and transmitted to the demodulator. Requirements include IL ≤ 0.4dB (C-band), ≤ 0.5dB (Ku-band), isolation ≥ 35dB, and VSWR ≤ 1.25.

　　Technical Solution: Employs a dual-band Wilkinson combiner topology, using an RO4003C substrate, gold-plated transmission lines, and 2GHz/1W thin-film resistors for isolation. The housing is made of 316L stainless steel with IP66 protection.

　　Application Results: Signal-to-noise ratio loss after combining ≤0.3dB, supports 24-hour continuous operation, exhibits no performance degradation in heavy rain or sandstorms, and is suitable for multi-band reception requirements of ground stations.

　　2. Spaceborne Phased Array Antenna Splitter (Ka Band)

　　Application Requirements: Low-Earth orbit satellite phased array antennas need to distribute one RF signal to eight antenna elements, operating frequency band 27~30GHz, size ≤20mm×15mm×5mm, IL≤0.6dB, phase coherence ≤±1.5°, and total radiation dose tolerance 100krad (Si).

　　Technical Solution: LTCC process branch-line coupler topology, Al₂O₃ ceramic substrate, silver-plated transmission lines, titanium alloy housing, and vibration-resistant silicone rubber encapsulation.

　　Application Results: Full-temperature range IL fluctuation ≤ ±0.1dB, phase difference ≤ ±1°, weight only 3g, suitable for lightweight spaceborne applications and extreme environment resistance requirements, already applied to low-Earth orbit broadband satellite constellations.

　　VI. Technology Development Trends: Ultra-wideband multi-band integration: Development of splitters/combiners covering the entire L/C/Ku/Ka band (1~30GHz), achieving wide-band low-loss (IL≤0.5dB) through multi-section matching networks, adapting to the multi-band compatibility requirements of satellite communication.

　　Intelligent Monitoring Integration: Miniature power sensors (such as the ADI AD8362) and temperature sensors are integrated into ground station devices. Real-time data is transmitted to the ground station monitoring system via an RS485 interface, enabling early warning of abnormal losses (e.g., triggering an alarm when IL increases by ≥0.3dB), improving operational efficiency.

　　Spaceborne Radiation Resistance Upgrade: Transmission lines are made of GaN (Gallium Nitride) material, increasing the total radiation dose resistance to 200 krad (Si), suitable for the strong radiation environment of deep space exploration satellites (such as Mars exploration), while simultaneously reducing device power consumption (30% lower than traditional solutions).

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