I. Technical Positioning and Core Functions

　　In a phased array radar system, the microwave power divider is a core passive device connecting the radar signal source, T/R (transmit/receive) components, and the antenna array. It directly determines beamforming accuracy and target detection performance. Its core functions include:

　　* **Multi-channel signal distribution:** Distributing the radar transmitter's radio frequency signal (pulse or continuous wave) evenly to hundreds to tens of thousands of T/R components. Combined with phase shifters, this enables rapid electrical scanning of the beam (switching speed ≤1μs), meeting multi-target tracking requirements.

　　* **Received signal synthesis:** In receive mode, it combines the echo signals collected by each T/R component to the radar receiver. Power synthesis improves the signal-to-noise ratio (SNR) of weak target signals, enhancing long-range detection capabilities.

　　* **Multi-beam and beamforming adaptation:** Through unequal or matrix-style power divider structures, it generates multiple simultaneous beams (e.g., search beam + tracking beam) or achieves low sidelobe beamforming (sidelobe suppression ≥30dB), reducing clutter and interference.

　　Its operating frequency band must cover the mainstream frequency bands of phased array radar (L-band: 1-2GHz; S-band: 2-4GHz; C-band: 4-8GHz; X-band: 8-12GHz; Ka-band: 26.5-40GHz; millimeter wave: 60-110GHz) to adapt to different detection scenarios (such as long-range early warning, fire control, and imaging).

　　II. Key Requirements for Adapting to Phased Array Radar Ultra-High Amplitude and Phase Consistency Radar beamforming is extremely sensitive to channel consistency. The amplitude imbalance of each output port of the power divider must be ≤0.05dB, and the phase imbalance must be ≤1° (across the entire frequency band). Otherwise, it will lead to increased beam sidelobes (e.g., a 2° phase deviation can reduce sidelobe suppression by 8dB), increasing the risk of interference. For example, in X-band fire control radar, the consistency error must be controlled within 0.03dB/0.5° to ensure target angle accuracy ≤0.1mrad.

　　Wide Instantaneous Bandwidth and High Group Delay Stability

　　To improve radar range resolution (resolution = speed of light / (2 × bandwidth)), the power divider needs to have a wide instantaneous bandwidth (relative bandwidth ≥ 20%, some imaging radars require ≥ 50%), while the group delay fluctuation must be ≤ 5ps to avoid increased target range measurement errors due to echo signal distortion. For example, Ka-band imaging radars have an instantaneous bandwidth covering 30-40GHz, and the group delay fluctuation needs to be controlled within 3ps to ensure a resolution of 0.015m.

　　High Power Capacity and Pulse Tolerance

　　Radar transmissions are mostly pulse-based (pulse width 100ns-10μs, duty cycle 1%-5%), and the power divider needs to withstand a combined load of high pulse power (1kW-100kW) and low average power (10W-500W). For example, S-band long-range early warning radars require a power divider pulse power capacity ≥ 50kW, an average power ≥ 200W, and no pulse leading-edge distortion (overshoot ≤ 5%). High Integration and Lightweight Design: Phased array antennas have extremely high element density (e.g., airborne radar arrays have ≥10,000 elements). Power dividers need to be integrated with T/R modules and phase shifters, with a single-channel power divider volume ≤1cm³ and weight ≤2g. Multi-channel integration can be achieved using LTCC (Low Temperature Co-fired Ceramic) or SiP (System-in-Package) processes; for example, an 8-channel integrated power divider has a volume of only 4cm × 2cm × 0.5cm.

　　Strong Environmental Adaptability: The antennas must be adaptable to complex radar operating environments: airborne scenarios require tolerance to temperature cycling from -55℃ to +85℃ and 15g vibration (20-2000Hz); shipborne scenarios require protection against salt spray (5% salt spray concentration) and mold; ground scenarios require tolerance to a wide temperature range from -40℃ to +70℃, with an MTBF (Mean Time Between Failures) ≥5×10⁵ hours.

　　III. Core Design Technologies and Optimization Directions

　　Topology Selection

　　Large-Scale Array Scenarios: A tree-shaped cascaded power divider is used, combined with a multi-section impedance transformation network (3-6 sections) to broaden the bandwidth. Simultaneously, a symmetrical layout reduces amplitude and phase deviation, suitable for long-range early warning radars with 1000+ channels, achieving a VSWR ≤ 1.1.

　　Multi-Beam Scenarios: Butler or Blass matrix power dividers are used. For example, a 16×16 Butler matrix can generate 16 orthogonal beams, with isolation ≥ 35dB, suitable for shipborne multi-functional radars (such as integrated search/track/guidance systems).

　　Low Sidelobe Beamforming Scenarios: Unequally divided Wilkinson power dividers are used. Specific amplitude weighting is achieved by adjusting the power distribution ratio of each channel (e.g., 1:1.2:1.5), and a phase shifter is used to achieve beam sidelobe suppression ≥ 40dB, suitable for anti-jamming radars.

　　Materials and Process Optimization

　　High-Frequency Substrate: Low-loss, high-stability materials are selected, such as Rogers RT/duroid 5880 (εr=2.2, tanδ≤0.0009, suitable for X/Ka bands) and aluminum nitride ceramic (εr=9.8, thermal conductivity ≥170W/(m・K), suitable for high-power applications);

　　Metal Layer: Gold-plated copper foil (thickness ≥25μm) or silver paste sintering process is used to reduce conductor loss (≤0.05dB/cm) and improve corrosion resistance (gold plating thickness ≥5μm is required for shipboard applications);

　　Integration Process: LTCC multilayer wiring (≥8 layers) is used to achieve heterogeneous integration of multi-channel power dividers and phase shifters, or GaN technology is used to monolithically integrate the power divider and T/R module, reducing link loss (total loss is reduced by 0.3-0.5dB after integration).

　　Performance Enhancement Design

　　Phase Compensation: Microstrip delay lines are introduced into the power divider branch paths to compensate for phase differences between different channels, ensuring phase consistency across the entire frequency band is ≤0.5°;

　　Pulse Protection: A PIN diode limiter is integrated at the input port. When the pulse power exceeds a threshold, it automatically conducts shunt to prevent the power divider from burning out (protection response time ≤10ns);

　　Thermal Management: High-power models employ a microchannel heat dissipation structure, using coolant circulation to keep the temperature below 60℃, adapting to the high average power requirements of X-band fire control radar.

　　IV. Typical Application Scenarios

　　Shipborne Multi-functional Phased Array Radar (e.g., US AN/SPY-1)

　　Utilizing an X-band tree-cascaded power divider, the 6MW peak power transmit signal is distributed to 4352 T/R modules. The power divider amplitude consistency is ≤0.04dB, and phase consistency is ≤0.8°. Combined with a phase shifter, it achieves 360° beam scanning without blind spots, capable of simultaneously tracking 100+ air/surface targets at a detection range of up to 400km.

　　Airborne fire control phased array radar (e.g., the J-20 active phased array radar)

　　Utilizes a Ka-band 8-channel LTCC integrated power divider, with a size of only 3cm×2cm×0.4cm and a weight ≤10g. It boasts an instantaneous bandwidth coverage of 30-36GHz (relative bandwidth 20%), group delay fluctuation ≤4ps, supporting high-resolution imaging and multi-target engagement capabilities. Target detection range ≥200km, angular accuracy ≤0.05mrad.

　　Ground-based long-range early warning radar (e.g., my country's YLC-8E radar)

　　Utilizes an S-band Blass matrix power divider (32×32 matrix), with a pulse power capacity ≥60kW and an average power ≥300W. Through multi-beam synthesis, it achieves long-range detection of stealth targets (detection range ≥500km). The power divider's low sidelobe design (sidelobe suppression ≥35dB) effectively counters active interference, ensuring detection performance in complex electromagnetic environments.

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