The **CA2120-9-R** is a high-performance, broadband directional coupler manufactured by **Modelithics** or similar microwave component specialists (often associated with API Technologies / Inmet). These parts are critical in RF (Radio Frequency) and microwave systems for signal monitoring and leveling. --- ### Technical Specifications The "9" in the part number typically refers to the coupling value (9 dB). Below are the general specifications for this series: | Parameter | Typical Value | | :--- | :--- | | **Frequency Range** | 2.0 GHz to 12.4 GHz (Broadband) | | **Coupling Nominal** | 9.0 dB (± 1.0 dB) | | **Insertion Loss** | < 0.8 dB (excluding coupled power) | | **Directivity** | > 18 dB | | **VSWR (Maximum)** | 1.35:1 | | **Power Rating** | 50 Watts (Average), 3kW (Peak) | | **Impedance** | 50 Ohms | --- ### Key Internal Components & Materials As a passive microwave component, the CA2120-9-R relies on precision mechanical and material engineering rather than active semiconductors: 1. **Coupling Structure:** Utilizes a **stripline** or **microstrip** design where two transmission lines are placed in close proximity. Electromagnetic fields transfer a specific amount of energy (9 dB) from the main line to the coupled port. 2. **Housing:** Usually constructed from **Passivated Stainless Steel** or Aluminum with a specialized finish to ensure shielding and durability. 3. **Dielectrics:** High-stability Teflon (PTFE) or ceramic-filled substrates are used to maintain constant impedance across a wide temperature range. 4. **Connectors:** Standard **SMA Female** connectors (complying with MIL-C-39012) are used for low-loss signal interface. --- ### Functional Port Diagram A directional coupler like the CA2120-9-R has four ports (though the fourth is often internally terminated): * **Input Port:** Where the main RF signal enters. * **Output Port:** Where the majority of the signal exits (Main Line). * **Coupled Port:** Where 1/8th of the power (9 dB down) is sampled. * **Isolated Port:** Internally terminated to ensure the coupler only samples signals moving in one direction. --- ### Common Applications * **Power Monitoring:** Measuring the output power of a transmitter without interrupting the main signal path. * **Reflectometry:** Measuring Return Loss or SWR by sampling reflected waves. * **Signal Leveling:** Providing a feedback loop to an Automatic Gain Control (AGC) circuit. * **Antenna Testing:** Sampling the signal sent to an antenna for diagnostic purposes.