• What is a coupler?

A coupler is a key passive device in RF/microwave systems, primarily used for signal sampling, power distribution, or monitoring. Its core functions include directional coupling (extracting a portion of the signal), power division (splitting the input signal into multiple paths), and signal isolation (preventing interference between ports). In fields such as communications, radar, and testing and measurement, couplers directly affect system performance and signal integrity, making them an indispensable component in the RF chain.

• Types of Couplers

Directional coupler: Couples signals in one direction, such as forward or reverse waves, commonly used for power monitoring.

Dual-directional coupler: Extracts both incident and reflected waves, suitable for standing wave ratio (VSWR) measurement.

Hybrid coupler: Provides 90° or 180° phase difference, used for balanced amplifiers, mixers, and so on.

• Main Technical Parameters

When selecting a coupler, the following parameters should be considered:

-**Coupling** (e.g., 20dB, 30dB), which determines the proportion of the sampled signal.

-**Insertion loss** (the lower the better), which affects system efficiency.
- **Directivity/Isolation** (the higher, the more precise the signal separation).
- **Frequency range** (e.g., 0.5-6GHz), which needs to match the application requirements.
- **Power handling** (e.g., 100W CW), to ensure long-term stable operation.

• Typical Application Scenarios

**5G Base Stations**: Monitor power amplifier output and optimize signal quality.
- **Radar Systems**: Detect transmission power in real time to ensure safe operation.
- **Laboratory Testing**: Used for spectrum analyzers, network analyzers, and other equipment.
- **Medical RF Devices**: Control energy output and improve treatment accuracy.

• Future Technology Trends

Future couplers will develop towards higher integration (such as MMIC technology), wider bandwidth (covering Sub-6GHz to millimeter waves), and intelligence (integrating sensors and digital interfaces) to meet the needs of emerging fields such as 5G and satellite communications.