RF Directional Coupler: Selection Guide, Benefits & Manufacturers

Introduction

RF directional couplers are essential components that allow signal sampling without disrupting the main signal path. Proper selection based on key parameters ensures high efficiency and low insertion loss. Popular manufacturers in this space include Microlab, KRYTAR, Pulsar Microwave, Vector Telecom, Agilent, Minicircuits, ET Industries, EMC Technology & Florida RF Labs.

Figure is taken from Wikimedia commons. RF Directional coupler will have 4 ports: input port, transmitted port, isolated port, and coupled port.

For the directional coupler illustrated above, the coupled port will exhibit a power level that is 10 dB lower than the power supplied to the INPUT PORT. The transmitted port will have a power level slightly lower than the input port, the difference depending on the insertion loss between these ports. The isolated port is terminated with a 50 Ohm impedance.

Selection Guide

When selecting an RF directional coupler, carefully consider the following key parameters:

• Frequency Range: Choose a coupler that operates within your required frequency band; for example, 1 GHz to 18 GHz for RF/microwave applications.

• Coupling Factor: Determines the amount of signal extracted (e.g., 3 dB, 6 dB, 10 dB, or 20 dB). Lower values extract more power.

• Directivity: Higher directivity (e.g., >20 dB) ensures better isolation between the coupled and main signal paths.

• Insertion Loss: Lower insertion loss (<1 dB) is preferred to minimize signal degradation.

• Power Capacity: Ensure the coupler can handle the required RF power without damage.

• Port Configuration: Decide between bi-directional or uni-directional couplers based on application needs.

• Impedance Matching: Typically 50 Ohm or 75 Ohm depending on system requirements (e.g., 50 Ohm for RF/microwave, 75 Ohm for broadcast applications).

• Connector Type: Choose compatible connectors such as SMA, N-Type, or BNC based on system integration.

Advantages of RF Directional Couplers

Here are some of the benefits of using RF directional couplers:

1. Allows non-intrusive signal sampling for power monitoring and system diagnostics.
2. Helps improve system impedance matching, reducing signal reflections.
3. Efficiently distributes RF power in multi-antenna and phased array systems.
4. Due to high Isolation & Directivity, it ensures minimal interference between forward and reverse signals, improving performance.
5. Supports broadband applications, including wireless communications, radar, and satellite systems.

RF Directional Coupler Manufacturers

The following table lists some of the leading RF directional coupler manufacturers and suppliers:

Conclusion

A well-chosen RF directional coupler enhances system monitoring and signal integrity. Explore trusted manufacturers for the best options.