Directional Couplers and Splitters (Power Dividers) in Wireless Systems.

Directional Couplers and Splitters (Power Dividers) have different names, but they can often be used in the same way. Because power transfer in passive systems is reciprocal, a Splitter can work as a Coupler and a Coupler can work as a Splitter.

Overview – Splitters (Power Dividers).

SPLITTER

Coaxial Splitters usually, have equal power outputs.  Couplers however, may have equal power outputs (-3dB couplers) or may tap off just a fraction of the power in a coupled port.

Directional Couplers.

The coupled port of a coaxial directional coupler is usually situated on the side and is near the common port.

A directional coupler will be typically 3dB (50,50) , 6dB (75,25), 7dB (80,20), 10dB (90,10) or 20dB (99,1) . The figures in brackets show the % split in the power.

   COUPLERS

Wireless System Application.

Typical application of a directional coupler or a splitter in a wireless system would be to connect two antennas to a radio. The radio would be connected to the common port and the antennas would connect to the thru and coupled ports. Note that if you attach the radio to the thru port you get very little if any power out of the coupled port.

These terms, ‘common port’ and ‘thru port’ are often replaced by numbers or names like ‘IN’ and ‘OUT’, but it is better to avoid these terms with wireless because the power flow is bidirectional.

The through loss of a: 6dB coupler is 1dB, 10dB coupler is 0.5dB and 20 dB coupler is less than 0.1dB.

So, in practice, you would hardly notice the power loss in the thru port with 10dB and 20dB couplers. The tapped off power may still be just enough for it to be useful.

Directional Couplers and Splitters (Power Dividers) – DATA.

Typical Coupler Specifications.
>Frequency Range: 0.8 – 2.5GHz.
Coupling Faltness: +/-0.5dB max.
Thru Loss: 0.25dB max.
Directivity: 20dB min.
VSWR: 1.2:1 max.
Power rating: 50 W.

Typical Plots of Through Loss and Return Loss.