Waveguide Coupler
A waveguide coupler is a device capable of transmitting light waves or electromagnetic waves from one waveguide to another, and it is widely used in fields such as communications and radar. The following is a detailed introduction.
Structure and Principle
Basic Structure
It is usually composed of a main waveguide and a secondary waveguide, and coupling is achieved through coupling holes on the common wall of the main waveguide and the secondary waveguide. According to the number and shape of the coupling holes, it can be divided into various structural forms such as single-hole directional couplers, multi-hole directional couplers, and cross-hole directional couplers.
Working Principle
Taking the single-hole directional coupler as an example, when a TE10 wave is input from port 1 of the main waveguide, most of the signal is output from port 2, and a small part of the signal energy is coupled into the secondary waveguide through the circular hole on the common wall. Most of the energy coupled into the secondary waveguide is output from port 3, while very little signal energy is output from port 4. This is because after the electromagnetic field enters the secondary waveguide through the coupling hole, the signals coupled by the electromagnetic field at port 3 superimpose and strengthen each other, while at port 4, they cancel out and weaken each other.
Main Types
Short-Slot Coupler
Also known as the Riblet short-slot coupler, it is a type of narrow-side coupling. It is formed by placing two waveguides in parallel with their narrow sides connected, and a short slot is opened in the middle to realize energy coupling between the waveguides. Its core principle is the superposition effect caused by the different phase velocities of the odd mode and the even mode. Different coupling degrees can be achieved by adjusting the length of the short slot.
Orthogonal Waveguide Coupler
It can provide signals with specific amplitude and orthogonal phase for two output ports, and uses waveguides as transmission lines to transmit signals. Its function is to distribute one signal to multiple channels and isolate the mutual influence between the front and rear stages.
Geometric Waveguide Coupler and Diffractive Waveguide Coupler
In AR (Augmented Reality) display technology, the key component of a waveguide combiner is the coupler, which mainly includes two types: geometric waveguide couplers and diffractive waveguide couplers. Geometric waveguide couplers are mainly composed of devices such as refracting and reflecting elements, and use prisms and mirrors as the main coupling devices; diffractive waveguide couplers mainly rely on diffractive optical elements as couplers, and gratings are the most common type of couplers.
Application Fields
Communications Field
In microwave and millimeter-wave communication systems, it is mainly used for functions such as power division, signal monitoring, and reflection detection.
Radar Equipment
It is used for signal division, synthesis, isolation, etc., to ensure the efficiency and reliability of radar systems.
Microwave Test Equipment
It plays an important role and is mainly used for signal analysis, testing, and monitoring.