RFRidge Waveguide and its advantages and disadvantages
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As we know, the bandwidth of a rectangular waveguide is relatively limited.
The TE10 mode is the dominant mode in a rectangular waveguide, and it has a cutoff wavelength of approximately 2a. Therefore, the dimension of the waveguide along the X direction should be equal to or less than 2a for the dominant mode of propagation. For an a/b ratio equal to two (where ‘a’ is the broad dimension and ‘b’ is the narrow dimension), the next higher-order mode will be TE20 or TE01, which will have a cutoff wavelength equal to either 2b or a.
(As a=2b, i.e., broad dimension = 2 * (narrow dimension)). But the dimensions of the waveguide are chosen such that only the dominant mode can propagate.
Image alt: Ridge Waveguide
The ridge waveguide is created using a rectangular waveguide by adding conducting ridges along the center of the top and bottom walls. Ridge waveguides are characterized by addition of conducting ridges within a standard waveguide structures.
An inward perturbation of the waveguide walls at a position of high E (electric field) will lower the cutoff frequency. Conversely, at a position of high H (magnetic field), it will raise the cutoff frequency.
These ridges will lower the cutoff frequency of the dominant mode and raise the cutoff frequency of the next higher-order modes. Consequently, a higher range of single-mode operation can be achieved using this technique, resulting in a wider bandwidth of operation.
The following are the advantages and disadvantages of the ridge waveguide compared to a conventional waveguide of the same dimensions.
Advantages of Ridge Waveguide
- It is used for impedance matching purposes. This is because it helps decrease the characteristic impedance of the guide.
- It increases the bandwidth of operation.
- The inclusion of ridges lowers cutoff frequency of dominant mode. Hence it allows low frequency operation without compromising on waveguide’s physical dimensions.
Disadvantages of Ridge Waveguide
- It will have less power handling capability compared to a rectangular waveguide of the same dimensions.
- The intricate design of ridge waveguides specially its double ridged variant, can complicate manufacturing processes. This increases production costs.
Conclusion
Understanding these factors is essential for engineers and designers when considering ridge waveguides for specific applications, ensuring that the benefits align with the system requirements and constraints.
