In recent years, the accuracy of electromagnetic simulation software at higher frequencies has improved dramatically, meaning that a Ka-band component in WR-28 (WG22) is scarcely more difficult to design, nor takes any longer to simulate, than a C-band part in WR-137 (WG14). If design costs are amortised over a production run then only the smaller volumes that are traditionally ordered at millimetre-wave frequencies will justify a higher cost being passed onto the customer. However, once the industry adapts to the idea that a higher frequency does not necessarily imply a higher price ticket, then volumes will increase and economies of scale should serve to equalise the design costs in the two bands.
Table 1: Table of rectangular waveguide dimensions for primary bands from C-band to Ka-band, highlighting the two bands discussed in this article.
Table 1 gives the frequency ranges and dimensions of the main band designations for rectangular waveguide (the even-numbered ones in the European WG types), with the data for WR-137 and WR-28 highlighted in pink. Since waveguide sizes were originally defined in inches, the metric sizes have been rounded to the nearest 0.01 mm. Figure 2 gives an idea of the difference in scale between the two waveguide sizes – roughly 5:1 in each dimension.