TK uses Modal Analysis Software to design Corrugated Horns
There is increasing demand for wideband corrugated horns in the MM and THz regions, and we have manufactured many horns giving 1 to 1.5 bandwidths. They are, however, much harder to design than narrow band horns and their performance can deteriorate at the band edges without careful design.
To improve the performance of our horns we have a licence to use Antenna Software Ltd's CORRUG modal analysis program, which allows us to predict and optimise the performance of our designs. This program takes information on the mechanical di mensions of each slot and fin within the corrugated structure and, through matrix algebra, analyses the progress of an incident TE11 mode on the waveguide end of the structure as the field progresses up the horn. It can thus determine the complex vector field at the aperture of the horn and, by Fourier transforming this field, determine the far-field antenna pattern. The program plots E, H and 45 degree co-polar patterns as well as X-polar patterns. It also estimates the return loss of the structure, which will put a lower bound (best case) value on the expected VSWR.
There is significant computational activity required to analyse the structures, and this effort rises as frequencies increase from the Microwave to the THz regions as the number of fins and slots in horns tends to increase. On the example below there are about 250 elements for the program to deal with in turn.We are running the program on a 200 MHz Pentium Pro Machine and even with this computational power many seconds elapse before each run of the analysis is completed.
The following theoretical plots show the patterns of a horn we have designed to operate from 70 to 110 GHz.
At 70 GHz
AT 90 GHz
And at 110 GHz