The present invention relates generally to improvements in transmission lines and more particularly to new and improved transmission lines which can tolerate damage from ordnance fragments without severe degradation of performance.
Those concerned with the development of radar systems have long recognized the need for a transmission line or waveguide which can tolerate damage from ordnance fragments without severe degradation of performance. Specifically, prior art transmission lines and waveguides, when hit by fragments from sources such as exploding ordnance, tend to generate holes on the order of 1 inch or less in diameter. These holes, in and of themselves, tend not to have much effect on the VSWR of the transmission line or waveguide because their diameters are generally small compared to the wavelength of the electromagnetic energy propagating within the line. However, the inwardly-protruding, jagged metal edges generated by the act of penetration by the projectile will, in fact, decrease the breakdown voltage during radar transmissions. A decreased breakdown voltage in the waveguide will substantially increase the potential for arcing and degrade the voltage standing wave ratio (VSWR). Such arcing will not only lower the forward transmission efficiency of the waveguide but will also send potentially destructive energy traveling back toward the output stages, e.g., magnetron tube, in the radar transmitter.