FSS – frequency selective surfaces

FSS are filters resulting from regular patterns of metallic grids printed on an insulating substrate which, by their design, either allow specific frequencies of incident radiation to be either reflected or to be transmitted though the filter with minimal absorbtion. Trackwise’ capability of precision imaging and etching of large areas of flexible PCB substrate – up to 2800mm* 610mm – is ideal for frequency selective surfaces. “An incident plane wave strikes the filter and causes the electrons in the metal to oscillate. If a large portion of the incident energy is absorbed by these electrons they reradiate and cancel the initial field, causing the transmittance through the filter to be low. In this case, the electrons will re-radiate toward the left and cause the reflected wave amplitude to be high. If only a small portion of the incident power is absorbed no such cancellation occurs and the transmittance will be high. In general the transmittance through the filter is a function of frequency; in other words, the electrons in the metal will absorb and re-radiate some wavelengths with higher efficiency than others. The shape of the transmittance curve depends on the pattern etched into the metal filter, and we can etch various patterns into our metal to obtain filters of varying behaviour.” Everything You Ever Wanted to Know About Frequency-Selective Surface Filters but Were Afraid to Ask. Benjamin Hooberman, May 2005.

For more information on FSS – frequency selective surfaces talk to Trackwise Ltd