log-periodic toothed antenna
log-periodic toothed antenna
(OP)
Hello everyone!
Made this antenna in HFSS. Need s11 to be under 10db at 450-970 MHz and 1800-1900 MHz.
Anyone have idea how to achieve it?
Thanks!
Made this antenna in HFSS. Need s11 to be under 10db at 450-970 MHz and 1800-1900 MHz.
Anyone have idea how to achieve it?
Thanks!





RE: log-periodic toothed antenna
You need an element or two with a length matching quarter wavelength of about 700 MHz.
RE: log-periodic toothed antenna
I removed some elements to eliminate 1-1.8 GHz bandwidth.
Was that ok?
RE: log-periodic toothed antenna
http://www.ewh.ieee.org/soc/es/Nov1998/13/LPARRAY/...
If the chosen number of elements is too low, then you'd expect to see holes in the bandwidth; especially at the low end where the percentage bandwidth is worst. For example, if somebody designed a log periodic antenna with only two or three groups of elements (an extreme example to make the point clear), then you wouldn't expect it to work very well. As a general rule, using a larger number of elements should assist in smoothing things out over the bandwidth.
If you're using a log periodic antenna, then you shouldn't bother removing elements to eliminate bandwidth.
You might also be able to tweak the element lengths to move things around a bit. If there's a reflection at 700 MHz, then adjust things so that there's a pair of elements accepting power at that frequency.
Thing is, you're trying to achieve a bit higher than 4:1 bandwidth (450 - 1900 MHz). That might be a stretch. If you can't make it work, then you might have to find a parallel arrangement of two antennas, each covering their own bandwidth.
Disclaimer: I've never designed a log periodic antenna, so this is all based on other somewhat related experience.