论坛上关于PBG/EBG LHM/DNG的讨论3

fff

（by simon_tse）

Frequency Band Selection. Tripole or Fractal for LHM

Hi, Totokevin! Yes, it has been a long time since we last chat.

Firstly, were you there at the IEE Metamaterial Conference on Monday? Yo
ur supervisor

was holding the chair for the morning session, I thought you might be th
ere too. Two

colleagues of yours were presenting there, they are Greek students. I wa
s there!

Yes, your group is working on AMC. Moreover, the AMC exhibits multiband  
nature.

However I haven''t seen any work they presented of an antenna place clos
e to the

surface. The data were mainly of surface-wave measurement to show the ba
ndgaps.

Yes, both fractal and convoluted implementation can reduce the bandgap f
requency.

The convoluted however will reduce the bandwidths of the bandgap. I don'
't know

about the fractal''s but I would assume it will have similar reduction i
n bandwidth

performance. One other thing though, Fractals can be more difficult to e
tch in practice

than say the convoluted one, because the fractals segments can be very s
mall. But the

advantage is that fractals have been around for years and so the theorie
s are there.

While the convoluted elements are based on systematic investigation.

Of course there will be differences between shape+surface waves and shap
e+plane

waves. The bandgaps tend to drift from plane wave incident normally (0 d
eg) to it  

incident at 90 deg. In my opinion, if your device is used for surface wa
ve suppression,

then trust your surface wave measurement data. Since it is called the Ar
tificial Magnetic

Conductor, I would expect it is for antenna places close to it acting as
a magnetic gnd

plane. Then in this case, trust your plane wave measurement data. Howeve
r, this is not

even correct. Because, when an antenna is placed close to it and resonat
ing within the

bandgap frequency, it will not operate within the bandgap frequency, but
slightly drifted.

The true operating frequency of that antenna on such surface is based on
one last

experimentation called the Frequency Band Selection. Place a tunable dip
ole antenna

close to the surface and measure the frequency bandwidth of the antenna  
that exhibit

VSWR < 2. The result obtained from this experiment is equally important  
and will be

more of interest to those commercial people. They aren''t really concern
about the AMC,

but how the antenna performs on such surfaces.

If your thesis is going to relate the latest Metamaterials, then yes "LH
M/DNG" is a sure

topic of discussion. Have you looked into your tripole or fractal elemen
ts if they exhibits

negative mu and and epsilon? If so, then sure this will be your chapter  
on LHM/DNG.

In regards to their background knowledge, I have had some experience wit
h them. But

I am no expert and confidence into giving you a detailed explanation. I  
hope you did

attend the conference on Monday in which we saw lots of these well expla
ined theory

repeatedly. I will leave you with the latest publications at the end whi
ch you might have

read already.

I haven''t heard of Yiannis moving. It would be obvious that he will be  
taking the whole

group with him. I know many groups are not surviving due to lack of fund
ings. Do keep

in touch.

P.S. Have you publised any works so far? Could you let me know if any, I
would be very

interested in reading your work.

References:

Metamaterial special issue, IEEE Transactions on Antennas and Propagatio
n, Vol 51,  

Issue 10, Oct. 2003, pp 2546 and on.


--
如果你要找superfighter，请按一下步骤进行：
曲线方式：bbs.hit.edu.cn->学术科学->微波技术与应用
直线方式：dreamfield@hit.edu.cn


※ 来源:·哈工大紫丁香 bbs.hit.edu.cn·[FROM: 219.217.250.144]