Hi to all

In the line of my theses I have designed an antenna,
which I consider as prototype(?) and named it D-Dimond1.

The antenna was designed, simulated and examined
(and propably will be constructed) for educational reasons mainly
and not only to be practically exploitable.

The operating frequency will be somewhere between 900 and 1300 MHz.
However, the test frequency that I used for my measurements was 1111
MHz.

So, I would be very happy if you could spend some time
to take a look to some of its characteristics:

The following URL shows the geometry of the antenna in the 3D space.
As you can see, it lies at the yoz plane.
As you cannot see, the input source is considered to be
at the starting point of the axes, O.
http://antennas.ee.duth.gr/ooo/dt/05...ometry/geo.jpg

The following URL contains a text file with the coordinates of
the antenna's nodes and also the orientation of the current
running through the segments of the anntenna.
Its the input file to the program that I used
to compute the various characteristics.
http://antennas.ee.duth.gr/ooo/dt/05...etry/input.txt

The following URL will clear out the situation a little bit.
http://antennas.ee.duth.gr/ooo/dt/05...0analysis2.gif
It shows the current distribution (which is assumed to be sinusoid)
at the various segments of the antenna, as it results
from the application of the standing wave theory.
The antenna is composed of 7 dipoles lambda/2.
The angle between the 2 dipoles at both of the tops
of the antenna is 60 degrees.

The following URL shows the radiation pattern in 3D space.
http://antennas.ee.duth.gr/ooo/dt/05...ichwire/da.jpg

The following URL shows the comparison of the radiation pattern
at the 3 main planes (xoy, yoz, zox) at cartesian and polar coordinate
systems
between the analytical and the computational method.

http://antennas.ee.duth.gr/ooo/dt/05...analytical.doc

During the analytical method the antenna considered to be
polygonical and thinwire. The current distribution assumed to be
sinusoidal.
During the computational method I used a program called Richwire and is
based
at the Methods of Moments.


Finally, the following URL shows a series of measurements of various
characteristics
as the antenna is being divided at an increasingly number of segments.

http://antennas.ee.duth.gr/ooo/dt/05/hli/14/totals.txt

The columns of the txt file from the left are representing:
1.Segments, 2.Frequency [MHz], 3.Rinput resistance [O], 4.Xinput
reactance [O],
5.|Z| input impedance's magnitude [O], 6.Input impedance's phase
[degrees],
7.SWR(Zo=50O), 8.SWR(Z0=75O), 9.SWR(Zo=300O), 10.D directivity,
11.D[dB], 12.D [dBd],
13.Front to back ratio (Ef/Eb)

As you may notice the value of input impedance is too high.
therefore, SWR is very increased.
I've added lambda/2 and lambda/4 transmission lines at the source
which were situated perpendicular to antennas plane (at xoy plane)
in order to alter the input impedance's value.
However, the results from both attempts were not satisfying.

I look forward to hear proposals and advices in order to decrease SWR.
Are there any standard transmission lines at the market with Zo
aproximatelly
to my input resistance so I can recalculate SWR with better results?

I ask apologize for any mistakes and for my poor english
as it is not my native language.

Thank you in advance

Dimitris I.

"Dimitris" wrote in
oups.com:

http://antennas.ee.duth.gr/ooo/dt/05...chwire11analyt
ical.doc

I did an analysis of my own (with very poor tools) that indicated that the
antenna is resonant at 93.1 percent of the design frequency with an
impedance of very close to 75 ohms resistive.


--
Dave Oldridge+
ICQ 1800667

On 12 Dec 2005 11:32:59 -0800, "Dimitris" wrote:

I look forward to hear proposals and advices in order to decrease SWR.
Are there any standard transmission lines at the market with Zo
aproximatelly
to my input resistance so I can recalculate SWR with better results?

I ask apologize for any mistakes and for my poor english
as it is not my native language.

Thank you in advance


Hi Dimitris,

Your English is very good. One question: What is it you want to
achieve that only this antenna can do?

73's
Richard Clark, KB7QHC

Richard Clark wrote:

On 12 Dec 2005 11:32:59 -0800, "Dimitris" wrote:

I look forward to hear proposals and advices in order to decrease SWR.
Are there any standard transmission lines at the market with Zo
aproximatelly
to my input resistance so I can recalculate SWR with better results?

I ask apologize for any mistakes and for my poor english
as it is not my native language.

Thank you in advance


Hi Dimitris,

Your English is very good. One question: What is it you want to
achieve that only this antenna can do?

73's
Richard Clark, KB7QHC




Sorry Dimitris but I have to agree with Richard Clark.

The frequency range from 900 to 1300 MHz is a common frequency for the older
mobile phone systems and the DECT cordless phones.

There are currently many available non-patented aerial designs available
when one needs an aerial for this frequency range.

You need to declare a number of other parameters except the fact that you
managed to create a novel design.

The question is - Why choose this aerial?

Antenna gain?
Directivity?
Sensitivity to ferronous materials in the close vicinity?
Production - is the aerial easy to reproduce?

As the aerial seems to be a balanced design, how sensitive will the to
production tolerances and inaccuracies?


Except for these basic questions - it's always nice to see new or different
aerial concepts popping up Dimitris - so keep buggering on!


Cheers


Dan Andersson / M0DFI

Ο/Η Richard Clark Î*γÏ�αψε:
On 12 Dec 2005 11:32:59 -0800, "Dimitris" wrote:

I look forward to hear proposals and advices in order to decrease SWR.
Are there any standard transmission lines at the market with Zo
aproximatelly
to my input resistance so I can recalculate SWR with better results?

I ask apologize for any mistakes and for my poor english
as it is not my native language.

Thank you in advance


Hi Dimitris,

Your English is very good. One question: What is it you want to
achieve that only this antenna can do?

73's
Richard Clark, KB7QHC

Mr Richard

Thank you for your time and for the copliment.

First of all, I don't have many expectations
from this antenna. Its geometry has been chosen
somehow randomly.

The profit that we wish to gain from all this
is simply to be delighted in the procedure
of designing, simulating, improving and making conclusions
about an antenna.
If the antenna seems to have interesting
characteristics which can bee useful at certain
applications, so much the better.

We are post-graduate electrical engineering students.
Unfortunatelly, where we come from, there is not too much
effort for research and for developing realistic and applicable
technology products inside our universities.
Therefore, we are just trying to do this
mainly for educational purposes.

I am looking forward for your proposals and advices.

Dimitris I.

Dear Dan

You are right at all your points.
I have answered to Mr Richard
and I don't want to repeat myself.

However, I can tell you that there wasn't
any preceded and detailed consideration
about certain constraints, requirements or parameters
for the present aerial in order to be used in specific applications.

The aerial was chosen somehow randomly,
just to "investigate" if this thing "plays" and
how it "plays".

However I have to confess -and actually
I am not too proud about this- that our
educational level and our minimal almost non existent
technical and practical experience
concerning telecommunication and wave propogation matters
cannot allow us to bother with such "complicated" issues.

However, we are wandering into this because:
1) we need to apply our theoritical framework and create
something which may not be very important or useful from
practical point of view but maybe will make us feel
somehow satisfied for that we created something real
2) we may like it

Finally,I suppose that it is uninteresting
for you to be concerned with this matter which hasn't
any practical application.
I will comprehend the reasons
if nobody deals with this post.

However, I will continue to give you
new results about this essay and set
new questions.

With regards

Dimitris I.

Mr Dave

Can you mention the process that you followed
(programs that you used, in what frequency, wire's radius,
value for the conductivity etc)
in order to make this analysis?

I am surpised that you've found this value
for the input impedance, which is so different
from the one I calculated.

Finally, can you explain what you mean by
finding 93.1% resonance of the antenna?

Dimitris I.

On 14 Dec 2005 05:45:57 -0800, "Dimitris" wrote:
First of all, I don't have many expectations
from this antenna. Its geometry has been chosen
somehow randomly.

Hi Dimitris,

So, what we would call an object lesson.

We are post-graduate electrical engineering students.
Unfortunatelly, where we come from, there is not too much
effort for research and for developing realistic and applicable
technology products inside our universities.
Therefore, we are just trying to do this
mainly for educational purposes.

This is also the purpose of this group.

I am looking forward for your proposals and advices.

Beginning with a complex shape may introduce too many variables. This
can make it difficult to judge what is important. However, if you
wish to explore along these lines, you should also include a reference
to compare to. Also, you should attempt to make variations to your
design and compare among them as well. Take care to make the
variations small and then progressively larger so changes do not occur
suddenly.

73's
Richard Clark, KB7QHC

"Dimitris" wrote in news:1134575594.448347.204420
@z14g2000cwz.googlegroups.com:

Mr Dave

Can you mention the process that you followed
(programs that you used, in what frequency, wire's radius,
value for the conductivity etc)
in order to make this analysis?

I am surpised that you've found this value
for the input impedance, which is so different
from the one I calculated.

Finally, can you explain what you mean by
finding 93.1% resonance of the antenna?

I modelled it in MMANA (I said poor tools, remember), using the standard
..8mm wires and free space (no ground).

Then I moved the frequency and recalculated the pattern and impedance
until it became resistive at the terminals. That happened at a frequency
93.1% of what the full quarter-wave frequency would have been. And at
that frequency, the impedance was a resistive 75 ohms. In other words,
it resonates lower than the design frequency (hence the lower
resistance).

I started with 900mhz and ended up with 837.9, if I remember. I didn't
save it.


--
Dave Oldridge+
ICQ 1800667