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how to increase the efficiency - RF Cafe Forums
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lee85
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Post subject: how to increase the efficiency
Posted: Tue Sep 02, 2008 11:02 pm
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Captain |
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Joined: Fri Dec 14, 2007
11:23 am Posts: 9 Location: malaysia
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i have design monopole antenna for 915mhz however
the efficiency only 38.7%. so many ways i have done
and change other design but i can't improve
the efficiency.
i have limitation size for
gnd plane and also size for monopole antenna
what should i do?please help me
regards,
lee85
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nubbage |
Post subject:
Posted: Wed Sep 03, 2008 9:30 am
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General |
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Joined: Fri Feb 17, 2006
12:07 pm Posts: 236 Location: London UK
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Hello lee How are you measuring the efficiency?
What are you using as a comparison reference
to define 100% efficiency? What gain, polarization
and bandwidth do you need?
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lee85 |
Post subject:
Posted: Wed Sep 03, 2008 11:06 pm
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Captain |
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Joined: Fri Dec 14, 2007
11:23 am Posts: 9 Location: malaysia
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1. i measure the efficiency using the chamber
2. what do u mean comparison reference to
define 100%
3. the gain 1dB it is linear
polarization and the bandwidth 25MHz
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nubbage |
Post subject:
Posted: Thu Sep 04, 2008 7:00 am
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General |
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Joined: Fri Feb 17, 2006
12:07 pm Posts: 236 Location: London UK
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Hi lee The 1dB gain, linear polar and the 25MHz
(about 2.5%) bandwidth are all achievable with a
variety of designs, such as normal mode helical
quarter wave etc. It was just you used the term
"efficiency" and find that 38% is unacceptable.
I wondered what your reference model is for 100%
so I can see what basis you are using for acceptable
performance. When you say you are using a chamber,
that does not describe the actual method. Are you
plotting the E and H plane far-field patterns and
integrating them in software as part of a suite,
like Scientific Atlanta or similar, then accepting
the given answer? Or are you comparing the radiated
power with the input power to the antenna and computing
the answer as a percentage? As a rule of thumb,
the ground-plane dimensions (critical for compact
antennas) should be about lambda/3 by lambda/3 at
least in order to achieve high efficiency. Anything
smaller will greatly reduce the efficiency.
Have you checked the reflection coefficient and/or
S parameters?
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Posted 11/12/2012
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