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PaulHolland
Joined: 15 Jan 2003
Posts: 636
Helped: 59
Location: Holland
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 06 Nov 2009 21:00 Who can design an small antenna for 170 MHz ?. |
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| Hi Who can design an antenna that works from ideally from 160 MHz upto 900 Mhz and even 2.4 GHz. It could also be two designs. One from 160 Mhz upto 175 Mhz and the other from 850 - 2500 MHz !. Design must be simulated and proven to work. Payment possible !
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06 Nov 2009 21:00 Ads |
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FvM
Joined: 22 Jan 2008
Posts: 5161
Helped: 767
Location: Bochum, Germany
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06 Nov 2009 22:26 Who can design an small antenna for 170 MHz ?. |
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| What's small for you? A logper would be the classical solution at least for the upper range.
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biff44
Joined: 24 Dec 2004
Posts: 1835
Helped: 244
Location: New England, USA
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06 Nov 2009 22:37 Re: Who can design an small antenna for 170 MHz ?. |
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This guy is very good with electrically small antennas
http://www.ieee.org/web/education/Expert_Now_IEEE/Catalog/antennas.html
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PaulHolland
Joined: 15 Jan 2003
Posts: 636
Helped: 59
Location: Holland
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06 Nov 2009 23:00 Re: Who can design an small antenna for 170 MHz ?. |
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| 8 Inch long and 3 inch wide PCB maximum 1 inch high.
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E Kafeman
Joined: 04 Jan 2007
Posts: 9
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09 Nov 2009 3:05 Re: Who can design an small antenna for 170 MHz ?. |
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A general rule for small antenna volumes (less then a wave length):
Effectiveness×Bandwidth=Size
Any small good conducting structure act as antenna for any frequency.
By requiring a very wide bandwidth and limited antenna volume, must you let it cost effectiveness. If you is prepared to this, is it no problem.
A antenna designer can then adjust the structure for a specific polarization, radiation direction and radiation impedance for best possible fit to actual RX/TX requirement.
But he can not improve the rule above!
With given space is it not possible to design a wide band antenna (>50% of center freq) which is not directional and covering frequencies below ~1.5 GHz.
Mainly due to the low height above ground (1 inch) but also the width limits a dipole or monopole function.
Of course can a antenna be designed small and still be resonate for a specific frequency but the rule remains.
Inside modern multi band cellular phones are small antennas that is covering 800-1000 and 1700-2100 MHz within a single PIFA antenna structure.
From antenna view is this very wide but it is at cost of antenna effectiveness.
It is common that 50% of the TX power is converted to heat, or even more in real small cell phones as the phone ground plane is a part of the antenna in this antenna type.
Even if you limit the required bandwidth to 10 MHz at 160 MHz is it not easy to make an omnidirectional antenna with good performance within given space.
Hand held units operating at 160 MHz do usually have a narrow band antenna, stubby or (ferrite)loop with moderate performance or a retractable antenna with somewhat better function. A relative good antenna for this use is a resonant ¼
wave monopole which at 160 MHz is 18 inch long. This antenna is both effective and have a wide bandwidth (~20 MHz) if the ground plane is of similar size.
It is possible to make it shorter by different kinds of loading of the antenna circuit, but any kind of loading do cost either bandwidth or radiation effectiveness.
With less good performance required, say -10 dBi in average radiation pattern, can short monopoles or loop antennas at 160 MHz with one inch of height be designed similar to the active FM antennas that can be seen on the roof of some cars (shark fins).
Better performance can be achieved by concentrating radiation pattern in a narrow direction or reduce required bandwidth.
With above in mind, I can easily design the antenna you want, as long as you not have specified antenna performance requirements of any kind.
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