anyone have some idea for steering radiation pattern?

[105s]

how to steel the radiation pattern of HF antenna? as you know,HF antenna 's dimensions is ver large,so i don't wish i could steel the antenna mechanical.can you tell me some advice ?

 

[sergio mariotti]

Do you want reduce the pattern for communication or for "finding"?
For findind, you may couple 2 or more antennas (of couse diminsions rises). The resulting pattern is composed by more, smaller, Greating lobes (also called "interference" - from Physical Optic-) the dimension of the new lobes decrease as you rise the distance form each antenna.
In spite of the increasing of the overall dimension, the weight and cost rise less than a bigger antenna.

 

[105s]

I want to find a way to steel the pattern of a HF antenna.and its frequency is 4~25M.at the present time,the pattern in horizontal plane is omnidirectional. and now i wish to destory the omnidirectional pattern and get a beamform with a specify bandwidth.can you help me?

 

[sergio mariotti]

The only effective way i know is the use at least 2 directive antennas and then put the signal into a variable-phase combiner.

To reduce the dimension and weight of the antenna you may take in account the use of small spiral antenna. But this kind of radiator, born for military use, give a Gain very low (often efficency is 0.1 or less).

 

[105s]

the key is to how to find a algorithm to control the phase,is it right?in order to do it,do i need use dsp?

 

[Poezie]

What you need is a source with a power splitter to seperate a reference signal in to 2 different channels. On both channels you need a integrated addapteble delay lines (or systems), which introduce a phase-shift between the two signals b appling a delay in time. The two signals will be emitted by a two antenna's.
The resulting wavefront has a propagation direction which is depending on the delay you setted.

The algoritme is not so difficult, When you try to draw the 2 signals with a phase-shift and you'll see in which direction the wavefront will propagate.

The steering of the delay lines can be done manual or with a dsp or other system (depending on how much money you want to spend )

Hopefully this will help you a little bit

 

[105s]

Thanks! I still have three question:
1.the antenna type:which type can be adopt? I don't need omnidirection antenna.
2.how to design the the delay lines? where can i find some paper about it?
3.the two different channels must connect two radiation or two arm of the antenna?it is right?