Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

half wave dipole antenna

Status
Not open for further replies.

amirsde

Newbie level 5
Joined
Jun 26, 2015
Messages
8
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
57
Hi
Why the current distribution of a half wave dipole antenna is sinusoid ?
I mean how the length of the antenna is related to the wave period ?
Is there a formula for get this result ?
 

redcrystalline

Advanced Member level 4
Joined
Nov 10, 2010
Messages
117
Helped
13
Reputation
26
Reaction score
13
Trophy points
1,298
Activity points
1,882
YES FOR sure thereis a relation between antenna length and current period(or correspond frequency).
each antenna works under certain frequency range(named bandwidth)
you could convert this frequency to wave length by landa=c0/f formula
then since antenna is half wave it means antenna length is landa/2
 

rizwan183

Member level 4
Joined
Feb 15, 2013
Messages
70
Helped
6
Reputation
12
Reaction score
6
Trophy points
1,288
Location
Pakistan
Activity points
1,817
Yeah. The length of each arm of a dipole is Lambda/4 at frequency obtain from formula f=c/lambda. So it is equal to the length of half sinosoid. if your decrease length more it shows a triangular current pattern at that frequency. It is simply because current is zero at open ends. decreasing size of dipole more result in lower gain and directivity at that particular frequency.
 

amirsde

Newbie level 5
Joined
Jun 26, 2015
Messages
8
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
57
Hi thanks for response
I know that every antenna works at certain frequency
But my question is that why the length of the antenna is related to the wave frequency
I mean is that any relation that gives us sinusoid distribution along half wave dipole ?
Or how can we get how is the current distribution ?
 

hamidrezakarami

Full Member level 3
Joined
Feb 26, 2007
Messages
181
Helped
45
Reputation
88
Reaction score
42
Trophy points
1,308
Activity points
2,158
to get current distribution along any antenna numerical method likes MoM, FEM, TLM, .. . can be useful.
I think the best efficient method is MoM for a linear dipole antenna. NEC is a non-commercial software based on MoM to do this.
 

catherine_smith

Junior Member level 1
Joined
Jul 11, 2014
Messages
17
Helped
11
Reputation
22
Reaction score
11
Trophy points
3
Activity points
128
Hi.. The answer can be stated from transmission line (tx) theory.

Two-wire tx line with source at one end and open at other, will have standing wave patterns of current and voltage which repeats lambda/2 apart..Current is zero at open end, max at lambda/4 from end, and zero again at lambda/2.. this repeats over line.. Now imagine the tx line itself is lambda/4 long.. Now flare the top conductor upwards and the bottom conductor downwards.. What you get is two lambda/4 segments with a source at centre, and hence a lambda/2 half-wave dipole.

It is obvious now the current is zero at top end, and goes to a maximum towards center when it reaches lambda/4.. similarly for the lower segment, current starts with zero at bottom end and goes to maximum at center when it reaches lambda/4..
Hence you get a half sinusoid.
 
  • Like
Reactions: amirsde and FvM

    FvM

    Points: 2
    Helpful Answer Positive Rating

    amirsde

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top