Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic 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.

Register Log in

Req: Antenna Gain measurement

Status
Not open for further replies.

Rayengine

Full Member level 5
Joined
May 18, 2001
Messages
287
Helped
3
Reputation
6
Reaction score
3
Trophy points
1,298
Location
Hong Kong
Activity points
1,737
antenna gain measurement

Hi All,

How can we measure the antenna gain in-house ? Assume we only have reference dipole, signal generator and spectrum available only measurement.

Rgs

Rayengine
 

flatulent

Advanced Member level 5
Joined
Jul 19, 2002
Messages
4,629
Helped
489
Reputation
980
Reaction score
150
Trophy points
1,343
Location
Middle Earth
Activity points
46,689
real problem

You have to avoid several problems. The first is reflections. One way is to use the tops of two adjacent buildings. Also use a gain antenna at the other end of the path from the antenna you are to measure. (This cuts out reflections). First you measure the signal strengh with a half wave dipole then with the antenna you want to know the gain of. Do a sanity check against theory. Even commercial firms have trouble measuring gain accurately.
 

klug

Advanced Member level 1
Joined
Jul 4, 2002
Messages
476
Helped
12
Reputation
24
Reaction score
7
Trophy points
1,298
Activity points
4,382
As Flatulent has said, you need to use good directional antenna in other end. Also you need enough distance between antennas - it will be good to have 15 or more wavelength between antennas. Another factor is a height over ground - better to rise antennas more than 3 wavelength over ground or roof - locate dipole and testing antenna at the same height anyway.
 

dowjones

Full Member level 2
Joined
Nov 21, 2001
Messages
122
Helped
7
Reputation
14
Reaction score
1
Trophy points
1,298
Activity points
1,352
purcell method

there is a also an antenna gain measurement method called Purcell method which is quite simple. Briefly it consist on measuring the antenna input match of the antenna when looking at a ground plane placed in front of it at several distances. From the set of points you can trace a line and some parameter of the line (the slope or the ordinate at the origin) is proportional to the gain. I dont remember exactly the method but i tried it once, and you can make a search on the IEEE or the electronics letters with "purcell" keyword. However, for low gain antennas such as your dipole the uncertainty may be large
 

FANT

Advanced Member level 1
Joined
Feb 27, 2002
Messages
415
Helped
52
Reputation
104
Reaction score
37
Trophy points
1,308
Location
Italy
Activity points
3,646
Antenna gain measurement

During a seminar on RF measurement, a relator told about a method involving three antennas; first you measure the signal coming from couple antennas A+B, then B+C and at the end A+C, with the corrections and what all the other people already said ( height of the antennas, distance between the antennas, ecc. )
Then you make three equations with three unknow data ( the gain of the three antennas, because you do not have any reference isothropic radiator ).
You solve the three equations and you will have the absolute gain of the three antennas.
P.S. I have never tested it because we have calibrated antennas and field, but anyway I think is worth the test.

Mandi
 

personal

Junior Member level 3
Joined
Nov 29, 2002
Messages
30
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
141
measure antenna

Make sure the polarisation is not in the direction of the ground....It may induce a lot of errors...
 

Rayengine

Full Member level 5
Joined
May 18, 2001
Messages
287
Helped
3
Reputation
6
Reaction score
3
Trophy points
1,298
Location
Hong Kong
Activity points
1,737
I search with Google and found that there is a article in ARRL web site with the title that exactly what I want? But it restrict to member only! Any have this article on hand?
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top