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.

Antennas suitable for radiation pattern measurements

Status
Not open for further replies.

VR4V6E39

Newbie level 6
Joined
Aug 3, 2009
Messages
11
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
UK
Activity points
1,358
conducting antenna pattern

Hi, I was wondering if someone could tell me whether a biconical antenna as a transmitter would be suitable for conducting antenna pattern measurements? My confusion comes from the fact that for such antennas (and for frequencies less than 1GHz) the physical size would be rather large, and hence the far-field criteria would not be met if it was conducted in a chamber of 5m maximum length?
 

vfone

Advanced Member level 5
Joined
Oct 10, 2001
Messages
5,392
Helped
1,560
Reputation
3,123
Reaction score
1,170
Trophy points
1,393
Activity points
34,178
Actually standard biconical antennas used for EMI measurements works in frequency range: 30MHz-1GHz

**broken link removed**
 

VR4V6E39

Newbie level 6
Joined
Aug 3, 2009
Messages
11
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
UK
Activity points
1,358
So does that mean they are not suitable for conducting antenna pattern measurments?

Whats the minimum sufficent gain required for the transmit antenna?
 

Kohi_boy

Full Member level 4
Joined
Apr 20, 2008
Messages
206
Helped
39
Reputation
78
Reaction score
23
Trophy points
1,298
Activity points
2,093
I would recommend to have a narrow beamwidth so as not to illuminate the surrounding.
 

biff44

Advanced Member level 5
Joined
Dec 24, 2004
Messages
4,955
Helped
1,369
Reputation
2,734
Reaction score
1,045
Trophy points
1,393
Location
New England, USA
Activity points
37,223
If you are making pattern measurements in the great outdoors, it is not so critical. If you are making pattern measurements in a chamber or room, then you do not want reflections off the walls confusing your gain vs azimuth readings, so you want a small, higher gain antenna, with very low back/side lobes.
 

VR4V6E39

Newbie level 6
Joined
Aug 3, 2009
Messages
11
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
UK
Activity points
1,358
Measurements will be conducted in a chamber and therefore yess I will need very narrow beam antennas I agree, but with low frequencies (<GHz) high gain antennas are not acheivable and what I wanted to know is what sort of gain or beamwidth should I be looking for?
 

biff44

Advanced Member level 5
Joined
Dec 24, 2004
Messages
4,955
Helped
1,369
Reputation
2,734
Reaction score
1,045
Trophy points
1,393
Location
New England, USA
Activity points
37,223
**broken link removed**

For RF part 15 tests I have observed at certified test houses, they use antennas that look like these:
**broken link removed**

The will do one set of readings, and then rotate the antenna 90 degrees to get the other polarization. They will often have these mounted on a motor driven mast that allows them to raise and lower the antenna with respect to the floor height.

Added after 2 hours 13 minutes:

Of course, there is such a thing as near field and far field. Since many antennas at RF frequencies are physically large, you have to have a chamber that is big enough to be outside of the near field if you want an accurate gain measurement!
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top