microwave antenna measurement

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scoppulal

Joined: 18 Apr 2004
Posts: 131
Helped: 1

16 May 2004 11:05 microwave antenna measurements

hi all,
could anybody help on this topic?

The point is that i can't buy a vector network analyzer or things like that.

Any advice or comment is appreciated.
regards

eirp

Joined: 11 Dec 2001
Posts: 639
Helped: 9
Location: Phase center

16 May 2004 11:13 aiming microwave antenna

scoppulal wrote:

hi all,
could anybody help on this topic?

The point is that i can't buy a vector network analyzer or things like that.

Any advice or comment is appreciated.
regards

Hi!

If you're interested in reflection coeficient -

You can perform scalar measurement e.g. with 3dB hybrid coupler and microwave detector.
This is very simple but needs to be very precisely build. There will be always systematic error.

Cheers

eirp

plasma

Joined: 20 Dec 2001
Posts: 577
Helped: 40

17 May 2004 0:05 microwave antenna measurement

Locate on your place factory that use network analyzer pay them
For using it after work hour. Or go to the nearest university probably they have it, and then try to get help there.

RGZ

chinaing

Joined: 05 Dec 2003
Posts: 35

17 May 2004 7:25 vswr antenna measurement power meter

if you haven't network analyzer, you could not measure any s signal~~~

starchern

Joined: 21 Feb 2004
Posts: 44
Helped: 2

18 May 2004 3:46 microwave antenna measurement pdf

antenna parameter (ex:gain,pattern) can measure without NA.

you can use SG(signal generator) and Spectrum or Power meter

radiation pattern measurement can obtain easily

but gain measurement must have a standard gain antenna

klug

Joined: 04 Jul 2002
Posts: 446
Helped: 5

18 May 2004 9:47 Re: microwave antenna measurement

Hmm, very interesting. I have the same problem to measure SWR on 2.4 GHz.

What is construction of this "network analyzer"?

I have 26MHz-1GHz measuring selective microvoltmeter (SMV8.5). I can receive 2.4 GHz by using 2.5 Ghz MMDS downconverter.

So, I need generator for 2.4 GHz. Is there any construction of noice generator for that band? Or simple near stable generator?

Also, is there info about good direct coupler for that frequency that I can make at home conditions?

goxy

Joined: 25 Jul 2002
Posts: 268
Helped: 1

18 May 2004 12:01 Re: microwave antenna measurement

@scoppulal What range do you need, I know simple NA construction for 100MHZ-1.3GHZ

@klug
For SG try with MAX2750, MAX2751, MAX2752 VCO's at 2.4GHz, price is low and they allow free samples.
For power detector use from Maxim(MAX4000, MAX4001, MAX4002) or from Analog. Also and diode detector can be used.

Coupler can be make in home conditions on FR4, simulation is very easy in Genesys or MWO(use linear, no need EM simulator).

scoppulal

Joined: 18 Apr 2004
Posts: 131
Helped: 1

18 May 2004 12:39 Re: microwave antenna measurement

the band of interest is the 2.4 GHz
for both satellite applications and wireless lan i'm putting up.

But also the band GOXY were talking about could be interesting
share knoledge with us plese.

Ciao

Google
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18 May 2004 12:39 Ads

sergio mariotti

Joined: 22 Dec 2003
Posts: 467
Helped: 42
Location: Italy

18 May 2004 21:51 microwave antenna measurement

Almost all parameters magnitude may be measured without VNA.
I agree with most of preceeding ideas about SA. A power meter should be used with attention, the risk is to receive unwanted strong signal (TV, Phones etc.)

I remember, i've read an article about the measuremet of phase centrer without VNA. If you are interested i'll look for.

a SA (not necessarely sintetized) and a generator and are enough to measure |co-pattern|, |cross-pattern|. The same generator and SA, with a good directional coupler, may measure the reflection coefficient also.

An accurate gain measurement is peraphs the most hard measurement to do, also with a VNA. Most of the expensive standard antennas, don't take in account for the ohmic (dissipative) loss.
enjoy

goxy

Joined: 25 Jul 2002
Posts: 268
Helped: 1

18 May 2004 22:12 Re: microwave antenna measurement

Look at:

http://www.circuitcellar.com/psoc2002/winners/3.htm
http://www.circuitcellar.com/psoc2002/winners/3.pdf
http://www.circuitcellar.com/psoc2002/winners/3.zip

Prescaler need to be replaced with some better, for example with Fujitsu MB506.

For 2.4GHz I'm explain in the above post. I'm forgot, and device like 2.4GHz 802.11b/g card can be signal generator. Detector diode can not detect real power because modulated signal. This detect value need to be converted in depentency of modulation, in Matlab or any system simulator this can be solver like Genesys, ADS,MWO.....

For satelite applications again you need signal generator, VCO's are expencive so remove DRO(dilectric resonator oscillator) from down converter and use them, diode detector for signal detector and 3dBcoupler(on some better material Rogers, Gil...).

divan

Joined: 01 Mar 2002
Posts: 91
Helped: 2

19 May 2004 3:58 Re: microwave antenna measurement

@klug
For SG try with MAX2750, MAX2751, MAX2752 VCO's
For power detector use from Maxim
Coupler can be make in home conditions on FR4, simulation is very easy in Genesys or MWO(use linear, no need EM simulator).
[/quote]

For Antenna gain meashurement the power of Maxim's VCO is not enough , you have to use additional PA and gain power to about +20/26dBm output.
And - very important - need to use On/Off keying of TX , the aim of this - you can avoid DC current offset at receiver side amplifier and reduce the errors. this possible to provide by PA's power supply switching , 1-10 kHz for example.

For VSWR measurement you can use a 50 ohm microstrip line at FR4, about half of wave, inserted btw antenna and TX closely to antenna and measure standing wave coefficient by the simpliest detector with small loop style probe , when move this one along the microstrip line . I think for your's homebrew antenna this will be the fastest way.
And don't forget about fadding and multipass propagation when make antenna gain measurement , shure you have no anechoic chamber .

try !

yakult

Joined: 28 Apr 2004
Posts: 7

19 May 2004 6:28 Re: microwave antenna measurement

You should connect the antenna with Network analyzer. The antenna should put inside a chamber to prevent measurement error from reflection.

It is suggested that you connect the antenna with the device (e.g. a mobile phone) in order to get a more accurate results

Yakult

goxy

Joined: 25 Jul 2002
Posts: 268
Helped: 1

19 May 2004 9:05 Re: microwave antenna measurement

AND/OR LNA have to be used Smile

On 8m distance between Rx and TX antenna, 3dB cables loss and 10dB antennas gain expected power is -47dBm.

I'm desing coupler with two line probes, if anybody need I can post here.

divan, can you explain On/Off keying of TX technique or post some papers.

BTW. I think better is to use bias PA switching then power supply.

richard_pan

Joined: 07 Oct 2004
Posts: 16

17 Jan 2005 5:16 Re: microwave antenna measurement

who can give me some material about antenna measurement with VNA,I really want such things,thanks

sergio mariotti

Joined: 22 Dec 2003
Posts: 467
Helped: 42
Location: Italy

17 Jan 2005 23:09 Re: microwave antenna measurement

richard_pan wrote:

who can give me some material about antenna measurement with VNA,I really want such things,thanks

Rohde&Shcwarz and Agilent produce Vector instrumentations tailored to measure antennas.
In most cases, vector measurement call for near field measurement and for a post processing to transforme data into far field pattern.
Look for that instruments and you'll find lots of Application Notes.

Vector measurement open the possibility to do exoctic measurement like holographic analysis of the antenna's mirrors

iamchrisk

Joined: 20 Dec 2004
Posts: 7

18 Jan 2005 16:02 microwave antenna measurement

radiation pattern can be measured by using signal generator and spectrum.
but if you would like to measure the gain then NA would be the fastest and easiest method to go.