Thread: Multi-Carrier measurement PXA signal anlyzer


Permlink Replies: 2 - Pages: 1 - Last Post: Apr 29, 2012 1:33 PM Last Post By: Leyo
Leyo

Posts: 63
Registered: 04/17/07
Multi-Carrier measurement PXA signal anlyzer
Posted: Apr 27, 2012 11:38 AM
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Hello,

I am trying to measure the ACP of a multi-carrier basestation transmitter using PXA signal anlyzer.
The carriers are spaced @ 1MHz and there are 6 carriers with GMSk modulation. Power of each carrier is 36.4 dBm.
In the ACP setup for carrier configurations, there is a a button called "Measurement Noise BW". What is the siginificance of this BW. Is this the BW in which the acrrier power is measured?. My carriers BW is 200 KHz(GMSK) . But seeting the measurement noise BW to 200 KHz, the measured power of each carriers is around 1.5 dB less than the expected 36.4 dBm. To get carrier power of 36.4 dBm, the measurement BW should be around 1MHz?
Also is this tied to the measurment method of "Integ BW" and "RRC weighted". Please explain the difference between these methods.

Thanks
Leyo
tabbott


Posts: 1,483
Registered: 07/24/09
Re: Multi-Carrier measurement PXA signal anlyzer
Posted: Apr 27, 2012 5:14 PM   in response to: Leyo in response to: Leyo
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Hi Leyo -

See coments in bold -

I am trying to measure the ACP of a multi-carrier basestation transmitter using PXA signal anlyzer.
The carriers are spaced @ 1MHz and there are 6 carriers with GMSk modulation. Power of each carrier is 36.4 dBm. I hope you have ample external attenuation applied since the safe input level to the PXA is +30 dBm, and you are inserting +36 dBm!!
In the ACP setup for carrier configurations, there is a a button called "Measurement Noise BW". What is the siginificance of this BW. Is this the BW in which the acrrier power is measured?.
After you press: Configure Carriers button, press the green Help key, then press Measurement Noise Bandwidth key. You will now see the description of the key. Indeed this is the BW which the carrier power is measured.
My carriers BW is 200 KHz(GMSK) . But seeting the measurement noise BW to 200 KHz, the measured power of each carriers is around 1.5 dB less than the expected 36.4 dBm. To get carrier power of 36.4 dBm, the measurement BW should be around 1MHz? Yes, the 36.4 dBm carrier power is the total carrier power of all 6 carriers. Each individual carrier power is less, and the 6 carriers “add” to provide the expected 36.4 dBm total carrier power.

Also is this tied to the measurment method of "Integ BW" and "RRC weighted". Please explain the difference between these methods.
The Help feature used above does not answer this question. While on the subject of where to find more information, please see the PXA User’s and Programmers Reference at:
http://cp.literature.agilent.com/litweb/pdf/N9060-90027.pdf

See: http://en.wikipedia.org/wiki/Root-raised-cosine_filter

Regards -
Leyo

Posts: 63
Registered: 04/17/07
Re: Multi-Carrier measurement PXA signal anlyzer
Posted: Apr 29, 2012 1:33 PM   in response to: tabbott in response to: tabbott
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Hello,

Thank for the response.
Yes, I have 40 dB of attenuation in-front of PXA. So PXA signal level is taken care of.
The 36.4 dBm is the power of each carrier. I am expecting total power of 36.4 dBm+10*log(10). Each individual carrier power is 1.5 dB less than expected when the measurement noise BW is 200 KHz.
If the measurement noise BW is same as integration BW, why it is not named as integration BW. For the case of offset measurements, it is named as integration BW.
For carrier power measurement, is there any ratio we have to maintain between integration BW and RBW?.
Thanks,
Leyo

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