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View all threadsUSRP transmission power
Hello List,
I have two USRP1 having D.B. WBX. I am transmitting through one USRP and receiving at another USRP.
I want to know what was the transmission power i.e. transmitted power of the USRP while transmission.
How can I calculate the transmission power?
Another question i have, can i change the transmission power for every transmission purpose?
Any help or suggestion is appreciated.
Thank you, Best Regards.
Alok Ranjan
Hi Alok,
How can I calculate the transmission power?
the power you transmit of course depends primarily on the signal you
transmit, on the TX gain you set, on your individual antenna, on the
frequency you're on, and to a certain degree on individual component
tolerances on the transmitting WBX. The only way of /knowing/ your power
is measuring in exactly the set up you have.
However, the USRPs/daughterboards are quite linear over quite a large
range, so if you take a signal, measure the power, and then use the same
signal but multiplied with 0.5, you'll get one fourth of the energy --
thus, you can generally assume signal energy to be proportional to the
square of your digital samples' magnitude.
Another question i have, can i change the transmission power for
every transmission purpose?
Of course. Just change the signal you're transmitting, or change the TX
gain, or do both.
Best regards,
Marcus
Hello Marcus,
Thank you for your prompt reply on the mentioned question. Since, I am new to the USRP community so I need some more expert suggestion from your end. I am just using the benchmark python script i.e. benchmark_tx.py and benchmark_rx.py for sending and receiving. Please Find below my complete set up,
Say, benchmark_tx.py -f 500e6 -M 0.5 --tx -gain=30 --tx-amplitude=0.8 -m qam
using the same for benchmark_rx.py also.
Would you please comment that how can i get the transmission power at the above mentioned setup.
However, i am able to get the avg received power per sample at receiver. say for eg. 8.8836e-06.
SO can I simply square the avg received power to get the transmitted power at that particular frequency and gain??
Thank you , Best Regards
Alok
Date: Thu, 30 Apr 2015 11:53:45 +0200
To: usrp-users@lists.ettus.com
Subject: Re: [USRP-users] USRP transmission power
From: usrp-users@lists.ettus.com
Hi Alok,
How can I calculate the transmission power?
the power you transmit of course depends primarily on the signal you
transmit, on the TX gain you set, on your individual antenna, on the
frequency you're on, and to a certain degree on individual component
tolerances on the transmitting WBX. The only way of knowing
your power is measuring in exactly the set up you have.
However, the USRPs/daughterboards are quite linear over quite a
large range, so if you take a signal, measure the power, and then
use the same signal but multiplied with 0.5, you'll get one fourth
of the energy -- thus, you can generally assume signal energy to be
proportional to the square of your digital samples' magnitude.
Another question i have, can i change the
transmission power for every transmission purpose?
Of course. Just change the signal you're transmitting, or change the
TX gain, or do both.
Best regards,
Marcus
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
Hello Alok,
Would you please comment that how can i get the transmission power at
the above mentioned setup.
use a calibrated measurement device -- as I explained, there's nothing
else you can do.
However, i am able to get the avg received power per sample at
receiver. say for eg. 8.8836e-06.
No! What you get are digital samples, which are, proportional to the
voltage that the ADC saw. That voltage in turn might be proportional, in
the best case (which you're free to assume in most of the operating
range of the USRP), to the voltage seen at the antenna port, but that's
just a "proportional to" relationship, and by no means the power itself.
SO can I simply square the avg received power
you're mixing things up. You receive samples having a magnitude that is
proportional to voltages at the ADC. If you square that magnitude, you
get something that is proportional to the square of these voltages, and
hence proportional to the power of the signal.
to get the transmitted power at that particular frequency and gain??
No. You need to use a measurement device that is calibrated to calibrate
your system.
Best regards,
Marcus
On 04/30/2015 12:25 PM, alok ranjan via USRP-users wrote:
Hello Marcus,
Thank you for your prompt reply on the mentioned question. Since, I
am new to the USRP community so I need some more expert suggestion
from your end. I am just using the benchmark python script i.e.
benchmark_tx.py and benchmark_rx.py for sending and receiving. Please
Find below my complete set up,
Say, benchmark_tx.py -f 500e6 -M 0.5 --tx -gain=30 --tx-amplitude=0.8
-m qam
using the same for benchmark_rx.py also.
Would you please comment that how can i get the transmission power at
the above mentioned setup.
However, i am able to get the avg received power per sample at
receiver. say for eg. 8.8836e-06.
SO can I simply square the avg received power to get the transmitted
power at that particular frequency and gain??
Thank you , Best Regards
Alok
Date: Thu, 30 Apr 2015 11:53:45 +0200
To: usrp-users@lists.ettus.com
Subject: Re: [USRP-users] USRP transmission power
From: usrp-users@lists.ettus.com
Hi Alok,
How can I calculate the transmission power?
the power you transmit of course depends primarily on the signal you
transmit, on the TX gain you set, on your individual antenna, on the
frequency you're on, and to a certain degree on individual component
tolerances on the transmitting WBX. The only way of /knowing/ your
power is measuring in exactly the set up you have.
However, the USRPs/daughterboards are quite linear over quite a large
range, so if you take a signal, measure the power, and then use the
same signal but multiplied with 0.5, you'll get one fourth of the
energy -- thus, you can generally assume signal energy to be
proportional to the square of your digital samples' magnitude.
Another question i have, can i change the transmission power for
every transmission purpose?
Of course. Just change the signal you're transmitting, or change the
TX gain, or do both.
Best regards,
Marcus
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Hello Marcus,
Thank you so much for your detailed explanation.
I could understand what you have suggested on the mentioned issues.
However, just share with you few formulas of relationship between the gain and transmission power and the energy and power.
Have a look and do comments...
- gain(db)=10log(Power received/transmit power) in db.
we have the gain setting at what transmitter was sending and calculated the received power per samples from complex data captured. Can we extract transmit power using the above formula??
- Energy=power*time
considering time as 1/Fc where Fc is the transmitted frequency and for energy as we have amplitude settings at transmitter the energy i am considering is area under the curve.
for eg. if tx amplitude is 0.5 then the equation is 0.5= power*1/500e6 . Since the SI unit of power is in watt so have to convert amplitude(db) into linear value for accurate readings.
Would you please comment that which formula would be quite useful .
Thank you for all your pain.
Best Regards,
Alok Ranjan
Date: Thu, 30 Apr 2015 14:40:27 +0200
To: usrp-users@lists.ettus.com
Subject: Re: [USRP-users] USRP transmission power
From: usrp-users@lists.ettus.com
Hello Alok,
Would you please comment that how can i get
the transmission power at the above mentioned setup.
use a calibrated measurement device -- as I explained, there's
nothing else you can do.
However, i am able to get the avg received
power per sample at receiver. say for eg. 8.8836e-06.
No! What you get are digital samples, which are, proportional to
the voltage that the ADC saw. That voltage in turn might be
proportional, in the best case (which you're free to assume in most
of the operating range of the USRP), to the voltage seen at the
antenna port, but that's just a "proportional to" relationship, and
by no means the power itself.
SO can I simply square the avg received
power
you're mixing things up. You receive samples having a magnitude that
is proportional to voltages at the ADC. If you square that
magnitude, you get something that is proportional to the square of
these voltages, and hence proportional to the power of the signal.
to get the transmitted power at that
particular frequency and gain??
No. You need to use a measurement device that is calibrated to
calibrate your system.
Best regards,
Marcus
On 04/30/2015 12:25 PM, alok ranjan via
USRP-users wrote:
Hello Marcus,
Thank you for your prompt reply on the mentioned question.
Since, I am new to the USRP community so I need some more expert
suggestion from your end. I am just using the benchmark python
script i.e. benchmark_tx.py and benchmark_rx.py for sending and
receiving. Please Find below my complete set up,
Say, benchmark_tx.py -f 500e6 -M 0.5 --tx -gain=30
--tx-amplitude=0.8 -m qam
using the same for benchmark_rx.py also.
Would you please comment that how can i get the transmission
power at the above mentioned setup.
However, i am able to get the avg received power per sample at
receiver. say for eg. 8.8836e-06.
SO can I simply square the avg received power to get the
transmitted power at that particular frequency and gain??
Thank you , Best Regards
Alok
Date: Thu, 30 Apr 2015 11:53:45 +0200
To: usrp-users@lists.ettus.com
Subject: Re: [USRP-users] USRP transmission power
From: usrp-users@lists.ettus.com
Hi Alok,
How can I calculate the transmission power?
the power you transmit of course depends primarily on the
signal you transmit, on the TX gain you set, on your
individual antenna, on the frequency you're on, and to a
certain degree on individual component tolerances on the
transmitting WBX. The only way of knowing your power
is measuring in exactly the set up you have.
However, the USRPs/daughterboards are quite linear over quite
a large range, so if you take a signal, measure the power, and
then use the same signal but multiplied with 0.5, you'll get
one fourth of the energy -- thus, you can generally assume
signal energy to be proportional to the square of your digital
samples' magnitude.
Another question i have, can i change the
transmission power for every transmission purpose?
Of course. Just change the signal you're transmitting, or
change the TX gain, or do both.
Best regards,
Marcus
_______________________________________________
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
_______________________________________________
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com