# UWB PA Transmitted Power and Spectrum Mask? - RF Cafe Forums

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Guest
Post subject: UWB PA transmitted power and spectrum mask? Posted: Wed Nov 30, 2005 9:30 pm
Dear all,

I have seen some specificaiton stated that the spectrum mask of the UWB is -41.3dBm/MHz. For the average Tx power is -10.3dBm. I want to ask how is the -10.3dBm get? I am so trouble about these two values. Is it means that the transmitted output power from PA must need to reach to -10.3dBm?

thanks

wccheng

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Guest
Post subject: UWB powerPosted: Thu Dec 01, 2005 12:34 pm
In the US, these are legal maximum limits - not required powers!

The spectral mask is there merely to assure that the power is spread over the assigned bandwidth equally, which will reduce interference with existing (licensed!) services. Please notice the very low power: -10.3 dBm is 93.3 microwatts. This level of power can often be generated directly, without the need for an amplifier.

Good Luck!

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rficdude
Post subject: Posted: Wed Jan 04, 2006 11:35 pm

Lieutenant

Joined: Sat Dec 31, 2005 9:19 am
Posts: 4
With a spectral density limit of -41.3 dBm/MHz the TX power of -10.3 dBm is a 30 dB difference. This means the TX bandwidth is three orders of magnitude larger than the 1MHz spectral density, so the -10.3 dBm TX power is for a 1GHz bandwidth (-10.3 dBm/GHz).

For UWB the maximum bandwidth is 7GHz for the 3-10 GHz band so the maximum TX power allowed should be about -2.8 dBm.

_________________
RFICDUDE

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jaslovkel
Post subject: Posted: Tue Jun 26, 2007 1:40 pm

Captain

Joined: Tue Jun 26, 2007 10:27 am
Posts: 11
Location: Dallas, TX
For IEEE 802.15.3a the specification states that the maximum transmit power for a UWB signal is -41.3 dBm/MHz. Each UWB band is 528 MHz as stated in the MB-OFDM proposal (which has seemed to take over compared to the DS-CDMA proposal). There are 14 band groups allocated in the UWB proposal located from 3.1 to 10.6 GHz, but right now most companies and researchers are only concerned with what is called "Mode I" of UWB which focuses on the 3 band groups located between 3.1 and 4.7 GHz. Therefore, we calculate the maximum average transmit power for a Mode I UWB device as follows:

-41.3 + 10*log10(3*528)= -9.3 dBm

Then, we operate at 1 dB backoff to make sure we stay below the FCC regulation and we end up with a maximum transmit power of -10.3 dBm.

If we talk about average transmit power for all 14 bands with a 1 dB power backoff we will obtain:

-41.3 + 10*log10(14*528) - 1 = -3.6 dBm

Posted  11/12/2012

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