LewisCobb
Electrical
- Aug 23, 2003
- 5
Hi - I have a rather specific question that someone may be able to answer with regard to the averaging of emissions for an on-off keyed transmitter under FCC part 15.35
According to the FCC documents and all that I have found through reading through it - the averaging can be used to gain up to a 20dB (10x received uV/m field strength) advantage by calculation of the average emissions over the busiest 100mS window.
An example - if the transmitter is putting out 100,000 uV/m at three meters and the duty cycle can be shown to be 10% - the averaged emission is 10,000 uV/m and will pass the emissions level.
I believe that the above averaging also holds true for the harmonics and their regulation levels.
My Question - for those harmonics that fall within the restricted bands - can this averaging also be applied to them, keeping in mind that the average must be equal or below the smaller emissions limit?
At 433.92MHz, the third harmonic is in a restricted band and has to be under 500uV/m at three meters. Does this mean that for a 50% on-off modulated data stream, the peak emisison can be 1000uV/m or are we resticted to a 500uV/m peak regardless of the duty cycle ?
Thanks for any assistance people can provide or perhaps pointers to a test house I can pose this question to.
Lewis
cobb@baseng.com
According to the FCC documents and all that I have found through reading through it - the averaging can be used to gain up to a 20dB (10x received uV/m field strength) advantage by calculation of the average emissions over the busiest 100mS window.
An example - if the transmitter is putting out 100,000 uV/m at three meters and the duty cycle can be shown to be 10% - the averaged emission is 10,000 uV/m and will pass the emissions level.
I believe that the above averaging also holds true for the harmonics and their regulation levels.
My Question - for those harmonics that fall within the restricted bands - can this averaging also be applied to them, keeping in mind that the average must be equal or below the smaller emissions limit?
At 433.92MHz, the third harmonic is in a restricted band and has to be under 500uV/m at three meters. Does this mean that for a 50% on-off modulated data stream, the peak emisison can be 1000uV/m or are we resticted to a 500uV/m peak regardless of the duty cycle ?
Thanks for any assistance people can provide or perhaps pointers to a test house I can pose this question to.
Lewis
cobb@baseng.com