Terrestrial Transmission of Digital Television Signals (DVB-T) - Digital Video and Audio Broadcasting Technology - page 364

c fu = 20 log(U peak /U RMS );
Power meters and spectrum analyzers are sometimes also calibrated to
the following definition:

c fp = 10 log(PEP)/P AVG ;

where PEP is the peak envelope power (U peak /√2) 2 / z o ;
and P AVG = U RMS 2 / z o ;

The two crest factor definitions thus differ by 3 dB:

c fu = c fp .+ 3 dB;

The crest factor of COFDM signals is calculated as follows:

The maximum peak voltage is obtained by adding together the peak
amplitudes of all single carriers:

peak = N • U peak0 ;

where U peak0 is the peak amplitude of a single COFDM carrier
and N is the number of COFDM carriers used.

The RMS value of a COFDM signal is calculated from the quadratic
mean as:

2

U = N ⋅ U ;

RMS RMS 0

where U RMS is the RMS voltage of a single COFDM carrier

2

U

peak 0

U = ;

RMS 0

2

The RMS value of the COFDM signal is then:

2

U

peak 0

U = N ⋅ ;

RMS

2