the sake of simplicity, the discussion will continue on the basis of one 

 signal to be analyzed and one analysis system. 



While the filter network, which is the wave analyzer, operates on 

 the modulated carrier-input signal, through the entire frequency range 

 generated by the oscillator, the passed components proceed to the analog 

 computer portion of the SEADAC for further treatment. In the analog 

 computer, one of the following operational modes may be programmed: 



1. Average linear amplitude. 



2. Mean square energy. 



3. Integral of energy. 



The average linear amplitude may be thought of as an estimate of the 

 Fourier coefficients in a Fourier series analysis, where the amplitude assigned 

 to a particular harmonic is the average amplitude of it and the neighboring 

 harmonics within the bandwidth of the filter. As the width of the filter 

 approaches zero, the Fourier representation of the seakeeping event is 

 approached. This type of computer calculation is not desired at this 

 time, and has consequently not been applied to any data. 



The "mean square energy" operation is equivalent to computing energy 

 spectral density. The amplitudes of the frequency components in the pass- 

 band are continuously squared and averaged. This mode of operation is 

 used most frequently. 



Since the total energy in the spectrum is a measure of the "peak- 

 to-peak" distribution of the record of the seakeeping event being 



11 



