INTERMITTENT BEHAVIOR IN OSCILLATORS 9 



Filter 



The filter of Fig. 8 consists of only a single tuned circuit. Its transmission 

 is readily represented in terms of the circuit Q by the familiar universal 

 resonance curve. The transmission of a modulated wa\'e through such a 

 passive network is conveniently determined by separating the wave into 

 its carrier and two sidebands. The carrier will be the frequency F corre- 

 sponding to zero phase shift which, in this case, is also the frequency of 

 maximum transmission. The sidebands will be shifted in phase by equal 



1.0 IQ. 



F 



2.0 



1.0 f Q 



2.0 



Fig. 9 — Envelope transmission of a modulated wave through a single tuned circuit of 



selectivity Q. 



Fig. 10 — Data of Fig. 9 plotted in polar form. 



and opposite amounts and attenuated according to the frequency / by which 

 they differ from the carrier. This behavior is interpreted in Fig. 9 as trans- 

 mission and phase shift of the envelope. It is seen that the transmission 

 approaches zero and the phase shift approaches 90° as the modulation 

 frequency is indefinitely increased. The same data is presented in polar 

 form in Fig. 10. Specifically Fig. 10 shows the vector ratio of the modula- 

 tion factor m of the output wave to that of the input wave for all frequencies. 

 In Fig. 9 the magnitude and phase angle of the ratio are shown separately. 



Limiter 



The limiting action of the tube and diode combination is determined by 

 direct circuit analysis. For very low modulating frequencies the condenser 



