5 7
CHAPTER V III CONCLUSION
la th is thesis^the c irc u its are studied fo r sh iftin g the frequency between the input signals and output signals of an audio system, th is frequency sh iftin g method has been suggested by H.R.
Schroeder th at i t can improve the s ta b ility of the system . The input signals sin 271f t pass a 90 degrees phase s h ift network, the output w ill be cos 2ïïft. Because in our application the input signals are in the band of audio frequency, so the phase s h ift network
must be a band pass constant 90 degrees phase sh ift network. This mean th at the phase difference must be indepedent of input signal frequencies, then a phase angle which varies as the logarithm of the frequency is required. When two such network are in p a ra lle l th e ir phase difference w ill be independent ef frequency . The - quadrature signal generator w ill generate sh iftin g frequency signals sin 2 ะf'ûft, cos 2 77ûft. The signals are m ultiplied by signal m u ltip lier and added by sunming signal c irc u it to form ( sin2/7ft . cos277tft ♦ cos277ft . sin2^Aft ) . The A f frequency sh iftin g is achieved.
A fter te s tin g the c ir c u it , i t can be concluded th a t th e frequency are sh ifte d q u ite a ccu rately and the s ta b ility of the audio system is improved.
