hi fi stereo multiplexer for fm

Posted on Feb 6, 2014

A Left and Right source of audio are first pre-emphasized (HPF) and then fed to adder circuits. The output of one adder is the sum of the two signals, or the L + R signal (the monaural signal), and the output of the other adder is the difference of the two signals, or L R. The L R signal is applied to a balanced modulator along with a 38-k

hi fi stereo multiplexer for fm
Click here to download the full size of the above Circuit.

Hz signal. The output of the balanced modulator is a DSBSC AM signal centered at 38 kHz. A portion of the 38-kHz signal is divided in frequency to become 19 kHz, and all three signals are applied to a summary/adder circuit at the output of the generator. The L + R signal, which contains baseband frequencies from near 0 Hz to 15 kHz, occupies that portion of the frequency spectrum. The 19-kHz tone is pilot sub-carrier signal, which will be used at the receiver to aid in the demodulation of the received signal. The L R signal, which has been DSBSC amplitude modulated by a 38-kHz tone, occupies the frequency range from 23 to 53 kHz. In FM, the noise increases with modulation frequency. To compensate for this effect, FM communication systems have incorporated a noise-combating system of pre-emphasis and de-emphasis. Pre-emphasis provides increased amplitude to the higher modulating frequencies prior to modulation under a well-defined pre-emphasis (high-pass filter) curve. This added amplitude will serve to make the higher frequencies more immune to noise by increasing their index of modulation. De-emphasis is just the opposite operation (using a low-pass filter) and it is done at the receiver. The NJM2035 is an integrated circuit used to generate a stereo composite signal and obtain switching out and 19Khz pilot signal due two input audio signal and 38Khz X-tal and few external CR. This stereo encoder is the perfect solution...

Leave Comment

characters left:

Related Circuits

  • New Circuits



    Popular Circuits

    30 LED audio frequency analyzer
    Telephone blinker
    Voltage Doublers
    Temperature To Pulse Width Converter Circuit Using LM3524
    AF counter circuits
    decoder circuit
    wein bridge oscillator using jfet
    Distance measurement system using PING Ultrasonic Range Finder
    Ultrasonic sensors apply to parking sensor system
    Tuned radio frequency receiver
    Lantern making use of a relay control circuit