FM demodulation

Faruk Kural

Other Parts Discussed in Thread: CD74HCT4046A

Hi everyone,

I need a PLL with VCO (e.g. CD74HCT4046A) or quadrature demodulator chip to demodulate FM signal. However, if the deviation of the input FM signal is less than a predefined frequency threshold (say; <10 kHz) or has an exact value (say; =60 kHz), i need NO demodulated output for both cases. Is it possible for potential chips to do so?

Thanks in advance.

over 7 years ago

0 Emrys Maier over 7 years ago

TI__Guru* 96752 points

There are some great application reports that go into detail on the 4046 PLLs that we offer.

This one specifically talks about FM demodulation (pg 17): CD4046B Phase-Locked Loop: A Versatile Building Block for Micropower Digital and Analog Applications

And this one is about FSK: Implementation of FSK Modulation and Demodulation using CD74HC4046A

Since these are analog devices, I'm not sure how you could get what you want (but I'm not saying it's impossible). The phase comparator output PWM is converted to an analog voltage through a low pass filter which then controls the VCO. That analog voltage essentially represents a range of frequency/phase offsets.

RF & microwave

RF & microwave forum

FM demodulation