How to double a variable freq

Hi
I need some help in designing a frequency doubler circuit. The requirement is that i have a signal comming from a motor which starts from 0hz till 1.2khz.
My plans is to quad the I/P frequency (using NAND gates & NOR) and then 1/2 it with a flip flop. Hence getting a doubled frequency.

Firstly i did managed to make a freq doubler circuit with a RC circuit but this can't work on a variable freq because it will overlap freq's.

How can I do this Plz guide

There are a few ways.

Have a look at PLL circuits (phase locked loop)
Sample the input frequency with a microcontroller and write some software that varies the output frequency vs input frequency (I have a product that does this for cars)
Use a Frequency to Voltage converter and a Voltage to Frequency converter together

will look into PLL

picbits said:

There are a few ways.

Have a look at PLL circuits (phase locked loop)
Sample the input frequency with a microcontroller and write some software that varies the output frequency vs input frequency (I have a product that does this for cars)
Use a Frequency to Voltage converter and a Voltage to Frequency converter together

Click to expand...

thanks for the reply. I'll look into PLL circuits. Why do i have to sample it? the input freq. is a square wave.
Plz let me know if i'm wrong.

Those were 4 different ways of doing it. I really should have put bullet points or numbers on them

1. use a PLL
or
2. Use a microcontroller

etc

If the doubled frequency doesn't have to be symetrical you can just trigger a one-shot at the rising edge and at the falling edge of the signal. This will give pulses at double the input frequency.

Thanks

Thats better now. Thanks i'll look into those and let you know if i got stuck.