first harmonic filter circuit

[swh]

Hi every body;
I am having problem on designing a filter circuit which can pass only the first harmonic frequency what so ever signal is given.
let me clarify my ques.
I want to design a filter (single filter) which is capable of passing the first harmonic frequency when signal of differnt frequency with harmonics comes into its input terminals.

Is there any way to use automatic tuned notch filter.If yes please give me idea.
thank you.

 

[Styx]

look up phase-lock-loops that will be a good place to start

 

[Russlk]

Is this an analog signal? If so, what is the amplitude? Or, is it a logic level? There has to be limits on the frequency. What is it?

 

[Roff]

You can do it with a phaselocked loop (PLL) and a switched-capacitor filter. Or, if you have a PLL with a sinewave VCO, you won't need the switched-capacitor filter. This only works if your input frequency doesn't change too rapidly.

 

[swh]

harmonics illimianation circuit

Hi every body;
Most of you told me to use a PLL.
The signal is going to be from the guitar strings , analog ,.Will PLL work to pass only the fundamental frequency if in the input signal from any of the string is given.
I will waite for you helpfull answers.

 

[Roff]

I think it would be difficult to get a PLL to lock on to the fundamental of analog signals such as an electric guitar generates, especially considering the varying frequencies generated by the strings. I am not a guitar player, but I am guessing that, because of the nature of the pickups, an electric guitar would have much higher harmonic content than an acoustic one. Perhaps if your PLL had a VCO with a narrow deviation range, and you pretuned it to the expected fundamental frequency for each string, you might get it to work. An acoustic guitar might be much easier, but I don't really know.
I thought you were trying to extract a fundamental sine wave from a square wave of varying frequency, which is a different problem. You should always give as much information as possible in your original question.
Your best bet for a general solution would probably be a digital signal processor (DSP) running a fast fourier transform (FFT) algorithm, but I can't see anyone doing this in a week, even if he were experienced in digital signal processing.
Have you already tried to make a tuner but failed? If so, what did you try? Why did it not work? This will give us an idea of what doesn't work, so we don't duplicate you mistakes.

 

[swh]

circuit for Illiminating harmonics

Hi every body;
The idea for the designe of the project looks as follows;

let me starrt from the middle.
I have an mc68000 processor kit in our lab so i have a program which reads the loop in one period of a square wave. that means the square wave is an input to one of the input ports of the processor so the program will count a loop number as long as the input is a 5v (which is higher value of the square wave). When the input is changed to the lower value of the square wave then the loop terminates and compare the number of loops it had before with some standard values for each strings.
then it will desplay a message signal whether the guitar is tuned or not.
If the frequency from the guitar is the same as the standard ones the program loop will count the same number as the standard and desplay good.
So before i supply the signal from the guitar I have to convert it to square wave. And i built a circuit which change sinusoidal to a square wave , i have tried it using pure sine wave as an input.
The problem comes when using a signal from a guitar, because the signal has harmonics it is not a pure sine wave and i could not convert it to rectangular wave.
so i am stucked on this point please solve this problem.
Thank you.