[SOLVED] Detection of frequency

[anandmeharwade]

Hi ,

I want detect the presence of input frequency at the input BNC connector which is ranging from 10kHz to 10MHz by the micro controller. Could any one help me to achieve this task.

Thank you in advance.

Regards,
- Anand

 

[barry]

You could do an fft. You would probably need an external ADC for the frequencies you specify. Or, if you are looking for a particular frequency, you could just have an external BP filter and comparator.

 

[anandmeharwade]

Hi Barry,

Thank you for the reply.

I am thinking of using the phase frequency detector for the same. but I am not getting how to implement. Do you think it is possible with this, if yes could you help me out. I have selected a part MC100EP140 from ON semi.

Thanks in advance.

Regards,
- Anand

 

[barry]

Hi Barry,

Thank you for the reply.

I am thinking of using the phase frequency detector for the same. but I am not getting how to implement. Do you think it is possible with this, if yes could you help me out. I have selected a part MC100EP140 from ON semi.

Thanks in advance.

Regards,
- Anand

I think there might be several problems with using that device. First of all, it requires a reference frequency to compare to your incoming frequency. Second, it's an ECL part which means you'll need a device to convert the PECL level outputs to levels compatible with your micro. You can probably make this work, but I'm not sure it's the 'best' way to do it. Could you give us a little more detail about your system?

 

[anandmeharwade]

Thank you for reply,
Actually the requirement is to detect the presence of the input at the input BNC connector. This input signal frequency ranges from 10Khz to 10MHz.

 

[FvM]

detect the presence of the input at the input BNC connector. This input signal frequency ranges from 10Khz to 10MHz.

Sounds like a level threshold detector. So what's the intended detection voltage threshold?

 

[barry]

So you're not trying to detect a frequency as you originally posted, you're trying to detect a signal? That's quite different. As FvM points out, maybe what you want is a LEVEL detector.

 

[anandmeharwade]

Intended threshold should be less than 3.3V as I have to connect output detector to controller gpio which can withstand up to 3.3V and controller supply voltage is 3.3V. Could you please tell me any other precaution I need take before connecting it to controller gpio?. and Is there any method so that I can get HIGH/LOW at gpio when there is input signal and LOW/HIGH when there is no input signal. My input signal strength is min =13dBm and max 19dBm
Thank you

 

[barry]

You are making this way harder than it has to be. All you need is a rectifier, RC and comparator.

 

[anandmeharwade]

Thank you very much barry, its great. I appreciate ur help..