Hey Everyone,

I'm having trouble by finding suitable ICs for my project. I need a FSK or GFSK modulator with data input of 10Mbps and Output of 45 and 55MHz for the 0 and 1 binary values correspondingly. It really is my first electronics project and have been looking for it for a week and can't find anything suitable.

Thank you for the help.

 

The simplest solution would be to switch between two signal sources with a multiplexer. How well would that fit your needs?

 

May be a solution but how's the continuity with that? Thought about a VCO, where the binary data selects which frequency is in its output. Any thoughts about that?

 

You are looking for a device with a 10 Mbps, fsk, input and a 45-55 MHz fsk modulated output?

Please re-state clearly what you are doing.

 

May be a solution but how's the continuity with that? Thought about a VCO, where the binary data selects which frequency is in its output. Any thoughts about that?

Maybe a single counter with 45MHz and 55 MHz outputs.

A PLL can do it. TI has a few set up for FSK but you would have to divide the several hundred MHz output to get down to around 50 MHz. One problem I can see with using a PLL is that the modulation frequency is about 20% of carrier frequency, making getting a snappy response but clean response difficult. Shifting the input voltage open loop into a VCO should work very well.

There were or are some VCOs that can operate well around the frequencies in which you are interested -most of these are in PLL chips today.

 

You mean you want a 44 MHz out for space and 55 MHz out for mark?

I have a little DDS chip with 3 independent outputs. You could set one for 44 continuous and one for 55 continuous and then gate the two with the third output.

https://www.adafruit.com/products/2045

 

You are looking for a device with a 10 Mbps, fsk, input and a 45-55 MHz fsk modulated output?

Please re-state clearly what you are doing.

Thanks for the reply. What I need is a device with a binary data input of 10Mbps, which modulates that data using FSK, setting the value '0' to a frequency of 45MHz and the binary value '1' to 55MHz.

 

Maybe a single counter with 45MHz and 55 MHz outputs.

A PLL can do it. TI has a few set up for FSK but you would have to divide the several hundred MHz output to get down to around 50 MHz. One problem I can see with using a PLL is that the modulation frequency is about 20% of carrier frequency, making getting a snappy response but clean response difficult. Shifting the input voltage open loop into a VCO should work very well.

There were or are some VCOs that can operate well around the frequencies in which you are interested -most of these are in PLL chips today.

Thanks for the rely, I will look for those PLL chips and their specification and will keep you updated

 

You mean you want a 44 MHz out for space and 55 MHz out for mark?

I have a little DDS chip with 3 independent outputs. You could set one for 44 continuous and one for 55 continuous and then gate the two with the third output.

https://www.adafruit.com/products/2045

Actually your solution is good but I couldn't find the way to switch between the two output frequencies, according to the data stream.