[SOLVED] Simple FSK circuit - Where to start with

[thanhFF]

Hi all,

I am doing a project to design and simulate a transmission circuit. The core of the circuit if a Colpitts Oscillator and a FSK modulator. The osc frequency is 30 Mhz. I am reading abt Oscillator, many documents abt that. But FSK very hard to find. I wanna get a simple circuit to start with. My question is Can we use CMOS transistors to make a FSK modulator(simple one), I saw on the net there are a lot of diagrams abt FSK but in block type, some using matlab to model FSK, some use PLLs..... I am very new with RF so got a lot of troubles at the beginning.

Any suggestions for me to start with this problem. Ah i am using Cadence SpectreRF to simulate.

Tks

 

[BigBoss]

FSK is digitally modulated frequency modulation..nothing else..
But modulating signal can be filtered before applying to reduce the spectrum explosion..
If you design a VCO, you may apply digital information signal directly or through a filter to Vtune input with appropriate DC voltage to shift the center frequency..
You may also use a PLL and change your Ref signal. etc..
There are many methods..

 

[varuniyengar]

Start with high level simulation by using Simulink block then go to ckt level is my opinion.

 

[vfone]

You can use the schematic below to generate two FSK datarates.

 

[varuniyengar]

vfone ckt works but thanhFF want to use cadence and ttl models to generate FSK

 

[thanhFF]

Tks all for replying me. Be honest, my knowledge in this are very narrow. Coz the courses i studying based on CMOS technology. So i just wanna make simple circuitry based on that also. But it seems that not easy like I thought. How about this? If i wanna build a simple FSK, which sub-circuits I should look at, and do research about.I am not using Simulink just Cadence only, is it possible?