PLL frequency synthetiser to generate a sinewave

[Hade]

Hi,

I have a project in which I have to design a sinewave within the frequency range of
1Mhz to 60Mhz. The design has to be done using a PLL synthetizer. Does anyone have an idea how to do it?
I though of using 74HC4046 PLL IC combined with the CD54HC4059 frequency divider to change the frequency. However, how can I get a sinewave from any specific frequency. Can these ICs do the job?

Any ideas!!!

 

[MikeMl]

If you just wanted a sine wave that was swept over a narrow range (say 50 to 60 MHz), then a square-wave VCO could be low-pass filtered to get rid of the harmonics to make a sine wave. Because of the wide sweep range you want, you should start with a sine-wave VCO, because otherwise the complexity of building a tunable low-pass filter will outweigh making the sine VCO in the first place.

 

[Hade]

If you just wanted a sine wave that was swept over a narrow range (say 50 to 60 MHz), then a square-wave VCO could be low-pass filtered to get rid of the harmonics to make a sine wave. Because of the wide sweep range you want, you should start with a sine-wave VCO, because otherwise the complexity of building a tunable low-pass filter will outweigh making the sine VCO in the first place.

Thanks MikeM,

For the sine VCO, which IC do you suggest and how would you procedd because it's still not very clear to me to get the problem solved.

 

[MikeMl]

It might have to be a Colpitts or Harley transistor oscillator with a Varicap diode; but it is going to be tough to get a 60:1 frequency range. You will have to bandswitch the oscillator, or have several oscillators where you select one appropriate for that range.

Another completely different idea is to start with a VHF VCO, say 201 to 260 MHz, and then mix it against a 200 MHz fixed Osc.

 

[Hade]

It might have to be a Colpitts or Harley transistor oscillator with a Varicap diode; but it is going to be tough to get a 60:1 frequency range. You will have to bandswitch the oscillator, or have several oscillators where you select one appropriate for that range.

Another completely different idea is to start with a VHF VCO, say 201 to 260 MHz, and then mix it against a 200 MHz fixed Osc.

Hi,
I am not sure if I understand bandswitching to do the job. I need more explanation.
As for VHF VCO, which IC can do that and the mixer that is compatible with it.
I really need more ideas because it is giving me problem. I have been able to get systems with square wave in the frequency range, but to get it to be sinusoidal that is what is the reel problem.

Need more !!!

 

[MikeMl]

Any Varicap-tunable LC oscillator is lucky to have more than a 3:1 tuning range, so it would take several oscillators to cover 1 to 60Mhz.

The output of a the correct mixer will be sinosoidal, as long as the inputs are.

 

[Hade]

Varicap option seems to be difficult as it will require the combination of many.
I'm going to read the mixer doc, however I would want know the VHF VCO that can go with. I haven't got a VCO at that frequency; I probably did not look for it properly.

 

[MikeMl]

Minicircuits VCOs