Square wave to Sine wave

[ohmstable]

converting a square wave to a sine wave

What is the best way to convert a square wave to a sine wave? I was thinking of putting it through a LPF. Basicly, I need to convert the square wave output of a PLL to a sine. Mind you, the square wave frequency is not fixed, it will be changing.

Any info would be appreciated.

thx

 

[cetc1525]

pll in square wave output sine wave

can you use the opamp?

 

[IanP]

convert square wave to sine wave

Probably the best you can do is to use min 3-pole active filter with its 3dB band below 2 * frequency.
Also, you can first convert square wave to triangular (less harmonics) and then use active LPF.

 

[hrkhari]

50hz wien bridge

Hi Guys:


For clarification, isn't square wave is observed to have mutiple odd order harmonics in frequency domain wheras a sine wave is observed to have a single harmonic at the desired frequency, wouldn't this conversion results in information loss?. Kindly clarify

Rgds

 

[echo47]

convert square wave to sine

How much frequency variation? If the variation is relatively small, then a fixed low-pass filter will work fine.

If the variation is large, then you could multiply the square wave frequency (perhaps using a PLL), and use it to clock a switched-capacitor low-pass filter.

Well hrkhari, you could feed the sine wave through a comparator to regenerate the square wave. Information created!

 

[ohmstable]

566 vco sinewave

How much frequency variation? If the variation is relatively small, then a fixed low-pass filter will work fine.

If the variation is large, then you could multiply the square wave frequency (perhaps using a PLL), and use it to clock a switched-capacitor low-pass filter.

Well hrkhari, you could feed the sine wave through a comparator to regenerate the square wave. Information created!

What i'm trying to do actually is convert the square wave of a PLL to sine. However the PLL will be tracking a changing frequency, so therefore the output of the PLL will be a square wave with varying frequency.

So what is a switched-capacitor LPF? where can I get info on this?

I was thinking of using the AD633 analog multiplier as a variable LPF but perhaps that is overkill and I was hoping there was an easier way of making a variable LPF??

 

[echo47]

low frequency pll 50hz

Here are some inexpensive switched-capacitor filters from Maxim:
**broken link removed**

If your frequency doesn't vary too much, then a fixed filter may be simpler. For example, if your square wave varies between 1000 and 1500 Hz, then use a fixed filter that passes below 1500 Hz and blocks above 2000 Hz.

How can a multiplier be a filter?

 

[ohmstable]

50hz square to sine wave

The signal will be varying quite a bit from prob 100hz to 10khz. I'll look into the switch-cap LPF.. thanks..

The AD633 analog multiplier IC can be used to multiply, divide, square signals.. plus it can be used as a voltage controlled amp/filter. It's does a lot.

https://www.analog.com/UploadedFiles/Data_Sheets/277093686AD633_e.pdf

 

[diegoisra]

how to changing square wave to sine wave

Why don't you try using a diferential amplifier, working on the limit of its max output amplitude?

 

[rx5]

sine wave square wave to sine wave

how about a square wave that is .02Hz?? can it be converted to a sine wave??

 

[echo47]

square wave to sine wave using pll

how about a square wave that is .02Hz?? can it be converted to a sine wave??

Sure! You simply need a very low frequency filter that rejects .06Hz and above.
Well, better make that .04Hz, just in case the square wave isn't perfectly square.

There are many other ways to do it, each with advantages and disadvantages

 

[jorgito]

square wave to sine wave

Hello,
If you can tolerate some distortion, double integration of the square wave can be usefull also. That way you get second degree parabolic arcs that are easy to filter.

 

[Longfuse]

square wave to sine wave lpf

Hello,
If you can tolerate some distortion, double integration of the square wave can be usefull also. That way you get second degree parabolic arcs that are easy to filter.

Double integration is something I've messed about with but amplitude of the sinusoidal waveform will vary with large frequency ranges so you need some sort of compression/auto-gain circuit.

 

[emreozer]

hows a square wave created from a sine wave

Hi,

I want to design a PLL for 50 Hz and it must has sinewave output.

What should I do?

Anybody tell me way?

Thanks

 

[melc]

square to sine wave conversion

Hi,

I want to design a PLL for 50 Hz and it must has sinewave output.

What should I do?

Anybody tell me way?

Thanks

You probably know how to get a 50Hz square wave from a PLL (even the PLL is the last way I've do it, but check the LM565 http://www.datasheetcatalog.net/datasheets_pdf/L/M/5/6/LM565.shtml

If the VCO is 250Khz guess how can be generated 50Hz with this PLL ?).

Imagine you get a 50Hz with three logic levels (like those used in LCD display). Then you filter it as discussed above with a high order LPF.

A finest approach is to transform the square into a triangle using a constant current charging-discharging integrator. Then you need a lower order LPF at the integrator output than for a square wave.

The third way is to use a multistage diode limiter, with the set points reconfiguring the sinusoidal signal envelope. The triangle signal will be cutted at the set points generating a sinusoidal signal with less than 10% distorsion. A simple RC filter at the limiter output will create a perfect sinusoidal signal. That methode will work with a large signal frequency variation as long the output filter is tuned.

The simplest way to get a stable 50Hz sinusoidal oscillation is Wien bridge with FET (or bulb) stabilisation.

The most precise way to get a 50Hz sinusoidal signal is DDS.

 

[emreozer]

I have to use PLL because 50 Hz signal source's frequency is changing.

Do you know any PLL that running at 50 Hz and it has sine wave output?

What do you advise me to obtain sine wave output from 50 Hz PLL circut? You know all PLL has square wave output.

thanks

Emre - emreozer1453@gmail.com