# Can period of such signal be found.

1. Jan 11, 2012

### John Atkinson

How to find the period of two signals added for example:
if f= s1+s2 where s1 is a squre wave of (+ -) 1 A, period √6 secs and s2 is a square wave of (+ -) 1 A, period 1/√6 secs.

Is this signal periodic if not why?

Can anyone let me know about some link where I can learn all the examples of such type.

2. Jan 11, 2012

### vk6kro

]The signals will have a repeating (periodic) pattern if their periods are in a whole number ratio to each other.

So, you have a ratio of √6 divided by 1/√6. That is √6 times √6. Or 6.

It is easier to work this out if you use voltage instead of current. To add voltages, you can just put two voltage generators in series.

However this seems like homework, so you need to make an effort to do some of it yourself. (Them's the rules!)

I suggest you get a free copy of LTSpice and use this to work out these oddball problems.

There will be one square wave that is faster than the other.
So draw it out on paper.
The slower square wave goes to 1 volt and then has the faster one imposed on it, so the result is a sqaure wave between 0 volts and 2 volts.
Then the slow wave goes to -1 volt and the same thing happens, except from -2 volts to zero volts.

http://dl.dropbox.com/u/4222062/2%20sq%20waves.PNG [Broken]

Last edited by a moderator: May 5, 2017
3. Jan 12, 2012

### John Atkinson

It is not HW it is just one of the questions in class presentations for which I am curious to know how to find the period of the signal theoretically. Can you suggest me some book.

As you suggested about the signal to be voltage can you explain the same assuming it to be voltage. How to find the period as I want to clear my doubts.

Last edited by a moderator: May 5, 2017
4. Jan 12, 2012

### vk6kro

If you look at the diagram above, you will see that the period is the same as that of the lowest frequency square wave.

Once you establish that the two waveforms have a whole number relationship, then you can say this.

I can't suggest a book, but I think a piece of graph paper would be more useful.
Just draw the two waveforms and then go along and add them to get a graph like the one above.