Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Why can't I mix two signals of the same frequency?

Status
Not open for further replies.

namtey

New Member
Hi

I am trying to mix two seperate 250MHz signals to get a 500MHz output using a Mini-circuits ADE-1H+, but the output signal has severe amplitude variations. It works fine when the two input signals are of different frequencies, the amplitude fluctuations are only a problem when both signals are the same fequency.

Could somebody explain why this is the case, and whether it is possible to stop this?
 

audioguru

Well-Known Member
Most Helpful Member
The signals add and make double the amplitude of one. Then the phase changes and the signals subtract and cancel each other. So the output fluctuates in level.
 

MikeMl

Well-Known Member
Most Helpful Member
You are "mixing" them, but one is slightly a different frequency than the other, and what you are seeing is the "beat". The mixer generates the product Asin(ω1t) X Bsin(ω2t). Look up the trig identity to see what the product looks like. Now make ω1 and ω2 almost equal.
 

BrownOut

Banned
Stop it by using a single signal and a frequency doubler. You don't actually need two signals to get the double frequency.
 

namtey

New Member
That makes sense! I just realised that in the application the signals will be locked together so there would be no phase offset and hence no fluctuation in amplitude.

So for my test setup I will lock the 2 sig gens to a 10Mhz ref.

Thanks guys.
 

mvs sarma

Well-Known Member
Hi

I am trying to mix two seperate 250MHz signals to get a 500MHz output using a Mini-circuits ADE-1H+, but the output signal has severe amplitude variations. It works fine when the two input signals are of different frequencies, the amplitude fluctuations are only a problem when both signals are the same fequency.

Could somebody explain why this is the case, and whether it is possible to stop this?

No two things are identical. you can perhaps feed the same signal in both ports.
as already clarified by AudioGURU, you get twice the frequency.
 

MikeMl

Well-Known Member
Most Helpful Member
No two things are identical. you can perhaps feed the same signal in both ports.
as already clarified by AudioGURU, you get twice the frequency.
..., riding on top of a voltage level which is proportional to the phase difference between the voltages applied to the input signal ports of the mixer.
 
Status
Not open for further replies.

Latest threads

Top