RF mixers and phase relationships.

Thread Starter

Richardgr

Joined Jun 12, 2017
6
Hi,
I am new to RF-mixers, and i read that RF mixers should maintain the amplitude and phase relationship from the RF-input signal (Linearity).

Do I use a wrong type of mixer, ore are there other ways of doing this. I can not get phase alignment.

If anyone can enlighten me on this subject, I wold appreciate it so much.

Data:
I am using the mixer “ADL5801”. My RF-in signal is 0dbm, 440Mhz.
My LO-inn signal is 0dbm 485Mhz.
My IF-out signal is filtered thru a 45Mhz crystal-filter.

I am not able to get any phase lock between RF-in and the 45Mhz.


Best Regards
Richard
 

DickCappels

Joined Aug 21, 2008
7,743
What, exactly, do you mean by phase alignment?

In most cases the mixer produces a product of two (or more?) inputs. Unless the two inputs are identical, the output will contain the input squared (twice the input frequency) -even that is not what I would call phase alignment.
 

Thread Starter

Richardgr

Joined Jun 12, 2017
6
Hi

I will try to explain a little clearer. I am not so god at this language.

I am trying to get a phase relationship between the RF-input and IF-output signal, I am only using one of the IF-output signals. The 45Mhz.

Although these are to different frequencies my belief was that this was how it would work:
The signals would not drift with respect to Itch-other.

Example:
if I measure the two signals with a scope, it wouldn't matter witch of the two I was triggering on, both would show clearly.

Another example:
If a frequency is divided with some flip-flops, to, fore say half its frequency, there would be a phase relationship between the two frequency. They wold follow Itch-other.

This is what I am trying to achive withe a RF-mixer.

I hope I can get to the bottom of this problem.

Best Regards
Richard
 

Ylli

Joined Nov 13, 2015
1,053
Example:
if I measure the two signals with a scope, it wouldn't matter witch of the two I was triggering on, both would show clearly.
This would only be the case if the IF output was an integral sub-multiple of the input frequency. e.g. If the RF input was 405 MHz and the IF output was 45 MHz (1/9 th), then the two waveforms would be phase consistant.
 

Ramussons

Joined May 3, 2013
1,064
There are 2 independent oscillators whose difference you are monitoring. Since the oscillators are free running, the sum/difference frequency will not phase lock with either oscillator.
The mixer has no role in this.
 
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