Transformer-less balanced mixer that does not change the phase?

A special application, calls for a:

1. transformer-less balanced mixer
2. that does not cause "serious" phase shifting from it's input to it's output
3. fed by a 3KHz local oscillator. Essentially, shifting the input RF spectrum to 2 output spectrums (DSB), separated by 6KHz, with the initial RF input spectrum to be suppressed.

I have tried this simple mixer, which does the above, but I cannot measure the output signals phase (which are 3KHz away from the initial RF input signal), since they are 2 (sidebands) and the scope shows a distorted waveform.

Any help to satisfy criteria 2. above?

Place this LPF at the IF output and you get rid of distortions.

vfone said:

Place this LPF at the IF output and you get rid of distortions.

Click to expand...

Output is not audio, it is shifted frequency RF by 3KHz (up and down)

How do you phase-match two different frequencies, more than once per least-multiple periodically?

neazoi said:

since they are 2 (sidebands)

Click to expand...

But isn't this what you expect from the mixer configuration with 3 kHz LO, to create two sidebands at +/- 3 kHz from the RF?

volker@muehlhaus said:

But isn't this what you expect from the mixer configuration with 3 kHz LO, to create two sidebands at +/- 3 kHz from the RF?

Click to expand...

This is if your LO is in RF. My LO is in AF, so I am using it as a3KHz RF shifter (up and down)

dick_freebird said:

How do you phase-match two different frequencies, more than once per least-multiple periodically?

Click to expand...

This is an issue yes. I hope that two HF frequencies (eg 10MHz) spaced by only 3KHz apart, will have a very small phase difference. I am counting on this assumption, but it has to be verified, how many degrees those signals will be off

neazoi said:

This is if your LO is in RF. My LO is in AF, so I am using it as a 3KHz RF shifter (up and down)

Click to expand...

No. First order mixer product is RF + LO and RF - LO, two signal frequencies. Instantaneous values of both signals (if you watch them separately) are permantly shifting phase against each other. If you watch the sum, you see a RF signal that switches phase every AF half cycle. To get a steady output signal with fixed phase, you need a SSB mixer.