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

[neazoi]

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?

 

[vfone]

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

 

[neazoi]

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

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

 

[dick_freebird]

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

 

[volker@muehlhaus]

since they are 2 (sidebands)

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?

 

[neazoi]

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?

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)

--- Updated Yesterday at 9:06 PM ---

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

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

 

[FvM]

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)

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.