AM Mixer Design Help

Hi,
I am trying to design an AM active mixer in double balanced gilbert cell configuration. I have the proper signals (power+ DC bias) given to both RF inputs and LO inputs but I seem to get a negative conversion gain.

What could be the possible flaws that I would be making in it

Suggestions are welcome


Dan

In Gilbert mixers if the phasing of the RF an LO signals is not ok, you cannot get the gain which should be about 12dB.

thanks for the reply
i believe I am giving the inputs(power level with right phases+dc level) for both RF inputs(left with RF+ and right with RF-) (the bottom differential pair) and LO+ inputs [(top leftmost & top rightmost) &(the rest two middle transistors with LO- inputs)

I could see the IF i needed in the output which is 455kHz for a suitable RF and LO frequency. But the power level of IF is almost 100 times(linear scale) lower than RF level. I dont know where the issue is, as I never designed a mixer before.

The cad tool I use is ADS

Dan

Try to post a picture of the schematic and might get a help from somebody...

here is the picture

Dan