Help me with designing a mixer using Cadence(M1, M2 issue)

[joehwang]

Mixer design~

I want to design a single-balanced Mixer using CADENCE,
RF port is 1.8GHZ (single input)
LO port is 1.7GHZ (differential input)
IF port is 100MHZ (differential output)

I use a port cannect to the load as the IF port.
(both port terminals connect to the differential load)
I use one port in the LO level MOSFET(M1) and set the input 2V peak-to-peak.
I use one port in the other LO level MOSFET(M2), still 2V peak-to-peak,
but 180 phase shift to make LO input differential.
Both LO ports connect to GND.
I use one port in the RF level MOSFET(M3) with 1mV(-60dB) RF input signal.
M3 is the tail current source for the Mixer.
So, I use PSS to see the Gc(voltage gain from RF to IF)

Original, I set the width of M1 and M2 380um (M2 is also 380um).
I got the amplitude at IF~=-55dB(100MHZ), so Gc~= 5dB.
However, it does not match my hand calculation.
gm(M3)~=30mA, RL=1K, so Gc should be Gc=gm3*RL*2/pi~=25dB.

So, I change the width of M1 and M2 to 100um.
I got Gc~=17dB.(I got IF~=-43dB at 100MHZ).

However, I think it makes no sense, because when I decrease width of M1 and M2,
I am decreasing gm2 and gm3, so that decreasing the speed of turn on-off time
of M1 and M2. It should result in lower Gc, but I got higher Gc!

Is there anything wrong or I connect something wrong?
Or, it makes sense? If yes,why??

Actually, I do not know how to choose the width of M1 and M2.

I really need help~
Thank you so so much!