Hi,

I do not understand the equations used in the mixer design guide "Mix_SE_Spect_Iso" for calculating the output IF impedance of the mixer.

For example, at the sum IF frequency:

ZoutUpConv=mix(SM.Vload,{1,1,1},SM.Mix)/1mA

Z_IF_UpConv=ZoutUpConv*HB.Zload[0]/(HB.Zload[0]-ZoutUpConv)

Please could someone help to explain how this method works?

Many thanks.

I do not understand the equations used in the mixer design guide "Mix_SE_Spect_Iso" for calculating the output IF impedance of the mixer.

For example, at the sum IF frequency:

ZoutUpConv=mix(SM.Vload,{1,1,1},SM.Mix)/1mA

Z_IF_UpConv=ZoutUpConv*HB.Zload[0]/(HB.Zload[0]-ZoutUpConv)

Please could someone help to explain how this method works?

Many thanks.

output port, at a small offset frequency (SS_Freq) from either the downconverted

or upconverterd signal. The voltage at the output node due to this current is

measured, and the output impedance is computed from the ratio of the

voltage to the current. The output impedance that is computed from

this technique is actually the parallel combination of the mixer's

output impedance and the load impedance. The output impedance of the

mixer may be obtained by applying the well-known equation for the

equivalent impedance of two parallel impedances Zp=Z1*Z2/(Z1+Z2). If

we know Zp and Z1, Z2=Zp*Z1/(Z1-Zp).

In this case, Zp = ZoutUpConv, Z_IF_UpConv =Z2, which is the impedance

we want to know, and Z1 = HB.Zload[0], which is the load impedance set

via a variable on the schematic.

ZoutUpConv is computed from the mix function, and the {1,1,1} syntax

picks the sum frequency of the two fundamentals plus the small-signal

mix frequency (SS_Freq). The current amplitude is set to 1 mA, but this

is still treated by the simulator as a small signal, so it doesn't

matter what you set the amplitude to.