How to calculate the output impedance of an adjustable RF amplifer to match the input of a mixer using SA605 chip?

I have an FM receiver design I wish to implement using the SA605 chip.

The stage before feeding the signal to the SA605 chip is an RF amplifier. I know I have to impedance match between each stage to obtain maximum power transfer, I am just not sure how one goes about in calculating the output impedance of an adjustable RF amplifier stage that uses LC tanks to tune between 88MHz to 108MHz.

My goal is to match the output impedance to the input impedance of the mixer of the chip. Furthermore, I have found online a couple of app notes discussing how to design the impedance network between the output of the RF stage to the input mixer of the SA605 chip but it is in respect to a specific frequency( n SA605.)

How would one select the frequency of the mixer? Note a local oscillator is also mixed with the RF signal, which will be adjusted respectively to maintain a constant 10.7MHz intermediate frequency.

• View your challenge as achieving a large voltage swing on a 10pF load (PCB trace + SA605 Cin) in parallel with thousands of ohms resistance. 1pf at 1GHz is -j159 ohms; 10pF at 100MHz is also -j159 ohms. Thus your load is close to pure capacitance, -j159 ohms. The Q is 20 or 30 or 40, thus your RF (low noise?) amplifier will set the bandwidth. Mar 1, 2018 at 4:40