Impedance match between IC's blocks???

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Should i care the impedance match between Mixer and LO driver???
Why :?:
 

The only thing that is important is knowing the input impedance of the mixer LO port and also knowing if the LO driver can work into this load impedance and deliver the power required by the mixer.
 

Do you mean that i needn't carry out 50ohm or conjugate matching between Mixer and LO drivers???
but, How to deliver power when it is not match between blocks in IC???
 

Power always flows. Efficiency and cost are important items. Conjugate match is always way below 50% efficiency because half the power gets dissipated in the source circuit. This is added to the DC-AC conversion efficiency.

In a small signal path where efficiency is dismal (microvolt signals and volt level power supplies) maximum gain may be important, but this drastically narrows the bandwidth. It all depends on the application.


Video amplifiers loads are orders of magnitude below the output impedance of the transistor. This is why such wide band performance is obtained.
 

Mixer LO Input port impedance is never constant regarding to higher LO amplitude. To define input impedance of a mixer is never easy. Because input transistors work under large signal condition and input impedance will vary with the amplitude . Essentially conjugate matching is almost impossible.

Instead of this , I suggest you to use Buffer Amplifier to drive LO port of the Mixer. By using that , isolation between LO and Mixer LO port will be high to prevent disturbing the LO that will create Phase Noise ( it's very very important !!)

Look RFMD web site for a LO Buffer Amplifier.( as I remember it has 50dB isolation , means that S12=very small smth..)
 

So impedance match between LNA and Mixer is the same, or not???
Should i need to care the s22 of LNA? since the impedance of Mixer's RF port is very high.
 

I always put an on board filter for image frequency rejection between LNA and Mixer. Need to some on board match on LNA output and Mixer input.

For blocks inside a chip, should we care more about the voltage instead of power?
 

Hi,

Yes, you can use conjugate match. However, I suggest you to implement a buffer amplifer at LO output. It is because the input signal of mixer may leak to LO and make the LO getting distorted.

eecly
 

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