I can simulate the output impedance of the LO and the input impedance of the mixer. Now one could have the idea to put an impedance matching network between the LO and the mixer. But I haven’t seen a publication where somebody did this. I always thought, this is due to the close distance and that in this case impedance matching is not necessary.
Other thought: If impedance matching is useful even at close distances, then it should be also considered within a component. For example between two connected transistors in every RF component (LO, mixer, LNA ...). But this I haven’t seen also yet.