Analysis of diode mixers using the method of node potentials in generalized matrix form in the frequency domain. Part 2. Isolation between ports, miscondition effect, noise level

A method for theoretical analysis of “input-output” and “local oscillator-output” decouplings of three types of diode frequency converters is presented: balanced, double balanced, triple balanced. For two operating modes of the local oscillator – “non-intensive” and “intensive” – the dependences of the “input-output” decoupling of the balanced mixer on the load conductivity and on the amplitude of the local oscillator voltage were obtained. Theoretical analysis and modeling were carried out. It is shown that the error between the calculated results and the simulation results does not exceed 3 dB. Expressions are obtained for errors introduced by the technological spread of diode parameters, which make it possible to estimate the maximum achievable values of the mixer characteristics (transmission coefficient and port isolation). A method for analyzing the noise properties of mixers is presented, the output noise spectra are calculated for each of the circuit elements (input resistance, diodes and output resistance), and analytical expressions for noise coefficients are obtained. Theoretical noise figure estimates are confirmed by simulation results with an accuracy of 1 dB.