Spectral identification of non linear devices
A method of non-linear device identification derived from the measured spectral response to a sinusoidal drive is developed. From these considerations the concept of dynamic characteristics is proposed as a generalisation of the static characteristics. An example of the design of a frequency multiplying circuit based on the test spectrum is given. Important parameters such as internal capacitance and characteristic conductance are derived in terns of the components of the test spectrum. The effect of series resistance on the performance of exponential diodes is fully discussed. Three new diode models are proposed:-(i) a two-term functional expansion, (ii) a logarithmic approximation, (iii) a bi-linear model with, exponential correcting cusp. Model (iii) is used to develop expressions to predict the spectral response to a sinusoidal drive voltage and the importance of the curvature of the diode characteristic is discussed. The effect of parasitic capacitance on the performance of lattice mixers is examined and the resulting angle of delay in the diode current is predicted. A new spectrum analyser system is designed and developed which, is capable of measuring harmonic amplitudes and phases up to a maximum frequency of 1 GHz.