The co-simulation techniques enable an efficient design of any 3D microwave circuit including lumped components or circuit networks. The interface between the 3D EM field simulator and the circuit simulator is facilitated by the use of discrete ports. The standard co-simulation approach is suitable for the design stage while the transient co-simulation might be more efficient for the analysis of the whole structure including all possible crosstalks between sub-circuits and potential influence of the housing box.
The balanced amplifier consists of two identical amplifiers in each branch, two Wilkinson dividers and two quarter-wavelength microstrip lines. All these components are comprised in a single CST MICROWAVE STUDIO block. A SPICE model is used for the chip, while the transistor package and the complete layout including SMD components are modeled as part of the 3D structure. The amplifier is simulated by transient co-simulation. Thus, the calculation of S-Parameters with multiple port excitations is avoided. Arbitrary excitation signals may be applied. In both cases, the resulting 3D fields can be obtained.