This paper presents a 3D topology for high miniaturization of the well-known hybrid branch-line coupler at the UHF band. A preliminary work already proposed the use of helical-microstrip TLs combined with a folded structure for this purpose. This extended work includes a compactness enhancement by loading the TL segments with capacitors. An study of loaded helical-microstrip TL is reported as well. The coupler prototypes have been simulated and fabricated by using a combination of Additive Manufacturing and copper electroplating. The performance results have been compared to the conventional model showing a good agreement. In order to place the designed devices within the state of the art a figure of merit that combines the compactness and the relative bandwidth has been proposed, showing very good results in terms of miniaturization.

A new design methodology for radiofrequency circuits is presented that includes electromagnetic (EM) simulation of the inductors into the optimization flow. This is achieved by previously generating the Pareto-optimal front (POF) of the inductors using EM simulation. Inductors are selected from the Pareto front and their S-parameter matrix is included in the circuit netlist that is simulated using an RF simulator. Generating the EM-simulated POF of inductors is computationally expensive, but once generated, it can be used for any circuit design. The methodology is illustrated both for a singleobjective and a multiobjective optimization of a low noise amplifier.

In this paper, a new methodology for the automated generation of the optimal performance trade-offs of integrated inductors is presented. The methodology combines a multiobjective optimization algorithm with electromagnetic simulation to get highly accurate results. A set of sized inductors is obtained showing the best performance trade-offs for a given technology. Unlike reported approaches for inductor synthesis, performance trade-offs are generated offline, i.e., before any specific inductance or quality factor are required. The tight efficiency versus accuracy trade-off of existing approaches is, in this way, avoided and performance evaluation via electromagnetic simulation becomes affordable.