Loaded miniature transmission lines compatible with low cost substrates: Q-factor improvement

Loading transmission lines by capacitors is an effective way of miniaturization. However, it exists generally a trade-off between miniaturization and performances. In this paper, a careful comparison is carried out between a loaded transmission line and an equivalent unloaded one. Results show that a high miniaturization percentage can be achieved (55%) on a low cost substrate, together with an improved quality factor (47%). This idea is confirmed by improving the performance of a classical Dual-Behavior Resonator (DBR) with loaded transmission lines. Results clearly confirm the compatibility of the miniature loaded transmission lines with low cost substrates rather than good quality high cost one.