A Complete Set Of Passband Tapped Circuits And Practical Application Range

Abstract

Tapped resonant LC circuits are investigated here in order to determine, in both qualitative and quantitative ways, how they deviate from previously proposed models. Mismatch, frequency shift and bandwidth shrinkage are observed. Limits for practical use suggested. Moreover, two additional tapped individuals are offered and modeled for the benefit of complex load matching applications. Introduction: The tapped capacitor and tapped inductor circuits, shown in Fig. l(a) and (c), respectively, have the same kind of transfer function. They are sometimes called as capacitor or inductor transformers [l], or parallel transformerlike network [2]. Their advantage is to provide the selectivity of a passband LC circuit combined with the effect of a physical transformer. Clarke and Hess [2] have mentioned the two above circuits and it was shown that, if some conditions are met, the equivalent circuits may be those of Fig. l(b) and (d), respectively. The correspondence between the circuit elements and the models is provided in Table 1. The equivalent circuits possess a shunt LC and an ideal transformer. The presence of the transfoFmer opens up the possibility of matching a step impedance: n = R / R This is a substantial improvement over the single passband LC circuit, where, for maximum power transfer condition one must always have: RG=RL. G L' Furthermore, in Fig. l(b) and (d), it is immaterial which side of the circuit the generator is placed at; these circuits may then perform a step-up or a step-down impedance transformation. While not mentioned previously, both Fig. l(a) and (c) circuits are in a Pi-configuration. It follows that for each of these circuits a correspondent Tee-configuration may now be introduced, This is shown in Fig l(e) and (9). The new proposed models are those in Fig. l(f) and (h), respectively: a series LC and an ideal transformer. Again, equivalence between circuits and models may be seen in Table 1. All four options are capable of matching an impedance step and presenting a bandpass shape equivalent to that of an LC. This four topologies set may be extremely useful when matching a complex load [3]. By selecting the right circuit, one is able to look into either port and see any of the four basic elements: shunt C, series C, shunt L or series L. The best configuration for absorbing an specific existent parasitic reactance may then be elected. The matching of microwave transistors, antennas, optical devices -lasers or photodetectorsis a suggested utilization.