RF Antenna Impedance Matching Of Considering Parasitic Parameters

With the rapid development of radiocommunications, the communications devices’operating frequency is increasing, frequency band will become wider and wider, and therefore a higher demand for antenna’s performance. If the impedance of antenna’s load doesn’t match the impedance of the source, it will reduce the load power’s transmission efficiency and affect the quality of the transmission signal. Thus it is very important to achieve adaptive impedance matching rapidly and steadlyThe impedance matching network’s property which influenced by the element’s parasitics was studied in this paper. Narrowband and broadband matching of parasitic parameters will be made in single-stage and multi-stage matching network respectively, which can achieve the goal of the minimum reflection and the maximum power transmission.The principle of impedance matching is first introduced in this paper. The model based on the low-pass π-type impedance matching network was improved, the adjustable inductance and the adjustable capacitance was regulated in the matching network to achieve impedance matching with the antenna load. The impact of the element’s characteristics deviated from the ideal characteristics was considered in high frequency, we analyze the parasitic parameter of inductance and capacitance respectively. The inductance’s and capacitance’s equivalent circuit model is substituted in π-type low-pass impedance matching network, then the model was simplified to get a simplified model with considering the parasitic parameters.For the shortcoming that PSO is easy to fall into local minima and convergence accuracy is not high, SPSO, QPSO and RSWPSO’s convergent accuracy and convergent rate ware compared by using the testing function. The result proved that RSWPSO has higher convergent accuracy and faster convergent rate.In order to verify the feasibility of impedance matching with considering parasitic parameters, the algorithm with impedance matching was combined, the adaptive object function under different frequency and load in the narrowband and broadband was designed respectively, then we can get the component parameters quickly. The input impedance, load power, reflection coefficient and VSWR were analyzed, compare the similarities and differences over the impedance matching network with the ideal parameters, the non-simplified impedance matching network with the parasitic parameters and the simplified impedance matching network with the parasitic parameters. The results show that the simplified model with considering parasitic parameters has faster convergence rate than the previous model, and the matching accuracy meet the requirements.Taking into account the actual situation that the single-stage impedance matching used so less, the multi-stage matching network was promoted. Let’s take the three-stage and four-stage impedance matching network for example. In the case under considering parasitic, we can achieve a narrowband and broadband impedance matching in the three-stage and four-stage impedance matching network under different frequency and load, which proved the multi-stage impedance matching network has more stable property than the single-stage impedance matching network.