Figure 18 shows how inductors and capacitors can be used to change the impedance. Capacitors and inductors in series or parallel can be used to match the antenna to the desired impedance. If varying these factors is not possible or if the performance still needs to be improved, discreet components could be used to optimize the impedance. Thus by varying these factors it might be possible to improve the impedance match of the antenna. In some cases, such as with transmission line stub matching in RF circuits or input impedance matching to a feedline’s characteristic impedance, a graphical representation of impedance can aid impedance matching. smithplot( frequency, data ) creates a Smith chart based on frequency and data values. Size of ground plane, distance from antenna to ground plane, dimensions of antenna elements, feed point, and plastic casing are factors that can affect the impedance. The Smith chart is commonly used to display the relationship between a reflection coefficient, typically given as S11 or S22, and a normalized impedance. Dependent of the antenna type there are several possibilities to obtain optimum impedance at the correct frequency. If the resonance frequency is too high, the antenna length should be increased.Įven if the antenna resonates at the correct frequency it might not be well matched to the correct impedance. To find the reflection coefficient from impedance, we use the formula that we previously derived, where ZL Z L is the load impedance, and zL ZL Z0 z L Z L Z 0 is the normalized load impedance. Thus if the resonance frequency is to low, the antenna should be made shorter. The reflection coefficient can be found from impedance or admittance. Ideally the frequency which gives least reflection should be in the middle of the frequency band of interest. In the impedance matching operations, it assists in finding out. For resonant antennas the main factor is the length. This chart is helpful for merging the capability of both the impedance and admittance charts. There are several ways to tune an antenna to achieve better performance. especially built-in antennas, such as spring type, chip type, pcb or fpc type antenna. To be precise, all antennas need impedance matching when applied to products. Antenna Matching is very important work in client side, not only antenna supplier side.

Smith chart impedance matching