Quality factor and absorption bandwidth of electrically small lossy structures

Abstract

A new quality factor (Qabs) characterising power absorption by electrically small structures ranging from antennas to lossy objects is defined. In analogy to the radiation quality factor (Qrad), which is evaluated using the antenna radiated fields in transmitting mode, Qabs is evaluated using the fields scattered by the absorbing structure. Similar to the known relationship between the antenna matching bandwidth (Bmatch) and Qrad, it is rigorously shown that for an electrically small lossless receiving antenna Qabs is inversely proportional to the absorption bandwidth (Babs) of the antenna. Based on a circuit model, it is then conjectured that the same Babs–Qabs relation is also valid in the cases of electrically small lossy antennas and objects that do not have terminals. Numerical examples are shown to demonstrate the validity of the presented Babs–Qabs relation.

A Complete Flow of Miniaturizing Coil Antennas Based on Matching Circuit

“…Therefore, an approach to widening the impedance bandwidth also must be under consideration when miniaturizing a CA. Afterwards, the Q-factor determining the efficiency of transmitted energy is an important index for the whole RF system to be paid attention to, as fabricating a CA as small as possible with a high Q-factor is also necessary for wide impedance bandwidth [9]. The traditional approach to making the CA resonate at 13.56 MHz by simply cascading a resistance of 50 Ohm and a certain capacitance due to the standard impedance matching of 50 Ohm at the source port (as shown in Figure 1) was abandoned.…”

“…lectronics 2021, 10, x FOR PEER REVIEW frequency of 13.56 MHz, making it even more difficult to transmit power approach to widening the impedance bandwidth also must be under consi miniaturizing a CA. Afterwards, the Q-factor determining the efficiency energy is an important index for the whole RF system to be paid attention to a CA as small as possible with a high Q-factor is also necessary for wide im width [9]. The traditional approach to making the CA resonate at 13.56 M cascading a resistance of 50 Ohm and a certain capacitance due to the standa matching of 50 Ohm at the source port (as shown in Figure 1) was abandon it still has some reference values for following investigations and compar success in transmitting and receiving power at a certain frequency [10].…”