![]() Resonance Frequency and the Impedance Bandwidth of an AntennaĪt resonance, the magnitude of antenna impedance is maximum. At resonance, the antenna reactance is equal to zero. When the stored magnetic and electrical energy are equal in magnitude, it leads to a resonance condition in the antenna. The antenna reactance indicates the stored energy around the antenna, the energy that is present in the near zone. The radiation efficiency is also dependent on the radiation and loss R l is the resistance of the antenna due to heat dissipation and R r is the resistance of the antenna depicting radiation loss. The antenna resistance R a can be resolved as presented: ![]() The real part of the antenna R a is due to heat dissipation and radiation loss. R a is the resistance of the antenna and X a is the reactance of the antenna. The ratio of voltage to current at terminals a and b give the antenna impedance Za : The ratio of appropriate components of electric and magnetic fields at a point also present antenna impedance.Ĭonsider an antenna with terminals a and b with no load connected. This impedance can be determined as the ratio of voltage to current at the antenna terminals. Antenna ImpedanceĪntenna impedance is the impedance measured at the terminals of an antenna. In this article, we will discuss antenna impedance, resonance frequency and impedance bandwith, and how to measure the antenna impedance. It is important to measure the antenna impedance to ensure the impedance matches the feedline impedance using matching networks. The bandwidth of the antenna is also dependent on the antenna impedance. Matching the antenna impedance with the system impedance is critical for maximum power transfer, as an antenna transmits or receives maximum power when the impedance is matched. ![]() ![]() Matching the antenna impedance with the system impedance is critical for maximum power transferĪntenna impedance is a significant parameter influencing the performance of communication systems. The impedance measured at the terminals of an antenna can be defined as antenna impedance.Īt resonance, the magnitude of antenna impedance is maximum.Īntenna impedance measurements can be obtained using a vector network analyzer, impedance bridge method, or the slotted line method. ![]()
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