Tham khảo tài liệu 'antennas with non-foster matching networks phần 2', kỹ thuật - công nghệ, kĩ thuật viễn thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 6 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS FIGURE 2 Geometry of monopole antenna as modeled in Antenna Model software. The monopole is a copper cylinder m in length and meters in diameter mounted on an infinite perfect ground plane total quality factor of the antenna matching network combination is given by _ 1 o Q Q 8 where Qm is the quality factor of the matching network. However the loss in the matching network reduces the total efficiency of the system resulting in less total energy being coupled into free space. ANTENNAS WITH NON-FOSTERMATCHING NETWORKS 7 FIGURE 3 Real part of input impedance of the ESA monopole obtained from simulation FIGURE 4 Imaginary part of input impedance of the ESA monopole obtained from simulation 8 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS FIGURE 5 Radiation quality factor of the ESA monopole obtained from simulation FOSTER S REACTANCE THEOREM AND NON-FOSTER CIRCUIT ELEMENTS Foster s reactance theorem is a consequence of conservation of energy and states that for a lossless passive two-terminal device the slope of its reactance and susceptance plotted versus frequency must be strictly positive . ĨĨÍMÍ 2BÍ2Ỉ 0. dM 9m A device is called passive if it is not connected to a power supply other than the signal source. Such a two-terminal device or one-port network can be realized by ideal inductors ideal capacitors or a combination thereof. It turns out that a corollary that follows from Foster s reactance theorem is even more important than the theorem itself. The corollary states that the poles and zeros of the reactance and susceptance function must alternate. By analytic continuity we can generalize this corollary of Foster s reactance theorem to state the following about immittance impedance .
