Radiation antenna method

In Section 22-5 we determined the attenuation of the fundamental mode on a weakly guiding, step-profile fiber due to radiation from a sinusoidal perturbation of the interface, using free-space antenna methods and correction factors. Here we consider the situation when the radiation field is well approximated by a single leaky mode, which can be realized by having an on-axis sinusoidal nonuniformity of the form of Eq. (22-14). The azimuthal symmetry ensures that only HEi leaky modes are excited. Further, the direction of radiation should coincide with the direction of the leaky-mode radiation [23]. If we represent the nonuniformity and the incident fundamental-mode fields by the induced current method, as in Section 22-5, the direction condition is satisfied by setting C = in Eq. (24-43), whence... 

In this first set of examples, we determine radiation from sources in free space , using the free-space radiation modes, and compare the results with the antenna methods of Chapter 21. 

Abstract A method of distance determination of evolved carbon stars is proposed and applied to six stars for which the terminal velocity of expansion and the angular size are obtained from the CO and HCN radio observations made at the Nobeyama Radio Observatory. The method assumes the radiation driven wind in spherical geometry. Within those small samples, however, two types of mass losing stars that are systematically different in the antenna temperature ratio Ta(CO)/T/i(HCN) 1, in the velocity ratio u(CO)/u(HCN) l, and in the angular size ratio 0(CO)/0(HCN) 1 seem to be present, suggesting nonspherical geometry of the outflow. 

In order to indicate the advantages of the 3-D WENO-TD method, the radiation capabilities of a 2 x 1 antenna array comprising circular patches above a dielectric (sr = 4.4) substrate are explored. Figure 6.5 presents the evolution of the Ez component between the two elements for various setups. Additionally, Table 6.2 gives the realization aspects along with the... 

In this section, the higher order FDTD methods are applied to basic three-dimensional (3-D) radiation and scattering problems that involve simple dipole antennas. As performed in Chapter 7, whenever possible numerical results are compared to reference data, alternative formulations are also taken into account. 

The input impedance of an antenna plays an important role in the matching of the source to the antenna. Knowledge of the impedance over the operating bandwidth is of concern. The real part of the impedance is primarily due to the radiation resistance, and in part due to the ohmic loss of the conductors. The radiation resistance is the equivalent resistance, which if connected to the source in place of the antenna absorbs the same power as radiated by the antenna. Impedance can be determined a number of ways. Use of the method of moments gives the most definitive results subject to modeling limitations. Method of moments software was discussed in the first part of Sec. 13.1.3. 

The actual form of the current distribution on a particular loop antenna maybe determined by performing a method of moments analysis, as discussed in two earlier sections. It is a straightforward procedure to find the input impedance, radiation pattern, and gain of a loop once the current distribution is known. Method of moments generated plots of the input impedance vs. loop radius may be found in Fig. 13.6 of Harrington (1968). 

Pattern optimization is another method that can be used to maximize radiation to the intended service area. The characteristics of the transmitting antenna are affected, sometimes greatly, by the presence of the supporting tower, if side-mounted, or by nearby tall obstructions (such as another transmitting tower) if top-mounted. Antenna manufacturers use various methods to reduce pattern distortions. These generally involve changing the orientation of the radiators with respect to the tower and adding parasitic elements. 

Open antenna systems offer a suitable method to apply microwave radiation to large-scale components, if it is impossible or too expensive to use closed ovens. Open antenna systems are often used with aeronautic or automotive structural parts. The equipment can vary depending on control necessities and the component geometry. 

The invention provides an optical method which permits, with the aid of 6 simple measurements, a conclusion regarding the suitability of antennas (groups which can absorb electromagnetic radiation) for incorporation into photoaddressable polymers. 

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