No abstract

No abstract

No abstract

The antenna radiates predominantly the E component of field with the cross polarization level below 13 dB.Next, radiation-pattern data are computed for the proposed feed. A half-wave dipole feed is also modeled for comparison. The parameters of the reflector are S ϭ 0.21, L ϭ 0.21, and ⌯ ϭ 0.65. Computed horizontal-plane (xy plane) patterns for both feeds are shown in Figure 3. It is clear that the front-to-back (F/B) ratio for the MLBT feed is better than the dipole feed. The directivity for the MLBT feed is 7.6 dBi, whereas that for the dipole feed is 6.9 dBi. The new feed results in some small cross polarization (suppressed below 18 dB).The second example given in Figure 4 has the same front-toback ratio for both feeds. To achieve this the height of the reflector, H is adjusted for each feed, and L is fixed. For the same F/B ratio, the reflector height for the MLBT feed is 34% shorter (H ϭ 0.65) than that for the dipole feed (H ϭ 0.98).The final model is generated by adjusting the length L and height H of the reflector for fixed F/B ratio, directivity, and beamwidth for both feeds. The pattern data for this case is shown in Figure 5. For fixed F/B ratio, directivity, and beamwidth of 15.5 dB, 7.6 dBi, and 100 o , the reflector dimension for the MLBT feed is 46% smaller than the dipole feed. The elevation-plane patterns for both feeds have been found to be almost identical. CONCLUSIONSA novel primary feed antenna is introduced for application with plane sheet metallic reflectors. Such a feed, when compared to a conventional half-wave dipole feed, can reduce the reflector dimension by almost half for fixed directivity, beamwidth, and front-to-back ratio. These antennas can also be used in conjunction with corner reflectors or other types of reflectors. IMPROVING THE COUPLED-MODE METHOD BY MEANS OF STEP FUNCTIONS: APPLICATION TO PARTIAL-HEIGHT ISOTROPIC OR