The fringing fields around the antenna can help explain why the microstrip antenna radiates. Consider the side view of a patch antenna, shown in Figure below. Note that since the current at the end of the patch is zero (open circuit end), the current is maximum at the center of the half-wave patch and (theoretically) zero at the beginning of the patch.

This low current value at the feed explains in part why the impedance is high when fed at the end (we'll address this again later). Since the patch antenna can be viewed as an open circuited transmission line, the voltage reflection coefficient will be 1 (see the for more information). When this occurs, the voltage and current are out of phase. Hence, at the end of the patch the voltage is at a maximum (say +V volts).

At the start of the patch antenna (a half-wavelength away), the voltage must be at minimum (-V Volts). Hence, the fields underneath the patch will resemble that of Figure 4, which roughly displays the fringing of the fields around the edges.

Side view of patch antenna with E-fields shown underneath. It is the fringing fields that are responsible for the radiation. Note that the fringing fields near the surface of the patch antenna are both in the +y direction. Hence, the fringing(किनारे की तरफ ) E-fields on the edge of the microstrip antenna add up in phase and produce the radiation of the microstrip antenna. This paragraph is critical to understanding the patch antenna.

The current adds up in phase on the patch antenna as well; however, an equal current but with opposite direction is on the ground plane, which cancels the radiation. This also explains why the microstrip antenna radiates but the microstrip transmission line does not. The microstrip antenna's radiation arises from the fringing fields, which are due to the advantageous voltage distribution; hence the radiation arises due to the voltage and not the current. The patch antenna is therefore a 'voltage radiator', as opposed to the, which radiate because the currents add up in phase and are therefore 'current radiators'.

As a side note, the smaller.

Advanced Mechanics Materials Cook Young Pdf Writer. Fringing Effects. The dimensions of the patch are finite along the length and width, so the fields at the edges of the patch undergo fringing. This is illustrated along the length in Figures 5.9 for the two radiating slots of the microstrip antenna. The amount of fringing is a function of the dimensions of the patch and the height. The Basics of Patch Antennas. Properties Of A Basic Microstrip Patch A microstrip or patch antenna is a low-profile antenna that has a. Zaitoon Ka Encyclopedia Urdu Pdf Library. Fringe field fringe.