Novel microstrip antenna with rotatable patch fed by coaxial line for personal handy-phone system units

An enhanced microstrip antenna is proposed that incorporates a patch that rotates around the inner conductor of the coaxial line or dielectric shaft and a novel coaxial line feeding technique that offers constant electromagnetic coupling. This proposal addresses the disadvantages in our previous patch antenna in which the resonant frequency diverges from the center frequency of the personal handy-phone system (PHS) band and the bandwidth decreases as the patch rotates because of the changing electromagnetic coupling between the patch and microstrip line due to the patch rotation. We verify that this enhanced patch antenna achieves the antenna gain of approximately 0 dBd, which is the same as that of the previously proposed antenna, while suffering no significant gain degradation due to unit inclination over inclination angles from ±45° compared to a conventional quarter-wavelength whip antenna, which experiences a degradation of approximately 2.7 dB. We show that the maximum resonant frequency separation from the center frequency of the PHS band is reduced to 15 MHz from 31.4 MHz of the previous antenna using the novel coaxial line feeding technique. The effective bandwidth needed for PHS is achieved over the inclination angles of - 20° to + 40°. Approximately 93% of the total bandwidth needed for PHS is achieved while the previous microstrip line type achieved only 58% coverage; accordingly, an adequate bandwidth for PHS use is obtained.