A Novel Differential Fed High Gain Patch Antenna Using Resonant Slot Loading

Inspired by slotted waveguide antennas, a pair of resonant slots is placed in the center out of phase region of TM30 mode rectangular patch antenna which acts as a new radiating edge. Superposition of radiated fields of TM30 mode patch and fundamental mode of slots results in high directivity radiator with reduced side lobe levels (SLL). It is shown that by making the resonant frequencies of patch and slots equal, good impedance matching and gain flatness can be achieved. The placement of resonant slots also has a slight adverse affect on the in phase current distribution resulting in asymmetric radiation pattern. It is demonstrated that a differential feeding scheme can be employed to achieve gain enhancement and symmetric radiation pattern by keeping the desired in phase current distribution intact. The proposed differential fed slot loaded patch antenna has symmetric radiation pattern with reduced cross polarization levels. It shows a measured gain of 12.8dBi, SLL of -12dB and S11≤ -10 dB impedance bandwidth of 21 MHz. The proposed antenna can be used as a substitute for 2x2 array of patch antenna operating in fundamental mode and is suitable for integration with differential circuits.