A Novel Broadband Microstrip Antenna Based on Operation of Multi-Resonant Modes

A novel broadband microstrip antenna under operation of TM_1/2,0, TM₁₀ and TM₁₂ modes through a shorting wall and slots is proposed in this paper. Initially, an inverted U-shaped slot is adopted around the feeding point, which achieves a good impedance matching on TM₁₀ mode and separates the patch into two parts. Additionally, a shorting wall is added underneath the edge of smaller patch to excite another one-quarter resonant mode, i.e., TM_1/2,0 mode of smaller patch close to TM₁₀ mode to expand the impedance bandwidth. Further, the antenna width is enlarged and two symmetrical vertical rectangular slots are cut on the patch to reduce the frequency of TM₁₂ mode to form a broadband. Based on the arrangements above, a wide impedance bandwidth with three minima can finally be achieved. The results show that the impedance bandwidth of proposed antenna for |S11|<-10 dB is extended to 26.5% (23.5-30.67 GHz), which is three times of the conventional antenna at same profile. Moreover, a stable radiation pattern at broadside direction is realized over the operating band.