A compact edge-fed filtering microstrip antenna with 0.2 dB equal-ripple response

A compact microstrip antenna with a second order 0.2 dB equal-ripple response and 4 % fractional bandwidth is proposed. This design follows the synthesis process of the bandpass filter. The radiating patch is fed by a new edge-fed gap-coupling mechanism. The coupling section excites the antenna, and it can be an admittance inverter for the filter design as well. Moreover, it does not occupy any additional circuit area. The proposed antenna has the size of 0.6λ_g × 0.6λ_g, where λ_g is the guiding wavelength in the substrate. The antenna provides good selectivity, flat in-band antenna gain response, and good out-band rejection. The measurement results agree with the simulated ones.