Design of microstrip antenna with filtering characteristic for wireless communication systems

  Objectives  This paper studies the development of a microstrip antenna with both traditional radiation characteristic and good out-of-band rejection characteristic.

  Methods  Through the filter integrated design method, the microstrip antenna with filtering characteristic, composed of a microstrip antenna, a coupled line, and two resonators is designed. In addition to the capability of meeting the traditional antenna design requirements, the microstrip antenna shall have the external quality factor that is equal to the external quality factor of the last resonator of the band-pass filter, thus enabling it to still function as a filter after being used as a substitute of the last resonator of the filter; in the filter design, the coupled line acts as an admittance converter to realize the energy coupling between the filter resonator and the microstrip antenna.

  Results  The simulation results show that as the impedance bandwidth is 2.37-2.53 GHz, the gain variation within the impedance bandwidth is gentle, the maximum in-band gain deviation is about 0.5 dB, the maximum gain is 7.5 dB, and the gain at 100 MHz outside the passband is rapidly reduced to -10 dBi, the microstrip antenna has good out-of-band rejection characteristic.

  Conclusions  The microstrip antenna with filtering characteristic designed in the paper reduces the overall size of filter and antenna and the transmission loss between the filter and the antenna, and can be used in modern communication systems.