This paper presents a highly isolated diplexer-antenna and a dual-band filtenna with high-frequency selectivity. The precise design procedure for the diplexer based on substrate-integrated waveguide technology is presented and effectively integrated with magnetoelectric dipole antenna/microstrip patch antennas to achieve a diplexer-antenna and dual-band filtenna. The proposed configuration enables the design and control of the filtering response of the channels individually. To verify the proposed method, a diplexer-antenna and a dual-band filtenna with operating frequencies of 26.5–27.5 and 28.5–29.5 GHz, a fourth-degree Chebyshev response, and two symmetric radiation nulls for each band are designed and simulated. Finally, the proposed dual-band filtenna is fabricated and measured. The measured peak realized gains for the lower and higher bands are 4 and 4.5 dBi, respectively. Besides, a high out-of-band suppression with a deep roll-off of better than 20 dBi is obtained.

A compact high-isolation power divider with bandpass response and high-frequency selectivity is presented in this letter. Two dual-mode resonators are used to realize filtering response. The circuit size of the proposed power divider can be reduced by using dual-mode capacitance loaded square meander loop resonators. Due to capacitive load, the resonator can exhibit slow-wave characteristics, which can be utilized to suppress harmonics and reduce size. The simulated and measured results show reasonable agreement.

A wide-stopband bandpass-filtering power divider with high-frequency selectivity has been proposed in this paper. The input and output feeding lines and eight 1/4 wavelength resonators are used to realize the signal transmission. In order to obtain good frequency selectivity, source-load coupling transmission path is used to generate transmission zeros near the passband. A four-way power divider with bandpass-filtering response and high-frequency selectivity is designed, fabricated, and measured. The measured results agree with the simulated ones closely in the desirable frequency range. The measured center frequency of the power divider is 2.38 GHz with input return loss of 31.2 dB, while the measured insertion loss is about 1 dB (not including ideal 6 dB four-way power dividing insertion loss). Moreover, the measured 3-dB bandwidth is 12% and the measured stopband attenuation is >15 dB from 2.59 to 7.7 GHz. In addition, two transmission zeros of 1.9 and 2.8 GHz are located near the passband. The measured output isolations are all >15.7 dB.