Narrowband Filtering Balun Power Divider Based on SIW and CSRRs

A narrowband filtering balun power divider based on substrate integrated waveguide (SIW) and complementary split rings resonators (CSRRs) is proposed in this paper. The middle metal-grand of the SIW filter is used to achieve 180° phase difference. The forward-wave power division propagating below the characteristic cutoff frequency of the waveguide can be easily realized by four complementary split rings resonators. Good in-band performance (amplitude and phase imbalance are less than 0.16 dB and 2°) over the passband are implemented.