A Two-Port Microwave Component with Dual-Polarized Filtering Antenna and Single-Band Bandpass Filter Operations

This paper presents a two-port microwave component which behaves either as a dual-polarized filtering antenna or a single-band bandpass filter. For the dual-polarized antenna operation, a novel feeding network with a hook-shaped self-coupled line is employed for a pair of magneto-electric dipoles to obtain filtering radiation performance. This self-coupled line can not only ensure the impedance matching within the passband, but also can generate a radiation null at the upper-band-edge, further suppressing the out-of-band antenna radiation. Since no complex filter circuit is involved in the antenna function design, the in-band radiation performance of the antenna is nearly not affected. Thus, both satisfactory filtering and radiation performances are obtained. With respect to the filter operation, the magneto-electric dipole of the component does not radiate but functions as the ground of the feeding network, and the feed lines act as two resonators, forming a second-order bandpass filter. For demonstration, the two-port component with both antenna and filter operations is implemented and fabricated. The component has a measured average in-band gain of 7.6 dBi as an antenna, whereas it features a measured in-band insertion loss of less than 1.14 dB as a filter.