A resonator and filter including the resonator is disclosed. The resonator (100) includes an open conductive loop (100) with folded transmission line segments (124, 134) extending from the adjacent ends of the loop. Of each transmission line segment, the portion emanating from the respective end of the loop is positioned generally along-side the corresponding portion of the other transmission line segment. That is, the two transmission line segments are folded away from each other. The resonator can be generally elongated in shape, with the loop at one end of the long axis and the transmission line segments at the other. The transmission line segments occupy a footprint (W2) that is not substantially greater than the width of the loop (W1). The filter includes multiple resonators of the invention, each resonator being coupled to at least another or the resonators. The resonators can be positioned in a side-by-side fashion, with the long axes of the resonators parallel or anti-parallel to one another.