A Compact Low-loss Single-layer Vialess Diplexer Based on Complementary Microstrip Spiral Resonators for Satellite Communications

The design of a compact low-loss diplexer based on complementary microstrip spiral resonators is described. The resonant elements are two: one is low-pass (channel A) and the other is passband (channel B). The low-pass element is composed of spirals departing from a circle, whereas the passband element is composed of spirals etched on a circle. The former element is novel and has been extensively analyzed here. These elements are connected using a star nonresonant Y-junction to form a single-layer vialess diplexer. As an example, a diplexer working at 0.87 and 2.0 GHz for satellite communications is manufactured and tested. The measured data show an insertion loss equal to 0.58 dB (0.66 dB) for channel A (B). The return loss exceeds 15 dB for both channels, and the dimensions are 0.129 lambda x 0.265 lambda approximate to 0.0343 lambda 2. 2 .