Superconducting Spiral Filters with Quasi-Elliptic Characteristic for Radio Astronomy

This paper presents integrated antennas, which can fulfill both the functions of an antenna and a power combiner, thus reducing the circuit loss. This will be useful for linear amplification using nonlinear components systems, where the circuit-level power-combiner losses degrade overall efficiency. Two antennas, which use a single-layer structure and a multilayer structure, respectively, are designed. Both antennas achieve good impedance-matching characteristics under both even- and odd-mode excitations. The single-layer antenna has a narrow bandwidth, and the even-mode radiated power at boresight is 33 and 26 dB lower than that of the odd-mode radiated power at the E- and H-plane, respectively, thus demonstrating the effective suppression of even-mode radiation. The other antenna using multilayer structure achieves a broad-band bandwidth (S-11 <- 10 dB) of 15.5% and 8% under the odd- and even-mode excitation, respectively. Across the bandwidth, broadside radiation patterns with low cross-polar levels (<-21 dB) are achieved under the odd-mode excitation, while the even-mode radiation is also suppressed.