HTS Microstrip Hybrid Couplers for Radio Astronomy C-Band Receivers

Critical upgrades of microwave hybrid directional couplers with wideband specifications in C band receiver for e-MERLIN telescope array at Jodrell Bank Observatory, UK, are required to achieve extremely low insertion loss and a reduction in receiver size. A High temperature superconducting (HTS) 3-section tandem coupled-line 3dB hybrid coupler and an HTS Lange coupler with a bandwidth of 53% and 48.5%, respectively, were designed on MgO substrates. The measured performance agrees well with the simulated one over the band of interest. The insertion loss of these HTS couplers are only 0.1-0.2dB as expected. The HTS Lange coupler has been successfully operated in the receiver on the telescope for over a year.