| Popis: |
We describe the design, construction and performance of a novel 180° hybrid power divider for L-band (1.3-1.8 GHz). The hybrid is based on a double ridged waveguide cavity that also integrates a band pass filter. The device will operate at 77 K inside a cryogenically cooled receiver to be installed at the primary focus of the Sardinia Radio Telescope. The hybrid has three ports consisting of N-type coaxial connectors whose central pins are attached to launching probes located inside the double ridge waveguide structure. The signal is launched into the cavity from an input probe located on one cavity end and is extracted from two output probes on the opposite end. The output probes are arranged in balanced configuration, are axially symmetric, and aligned along the same axis. Both input and output probes are located in front of reactive loads consisting of shaped tunerless backshorts that provide broad band responses with low reflection coefficient. The band pass filter is located in the middle of the cavity, between the two input and output transitions. The dimensions of the device (excluding connectors) are 70 x 57.2 x 254.4 mm 3 . The design was optimized using a commercial electromagnetic simulator. From 1.3-1.8 GHz the measured output reflection coefficient was less than -17dB , the coupling and the phase difference between inputs and output was respectively, 3±0.25dB and 180 0 ±0.9 0 , over the full band. The amplitude and phase balance performances are much superior to that of commercially available devices. |
