# Design of quad-ridge flare horn for L- to S band

[Examensarbete på avancerad nivå]

Currently there are number of radio-astronomical projects like VLBI2010, SKA and EVN aiming for 1:4 to 1:10 observational bandwidth. The current project presents design of Quad-Ridge Flare Horn (QRFH) for 1-4GHz band. The Horn utilizes coax line to quad-ridge waveguide transition and flared exponential section. Those two parts are first modeled and analyzed independently and then they are optimized together for achieving the desired antenna performance. The feeding part is implemented as coax line to quad-ridge waveguide transition. Airline and dielectric coaxial feeding approaches has been studied as alternatives for dual polarized quad ridge waveguide with impedance of 50Ω. The transition is terminated with back short. Two different parametric models were built in CST to evaluate the reflection coefficient and optimize it over 4:1 bandwidth. The flare section was modeled in MATLAB by using exponential function to match it over 4:1 bandwidth. Study and effect on horn antenna performance for different exponential opening rates of ridge profile and sidewall profile has been shown. Horn flare section of antenna was designed for two of the best models obtained in the first part. The first model feed horn antenna achieves constant beam width over 6.5:1 frequency bandwidth. The calculated aperture efficiency for axi-symetric paraboloid antenna is 60% using simulated beam patterns. Similarly, the second model feed horn achieves relatively constant beam width over 4:1 frequency bandwidth. The horn performance gives return loss > 10dB over the entire band and > 20dB from 1 to 2 GHz. Moreover, the simulated system performance of this horn antenna on the radio telescope also shows aperture efficiency of 60%. The proposed Quad-ridge horn antennas have been simulated using the commercial available software package CST Microwave studio.

**Nyckelord: **Antenna, quad-ridge horn, wide band, constant beam width horn, radio telescope feed, reflection coefficients, mutual couplings, radiation efficiency, radiation patterns, genetic algorithms optimization

Publikationen registrerades 2013-02-12. Den ändrades senast 2013-04-04

CPL ID: 173428

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