Design And Research Of Broadband Vivaldi Antenna And Differential SPP Filter For Radio Astronomy

Radio astronomy is a discipline that studies the phenomena of the universe by studying the electromagnetic signals emitted by celestial bodies.Its main observation method is radio receiving technology,and its main observation equipment is a large-aperture radio telescope.The radio telescopes can break through the limitations of traditional optical telescopes and is not restricted by harsh all-weather conditions such as fog and clouds.Therefore,longer distances,wider fields of view,and all-weather astronomical observation can be achieved.Phase array feed is a key component of radio telescopes.How to design a broadband feed antenna with high common-mode rejection and multiple notches,as well as a filter unit with low insertion loss and miniaturization has become a research hotspot in recent years.Starting from exploring the key technologies of radio telescope phase array feeds,this paper focuses on improving the performance of radio telescope feed arrays and filter components in China,and conducts the following research contents:(1)A broadband Vivaldi array antenna based on a non-uniform T-shaped power divider is proposed.Firstly,a non-uniform transmission line is used to design a 1-to-4 wideband power divider.By using an exponential line instead of the traditional quarter-wavelength impedance conversion line,impedance matching in the wideband range can be achieved.Then a wideband Vivaldi antenna unit is designed to achieve good impedance matching by rationally designing the feeding structure.Finally,four Vivaldi antenna units are connected through a non-uniform T-shaped power divider to form an E-plane array.The designed Vivaldi array antenna has a-10 d B impedance bandwidth of 1-6 GHz and an in-band gain of5.7-11.3 d Bi.The radiation pattern is stable and end-fired.(2)An ultra-wideb and differential triple-notch Vivaldi antenna based on branch-loaded resonator is proposed.First,an ultra-wideband differential Vivaldi antenna with high common-mode rejection is designed,and its differential-mode operating band is 3.1-11 GHz.Then,to achieve the characteristics of triple-notch band,a pair of branch-loaded resonators and a pair of half-wavelength C-type resonators are respectively loaded on the inner and outer sides of the differential-feed micro-strip line.The three notch bands are:5.17-5.42,7.30-7.52,7.83-8.32 GHz,and the antenna gain in the notch band is negative.Since the three notch band located in the operating frequency band of WLAN systems and satellite communication systems,the electromagnetic interference of WLAN systems and satellite communication systems on radio observation equipment can be effectively suppressed.The designed differential triple-notch antenna can be applied to a phased array antenna to improve its observation sensitivity.(3)A wideband differential filter based on slotline surface plasmon polaritons(SPP)is proposed.The broadband differential filter is composed of a differential microstrip-to-slotline feeding structure,a sub-wavelength gradient slotline structure,and a slotline SPP waveguide structure.First,the high-pass characteristics and high common-mode rejection characteristics of the differential microstrip-to-slotline conversion structure are analyzed,and the key parameters and common-mode rejection mechanism that determine the lower cutoff frequency of the filter are found.Then,the dispersion characteristics of the slotted SPP waveguide unit are analyzed to determine the upper limit cutoff frequency of the filter.Finally,a sub-wavelength gradient groove structure is used to bridge the two structures to achieve a smooth transition from TEM mode to TE mode to SPP mode.The designed wideband differential SPP filter achieves a fractional bandwidth of 147.6%(the center frequency f₀is 4.2GHz),a common mode rejection of less than 40 d B in the frequency range of 0.1-20 GHz,and a wide differential mode upper stop-band up to 4.8f₀.