Subjects: Astronomy submitted time 2024-01-31 Cooperative journals: 《天文学报》
Abstract： Radio telescopes usually conduct continuous observation across a wide frequency range, but traditional phased array antenna designs struggle to meet the requirements of both wide band and large scanning volume. The development of tightly coupled antennas offers a novel approach for addressing these challenges. Accordingly, a wideband dual-polarized Vivaldi phased array feed has been designed. Firstly, a theoretical analysis of the tightly coupled principle is conducted, incorporating Wheeler's concept of continuous current and equivalent circuit. It reveals that the strong coupling between the antenna elements effectively expands the operational bandwidth of the Vivaldi phased array. Based on this, a wideband Vivaldi phased array feed composed of 8$\times$9 Vivaldi antenna elements with a operational frequency ranging from 2 to 8 GHz is designed. Furthermore, the phased array enables $\pm$45$^\circ$ scanning characteristics in both E-plane and H-plane. Finally, a prototype of the phased array is fabricated and measured. The measurement results are in good agreement with the simulated ones.
Subjects: Astronomy submitted time 2023-08-02 Cooperative journals: 《天文学报》
Abstract： As the key component of radio astronomy receiver system, the noise and gain performance of Low Noise Amplifier (LNA) have important influence on the sensitivity of receiver system. In this paper, a broadband LNA which can cover the C-band (4--8\;GHz) is developed by using the 100\;nm gallium arsenide (GaAs) pseudomorphic High Electron Mobility Transistor (pHEMT) technology. The amplifier adopts three-stage common source cascade amplifier topology and dual power supply structure. Measured results show that the average noise temperature of the amplifier is 60\;K in the frequency range of 4--8\;GHz with the lowest noise temperature of 50\;K being achieved at 5\;GHz. The gain is (31$\pm$1.5)\;dB in the whole bandwidth and the input and output return loss is better than 10\;dB. The chip area is 2.1$\times$1.1\;mm$^2$. This designed LNA can be used in the C-band radio astronomy receiver and satellite communication system.
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