探测宇宙黎明的浮动倍频程锥盘天线
A Floating Octave Bandwidth Cone-Disc Antenna for Detection of Cosmic Dawn
摘要：
射电天文学辐射计的关键组成部分是用来探测宇宙黎明号的红移21厘米信号的天线元件。我们描述了一个倍频程带宽锥盘天线的设计和性能，用于检测该信号在频带40至90 MHz。宇宙黎明信号被预测为宽带光谱特征，其数量级弱于天空和地面无线电亮度。因此，工程上的挑战是设计一种低频天线，能够提供高保真度的微弱宇宙信号，以及前景天空，接收器。天线特性不得因在天体辐射、地面辐射或接收机噪声上留下任何令人困惑的频谱特征而损害探测。本设计中的创新是使天线在电学上小于半波长，并且在足够大的水体的表面上操作它。小型锥盘天线下方的均匀和高介电常数介质导致消色差波束方向图、高辐射效率和最小不必要的混淆频谱特征。天线设计在WIPL-D和FEKO中进行了优化。一个原型的构建和部署在一个湖上，以验证其性能与现场测量。索引条款：天线测量，射电天文学，反射天线。
英文摘要：
The critical component of radio astronomy radiometers built to detect redshifted 21-cm signals from Cosmic Dawn is the antenna element. We describe the design and performance of an octave bandwidth cone disc antenna built to detect this signal in the band 40 to 90 MHz. The Cosmic Dawn signal is predicted to be a wideband spectral feature orders of magnitude weaker than sky and ground radio brightness. Thus, the engineering challenge is to design an antenna at low frequencies that is able to provide with high fidelity the faint cosmological signal, along with foreground sky, to the receiver. The antenna characteristics must not compromise detection by imprinting any confusing spectral features on the celestial radiation, ground emission or receiver noise. An innovation in the present design is making the antenna electrically smaller than half wavelength and operating it on the surface of a sufficiently large water body. The homogeneous and high permittivity medium beneath the small cone-disc antenna results in an achromatic beam pattern, high radiation efficiency and minimum unwanted confusing spectral features. The antenna design was optimized in WIPL-D and FEKO. A prototype was constructed and deployed on a lake to validate its performance with field measurements. Index Terms: Antenna measurements, radio astronomy, reflector antennas.
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