摘要
数字卫星电视直播业务是近十几年发展起来并且还在被广泛应用的卫星电视接收业务。与传统的陆基电视接收业务相比,它具有覆盖范围广、入户成本低、有条件接收和有偿付费等优点,因而自其问世以来,在美国、欧洲、日本等国家和地区迅速发展,现已形成庞大的产业链,而我国的数字卫星电视直播业务正处于起步阶段,具有广阔的市场前景。
本文所设计的Ku波段圆锥波纹喇叭馈源正是应用于数字卫星电视直播业务,它将作为高频头(Low Noise Block, LNB)的前端接收天线,用于照射偏置抛物面天线。它的性能好坏将决定整个偏置抛物面天线的性能,甚至最终决定卫星接收电视的收视质量。
本文的主要贡献与创新点归纳如下:
1.所设计的Ku波段圆锥波纹喇叭馈源电压驻波比小于1.35,优于国内外所报道同类天线的设计水平。当其照射于口径不小于35cm、焦径比( f /D )为0.6的偏置抛物面天线时,12.5GHz处增益大于32 dB,最大副瓣电平小于-28dB,适合应用于卫星电视直播业务,具有很好的性能。
2.在馈电结构中,引入了反射柱结构,实现了双线极化,并重点研究了反射柱对于馈电结构的作用。
3.考虑到所设计的Ku波段圆锥波纹喇叭馈源要与后续微带电路相连接,使用了对同轴填充介质倒45角、探针倒135角的结构,保证天线两根探针的输出端在同一平面上,并对填充介质采用阶梯结构,便于安装。
Direct broadcast service of digital satellite TV appears in recent years and is now still widely used for the reception of satellite TV. Compared to the traditional land-based TV, it has many advantages, such as wide coverage, low cost entering the family, conditional reception and repay, etc. Therefore, since it came out it developed rapidly in U.S.A., Europe, Japan, etc. It has already formed the huge industry chain. But in our country, it is at the starting stage, and has broad market prospects.
The Ku-band conical waveguide receiving antenna, which is designed in this paper, will be applied to the direct broadcast service of digital satellite TV. It is the front of Low Noise Block (LNB), used for illuminating the offset parabolic antenna. Its performance determines the whole performance of the offset parabolic antenna, even though the reception quality of the satellite TV.
The main contribution and innovation is as follows:
1. The designed antenna’s VSWR is smaller than 1.35, which is superior to the reported design level of the similar antenna both at home and abroad. When it used for illuminating the offset parabolic antenna, which aperture is not less than 35cm and focal length to diameter ratio is 0.6, the whole antenna’s gain should be higher than 32 dB and its maximum sidelobe level should be less than -28 dB. It has very good performance and suitable for applying to direct broadcast service.
2. In the feed structure, we introduce the reflect-cylinder structure to realize dual linear polarization, and study the function of the reflect-cylinder structure.
3. Considering the designed antenna should be connected with the microstrip of LNB, we use the structure, which the substrate with 45 angle and the probe with 135 angle, to make sure the outputs of the two probes are on the same plane. We also use the stepped substrate structure to make it easy to install.
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