Design Of CMMB Terminal Internal Antenna

In recent years, the demand for radio and television reception has been slowly evolving from fixed to mobile receivers, so Mobile multimedia digital TV technology is emerged. Many countries have developed standards of mobile digital TV broadcasting. China has also launched CMMB (China Mobile Multimedia Broadcasting) standard. The standard requires the terminal to receive the frequency of electromagnetic waves in the UHF band from 470MHz to 860MHz. The band brings difficulties to CMMB terminal antenna design, because there is a contradiction between achieving broadband at a lower frequency and size of CMMB terminal, and this paper’s main job is to overcome this contradiction and achieve the design of CMMB terminal internal antenna. This paper summarizes the classical methods of antenna band broaden, and applies these methods to the lower band antenna designs, by improving, made two CMMB terminal internal antenna.The innovation of this paper and the main work as follows:(1) A low-profile wide-band monopole antenna. The antenna uses form of a monopole antenna in the the design process and the design is without media substrate, this can effectively broaden the bandwidth. The antenna consists of two parts, U-shaped bent piece is to improve the higher frequency performance of the antenna (bandwidth broadening 33%), metal floor of the trench structure is to improve the performance of lower frequency performance of the antenna (bandwidth broadening 33%), which make the antenna work on a wideband. The -6dB bandwidth of the antenna covers from 460MHz to 900MHz, the peak gain in this band are larger than 1.5dBi, the overall size of the antenna is 180mm x 120 mm x 5mm, so the design of CMMB terminal antenna meets the design requirements.(2) Meandering antenna with structure of ground branch. The microstrip antenna is taken as the antenna design model, with 1.6mm thickness of FR-4 substrate, the design of meandering lines is to effectively reduce the size of the antenna, while the design of structure with ground branch can make the antenna be resonant in the lower frequency band, which will broaden the antenna bandwidth. The-6dB bandwidth of the antenna covers from 466MHz to 930MHz, and the peak gain is greater than 1.6dBi, and the overall size of the antenna is 174mm x 120mm x 1.6mm, which makes the antenna can be inserted into the CMMB terminals.