Microstrip Antenna Broadband Technology Research

Due to the development of the large capacity, broadband feature and intelligence in modern communication systems, the broadband technique of the microstrip antennas has been increasingly becoming a significant research field in last two decades. In addition, multi-frequency technologies of microstrip antennas also attract more and more attention of the experts and scholars.Transmission Line Model and Cavity Model, two conventional analysis methods were discussed. After all kinds of factors restricting the bandwidth of microstrip antennas were comprehensively analyzed, decreasing the Q of the equivalent circuit, adding additional resonant frequencies, use of the impedance matching network and changing the antennas' structure, the four main approaches for enhancing the bandwidth of microstrip antennas were presented. On basis of these main approaches, through HFss and Designer antenna simulation software, eight kinds of broadband microstrip patch antenna models were simulated whose bandwidth are much greater than the conventional microstrip antennas. The greatest bandwidth of these antenna models reaches 97 %(S₁₁ ≤ -10dB).At last, the basic methods for acquiring multi-frequency microstrip antennas and preliminary conception of antenna arrays were presented. On basis of multi-patch technique, a shared aperture dual band microstrip array was simulated by Designer software, which can operate in L- and X-band. The bandwidths of the antenna are separately 50MHz at L-band and 780MHz at X-band (S₁₁ ≤ -10dB). Moreover, the good radiation directivity both exists at two bands.Furthermore, with the application of multi-patch and LC loading technique, a shared aperture triple-band microstrip array was simulated by Designer software, which can operate in S and X band. There are two operational bands at S band and the bandwidths are separately 20MHz and 11MHz (S₁₁ ≤ -10dB). The bandwidth at X band reaches 800MHz (S₁₁ ≤ -10dB). Moreover, very good radiation characteristics were obtained at each operational band.