| Beidou navigation system is independently developed by our country, can provide positioning, navigation and timing services for various users worldwide, and have the function of short message communication. Has now completed Regional network, and in 2012-12-27 began to provide service for the asia-pacific region. While the TD-LTE(Time Division Long Term Evolution) is the fourth generation(4G) mobile communication technology, which is our country with independent intellectual property rights, compared with traditional 2G, 3G network the system bandwidth, mobility, network delay, etc, have greatly improved. In order to further improve the performance of the beidou navigation system to implement the TD-LTE and beidou navigation technology and their synergy between applications, and services for various industries to provide high performance. Predictably, the fusion of these two technologies communication terminal will have broad prospect of application. The low noise amplifier is located in the front end of the wireless receiving device, the system noise factor plays a decisive role. Noise factor of the system is the main factors influencing the sensitivity of the receiving system, so the performance of the low noise amplifier has important influence on the overall performance of the equipment. Therefore, the LNA of TD-LTE wireless communication receiver front-end with beidou navigation technology design becomes a scientific problems needed to resolve.This paper designed a two cascade structure of low noise amplifier.The main research content is as follows:First, by comparing several implementations of multiband LNA, eventually identified with the method of broadband LNA to complete the design.Second, the transistor is the core of the LNA circuit, according to the noise coefficient and available gain of design frequency channel the transistor is determined. And according to the different bias condition of its performance parameters determine the static working point for the amplifier.Third, active device due to internal feedback, when the feedback amount reaches a certain degree, will produce oscillation amplifier, and even burn out. So this paper analyzes the method of judging the stability of the amplifier, and the commonly used to improve the stability of the measures.Fourth, the circuit structure of the amplifier is analyzed, due to the LNA need appropriate high gain, so the two cascade structure of the amplifier was designed. Because the amplifier is designed in this paper belongs to the broadband amplifier, and the transistor will work as the frequency increases with the decrease of the available gain, So the analysis of the broadband matching Q value factors and respectively according to the goals of before and after stage the design don’t have to determine the circuit structure,Using the agilent ADS simulation software design a 2-stage cascade low noise amplifier which work in 1.2-2.7GHz.The noise coefficient is less than 1.4, gain greater than 21.5dB, within the band gain flatness less than 1.1 dB, VSWRin less than 1.902, VSWRout less than 1.884.Work of this paper for the improvement of the performance of the beidou satellite navigation terminal design and has important scientific significance, will promote the development of China’s beidou navigation technology. |
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