| Currently, the coverage of DCS and WCDMA networks have been maturing. But with the rapid increase in the number of mobile users, the user density and traffic intensity significantly increase, which put forward more and more strict requirements on the quality of communication network coverage. In recent years, with the urbanization construction process speeding up, more and more tall buildings have been built in town, which make indoor communication quality become a new problem to the network service providers. So the indoor coverage build has become a focal point of network construction for the service providers. At the same time, WLAN has been widely used in the hospital, shops, factories and schools, which are not suitable for network cabling. DCS, WCDMA and WLAN are suitable for different scenarios and have different coverage ability, in the current multi-network integration business development background, they will coexist for a long time. So researching on DCS/WCDMA/WLAN indoor distribution system has higher theoretical and practical significance.In a indoor distribution system, includes indoor distributed antennas, multiplexers and low-noise amplifiers, and other devices.In this paper, the design and implementation method of the antenna, multiplexer and low-noise amplifier suitable for DCS/WCDMA/WLAN indoor distribution system were studied.In this paper, the three-layer stacked microstrip patch antenna structure was used for designing a broadband element antenna; and using three this kind element antennas to build up a triangular prism structure antenna array, which was feed by a wideband T-divider, to achieve omnidirectional radiation characteristics.The multiplexer was achieved by connecting three bandpass filters and each of them has different structure. By using the method that converting the tri-band multiplexer to two dual-band multiplexers to simplify the design process, finally, obtained good characteristics and with smaller size. Among them, DCS filter was designed by using a dual-mode resonator which contained a uniform impedance resonant ring loaded a "in" shaped stub; WCDMA filter is a generalized chebyshev filter, which was designed by using cross-coupling technology and 0° feed structure; WLAN filter was designed by the input/output coupling lines structure, and microstrip open stubs were adopted to achieve a good out-of-band rejection degree.The low-noise amplifier was designed by the ATF 54143 transistor of AVAGO company, which works in the band of 1.7～2.2GHz. In the low-noise amplifier design, the source series negative feedback technology was used to increase the stability of the circuit, drain parallel negative feedback technology was adopted to get a good gain flatness, and the n shape matching network was used for input and output matching, and finally, a wideband performance and low noise figure were achieved.In this paper, the design method of theoretical analysis combining with electromagnetic simulation software optimizing was adopted. According to the design results, the antenna, multiplexer and low noise amplifier were fabricated and measured. The tested results show that the gain of the antenna array is 1.93dBi, out-of-roundness is about ±1.64dB in the DCS band; the gain is 2.04dBi, out-of-roundness is about± 1.36dB in the WCDMA band; the gain is 2.3dBi, out-of-roundness is about±1.67dB in the WLAN band. The insertion losses of the multiplexer are less than 2.87dB within the DCS/WCDMA/WLAN frequency band, the isolation between different bands are more than 30dB, and with steep characteristic at each band’s edge, showing good frequency selectivity. The return loss of the low-noise amplifier is less than -13dB in the band, and it’s noise figure is less than 1.84dB, has a gain about 12dB, and has a good gain flatness. In summary, the antenna, multiplexer and low-noise amplifier basically reached the requirements of the design specifications. |
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