Design Of New Type Double Radio Frequency Low Noise Amplifier Circuit Which With The Function Of Inner And Outer Antenna Switching

With the rapid development of modern wireless communication, the successful of the wireless communication in the commercial and take important reform, such as the3G network and high-quality RF receiver has been launched, RF and microwave communication has been widespread concern. On the other hand, multi-mode, multi-standard, multi-band receiver is one of primary targets in the future on industry research. The low noise amplifier (LNA) as receiver front-end core part needs to be lower noise figure, enough bandwidth, enough gain, good gain flatness and perfect out-of-band suppression, has become a low noise amplifier circuit shall meet the increasingly strict measure, how to coordinate the relationship between the various indicators is the difficult problem in the design.Through theoretical analysis. In this paper introduces one of using in GPS L1, L2band&GLONASS L1, L2band new type double radio frequency low noise amplifier circuit which with the function of inner and outer antenna switching. The low noise amplifying circuit uses dual channel combiners way, so as to achieve multi-mode multi-band reception function; the cascaded amplifying circuit topology in order to reduce the noise figure, at the same time, to reach the requirements of the gain; wherein change low-noise amplifier circuit structure, the use of a filter placed before the amplifier, significantly improved the amount of the out of band rejection, it has better anti-interference ability; and select ultra-low noise and has a high-gain amplifier tubes-NE3509M04.Selected the low loss tangent angle of the high-frequency board material. In addition, the hand-held receiver needs equipment within the external antenna switching function. When inner antenna signal is bad, we can use the outer antenna to ensure to receipted of the signal.The simulation results show that the new dual-frequency low-noise amplifier circuit has a low noise figure, high gain flatness and out of band rejection capability and stability.Finally, we also make the dual RF amplification circuit board, through to debugging and testing, to verify the correctness of the derivation of the theory and design techniques. The final test results:1. Operating bandwidth covering the GPS LI. L2band and GLONASS Gl. G2band;2. The first stage amplifying circuit noise figure(NF1≤0.7dB). Gain≥15.5dB; The total gain is greater than39dB;50MHz out of band rejection can reach more than45dB.5.inner and outer antenna has high isolation.Compared and analyzed simulation results with test; verified the correctness of the derivation of theoretical and design, which explains the new dual-frequency low-noise amplifier circuit has good features occupy in a smaller PCB area is very suitable for handheld high-precision positioning receiver.