The Study On Broadband Matching Of The Antenna Based On The Improved Simplified Real Frequency Technique

In recent years,the mobile communication technology has been developing rapidly.As the key part of mobile communication system,the performance of antenna will affect the working condition of the whole communication system.And with the emergence of the new frequency band,it is necessary to install the antenna adaptable to different frequency bands at the same time.In order to reduce the number of the antennas,reduce the cost,save space and avoid the interference between these antennas,it is necessary to develop broadband antenna to make the antenna cover multiple working bands at the same time.The purpose of the broadband matching is to achieve the maximum power transmission from the source to the load in the considered frequency band of the RF system.So this method can be used as a way to achieve the broadband antenna.The broadband matching problem exists in various electronic systems,such as the antennas and the power amplifiers.Its purpose is to build a broadband matching network between the source and the load to reduce the reflected power.As an effective method for the design of the broadband matching network,the simplified real frequency technique does not need to calculate the equivalent model of the load and presuppose the topologies of the matching networks.It uses the normalized scattering parameters to describe the network to be designed and combines the reflection coefficient of the load to construct the function of the transducer power gain.The optimization algorithm is used to optimize this function and acquire the maximum transmission power gain in the frequency range of the interest.The main research work of this paper includes the following aspects:1.This paper studies the basic algorithm of the classic simplified real frequency technique.This technique uses the Levenberg-Marquardt algorithm to optimize the transducer power gain and the optimization result of this algorithm can be easily affected by the initial values,resulting in the need for the initial values provided by the experience and more debugging in the design of the matching networks.Based on these defects,this paper introduces a stochastic optimization algorithm,the invasive weed optimization,to acquire a new hybrid optimization algorithm and then uses this hybrid algorithm to improve the simplified real frequency technique.2.The design result of the classic simplified real frequency is a matching network of lumped parameters.In low frequencies,this form of matching networks can work well.But in high frequencies,the capacitor and the inductor have the distributed parameter effects and the distance among the components can not be ignored.Therefore,this paper offers an additive procedure transforming the passive matching network of lumped parameter into the equivalent microstrip circuit.It makes the matching network not only adapt to the condition of the high frequency well,but also can be integrated with the antenna to fabricate.3.This paper designs and simulates a rectangular dielectric resonator antenna according to the IEEE 802.11a standard.In order to make this antenna reach the required bandwidth of IEEE 802.11a,the improved simplified real frequency technique proposed in this paper is used to design a matching network.The simulation result of the matched antenna system is acquired by using the circuit simulation software.The simulation results show that the matching effect is good and the relative bandwidth is increased by 44.3%.4.A double-sided printed dipole base station antenna is designed and optimized.The-10dB bandwidth of this antenna is 0.763?0.924GHz.The broadband matching network is designed by the improved simplified real frequency technique,and the matching antenna system is fabricated and tested.The test results show that the bandwidth of the matched antenna is 0.728-1.01 GHz and can cover the bandwidth of both the CDMA and GSM-900 simultaneously.