Analysis And Design Of Filter In Wireless Communication Systerm

The filter that can filter frequency in high-performance oscillation, amplification, frequency-doubling,mixer circuits,is an important RF component in wireless communication circuits. In addition, it is very useful in effective broadband impedance matching networks and coupling structures. In order to suppress the external signals and the high-order harmonic produced by oscillators and other devices, filters with well harmonic suppression ability are necessary.In this paper, a method based on Newton's iterative algorithm successive linear approximation method is proposed to solve the problem of center frequency offset and bandwidth changing in traditional design of the parallel-coupled filter. Procedures that can greatly improve design efficiency are designed in MATLAB.The paper presents a linear and successive approximation method that can achieve the expected design results throuth linear adjustment of the initial design specifications, compared with the traditional design method or software design, the desired performance can be achieved more faster. Examples of two high-performance band-pass filter working in the X-band and S-band are achieved more faster with the introduction of successive linear approximation method in compatation with the traditional method.The two design examples demonstrate the accuracy, effectiveness and feasibility of the successive linear approximation method.The half-wavelength SIR stripline parallel-coupled band-pass filter with the same and different impedance ratio are designed. By controlling the impedance ratio of SIR, the high-order harmonic are controled and the first spurious response in 2.5f0 above. At the same time, the hairpin-shaped structure is adopted in all the unit resonator of the filters to reduce the filter size. Design examples in Chapter IV which are simulated and optimizated by ADS2008(Advanced Design Systerm)validate the design method.Then, examples are simulated in electromagnetic simulation,which provide feasibility for the physical production. In addition, two structures of the SIR-BPF are in compation. Finally, the tow structures of SIR-BPF both enabled the first harmonic appear in the location 2.5f0 above. But, the comparation between the two structures shows that the structure with the same impedance ratio has a better in-band characteristic and a more far away harmonic,and the structure with different impedance ratio can suppress the harmonic in greater deep degree.