Research On Harmonic Suppression Filters

With wide application of wireless technology, radio frequency RF engineers need to have a higher level of development and integration, as well as test and measurement technology for the development and production under the new standards. Wireless communication terminal devices become highly integrated and highly technological level, the RF terminal products will continue to development in complexity and size. Research and development engineers must provide solutions without sacrificing performance within a very small volume, in order to support the rapidly growing RF content. In communication systems, the design and manufacture of RF devices are faced with various challenges, such as high frequency, multiple frequencies, high performance, low interference, small volume and so on. To improve the performance of the communication systems, inhibit higher harmonics from external signals, mixers and oscillators and increase the sensitivity of the receiver, the filter must make its capacity of band rejection be better. Microwave filter with harmonic suppression have become one of the hot spots in the field of microwave technology.We write the thesis based on the processing test and pay more attention to the actual requirement of engineering, which mainly studies the harmonic suppression technology of cavity filters and strip-line filters based on traditional design and seeking to suppress the parasitic pass-band, in order to achieve high performance design.Firstly, we introduce the research status of microwave filters in detail, emphatically analyze the related transmission line theory which consists of the characteristics analysis of rectangular resonant cavities and suspended strip-line, in order to support the design process of thesis mentioned filters.Secondly, based on the aforementioned theory, we design two rectangular cavity filters with harmonic suppression. The former aims to broaden the stop-band by the way of changing the width of each cavity and regulating the coupling structure between cavities, so that the second resonance frequency of each cavity can shifted from each other. The latter uses symmetric cavity structure, we optimize the size of each cavities and coupling diaphragm so that the cavity parasitic pass-band deviate from 55 GHz-60 GHz.The latter was processed and tested, and resulting curves perform well, which verified the feasibility of project design.Once again, we make some improvements based on the traditional trapezoidal strip-line low-pass filter structures, adding metal patches to change coupling patterns, thus expanding the filter stop-band rejection beyond four times the center frequency, processing measured results agree well with the simulation and optimization results.Finally, we complete the summary of the full text research.