Simplified Filter Tuning Using Time Domain
应用文章
The increase in wireless communications services is forcing more and more channels into less frequency spectrum. To avoid interference, very stringent filtering requirements are being placed on all systems. These systems usually employ coupled resonator filters to handle the power levels and provide the needed isolation. The difficulty of tuning these filters quickly and accurately often limits manufacturers from increasing their production volumes and reducing manufacturing cost. In a coupled-resonator cavity-tuned filter, the center frequency of each resonator must be precisely tuned. The couplings between resonators must also be precisely set to achieve the proper passband response, low return loss (reflection), and small passband ripple. Setting coupling coefficients and tuning the resonators are as much art as science; often a trial-and-error adjustment process. Until now, there has been no alternative.