A Varactor-tunable Filter with Constant Bandwidth and Loss 一个恒定的带宽和损耗变容二极管调谐滤波器.pdf

A Varactor-tunable Filter with Constant Bandwidth and Loss Compensation | April 6, 2... Page 1 of 19 April 2007 Issue : Technical Feature A Varactor-tunable Filter with Constant Bandwidth and Loss Compensation This article presents the basic concept and realization of a bandpass varactor-tunable filter with constant bandwidth and loss compensation. The filter components are based on step-impedance planar resonators, while the equalizing circuits of L- and T-types are lumped capacitances. The integration of the filter passive parts with a gain block is implemented to compensate for the insertion losses. Examples of practical realizations of two- and four-pole varactor-tunable filters in the 1.1 to 1.5 GHz frequency range are reported. by B. Kapilevich From: Vol. 50 l No. 4 | April 2007 | Pg.106- 4 Varactor-tunable filters attract the attention of microwave specialists due to a number of advantages that can improve the overall performance of communications and radar receivers, as well as measuring equipment. One of the drawbacks of such filters is a considerable variation in bandwidth (BW) and insertion losses (IL) within the tuning range. The problem can be solved by the proper design of equalizing circuits, providing stabilization of these parameters. This article describes the basic concept and realization of such an approach, when the filter components are using step-impedance resonators matched by L- and T-types of equalizing elements. Since implementing additional equalizers leads to increased insertion losses, a gain block, such as an LNA, is integrated with the passive filtering part to compensate for the loss. Basic Design Concept /Journal/Print.asp?Id=AR_4121 12/26/2007 A Varactor-tunable Filter with Constant Bandwidth and Loss Compensation | April 6, 2... Page