The broadband reflectionless filtering and matching circuit operating with high transformation ratio

For matching transformed impedances, various methods are known in the literature that are used reactive, dissipative, and combined circuits. The operation of such circuits is possible either in a wide frequency band, but in the same standard paths, or in a narrow frequency band when matching impedances that differ from each other by a high transformation ratio. Unfortunately, with the help of known methods, it is impossible to matching impedances with a high transformation ratio and simultaneously to operating of the circuit in a wide frequency band. For a reflectionless high-pass filter, the task is to investigate the possibilities of expanding its operating frequencies band when matching impedances have high transformation ratio. For a typical reflectionless high-pass filter, the reflection coefficients of its two equivalent circuits operating in even and odd excitation modes are determined. They are used to find the frequency transmission coefficients for this device, as well as the transfer functions of the complex frequency. It is established that such device has a narrow band of operating frequencies when matching impedances have a high transformation ratio. Possible ways to expand the frequency band by introducing additional electromagnetic coupling to this device are considered. An absorbing filter-transformer with an additional electromagnetic coupling is investigated. The relations for calculating its main elements of the scheme are obtained. It is established that electromagnetic coupling in this device extends the operating frequencies band. Thus, when the magnetic coupling coefficient k tends to 1, this band can be expanded 1 1k2  times. The obtained theo- retical conclusions are fully confirmed by experimental results. The performed studies of reflectionless high-pass filter-transformer confirm the possibility of expanding the operating frequency band when matching impedances have high transformation. The proposed filter-transformer is recommended for use in the design of input matching circuits in power amplifiers using modern GaN transistors, for which broadband reflectionless matching is a necessary condition for eliminating parasitic excitations at low frequencies.