Low Phase-Delay Reflection-type CRLH Band-Pass-Filter

In this paper, the authors propose the concept of the reflection-type composite right left handed (CRLH) filter to obtain low phase-delay in pass band. A lumped-element CRLH transmission line has stop bands and pass bands according to its lumped-element values. Therefore, it is a candidate of tunable filter configuration. But in pass band, transmission phase changes very rapidly when the number of unit CRLH cells increases. This is a fatal disadvantage for a communication device. On the other hand, reflection phase does not change so fast. The authors have realized this reflection property could be transferred to transmission property by combining with a hybrid circuit. Finally, the concept was verified by being implemented on a GaAs substrate. The result showed phase change was less than 90 degrees in 20% bandwidth