Generally, the communication system requires transmit-and-receive using one antenna. A duplexer is an important component in a wireless transceiver because it allows simultaneous transmission and reception of signals by means of a single antenna. With a single antenna, a duplexer is normally used for a microwave transceiver to isolate a transmitter from a receiver electrically. Therefore, a duplexer is generally composed of two individual band-pass filters with different center frequencies. Conventionally, the band-pass filter of a duplexer is a coaxial cavity filter with high quality factor.
Filter tuning in coaxial cavity filters can be realized by tuning screws. In this case, the tuning screws are adjusted from the lid towards the resonator inside the cavity. The goal of filter tuning is to find the optimum locations of tuning screws that satisfy the required filter response.
The optimization design of microwave filters may be achieved by using the optimization tools supported by CST Studio. These optimization tools change all the filter geometries to obtain the geometric parameters when the error function between the current frequency response and the desired frequency response is less than the threshold. However, use of these tools provides no guarantee that each step of optimization always goes in the right direction and optimization process is very time-consuming. Furthermore, the required frequency response may not be obtained accurately. Hence, recently, optimization routines using space mapping technique have been widely exploited.
Kim Myong Sik, a section head at the Faculty of Communications, has found a new optimization method to determine the location of tuning screws of the coaxial cavity filter for mobile base stations by using the space mapping technique, and verified the band-pass characteristics of the duplexer.
Unlike the optimization algorithms supported by CST Studio, the proposed method guarantees much faster optimization and can always produce the expected results.
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