Design of a filter-antenna subsystem for UWB communications

In this paper, we discuss about the design of a filter-antenna subsystem for UWB communications, which can appears optimum physical and electrical characteristics. A UWB antenna can't obtain a good performance in the passband and restrain the upper-passband (higher than 10.6 GHz) very well at the same time by itself. So we propose a filter-antenna subsystem. In this subsystem, we associate a UWB filter with a UWB antenna. The UWB filter is placed where the microstrip feed line was located. By this way, several subsystems' advantages can be obtained. First of all, UWB filter can be used as a wideband match circuit to enhance the performance of antenna in the passband. Secondly, we can get an improved out-of-band performance. Thirdly, the subsystem has a small dimension, which is very essential to the modern radio communication system. In this subsystem, S
₁₁
is smaller than -10 dB between 3.3-10.4 GHz and higher than -3 dB until nearly 18 GHz. A quasi-omnidirectional radiation pattern can also be remained. The measured results are well matched to the simulations.