A Microwave Band Pass Filter with Suspended Diamond Slot Structure

Abstract

Abstract. In the present paper a band pass microwave filter based on spoof surface plasmon polaritions (spoof SPPs) mechanism and with suspended diamond slot structure is designed and simulated. The filter is composed of three sections, where in the third section, a corrugated metallic strip with parallel and periodically arranged diamond slots is the spoof SPPs transmission line. In the second section, the transition section, the gradient diamond slots are designed and distributed with the same periodic as the spoof SPPs section to realize the minimum transmission impedance. The transmission and reflection properties of the spoof SPPs filter in microwave frequency region are elaborately investigated. Through adjusting the geometrical dimensions of the suspended diamond-shaped slot structure, the bandwidth and suppression characteristics of the filter can be flexibly controlled and the filter has great resistant ability to space electromagnetic interference. I. IntroductionThe surface plasmon polaritons (SPPs) is a kind of surface electromagnetic wave. It propagates along the interface between the metal and the dielectric interface with an amplitude decaying exponentially in the direction vertical to the interface, since the metal has the similar property to plasma with a negative permittivity [1]. SPPs have been proposed to transform the traditional Sommerfeld or Zenneck surface waves into the highly confined electromagnetic waves, which provide favorable conditions to overcome the diffraction limit [2]. Therefore, SPPs have been researched in areas of super-resolution imaging [3], electromagnetically induced transparency (EIT) [4], energy harvesting [5] and SPP circuits [6]. However, natural SPPs effect can only work at optical frequency since the intrinsic electron oscillation in a metal is usually located beyond the infrared band. While at much lower frequency band, which is actually the microwave and terahertz communication frequency bands, deep sub-wavelength effect of SPPs cannot be realized because the metal behave assemble as perfectly electrical conductor (PECs), with large imaginary and negative real part of the permittivity, disabling the internal plasmonic oscillations in metal.With the development of SPP devices, in 2004, professor Pendry et al. put forward a device, which is the so-called spoof SPPs concept. The spoof SPPs device can produce deep sub-wavelength effect at microwave and terahertz frequencies, which can be employed to fabricate novel microwave compact devices [7]. The spoof SPPs microwave device, compared with traditional microwave devices, possesses special properties [8][9][10][11]. For example, it can confine the microwave field into sub-wavelength size, it possesses better resistibility to electromagnetic interference as well as possesses higher sensitivity and larger bandwidth. Therefore, the filters based on the spoof SPPs can be very suitable to meet the requirements of the next generation microwave communication [12][13].Based on the above technology background, in the presen...