Modern communication systems require high-performance microwave devices that are compact, low-cost, multifunctional, and compatible with high-frequencies. The filters are one of the key components in these systems, and they need to have high performance and be tailored to the specific needs of each system [1]. However, conventional microstrip filters have limited performance and tuning range at higher frequencies. To overcome these limitations, substrate integrated waveguide (SIW) technology has emerged as a promising alternative for designing microwave filters [2]. SIW technology is based on creating a synthetic rectangular waveguide within a dielectric substrate by using metallized vias to connect the upper and lower metal plates [3]. SIW technology offers several advantages over microstrip technology, such as high-quality factor, low radiation loss, easy integration, high power handling, and mass production capability. SIW technology also enables the implementation of various microwave components, such as couplers [4, 5], diplexers [6, 7], antennas [8, 9], and filters [10, 11]. Therefore, SIW technology has attracted significant attention from both academia and industry in recent years.
Another technique that has been widely used to improve the performance of microwave devices is Defected Ground Structure (DGS) technology [12]. DGS technology involves etching various shapes of slots or defects on the ground plane of a microstrip circuit, which modifies its frequency response and creates band-stop characteristics [13]. One of the common shapes used in DGS is the Hilbert curve, which is a fractal curve that fills the space efficiently [14]. Using a Hilbert curve as a resonator allows us to obtain diverse responses by adjusting the line to-spacing ratio and the curve orientation. Moreover, the Hilbert curve offers several benefits as a resonator, such as high selectivity, wide band, sharp rejection, and easy tuning. The Hilbert curve was first applied to antenna geometry and then extended to other components, such as filters, couplers, and diplexers [15, 16]. Many papers have reported the combination of SIW and DGS (Hilbert curve) to enhance the performance of components [17, 18]. However, SIW and DGS still have some drawbacks, such as large size and high complexity. To address these issues, a novel structure called half-mode substrate integrated waveguide (HMSIW) has been proposed. HMSIW is derived from SIW by cutting it along its plane of symmetry corresponding to the magnetic wall of the fundamental mode. This reduces the size of the SIW by half while maintaining its propagation characteristics. HMSIW also has lower loss and higher quality factor than microstrip filters [19, 20]. HMSIW can be easily fabricated and can be integrated with other components on the same substrate. Therefore, HMSIW is a suitable candidate for designing compact and efficient microwave filters for modern wireless communication systems. In this paper we proposed a high performance filter design first we have simulated and analysed the HMSIW high pass filter, pass bas filter and band pass filter in the second part we have simulated and analysed the transverse DGS effects. In third part, we have discussed the fabrication and measurement results.