5G Hairpin and Interdigital Bandpass Filters

Abstract

Filters play important role in many RF/Microwave applications in which they are used to get different responses (band-pass, band-stop, low-pass, and high-pass) [1]. Hairpin Bandpass Filter (HPBF) is simply constructed by folding the λ/2 resonators of the parallelcoupled filter, to get the U shape [2]. HPBF has been used in many applications for different frequencies. In [3], 5.78 GHz with 10% BW HPBF was designed to work for unlicensed WiMAX. Superior harmonics suppression in the response of HPBF is obtained in [4] by adding different Defected Microstrip Structure (DMS) to the filter's resonators. The resulted suppressions were 25 dB and 40 dB for the second and the third harmonics. Authors in[5], designed a compact HPBF for 923 MHz RFID application. The compactness was 37 % and it was achieved using via hole grounding. Plackett-Burman Design of Experiment methodology (DOE) was applied in designing 2.4 GHz HPBF for further optimization. The resulted insertion and return loss of this filter were 61% and 15 % improved from the one designed with Gensys software. 2 GHz-4 GHz HPBF was designed in [6] for satellite application. HPBF with Defected Ground Structure (DGS) for radar application was designed in [7]. In addition, this filter showed better performance with aluminum casing. In [8], X-band HPBF was designed for radar navigation. Authors in [9], designed a millimeter wave HPBF (30 GHz) on Liquid Crystal Polymer Substrate using Inkjet Printing Technology. The measured insertion and return loss at 30.4 GHz were 2.41 and 18.9 dB, respectively. Spurious harmonic response suppression was obtained by using nonuniform coupled line resonators to design 34 GHz in [10]. HPBF with tunable center frequency Abstract: At two low 5G frequency bands: 3.7 GHz-4.2 GHz and 5.975 GHz-7.125 GHz, Hairpin Bandpass Filter (HPBF) and Interdigital Bandpass Filter (IBF) are designed and simulated in this paper. Both filters show good results in terms of matching and transmission responses with a wide bandwidth through the two frequency bands. HPBF with simple design resulted in good return and insertion losses, <-10.43 dB and-0.63 dB, and <-14.48 dB and-0.46 dB through frequency bands: 3.51 GHz-4.27 GHz and 5.58 GHz-7.24 GHz, respectively. In addition to good filter response that IBF provides, it supports high order second harmonics suppression. The simulated S11 and S12 of this filter are <-11.15 dB and-0.63 dB with out of band rejection up to 11.12 GHz through the frequency band 3.56 GHz-4.25 GHz. Furthermore, at the second frequency band IBF is designed with two different grounding via hole radii (rVia), case 1: rVia = 0.4 mm and case 2: rVia = 0.7 mm. For both cases, the designed filter shows good results with high order second harmonics suppression up to 18.33 GHz and 18.96 GHz. In this paper, High Frequency Structure Simulator (HFSS) software is used to carry out the simulation.

Compact 5G Vivaldi Tapered Slot Filtering Antenna with Enhanced Bandwidth

“…Fig. 2f demonstrates that the W p = 1.2 mm used for UWB VTSA is better than that at W p = 1.819 mm (S 11 < -10 dB, BW = 6.4 -7.22 = 0.82 GHz and maximum realized gain of 6.17 dBi) utilized for UTL HPBF [27] and W p = 1.5095 mm (S 11 < -11.67 dB, BW = 6.1 -7.41 = 1.31 GHz and maximum realized gain of 6.38 dBi) in terms of matching, BW, and gain. At W p < 1.2 mm, there is a noticeable mismatch, such as at W p = 0.8905 mm (S 11 < -6.7 dB, BW = 5.976 -7.72 = 1.744 GHz and maximum realized gain of 6.79 dBi).…”

“…Fig. 2g shows that although the matching and gain at the optimized value, L tap = 2.9 mm (S 11 < -12.9 dB, BW = 6.04 -7.62 = 1.58 GHz and maximum realized gain of 6.53 dBi) for UTL HPBF [27] are 8.37% and 1.23% better than that at L tap = 2.8 mm (S 11 < -11.82, BW = 5.976 -7.656 = 1.68 GHz and maximum realized gain of 6.45 dBi), it is selected due its 5.95% wider BW which covers the lower frequency in required band (5.975 -7.125 GHz). As indicated in Fig.…”

“…To keep up with the recent development in the wireless communication system, the proposed VTSFAs are chosen to work in the 5G low-frequency band (5.975 -7.125 GHz). Based on the codesign approach, the designed 6.55 GHz UTL and NTL HPBFs in [27,28], respectively are integrated into the feed line of the recently designed compact UWB VTSA [29] resulting in 6.55 GHz VTSFA using 6.55 GHz UTL HPBF (Antenna 1) and NTL HPBF (Antenna 2).…”

“…By applying the NTL theory [28] to the designed 6.55 GHz UTL HPBF in [27], the UTL resonators are replaced by their equivalent NTL resonators with a 17.76% size reduction, guaranteeing that their ABCD parameters are equal. Fig.…”

“…In this work, the predesigned 6.55 GHz uniform and non-uniform transmission line (UTL) and (NTL) HPBFs in [27,28], respectively are integrated with the predesigned compact ultrawide band Vivaldi tapered slot antenna (UWB VTSA) in [29] to design compact 5G Vivaldi tapered slot filtering antennas (VTSFAs). This integration aims to suppress the unwanted signals and exploit the good performance of VTSA in terms of BW, gain, and stable directive radiation patterns.…”