Miniaturized IPD bandpass filter with controllable transmission zero based on modified lumped T‐section
■In this letter, a miniaturized bandpass filter (BPF) with controllable transmission zero (TZ) based on one lumped T‐section is proposed. To enhance rejection in the BPF, a modified T‐section circuit is introduced to generate a controllable TZ that can be readily adjusted by the LC values. To validate the performance, the proposed BPF is fabricated using integrated passive device technology on silicon. The measurement results show that the achievable bandwidth covers 2.4–2.5 GHz, with an insertion loss less than 2.6 dB and a measured return loss less than −15 dB. The fabricated BPF has a compact size of 1.3 mm × 0.8 mm (i.e., 0.0113λ₀ × 0.0069 λ₀). The simulated and measured results of the BPF are in reasonably good agreement.
●KEYWORDS
■band pass filter (BPF), integrated passive device (IPD), transmission zero
●INTRODUCTION
■A compact bandpass filter with high‐frequency selectivity and low insertion loss has the potential to significantly enhance the performance of wireless communication systems. Especially with the increasing miniaturization of communication terminals, on‐chip filter is an attractive choice to achieve high integration of the wireless system. Consequently, there has been extensive research on developing high‐performance and miniaturized filters in recent years.
■A novel synthesis method for lumped‐element bandpass filters is proposed in Chen et al.,and A design methodology for optimized minimum inductor bandpass filter (BPF) is presented in Taslimi and Mouthaan. In addition, a glass‐integrated passive device bandpass filter using synthesized stepped impedance resonators is presented in Tseng et al. However, all their proposed designs are mainly designed to verify their filter synthesis methods, so the filters performance such as the size and insertion loss cannot be effectively controlled. Filters designed with differential transformer structures can achieve very compact size, but its design structure is special and not universal. To improve the out‐of‐band rejection of the filter, adding transmission zero (TZs) to the filter is an effective method. 5–7 In Xu et al.,the paper utilizes the coupling matrices to design a compact low-temperature cofired ceramic (LTCC) bandpass filter which introduces TZs at both sides of the filter passband to enhance the selectivity. In Zhao et al., TZs are generated by stepped‐impedance stubs to obtain high selectivity. Because the above designs are fabricated on the LTCC technology, their size are also slightly larger. In addition to adding TZs to filter, increasing the filter order is also an effective way to improve the filter. In Lyu et al., the design employs a stepped impedance multi-mode resonator to design a high‐order on‐chip wideband bandpass filters and achieves the wide stopband and high stopband rejection. In Liu et al., a BPF based on three π‐type units has the advantage of the ultra‐wide stopband due to the nonperiodic phase of the unit. Although the above two designs have wider out‐of‐band rejection and their passband bandwidth is also wider, there are still challenging to implement them into Wi‐Fi, Bluetooth, or 5G applications. Another way to improve out‐of‐band rejection is to add an additional filter circuit.In Marin et al.,a TZ is introduced to improve out‐of‐band rejection by adding low‐pass pi‐type circuits to the input and output ports of the filter. However, since the design uses a PCB structure rather than an on‐chip design. In the design of on‐chip filters,a Pi‐section circuit is designed so that a TZ is obtained at the upper sidebands, which effectively improving the high‐frequency out‐of‐ band rejection performance of the filter.
■In this letter, a miniaturized silicon‐based IPD BPF is presented. To improve out‐band rejection, a TZ is produced at lower sidebands. A modified T‐section circuit is introduced and analyzed to generate and control this TZ. It can be readily adjusted by LC value in the T‐section. Finally, the simulation results from the electromagnetic (EM) simulator and the measured results are shown and compared. The proposed BPF demonstrates competitive overall performance when compared to recently reported works, such as those in Chen and Colleagues.
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English Chinese Chinese and English Japanese |
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23 March 2024 |
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773 KB |
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