Abstract
Portable wireless communication systems are increasingly in demand in small sizes for human convenience. In wireless communication systems, the performance, size, and unit cost are very important. A band−pass filter is important to sharp cut–off frequency characteristics, size, and frequency selectivity in wireless communication systems. The band−pass filter has three types of techniques in the transmission−zero method, stub−loaded resonator, and stepped impedance resonator for the sharp cut−off frequency characteristic, adjustable bandwidth, and excellent frequency response characteristics. To obtain these characteristics, the impedance ratio and length of a stub are mainly adjusted. It also utilizes a multi–mode technique to increase bandwidth. However, it is analyzed that the problem of reducing the size of the device still remains. To solve these problems, the paper is applied to a stub−loaded resonator and a stepped impedance resonator to control the impedance ratio and the length of the stub to obtain the results of the transmission−zero method, bandwidth control, and size reduction through the folded structure. Dual−band bandwidth was secured by integrating a T−shaped band−stop filter. The designed band–pass filter has center frequencies of 243 GHz and 7.49 GHz, and the insertion loss of a proposed band−pass filter is 0.102 dB and 0.103 dB. Additionally, the return loss of a proposed band−pass filter is 19.13 dB and 19.96 dB, respectively. The bandwidth of a filter is 120% and 105%, respectively. The size of the filter is 0.0708 λg × 0.0533 λg. The designed filter has a good skirt phenomenon, small size, low insertion loss, and dual−band characteristics.
Highlights
The demand for wireless communication systems in the 4th industrial revolution technology is steadily increasing
For size reduction and bandwidth control, a bandpass filter (BPF) is used for the stepped impedance resonator (SIR), stub−loaded resonator (SLR), and multimode/band
We proposed a compact dual–band band–pass filter (BPF) with short stubs and a T–shaped band–stop filter (BSF)
Summary
The demand for wireless communication systems in the 4th industrial revolution technology is steadily increasing. An important item in a wireless communication system is that it divides frequency bands and avoids interference in different frequency bands [2] In this case, the bandpass filter (BPF) plays the role of frequency band distribution and interference blocking. The important components of a BPF are the low cost, bandwidth control, device size, skirt characteristic, frequency selectivity, and frequency response characteristics (low insertion loss and high return loss). A BPF using both SLR and SIR was able to obtain the tri−band characteristics of a wide bandwidth by adjusting the stub length and impedance ratio [10,11]. In order to obtain tri−band characteristics, it would have been difficult to adjust the length and impedance ratio of the filter at the same time. The filter has the disadvantages of a complex structure and a size increase [9]
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