###### Abstract  
In this study, we propose a miniaturized bandpass filter (BPF) developed by combining an approximate circular (36-gon) winding inductor, a circinate capacitor, and five air-bridge structures fabricated on a gallium arsenide (GaAs) substrate using an integrated passive device (IPD) technology. We introduced air-bridge structures into the outer metal wire to improve the capacitance per unit volume while utilizing a miniaturized chip with dimensions 1538 \(\upmu\)m \(\times\) 800 \(\upmu\)m (0.029 \(\uplambda\)\(\times\) 0.015 \(\uplambda\)) for the BPF. The pattern was designed and optimized by simulating different dimensional parameters, and the group delay and current density are presented. The equivalent circuit was modeled to analysis various parasitic effect. Additionally, we described the GaAs-based micro-nano scale fabrication process to elucidate the proposed IPD technology and the physical structure of the BPF. Measurements were conducted with a center frequency of 1.53 GHz (insertion loss of 0.53 dB) and a 3-dB fractional bandwidth (FBW) of 70.59%. The transmission zero was located at 4.16 GHz with restraint of 35.86 dB. Owing to the benefits from its miniaturized chip size and high performance, the proposed GaAs-based IPD BPF was verified as an excellent device for various S-band applications, such as satellite communication, keyless vehicle locks, wireless headphones, and radar. gallium arsenide; air-bridge structure; bandpass filter; capacitor; inductor; integrated passive device; micro-nano fabrication 202212347  
20220212020220220220220220220202202020220202202022020202202020220220202202022020220220220202202202202202202202202202202202202202202202202202202202202220220220220222022022202202220222022022202220220222022 have been widely studied to meet the growing market demand [4]. The LTCC technology embeds several passive components (such as resistors, capacitors, and inductors) in ceramics through punching, grouting, and printing, which reduces the size of the entire module. For example, see Ref. [5], where the insertion loss is 2.4 dB and the physical size is 6.9 \(\times\) 39.9 mm\({}^{2}\). Additionally, it allows ceramics to be sintered with highly conductive materials (silver, copper, and gold) that exhibit low resistance and low conductor loss at high frequencies. However, modules that require heat dissipation must have a heat sink, which complicates processing. Moreover, LTCC technology has higher requirements for the size and characteristics of the processed plates given that ceramics shrink after firing [6; 7]. HTSs have developed rapidly in recent years considering their low surface resistance, which is comparable to ordinary conductive metals. Additionally, passive components based on HTSs have almost no signal loss during transmission, which makes them attractive. Furthermore, their low-loss characteristics help fabricate relatively compact and complex designs of microwave passive components. For example, see Ref. [8], where the insertion loss is 0.2 dB and the physical size is 20.8 \(\times\) 16.15 mm\({}^{2}\)[9]. However, their low temperature requirements increase the cost and complexity, thereby limiting their development and popularity. MEMSs can largely integrate several passive components on a substrate, resulting in a microstructure of 20 \(\upmu\)m to 1 mm, which reduces the size and weight of the device. Furthermore, MEMSs are widely used considering they can be mass produced while reducing manufacturing costs. For example, see Ref. [10], where the insertion loss is 5.2 dB and the physical size is 5.2 \(\times\) 12.3 mm\({}^{2}\). However, the stability of their dynamic range and capability of power handling needs to be improved [11]. MMICs have gained wide attention due to advantages such as higher integration, smaller size, lighter weight, higher reliability of wire bonding, and lower cost of a single IC during mass production.