On‐chip miniaturized bandpass filter using gallium arsenide‐based integrated passive device technology

• Published in: Microwave and optical technology letters 2022-04, Vol.64 (4), p.688-693
• Main Authors: Wu, Wen‐Jing, Yuan, Bo, Zhao, Wen‐Sheng, Wang, Gaofeng
• Format: Article
• Language: English
• Subjects: Arsenic; bandpass filter; Bandpass filters; Cross coupling; electrical size; Frequencies; Gallium arsenide; Insertion loss; integrated passive device technology; Intermetallic compounds; Mathematical analysis; Parallel connected; rectangular coefficient; Rejection; Resonators; Selectivity; transmission zero
• ISSN: 0895-2477; 1098-2760
• DOI: 10.1002/mop.33180

The paper proposes a miniaturized bandpass filter (BPF) using gallium arsenide (GaAs)‐based integrated passive device (IPD) technology. The proposed filter is evolved from traditional third order BPF, and it achieves a wide operation frequency band covering three 5G sub‐bands including 3.4–3.5 GHz, 3.5–3.6 GHz, and 4.8–4.9 GHz. The performance of out‐of‐band rejection is improved by introducing three transmission zeros (TZs). As known, adding cross coupling and LC resonator are the general methods to improve out‐of‐band rejection. Therefore, the first TZ at 5.85 GHz is obtained at the upper sideband by adding a capacitive coupling between the source port and resonator 2, which is a cross‐coupling mode. According to the coupling matrix, the value of the added capacitance can be calculated and optimized. Another TZ at 2.36 GHz is occurred at the left side of passband as a serial LC resonator is connected in parallel with filter near the input port. The third TZ at 7.74 GHz is generated at the upper sideband due to a serial LC resonator connected in parallel with the load terminal of the filter. The values of components in LC resonators can be calculated, too. Finally, the whole filter is optimized in full‐wave electromagnetic simulation software HFSS. The proposed filter is fabricated and measured, and the results show that it has a wide −10 dB frequency band from 3.3 GHz to 4.9 GHz and a maximum insertion loss of 2.5 dB. In addition, it has a good frequency selectivity with a rectangular coefficient of 1.67 and out‐of‐band suppression higher than 20 dB in a wide stopband. The filter adopts compact placement and has a relative miniaturized electrical size of 0.298 λ02, which is about 55% smaller than recently reported one.