Glass-Based Bandpass Filters for New Radio (NR) K-/Ka-Band Communications

Abstract

Highly miniaturized substrate integrated coaxial (SIC) bandpass filters (BPFs) are presented for new radio (NR) communications. They are based on glass-integrated two-post SIC resonators and mixed electromagnetic (EM) couplings that contribute to two poles and one transmission zero (TZ) to the overall BPF transfer function. The concept can be extended to high-order quasi-elliptic configurations shaped by 2N poles and N TZs by readily cascading N two-post SIC cavities through inter-stage transmission lines (TLs). A high-frequency glassbased integration platform is explored as a low-loss and high-frequency integration mechanism. To practically validate the concept, three glassintegrated BPF prototypes were designed, manufactured, and tested. They include a: 1) two-pole/one-TZ BPF with a passband centered at 26 GHz, fractional bandwidth (FBW) of 21%, and a TZ at 32 GHz; 2) twopole/one-TZ BPF with a passband centered at 26.7 GHz, FBW of 11%, and a TZ at 23.6 GHz; and 3) a four-pole/two-TZ BPF with a passband centered at 26.7 GHz, FBW of 11%, and two TZs at 24 and 31.3 GHz.

Design of a New Capacitive Load Cross-Coupled Cavity Filter

“…If the filter is to work safely, the maximum value of the field strength in the resonator must be less than the electric-field breakdown value of the air; otherwise, the filter will be broken down. When the two are equal in magnitude, the maximum value of the cavity power-capacity can be calculated using Equation (15). The breakdown field-strength of air at regular atmospheric pressure can be taken as Ep = 2.9 × 10 6 V/m, and the maximum energy storage of a single cavity calculated using CST Filter 3D software (CST Studio Suite 2022, Darmstadt, Germany) is 3.07173 × 10 −8 J:…”

“…In this context, cross-coupled structures capable of generating transmission zeros out-of-band in order to be able to improve frequency selectivity have been created [10][11][12] In addition, the filter size reduction is inevitably accompanied by a reduction of the cavity power capacity. Therefore, it is crucial to consider the power capacity [13][14][15].…”

RF Glass Technology Is Going Mainstream: Review and Future Applications

“…Recently, glass materials are also used as a dielectric load for resonators. These are realized in different technologies such as substrate integrated waveguide [122] at X-band and substrate integrated coaxial resonators [123] and K/K a -band, respectively. These structures make direct use of the dielectric properties of the glass substrate.…”

Multi‐band glass‐integrated bandpass filters for new radio (NR) communications

“…Although acoustic-wave filters such as the ones based on surface acoustic wave (SAW) resonators and bulk acoustic (BAW) resonators have been the major RF filtering technology for cellular communications, they are limited to narrow-band single-band transfer functions and frequencies <2 GHz. Integrated passive devices (IPDs) based filters using silicon [1][2][3], microwave monolithic integrated circuits (MMIC) [4], or low-temperature co-fired ceramic (LTCC) [5,6] and glass substrates [7][8][9][10][11][12] functionalize significantly wider BWs, and are suitable for higher frequencies; however, they exhibit lower quality-factor than the SAW/BAW filters and are significantly larger in size. Among the existing IPD technologies, glass-based IPDs exhibit competitive RF performance for both FR1 [7][8][9][10][11] and FR2 [12] applications.…”

“…Integrated passive devices (IPDs) based filters using silicon [1][2][3], microwave monolithic integrated circuits (MMIC) [4], or low-temperature co-fired ceramic (LTCC) [5,6] and glass substrates [7][8][9][10][11][12] functionalize significantly wider BWs, and are suitable for higher frequencies; however, they exhibit lower quality-factor than the SAW/BAW filters and are significantly larger in size. Among the existing IPD technologies, glass-based IPDs exhibit competitive RF performance for both FR1 [7][8][9][10][11] and FR2 [12] applications. Notable demonstrations of these trends include single-band quasi-elliptic bandpass filters (BPFs) for n77 and n79 bands [7,8] and inverter-less single and dual-band BPFs configurations in [10].…”