Cheng Guo

Bio: Cheng Guo is an academic researcher from Xi'an Jiaotong University. The author has contributed to research in topics: Band-pass filter & Resonator. The author has an hindex of 11, co-authored 54 publications receiving 466 citations. Previous affiliations of Cheng Guo include Chinese Ministry of Education & University of Birmingham.

$W$ -Band Waveguide Filters Fabricated by Laser Micromachining and 3-D Printing

Abstract: This paper presents two W-band waveguide bandpass filters, one fabricated using laser micromachining and the other 3-D printing. Both filters are based on coupled resonators and are designed to have a Chebyshev response. The first filter is for laser micromachining and it is designed to have a compact structure allowing the whole filter to be made from a single metal workpiece. This eliminates the need to split the filter into several layers and therefore yields an enhanced performance in terms of low insertion loss and good durability. The second filter is produced from polymer resin using a stereolithography 3-D printing technique and the whole filter is plated with copper. To facilitate the plating process, the waveguide filter consists of slots on both the broadside and narrow side walls. Such slots also reduce the weight of the filter while still retaining the filter’s performance in terms of insertion loss. Both filters are fabricated and tested and have good agreement between measurements and simulations.

A 3-D Printed Lightweight X-Band Waveguide Filter Based on Spherical Resonators

Abstract: A fifth order X-band waveguide bandpass filter, based on spherical resonators, has been designed, and fabricated by 3-D printing. In comparison with rectangular waveguide, spherical resonators have a higher unloaded quality factor, but at the same time suffer from closer higher order modes. In this letter, a special topology has been proposed to relieve the impact of the first three higher order modes in the resonator and ultimately to achieve a good out-of-band rejection. Stereolithography based 3-D printing is used to build the filter structure from polymer and a 25 $\mu{\rm m}$ thick copper layer is deposited to the filter. The measurement result of the filter has an excellent agreement with the simulations. The filter is also considerably lighter than a similar metal filter.

A Lightweight 3-D Printed $X$ -Band Bandpass Filter Based on Spherical Dual-Mode Resonators

Abstract: A 3-D printed fourth-order cavity bandpass filter (BPF) centered at 10 GHz and with a 3% fractional bandwidth is presented in this letter. The BPF was designed using two high- $Q$ spherical dual-mode cavity resonators, and was fabricated using a stereolithography-based 3-D printing technique. Compared to dual-mode filters constructed by square or cylindrical resonators, the use of spherical resonator gives a wider spurious-free region. In order to fully exhibit the light weight advantage of additive manufacturing, the redundant material outside of the filter was removed. In addition, rectangular apertures were added through the cavities and waveguide walls without interrupting the surface current distributions, which further yields reduced filter weight as well as easier electroplating. Measured results of the BPF exhibit an excellent agreement with simulations.

A 3-D Printed $E$ -Plane Waveguide Magic-T Using Air-Filled Coax-to-Waveguide Transitions

Abstract: This article reports on a new class of broadband and fully 3-D printed $E$ -plane coax-to-waveguide transition and a monolithically 3-D printed waveguide magic-T based on the transition. The transition is constructed by a section of air-filled rectangular coaxial transmission line (TL) that is placed between two broadband coax-to-waveguide probe transitions. It is used to interconnect the magic-T’s sum port and the waveguide T-junction. The incorporation of the transition reorients all the waveguide arms of the magic-T into the $E$ -plane. Some $X$ -band prototypes of the proposed transition and the magic-T are designed and implemented. Polymer-based additive manufacturing and copper electroplating techniques are employed to monolithically fabricate each prototype. The transition and the magic-T exhibit broadband and low-loss characteristics from 8.2 to 12.4 GHz with the measured performance well matched with the simulations. In addition, the power handling capability (PHC), including the peak PHC (PPHC) and the average PHC (APHC), of the magic-T is evaluated by simulations, showing that the proposed magic-T could handle 100 W of APHC.

Monolithically 3-D Printed Hemispherical Resonator Waveguide Filters With Improved Out-of-Band Rejections

Abstract: This paper provides a comprehensive presentation for the RF design and implementation of novel millimeter-wave waveguide bandpass filters (BPFs) that are composed of compact hemispherical resonators. The proposed hemispherical resonator features a high unload quality factor and a volume 50% smaller than a spherical one and more significantly is much less degenerate than the latter due to its structural asymmetry. With proper geometrical configurations, the hemispherical resonator BPF can perform significantly improved out-of-band rejections compared with the spherical resonator BPFs of the same orders. The second- and fourth-order waveguide-fed BPFs are designed at $X$ and $Ka$ band s with flexible inter-resonator coupling geometries. The proof-of-concept $Ka$ -band filters are monolithically prototyped with a high-temperature-resistant ceramic-filled photosensitive resin by using a fast and low-cost stereolithography (SLA)-based additive manufacturing technique. A proprietary electroless nickel/copper/silver plating process is reported for surface metallization of the utilized commercially available resin. The $Ka$ -band filters demonstrate in the passbands small insertion losses (0.43–1 dB), good return losses (mostly >10–17 dB), and small frequency shifts (0.01%–0.47%), which validates excellent fabrication accuracy and reliability of the SLA printing and the metal plating. Characterization and quantification of surface morphology for SLA-printed samples are performed by employing contact profilometry and scanning electron microscopy.

Additive manufacturing of structural materials

Abstract: Additive manufacturing (AM), also known as three-dimensional (3D) printing, has boomed over the last 30 years, and its use has accelerated during the last 5 years AM is a materials-oriented manufacturing technology, and printing resolution versus printing scalability/speed trade-off exists among various types of materials, including polymers, metals, ceramics, glasses, and composite materials Four-dimensional (4D) printing, together with versatile transformation systems, drives researchers to achieve and utilize high dimensional AM Multiple perspectives of the AM of structural materials have been raised and illustrated in this review, including multi-material AM (MMa-AM), multi-modulus AM (MMo-AM), multi-scale AM (MSc-AM), multi-system AM (MSy-AM), multi-dimensional AM (MD-AM), and multi-function AM (MF-AM) The rapid and tremendous development of AM materials and methods offers great potential for structural applications, such as in the aerospace field, the biomedical field, electronic devices, nuclear industry, flexible and wearable devices, soft sensors, actuators, and robotics, jewelry and art decorations, land transportation, underwater devices, and porous structures

A Lightweight 3-D Printed $X$ -Band Bandpass Filter Based on Spherical Dual-Mode Resonators

Abstract: A 3-D printed fourth-order cavity bandpass filter (BPF) centered at 10 GHz and with a 3% fractional bandwidth is presented in this letter. The BPF was designed using two high- $Q$ spherical dual-mode cavity resonators, and was fabricated using a stereolithography-based 3-D printing technique. Compared to dual-mode filters constructed by square or cylindrical resonators, the use of spherical resonator gives a wider spurious-free region. In order to fully exhibit the light weight advantage of additive manufacturing, the redundant material outside of the filter was removed. In addition, rectangular apertures were added through the cavities and waveguide walls without interrupting the surface current distributions, which further yields reduced filter weight as well as easier electroplating. Measured results of the BPF exhibit an excellent agreement with simulations.

Polymer-Based Additive Manufacturing of High-Performance Waveguide and Antenna Components

Abstract: In this paper, a lightweight horn antenna array demonstrator is designed and fabricated by means of an additive manufacturing (AM) process that has been optimized for complicated passive radio-frequency (RF) components. The presented design comprises a complex waveguide feeding network (WFN) which aims to exploit the increased flexibility offered by this novel fabrication technique. This WFN concept could be easily extended to larger antenna arrays with higher gain for full-size telecommunication applications. The electromagnetic performance of the featured structure is validated by means of full-wave numerical simulations. Fabricated prototypes of the WFN and of the complete antenna array are tested and are found to exhibit a promising agreement with the simulation results.

Development of 340-GHz Transceiver Front End Based on GaAs Monolithic Integration Technology for THz Active Imaging Array

Abstract: Frequency multipliers and mixers based on Schottky barrier diodes (SBDs) are widely used in terahertz (THz) imaging applications. However, they still face obstacles, such as poor performance consistency caused by discrete flip-chip diodes, as well as low efficiency and large receiving noise temperature. It is very hard to meet the requirement of multiple channels in THz imaging array. In order to solve this problem, 12-μm-thick gallium arsenide (GaAs) monolithic integrated technology was adopted. In the process, the diode chip shared the same GaAs substrate with the transmission line, and the diode’s pads were seamlessly connected to the transmission line without using silver glue. A three-dimensional (3D) electromagnetic (EM) model of the diode chip was established in Ansys High Frequency Structure Simulator (HFSS) to accurately characterize the parasitic parameters. Based on the model, by quantitatively analyzing the influence of the surface channel width and the diode anode junction area on the best efficiency, the final parameters and dimensions of the diode were further optimized and determined. Finally, three 0.34 THz triplers and subharmonic mixers (SHMs) were manufactured, assembled, and measured for demonstration, all of which comprised a waveguide housing, a GaAs circuit integrated with diodes, and other external connectors. Experimental results show that all the triplers and SHMs had great performance consistency. Typically, when the input power was 100 mW, the output power of the THz tripler was greater than 1 mW in the frequency range of 324 GHz to 352 GHz, and a peak efficiency of 6.8% was achieved at 338 GHz. The THz SHM exhibited quite a low double sideband (DSB) noise temperature of 900~1500 K and a DSB conversion loss of 6.9~9 dB over the frequency range of 325~352 GHz. It is indicated that the GaAs monolithic integrated process, diodes modeling, and circuits simulation method in this paper provide an effective way to design THz frequency multiplier and mixer circuits.