Yang Gao

Bio: Yang Gao is an academic researcher from Zhengzhou University. The author has contributed to research in topics: Microstrip & Amplifier. The author has an hindex of 4, co-authored 19 publications receiving 50 citations. Previous affiliations of Yang Gao include University of Birmingham.

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.

3D printed waveguide step-twist with bandpass filtering functionality

Abstract: A novel waveguide step-twist integrated with a bandpass filter is presented in this Letter. The twist is composed of four equally rotated cavities to achieve polarisation rotation and filtering functionalities simultaneously. Such step-twist can achieve a significant reduction in size and weight. The design is demonstrated at Ka-band using waveguide technology and is fabricated using a stereolithography apparatus 3D printing together with metal plating. The device is designed to have a centre frequency of 32 GHz and a bandwidth of 1 GHz. The measured result shows good agreement with simulations, with a measured average insertion loss of 0.84 dB and a return loss better than 15 dB across the passband.

Coupling Matrix-Based Design of Waveguide Filter Amplifiers

Abstract: This paper extends the conventional coupling matrix theory for passive filters to the design of “filter-amplifiers,” which have both filtering and amplification functionality. For this approach, extra elements are added to the standard coupling matrix to represent the transistor. Based on the specification of the filter and small-signal parameters of the transistor, the active $N + 3$ coupling matrix for the “filter-amplifier” can be synthesized. Adopting the active coupling matrix, the last resonator of the filter (adjacent to the transistor) and the coupling between them are modified mathematically to provide a Chebyshev response with amplification. Although the transistor has a complex impedance, it can be matched to the filter input by the choice of the coupling structure and the resonator frequency. This is particularly useful as the filter resonators can be of a different construction (e.g., waveguide) to the amplifier (e.g., microstrip). Here, an X-band filter-amplifier is implemented as an example, but the technique is general.

A 3-D Printed Bandpass Filter Using TM₂₁₁-Mode Slotted Spherical Resonators With Enhanced Spurious Suppression

Abstract: This article presents a Ka -band fourth-order slotted spherical resonator waveguide bandpass filter (BPF) with a wide spurious suppression stopband. It uses the first higher-order TM211 mode rather than the fundamental TM101 mode of the spherical resonator in order to obtain a higher unload quality factor ( $Q_{\mathrm {u}}$ ) for smaller in-band insertion loss, as well as a larger filter volume that gives better tolerance to fabrication errors in high frequency applications. By introducing slots that interrupt surface currents, the fundamental TM101 and two higher spurious modes (TE101 and TM311) can be suppressed without compromising the unloaded quality factor of the TM211 mode. In addition, the filter topology is optimized to further enhance the suppression level of the spurious passbands. A Z-shaped topology has been found effective in decreasing the coupling strength of the spurious TM311 mode. An analysis is performed to demonstrate the better tolerance of the Z-shaped filter over the conventional TM101-mode spherical resonator filter. For verification, a fourth-order slotted spherical resonator waveguide BPF with a center frequency of 31 GHz and bandwidth of 880 MHz is designed and manufactured using a selective laser melting (SLM) 3-D printing process. The measured results show an average in-band insertion loss of 1.53 dB, and a passband return loss better than 13.6 dB. The stopband of the filter is extended up to 40.9 GHz with a rejection level greater than 20 dB.

Integrated Waveguide Filter Amplifier Using the Coupling Matrix Technique

Abstract: This letter presents an integrated waveguide filter amplifier using all resonator-based filtering and matching structure. An $N\,+\,4$ active coupling matrix is proposed for the first time to describe the coupling topology. High- $Q$ waveguide resonators are featured in the design, achieving simultaneous filtering and matching at both the input and output ports. Easy integration of the transistor with waveguide resonators is demonstrated through filter synthesis, where a hybrid waveguide/ microstrip structure is implemented for the structural and impedance transition. In this letter, an X-band device is constructed as a demonstrator, but the technique is also applicable to higher frequencies where waveguide is widely utilized for its low loss.

Yield-Constrained Optimization Design Using Polynomial Chaos for Microwave Filters

Abstract: Yield optimization aims at finding microwave filter designs with high yield under fabrication tolerance The electromagnetic (EM) simulation-based yield optimization methods are computationally expensive because a large number of EM simulations is required Moreover, the microwave filter design usually requires several performance objectives to be met, which is not considered by the current yield optimization methods for microwave filters In this paper, an efficient yield-constrained optimization using polynomial chaos surrogates (YCOPCS) is employed for microwave filters considering multiple objectives In the YCOPCS method, the low-cost and high-accuracy of polynomial chaos is used as a surrogate An efficient yield-constrained design framework is implemented to obtain the optimal design solution Two numerical examples demonstrate the performance of the YCOPCS method, including a coupling matrix model of a fourth-order filter with cascaded quadruplet topology and an EM simulation model of a microwave waveguide bandpass filter The numerical results show that the YCOPCS method can obtain the filter designs with higher yield and reduce EM simulations by 80% compared to Monte Carlo-based yield optimization in all testing examples

Ka-Band Coplanar Magic-T Based on Gap Waveguide Technology

Abstract: A coplanar Magic-T is proposed based on a combination of ridge and E -plane groove gap waveguides for Ka-band applications. All four ports of the proposed Magic-T are coplanar. The impedance bandwidth of the proposed Magic-T is about 43% covering the whole Ka-band from 26 to 40 GHz. The Magic-T isolation is better than 40 dB in the whole bandwidth while its insertion loss is about 0.25 dB.

A 3-D Printed Bandpass Filter Using TM₂₁₁-Mode Slotted Spherical Resonators With Enhanced Spurious Suppression

Abstract: This article presents a Ka -band fourth-order slotted spherical resonator waveguide bandpass filter (BPF) with a wide spurious suppression stopband. It uses the first higher-order TM211 mode rather than the fundamental TM101 mode of the spherical resonator in order to obtain a higher unload quality factor ( $Q_{\mathrm {u}}$ ) for smaller in-band insertion loss, as well as a larger filter volume that gives better tolerance to fabrication errors in high frequency applications. By introducing slots that interrupt surface currents, the fundamental TM101 and two higher spurious modes (TE101 and TM311) can be suppressed without compromising the unloaded quality factor of the TM211 mode. In addition, the filter topology is optimized to further enhance the suppression level of the spurious passbands. A Z-shaped topology has been found effective in decreasing the coupling strength of the spurious TM311 mode. An analysis is performed to demonstrate the better tolerance of the Z-shaped filter over the conventional TM101-mode spherical resonator filter. For verification, a fourth-order slotted spherical resonator waveguide BPF with a center frequency of 31 GHz and bandwidth of 880 MHz is designed and manufactured using a selective laser melting (SLM) 3-D printing process. The measured results show an average in-band insertion loss of 1.53 dB, and a passband return loss better than 13.6 dB. The stopband of the filter is extended up to 40.9 GHz with a rejection level greater than 20 dB.

3-D-Printed Dual-Mode Filter Using an Ellipsoidal Cavity With Asymmetric Responses

Abstract: A new structure based on an ellipsoidal cavity that operates with the fundamental mode and its degenerate in a transverse routing scheme is presented in this letter. This configuration yields asymmetric filtering functions with two poles and one transmission zero, the position of which can be easily controlled by the rotation of the input and output. For validation purposes, a two-pole filter has been designed and manufactured using 3-D printing techniques. Measured results demonstrate the feasibility of the proposed filter with good agreement between simulation and measurement.

A K -Band High Interference-Rejection GaAs Low-Noise Amplifier Using Multizero Control Method for Satellite Communication

Abstract: This letter presents a 17.5–22.5-GHz low-noise amplifier (LNA) with the high out-of-band rejection in the range of 27.5–32.5 GHz and 4–10 GHz by using 90-nm GaAs p-HEMT technology. The multizero control method is proposed to produce multiple zeros for generating the high out-of-band rejection and expanding the rejection bandwidth. The multizero control is realized by bypass capacitor notch filters at the drain of transistors and shunt capacitor notch filters at the interstage matching circuits. By using this approach, the high rejection can be achieved at unwanted frequencies without additional devices. Also, the multizero control is mainly implemented in the transistor’s bypass branch, which can achieve the low noise figure (NF) well within the whole operating band. The cost and integration of the front end can also be improved. The measured maximum gain is 23.9 dB at 19 GHz, and the 3-dB bandwidth is 17.5–22.5 GHz. The good interference rejection of the proposed LNA is from 57 to 73 dB and 61 to 72 dB in the range of 4–10 GHz and 27.5–32.5 GHz, respectively. The measured NF is 1.1–1.3 dB. The LNA area is 2 mm $\times1.3$ mm including pads.