A three-dimensional (3D) integrated waveguide filtering power amplifier (PA) is introduced in this paper. An augmented${N} +4$coupling matrix that incorporates the harmonic control (HC) network and the transistor is synthesized to characterize the filtering PA circuits. Due to the introduced HC node, the characteristic polynomials and coupling matrix are resynthesized. By leveraging the coupling matrix, the PA circuits can achieve a standard Chebyshev filtering response at the fundamental frequencies while simultaneously introducing arbitrary transmission zeros (TZs) at harmonic frequencies with precisely controlled phase. This technique greatly expands the flexibility and practicality of waveguide PAs, particularly because harmonic manipulation plays a crucial role in determining efficiency and saturated power. The performances of return loss and gain can be predicted by the coupling matrix. Furthermore, this technique facilitates seamless integration between on-chip transistors and 3D high-Q resonators, as well as HC circuits. Consequently, the need for additional planar matching circuits is eliminated, resulting reduced losses, improved efficiency, and a more compact system architecture. The technique is validated by using the 0.25-$\mu $m GaN HEMTs microwave integrated circuits (MICs) at 3.3–3.5 GHz. The measured drain efficiency is from 62.8% to 67.7% at the saturated power of 38.8–39.1 dBm, and the adjacent channel leakage power ratios (ACLR) are −34.8/−33.5 dBc. The synthesis approach could boost progress of the PAs in high-frequency and high-power scenarios, where 3D waveguide circuit is preferred for its intrinsic low-loss and high-power capacity.

Low earth orbit (LEO) satellite communication system is vital due to its global coverage and low latency. To meet higher data rates, orthogonal frequency division multiplexing (OFDM) technology is recommended for adoption. In this paper, we analyze the nonlinear behavior of high-power amplifier (HPA) at Ka and Q/V frequency bands in wideband OFDM-based satellite communication system. A real satellite PA testing platform is constructed. Experimental results reveal that in wideband OFDM-based systems with high peak-to-average power ratio (PAPR), the conventional power back-off (PBO) method is no longer effective, particularly in mitigating in-band imbalance. Furthermore, we propose a low-complexity digital predistortion (DPD) scheme for satellite communication system. Experimental results demonstrate the robust performance of the proposed DPD.

To meet the demand for high-speed and high-quality communication in next 6G satellite communication, it is very necessary and urgent to study the behavioral modeling of 6G satellite communication power amplifiers (PAs). In satellite communication, PAs face the situation of high dynamic and wide bandwidth and exhibit strong nonlinearity and strong memory effects. In this case, we need to study Transformer architectures that can better handle long sequence data and further explore the inherent characteristics of the PA signal data. In this article, we propose a behavioral modeling method of PAs named augmented real-valued time-delay transformer (ARVTDform). ARVTDform is an augmented transformer-based method, which can capture long-range dependencies between the PA signal data and has powerful nonlinear modeling capabilities. To simulate the working status of the satellite PAs, we set up two physical platforms and collect and analyze twelve datasets. To the best of our knowledge, this is the first time real satellite data has been used for behavioral modeling. Extensive experiments on the collected datasets further demonstrate that our transformer-based method is more suitable for handing PAs with strong nonlinearity and strong memory effects in terms of normalized mean square error (NMSE). Finally, we discuss the major challenge and list the potential future work that may contribute to the sustained development of high-performance transceivers.

The task of chest X-ray report generation, which aims to simulate the diagnosis process of doctors, has received widespread attention. Compared with the image caption task, chest X-ray report generation is more challenging since it needs to generate a longer and more accurate description of each diagnostic part in chest X-ray images. Most of existing works focus on how to extract better visual features or more accurate text expression based on existing reports. However, they ignore the interactions between visual and text modalities and are thus obviously not in line with human thinking. A small part of works explore the interactions of visual and text modalities, but data-driven learning of cross-modal information mapping can not break the semantic gap between different modalities. In this work, we propose a novel approach called Knowledge-guided Cross-modal Alignment and Progressive fusion (KCAP), which takes the knowledge words from a created medical knowledge dictionary as the bridge to guide the cross-modal feature alignment and fusion, for accurate chest X-ray report generation. In particular, we create the medical knowledge dictionary by extracting medical phrases from the training set and then selecting some phrases with substantive meanings as knowledge words based on their frequency of occurrence. Based on the knowledge words from the medical knowledge dictionary, the visual and text modalities are interacted by a mapping layer for the enhancement of the features of two modalities, and then the alignment fusion module is introduced to mitigate the semantic gap between visual and text modalities. To retain the important details of the original information, we design a progressive fusion scheme to integrate the advantages of both salient fused and original features to generate better medical reports. The experimental results on IU-Xray and MIMIC datasets demonstrate the effectiveness of the proposed KCAP.

This paper introduces a coupling matrix synthesized filtering power amplifier (PA). In conventional filtering PAs, impedance matching is usually implemented through lumped or distributed circuits based approaches, such as the even-odd mode analysis or the equivalent circuit transformation. However, they are difficult to be applied in three-dimensional (3D) circuits, where exist electric/magnetic resonances and mutual couplings. Herein, a general$N+3$coupling matrix is synthesized, which the 3D physical structure can be determined directly, regardless of specific lumped/distributed circuit values. The$N+3$matrix enables explicit efficiency calculation of the amplifiers as well as scattering parameters, which offers a comprehensive evaluation and prediction of the circuits’ performances. Moreover, the coupling matrix facilitates easy integration of the on-chip transistor with the 3D high-Q resonators. Thus, conventional planar matching circuits can be removed, allowing for reduced losses and compact architecture. The technique will be more valuable for millimeter or terahertz waves as the operating frequencies, and therefore, planar circuit losses increase.