To mitigate the overlapping of the radar and communication frequency bands caused by large-scale devices access, we propose a novel integrated sensing and communication (ISAC) system, where a micro base station (MiBS) simultaneously carries out both target sensing and cooperative communication. Concretely, the MiBS, acting as the sensing equipment, can also serve as a full-duplex decode-and-forward relay to assist end-to-end communication. Moreover, nonorthogonal downlink transmission (NO-DLT) is adopted between the macro base station and the Internet of Things devices, so that the spectrum utilization can be further improved. To facilitate the performance evaluation, both the exact and asymptotic outage probabilities, the ergodic rates associated communication, and the probability of successful sensing detection are characterized. Subsequently, a pair of problems of maximizing the receive signal-to-interference-plus-noise ratio of the sensing signal and maximizing the sum rate of communication are formulated that are solved by the classic Lagrangian method while exploiting the associated function monotonicity. Our simulation results demonstrate that: 1) The proposed ISAC NO-DLT system improves both the communication and sensing performance under the same power consumption as noncooperative NO-DLT and 2) the proposed power allocation (PA) schemes are superior to the random PA scheme.

A novel block-oriented time-delay neural network (BOTDNN) model for dynamic nonlinear modeling and digital predistortion (DPD) of RF power amplifiers (PAs) is proposed. The proposed model consists of a dynamic linear network and a static nonlinear network to characterize dynamic nonlinear systems. The dynamic linear network simulates multiple linear filters using a fully connected layer with the linear activation function. The static nonlinear network is constructed based on vector decomposition and phase recovery mechanism. To validate the proposed model, experiments have been carried out with two different PAs operating at 2.4 and 39 GHz, respectively. The test results demonstrate that the proposed model has better PA modeling and nonlinear compensation capabilities than state-of-the-art PA behavioral models, while with significantly lower model complexity. Furthermore, to reduce the system cost, we investigate the problems that arise when the neural network-based behavioral models are applied to low feedback sampling rate DPD and propose an improved method. The experiments confirm that the proposed low feedback sampling rate DPD method can effectively alleviate the deterioration of linearization performance caused by undersampling.

TeraHertz (THz) communications are envisioned as a promising technology, owing to its unprecedented multi-GHz bandwidth. One fundamental challenge when moving to new spectrum is to understand the science of radio propagation and develop an accurate channel model. In this paper, a wideband channel measurement campaign between 130 GHz and 143 GHz is conducted in an office room. The channel measurement campaign in the office room scenario consists of three cases: 1) LoS case in the office area 2) Line-of-Sight (LoS) case in the hallway and 3) NLoS case. Directional antennas are utilized and rotated for resolving the multi-path components (MPCs) in the angular domain. With careful system calibration that eliminates system errors and antenna effects, realistic power delay angular profiles (PDAP) are developed. In light of the measurement results, channel parameters and insights in the THz indoor channel are comprehensively analyzed, including the path loss, delay spread, angular, and correlations among the channel parameters. Furthermore, the propagation of NLoS multipath components (MPCs) in the office room scenario and its impact on the THz channel are discussed and compared with the channel measurement in the meeting at 140 GHz. Our analysis shows that the MPCs that reflect from the partitions dominate in NLoS propagation in office room.

The knowledge of reflection and transmission properties of building materials is crucial for understanding radio propagation and developing efficient channel models in terahertz (THz) indoor wireless communication. In this letter, such fundamental interaction mechanisms for five common building materials at 219-224 GHz are extensively investigated through experimental measurement campaign, including glass, granite, polyvinyl chloride board, ceramic, and wooden board. Measured results indicate that the reflection coefficients gradually decrease with the increasing of incident angle, whereas the transmission coefficients show weaker angle dependence. In particular, we compare the measured results with those at 40-50 GHz and investigate different characteristics of the materials at the two frequency ranges. Furthermore, the complex permittivity is extracted using least squares fitting methods based on measured reflection coefficients. The results presented in this letter can offer guidance to channel modeling at 220 GHz for indoor low-THz communication.

This article presents a novel 200-GHz four-element phased-array receiver system-in-package (SiP) using high-temperature co-fired ceramic (HTCC) technology for wireless communications. The receiver employs a local oscillator (LO) phase-shifting architecture to realize sub-terahertz (THz) beamforming. All components of the front-end array are heterogeneously integrated within the HTCC. To achieve low-loss interconnection and 3-D integration, quartz substrates and vertical air-filled waveguides are incorporated within the HTCC. Meanwhile, an electromagnetic bandgap (EBG) structure is introduced in the vertical transitions to mitigate energy leakage caused by assembly gaps, thus reducing the sensitivity to assembly errors. Besides, a highly efficient parabolic reflector antenna array with a multilayered structure is designed for beam scanning. The overall size of the front-end package is 40.7 $\times$ 43 $\times$ 7.3 mm $^{3}$ . The measured channel gain is 8.2–23 dB from 194.5 to 234.5 GHz (18.6% bandwidth), and the measured lower-sideband noise figure is 7.5–9.4 dB, covering from 196 to 215 GHz. The phased-array receiver can achieve a scanning range of $\pm$ 30 $^{\circ}$ in the E -plane. To evaluate its over-the-air (OTA) performance, a wireless link is demonstrated with 16-quadrature amplitude modulation (QAM) and 64-QAM waveforms, achieving a maximum data rate of 32 Gbps.

A high-integration and low-cost transmitter packaging solution for 0.2-THz system-in-package (SiP) application is newly presented using high-temperature co-fired ceramic (HTCC) technology. To improve 3-D integration, internal vertical air-filled interconnection waveguides buried in the HTCC package are explored and fabricated. A compact MoCu waveguide bandpass filter (BPF) is designed and integrated into the package to suppress the harmonic output of the mixer. To demonstrate the potential SiP application in the future 0.2-THz radar systems, based on the proposed solution, two 0.2-THz transmitters using frequency multipliers/mixer are designed, fabricated, and measured. All the components are buried in HTCC, and the overall size is $36\times 14\times9.8$ mm ³ and $54\times 14.5\times9.8$ mm ³ , respectively. Both the transmitters show good performance, and the measured output power is better than 8 and 5 dBm, respectively.