A pattern synthesis method capable of controlling beam directions and polarization states, as well as suppressing the cross-polarization level (XPL), is proposed for spaceborne antenna arrays in the satellite Internet of Things (SIoT). The optimal excitation distribution (OED) is calculated by maximizing an electric field energy ratio (EER), which is defined as the ratio of the weighted co-polarized (CoP) electric field energy density in the desired directions to the sum of the cross-polarization (XP) electric field energy density within the half-power beamwidth (HPBW) regions and the total electric field energy density within the sidelobe region (SLR). Notably, polarization constraints and XP component weights are introduced to control the beam polarization states and the XPLs within the HPBW regions. To validate the proposed method, a dual-polarized 2× 2 antenna array was designed and fabricated. Single- and dual-beam patterns with controlled beam polarization states and suppressed XPL within the HPBW regions were synthesized. Both the simulated and measured results agree well with the theoretical predictions, indicating that the proposed pattern synthesis method is a promising candidate for spaceborne antenna arrays in SIoT applications.
A novel constellation design, Fixed Lattice Shifted Triangular Quadrature Amplitude Modulation (FLS-TQAM) is proposed, to improve the energy efficiency of digital communication systems while maintaining a simplified geometric decision-region structure. Although, regular-TQAM provides superior packing efficiency as compared to the conventional square-QAM (SQAM), its irregular decision boundaries complicate practical implementation and analytical evaluation. The proposed FLS-TQAM uses a fixed lattice-shifting strategy that produces simplified decision regions thus reducing the structural complexity to evaluate the theoretical model. Based on the geometric characteristics of the resulting constellation, a generalized symbol error probability (SEP) formulation is derived for arbitrary odd as well as even bit modulation orders of FLS-TQAM over additive white Gaussian noise (AWGN) channel. In order to further highlight the utility of the proposed work, the error performance analysis of FLS-TQAM over AWGN channel is extended to the Extreme Two-Wave fading distribution which is specifically modeled to cover severe fading conditions. Simulation and analytical results show that the proposed method is not only mathematically accurate but also performs better than the traditional models, proving that FLS-TQAM is a practical and highly efficient solution for the next generation of wireless devices.
Noise-domain non-orthogonal multiple access (ND-NOMA) provides low-complexity multiuser transmission by embedding independent data streams in statistical properties of a common random waveform. Existing designs, however, mainly consider a single hop, binary statistical alphabets, and a fixed access point. This paper develops a relay-orchestrated dual-hop downlink system in which a base station serves two low-complexity Internet-of-Things users through one of several half-duplex amplify-and-forward relays. One user’s bits are conveyed by the mean of a Gaussian waveform, while the other user’s data are mapped to two consecutive silent, low-variance, or high-variance states. The relay preserves this statistical superposition without decoding. Exact finite-sample laws are established for the sample mean and centered sample variance after relay-noise amplification, and a constrained maximum-likelihood detector is derived for the eight valid ternary pairs. A relay-selection rule based on the weakest Bhattacharyya separation among the user statistics is then proposed and embedded in an energy-latency-reliability design framework. Simulations verify the exact analysis and show that the proposed selection reduces weighted bit error rate relative to first-hop-only selection. The results also quantify the fundamental tradeoffs among observation length, successful-delivery energy, variance calibration, and inter-user power allocation.
This paper introduces a highly compact, wideband frequency doubler operating in the D-band, designed in 40-nm CMOS for high-resolution FMCW radar and emerging joint radar-communication architectures. The circuit utilizes a traveling-wave (distributed) topology integrated with an on-chip Marchand balun to achieve seamless differential signal generation. To optimize second-harmonic conversion efficiency while maintaining low power overhead and occupied silicon area, the multiplier core features three push–push core stages. Alongside the optimization of the core stage count and the Marchand balun development, the design of an integrated D-band amplifier for overall system implementation is presented. Post-layout simulation results demonstrate an output frequency coverage of 106 to 127 GHz. Driven by a 10-dBm input signal, the system yields a conversion gain of -7 dB while dissipating a modest 47.1 mW of power. The complete circuit requires a compact core layout area of 0.131 mm2.
An advanced technique for suppressing cross-polarized (XP) radiation in a strip-fed cylindrical dielectric resonator antenna (CDRA) is presented. The source of XP radiation is identified and suppressed to improve cross-polarization characteristics over the operating bandwidth. With a compact footprint of 0.5λ × 0.5λ, the optimized antenna resonates near 2.5 GHz and achieves an impedance bandwidth of 7.5%, making it suitable for Wi-Fi applications. The resonant frequency can be smoothly tuned without significantly affecting the co-polarized (CoP) broadside pattern. Compared to a conventional reference antenna resonating at 2.5GHz, the proposed design achieves approximately 25 dB suppression of XP radiation in the H-plane over a 100° beam width. An analysis of cross-polarized isolation (XPI) over the operating frequency demonstrates an XPI ranging from 40 to 50 dB, ensuring the effectiveness of the proposed technique. The proposed approach offers a minimal structural perturbation to the CDRA, enabling easy fabrication using standard micromachining techniques.
