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High-Rate Regular APSK Constellations
摘要： The majority of modern communication systems adopts quadrature amplitude modulation (QAM) constellations as transmission schemes. Due to their square structure, however, QAM do not provide satisfying protection to phase noise effects as the number of constellation points grows, increasing at the same time their peak to average power ratio (PAPR). This requires an expensive power amplifier and oscillator at the transmitter to guarantee low distortion, complicating the adoption of dense transmission schemes in practical high-data rate systems. In this paper, we construct a coded modulation scheme based on regular amplitude and phase shift keying (RAPSK) modulations. We propose a novel multilevel coding (MLC) labeling for the constellation points separating amplitude and phase domains. We provide a novel multistage decoding (MSD) scheme allowing for a low-complexity log-likelihood ratio (LLR) calculation for soft-input decoding of component codes, along with a suitable rate design. Finally, we compare the proposed scheme with state-of-the-art QAM constellations and optimized constellations in the presence of phase noise.
关键词： Digital modulation,microwave communication,phase noise
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Research of High Performance Frequency Synthesizer for X-Band LFMCW Radar Application
摘要： This paper describes a low phase noise and low spurious frequency synthesizer based on DDS (Direct Digital Synthesis)–PLL (Phase-Locked Loop)–MIX (Mixer) architecture. The architecture combines the advantages of both DDS and PLL, In order to achieve a good performance at phase noise and spurious, a mixer has been introduced. According to this structure, an excellent performance X-Band LFMCW (9.6GHz~9.9GHz) frequency synthesizer with low phase noise (>-115dBc/Hz@10KHz), low spurious in narrow band SFDR (>-90dBc), linearity 8.76E-5 is developed. Using this architecture, the phase noise of X band signal can be better than -125dBc/Hz@10KHz
关键词： Low phase noise,PLL,LFMCW,Low Spurious,DDS
更新于2025-09-04 15:30:14
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An upgraded interferometer-polarimeter system for broadband fluctuation measurements
摘要： Measuring high-frequency fluctuations (above tearing mode frequencies) is important for diagnosing instabilities and transport phenomena. The Madison Symmetric Torus interferometer-polarimeter system has been upgraded to utilize improved planar-diode mixer technology. The new mixers reduce phase noise and allow more sensitive measurements of fluctuations at high frequency. Typical polarimeter rms phase noise values of 0.05°–0.07° are obtained with 400 kHz bandwidth. The low phase noise enables the resolution of fluctuations up to 250 kHz for polarimetry and 600 kHz for interferometry. The importance of probe beam alignment for polarimetry is also verified; previously reported tolerances of ≤0.1 mm displacement for equilibrium and tearing mode measurements minimize contamination due to spatial misalignment to within acceptable levels for chords near the magnetic axis.
关键词： Faraday rotation,interferometer-polarimeter,planar-diode mixer,broadband fluctuation measurements,phase noise
更新于2025-09-04 15:30:14