Quadrature Modulation Signals Research Articles

Justification of the Empirical Expression for Assessing the Noise Immunity of Quadrature Modulation Signals

An approach to the substantiation of the empirical formula for calculating the bit error probability of quadrature modulation signals in terms of the average signal energy and the minimum Euclidean distance is considered. An analytical description of quadrature synthesis signals in the time and frequency continuum is presented. An approach to assessing the noise immunity of quadrature modulation signals from the standpoint of the indicator of the average signal energy and the Euclidean distance is considered. The equivalence of various well-known approaches to the analytical calculation of the bit error probability is shown. Graphic materials are presented, as well as simulation results. Empirically substantiated is a universal expression for assessing the noise immunity of receiving quadrature modulation signals, based on the differences in the average energy value and the value of the minimum Euclidean distance. Its generality with known expressions is shown.

Theoretical Aspects in Forming Complex Structure Signal

Receiving and transmitting paths of modern radio communication systems are built on the basis of an open structure that provides hierarchical differentiation of access to the provided telecommunication services. However, this approach does not exclude the possibility of access to the transmitted content by unauthorized users. Hiding information by methods of cryptographic protection in such a situation only activates additional interest in transmission, therefore the most pragmatic solution is to use signals of a complex structure, which significantly complicate or even exclude the extraction of information from them by third-party users. The problem of regulating access selection in the development and design radio system elements is rather multifaceted and has a high degree of complexity. One of the directions for solving problems in this subject area is based on the well-known approaches to expanding the signal base, however, algorithms for their practical implementation were obtained without taking into account the limitations on the allocated resource and the very fact of using these algorithms. Based on the theory of systems and the general theory of communication, an approach to the formation of signal structures of a complex structure has been developed, which ensures an increase in the properties of their structural secrecy in relation to unauthorized users. At the same time, the known solutions at the physical level of signal spaces were refined, which made it possible to formalize the procedures for the formation of radio signals with specified properties. The method of formalizing the function of displaying the signal space based on the allocation of stochastic properties of pseudo-random sequences has been substantiated, which made it possible to ensure the uncertainty of their structure in case of unauthorized processing. The approbation of the proposed approach is given on the example of the formation of quadrature modulation signals, taking into account the subsequent analysis of their properties from various positions of legitimate and illegitimate users. The results obtained confirm the uncertainty during illegitimate processing with a slight deterioration in the noise immunity properties of radio communication systems. In general, this allows to conclude the adequacy of theoretical solutions. As an example, constellation diagrams of signals at the output of a quadrature receiver are presented. The set of proposed technical solutions presented in the work determines the novelty of this approach. The scientific problem to be solved belongs to the class of problems of synthesis of signals of complex structures.

An Optimized Design Method of PSWFs Pulse Group Based on DFT Precoding

Aiming at the problems of non-sinusoidal time-domain multiple quadrature modulation signals based on Prolate Spheroidal Wave Functions (PSWFs), as the number of pulses increases, the bandwidth efficiency of the modulation signal frequency band decreases, the Peak-to-Average Power Ratio (PAPR) and the implementation complexity are high, a method for optimal design of PSWFs pulse groups based on DFT precoding is proposed. The PSWFs pulse signal frequency domain generation method is adopted. By introducing the precoding matrix, the multi-channel PSWFs pulse group signals are optimized and designed, and then the input data is redistributed to obtain new PSWFs pulse group signals. Experimental results show that this method can further improve the power efficiency of the modulated signal and effectively reduce the peak-to-average power ratio of the modulated signal without changing the orthogonality of the original PSWFs subcarriers. As the number of carriers increases, the suppression effect on the peak-to-average power ratio becomes more obvious.

ПЕРСПЕКТИВИ, ПЕРЕВАГИ ТА ОСНОВНІ ПРИНЦИПИ ВОЛОКОННО-ЕФІРНИХ ТЕХНОЛОГІЙ ДЛЯ ТЕЛЕКОМУНІКАЦІЙНИХ СИСТЕМ В МІЛІМЕТРОВОМУ ДІАПАЗОНІ ХВИЛЬ

Волоконно-ефірні технології зможуть стати перспективним рішенням для реалізації телекомунікаційних бездротових систем в міліметровому діапазоні хвиль. Фотонні методи формування радіосигналів та волоконно-ефірна архітектура змужуть забезпечити високу пропускну спроможність мереж за рахунок широкої смуги обробки до 10 ГГц, спектрального мультиплексування та використання форматів модуляції високого порядку. У статті проаналізовані перспективи і переваги реалізації бездротових телекомунікаційних систем з використанням волоконно-ефірних технологій в міліметровому діапазоні хвиль. Показані основні принципи фотонних методів формування та модуляції радіосигналів міліметрового діапазону, архітектури гібридної волоконно-ефірної мережі. Проаналізовано складові шуму, дискретність модуляції амплітуди і фази для квадратурного модульованого радіосигналу з використанням фотонних методів понижуючого перетворення частоти.

Digital Signal Detection by a Glow Discharge Detector

A glow discharge detector (GDD) is a plasma neon bulb originally designed for lighting. However, it was demonstrated that it can be used for the detection of electromagnetic radiation in a wide range of frequencies up to millimeter and submillimeter waves. It is shown here that the device can be used not only as a detector but also as a heterodyning mixer. Experimental measurements confirm an analytical derivation, demonstrating that quadrature modulated signals can be downconverted to an intermediate frequency (IF) without distortions, even if the amplitude and phase are modulated simultaneously, as in quadrature amplitude modulation (QAM) waveforms. Digital QAM waves at the microwave frequencies were directly illuminated onto the GDD and mixed with radiation produced by a local oscillator. The resulted GDD current was analyzed to verify that the product maintains its QAM constellation also at the IF. The GDD detects both the magnitude as well as the phase in a manner that allows the complete demodulation of the digital data using several modulation methods. The experimental setup, as well as the results, is presented. It is concluded that the GDD can be employed also as a direct mixer in a digital receiver chain. The notation “GDM” is proposed for it which stands for “glow discharge mixer.”

Моделирование фазовых сдвигов света в порядках дифракционных решеток интерференционного датчика линейных перемещений

Phase shifts of light in the orders of diffraction gratings for the interference sensor of linear displacements are considered. The use of a phase diffraction grating with given geometrical parameters of the surface relief makes it possible to stabilize the phase relationships in the optical signals and, as a result, in the final signals taken from the displacement sensor. Based on mathematical modeling data, technically feasible parameters of the surface relief of diffraction gratings are proposed to create the required phase shifts between the diffracted beams and quadrature modulation signals and to achieve the required measurement accuracy with nanometric resolution.

Automatic Frequency Tuning Technology for Dual-Mass MEMS Gyroscope Based on a Quadrature Modulation Signal.

In order to eliminate the frequency mismatch of MEMS (Microelectromechanical Systems) gyroscopes, this paper proposes a frequency tuning technology based on a quadrature modulation signal. A sinusoidal signal having a frequency greater the gyroscope operating bandwidth is applied to the quadrature stiffness correction combs, and the modulation signal containing the frequency split information is then excited at the gyroscope output. The effects of quadrature correction combs and frequency tuning combs on the resonant frequency of gyroscope are analyzed. The tuning principle based on low frequency input excitation is analyzed, and the tuning system adopting this principle is designed and simulated. The experiments are arranged to verify the theoretical analysis. The wide temperature range test (-20–60) demonstrates the reliability of the tuning system with a maximum mismatch frequency of less than 0.3 Hz. The scale factor test and static test were carried out at three temperature conditions (−20 C, room temperature, 60 C), and the scale factor, zero-bias instability, and angle random walk are improved. Moreover, the closed-loop detection method is adopted, which improves the scale factor nonlinearity and bandwidth under the premise of maintaining the same static performances compared with the open-loop detection by tuning.

Radio Frequency Fingerprint Extraction of Radio Emitter Based on I/Q Imbalance

Specific emitter identification use external signal feature called radio frequency fingerprint to identify the different radio transmitter, which does not rely on information content. A radio frequency fingerprint feature extraction approach based on I/Q imbalance of quadrature modulation signal is proposed. A I/Q modulator model is utilized to investigate the sources of radio frequency fingerprint and the effect on signal. A fingerprint features extraction based on signal space is proposed, but the SNR (Signal to Noise Ratio) need to be estimated before. Simulation results demonstrate that the method have superior performance than previous bispectrum-based, Hibert-Huang transform-based approaches.

RF-Powered Transceiver With an Energy- and Spectral-Efficient IF-Based Quadrature Backscattering Transmitter

This study introduces a 5.8 GHz RF-powered transceiver that includes a transmitter using an IF-based quadrature backscattering (IFQB) technique. The IFQB transmitter can produce a quadrature modulated signal without active RF circuits, such as PLL, local generation, and local distribution circuits. Thus, the IFQB technique can significantly reduce the power consumption while achieving denser constellations by the quadrature modulation. The RF-powered transceiver consists of the IFQB transmitter, an OOK receiver, and a power management unit (PMU) for RF powering. The transmitter and receiver operate under a 0.6 V power supply provided by the PMU to further reduce the power consumption. We fabricated a prototype RF-powered transceiver using a 65 nm Si CMOS process to confirm the validity of the proposed technique. During the measurements, the transmitter achieved 2.5 Mb/s with a 32-QAM modulation while consuming 113 µW. In addition, a wireless temperature sensing demonstration was conducted using the prototype sensor node with the presented RF-powered transceiver.

Line shape of amplitude or frequency-modulated spectral profiles including resonator distortions.

We report experiments and an improved method of analysis for any harmonics of frequency-modulated spectral line shapes allowing for very precise determinations of the resonance frequency of single absorption lines for gigahertz spectroscopy in the gas phase. Resonator perturbations are implemented into the formalism of modulation spectroscopy by means of a full complex transmission function being able to model the asymmetrically distorted absorption line shapes for arbitrary modulation depths, modulation frequencies, and resonator reflectivities. Exact equations of the in-phase and the quadrature modulation signal, taking into account a full resonator transmission function, are simultaneously adjusted to two-channel lock-in measurements performed in the gigahertz regime to obtain the spectral line position. The determination of the absorption line position of the rotational transition J' = 7 ← J" = 6 of (16)O(12)C(32)S in the vibrational ground state is investigated while changing the resonator distortions. The results are subjected to the approach proposed here and compared to standard methods known from the literature.

Behavioral modeling of nonlinear RF power amplifiers using ensemble SDBCC network

A new behavioral model of nonlinear RF power amplifiers (PA) is presented to treat memory effects. The key issue here is considering the phenomenon that uplink quadrature modulation signals are influenced not only by the current uplink signals, but also by previous terms. The variation of AM/AM and AM/PM, and the asymmetries in lower and upper intermodulation terms are frequently observed in high-power PAs. To treat these phenomena, this paper proposes a model based on artificial neural network. The contribution made of this model is to solve the order determination issue (determining the order of the previous output and input signals that have influence on the current output signal). In addition, the recognized difficulty of long training process is overcome by using SDBCC algorithm, a novel neural network design method combining structure decomposition and the Cascade-Correlation neural network algorithm. The required maximum delay is established by examining the autocorrelation coefficient of the residual error. Ensemble system is finally used to improve the performance further. This proposed method is successfully validated in nonlinear modeling of the RF PAs from HuaWei Company, including 8000 samples.

Phase-sensitive frequency conversion of quadrature modulated signals

Two mechanisms that can make frequency conversion based on nonlinear mixing dependent on the phase of the input signal are identified. A novel phase-to-polarization converter that converts the orthogonal phase components of an input signal to two orthogonally polarized outputs is proposed. The operation of this scheme and a previously reported scheme at an increased symbol rate are simulated with semiconductor optical amplifiers (SOAs) as the nonlinear devices. Experimental results demonstrate the effectiveness of SOAs for nonlinear mixing over a wide range of wavelengths and difference frequencies and confirm the accuracy of the numerical model.

Generation of pure electrical quadrature amplitude modulation with photonic vector modulator

A photonic vector modulator architecture for generating pure quadrature amplitude modulation (QAM) signals is presented. An electrical quadrature-modulated signal at microwave-millimeter-wave frequencies is generated from its corresponding baseband in-phase (I) and quadrature (Q) components. In the proposed scheme, no electrical devices apart from the electrical tone oscillator are needed in the generation process. In addition, the purity of the generated signal is increased, and the hardware requirements are reduced when compared with previously proposed architectures so a highly compact low-cost architecture can be implemented. A pure 1.25 Gbit/s 4-QAM signal has been experimentally generated at a 42 GHz carrier frequency.

Envelope Following-Based RF Transmitters Using Switching-Mode Power Amplifiers

This research presents a high-efficiency linear radio frequency transmitter applying the envelope-following technique to a switching-mode power amplifier. The use of predistorted envelope and quadrature-modulated signals can linearize the nonlinear behavior with fairly high average efficiency. The experimental results show that the proposed transmitter can deliver a 1.9-GHz CDMA2000 1times signal with high adjacent channel power ratio, low error vector magnitude, and high power added efficiency over a wide range of modulated output power

Direct photonic generation of electrical vector modulations at microwave/millimeter-wave frequencies

In this letter, a novel quadrature photonic vector modulator architecture is proposed. An electrical quadrature-modulated signal at microwave/millimeter-wave frequencies is generated from its corresponding base-band in-phase (I) and quadrature (Q) components. In the proposed scheme, no electrical devices apart from the electrical tone oscillator are needed in the generation process and, therefore, high data rates at high electrical frequencies can be obtained. In addition, the hardware requirements are reduced when compared to previously proposed architectures so a highly compact low-cost architecture can be implemented. Experimental results demonstrate the feasibility of the architecture.