Quadrature Signal Processing Research Articles

Quadrature phase-coded signal model and signal processing method for frequency diverse array radar

Quadrature phase-coded signal model and signal processing method for frequency diverse array radar

Application of combined optical signal processing methods to compensate for nonlinear effects in fibre-optic communication links

We report on the use of complex quadrature amplitude signal processing methods based on a combination of static neural networks and special modulation techniques. The conditions are found that allow one to construct the most effective combination of signal processing methods for transmitting signals with considerable power (in the nonlinear regime). Using analytical methods, it is shown how the statistical properties of a signal affect the efficiency of combined processing methods.

A CMOS vector lock-in amplifier for sensor applications

The design of an integrated lock-in amplifier is discussed, specifically conceived for the detection of low-level signals at a harmonic of the drive frequency in magnetically excited resonant structures. The circuit includes in-phase and quadrature analogue signal processing channels, whose outputs feed an integrated ΣΔ analogue to digital converter. The circuit can be operated in different configurations, depending on the application requirements: in particular, by combining the digitized outputs of the two channels, vector operation can be obtained. The entire analogue chain, including the ΣΔ modulator, was designed using fully differential elaboration. The circuit was developed in a 0.35μm, dual poly-Si, four metal layers analogue CMOS technology with high resistivity poly-Si option. Circuit performance is discussed on the basis of transistor-level simulations and measurement results.

Auto calibration with training sequences for wireless local loop at 26 GHz

Quadrature signal processing is widely used in current communication receivers. However, all inphase/quadrature (I/Q) processing receiver structures face a common problem of matching the amplitudes and phases of the inphase and the quadrature branches. This article proposes an auto calibration method, for I/Q imbalance compensation using base band digital processing on training sequences transmitted with data bursts of a test platform for a wireless local loop at 26 GHz. After a description of the test platform, a calibration method is proposed and its influence on the improvement of the transmission's performance, in term of phase constellation diagram and bit-error rate, presented.

시간지연 샘플링을 이용한 광섬유 격자 센서어레이의 선형 복조

파장가변형 광섬유레이저로 광섬유격자 센서어레이를 복조하는 방법을 제안하였다. 레이저의 출력파장을 시간지연 샘플링으로 분석하고 이를 이용하여 기존 시스템의 비선형적 동작특성을 개선하였다. 계산된 파장값은 센서어레이 출력파평의 각 피크에 할당되어 파장가변필터의 비선형성에 영향받지 않고 가해진 물리량에 대하여 항상 선형적인 출력을 얻게 하였다. 실험을 통하여 약 20 pm의 분해능을 얻었으며 이는 고속의 위상변조를 사용할 경우 크게 개선될 수 있음을 보였다. A fiber laser of which wavelength was scanned by an intra-cavity FP (Fabry-Perot) filter was used to interrogate a fiber Bragg grating strain sensor array. We calculated the wavelength variation of the fiber laser using quadrature signal processing with an unbalanced M/Z (Mach-Zehnder) interferometer and time-delayed sampling technique. The calculated wavelengths are mapped to corresponding temporal reflection peaks from the sensor array, which enables more accurate and stable interrogation without the problems caused by the FP filter's nonlinear characteristics. Wavelength resolution of ∼20 pm was obtained in our experimental setup, which could have been greatly enhanced with faster phase modulation.

A Wideband Interferometric Wavelength Shift Demodulator of Fiber Bragg Grating Strain Sensor

The performance of a fiber Bragg grating strain sensor constructed with 3 $\times$ 3 coupler is investigated. A 3 $\times$ 3 coupler Mach-Zehnder (M/Z) interferometer is used as wavelength discriminator, interrogating strain-induced Bragg wavelength shifts. Two quadrature-phase-shifted intensities are synthesized from the as-coupled interferometer outputs, and digital arctangent demodulation and phase unwrapping algorithm are applied to extract the phase information proportional to strain. Due to the linear relation between the input strain and the output of quadrature signal processing, signal-fading problems eliminated. In the experiment, a fiber grating that was surface adhered on an aluminum beam was strained in different ways, and the photodetector signals were transferred and processed in a computer-controlled processing unit. A phase recovery fo 7.8 $\pi$ pk-pk excursion, which corresponds to ~650 $\mu$ strain pk-pk of applied strain, was demonstrated. The sensor system was stable over the environmental intensi쇼 perturbations because of the self-referencing effect in the demodulation process.

In-fiber Bragg grating sensors using interferometric interrogations for passive quadrature signal processing

This letter describes a simple optically passive detection scheme for Bragg grating sensors. This detection scheme is based on two cavity lengths in Fabry-Perot read-out interferometers to produce two quadrature phase shifted signals from the Bragg grating sensor. Using the amplified spontaneous emission from an erbium-doped fiber amplifier as a low-coherence and high-power broad-band source, the passive detection technique is demonstrated by the use of Bragg grating sensors in dynamic strain measurements. This scheme is capable of measuring dynamic strain with a resolution of 0.1 /spl mu//spl epsiv///spl radic/(Hz) root mean square at a frequency of 500 Hz for 600 /spl mu/m cavity length in the Fabry-Perot read-out system.

Fabry-Perot sensors for dynamic studies using spectrally based passive quadrature signal processing

This paper describes a simple, optically passive detection scheme for in-line Fabry-Perot etalon (ILFE) sensors that is also useful for intrinsic Fabry-Perot (IFP) and extrinsic Fabry-Perot interferometer (EFPI) sensors. This detection scheme is based on two spectrally shiffed Bragg wavelengths from in-line Bragg gratings to produce two quadrature phase shifted signals from the spectral transfer function of the Fabry-Perot sensor. Using the amplified spontaneous emission (ASE) from an erbium-doped fiber amplifier (EDFA) as a low-coherence, high-power broad-band source, the passive detection technique is used to demonstrate the use of ILFE sensors in high strain rate dynamics studies. This study is designed to characterize the high strain rate response of optical fiber sensors and test their ability to monitor dynamic strain changes resulting from one-dimensional stress wave propagation.

Implementación de un espectrómetro NMR en cuadratura basado en una red RC pasiva splitter-combiner

El presente artículo describe la arquitectura de un espectrómetro NMR en cuadratura, se identifican los componentes claves que marcan el límite entre los mundos analógico y digital. Se explican en detalle los requerimientos de un modulador y demodulador que usan splitters y combiners en cuadratura y se discuten las especificaciones necesarias para estos elementos. Se introduce la arquitectura de una red RC pasiva utilizada como splitter-combiner, se describen las decisiones tomadas en el diseño y se presentan los resultados de simulaciones y test. Para terminar se presenta una caracterización total de algunos moduladores y demoduladores junto con las estrategias de calibración las cuales alcanzan una altísima presición en el proceso de señales en Cuadratura y caracterizan al mismo tiempo los errores del sistema.