Traditional Demodulation Method Research Articles

Accelerate Demodulation of Quadrature Amplitude Modulation Using GPU

Quadrature amplitude modulation (QAM) is widely used in communication systems. The traditional QAM demodulation method was implemented in hardware. This paper proposes a demodulation algorithm using GPU. The GPU algorithm is easier to add new features than hardware implementation and reaches 57x speed up compared with the serial algorithm on CPU. It is shown that the QAM demodulation algorithm gained significant performance increase due to the natural parallism of the GPU, using Compute Unified Device Architecture (CUDA).

4PSK Signal Based on FPGA

Based on the traditional demodulation method of four phase shift keying (QPSK), a QPSK demodulation model was proposed. The FPGA-based QPSK modulation and demodulation system and circuit had been achieved. In Xilinx ISE12.3 development environment, using the SPARTAN-3E development board, the simulation results demonstrate the feasibility of this design.

Quadrature demodulation with synchronous difference for interferometric fiber-optic gyroscopes

We propose a novel method of quadrature demodulation with synchronous difference for suppressing noise in interferometric fiber-optic gyroscopes (IFOGs). For an IFOG with sine wave phase modulation, an in-phase result and a quadrature result are obtained simultaneously by coherent detection. Eigenfrequency modulation is used and a phase shift of 45° is set between the modulation signal and the reference signal, so that two results have the same expectation of amplitude but with opposite signs. A synchronous difference procedure is carried out for output, in which signals are added up and common noise between two results is eliminated. Theoretical analysis and experimental results show that both short term noise and long term instability of the IFOG are reduced by this method. In experimental comparison with the traditional demodulation method on the same IFOG with a 1982 m fiber coil, this method reduces the bias drift from 0.040°/h to 0.004°/h.

A best method of demodulation algorithm for UNFSK applied in transportation

The frequency shift of the ultra-narrow frequency shift keying (UNFSK) is far less than the ordinary binary frequency shift keying (FSK) method. Because the two frequencies of UNFSK are extremely close, the traditional demodulation method cannot separate them successfully. This study aims to successfully demodulate the UNFSK signals by applying cycle extension and notch filter. The signal processing procedure is as follows: First, the sampling signals have been made cycle extension to enlarge their spectrum difference between signal 0 and 1; secondly, the cycle extension signals have been processed by the notch filter algorithm and finally, we could get the information by sentencing the filtering result. Finally, the method is applied in transportation. The simulation results proved that the algorithm greatly enhanced UNFSK signal demodulation performance, compared to the traditional demodulation method. There can be 2–3 dB improvement in performance, which is very suitable for UNFSK.

Simulation studies on chaos demodulation of weak BPSK signal based on Simulink tools

Concerning the problem of demodulating the weak Binary Phase Shift Keying (BPSK) signal,the demodulation method based on chaotic system was researched. The basic principle of the chaotic system weak signal detection was introduced. By combining with the phase condition of the phase change happening and the modulation method of BPSK signal,the methods and steps of using Duffing system to demodulate the BPSK signal in strong noisy background were given. And a new method was presented for power spectrum entropy to judge the complexity of the different system state. Based on theoretical analysis,the simulation model based on Matlab/Simulink was built. The digital simulation results show that the performance of demodulating the weak BPSK signal using chaotic oscillator and power spectrum entropy is better than that of traditional coherent demodulation method.

An image-rejecting mixer and vector filter with 55-dB image rejection over process, temperature, and transistor mismatch

This paper describes an image-rejecting mixer and vector filter for use in radio systems with channel bandwidths in the range of 1 MHz. The circuit replaces the SAW filter and second downconverter commonly used in this style of radio. Because the output of the circuit is at an IF of 5 MHz, traditional demodulation methods including limiting and FM discrimination can still be used. The circuit is based on a quadrature mixer that guarantees good performance despite device mismatches and process variation. The circuit consumes 29 mA at 3.3 V,and achieves better than 55-dB image rejection despite device mismatches and process variation and is implemented in a single-poly triple metal 0.5 /spl mu/m CMOS process with linear capacitor implants. The circuit is designed for input signals from 125 to 250 MHz. Input referred voltage noise is 900 /spl mu/Vrms. The in-band IP3 is 18 dBm. By changing an external reference frequency, the passband width of the filter can be varied from 3 to 0.5 MHz.