Design and Implementation of DSP—Based IEEE802.16a OFDM System

A set of integrated Orthogonal Frequency Division Multiplexing(OFDM) modulation and demodulation system is proposed and its performance is verified in reference to the standard of IEEE802.16a for WMAN.The design,combined with analogy front-end,adopts Texas Instrument(TI) Company's 6701 evaluation module(EVM) to construct digital Intermediate Frequency(IF) platform.A DSP-based baseband processing software module is embedded into the system.The proposed scheme makes it possible for users to select various software modules to set up connections with different throughput performance.Taking into account the given hardware configuration,the design aims to optimize the algorithm modules to accomplish better system performance.

High efficiency spreading spectrum modulation using double orthogonal complex sequences

This paper presents a novel scheme of high efficiency spreading spectrum modulation using double orthogonal complex sequences （DoCS）. In this scheme, input data bit-stream is split into many groups with length M. Each group is then mapped into a word of width M and then utihzed to select one sequence from 2u-2 DoCS sequences each with length L. After that, the selected sequence is modulated on carrier in quadrature phase shift keying （QPSK） mode. In addition, a new method named forward phase correction （FPC） is put forward for carrier recovery. Theoretical analysis and bit-error-ratio（BER） experiment results indicate that the proposed scheme has better performance than the conventional direct sequence spread spectrum（DSSS） scheme both in bandwidth efficiency and processing gain of the receiver.

A 330-W single-frequency retrievable multi-tone monolithic fiber amplifier

A single-frequency retrievable phase modulated multi-tone fiber amplifier is presented in theory and demonstrated in experiment. A multi-tone seed laser generated by a sine wave phase modulated single-frequency laser is employed for stimulated Brillouin scattering suppression in an all-fiber amplifier. A demodulation signal which is π phase shifted with respect to the modulation signal is used to retrieve the single-frequency laser from the multi-tone laser. In experiment, we first optimize the all-fiber master-oscillator power-amplifier. With this amplifier, we demonstrate a single-frequency retrievable multi-tone laser with 330-W output when driven by the multi-tone seed, while the ultimate output power is only 130 W when driven by the single-frequency laser. Then, we carry out an experiment for retrieving the single-frequency laser from the amplified multi-tone laser. Results indicate that the single-frequency laser can be retrieved with a sideband suppression of more than 20 dB. Retrieving an even higher power single-frequency laser is possible if a high power demodulator is available.

Design of inductive coupling channel analysis system based on LabVIEW

Inductive coupling transmission system is an important measurement device for acquiring and transmitting marine environmental information.However,low transmission rate cannot meet the current demand for large data transmission in marine environment detection at home.In order to improve the transmission performance of the system in practical communication system,optimizing the design by directly changing the circuit parameters is time-consuming and expensive.Therefore,a set of inductive coupling transmission channel analysis system is designed based on virtual instrument to improve the transmission rate and reliability of inductive coupling transmission system.The bit error rate of channel system at different frequency and noise levels are tested by using three kinds of digital modulation mode including amplitude shift keying(ASK),frequency shift keying(FSK)and differential phase shift keying(DPSK),taking square wave and sine wave as a carrier.Finally,the sine wave is selected to be carrier signal and DPSK is chosen to be modulation mode.The reliable transmission of signal with the error rate less than0.005and the transmission rate of9600bps,at the noise level of-10dB,is realized and verified by the debugging circuit experiments with multi-nodes in the laboratory.The study provides an important experimental evidence for improving signal transmission reliability of inductive coupling transmission system.

116 dB dynamic range CMOS readout circuit for MEMS capacitive accelerometer

A high stability in-circuit reprogrammable technique control system for a capacitive MEMS accelerometer is presented. Modulation and demodulation are used to separate the signal from the low frequency noise. A low-noise low-offset charge integrator is employed in this circuit to implement a capacitance-to-voltage converter and minimize the noise and offset. The application-specific integrated circuit （ASIC） is fabricated in a 0.5 /μm one-ploy three-metal CMOS process. The measured results of the proposed circuit show that the noise floor of the ASIC is -116 dBV, the sensitivity of the accelerometer is 66 mV/g with a nonlinearity of 0.5%. The chip occupies 3.5×2.5 mm2 and the current is 3.5 mA.