One-bit Sigma-delta Modulator Research Articles

Artificial TMAP Signal Generator Based on One-Bit Sigma Delta Modulator for MEC Test

The current study proposes three electrode-channels with time delay of artificial nerve signals generator utilized with only a active low pass filter and a Field Programmable Gate Array (FPGA). The XC3S100E FPGA board adopted to design a novel and real-time artificial transmembrane action potential (TMAP). The implementation of one bit Sigma Delta Modulation (SDM) method with linearized technique could be very expensive and complicated products with other technologies option currently available such as a microcontroller due to the fabrication requirements. This technique could employ in many biomedical applications and testing efficiently, especially, in evaluating the multi-electrode cuff system without requiring use of real nerves spike from animal models and saving time and effort, and cost. Moreover, this approach is adopted for further improvement to the signal performances such as resolution, accuracy, differential linearity monotonic DAC, and settling time of the signal waveform without extra hardware or cost required. In addition, the design included three channels of white Gaussian noise uncorrelated for each TMAP signal to simulate the real nerve noise environment, which surrounds the electrode cuff in experimental cases. A noise channels with adjustment level is added to the nerve spike using three sets of taps are employed to provide three channels of noise sources. The Xilinx ISE platform and Mentor Graphics ModelSim tool are used to simulate and implement this, and the results produced are compared. The power consumption of conventional technology is 31 mW, which is significantly higher than the power consumed (21mW) in modern technology. Furthermore, as compared to the usual way, the proposed solution conserved around 10% of the FPGA resources. This technique offers reuse in other applications where delay time, low amplitude voltage signals, and multichannel generator is needed. Moreover, this system offers adjustable waveform signal, noise level, conduction velocity and time delay easily to adequate different applications and tests.

One-Bit Sigma-Delta Modulator for Nonlinear Visible Light Communication Systems

In a visible light communication (VLC) system, the modulation bandwidth of light emitting diode (LED) is limited with current technology. In addition, the nonlinearity inherited in the LED prevents the application of spectral efficient modulation schemes with high peak-to-average power ratio. These characteristics limit the overall throughput of the VLC system. In this letter, a one-bit sigma-delta modulator (SDM) is introduced to the transmit signal. Such modification is compatible with the current LED lighting systems and LED drivers as the output of the one-bit SDM is equivalent to ON-OFF keying signal, thus is immune to system nonlinearities. In addition, the output of the one-bit SDM enjoys high spectral efficiency as the original input signal does. The out-of-band quantization noise can be taken care of at the receiver with analog filtering and digital signal processing. Simulation and experiment results validate that the SDM can significantly improve the VLC system performance.

On the effect of the integrator initial state in a non-ideal sigma–delta-modulator

This paper examines the dynamics of an electronic system—a single-loop one-bit sigma–delta modulator in the presence of integrator leak which is not necessarily a constant. We prove that the difference of the moving averages of any two output sequences of the modulator (arising from different initial conditions of the integrator) is inversely proportional to the averaging length. The result demonstrates the insensitivity of the time average of the modulator output to the initial condition of the integrator.

A constant temperature operation thermoresistive sigma–delta solar radiometer

In this paper we propose a feedback system, with thermoresistive sensor, based on sigma–delta modulation. This system uses an one-bit sigma–delta modulator in which considerable part of conversion functions is performed by a thermoresistive sensor. The sensor is modelled using the power balance principle and the applied measure method is constant temperature. This transducer architecture is able to perform digital measurement of physical quantities that interacts with the sensor: temperature, thermal radiation and fluid velocity. This paper presents simulation results of this system applied to thermal radiation measurement.

A sixth-order continuous-time bandpass sigma-delta modulator for digital radio IF

This paper presents a sixth-order continuous-time bandpass sigma-delta modulator (SDM) for analog-to-digital conversion of intermediate-frequency signals. An important aspect in the design of this SDM is the stability analysis using the describing function method. The key to the analysis is the extension of the linear gain model for the sampled quantizer with a phase uncertainty. The single-loop, one-bit SDM is tuned at 10.7 MHz, is sampled at 40 MHz, and achieves 67-dB signal-to-(noise+distortion) ratio in 200 kHz and 80 dB in 9 kHz. The third order intermodulation is at -82 dBc for a -13-dBFS input level. The 0.5-/spl mu/m CMOS chip occupies 0.9/spl times/0.4 mm/sup 2/ and consumes 60 mW at 3.3 V (digital) and 5.0 V (analog). The sample frequency is variable and can be set from 30 to 80 MHz.