Showing papers on "Digital signal published in 2009"

Spectrum-Sensing Algorithms for Cognitive Radio Based on Statistical Covariances

Abstract: Spectrum sensing, i.e., detecting the presence of primary users in a licensed spectrum, is a fundamental problem in cognitive radio. Since the statistical covariances of the received signal and noise are usually different, they can be used to differentiate the case where the primary user's signal is present from the case where there is only noise. In this paper, spectrum-sensing algorithms are proposed based on the sample covariance matrix calculated from a limited number of received signal samples. Two test statistics are then extracted from the sample covariance matrix. A decision on the signal presence is made by comparing the two test statistics. Theoretical analysis for the proposed algorithms is given. Detection probability and the associated threshold are found based on the statistical theory. The methods do not need any information about the signal, channel, and noise power a priori. In addition, no synchronization is needed. Simulations based on narrow-band signals, captured digital television (DTV) signals, and multiple antenna signals are presented to verify the methods.

Compressive wide-band spectrum sensing

Abstract: We present a compressive wide-band spectrum sensing scheme for cognitive radios. The received analog signal at the cognitive radio sensing receiver is transformed in to a digital signal using an analog-to-information converter. The autocorrelation of this compressed signal is then used to reconstruct an estimate of the signal spectrum. We evaluate the performance of this scheme in terms of the mean squared error of the power spectrum density estimate and the probability of detecting signal occupancy.

Design and Implementation of an Adaptive Tuning System Based on Desired Phase Margin for Digitally Controlled DC–DC Converters

Abstract: This letter presents an online adaptive tuning technique for digitally controlled switched-mode power supplies (SMPS). The approach is based on continuous monitoring of the system crossover frequency and phase margin, followed by a multi-input-multi-output (MIMO) control loop that continuously and concurrently tunes the compensator parameters to meet crossover frequency and phase margin targets. Continuous stability margin monitoring is achieved by injecting a small digital square-wave signal between the digital compensator and the digital pulsewidth modulator. The MIMO loop adaptively adjusts the compensator parameters to minimize the error between the desired and measured crossover frequency and phase margin. Small-signal models are derived, and the MIMO control loop is designed to achieve stability and performance over a wide range of operating conditions. Using modest hardware resources, the proposed approach enables adaptive tuning during normal SMPS operation. Experimental results demonstrating system functionality are presented for a synchronous buck SMPS.

Digital current-control schemes

Abstract: The paper is about comparing the performance of digital signal processor-based current controllers for three-phase active power filters.

System and method for determination of a horizontal minimum of digital values

Abstract: A system for fast determination of a horizontal minimum of multiple digital values including a difference circuit and a compare circuit. The difference circuit may include first and second adders in which the first adder compares upper bits of a first digital value with upper bits of a second digital value and provides a first carry output and a propagate output. The second adder compares lower bits of the first digital value with lower bits of the second digital value and provides a second carry output. The compare circuit determines whether the first digital value is greater than the second digital value based on the carry and propagate outputs. Multiple difference circuits may be used to compare each of multiple digital values with every other digital value to provide corresponding compare bits, which are then used to determine a minimum one of the digital values and its corresponding location.

Distributed compressive wide-band spectrum sensing

Abstract: We consider a compressive wide-band spectrum sensing scheme for cognitive radio networks. Each cognitive radio (CR) sensing receiver transforms the received analog signal from the licensed system in to a digital signal using an analog-to-information converter. The autocorrelation of the compressed signal is then collected from each CR at a fusion center. A compressive sampling recovery algorithm that exploits joint sparsity is then employed to reconstruct an estimate of the signal spectrum and used to make a decision on signal occupancy. We compare the performance of this distributed compressive spectrum sensing scheme with a compressive spectrum sensing scheme at a single CR and show the performance gains obtained from spatial diversity.

A High-Speed Low-Noise CMOS Image Sensor With 13-b Column-Parallel Single-Ended Cyclic ADCs

Abstract: A high-performance CMOS image sensor (CIS) with 13-b column-parallel single-ended cyclic ADCs is presented The simplified single-ended circuits for the cyclic ADC are squeezed into a 56-mum-pitch single-side column The proposed internal reference generation and return-to-zero digital signal feedback techniques enhance the ADC to have low read noise, a high resolution of 13 b, and a resulting dynamic range of 71 dB An ultralow vertical fixed pattern noise of 01 erms - is attained by a digital CDS technique, which performs A/D conversion twice in a horizontal scan period (6 mus) The implemented CIS with 018-mum technology operates at 390 frames/s and has 707-V/lx middots sensitivity, 61- muV/e- conversion gain, 49-erms - read noise, and less than 04 LSB differential nonlinearity

Continuous digital offset cancellation

Abstract: A disk drive is disclosed comprising a disk, a head for writing data to the disk, and control circuitry coupled to the head, the control circuitry comprising a signal amplifier outputting a first signal comprising an offset voltage, the control circuitry operable to determine a state signal based on comparing the first signal to a reference signal, increase a M-bit digital count value in response to a first state of the state signal, decrease the M-bit digital count value in response to a second state of the state signal, and determine a first analog signal based on N bits of the digital count value, wherein the first analog signal adjusts the offset voltage and M>N.

Intelligent electronic device for providing broadband internet access

Abstract: An intelligent electronic device for monitoring and determining an amount of electrical power usage by a consumer, or end user, and for providing broadband Internet access to the consumer. The intelligent electronic device includes at least one sensor coupled to an electric circuit configured for measuring at least one power parameter of the electrical circuit and generating at least one analog signal indicative of the at least one power parameter; at least one digital to analog converter coupled to the at least one sensor configured for receiving the at least one analog signal and converting the at least one analog signal to at least one digital signal; a processor configured for receiving the at least one digital signal and calculating energy consumption in the electrical circuit; and a gateway configured for receiving data transmissions imposed on the electrical circuit and for demodulating the imposed data transmission for providing data communications.

Generation of optical OFDM signals using 21.4 GS/s real time digital signal processing.

Abstract: We demonstrate a field programmable gate array (FPGA) based optical orthogonal frequency division multiplexing (OFDM) transmitter implementing real time digital signal processing at a sample rate of 214 GS/s The QPSK-OFDM signal is generated using an 8 bit, 128 point inverse fast Fourier transform (IFFT) core, performing one transform per clock cycle at a clock speed of 1672 MHz and can be deployed with either a direct-detection or a coherent receiver The hardware design and the main digital signal processing functions are described, and we show that the main performance limitation is due to the low (4-bit) resolution of the digital-to-analog converter (DAC) and the 8-bit resolution of the IFFT core used We analyze the back-to-back performance of the transmitter generating an 836 Gb/s optical single sideband (SSB) OFDM signal using digital up-conversion, suitable for direct-detection Additionally, we use the device to transmit 836 Gb/s SSB OFDM signals over 200 km of uncompensated standard single mode fiber achieving an overall BER<10(-3)

Optical communication system and optical receiver

Abstract: An optical receiver for receiving an optical signal that transmits a first data signal and a second data signal, including: an optical front-end configured to generate a digital signal that represents the optical signal; a detector configured to detect a state of the optical signal by using the digital signal and output state information that represents the state of the optical signal; a state controller configured to control the digital signal on the basis of the state information in order to recover the first data signal; and a data recovery configured to recover the second data signal on the basis of the state information.

Optical ofdm receiver, optical transmission system, subcarrier separation circuit, and subcarrier separation method

Abstract: A high-performance optical OFDM receiver is realized A subcarrier separation circuit receives an optical OFDM signal consisting of two subcarriers A and B and separates a subcarrier component, signal light and first local oscillator light are input to the subcarrier separation circuit, the subcarrier separation circuit converts the signal light and the first local oscillator into a baseband electrical signal, the subcarrier separation circuit converts the baseband electrical signal into a digital signal, the subcarrier separation circuit shifts the frequency of the converted digital signal so that a center frequency of the subcarrier A becomes zero, and the subcarrier separation circuit adds a frequency shifted signal to a signal obtained by delaying the frequency shifted signal by ½ of a symbol time to separate a component of the subcarrier A

System and method of reducing power consumption for audio playback

Abstract: A system and method of improving the efficiency in the power consumption of an audio system. In essence, the technique is to adjust the power delivered from the power supply to the analog section, such as the power amplifier, in response to the volume level indicated by the volume control module and/or in response to the detected characteristic of the input audio signal. Thus, in this manner, the analog section is operated in a manner that is related to the level of the signal it is processing. Additionally, the system and method also relate to a technique of adjusting the dynamic ranges of the digital signal and the analog signal to improve the overall dynamic range of the system without needing to consume additional power.

Physical quantity measuring apparatus and electronic device

Abstract: A physical quantity measuring apparatus includes an oscillation drive circuit that forms an oscillation loop together with a physical quantity transducer and excites a drive oscillation of the physical quantity transducer, and a detection circuit that detects an analog detection signal outputted from the physical quantity transducer using a detection circuit first and thence converts the signal that has been detected into a digital signal using an A/D converter to output the digital signal. The oscillation drive circuit has a drive amplitude detection circuit that detects amplitude of the drive oscillation. A voltage level of a reference of the A/D converter included in the detection circuit is controlled on the basis of a detection output signal of the drive amplitude detection circuit.

Method and apparatus for improving digital predistortion correction with amplifier device biasing

Abstract: A method, apparatus, and electronic device for using digital predistortion are disclosed. A transmitter (212) may transmits a transmission signal. A receiver (214) may monitor the transmission signal to execute digital predistortion of the transmission signal to compensate for distortion. A field programmable gate array or application specific integrated circuit (226) may adjust a power amplifier bias to improve the digital predistortion.

Information processing apparatus and signal transmission method

Abstract: An information processing apparatus is provided which includes a signal multiplexing unit for multiplexing a plurality of transmission signals, each in a different frequency band and not containing a DC component, and a power signal supplied from a DC power supply and generating a multiplexed signal, a single signal cable through which the multiplexed signal generated by the signal multiplexing unit is transmitted, and a signal separating unit for separating the multiplexed signal transmitted through the signal cable into signals, each in a frequency band of one of the plurality of transmission signals, and a signal in a frequency band of the power signal.

Predicting Microwave Digital Signal Integrity

Abstract: High-speed digital signal integrity at data rates above 6 Gb/s is an obstacle to reliable serial link operation. Two signal integrity challenges include dispersion due to frequency-dependent losses and reflections created at impedance mismatches. Signal integrity analysis relies on time-domain simulation of pseudo-random data patterns. This paper explores a predictive method for interconnect eye closure caused by reflections at the transmitter and receiver and does not require extensive time domain simulation. Worst-case bounds on intersymbol interference and data-dependent jitter aid prediction for link budgets under channel variations. This method is applied to the design of a passive equalizer.

Communication device, communication system, reception method, and communication method

Abstract: Provided is a communication device which performs a hybrid automatic repeat request process of requesting a transmission source to perform retransmission when an error is detected from a received signal. The communication device includes: a reception unit that receives a signal into which an initial transmission signal and a retransmission signal are multiplexed among signals including the initial transmission signal and the retransmission signal for any one signal; a detection order decision unit that decides an order of detection of the initial transmission signal and the retransmission signal from the signal received by the reception unit in response to the number of retransmissions of the initial transmission signal and the retransmission signal which are included in the signal received by the reception unit; and a signal detection unit that removes an interference component from the signal received by the reception unit by using a signal detected by the communication device according to the order decided by the detection order decision unit, and that detects the initial transmission signal and the retransmission signal. An increase of delay can be prevented when retransmission is repeated.

Ultra low-power angular position sensor for high-speed portable applications

Abstract: We present a technique for contactless angular position sensing that allows low power consumption while keeping dynamic properties comparable to existing sensors. The technique essentially consists in combining a recently developed sensing element, the so-called Circular Vertical Hall Device, with a simple and robust signal treatment based on phase detection. Because of its low startup time, this circuit is specially suited for pulsed mode operation, which enables to further decrease the power consumption. More generally, the absence of complex digital signal treatment makes this technique a natural method for measuring the magnetic field direction and therefore for designing an angular position sensor using Hall probes.

Switching power supply and related control method

Abstract: A switching power supply includes a power switch, an adjusting circuit and a limit signal generator. The power switch operates according to a switch control signal. The adjusting circuit adjusts the turn-on time of the switch control signal according to a limit signal and a detecting signal which corresponds to the current passing the power switch. When the detecting signal exceeds or is equal to the limit signal, the limit signal generator samples a reference signal and updates the limit signal according to the sampled reference signal.

Feasibility study of using acoustic signals for online monitoring of the depth of weld in the laser welding of high-strength steels

Abstract: It is a trend to use high-strength steels in the automobile industry because of their good formability, weldability, and high strength-volume ratio. In order to achieve quality control, it is necessary to monitor the welding process online. In this paper, acoustic signals generated during the laser welding process of high-strength steel DP980 were recorded and analysed. A microphone was used to acquire the acoustic signals. A spectral subtraction method was used to reduce the noise in the acoustic signals, and a Welch-Bartlett power spectrum density estimation method was used to analyse the frequency characteristics of the acoustic signals. The results indicate that good welds with full penetration (FP) could be clearly distinguished from bad welds with partial penetration (PP). An algorithm based on the different sound pressures between FP and PP was developed to identify the penetration state in the time domain. Another algorithm based on the different frequency characteristics from 500 to 1500 Hz between FP and PP was also developed to differentiate the penetration state. The results show that these two algorithms can effectively distinguish FP from PP. In addition, the mechanisms of the different characteristics of the acoustic signal generated from different penetration depths and modes were also analysed and discussed. This study shows that it is feasible to use acoustic signals to achieve online monitoring of the penetration states during the laser welding of high-strength steel DP980 in a noisy environment by applying proper digital signal processing methods. The acquired acoustic signal could be used as a feedback signal to control the depth of weld penetration in the laser welding process.

On the Coherence Time Control of a Continuous Mode Stirred Reverberating Chamber

Abstract: In this communication, a new methodology on the control of the mode-stirred reverberating chamber (RC) coherence time is accomplished. This communication shows how it is possible to evaluate the RC coherence time values with the method of the normalized autocorrelation function (ACF). The coherence time values obtained from measured data via the ACF have been used in a channel simulator and then the computed constellation has been compared with measurements for a global system for mobile communication (GSM) signal. A visual inspection of the constellation as well as the comparison of measured and computed modulation error rate (MER) and bit error rate (BER) values have been done. The methodology is general and actually applicable to a large class of electromagnetic digital input signals, once that no error of modulation occurs and the channel does not cause distortion in the received signal.

Apparatus and method for determination of signal format

Abstract: The determination of the signal modulation format for a channel is an important aspect of the operation of a signal receiver. A method (700) is described including the steps of receiving (710) a signal, comparing (720) a sample of the received signal to a first threshold value and a second threshold value, creating (720) a signal profile based on the comparison, and selecting (750) a modulation format for the received signal based on the signal profile. An apparatus (500) is also described including a ring counter (510) that receives a sample of an input signal, compares the sample to a first threshold value and a second threshold value, and creates a signal profile for the input signal, a signal profiler (550) that compares the signal profile for the input signal to at least two reference profiles, and a detector (560) that determines a modulation format for the input signal based on the comparison in the signal profiler (550).

Front end circuitry for imaging systems and methods of use

Abstract: Pulse-echo imaging systems and methods are provided, including a transmit code sequencer and a pulse generation circuit. The transmit code sequencer is configured to input a transmit code sequence to the pulse generation circuit. A transducer is configured to receive electrical signals provided as pulses using coded excitation according to the transmit code sequence, and to transduce the electrical signals to pulses of energy other than electrical signals. The transducer is further configured to receive echoes of the pulses of energy other than electrical signals and convert the echoes to received electrical signals generate using coded excitation. A receive receive circuit is configured to receive the received electrical signals generate using coded excitation, perform analog sampling of the received electrical signals generate using coded excitation, and provide a weighted, summed digital signal by processing the analog samples.

Accuracy and resolution of ultrasonic distance measurement with high-time-resolution cross-correlation function obtained by single-bit signal processing

Abstract: Distance measurement using an ultrasonic wave is suitable for environment recognition in autonomous mobile robots. Ultrasonic distance measurement with the pulse-echo method is based on the determination of the reflected echo's time of flight (TOF). Pulse compression can improve distance resolution and the reflected echo's signal-to-noise ratio (SNR). However, calculation of cross correlation requires high-cost digital signal processing. A sensor signal processing method of cross correlation using a delta-sigma modulated single-bit digital signal has been proposed. Cross correlation by single-bit signal processing reduces the calculation costs of cross correlation. Furthermore, cross correlation by single-bit signal processing improves the time resolution of the cross-correlation function. Therefore, the high-time-resolution cross-correlation function improves the distance resolution of the cross-correlation method. In this paper, ultrasonic distance measurement using cross correlation by single-bit signal processing is evaluated based on computer simulations and the experimental results.

Active pulse positioning modulator

Abstract: An adaptive pulse positioning modulator including a sense circuit which provides a compensation signal indicative of output voltage error, a filter circuit having an input receiving the compensation signal and an output providing an adjust signal, a leading ramp circuit which provides a repetitive first leading edge ramp signal having a slope which is adjusted by the adjust signal, a comparator circuit which provides a first start trigger signal when the first leading edge ramp signal reaches the compensation signal and a first end trigger signal when a first trailing edge ramp signal reaches the compensation signal, a trailing ramp circuit which initiates ramping of the first trailing edge ramp signal when the first start trigger signal is provided, and a pulse control logic which asserts pulses on a PWM signal based on the trigger signals.

Power source sensing dimming circuits and methods of operating same

Abstract: Lighting is controlled by receiving an input signal, determining whether the input signal is an AC signal or a DC signal and generating a dimming command signal based on the determination of whether the input signal is an AC signal or a DC signal. For example, determining whether the input signal is an AC signal or a DC signal may include generating an average signal indicative of an average duty cycle of the input signal and determining whether the average signal meets a predetermined criterion.

Digital PWM controller for high-frequency low-power DC-DC switching mode power supply

Abstract: This paper presents a fully synthesizable digital controller for high-frequency low-power DC-DC switching mode power supply (SMPS). Key module of the digital controller is a Hybrid digital pulse-width modulator (DPWM), which takes advantage of Digital Clock Manager (DCM) phase-shift characteristics available in FPGA resource and combines a counter-comparator with multi-bit Delta-Sigma (Δ-Σ) Multi-stAge-noise-SHaping (MASH) modulator. A digital controller which includes the proposed Hybrid Δ-Σ DPWM and a digital PID algorithm is experimentally verified using an FPGA on a high-frequency low-power discrete synchronous buck converter. Experimental results with constant switching frequency up to 4MHz validate the functionality of the proposed digital controller. In addition, the digital controller is implemented in a 0.35 µm standard CMOS.