Showing papers on "Demodulation published in 2015"

A 0.13 μm CMOS System-on-Chip for a 512 × 424 Time-of-Flight Image Sensor With Multi-Frequency Photo-Demodulation up to 130 MHz and 2 GS/s ADC

Abstract: We introduce a 512 × 424 time-of-flight (TOF) depth image sensor designed in a TSMC 0.13 μm LP 1P5M CMOS process, suitable for use in Microsoft Kinect for XBOX ONE. The 10 μm × 10 μm pixel incorporates a TOF detector that operates using the quantum efficiency modulation (QEM) technique at high modulation frequencies of up to 130 MHz, achieves a modulation contrast of 67% at 50 MHz and a responsivity of 0.14 A/W at 860 nm. The TOF sensor includes a 2 GS/s 10 bit signal path, which is used for the high ADC bandwidth requirements of the system that requires many ADC conversions per frame. The chip also comprises a clock generation circuit featuring a programmable phase and frequency clock generator with 312.5-ps phase step resolution derived from a 1.6 GHz oscillator. An integrated shutter engine and a programmable digital micro-sequencer allows an extremely flexible multi-gain/multi-shutter and multi-frequency/multi-phase operation. All chip data is transferred using two 4-lane MIPI D-PHY interfaces with a total of 8 Gb/s input/output bandwidth. The reported experimental results demonstrate a wide depth range of operation (0.8–4.2 m), small accuracy error ( $ 1%), very low depth uncertainty ( $ 0.5% of actual distance), and very high dynamic range ( $>$ 64 dB).

Phase-Sensitive Optical Time Domain Reflectometer Based on Phase-Generated Carrier Algorithm

Abstract: We propose a novel approach to generate distributed fiber sensing system based on phase-sensitive optical time domain reflectometer (Φ-OTDR) and phase-generated carrier demodulation algorithm. An unbalanced Michelson interferometer is introduced at the receiving end of the system. The back Rayleigh scattering light from a certain position along the sensing fiber would interfere to generate interference light signal versus time, whose phase carries the sensing information. Phase-generated carrier demodulation algorithm is proposed and carried out to recover the phase information. A single frequency vibration event is applied to a certain position along the sensing fiber and we realize to demodulate it correctly. The noise level of the phase sensitive OTDR system is about $3 \times 10^{-3}$ rad/SHz and a signal to noise ratio about 30.45 dB is achieved. The maximum sensing length and the spatial resolution of the Φ-OTDR system are 10 km and 6 m with pulse repetition rate at 10 kHz and 6 m fiber delay in MI with interrogating pulse width of 30 ns.

Unlocking Spectral Efficiency in Intensity Modulation and Direct Detection Systems

Abstract: A number of inherently unipolar orthogonal frequency division multiplexing (OFDM) modulation schemes have been introduced recently in an attempt to improve the energy efficiency of OFDM-based intensity modulation and direct detection (IM/DD) systems. All such algorithms, including asymmetrically clipped optical OFDM (ACO-OFDM), pulse-amplitude-modulated discrete multitone modulation (PAM-DMT) and unipolar orthogonal frequency division multiplexing (U-OFDM), experience an inherent loss in spectral efficiency caused by the restrictions imposed on the OFDM frame structure required for the generation of a unipolar signal. The current paper presents a modified modulation approach, termed enhanced U-OFDM (eU-OFDM), which compensates the spectral efficiency loss in U-OFDM. At the same time, it still allows for the generation of an inherently unipolar modulation signal that achieves better performance in terms of both electrical power and optical power dissipation compared to the conventional state-of-the-art technique direct current (DC)-biased optical OFDM (DCO-OFDM). To the best of the authors' knowledge, the current work also presents the first experimental proof-of-concept demonstration of both U-OFDM and eU-OFDM, and clearly demonstrates the significant energy advantages that these two schemes can introduce in an optical wireless communications (OWC) system.

Differentially Coherent Multichannel Detection of Acoustic OFDM Signals

Abstract: In this paper, we propose a class of methods for compensating for the Doppler distortions of the underwater acoustic channel for differentially coherent detection of orthogonal frequency-division multiplexing (OFDM) signals. These methods are based on multiple fast Fourier transform (FFT) demodulation, and are implemented as partial (P), shaped (S), fractional (F), and Taylor (T) series expansion FFT demodulation. They replace the conventional FFT demodulation with a few FFTs and a combiner. The input to each FFT is a specific transformation of the input signal, and the combiner performs weighted summation of the FFT outputs. The four methods differ in the choice of the pre-FFT transformation (P, S, F, T), while the rest of the receiver remains identical across these methods. We design an adaptive algorithm of stochastic gradient type to learn the combiner weights for differentially coherent detection. The algorithm is cast into the multichannel framework to take advantage of spatial diversity. The receiver is also equipped with an improved synchronization technique for estimating the dominant Doppler shift and resampling the signal before demodulation. An additional technique of carrier sliding is introduced to aid in the post-FFT combining process when residual Doppler shift is nonnegligible. Synthetic data, as well as experimental data from a recent mobile acoustic communication experiment (few kilometers in shallow water, 10.5–15.5-kHz band) are used to demonstrate the performance of the proposed methods, showing significant improvement over conventional detection techniques with or without intercarrier interference equalization (5–7 dB on average over multiple hours), as well as improved bandwidth efficiency [ability to support up to 2048 quadrature phase-shift keying (QPSK) modulated carriers].

A Capacitive Rotary Encoder Based on Quadrature Modulation and Demodulation

Abstract: This paper presents a capacitive rotary encoder for both angular position and angular speed measurements. The encoder is mainly composed of three parts: the transmitting segments; a pair of reflecting electrodes; and a pair of receiving electrodes. The transmitting segments together with four mutual quadrature carrier voltages provide a modulated electric field. The reflecting electrodes, which are patterned sinusoidally can encode the angular position to a phase/frequency modulated signal based on quadrature modulation. The modulated signal is then digitally decoded to the angular position in a field programmable gate array processor based on the quadrature demodulation and the coordinate rotational digital computer algorithm. Through a universal serial bus, the digital angular position is transmitted to a computer for further analysis in National Instruments' LabVIEW software. A prototype of the capacitive encoder shows that its precision is better than 0.006° and the resolution is 0.002°. The dynamic nonlinearity is evaluated at ±0.4° when the rotor is rotating at 1000 r/min.

Fast White Light Interferometry Demodulation Algorithm for Low-Finesse Fabry–Pérot Sensors

Abstract: Over decades, the signal demodulation techniques of low-finesse Fabry–Perot interferometer (FPI) sensors have been either slow with wide dynamic range and absolute measurement capability, or fast with narrow dynamic range and relative measurement capability. The tradeoff between the speed and the measurement capability has greatly limited the application of FPI-based sensors. In this letter, a novel high-speed white light interferometry (WLI) demodulation algorithm for low-finesse FPI has been developed. By realizing high-speed absolute demodulation utilizing full spectra, the new algorithm has the advantage of spectral drift immunity, high precision, and simultaneous ac and dc signal measurement capability, such as acoustic and temperature. A 70-kHz real-time WLI demodulation experiment was conducted in lab, in which the speed was limited only by the spectrometer hardware.

A Markovian Approach to the Optimal Demodulation of Diffusion-Based Molecular Communication Networks

Abstract: In a diffusion-based molecular communication network, transmitters and receivers communicate by using signalling molecules (or ligands) in a fluid medium. This paper assumes that the transmitter uses different chemical reactions to generate different emission patterns of signalling molecules to represent different transmission symbols, and the receiver consists of receptors. When the signalling molecules arrive at the receiver, they may react with the receptors to form ligand-receptor complexes. Our goal is to study the demodulation in this setup assuming that the transmitter and receiver are synchronised. We derive an optimal demodulator using the continuous history of the number of complexes at the receiver as the input to the demodulator. We do that by first deriving a communication model which includes the chemical reactions in the transmitter, diffusion in the transmission medium and the ligand-receptor process in the receiver. This model, which takes the form of a continuous-time Markov process, captures the noise in the receiver signal due to the stochastic nature of chemical reactions and diffusion. We then adopt a maximum a posteriori framework and use Bayesian filtering to derive the optimal demodulator. We use numerical examples to illustrate the properties of this optimal demodulator.

Demodulation of diaphragm based acoustic sensor using Sagnac interferometer with stable phase bias

Abstract: A stable phase demodulation system for diaphragm-based acoustic sensors is reported. The system is based on a modified fiber-optic Sagnac interferometer with a stable quadrature phase bias, which is independent of the parameters of the sensor head. The phase bias is achieved passively by introducing a nonreciprocal frequency shift between the counter-propagating waves, avoiding the use of complicated active servo-control. A 100 nm-thick graphite diaphragm-based acoustic sensor interrogated by the proposed demodulation system demonstrated a minimum detectable pressure level of ~450 µPa/Hz(1/2) and an output signal stability of less than 0.35 dB over an 8-hour period. The system may be useful as a universal phase demodulation unit for diaphragm-based acoustic sensors as well as other sensors operating in a reflection mode.

Method and apparatus for calibration to reduce coupling between signals in a measurement system

Abstract: A method and an apparatus for separating a composite signal into a plurality of signals is described. A signal processor receives a composite signal and separates a composite signal into separate output signals. Feedback from one or more of the output signals is provided to a configuration module that configures the signal processor to improve a quality of the output signals. In one embodiment, calibration data from multiple calibration data sets is used to configure the demodulation of the composite signal into separate output signals.

An 18.7-Gb/s 60-GHz OOK Demodulator in 65-nm CMOS for Wireless Network-on-Chip

Abstract: This paper presents a high-efficiency 60-GHz on-off keying (OOK) demodulator for high-speed short-range wireless communications such as wireless network-on-chip (WiNoC) applications Targeting at data rates of beyond 16 Gb/s, the OOK demodulator consists of a wideband envelope detector (ED) and a single-stage baseband (BB) peaking amplifier Novel dual gain-boosting techniques improve the gain, bandwidth, and out-of-band rejection of the ED In addition, an actively-enhanced tunable inductor (AETI) load in the BB amplifier not only significantly reduces its area overhead, but also provides a tunable peaking level Fabricated in a 65-nm bulk CMOS process, the OOK demodulator consumes only 46 mW from a 1-V supply, and occupies an active area of 0043 mm 2 A maximum data rate of 187 Gb/s with a bit-error rate less than 10 -12 is demonstrated through measurements, which translates to a bit-energy efficiency of 025 pJ/bit

Two-shot fringe pattern phase-amplitude demodulation using Gram-Schmidt orthonormalization with Hilbert-Huang pre-filtering.

Abstract: Gram-Schmidt orthonormalization is a very fast and efficient method for the fringe pattern phase demodulation. It requires only two arbitrarily phase-shifted frames. Images are treated as vectors and upon orthogonal projection of one fringe vector onto another the quadrature fringe pattern pair is obtained. Orthonormalization process is very susceptible, however, to noise, uneven background and amplitude modulation fluctuations. The Hilbert-Huang transform based preprocessing is proposed to enhance fringe pattern phase demodulation by filtering out the spurious noise and background illumination and performing fringe normalization. The Gram-Schmidt orthonormalization process error analysis is provided and its filtering-expanded capabilities are corroborated analyzing DSPI fringes and performing amplitude demodulation of Bessel fringes. Synthetic and experimental fringe pattern analyses presented to validate the proposed technique show that it compares favorably with other pre-filtering schemes, i.e., Gaussian filtering and continuous wavelet transform.

Method and base station for transmitting downstream link data, and method and user device for receiving downstream link data

Abstract: The present invention relates to a method and apparatus which transmit/receive at least one demodulation reference signal by using a CDM group and/or a transmission rank of a user device that have been used to transmit the at least one demodulation reference signal for the user device, an OCC that has been used to spread the demodulation reference signal, etc. Also, the present invention relates to a method and apparatus which change an antenna port for transmitting the demodulation reference signal by using NDI for a disabled transmission block.

Method and apparatus for reducing latency of lte uplink transmissions

Abstract: A method and apparatus reduce latency of Long Term Evolution (LTE) uplink transmissions. A Downlink Control Information (DCI) message can be received in a first subframe. The DCI message can indicate a resource assignment and a modulation and coding scheme and can indicate a plurality of cyclic shifts from which a User Equipment (UE) may select one cyclic shift for transmission in a second subframe for an uplink carrier. A cyclic shift can be selected from the plurality of indicated cyclic shifts based on a selection criterion. A data packet can be transmitted on a Physical Uplink Shared Channel (PUSCH) in a resource indicated by the resource assignment and modulation and coding scheme using a Demodulation Reference Signal (DMRS) based on the selected cyclic shift in the second subframe on the uplink carrier.

Impact of Power Amplifier Nonlinearities in Multi-User Massive MIMO Downlink

Abstract: In this paper, we investigate the impact of power amplifier (PA) nonlinear distortion in pre-coded multi-user large antenna or massive MIMO downlink systems. First, detailed signal and sys-tem models are derived for the received signal at single-antenna user equipment (UE) under channel-aware linear precoding in the base-station combined with behavioral models for the individ-ual PA units, covering both single-carrier and multi-carrier modulation schemes. Based on the derived models, it is shown that the PA induced nonlinear distortion can also combine coherently in the channel, depending on the relative differences between the phase characteristics of the different PA units and the corresponding distortion terms. Furthermore, it is also shown that the impact of nonlinear PAs and the resulting linear and nonlinear multi-user interference, quantified in terms of the received signal-to- interference-plus-noise ratio (SINR), is largely dependent on the effective or observable linear gain in the UE receiver demodulation stage. By observing only the instantaneous direct linear gain, the PA induced nonlinear distortion has a substantial impact on the effective SINR, even if very large number of TX antennas is adopted relative to the number of spatially multiplexed UEs. On the other hand, if the statistically averaged linear gain can be observed, the impact of nonlinear PAs is far less severe. These findings give thus new insight, not only to the core impact of nonlinear PAs in massive MIMO systems but also to the downlink reference signal design, radio frame design and radio resource management in time, in order to facilitate the estimation of the statistically averaged linear gains in the receivers within the scheduled transmission and processing blocks.

Ultra-low latency lte reference signal transmission

Abstract: Various aspects described herein relate to communicating in a wireless network. A resource grant comprising an indicator of whether to transmit a demodulation reference signal (RS) for an uplink control channel or an uplink data channel can be received from a network entity. It can be determined whether to transmit the RS in at least one transmission time interval (TTI) based at least in part on the indicator.

Robust Preamble Design for Synchronization, Signaling Transmission, and Channel Estimation

Abstract: The European second generation digital video broadcasting standard introduces a P1 symbol. This P1 symbol facilitates the coarse synchronization and carries 7-bit transmission parameter signaling (TPS), including the fast Fourier transform size, single-input/single-output and multiple-input/single-output transmission modes, etc. However, this P1 symbol suffers from obvious performance loss over fading channels. In this paper, an improved preamble scheme is proposed, where a pair of optimal ${m}$ sequences are inserted into the frequency domain. One sequence is used for carrier frequency offset (CFO) estimation, and the other carries TPS to inform the receiver about the transmission configuration parameters. Compared with the conventional preamble scheme, the proposed preamble improves CFO estimation performance and the signaling capacity. Meanwhile, without additional overhead, the proposed scheme exploits more active pilots than the conventional schemes. In this way, it can facilitate the channel estimation, improve the frame synchronization accuracy as well as enhance its robustness to frequency selective fading channels.

Implementation of the OFDM Chirp Waveform on MIMO SAR Systems

Abstract: Attention has been devoted to multiple-input multiple-output (MIMO) synthetic aperture radar (SAR) systems in recent years. The applications of MIMO SAR systems, which involve high-resolution wide-swath remote sensing, 3-D imaging, and multibaseline interferometry, are seriously limited by the available sets of orthogonal waveforms. Although orthogonal frequency-division multiplexing (OFDM) chirp waveforms are proposed to avoid intrapulse interferences, this waveform scheme has not been investigated for practical implementation. In this paper, challenges in implementing the OFDM chirp waveforms on practical systems are analyzed and solved. First, the small extra carrier frequency between the mutually orthogonal waveforms, which renders the OFDM chirp waveforms not strictly on common spectral support, is avoided by improving the modulation of the OFDM chirp waveform. Second, the tedious demodulation, which is realized by circular-shift addition in the time domain and subcarrier extraction in the frequency domain, is improved. Third, the radar systematic error and the Doppler shift, which introduce bandwidth leakage and degrade the waveform orthogonality significantly, are compensated. Finally, taking all these challenges into consideration, a novel signal processing algorithm along with a MIMO SAR system model is proposed. Theoretical analysis is validated by simulations and systematic calibration measurements based on a C-band system.

Electro-optic millimeter-wave harmonic downconversion and vector demodulation using cascaded phase modulation and optical filtering.

Abstract: We describe and demonstrate an electro-optic technique to simultaneously downconvert and demodulate vector-modulated millimeter-wave signals. The system uses electro-optic phase modulation and optical filtering to perform harmonic downconversion of the RF signal to an intermediate frequency (IF) or to baseband. We demonstrate downconversion of RF signals between 7 and 70-GHz to IFs below 20-GHz. Furthermore, we show harmonic downconversion and vector demodulation of 2.5-Gb/s QPSK and 5-Gb/s 16-QAM signals at carrier frequencies of 40-GHz to baseband.

Swept optical SSB-SC modulation technique for high-resolution large-dynamic-range static strain measurement using FBG-FP sensors.

Abstract: This Letter presents a static strain demodulation technique for FBG-FP sensors using a suppressed carrier LiNbO3 (LN) optical single sideband (SSB-SC) modulator. A narrow-linewidth tunable laser source is generated by driving the modulator using a linear chirp signal. Then this tunable single-frequency laser is used to interrogate the FBG-FP sensors with the Pound–Drever–Hall (PDH) technique, which is beneficial to eliminate the influence of light intensity fluctuation of the modulator at different tuning frequencies. The static strain is demodulated by calculating the wavelength difference of the PDH signals between the sensing FBG-FP sensor and the reference FBG-FP sensor. As an experimental result using the modulator, the linearity (R2) of the time-frequency response increases from 0.989 to 0.997, and the frequency-swept range (dynamic range) increases from hundreds of MHz to several GHz compared with commercial PZT-tunable lasers. The high-linearity time-wavelength relationship of the modulator is beneficial for improving the strain measurement resolution, as it can solve the problem of the frequency-swept nonlinearity effectively. In the laboratory test, a 0.67 nanostrain static strain resolution, with a 6 GHz dynamic range, is demonstrated.

Range-resolved interferometric signal processing using sinusoidal optical frequency modulation.

Abstract: A novel signal processing technique using sinusoidal optical frequency modulation of an inexpensive continuous-wave laser diode source is proposed that allows highly linear interferometric phase measurements in a simple, self-referencing setup. Here, the use of a smooth window function is key to suppress unwanted signal components in the demodulation process. Signals from several interferometers with unequal optical path differences can be multiplexed, and, in contrast to prior work, the optical path differences are continuously variable, greatly increasing the practicality of the scheme. In this paper, the theory of the technique is presented, an experimental implementation using three multiplexed interferometers is demonstrated, and detailed investigations quantifying issues such as linearity and robustness against instrument drift are performed.

On-chip WDM mode-division multiplexing interconnection with optional demodulation function.

Abstract: We propose and fabricate a wavelength-division-multiplexing (WDM) compatible and multi-functional mode-division-multiplexing (MDM) integrated circuit, which can perform the mode conversion and multiplexing for the incoming multipath WDM signals, avoiding the wavelength conflict. An phase-to-intensity demodulation function can be optionally applied within the circuit while performing the mode multiplexing. For demonstration, 4 × 10 Gb/s non-return-to-zero differential phase shift keying (NRZ-DPSK) signals are successfully processed, with open and clear eye diagrams. Measured bit error ratio (BER) results show less than 1 dB receive sensitivity variation for three modes and four wavelengths with demodulation. In the case without demodulation, the average power penalties at 4 wavelengths are -1.5, -3 and -3.5 dB for TE₀-TE₀, TE₀-TE₁ and TE₀-TE₂ mode conversions, respectively. The proposed flexible scheme can be used at the interface of long-haul and on-chip communication systems.

Iterative Channel Estimation and Impulsive Noise Mitigation Algorithm for OFDM-Based Receivers With Application to Power-Line Communications

Abstract: This paper presents a novel iterative receiver used to mitigate the impact of impulsive noise (IN) on orthogonal frequency-division multiplexing (OFDM)-based baseband power-line communications. An adaptive threshold is mathematically derived for the detection of IN under a desired false alarm probability. This detection mechanism is then used to mitigate IN in two stages. Prior to the OFDM demodulation, a pre-IN mitigation block is used to clip the stronger portions of the IN source. This preprocessing significantly reduces the power of the IN spreading into all subcarriers and, thus, facilitates the detection of residual IN in the second stage. After the OFDM demodulation, the proposed receiver iteratively estimates the channel impulse response and reduces IN sources that were not detected by the pre-IN mitigation block. Post-IN mitigation involves the iterative reconstruction of residual IN, which is then subtracted from the received signal. Denoising is also applied to the estimated channel impulse response. Thus, channel estimation and IN mitigation are mutually beneficial. Simulation results confirm that the proposed iterative receiver significantly improves the mean squared error of the channel estimation as well as bit-error rate.

Low complexity GFDM receiver design: A new approach

Abstract: GFDM (Generalized Frequency Division Multiplexing) is a multicarrier modulation technique that is being proposed as a potential candidate for the fifth generation of wireless communication systems (5G). Due to the fact that GFDM uses only one cyclic prefix (CP) for a group of symbols rather than a CP per symbol and it has a well contained spectral properties, it is more bandwidth efficient than the widely used OFDM modulation. In this paper, we propose novel receiver designs for GFDM by taking advantage of the particular structure in the modulation matrix. A unified receiver structure for matched filter (MF), zero forcing (ZF) and minimum mean square error (MMSE) receivers is derived. Our proposed MF receiver is based on sparsification of the modulation matrix using block discrete Fourier transform (DFT) matrix. The proposed ZF and MMSE receiver algorithms in this paper harness the special block circulant property of the matrices involved in the demodulation stage to reduce the computational cost of the system implementation. In addition, our algorithms do not incur any performance loss as no approximation is involved. The computational costs of our proposed techniques are analyzed in detail and are compared with the existing solutions that are known to have the lowest complexity. It should be highlighted that a substantial computational complexity reduction can be achieved by adopting our techniques.

Low-power, low-rate ultrasonic communications system transmitting axially along a cylindrical pipe using transverse waves

Abstract: Acoustic-electric channels have been used in the recent past to send power and data through thin metallic barriers. Acoustic-electric channels formed along a structure which are highly attenuative and nonreverberant could have potential applications in aerospace, nuclear, and oil industries, among others. This work considers data transmission along the length of a cylindrical pipe both when in air and when filled and immersed in water using shear waves of transverse polarity. To combat the effects of frequency selectivity and to address the available power constraints, a simple modulation scheme using noncoherent demodulation is employed for data transmission: chirp-on-off keying (Chirp-OOK). The wideband nature of the chirp waveform provides resilience against nulls in the channel response while making it possible to implement a simple noncoherent energy detector. Monte Carlo simulation results using measured channel responses suggest that the bit error rate performance of the scheme matches quite closely with the theoretical results. The energy detector performance is independent of the type of the channel used as long as intersymbol-interference is negligible and same received Eb/N0 is maintained. A low-power prototype hardware system was implemented using microcontrollers, commercial ICs, and custom circuits. Successful data transmission was achieved across the 4.8 m length of pipe (in air and water) for a data rate of 100 bps using approximately 5 mW of transmit power.

Demodulation in wireless communications

Abstract: A wireless communication device is configured to perform demodulation of device- to-device (D2D) communication signals or LTE uplink signals in a User Equipment. In a transmitter, demodulation reference signal (DMRS) generation circuitry is provided for selective insertion of DMRS signals in resource elements of resource blocks of the signal for transmission using a pattern of resource elements spanning at least one of the resource blocks such that a minimum temporal spacing between consecutive symbols of the demodulation reference signal pattern is less than one slot. In a receiver the DMRS signals are used to perform channel estimation. A user equipment having the DMRS generation circuitry is provided. A computer program product is also provided. Other embodiments may be described and claimed.

A Modified Demodulation Technique for Single-Phase Grid Voltage Fundamental Parameter Estimation

Abstract: This paper proposes a modified demodulation technique to provide accurate estimation of the single-phase grid voltage fundamental amplitude, frequency, and phase angle under distorted grid conditions. A quadrature oscillator is combined with a demodulation technique for rejecting oscillations at second harmonic generated by the demodulation of the fundamental voltage component; thus, it can provide more accurate estimation, as compared to a conventional one, using same-order and cutoff-frequency-based infinite-impulse-response low-pass filters after the demodulation stage. It also does not require a separate frequency estimation algorithm for adaptive demodulation as the frequency is obtained from the estimated initial phase by using a differentiation operation and an integral controller. The technique is relatively simple and can also reject the negative effects caused by harmonics under a wide range of fundamental frequency variation as specified by the standard requirements. When compared with a quadrature phase-locked loop technique, the proposed one provides improved estimation of the fundamental voltage parameters. The performance of the proposed technique is verified using both simulation and experimental results.