Digital Phase Discriminator Research Articles

Microwave frequency transfer over 3000-km fiber based on optical frequency combs and active noise cancellation

Time and frequency transfer plays an important role in the fields of navigation and positioning, remote sensing, and fundamental physics. The performance of long-haul frequency transfer is ultimately limited by accumulated phase and amplitude noise in fiber propagation. In this work we overcome these limitations and demonstrate a frequency transfer system over 3000 km of indoor spooled fibers via repetition-frequency-locked frequency combs, which benefit from the extremely high signal-to-noise ratio. With the help of the digital phase discrimination and compensation method and active power stabilization, the dramatic phase and amplitude variations are sufficiently suppressed, respectively, which results in the residual instability 7.5×10−14 at 1 s and 1.0×10−16 at 10 000 s, without optical-electrical-optical recovery by the regeneration system. Our results mark a breakthrough in building large-scale, high-precision synchronization networks. Published by the American Physical Society 2024

Single-Ended Eddy Current Micro-Displacement Sensor with High Precision Based on Temperature Compensation.

To measure the micro-displacement reliably with high precision, a single-ended eddy current sensor based on temperature compensation was studied in detail. At first, the principle of the eddy current sensor was introduced, and the manufacturing method of the probe was given. The overall design plan for the processing circuit was induced by analyzing the characteristics of the probe output signal. The variation in the probe output signal was converted to pulses with different widths, and then it was introduced to the digital phase discriminator along with a reference signal. The output from the digital phase discriminator was processed by a low-pass filter to obtain the DC component. At last, the signal was amplified and compensated to reduce the influence of temperature. The selection criteria of the frequency of the exciting signal and the design of the signal conditioning circuit were described in detail, as well as the design of the temperature-compensating circuit based on the digital potentiometer with an embedded temperature sensor. Finally, an experimental setup was constructed to test the sensor, and the results were given. The results show that nonlinearity exists in the single-ended eddy current sensor with a large range. When the range is 500 μm, the resolution can reach 46 nm, and the repeatability error is ±0.70% FR. Within the temperature range from +2 °C to +58 °C, the voltage fluctuation in the sensor is reduced to 44 mV after temperature compensation compared to the value of 586 mV before compensation. The proposed plan is verified to be feasible, and the measuring range, precision, and target material should be considered in real-world applications.

High-Precision Pseudo-Noise Ranging Based on BOC Signal: Zero-Bias Mitigation Methods

In high precision applications based on binary subcarrier offset (BOC) signals, zero-bias of the digital discriminator is an error of importance. Unlike the thermal noise error, zero-bias is a fixed deviation that is challenging to eliminate by filtering in the time domain. In this paper, a statistical error analysis model for the zero-bias of BOC signal’s digital phase discriminator is established. The evaluation of the zero-bias is inseparable from the spreading code sequence and the initial phase of the signal through defining the concept of statistics maximum and statistics standard deviation. Based on the zero-bias statistical error analysis model, two receiver parameter design methods, namely, the baseband signal sampling frequency and the early-late correlation interval, are proposed. The performance of the algorithm is simulated on account of the limited bandwidth, Doppler frequency offset and thermal noise. The simulation results prove that the proposed algorithm can suppress the standard deviation of zero-bias within one phase resolution, which contributes substantially to the improvement of the measurement accuracy of pseudo-noise ranging.

Zero‐bias mitigation method based on optimal correlation interval for digital code phase discriminator

In time synchronisation systems, the code phase of the spread spectrum signal is an important characteristic that can provide users with high-precision and unambiguous observation results. However, digital code phase discriminators have limited sampling frequencies that distort the signal correlation peak and generates a zero-bias code-phase estimate. In this Letter, the authors evaluate and analyse the zero-phase deviations of digital code phases. An optimal correlation interval design method, based on a code phase discriminator that can effectively suppress the zero-crossing deviation, is also proposed. The simulation results show that the proposed algorithm can reduce the deviation of 96.5% and effectively improve the measurement accuracy of the code phase.

多普勒加速度测量的数字相关鉴相算法

多普勒加速度测量的数字相关鉴相算法

PERFORMANCE-OPTIMAL PHASE-LOCKED SYSTEM FOR DEVICE OF SYNCHRONIZATION AND FORMATION OF THE EXACT TIME SIGNALS

Background. The generating reference time signals problem to meet the all consumers’ requirements for time and frequency information is targeted on researching the time scale IP-technologies transmission systems quality improvement and optimizing the synchronization devices self-tuning, as one of the most common systems’ elements in a today’s world. Objective. The aim of the paper is the phase locked loop (PLL) system performance optimization of the device for the exact time signal synchronization and formation. Methods. The linearized model construction of a closed automatic control system for a synchronization device, obtaining performance optimal control law in an analytical form and its implementation in the synchronization device PLL system using an adaptive digital phase discriminator. Results. The performance optimal control law in synchronization PLL device using an adaptive digital phase discriminator was practically implemented. Conclusions. The synchronization information transmission over existing IP networks based on the PTP protocol allows spreading the time scale with an accuracy of hundreds nanoseconds in real networks. Improving the exact time signals formation quality causes the optimizing performance need for the PLL synchronization devices. The adaptive digital phase discriminator use is protected by the Ukraine invention patent and provides the ability to control the phase discriminator (PD) characteristic shape for the transient process duration in PLL system. Keywords: standard; exact time; self-tuning; optimization; synchronization; control system; IP-technologies.

A Rotation-Aided Arctangent Phase Discriminator With One-Bit Quantization

In this letter, we present a rotation-aided arctangent phase discriminator (RaAPD) with one-bit analog-to-digital conversion. Different from the existing digital phase discriminator (DPD) and noise-balanced digital phase discriminator (NB-DPD), the proposed RaAPD can achieve higher accuracy and better noise robust features through utilizing an extra rotation channel in the arctangent phase discriminator (APD). Experimental results show that RaAPD achieves 98.3%, 79.3%, and 79.4% reduction in terms of the average root-mean-square error of phase estimation with the signal noise ratio range [−20 dB, 20 dB] and a 16.384-MHz sampling frequency comparing to DPD, NB-DPD, and APD, respectively.

1-Bit High Accuracy Carrier Phase Discriminators

Asymptotic derivation of traditional 1-bit arctangent phase discriminator (APD) is derived, even though neighboring quantized samples are dependent. The results reveal that high accuracy can be achieved by an APD in low signal-to-noise ratio (SNR) applications using sufficient samples. For high- SNR applications a novel phase discriminator called noise-balanced digital phase discriminator (NB-DPD), which has a complementary asymptotic performance of APD, is proposed to achieve high accuracy. The threshold SNR 2.6 dB that is suggested to identify either APD or NB-DPD is adopted in a specific application. Finally the sampling, quantization, and environmental noise effects on convergence of the asymptotic performance are discussed, and the simulations are provided to verify the analytical results.

The Research of Phase Method of Laser Ranging Measurement System

The phase method of laser ranging modulates laser by using a continuous wave, calculating the time interval indirectly through the phase variation of the modulation wave when it propagates between the measured targets, and make out the measured distance. This paper uses the principle of phase method of laser ranging, proposes the overall design scheme of phase method of laser measurement system which achieves the distance measurement by using methods of the difference frequency measurement and digital phase discrimination as well as the microcontroller. It also analysis the system possible errors from many aspects, puts forward the appropriate measures to improve the accuracy of the measurement.

SNR-Aided Accurate Phase Estimation in 1-Bit Software-Defined Receiver

This work investigates the high-accuracy phase discriminator in 1-bit software-defined receiver (SDR) for three signal-to-noise ratio (SNR) ranges: low SNR, high SNR and moderate SNR. Unlike traditional approaches, our approach first distinguishes which SNR range an application falls into, and this SNR information is then utilized to select a proper phase discriminator to achieve high accuracy. For low-SNR applications, traditional arctangent phase discriminator (APD) is adopted and the analysis of asymptotic performance is derived. For high-SNR applications, the noise-balanced digital phase discriminator (NB-DPD) is adopted to improve accuracy [1]. Between them, for moderate-SNR applications, a novel SNR-aided phase discriminator (SNRaPD) is proposed. The analytical and simulation results verify the superiority of the proposed approach for applications in different SNR ranges. The determination of moderate SNR range is critical and discussed finally.

Free-axis RLC Measurement Research Based on Fully Digital Phase Discrimination

Free-axis RLC Measurement Research Based on Fully Digital Phase Discrimination

High-Accuracy Carrier Phase Discriminator in One-Bit Quantized Software-Defined Receivers

In this letter, a novel phase discriminator called digital phase discriminator (DPD) is proposed for 1-bit analog-to-digital-conversion (ADC) software-defined receivers. Using fewer computations, the DPD achieves higher accuracy than that of the typical arctangent phase discriminator (APD). The improvement is up to several orders when the sampling frequency keeps increasing since the accuracy of APD is bounded mainly due to quantization loss. Finally, the simulation results demonstrate the superiority of the proposed approach and the critical uniformity condition is verified.

Successive approximation tuning of monolithic continuous-time filters

The Letter proposes the tuning of monolithic continuous-time filters employing a successive approximation algorithm to control the automatic adjustment of a two-integrator loop to its nominal resonant frequency depending on an error signal provided by a digital phase discriminator. This achieves high-precision tunability which does not depend on tight circuit matching.