Phase Difference Of Signals Research Articles

Microwave Photonic I/Q Mixer With Phase Shifting Ability

A compact system with multiple signal processing functions is of interest in many applications. The purpose of this paper is to present a microwave photonic structure that is capable of simultaneously realising in-phase/quadrature (I/Q) mixing and phase shifting operations. The multi-function signal processor has a simple structure and can be constructed using off-the-shelf components. It is designed to enable commercial modulator bias controllers to be incorporated into the system to provide accurate phase shift and to improve system stability. Non-ideal effects in the system that cause deviation in the two output IF signal phase difference from 90° can be mitigated by adjusting a modulator bias voltage. The multi-function signal processor is theoretically analysed and experimentally demonstrated. Its performance including two output IF signals with a quadrature phase difference, wideband operation, continuous 0° to 360° IF signal phase shift and long-term stable operation are verified experimentally.

Methods to Increase the Accuracy of Calculation of the Phase Difference of Signals of an Interferometric Side-Scan Sonar

Methods to Increase the Accuracy of Calculation of the Phase Difference of Signals of an Interferometric Side-Scan Sonar

A half-bridge IGBT drive and protection circuit in dielectric barrier discharge power supply

PurposeThis paper aims to improve the general circuit of driving and protection based on insulated gate bipolar transistor (IGBT) in dielectric barrier discharge power supply by designing a novel half-bridge inverter circuit with discrete components.Design/methodology/approachWith one SG3524 chip, the structure based on discrete components is used to design the IGBT drive circuit. The driving waveform is isolated and sent out by photo-coupler 6N137. The protection circuit is realized by Hall sensor directly detecting the main circuit current, supplemented by a few components, including diodes, resistors, capacitors and triodes. It improves the reliability of the protection circuit.FindingsIn the driving circuit, the phase difference of signals from two channels are 180°. Moreover, when the duty cycle is set at 40%, it can ensure sufficient pulse width modulation response time. In the protection circuit, when over-current occurs, an intermittent output signal is automatically sent out. Furthermore, the over-current response time can be controlled independently. The peak voltage can be adjusted continuously from 0 to 30 kV with its frequency from 8 to 25 kHz and the power output up to 150 W.Originality/valueThe novel circuit of driving and protection makes not only its structure simpler and easier to be realized but also key parameters, such as frequency, the duty cycle and the driving voltage, continuously adjustable. Moreover, the power supply is suitable for other discharges such as corona discharge and jet discharge.

RTK Kinematic Positioning Accuracy with Double Phase Difference of SIS GNSS Signals

The article presents results of verification of the kinematic measurements usefulness for precise real-time positioning RTK in the local reference system. These measurements allow for continuous RTK measurements in the event of temporary interruptions in radio or internet connections, which are the main reason for interruptions in RTK kinematic measurements and cause a decrease in the reliability and efficiency of this positioning method. Short interruptions communication are allowed during the loss of the key correction stream from the local RTK support network, so the global corrections obtained from the geostationary satellite are used. The aim of the article was to analyze the accuracy of measuring the position of moving objects. Practical conclusions were formulated according to the research subject, the presented mathematical models, the experiment and the analysis of the obtained results.

Localization and Tracking of an Indoor Autonomous Vehicle Based on the Phase Difference of Passive UHF RFID Signals.

State-of-the-art radio frequency identification (RFID)-based indoor autonomous vehicles localization methods are mostly based on received signal strength indicator (RSSI) measurements. However, the accuracy of these methods is not high enough for real-world scenarios. To overcome this problem, a novel dual-frequency phase difference of arrival (PDOA) ranging-based indoor autonomous vehicle localization and tracking scheme was developed. Firstly, the method gets the distance between the RFID reader and the tag by dual-frequency PDOA ranging. Then, a maximum likelihood estimation and semi-definite programming (SDP)-based localization algorithm is utilized to calculate the position of the autonomous vehicles, which can mitigate the multipath ranging error and obtain a more accurate positioning result. Finally, vehicle traveling information and the position achieved by RFID localization are fused with a Kalman filter (KF). The proposed method can work in a low-density tag deployment environment. Simulation experiment results showed that the proposed vehicle localization and tracking method achieves centimeter-level mean tracking accuracy.

Absolutely Consistent Fiber-Optic Phase Synchronization Based On Fixed-Phase-Reference Optical Active Compensation

An absolutely consistent fiber-optic phase synchronization scheme based on fixed-phase-reference optical active compensation is proposed. By measuring the time interval of time pulse and the phase difference of frequency signal, and then using the optical delay line to compensate the phase change in real time according to a fixed phase reference, the phase period ambiguity and the phase-lock control initial randomness are eliminated, realizing a stable and repeatable fixed phase difference between different sites. Then the phase synchronization performances of stability and absolute consistence have been demonstrated through experiments in different scenarios. The phase difference fluctuation within 10000 s is only ±0.0006 rad, showing an ultra-high stability. Under the total of 5 different operations, including the signal source restart, system restart, adding 20 m additional fiber, adding 1 km additional fiber, and adding 2 km additional fiber, the maximum inconsistency of the mean phase difference is about 1% of one full cycle. The proposed and verified absolutely consistent phase synchronization method can well maintain the coherence in transferring frequency signal, having important application prospects in radar network and other time-frequency-phase synchronization-based coherent detection.

Photonics-Based RF Signal Phase Detector With Wide Operating Frequency Range and High Resolution

A new topology that generates a DC voltage whose value is depending on the phase difference of two input RF signals is presented. It is implemented by the mixer concept. With the use of microwave photonics, the mixer-based phase detector can be operated over a very wide frequency range. It also has the advantages of high phase detection resolution, small phase detection error, and small DC offset and phase offset. The phase detector can be constructed using off-the-shelf components including a single integrated optical modulator and a low-speed balanced detector. Measured results on the phase detector demonstrate a 0° to 180° RF signal phase difference detection range for 3.5 GHz to 18 GHz input RF signal frequencies, less than ±3° phase detection error and 2° phase detection resolution.

Design of compact wideband Rotman lens for 5G multibeam application

In this paper, a compact broadband Rotman lens beamforming network based on equal optical path difference is proposed. The beamforming network is intended for applications in a multi-beam antenna array of 5G millimeter-wave (mm-wave) communication. Firstly, the theoretical design of the Rotman lens is introduced in detail. A power divider is used to replace the standard single-port feeding mode to generate a high-directional beam, reducing the scattering of the lens’ internal energy and the energy loss at adjacent ports. The Chebyshev multi-stub matching converter is used to optimize the original tapered array output port. To ensure a wide frequency band, the original matching port size is reduced, and the overall size of the lens is reduced by 20%. Measurement results of the improved model, show that the working frequency band of the lens is 16.5−33.8 GHz, of which S11 is better than 15 dB at 17.2−32.0 GHz, and the scanning angle is ±30°. The lens has a simple and compact structure, can effectively provide a stable phase difference signal for adjacent array elements, and achieve the goal of 5G millimeter-wave array multi-beam.

Method for Determining the Fractional Part of the Cycle of the Carrier Frequency of the Navigation Signal of the GNSS Signal Simulator

The problem of calibrating a simulator of the navigation signals of global navigation satellite systems in order to ensure the unity of measurements of coordinate and time facilities was examined. A method is provided of determining, with the use of an oscilloscope, a fractional part of a carrier frequency cycle in the radio-frequency circuit of the simulator, and of estimating the mean reference deviation of the error of simulator generation of a pseudo-distance on the carrier-phase. The essence of the method consists in determining the phase difference of two signals. Depending on the type of problem, this method of calibration can be used with different input data: for absolute calibration of the simulator with one radio-frequency output: the phase difference of the navigation signal generated by the simulator, and the reference harmonic signal; for relative calibration of the simulator with two or more radio frequency outputs: the phase difference between navigation signals generated by the simulator from the different radio-frequency outputs. The application is shown of the absolute calibration of the simulator by the carrier-phase for the solution of a problem of calibrating users’ navigation equipment by the carrier-phase, which will substantially simplify the implementation of the promising Integer-PPP technology. The use of the relative calibration of the simulator, in order to determine the precise characteristics of goniometric navigation equipment for its development and tests, is presented.

Improved Estimation of Sway-Angle for Overhead Crane based on Phase Difference of Acoustic Signals in Frequency Domain

Improved Estimation of Sway-Angle for Overhead Crane based on Phase Difference of Acoustic Signals in Frequency Domain

Study of the characteristics of a radio photon device for determining the phase difference of a radar signals

The paper considers the problem of accurate calculation of the phase of the radar signal in relation to the receiving phased antenna arrays. Methods for determining the phase difference based on a comparison of the received signal with the local oscillator signal are listed, as well as a method based on the use of a radio-photon analog-to-digital converter for the output signal of the receiving phased antenna array. Their disadvantages are indicated. A method and a radio photon device are proposed that are devoid of these disadvantages. The method allows you to calculate the phase difference of the radar signal at the output of the electro-optical modulator and the output signal of the photodetector, taking into account the known values of the amplitudes and phase difference of the microwave signals at the input of the receiving elements of the phased antenna array. The radio-photon device allows you to implement this method and, unlike the known analogues, is based on the use of two parallel-connected electro-optical modulators constructed according to the scheme of the Mach-Zehnder interferometer. It is shown that the proposed radio photon device provides a higher accuracy of determining the phase of the radar signal in comparison with existing analogues. At the end of the work, an analysis of the results of experimental studies using the proposed method and a radio photon device is presented. According to the results of the experiment, it was found that the phase and phase differences vary linearly, and their maximum reaches π. In addition, the square of the amplitude of the optical signal at the input of the photon-electronic unit is proportional to the phase difference and inversely proportional to the ratio of the amplitudes of the output signals of the adjacent receiving elements of the phased antenna arrays.

Deep Convolutional Neural Network for Passive RFID Tag Localization Via Joint RSSI and PDOA Fingerprint Features

Radio-frequency identification (RFID) localization has drawn much attention with the emergence of the Internet of Things (IoT). Deep learning with applications to RFID localization owns a lot of advantages. In this paper, we present a deep convolutional neural network (CNN)-based approach for passive RFID tag localization exploiting joint fingerprint features of the received signal strength indication (RSSI) and phase difference of arrival (PDOA). First, the RSSI and PDOA data are extracted from the received signals of RFID readers. Then, a CNN with three convolution layers and pooling layers is design, in which the normalized RSSI and PDOA data are formed into images as its input to train the weights in the offline stage. In the online stage, the RSSI and PDOA data of test tags are collect and then the positions of unknown tags is predected based on the designed CNN. In the simulations, the accuracy of the proposed approach is compared with several fingerprinting-based schemes such as LANDMARC, weighted K-nearest neighbor (WKNN) and deep neural network (DNN), and the impact of different fingerprint data sets and noise variances on the positioning accuracy is analyzed. Experiments show that the proposed approach can locate multiple tags with high accuracy and stability in complex indoor environment, and outperforms other existing schemes.

Method for increasing noise resistance of radar sensors with frequency selection

The description of a new method of signal generation and processing which provides an increase in the noise immunity of radar sensors (RS) with frequency switching (FS) radiation is presented. The principle of method is in the use of a set of time intervals when measuring the phase difference of signals at different radiation frequencies and, accordingly, a set of the Doppler frequency values in the signal spectrum when determining the average value of the Doppler frequency, as well as the use of forward and reverse IF sequences. This method allows averaging the results of calculating individual implementations and, thereby, increase the accuracy of determining the target speed and distance to it. At the same time, the stability of the RS with FS also increases to the effects of signals from third-party radio sources and interference from the underlying surface. The results of experimental studies of the method are obtained on the example of the autodyne RS with the 8-mm frequency range, made on the basis of the Gann diode generator with frequency control by varicap. The method may be used in on-board (for example, automotive) radar sensors designed to detect moving targets, measure the distance to them, as well as determine the speed and direction of movement.

Sea Surface Imaging with a Shortened Delayed-Dechirp Process of Airborne FMCW SAR for Ocean Monitoring on Emergency

A sea surface imaging technique for an emergency response using a ready-made frequency modulated continuous wave–synthetic aperture radar (FMCW SAR) system and its experimental results are described in this paper. The optimal range of radiowave incidence angle for sea surface imaging was analyzed by a theoretical scattering model and measurement data, and it was properly applied to the FMCW SAR system by readjusting the delayed-dechirp process. Raw data acquired through flight experiments were reconstructed to SAR image by the range-doppler algorithm. To verify the performance of the reconstructed sea surface image, dual-channel images collected by the configuration of the along-track interferometry were used, and then performance indicators such as signal attenuation, coherence, and phase difference were analyzed. Through this experimental study, it was confirmed that the ready-made FMCW SAR system without a function of the incident angle control can also conduct limited missions for maritime observation. It is possible to be an alternative resource for emergency response, in which the cases are requiring urgent maritime disaster detection and analysis.

A Simple Scheme for Photonic Generation of Microwave Waveforms Using a Dual-drive Mach–Zehnder Modulator

In this paper, a novel photonic scheme for the generation of square and triangular waveforms is proposed and experimentally demonstrated by using a dual-drive Mach–Zehnder modulator (DDMZM) without any optical signal processing. By properly setting the modulation index of the DDMZM, the square and triangular microwave waveforms could be easily achieved in conjunction with a 90° hybrid coupler. Furthermore, the modulation index of the DDMZM could be tuned for a low radio frequency (RF) signal power requirement by tuning the phase difference of the RF signals applied to the two arms of the DDMZM. The proposed scheme for the photonic generation of microwave waveforms is theoretically analyzed and experimentally demonstrated. The periodical triangular and square waveforms with repetition rates of 5 GHz, 8 GHz, and 10 GHz are successfully obtained. The root-mean-square errors between the generated and theoretical triangular and square waveforms with a repetition of 5 GHz are 0.042 and 0.053, respectively.

Research on modulation recognition of Communication Radar Based on spread spectrum technology

Aiming at the problem that the traditional radar signal recognition method needs to be completed under the noiseless condition, which leads to the low recognition accuracy of low SNR signal, the modulation recognition method of communication radar signal based on spread spectrum technology is studied. The phase difference and instantaneous frequency characteristics of communication radar signal are extracted after the spread spectrum processing of communication radar signal with direct sequence spread spectrum. The training sample is used to train PNN neural network, and the modulation recognition of communication radar signal is completed. Simulation experiments under different parameters show that the recognition method based on spread spectrum technology has an effective recognition rate higher than 90% for low SNR signal, which is superior to the traditional method and can be applied in practice.

Terahertz Spoof Surface Plasmonic Logic Gates.

SummaryLogic gates are important components in integrated photonic circuitry. Here, a series of logic gates to achieve fundamental logic operations based on linear interference in spoof surface plasmon polariton waveguides are demonstrated at terahertz frequencies. A metasurface-based plasmonic source is adopted to couple free-space terahertz radiation into surface waves, followed by a funnel-shaped metasurface to efficiently couple the surface waves to the waveguides built on a domino structure. A single Mach-Zehnder waveguide interferometer can work as logic gates for four logic functions: AND, NOT, OR, and XOR. By cascading two such interferometers, NAND and NOR operations can also be achieved. Experimental investigations are supported by numerical simulations, and good agreement is obtained. The logic gates have compact sizes and high intensity contrasts for the output “1” and “0” states. More complicated functions can be envisioned and will be of great value for future terahertz integrated computing.

Viterbi Decoder to Resolve Angular Ambiguity in Digital Beamforming With Widely Spaced Radar Front Ends

This article introduces a precise radar-based direction-of-arrival measurement system using a Viterbi decoder. Based on the frequency-modulated continuous-wave principle, the presented method employs both the frequency difference and the round-trip phase difference of the radio wave signal impinging at two widely spaced receiving antennas, thereby accomplishing highly accurate and absolute measurements of the direction-of-arrival. In order to resolve angular ambiguity, which is inherently caused by the $2 \pi $ ambiguity in phase measurement, the proposed Viterbi decoder determines the most likely sequence of direction-of-arrivals of the impinging radio wave signals. For proof of concept, experiments based on a 77 GHz radar unit equipped with one transmitting and two widely spaced receiving antennas were carried out. The measurement results show that angular ambiguity can be resolved by the presented Viterbi decoder since absolute, accurate, and repeatable direction-of-arrival estimates were obtained, even for receiver antenna spacings significantly larger than the signal wavelength.

On the Transient Behavior of Single-Loop Optoelectronic Oscillators Under RF Injection-Locking

A study on the transient behavior of a single-loop optoelectronic oscillator (OEO) under a single sinusoidal radio frequency (RF) signal injection is presented. Considering only the phase perturbation imposed by the external RF signal, the phase-dynamic equation is solved to analyze the frequency settling behavior of the loop. A closed form expression for the required time of an OEO under RF injection-locking, reaching the steady state condition, is derived in terms of the initial phase difference, beat frequency and injection signal strength. The phase modulated signal, which is responsible for the perturbation of the free running oscillation, is expanded in a Fourier series and the expression for the output RF spectrum of the injection pulled OEO is derived. The injection-pulling dynamics approach is used to describe the phase noise of the OEO and also, the influence of the phase settling time constant on the phase noise of the injection-locked OEO is studied. The experimental results corroborating the theoretical findings are given.

Effect of Decorrelation Factors on the Error in Measuring the Signal Phase Difference with Interferometric Systems

Based on the general model of signals scattered by the rough surface of the seabed, relations are developed for estimating the errors of measurement by the interferometric side-scan sonar (ISSS) of the arrival angles of echo signals caused by the decorrelation of the probing signals with a large base in the receiving channels due to the spatial separation of the antennas. The obtained relations allow us to adjust the signal processing algorithms received by the multiantenna interferometer to reduce the influence of additive noise on the accuracy of the measurements of the angles of arrival of echo signals.