Leveraging ROTI map derived from Indonesian GNSS receiver network for advancing study of Equatorial Plasma Bubble in Southeast/East Asia

This paper highlights the crucial role of Indonesia’s GNSS receiver network in advancing Equatorial Plasma Bubble(EPB)studies in Southeast and East Asia,as ionospheric irregularities within EPB can disrupt GNSS signals and degrade positioning accuracy.Managed by the Indonesian Geospatial Information Agency(BIG),the Indonesia Continuously Operating Reference Station(Ina-CORS)network comprises over 300 GNSS receivers spanning equatorial to southern low-latitude regions.Ina-CORS is uniquely situated to monitor EPB generation,zonal drift,and dissipation across Southeast Asia.We provide a practical tool for EPB research,by sharing two-dimensional rate of Total Electron Content(TEC)change index(ROTI)derived from this network.We generate ROTI maps with a 10-minute resolution,and samples from May 2024 are publicly available for further scientific research.Two preliminary findings from the ROTI maps of Ina-CORS are noteworthy.First,the Ina-CORS ROTI maps reveal that the irregularities within a broader EPB structure persist longer,increasing the potential for these irregularities to migrate farther eastward.Second,we demonstrate that combined ROTI maps from Ina-CORS and GNSS receivers in East Asia and Australia can be used to monitor the development of ionospheric irregularities in Southeast and East Asia.We have demonstrated the combined ROTI maps to capture the development of ionospheric irregularities in the Southeast/East Asian sector during the G5 Geomagnetic Storm on May 11,2024.We observed simultaneous ionospheric irregularities in Japan and Australia,respectively propagating northwestward and southwestward,before midnight,whereas Southeast Asia’s equatorial and low-latitude regions exhibited irregularities post-midnight.By sharing ROTI maps from Indonesia and integrating them with regional GNSS networks,researchers can conduct comprehensive EPB studies,enhancing the understanding of EPB behavior across Southeast and East Asia and contributing significantly to ionospheric research.

Optimization strategies for operational parameters of Rydberg atom-based amplitude modulation receiver

The Rydberg atom-based receiver, as a novel type of antenna, demonstrates broad application prospects in the field of microwave communications. However, since Rydberg atomic receivers are nonlinear systems, mismatches between the parameters of the received amplitude modulation(AM) signals and the system's linear workspace and demodulation operating points can cause severe distortion in the demodulated signals. To address this, the article proposes a method for determining the operational parameters based on the mean square error(MSE) and total harmonic distortion(THD) assessments and presents strategies for optimizing the system's operational parameters focusing on linear response characteristics(LRC) and linear dynamic range(LDR). Specifically, we employ a method that minimizes the MSE to define the system's linear workspace, thereby ensuring the system has a good LRC while maximizing the LDR. To ensure that the signal always operates within the linear workspace, an appropriate carrier amplitude is set as the demodulation operating point. By calculating the THD at different operating points, the LRC performance within different regions of the linear workspace is evaluated, and corresponding optimization strategies based on the range of signal strengths are proposed. Moreover, to more accurately restore the baseband signal, we establish a mapping relationship between the carrier Rabi frequency and the transmitted power of the probe light, and optimize the slope of the linear demodulation function to reduce the MSE to less than 0.8×10^(-4). Finally, based on these methods for determining the operational parameters, we explore the effects of different laser Rabi frequencies on the system performance, and provide optimization recommendations. This research provides robust support for the design of high-performance Rydberg atom-based AM receivers.

Interference Cancellation Based Neural Receiver for Superimposed Pilot in Multi-Layer Transmission

In this paper,an interference cancellation based neural receiver for superimposed pilot(SIP)in multi-layer transmission is proposed,where the data and pilot are non-orthogonally superimposed in the same time-frequency resource.Specifically,to deal with the intra-layer and inter-layer interference of SIP under multi-layer transmission,the interference cancellation with superimposed symbol aided channel estimation is leveraged in the neural receiver,accompanied by the pre-design of pilot code-division orthogonal mechanism at transmitter.In addition,to address the complexity issue for inter-vendor collaboration and the generalization problem in practical deployments,respectively,this paper also provides a fixed SIP(F-SIP)design based on constant pilot power ratio and scalable mechanisms for different modulation and coding schemes(MCSs)and transmission layers.Simulation results demonstrate the superiority of the proposed schemes on the performance of block error rate and throughput compared with existing counterparts.

A 10Gb/s GaAs PHEMT High Gain Preamplifier for Optical Receivers

A high gain cascade connected preamplifier for optical receivers is developed with 0.5μm GaAs PHEMT technology from the Nanjing Electronic Devices Institute. To begin with, the transimpedance amplifier has a -3dB bandwidth of 10GHz, with a small signal gain of around 9dB. The post-stage distributed amplifier （DA） has a -3dB bandwidth of close to 20GHz,with a small signal gain of around 12dB. As a whole,the cascade preamplifier has a measured small signal gain of 21.3dB and a transimpedance of 55.3dBΩ in a 50Ω system. With a higher signal-to-noise ratio than that of the TIA and a markedly improved waveform distortion compared with that of the DA, the measured output eye diagram for 10Gb/s NRZ pseudorandom binary sequence is clear and symmetric.

A 12-Channel,30Gb/s,0.18μm CMOS Front-End Amplifier for Parallel Optic-Fiber Receivers

This paper presents a 12-channel,30Gb/s front-end amplifier realized in standard 0.18μm CMOS technology for parallel optlc-fiber receivers. In order to overcome the problem of inadequate bandwidth caused by the large parasitical capacitor of CMOS photo-detectors,a regulated-cascode structure and noise optimization are used in the design of the transimpedance amplifier. The experimental results indicate that, with a parasitical capacitance of 2pF,a single channel is able to work at bite rates of up to 2.5Gb/s,and a clear eye diagram is obtained with a 0. 8mVpp input. Furthermore, an isolation structure combined with a p^＋ guard.ring （PGR）, an n^＋ guard-ring （NGR）,and a deep-n-well （DNW） for parallel amplifier is also presented. Taking this combined structure, the crosstalk and the substrate noise coupling have been effectively reduced. Compared with the isolation of PGR or PGR ＋ NGR,the measured results show that the isolation degree of this structure is improved by 29.2 and 8. ldB at 1GHz,and by 8. 1 and 2. 5dB at 2GHz,respectively. With a 1.8V supply,each channel of the front-end amplifier consumes a DC power of 85mW,and the total power consumption of 12 channels is about 1W.

A 0.5mV High Sensitivity 200Mbps CMOS Limiting Amplifier with RSSI for Optical Receivers

A 0. 5mV high sensitivity,200Mbps CMOS limiting amplifier （LA） with 72dB ultra wide dynamic range is described. A novel active DC offset cancellation loop is elaborately analyzed and designed to achieve this performance. Using a signal path, a received signal strength indicator （RSSI）, based on the piecewise-linear approximation, is realized with a ± 2dB logarithmic accuracy in a 60dB indicating range. The architecture of the LA and RSSI employed is determined by the optimal sensitivity and RSSI accuracy for a specified speed, gain, and power consumption. It consumes 60mW from a single 5V supply. The active area is 1.05mm^2 using standard 5V 0.6μm CMOS technology.

Iterative receivers for SFBC-OFDM systems with adaptive training scheme

This paper considers the design of iterative receivers for space-frequencyblock-coded orthogonal frequency division multiplexing (SFBC-OFDM) systems in unknown wirelessdispersive fading channels. An iterative joint channel estimation and symbol detection algorithm isderived. In the algorithm, the channel estimator performs alternately in two modes. During thetraining mode, the channel state information (CSI) is obtained by a discrete-Fourier-transform-basedchannel estimator and the noise variance and covariance matrix of the channel response is estimatedby the proposed method. In the data transmission mode, the CSI and transmitted data is obtainediteratively. In order to suppress the error propagation caused by a random error in identifyingsymbols, a simple error propagation detection criterion is proposed and an adaptive training schemeis applied to suppress the error propagation. Both theoretical analysis and simulation results showthat this algorithm gives better bit-error-rate performance and saves the overhead of OFDM systems.

An Implementation of a CMOS Down-Conversion Mixer for GSM1900 Receivers

A 1.9GHz down-conversion CMOS mixer with a novel folded Gilbert cell,intended for use in GSM1900 （PCS1900） low-IF receivers,is fabricated in a RF 0.18μm CMOS process. The prototype demonstrates good performance at an intermediate frequency of 100kHz. It achieves a conversion gain of 6dB, SSB noise figure of 18. 5dB （1MHz IF） ,and IIP3 11.5dBm while consuming a 7mA current from a 3.3V power supply.

A Low-Voltage,Low-Power CMOS High Dynamic Range dB-Linear VGA for Super Heterodyne Receivers

This paper presents a low-voltage low-power variable gain amplifier,which is applied in the automatic gain control loop of a super heterodyne receiver. Six stages are cascaded to provide an 81dB digitally controlled gain range in a 3dB step. The gain step error is less than 0.5dB. It operates at an intermediate frequency of 300kHz, and the power consumption is 1.35mW from a 1.8V supply. The prototype chip is implemented in a TSMC＇s 0.18μm 1P6M CMOS process and occupies approximately 0.24mm^2 . It is very suitable for portable wire- less communication systems. The measurement results agree well with the system requirements.

The usability of GNSS mass-market receivers for cadastral surveys considering RTK and NRTK techniques

Nowadays many positioning techniques and methods are applied to the cadastral surveys. Starting from last decade, GPS/GNSS positioning had become one of the most used methodology thanks to the rapid development of satellite-based positioning and to the appearance of GNSS mass-market receivers and antennas. Methods based on these instruments are more affordable than the conventional ones even if their use for precise positioning is not so intuitive. This study is aimed to evaluate the use of singlefrequency GPS/GNSS mass-market receivers for cadastral surveys, considering both single-base RealTime Kinematic(RTK) and Network Real-Time Kinematic(NRTK) methodologies. Furthermore, a particular tool for predicting and estimating the occurrence of false fix of the phase ambiguities has been considered, in order to improve the accuracy and precision of the solutions. Considering the single-base positioning, the research results showed the difference of a few centimetres between the reference coordinates and the estimated ones if the distance between master and rover is less than 3 km, while considering the network positioning and the Virtual Reference Station correction, the difference are about a couple of centimetres for East and North component, and about 5 cm for the Up.

Optimization of the carrier tracking loop for GPS high dynamic receivers

A carrier tracking loop which can adjust the loop parameters adaptively is proposed for high dynamic application. Three modules, called the α-β-γT filter model, adaptive loop structure mod- el and adaptive loop bandwidth model respectively, are added in the presented tracking loop com- pared with the traditional carrier tracking loop based on the second-order frequency lock loop （FLL） assisting third-order phase lock loop （PLL） loop filter. And the optimization methods for the track- ing bandwidth and the carrier loop order are analyzed. The real-time estimation methods of the dy- namic parameters, the velocity, acceleration and jerk along the line of sight （LOS） between the sat- ellite and the receiver＇ s antenna, and the measurement parameters are discussed based on the pres- ented α-β-γ filter algorithm. A method is introduced to improve the filter＇ s dynamic response to meet high dynamic application by self-adjusted α-β-γ filter coefficient used in the tracking loop. The performance of three cases with different carrier tracking loop is compared by simulation.

Design and simulation of digital channelized receivers in fractional Fourier domain

An approach is proposed to realize a digital channelized receiver in the fractional Fourier domain （FRFD） for signal intercept applications. The presented architecture can be considered as a generalization of that in the traditional Fourier domain. Since the linear frequency modulation （LFM） signal has a good energy concentration in the FRFD, by choosing an appropriate fractional Fourier transform （FRFT） order, the presented architecture can concentrate the broadband LFM signal into only one sub-channel and that will prevent it from crossing several sub-channels. Thus the performance of the signal detection and parameter estimation after the sub-channel output will be improved significantly. The computational complexity is reduced enormously due to the implementation of the polyphase filter bank decomposition, thus the proposed architecture can be realized as efficiently as in the Fourier domain. The related simulation results are presented to verify the validity of the theories and methods involved in this paper.

Analysis of Multipath and CW Interference Effects on GNSS Receivers with EMLP Discriminator

Multipath and continuous wave (CW) interference may cause severe performance degradation of global navigation satellite system (GNSS) receivers. This paper analyzes the code tracking performance of early-minus-late power (EMLP) discriminator of GNSS receivers in the presence of multipath and CW interference. An analytical expression of the code tracking error is suggested for EMLP discriminator, and it can be used to assess the effect of multipath and CW interference. The derived expression shows that the combined effects include three components: multipath component;CW interference component and the combined component of multipath and CW interference. The effect of these components depends on some factors which can be classified into two categories: the receiving environment and the receiver parameters. Numerical results show how these factors affect the tracking performances. It is shown that the proper receiver parameters can suppress the combined effects of multipath and CW interference.

Design of Si-bipolar Monolithic Main Amplifier IC for Optical Fiber Receivers

A broadband amplifier with transadmittance and transimpedance stages is designed and two types of improved AGC amplifiers are developed on the base of theory study. Making use of the basic amplifier cells, a main amplifier IC for optical-fiber receivers is deliberated. By computer simulating the performances of the designed main amplifier meet the necessity of high gain and wide dynamic range . They are maximum voltage gain of 42 dB, the bandwidth of 730 MHz,the input signal( V p-p )range from 5 mV to 1 V,the output amplitude about 1 V, the dynamic range of 46 dB. The designed circuit containing no inductance and large capacitance will be convenient for realizing integration. A monolithic integrated design of 622 Mb/s main amplifier is completed.

Calibration of GNSS positioning receivers

Nowadays global navigation satellite system(GNSS)receivers are the primary tool not only for precision surveying but also for geodesy,geophysics and many other industrial applications worldwide.The only way to assure the accuracy,universality and longevity of GNSS measurements is by calibration of its receivers.The parameters affecting the calibration accuracy of a single GNSS receiver are discussed in this paper.And a geodetic basepoint is established according to previous empirical studies to serve as a reference for calibration.Additionally,the traceability to the systeme international(SI)unit of such kind of calibrations is discussed.Stability of the base point is also verified through long-term measurements over three years.Eventually,a calibration of a sample single GNSS receiver is performed and the uncertainty budget is derived.

Limited Bandwidths and Correlation Ambiguities: Do They Co-Exist in Galileo Receivers

Galileo is the Global Navigation Satellite System that Europe is building and it is planned to be operational in the next 3-5 years. Several Galileo signals use split-spectrum modulations, such as Composite Binary Offset Carrier (CBOC) modulation, which create correlation ambiguities when processed with large or infinite front-end bandwidths (i.e., in wideband receivers). The correlation ambiguities refer to the notches in the correlation shape (i.e., in the envelope of the correlation between incoming signal and reference modulated code) which happen within +/– 1 chip from the main peak. These correlation ambiguities affect adversely the detection probabilities in the code acquisition process and are usually dealt with by using some form of unambiguous processing (e.g., BPSK-like techniques, sideband processing, etc.). In some applications, such as mass-market applications, a narrowband Galileo receiver (i.e., with considerable front-end bandwidth limitation) is likely to be employed. The question addressed in this paper, which has not been answered before, is whether or not this bandwidth limitation can cope inherently with the ambiguities of the correlation function, to which extent, and which the best design options are in the acquisition process (e.g., in terms of time-bin step and ambiguity mitigation mechanisms).

Stochastic Analysis of Low-Cost Single-Frequency GPS Receivers

Typically, dual-frequency geodetic grade GNSS receivers are utilized for positioning applications that require high accuracy. Single-frequency high grade receivers can be used to minimize the expenses of such dual-frequency receivers. However, user has to consider the resultant positioning accuracy. Since the evolution of low-cost single-frequency (LCSF) receivers is typically cheaper than single-frequency high grade receivers, it is possible to obtain comparable positioning accuracy if the corresponding observables are accurately modelled. In this paper, two LCSF GPS receivers are used to form short baseline. Raw GPS measurements are recorded for several consecutive days. The collected data are used to develop the stochastic model of GPS observables from such receivers. Different functions are tested to determine the best fitting model which is found to be 3 parameters exponential decay function. The new developed model is used to process different data sets and the results are compared against the traditional model. Both results from the newly developed and the traditional models are compared with the reference solution obtained from dual-frequency receiver. It is shown that the newly developed model improves the root-mean-square of the estimated horizontal coordinates by about 10% and improves the root-mean-square of the up component by about 39%.

Acquisition of Weak Signals in Multi-Constellation Frequency Domain Receivers

New positioning applications’ availability requirements demand receivers with higher sensitivities and ability to process multiple GNSS signals. Possible applications include acquiring one signal per GNSS constellation in the same frequency band and combining them for increased sensitivity or predicting acquisition of other signals. Frequency domain processing can be used for this purpose, since it benefits from parallel processing capabilities of Fast Fourier Transform (FFT), which can be efficiently implemented in software receivers. On the other hand, long coherent integration times are mainly limited due to large FFT size in receivers using frequency domain techniques. A new method is proposed to address the problems in frequency domain receivers without compromising the resources and execution time. A pre-correlation accumulation (PCA) is proposed to partition the received samples into one-code-period blocks, and to sum them together. As a result, the noise is averaged out and the correlation results will gain more power, provided that the relative phase between the data segments is compensated for. In addition to simplicity, the proposed PCA method enables the use of one-size FFT for all integration times. A post-correlation peak combination is also proposed to remove the need for double buffering. The proposed methods are implemented in a configurable Simulink model, developed for acquiring recorded GNSS signals. For weak signal scenarios, a Spirent GPS simulator is used as a source. Acquisition results for GPS L1 C/A and GLONASS L1OF are shown and the performance of the proposed technique is discussed. The proposed techniques target GNSS receivers using frequency domain processing aiming at accommodating all the GNSS signals, while minimizing resource usage. They also apply to weak signal acquisition in frequency domain to answer the availability demand of today’s GNSS positioning applications.

New Strategy of Collaborative Acquisition for Connected GNSS Receivers in Deep Urban Environments

Collaborative Positioning (CP) is a better localization technique used to locate a user in challenged environments, which is driven by the increasing presence of cellular phones and mobile devices in urban areas. The basic idea is that the mobile devices can cooperate with each other to improve their ability to determine their position. In this concept, a network of GNSS (Global Navigation Satellite System) receivers can collectively receive available satellite signals, and each receiver can receive signal measurements from other receivers via a communication link. This work shows how to use the Collective Detection (CD) approach to deal with the concept of collaborative or cooperative positioning. Specifically, this paper develops a new strategy allowing a receiver in deep urban environment to locate using the CD approach, while overcoming the implementation complexity problem. The idea consists in applying the CD approach in the case of multiple GNSS receivers to assist a receiver in a difficult situation. A typical case of two connected receivers assisting a receiver in difficulty in a deep urban area shows the effectiveness of this strategy. This strategy is tested with real GNSS signals to analyze its feasibility. The overall gain in complexity can reach up to 46% of what has been achieved in previous works.

Normalized Design of Multi-channel LIF Digital Receiver

A design method for parallel processing application on multi-channel low-intermediate-frequency(LIF) digital receiver was presented. It is based on the DSP sub-array with a simple topology and operation timing to evaluate and determine the processing capability and then construct the parallel processing array for multi-channel signals according to the restriction of operation timing. Using this method, the design of multi-channel digital receiver may be simplified. Finally, a design example was used to show how to apply this method.