Receiver Channel Research Articles

Multichannel Staggered SAR Azimuth Processing

State-of-the-art and future spaceborne synthetic aperture radar (SAR) systems increasingly often face the requirement of providing high-resolution images with reduced revisit times, requiring coverage of wide swaths. Since these are contradicting drivers in terms of system design, different alternatives for high-resolution wide-swath SAR imaging have been investigated, relying on digital beamforming and the use of multiple receiver channels, both in elevation and azimuth dimensions. In this context, staggered SAR, which operates with a pulse repetition frequency (PRF) variation, using a single channel in azimuth proves itself as a promising alternative for covering wide continuous swaths with moderate azimuth resolution, whereas the use of multiple azimuth receiver channels bears the potential of improving the azimuth resolution over a given swath, but has yet only been applied to systems with a fixed PRF. This paper introduces and analyzes in detail processing techniques suitable for the combination of these techniques, leading to novel multichannel staggered SAR imaging modes with the potential for very fine azimuth resolution over ultra-wide swaths. A system concept with 2-m azimuth resolution over a 400-km swath in quad-pol is provided as an example.

Broadband Reflector Antenna With High Isolation Feed for Full-Duplex Applications

A broadband circularly polarized reflector antenna with high isolation between transmitter and receiver channels is demonstrated theoretically and experimentally. The proposed antenna achieves $\vert S_{11}\vert dB, gain > 21 dBic (with a maximum value of 28 dBic) over the 4–8 GHz operating frequency range. A dual-polarized coaxial cavity antenna is designed to serve as the feed for the axis-symmetry reflector antenna. The inner conductor of the coaxial cavity antenna is extended to integrate the feed with the reflector; therefore, avoiding the use of mounting struts. The proposed configuration is used to realize an antenna subsystem for monostatic simultaneous transmit and receive (STAR)/full-duplex applications. The monostatic STAR operation is achieved by the use of a simple, low-loss beamformer network where hybrids and circulators are arranged to cancel any signal leakage from transmitting to receiving paths leading to high isolation. Practically, the proposed system achieves measured isolation >30 dB which is bounded by the amplitude and phase imbalances of the deployed commercial off-the-shelf components.

Pilot Spoofing Attack Detection and Countermeasure

In a time-division duplex multiple antenna system, the channel state information can be estimated using reverse training. A pilot spoofing (contamination) attack occurs when during the training phase, an adversary (spoofer) also sends synchronized, identical training (pilot) signal as that of the legitimate receiver. This contaminates channel estimation and alters the legitimate beamforming/precoder design, facilitating eavesdropping. A recent approach proposed superimposing a random sequence on the training sequence at the legitimate receiver and then using the minimum description length (MDL) criterion to detect pilot contamination attack. In this paper, we augment this approach with estimation of both legitimate receiver and eavesdropper channels, and secure beamforming, to mitigate the effects of pilot spoofing. We consider two cases: 1) the spoofer transmits only the pilot signal and 2) the spoofer also adds a random sequence to its pilot, mimicking the legitimate receiver. We also employ a random matrix theory-based source enumeration approach instead of MDL, for spoofing detection, leading to improved detection performance. The proposed detection and mitigation approaches are illustrated via simulations.

Low noise 874 GHz receivers for the International Submillimetre Airborne Radiometer (ISMAR).

We report on the development of two 874 GHz receiver channels with orthogonal polarizations for the International Submillimetre Airborne Radiometer. A spline horn antenna and dielectric lens, a Schottky diode mixer circuit, and an intermediate frequency (IF) low noise amplifier circuit were integrated in the same metallic split block housing. This resulted in a receiver mean double sideband (DSB) noise temperature of 3300 K (minimum 2770 K, maximum 3400 K), achieved at an operation temperature of 40 °C and across a 10 GHz wide IF band. A minimum DSB noise temperature of 2260 K at 20 °C was measured without the lens. Three different dielectric lens materials were tested and compared with respect to the radiation pattern and noise temperature. All three lenses were compliant in terms of radiation pattern, but one of the materials led to a reduction in noise temperature of approximately 200 K compared to the others. The loss in this lens was estimated to be 0.42 dB. The local oscillator chains have a power consumption of 24 W and consist of custom-designed Schottky diode quadruplers (5% power efficiency in operation, 8%-9% peak), commercial heterostructure barrier varactor (HBV) triplers, and power amplifiers that are pumped by using a common dielectric resonator oscillator at 36.43 GHz. Measurements of the radiation pattern showed a symmetric main beam lobe with full width half maximum <5° and side lobe levels below -20 dB. Return loss of a prototype of the spline horn and lens was measured using a network analyzer and frequency extenders to 750-1100 GHz. Time-domain analysis of the reflection coefficients shows that the reflections are below -25 dB and are dominated by the external waveguide interface.

SEPIA – a new single pixel receiver at the APEX telescope

Context. We describe the new Swedish-ESO PI Instrument for APEX (SEPIA) receiver, which was designed and built by the Group for Advanced Receiver Development (GARD), at Onsala Space Observatory (OSO) in collaboration with ESO. It was installed and commissioned at the APEX telescope during 2015 with an ALMA Band 5 receiver channel and updated with a new frequency channel (ALMA Band 9) in February 2016. Aim. This manuscript aims to provide, for observers who use the SEPIA receiver, a reference in terms of the hardware description, optics and performance as well as the commissioning results. Methods. Out of three available receiver cartridge positions in SEPIA, the two current frequency channels, corresponding to ALMA Band 5, the RF band 158–211 GHz, and Band 9, the RF band 600–722 GHz, provide state-of-the-art dual polarization receivers. The Band 5 frequency channel uses 2SB SIS mixers with an average SSB noise temperature around 45 K with IF (intermediate frequency) band 4–8 GHz for each sideband providing total 4 × 4 GHz IF band. The Band 9 frequency channel uses DSB SIS mixers with a noise temperature of 75–125 K with IF band 4–12 GHz for each polarization. Results. Both current SEPIA receiver channels are available to all APEX observers.

Synthetic Aperture Sonar Image Contrast Prediction

Sidescan imaging sonar performance is often described using metrics such as resolution, maximum range, and area coverage rate. These attributes focus on describing how finely and over what area a sensor can make imagery of the seafloor and targets. While these metrics are important, they are inadequate for fully characterizing the quality of sonar imagery. Shadow regions often carry as much, and sometimes even more, information than the direct return from a target. The shadow contrast within an image is therefore a critical property, and it is the result of a complex interaction between the sonar hardware, the environment, and the signal processing. This paper builds on key results from the synthetic aperture radar and sonar literature to develop a comprehensive, quantitative model for predicting the shadow contrast ratio. A model for the contrast ratio is constructed using an approach that is similar to the development of the sonar equation. This ratio describes the average relative level between the seafloor and a shadow. The model includes the effects of the transducer and array design, ambient noise, quantization noise, unwanted volume and surface reverberation, and the signal processing used to construct the synthetic aperture sonar (SAS) imagery. The shadow contrast predicted by the model is compared to the contrast measured from SAS imagery, where close agreement is observed. Examples are presented where the model is applied to a hypothetical high-frequency imaging SAS sensor in a typical operating environment. The shadow contrast ratio is estimated as a function of the sensor range and key parameters of interest, such as receiver channel spacing, sediment backscatter coefficient, and the time-bandwidth product of the transmitted signal. At long ranges, the contrast ratio is limited by additive noise interference, while at near ranges the effect of the receiver channel spacing dominates the contrast ratio through along-track ambiguities. The use of this tool for analysis and prediction of image quality has significant implications for system design, mission planning, and data processing.

Method for the detection of small­sized air objects by observational radars

We proposed the introduction of an additional mode of dispersed reception and the combination of one-position and multiple reception of signals to the existing one-position observation radar. We improved the algorithm for detection of an air object at its irradiation by several transmitters. We provided compensation of a delay time and Doppler frequency in each receiving channel to a separate volume of an observation radar upgrading the algorithm. The improved algorithm for detection of an air object at its irradiation by several transmitters is reduced to: coherent processing of received signals in each processing channel in each element corresponding to the relevant separate volume and the relevant separate Doppler frequency; quadratic detection in each processing channel in each element corresponding to the relevant separate volume and the relevant separate Doppler frequency; weight summation of detector outputs for each processing channel in each element corresponding to the relevant separate volume and the relevant separate Doppler frequency. We constructed a structural diagram of the detector of an air object at its illumination by several transmitters. Each receiving channel of a signal is a multichannel for distance and speed. The diagram provides reception, coherent processing of echo signals from third-party sources, compensation of delay and Doppler frequency differences relative to a separate volume of the observation radar and incoherent weight summation. We carried out estimation of the efficiency of detection of an air object at its irradiation by several transmitters. We established that the transition from a single-channel detection of an air object to the detection of an air object at the incoherent combination of two channels results in a significant shift of detection characteristics to the left. We selected the number of receiving channels to be combined. We established that it is most effective to combine two, at most three, reception channels. We constructed a structural diagram of channels that process echo signals of an observation radar by combining the methods of one-position and differential signal reception. For combining of one-position and dispersed location modes of observation radars, we provided complexing of corresponding digital reception devices and digital signal processing systems. The main principle underlying the combination of the mentioned receiving devices is the informational supplement without violating the standard modes of operation of observation radar.

ANALISIS KEBUTUHAN SUMUR RESAPAN SEBAGAI PENCEGAHAN LIMPASAN AIR HUJAN PADA PERUMAHAN PUSRI SEMBAWA BANYUASIN

In accordance with rapid development in Banyuasin Regency has effected the increased use of land that is built into residential areas. Land use is unwittingly can affect and disrupt the hydrological cycle which causes a negative impact on the environment. It consequenlly, it reduces soil absorption and causes excessive surface run off. Therefore there must be anticipatory steps to reduce rainwater runoff. Infiltration wells can be some to figure out the issue. This research aims to plan the infiltration wells design to reduce rainwater runoff and to know the capacity of drainage channel in Pusri Residence Sembawa Banyuasin. The result of data analysis shows that most of runoff occur in drainage channel of receiver except in segment of Block A1-A2 and Block D1 - D2 and at collector channel. The largest receiver discharge (Q2) is 0.2378 on block V1 - V2. The results of the infiltration wells design is a circle with a diameter of 1 meter and a depth of 3.5 meters. The debit plan for the 2nd year return period with rain intensity 505,9905 mm / hr is 0,0296 m3 / s, while the discharge of the infiltration wells of each plot is 0,0032 m3 / dt for type 36/84. The rain water discharge of infiltration wells with a duration of 30 minutes and the number of house plots is 0.0253 m3 / s, while the discharge plan on channel A-B is 0.0296 m3 / s. After the use of infiltration wells the, remaining discharge of rain water entering on receiver channel on block A-B equal to 0,0265 m3 / s.Keywords: Infiltration Wells, Runoff, permeability

ALMA Band 5 receiver cartridge

We describe the design, performance, and commissioning results for the new ALMA Band 5 receiver channel, 163–211 GHz, which is in the final stage of full deployment and expected to be available for observations in 2018. This manuscript provides the description of the new ALMA Band 5 receiver cartridge and serves as a reference for observers using the ALMA Band 5 receiver for observations. At the time of writing this paper, the ALMA Band 5 Production Consortium consisting of NOVA Instrumentation group, based in Groningen, NL, and GARD in Sweden have produced and delivered to ALMA Observatory over 60 receiver cartridges. All 60 cartridges fulfil the new more stringent specifications for Band 5 and demonstrate excellent noise temperatures, typically below 45 K single sideband (SSB) at 4 K detector physical temperature and below 35 K SSB at 3.5 K (typical for operation at the ALMA Frontend), providing the average sideband rejection better than 15 dB, and the integrated cross-polarization level better than –25 dB. The 70 warm cartridge assemblies, hosting Band 5 local oscillator and DC bias electronics, have been produced and delivered to ALMA by NRAO. The commissioning results confirm the excellent performance of the receivers.

Performance Characterization of Spatially Random Energy Harvesting Underlay D2D Networks With Transmit Power Control

In underlay device-to-device (D2D) networks, the transmitter nodes can harvest energy from downlink cellular (primary) transmissions to solely power the D2D links, which enhances the overall spectral and energy efficiencies. How will the energy harvest and D2D link performance be affected by spatial randomness, temporal correlations, transmit power control, and channel uncertainties? To investigate these issues, we analyze the energy harvesting process of a random (typical) D2D transmitter node, say $\mathcal D_{t}$ , which needs a sufficient harvest to meet the requirements for receiver sensitivity and channel inversion. This system model consists of: 1) three independent homogeneous Poisson point processes; 2) log-distance path loss and Rayleigh fading; and 3) path loss inversion transmit power control. We derive the ambient radio frequency energy at $\mathcal D_{t}$ , and model the harvest as a Gamma random variable. We propose four schemes: 1) single slot harvesting; 2) multislot harvesting; 3) $\mathcal {N}$ slot harvesting; and 4) hybrid harvesting. We develop a Markov chain model for success probability of these schemes, and derive the D2D coverage. We find that a high density of primary transmitters is unfavorable to multislot harvesting for increased D2D link distances. Moreover, hybrid harvesting always outperforms single and $\mathcal {N}$ slot harvesting, and outperforms multislot harvesting except for very high path-loss conditions.

Shallow water multichannel sub-bottom profiling using Kirchhoff imaging

Single-channel sub-bottom profilers are commonly used for shallow water seismic investigation. This work reports the design and construction of a multiple channel profiler that allows more effective seismic imaging techniques. The system is composed of a controlled acoustic source and a 1.6 m long array with eight evenly spaced receiver channels, and operates using CHIRP signals with frequency ranging from 800 Hz to 8 kHz. A survey was carried out to obtain seismic data in the region of Lagoa da Conceição, Santa Catarina, Brazil. The acquired data was processed using a seismic imaging technique based on the pre-stack Kirchhoff time migration. Both the multichannel seismic data acquisition system and the applied imaging technique showed to be robust for acquiring subsurface information. The use of the pre-stack Kirchhoff time migration resulted in a seismic image with reflection events allocated in the real position and without bow-tie effects since it repositions the diffracted energy back to the spreaders that originated it. This procedure results in a more reliable subsurface image of the studied environment, when compared with single-channel sub-bottom profilers.

A Portable K-Band 3-D MIMO Radar With Nonuniformly Spaced Array for Short-Range Localization

This paper presents a $K$ -band multiple-input-multiple-output (MIMO) radar for short-range localization. This radar features 3-D imaging capability, which can obtain the range, azimuth angle, and zenith angle of a target. The proposed radar system implements the concept of MIMO to synthesize a planar array that realizes 2-D digital beamforming with a small number of transmitter and receiver (T/R) channels. A nonuniformly spaced array configuration is also designed to further reduce the number of T/R channels without sacrificing the beamwidth and sidelobe level. The design principle is detailed in this paper. A prototype with eight transmitter channels and eight receiver channels has been built. A calibration procedure was developed to remove path delays of different MIMO channels. Experiments of the proposed ${K}$ -band MIMO radar prototype reveal its capability in the 3-D localization of multiple targets. This prototype features 7.2° 2-D angular resolution, 90° field of view, −10-dB sidelobe level, and wireless data transfer.

Differential Phase Measurement Accuracy of a Monobit Receiver

Differential phase measurements using two receiver channels are used to calculate the angle of arrival of a target signal. A monobit receiver architecture is a desirable receiver type due to its low hardware complexity, sampling rate, and power efficiency. The application motivating this paper benefits from the use of automatic gain control circuitry and sensitivity offered by the monobit architecture. However, the one-bit sampling of the input signal introduces undesirable non-linear effects. This paper analyzes the effects of a monobit receiver architecture on the differential phase accuracy. Simulated results are compared to measurement data collected from prototype monobit receiver hardware. The measured data had good agreement with the simulated results. At a high-input signal-to-noise ratio of 30 dB, the differential phase measurement sigma was approximately 0.66° for input phase shifts of 0°, 45°, and 90°. While the differential phase measurement accuracy is less than predicted by the Cramer–Rao lower bound, it is sufficient for the low cost, power, and size constrained sensor application motivating this paper.

Invited Paper] Adaptive Configuration of Forward Channels for Terminal Collaborative Reception

Invited Paper] Adaptive Configuration of Forward Channels for Terminal Collaborative Reception

Performance Analysis of IEEE 802.11p Safety Message Broadcast With and Without Relaying at Road Intersection

Dedicated short-range communication (DSRC), which is an essential part of vehicle-to-vehicle/infrastructure communication to enhance the road safety, is often characterized by the IEEE 802.11p standard. Numerous works have been done on the DSRC safety message broadcasting performance for highway scenario. However, up to date, no work has been done on the performance of the IEEE 802.11p safety message broadcasting for the road-intersection scenario in urban environment. An intersection scenario is different from a highway scenario. In a highway scenario, it is often been considered that all the vehicles have the same communication range as well as the same carrier sensing range. However, this is not the case for the intersection scenario, where there exist a lot of obstructions, such as buildings and urban canyons. In an intersection, the communication and carrier sensing ranges of a vehicle heavily depend on the location of that vehicle. This paper first analyzes and then provides solution on improving the broadcasting performance of the DSRC safety message at an intersection while considering the IEEE 802.11p enhanced distributed channel access mechanism. To facilitate different communication and carrier sensing ranges of different vehicles, we divide the intersection region into few parts/areas based on an empirically validated path loss model. We present an analytical study on the packet reception rates and channel access delay which is applicable for the different positions of transmitters and receivers in the intersection areas. The analytical results are verified by the NS-3 simulation. From the results, we find that the overall delivery ratio is very poor when the broadcasting vehicle is not close enough to the intersection-center. To improve the overall broadcast performance of such scenarios, we employ a road side unit (RSU) at the intersection-center to relay the safety messages once. We show the performance improvement via relaying while first using omni-directional and then using special sector antennas, the so-called bidirectional antenna, at the RSU. From the results, it is shown that relaying with the omni-directional antenna gives moderate improvement on the overall delivery ratio, while a significant improvement can be achieved by relaying with sector antenna.

A Fully Integrated 300-MHz Channel Bandwidth 256 QAM Transceiver With Self-Interference Suppression in Closely Spaced Channels at 6.5-GHz Band

We present a fully-integrated 256 QAM single-chip transceiver (TRX) with 300-MHz channel bandwidth at the 6.5-GHz band. A novel architecture for self-interference suppression (SIS) is proposed. A noise-canceling low-noise amplifier with the embedded programmable source degeneration network based on the bond wires, manifesting the notch filtering characteristics of the self-interference signal, has been utilized to facilitate the SIS, and LC -tuned tanks further improve the interference filtering in a receiver (RX) and considerable adjacent channel leakage power ratio in a transmitter (TX). The SAW-less /duplexer-less TRX allows TDD/FDD co-operation in closely spaced channels. The RX achieves a noise figure (NF) as low as 3 dB with +17.5-dBm out-of-band IIP3. The EVM is 2.02% and 2.72% for the RX and TX, respectively, in 160-MHz bandwidth OFDM 256 QAM. In the SIS mode, the blocker P1dB is −8 dBm, and the NF of the RX degrades only 2.1 dB (from 3.0 to 5.1 dB), withstanding 0-dBm interference at 150-MHz offset. The TRX exhibits a slight EVM degradation (from 2.02% to 2.98%) when receiving a −40-dBm 160-MHz bandwidth 256 QAM desired signal, in the presence of a −15-dBm 80-MHz bandwidth self-interference signal at 300-MHz offset. The TRX has been implemented in 0.13- $\mu \text{m}$ CMOS with superior overall performances.

Thermal design of a plate receiver for cooling densely packed photovoltaic cells with a point focusing solar concentrator

The viability of a plate receiver for an array of densely packed photovoltaic cells with a point focusing solar concentrator has been investigated. A cooling receiver being similar to a multi-channel receiver was designed and a thermal resistance model was developed to optimize the geometric parameters. Furthermore, the simulation results found that when the receiver fin height, channel width, and width of the fin wall is 15, 1, and 5.8 mm, respectively, the total ther- mal resistance could be less than 4 cm2?C/W under a constant volumetric flow rate of 0.1 L/s. A physical prototype has been built according to the simulation results. A performance test has been conducted to investigate the temperature distribution and the thermal performance. The experimental results reveal that the new design of the plate receiver has a desirable working performance and it is acceptable for the cooling application of photovoltaic cells which expose to high heat fluxes.

Повышение эффективности подавления помех за счет коррекции частотных характеристик приемных каналов в навигационной аппаратуре потребителей

Space-time signal processing in adaptive electronic systems, including navigation, remains the subject of intensive research, as it allows to improve the efficiency of receiving useful signals under the influence of natural or intentional interference. The bibliography on this subject is very extensive and includes a large number of articles of scientific and applied nature, dissertations, monographs, patent materials. Much of this work has references to monographs by R. Monzingo and B. Widrow, which set out the basic principles, criteria and algorithms of spatial-temporal signal processing. To date, the development of space-time signal processing is largely constrained by the imperfection of the element base. The use of modern navigation equipment consumers high-speed signal processors that implement advanced methods and algorithms of digital signal processing, provides the ability of digital methods to form the desired beam pattern of the antenna system and to adjust the frequency characteristics of the reception channels, to implement complex algorithms for optimal processing of useful signals, operative to control the main operation modes of equipment. One of the most important applications of space-time signal processing is noise suppression, and its effectiveness depends on the degree of inter-channel correlation of these signals received by antenna elements of the adaptive antenna array. To maximize the coefficient of interference suppression required the adoption of measures on alignment of frequency and phase characteristics of the receiving circuits, and high precision computation of weighting coefficients. The article considers the questions of spatial filtering of the interference when adaptive interference compensator adjusted frequency characteristics of the receiving channels, and means of satellite navigation. Gradient algorithm of spatial compensation of noise, and also influence of adaptive correction of frequency characteristics of receiving channels on quality of suppression of noise is presented. The formation of a directional diagram of a multi-element adaptive antenna array with spatial noise suppression is demonstrated by modeling in the Matlab environment.

Turbo Receiver Channel Estimation for GFDM-Based Cognitive Radio Networks

Generalized frequency division multiplexing (GFDM) is a promising candidate for 5G waveforms because of its flexibility to meet the requirements of different scenarios and applications. Compared with the orthogonal frequency division multiplexing, the lower out-of-band radiation and higher spectrum efficiency make GFDM the qualified waveform solution for cognitive radio (CR). In CR networks, channel estimation is the necessity and premise to guarantee reliable spectrum sensing. Because of the block modulation structure for GFDM, conventional channel estimation algorithm cannot be applied to GFDM directly. Also, the feedback information in channel decoding is not fully utilized by the conventional algorithm. To solve these problems, in this paper, a modified turbo receiver is designed to utilize the feedback information for channel estimation. The modulator for the pilot insertion is also improved to make pilots orthogonal to data subcarriers. Based on the modified turbo receiver, an iterative channel estimation strategy combined with threshold control is proposed to cope with the noise enhancement. The symbols rebuilt for the iterative channel estimation are verified that only the credible symbols can be retained for the next iteration. Simulation results demonstrate that the proposed channel estimation method has the better bit error rate and mean-squared error performances over Rayleigh fading channel compared with the conventional algorithm.

Multi-pulse laser ranging method for pre-detection with high frequency resonance

Based on the measurement principle of pulse time-of-flight, non-cooperative target ranging technology using a pulsed laser diode (LD) as a light source has received widespread attention in recent years. Using leading edge timing method to directly detect pulses, its measuring range is about a few tens of meters and only a cm-level single-shot accuracy could be reached due to the limitations of its pulse width and eye-safe laser power of the LD, which cannot meet the needs of most applications. Especially, in order to increase its receiver channel bandwidth from hundreds of MHz to even a few GHz to reduce its work error, its distance measurement accuracy and ranging distance are significantly degraded as its signal-to-noise ratio (SNR) decreases. When a target is out of its measuring range, the back diffused laser pulse signal with an SNR of much less than 1 will be too weak to be extracted even with digital correlation processing technology.In this paper, using a pre-detection with high frequency resonance and multi-pulse correlation processing, a new ranging method to solve long ranging targets with high precision is proposed for the first time. Through the pre-detection circuit with high frequency resonance, a pulsed photocurrent signal is amplified and filtered, and then converted into a bipolar attenuation oscillation signal. Thereafter, its SNR is further improved by a new pulse function constructed through multi-pulse correlation processing. The peak of the new pulse is constant and its zero crossing point is found to be the timing point to calculate the target distance. The method has a better SNR and a high timing accuracy. And the detected ranging distance could be increased over one thousand meters or more. Theoretical calculation results show that the minimum detectable peak current of light pulse is around 17 nA in the method. Comparing with the direct pulse detection method, its SNR can increase 60 times. When a received peak of a photocurrent pulse is within a dynamic range of 1:10000, its work error is less than 0.1 ps. A pulsed laser rangefinder is developed based on the principle. And its average laser emission power is about 1 mW. Its measurement ranging without cooperative target is greater than 2000 m. Its distance measurement accuracy increases up to ± (3 mm+2 ppm) in a range of 1.5-300 m. For a long ranging target, its distance measurement accuracy is ± (10 mm+10 ppm). The rangefinder system is used in a total station product and can be used to measure large-scale engineering structures (such as roads, bridges, dams, tunnels, subways, etc.), building structures and industrial sites.