Use Of Receivers Research Articles

A Frequency Translation System for Multi-Channel, Multi-Nuclear MR Spectroscopy.

Most MRI scanners are equipped to receive signals from 1H array coils but few support multi-channel reception for other nuclei. Using receive arrays can provide significant SNR benefits, usually exploited to enable accelerated imaging, but the extension of these arrays to non-1H nuclei has received less attention because of the relative lack of broadband array receivers. Non-1H nuclei often have low sensitivity and stand to benefit greatly from the increase in SNR that arrays can provide. This paper presents a cost-effective approach for adapting standard 1H multi-channel array receivers for use with other nuclei - in this case, 13C. A frequency translation system has been developed that uses active mixers residing at the magnet bore to convert the received signal from a non-1H array to the 1H frequency for reception by the host system receiver. This system has been demonstrated at 4.7T and 7T while preserving SNR and isolation. 1H decoupling, particularly important for 13C detection, can be straightforwardly accommodated. Frequency translation can convert 1H-only multi-channel receivers for use with other nuclei while maintaining SNR and channel isolation while still enabling 1H decoupling. This work allows existing multi-channel MRI receivers to be adapted to receive signals from nuclei other than 1H, allowing for the use of receive arrays for in vivo multi-nuclear NMR.

Optimization Design and Experimental Testing of a Laser Receiver for Use in a Laser Levelling Control System

The elevation detection accuracy of the laser receiver in the laser levelling control system directly affects land-levelling operations. To effectively improve the effect of levelling operations and meet the requirements for the accuracy of elevation detection in different industries, this study optimization designed a multilevel adjustable laser receiver. First, we examined the laser signal detection technology and processing circuit, designed the photoelectric conversion array for the detection of the rotating laser, and converted it into a photocurrent signal. We also designed the filter, amplifier, and shaping and stretching circuits for analogue-to-digital conversion of the photocurrent signal. The digital signal was calculated based on the deviation of the elevation by using a microprocessor and was output by a controller area network (CAN) bus. The laser beam spot diameter transmission and diffusion were then studied, and with the detectable spot diameters were compared and analyzed. Accordingly, an algorithm was proposed to calculate the deviation of laser receiver elevation. The resolution of the elevation deviation was set to ±3 mm; however, this value could be adjusted to ±6 mm, ±9 mm, ±12 mm, and ±15 mm, according to the requirements. Finally, the laser receiver was tested and analyzed, and the test results of the elevation detection accuracy showed that when the laser receiver was within a radius of 90 m, the elevation detection accuracy was within the ±3 mm range. The outcomes of the farmland-levelling test showed that the standard deviation S d of the field surface decreased from 9.54 cm before levelling to 2.42 cm after levelling, and the percentage of sampling points associated with absolute errors of ≤3 cm was 84.06%. These outcomes meet the requirements of high-standard farmland construction. The test results of concrete levelling showed that within a radius of 30 m, the standard deviation S d of the elevation adjustment of the left laser receiver was 1.389 mm, and the standard deviation S d of the elevation adjustment of the right laser receiver was 1.316 mm. Furthermore, the percentage of the sampling points associated with absolute elevation adjustment errors of ≤3 mm in the cases of the two laser receivers was 100% after levelling, whereas the standard deviation S d of the sand bed surface was 0.881 mm. Additionally, the percentage of the sampling points associated with absolute errors of ≤3 mm was 100%. This met the construction standards of the concrete industry.

Proof of Concept for an Intracochlear Acoustic Receiver for Use in Acute Large Animal Experiments

(1) Background: The measurement of intracochlear sound pressure (ICSP) is relevant to obtain better understanding of the biomechanics of hearing. The goal of this work was a proof of concept of a partially implantable intracochlear acoustic receiver (ICAR) fulfilling all requirements for acute ICSP measurements in a large animal. The ICAR was designed not only to be used in chronic animal experiments but also as a microphone for totally implantable cochlear implants (TICI). (2) Methods: The ICAR concept was based on a commercial MEMS condenser microphone customized with a protective diaphragm that provided a seal and optimized geometry for accessing the cochlea. The ICAR was validated under laboratory conditions and using in-vivo experiments in sheep. (3) Results: For the first time acute ICSP measurements were successfully performed in a live specimen that is representative of the anatomy and physiology of the human. Data obtained are in agreement with published data from cadavers. The surgeons reported high levels of ease of use and satisfaction with the system design. (4) Conclusions: Our results confirm that the developed ICAR can be used to measure ICSP in acute experiments. The next generation of the ICAR will be used in chronic sheep experiments and in TICI.

First results of registering ionospheric disturbances obtained with SibNet network of GNSS receivers in active space experiments

Global and regional networks of GNSS receivers have been successfully used for geophysical research for many years; the number of continuous GNSS stations in the world is steadily growing. The article presents the first results of the use of a new regional network of GNSS stations (SibNet) in active space experiments. The Institute of Solar-Terrestrial Physics of Siberian Branch of Russian Academy of Sciences (ISTP SB RAS) has established this network in the South Baikal region. We describe in detail SibNet, characteristics of receivers in use, parameters of antennas and methods of their installation. We also present the general structure of observation site and the plot of coverage of the receiver operating zone at 50–55° latitudes by radio paths. It is shown that the selected location of receivers allows us to detect ionospheric irregularities of various scales. The purpose of the active space experiments was to reveal and record parameters of the ionospheric irregularities caused by effects from jet streams of Progress cargo spacecraft. The mapping technique enabled us to identify weak, vertically localized ionospheric irregularities and associate them with the Progress spacecraft engine impact. Thus, it has been shown that SibNet deployed in the Southern Baikal region is an effective instrument for monitoring iono-spheric conditions.

Первые результаты регистрации ионосферных возмущений по данным сети SibNet приемников ГНСС в активных космических экспериментах

Global and regional networks of GNSS receivers have been successfully used for geophysical research for many years; the number of continuous GNSS stations in the world is steadily growing. The article presents the first results of the use of a new regional network of GNSS stations (SibNet) in active space experiments. The Institute of Solar-Terrestrial Physics of Siberian Branch of Russian Academy of Sciences (ISTP SB RAS) has established this network in the South Baikal region. We describe in detail SibNet, characteristics of receivers in use, parameters of antennas and methods of their installation. We also present the general structure of observation site and the plot of coverage of the receiver operating zone at 50–55° latitudes by radio paths. It is shown that the selected location of receivers allows us to detect ionospheric irregularities of various scales. The purpose of the active space experiments was to reveal and record parameters of the ionospheric irregularities caused by effects from jet streams of Progress cargo spacecraft. The mapping technique enabled us to identify weak, vertically localized ionospheric irregularities and associate them with the Progress spacecraft engine impact. Thus, it has been shown that the SibNet deployed in the Southern Baikal region is an effective instrument to monitor ionospheric conditions.

Design, Implementation, and Performance Evaluation of a Flexible Low-Latency Nanowatt Wake-Up Radio Receiver

Wireless sensor networks (WSNs) have received significant attention in recent years and have found a wide range of applications, including structural and environmental monitoring, mobile health, home automation, Internet of Things, and others. As these systems are generally battery operated, major research efforts focus on reducing power consumption, especially for communication, as the radio transceiver is one of the most power-hungry components of a WSN. Moreover, with the advent of energy-neutral systems, the emphasis has shifted toward research in microwatt (or even nanowatt) communication protocols or systems. A significant number of wake-up radio receiver (WUR) architectures have been proposed to reduce the communication power of WSN nodes. In this work, we present an optimized ultra-low power (nanowatt) wake-up receiver for use in WSNs, designed with low-cost off-the-shelf components. The wake-up receiver achieves power consumption of 152 nW (with -32 dBm sensitivity), sensitivity up to -55 dBm (with maximum power of 1,2 μW), latency from 8 μs, tunable frequency, and short commands communication. In addition, a low power solution, which includes addressing capability directly in the wake-up receiver, is proposed. Experimental results and simulations demonstrate low power consumption, functionality, and benefits of the design optimization compared with other solutions, as well as the benefits of addressing false positive (FP) outcomes reduction.

Leveraging spatial diversity to mitigate interference in underwater acoustic communication networks

Many acoustic channels suffer from interference which is neither narrowband nor impulsive. This relatively long duration partial band interference can be particularly detrimental to system performance. We survey recent work in interference mitigation and orthogonal frequency division multiplexing (OFDM) as background motivation to develop a spatial diversity receiver for use in underwater networks. The network consists of multiple distributed cabled hydrophones that receive data transmitted over a time-varying multipath channel in the presence of partial band interference produced by interfering active sonar signals as well as marine mammal vocalizations. In operational networks, many dropped messages are lost due to partial band interference which corrupts different portions of the received signal depending on the relative position of the interferers, information source and receivers due to the slow speed of propagation.

A RAKE RECEIVER DESIGN FOR ULTRA WIDE BAND APPLICATION

In this paper, we describe the design and implementation of a rake receiver for use with ultra wide band (UWB) systems. The rake receiver uses spread spectrum modulation (SSM) aided by kasami sequence generator. The combination is found to be effective in dealing with multipath fading and signal to noise ratio. The design is initially simulated using MATLAB 7.10 and is implemented using a HDL coder. The design is also implemented in a FPGA kit and is found to be effective in interference mitigation as part of a CDMA framework.

Dynamic Accuracy of GPS Receivers for Use in Health Research: A Novel Method to Assess GPS Accuracy in Real-World Settings

The emergence of portable global positioning system (GPS) receivers over the last 10 years has provided researchers with a means to objectively assess spatial position in free-living conditions. However, the use of GPS in free-living conditions is not without challenges and the aim of this study was to test the dynamic accuracy of a portable GPS device under real-world environmental conditions, for four modes of transport, and using three data collection intervals. We selected four routes on different bearings, passing through a variation of environmental conditions in the City of Copenhagen, Denmark, to test the dynamic accuracy of the Qstarz BT-Q1000XT GPS device. Each route consisted of a walk, bicycle, and vehicle lane in each direction. The actual width of each walking, cycling, and vehicle lane was digitized as accurately as possible using ultra-high-resolution aerial photographs as background. For each trip, we calculated the percentage that actually fell within the lane polygon, and within the 2.5, 5, and 10 m buffers respectively, as well as the mean and median error in meters. Our results showed that 49.6% of all ≈68,000 GPS points fell within 2.5 m of the expected location, 78.7% fell within 10 m and the median error was 2.9 m. The median error during walking trips was 3.9, 2.0 m for bicycle trips, 1.5 m for bus, and 0.5 m for car. The different area types showed considerable variation in the median error: 0.7 m in open areas, 2.6 m in half-open areas, and 5.2 m in urban canyons. The dynamic spatial accuracy of the tested device is not perfect, but we feel that it is within acceptable limits for larger population studies. Longer recording periods, for a larger population are likely to reduce the potentially negative effects of measurement inaccuracy. Furthermore, special care should be taken when the environment in which the study takes place could compromise the GPS signal.

Front-end electronics for the upgraded GMRT

This paper first describes briefly the existing front-end receiver in use at the GMRT observatory and then details the ongoing development of next generation receiver systems for the upgraded GMRT. It covers the design of the new, two stage, room temperature, low noise amplifiers with better noise performance and matching, and improved dynamic range that are being implemented for the 130–260 MHz, 250–500 MHz and 550–900 MHz bands of the upgraded GMRT front-end systems.

A 70-mW ISDB-T Tuner for VHF and UHF Bands

This brief presents a highly integrated low-Intermediate Frequency receiver for use in UHF/VHF channel 7 and Channel 8 Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) systems (90-220 MHz). It features an ultralow power consumption of 68 mW (55 mW in attenuator mode) with a noise figure of 3 dB. The device fully complies with the ISDB-T standard and is implemented in 0.13-μm CMOS technology with fully integrated low-noise amplifier/matching networks, a voltage-controlled oscillator, a phase-locked loop/loop filter, a crystal oscillator, baseband filters, and Variable Gain Amplifier. The tuner only requires a prefiltering RF surface acoustic wave filter to notch out cellular frequencies and a biasing inductor to implement a fully compliant ISDB-T tuner. The full characterization of the tuner and the comparison with previous implementation are presented. The chip area is 2.1 mm × 2.1 mm.

Electroacoustic Transducer Mounting In Shells Of Hearing Prostheses

A hearing aid and a receiver for use therein, the receiver being tip-mountable in a chamber of a housing. The back chamber of the receiver is acoustically connected to the chamber of the housing. The receiver is a dual-diaphragm receiver providing no or very little vibrations, whereby the receiver is fixedly but removably mounted to the housing. Electrical connections are provided between the receiver and housing using solderless, biasing electrical contacts, whereby removal of the receiver is facilitated.

A Discrete-Time FFT Processor for Ultrawideband OFDM Wireless Transceivers: Architecture and Behavioral Modeling

A discrete-time (DT) fast Fourier transform (FFT) processor which enables an architectural improvement to ultrawide-bandwidth orthogonal frequency-division multiplexing (OFDM) receivers for use in low-power handheld applications is presented. The new architecture performs FFT demodulation of the OFDM signal in the DT signaling domain before analog-to-digital conversion. The approach significantly reduces the required number of bits in the analog-to-digital converter (ADC) while increasing receiver linearity and providing improved handling of narrow-band blockers. The processor is first implemented in simulation using a top-down methodology based on behavioral models which are developed to describe the circuit functions of the DT FFT processor. System simulation results show that the processor can be implemented with DT CMOS circuits having typical nonidealities while outperforming equivalent all-digital FFT processors. An improvement in dynamic range in the FFT processor and ADC from 35 to 54 dB is demonstrated through simulation.

ALMA North American Integration Center Front-End Test System

The Atacama Large Millimeter/submillimeter (ALMA) Array Front End (FE) system is the first element in a complex chain of signal receiving, conversion, processing and recording. 70 Front Ends will be required for the project. The Front End is designed to receive signals in ten different frequency bands. In the initial phase of operations, the antennas will be fully equipped with six bands. These are Band 3 (84-116 GHz), Band 4 (125-163 GHz), Band 6 (211-275 GHz), Band 7 (275-373 GHz), Band 8 (385-500 GHz) and Band 9 (602-720 GHz). It is planned to equip the antennas with the missing bands at a later stage of ALMA operations, with a few Band 5 (163-211 GHz) and Band 10 (787-950 GHz) receivers in use before the end of the construction project. The ALMA Front End is far superior to any existing receiver systems; spin-offs of the ALMA prototypes are leading to improved sensitivities in existing millimeter and submillimeter observatories. The Front End units are comprised of numerous elements, produced at different locations in Europe, North America and East Asia and are integrated at several Front End integration centers (FEIC) to insure timely delivery of all the units to Chile. The North American FEIC (NA FEIC) is at the National Radio Astronomy Observatory facility in Charlottesville, Virginia, USA. This paper describes the design and performance of the test set used at the NA FEIC to check the performance of the Front Ends, following integration and prior to shipment to Chile.

Issues of identifying, estimating and using delay times in telecontrol systems based on TCP/IP networks

Today's performant equipment and high speed connections make network control systems a reality. For a series of teleoperation applications like the ones from network control systems domain it is essential to estimate the time delay between the acquisition moment of primary data that needs to be sent and the moment it is available for the receiver's use. This paper presents a methodology for estimating the time delay from experimental measurements, while also taking into account the information loss during transmission. A series of unwanted exceptions that may occur in signal transmission are identified and solution methods are proposed. Based on the above study, three real scenarios were designed for three TCP/IP network types. These scenarios were implemented through simulations for a telecontrol system that uses adaptive PD compensators for the time-varying delays. Finally, the improvement in the system's performances with the PD compensators were validated using real life scenarios.

Disjoint detection in polarization multiplexed communication systems affected by polarization dependent loss

We study the performance of a simple optical receiver for use with polarization multiplexed transmission in the presence of polarization dependent loss (PDL). The receiver is based upon filtering of each of the channels with a polarizer that is orthogonal to the other channel, such that interference due to loss of orthogonality is avoided at the expense of a reduction in the detected signal to noise ratio. In spite of its simplicity, this receiver is shown to perform almost as well as the optimal maximum likelihood receiver, and much better than receivers that are based on conventional polarization splitting.

Practical architecture of a broadband sensing receiver for use in cognitive radio

This paper proposes a dedicated sensing receiver architecture that addresses some challenges of broadband sensing in Cognitive Radios. Specifically, we address broadband sensing challenges for delay sensitive applications such as voice. A subjective calculation of an acceptable voice delay is used as a reference in our analysis. In the proposed architecture, fast response and accurate sensing is aided by the combination of power sensing at RF, baseband and in the digital domain. Since the sensing workload is distributed, the performance requirement on the main receiver is relaxed. The proposed architecture provides the ability to perform adaptive coarse and fine sensing at different points in the receiver chain. The estimated sensing time is derived and simulation results to illustrate the performance improvement are presented.

Performance comparison of semicodeless GPS receivers for LEO satellites

This report provides a detailed performance analysis of three semicodeless dual-frequency GPS receivers for use in low Earth orbit (LEO). The test set comprises the IGOR receiver, which represents a follow-on of the flight-proven BlackJack receiver, as well as two geodetic receivers (NovAtel OEM4-G2 and Septentrio PolaRx2), which are entirely based on commercial-off-the-shelf technology (COTS). All three receivers are considered for upcoming flight projects or experiments and have undergone at least a preliminary environmental qualification program. Using extensive signal simulator tests, the cold start signal acquisition, tracking sensitivity, differential code biases, raw measurement accuracy, and navigation accuracy of each receiver have been assessed. All tests are based on a common scenario that is representative of an actual space mission and provides a realistic simulation of the signal dynamics and quality on a scientific LEO satellite. Compared to the other receivers, the IGOR instrument exhibits a superior tracking sensitivity and is thus best suited for occultation measurements with low tangent point altitudes. The OEM4-G2 and PolaRx2 receivers are likewise shown to properly track dual-frequency GPS signals and normal signal levels and to provide accurate code and carrier phase measurements. Given their limited resource requirements, these receivers appear well suited for precise orbit determination applications and ionospheric sounding onboard of microsatellites with tight mission budgets.

Ka-band direct digital receiver

A new direct-conversion wideband (26-28.5 GHz) six-port receiver is proposed for mass-market wireless communications. This six-port receiver is designed to operate without the need for precise power reading and the use of a digital signal processor that is usually required in other receivers. The proposed receiver architecture is chosen to satisfy requirements of hardware receivers used in high-speed QPSK communications. The receiver contains a receiver front-end, QPSK demodulator, and carrier recovery module. A reverse modulation loop was used to provide a rapid carrier recovery. The maximum bit rate is determined solely by the limiting speed of the baseband module. This new hardware receiver is proposed as a robust, rugged, low-cost receiver for use in wide Ka-band wireless mass-market QPSK communications such as local multipoint distribution system services, which is a prime example of communication equipment requiring such receivers. Bit-error-rate results are presented versus the noise and reference signal phase shift.

Adaptive detector arrays for optical communications receivers

An optimal adaptive array receiver for use in groundbased optical communications is investigated. Kolmogorov phase screen simulations are used to generate realistic focal-plane distributions of the received optical fields in the presence of turbulence. The array detection concept reduces interference from background radiation by effectively assigning higher confidence levels at each instant of time to those detector elements that contain significant signal energy and suppressing those that do not. A simpler suboptimum structure that replaces the continuous weighting of the optimal receiver by a hard decision over each detector element is also described. It is shown that, for photon counting receivers observing Poisson distributed signals, performance improvements of up to 5 dB can be obtained over conventional single-detector photon counting receivers when observing turbulent optical fields in high background environments.