Receiver Chain Research Articles

Total electron content disturbances during minor sudden stratospheric warming, over the Brazilian region: A case study during January 2012

AbstractThe effects of sudden stratospheric warming (SSW) on ionosphere have been investigated by several scientists, using different observational techniques and model simulations. However, the minor SSW event during January 2012 is one of those that are less studied. Influences of several types of possible drivers—minor SSW event, changing solar flux, moderate geomagnetic storm on 22–25 January, and one of the largest solar proton events on 23–30 January—make it a challenging period to interpret. In the present study, the GPS‐total electron content (TEC) measurements from a network of 72 receivers over the Brazilian region are considered. This network of 72 GPS‐TEC locations lies between 5°N and 30°S (35°) latitudes and 35°W and 65°W (30°) longitudes. Further, two chains of GPS receivers are used to study the response of the equatorial ionization anomaly (EIA) in the Brazilian eastern and western sectors, as well as its day‐to‐day variability before and during the SSW‐2012. It was noted that the TEC is depleted to the order of 30% all over the Brazilian region, from equator to beyond the EIA regions and from east to west sectors. It is also noticed that the EIA strengths at the east and west sectors were weakened during the SSW‐2012. However, the Brazilian eastern sector was found to be more disturbed compared to the western sector during this SSW‐2012 event.

Scenario-Aware Dynamic Power Reduction Using Bias Addition

Typical modern communication systems operate over a wide dynamic range of signal strengths. We consider the approach of adding a bias as offset to reduce switching activity, and study the average bit toggle for signals with different distributions, as a function of signal span and the actual bias value added. From the analysis, we provide guidelines to choose an optimal bias value, based on the system scenario, to obtain the lowest power consumption. Simulation results confirm the accuracy of the theoretical analysis. Various finite-impulse response filter architectures are evaluated, and we propose suitable enhancements to them to enable improved power savings. We apply the bias addition technique and the proposed architectural enhancements to a wireless local area network digital receiver chain, and demonstrate that over 25% power savings can be achieved under different signal conditions.

An Approximate Zero IF FM-UWB Receiver for High Density Wireless Sensor Networks

A low-power frequency modulated-ultra-wideband (FM-UWB) receiver for short-range communications, capable of simultaneously demodulating multiple FM-UWB signals located at the same frequency, is presented in this paper. The proposed receiver utilizes an “approximate zero IF” architecture that uses a low-power, free-running ring oscillator as the RF LO to first convert the input signal into baseband, where it is then amplified and demodulated. Moving the most power-hungry blocks from RF to IF results in reduction of power consumption by more than one order of magnitude compared to previous implementations using the delay-line demodulator. Integrated in a 65-nm CMOS technology, the whole receiver chain consumes 423 $\mu \text{W}$ from a 1-V supply while achieving −70-dBm sensitivity at a data rate of 100 kb/s at 4 GHz. Communication with up to four FM-UWB users, operating in the same band, is demonstrated, making this receiver suitable for high-density wireless sensor networks.

On the Analog Self-Interference Cancellation for Full-Duplex Communications With Imperfect Channel State Information

This paper studies the performance of the analog multi-tap (MT) canceller, where the tap coefficients are calculated based on the estimated self-interference (SI) channel state information (CSI). In this paper, both the time-invariant and the time-varying SI channels scenarios are investigated, considering the dynamic range of the analog-to-digital converter (ADC) and the linearity of the receiver chain. Closed-form expressions are first developed to calculate the residual SI power after the MT cancellation, characterizing the joint effects of the imperfect SI CSI, reconstruction errors on the estimated SI CSI, and the variation of the SI channels. Then, the achievable rate of the full-duplex transceivers is derived as a function of the residual SI power after the MT cancellation, dynamic range of the ADC, and the linearity of the receiver chain. Theoretical and simulated results show that with imperfect SI CSI, deploying more taps may harm the amount of analog SI cancellation. The sensitivity of the canceller to the doppler frequency shift reduces the amount of analog SI cancellation, and thus brings rate gain loss even with a doppler negligible in conventional communications.

Challenges in Clock Synchronization for On-Site Coding Digital Beamformer

Typical radio frequency (RF) digital beamformers can be highly complex. In addition to a suitable antenna array, they require numerous receiver chains, demodulators, data converter arrays, and digital signal processors. To recover and reconstruct the received signal, synchronization is required since the analog-to-digital converters (ADCs), digital-to-analog converters (DACs), field programmable gate arrays (FPGAs), and local oscillators are all clocked at different frequencies. In this article, we present a clock synchronization topology for a multichannel on-site coding receiver (OSCR) using the FPGA as a master clock to drive all RF blocks. This approach reduces synchronization errors by a factor of 8, when compared to conventional digital beamformer.

A Simple Algorithm for Specs Definition in Wireless Receivers

This paper presents a system-level design procedure for wireless receivers, which allows an optimum distribution of the specifications-per-stage along the receiver. The main idea hereby developed is to start from a specific set of requirements (given by the selected telecommunications standards) in terms of bit-error-rate (BER) and blocker mask scenario in frequency domain, and to finally achieve a certain set of specifications for each stage in the receiver chain (i.e., LNA, mixer, baseband and ADC). The proposed system-level design algorithm allows fixing the receiver specifications-per-stage with a reduced set of equations and successive iterations. Moreover, an optimum design for baseband section (i.e., complex filter and the ADC) is also found, by achieving an optimum trade-off between filter order and ADC equivalent-number-of-bits (ENOB). In order to validate the hereby proposed algorithm, a low-energy Bluetooth low-IF receiver has been modeled and simulated (by Simulink), and extensive time-domain simulation results have been provided, complying with the expected Bluetooth standard signal-to-noise-and-distortion ratio (SNDR).

Spatio-Temporal Waveform Design for Multiuser Massive MIMO Downlink With 1-bit Receivers

Internet-of-Things (IoT) refers to a high-density network of low-cost low-bitrate terminals and sensors where also low energy consumption is one central feature. As the power-budget of classical receiver chains is dominated by the high-resolution analog-to-digital converters (ADCs), there is a growing interest towards deploying receiver architectures with reduced-bit or even 1-bit ADCs. In this paper, we study waveform design, optimization and detection aspects of multi-user massive MIMO downlink where user terminals adopt very simple 1-bit ADCs with oversampling. In order to achieve spectral efficiency higher than 1 bit/s/Hz per real-dimension, we propose a two-stage precoding, namely a novel quantization precoder followed by maximum-ratio transmission (MRT) or zero-forcing (ZF) type spatial channel precoder which jointly form the multi-user-multiantenna transmit waveform. The quantization precoder outputs are optimized, under appropriate transmitter and receiver filter bandwidth constraints, to provide controlled inter-symbol-interference (ISI) enabling the input symbols to be uniquely detected from 1-bit quantized observations with a low-complexity symbol detector in the absence of noise. An additional optimization constraint is also imposed in the quantization precoder design to increase the robustness against noise and residual inter-user-interference (IUI). The purpose of the spatial channel precoder, in turn, is to suppress the IUI and provide high beamforming gains such that good symbol-error rates (SERs) can be achieved in the presence of noise and interference. Extensive numerical evaluations illustrate that the proposed spatio-temporal precoder based multiantenna waveform design can facilitate good multi-user link performance, despite the extremely simple 1-bit ADCs in the receivers, hence being one possible enabling technology for the future low-complexity IoT networks.

8-GHz, 6.6-mW LC-VCO with Small Die Area and FOM of 204 dBc/Hz at 1-MHz Offset

This letter discusses the design of an 8-GHz LC-tank voltage-controlled oscillator (VCO) for use in a receiver chain developed for the Cerro Chajnantor Atacama Telescope Heterodyne Array Instrument. A VCO-optimization approach is proposed that reduces the phase noise (PN) and minimizes the VCO die area. An LC-VCO is realized in a 0.13- $ {\mu }\text {m}$ CMOS technology to validate the design methodology experimentally. The VCO achieves a worst-case PN, within the whole tuning range of 850 MHz, of -131 dBc/Hz at a 1-MHz offset. At 8 GHz the oscillator PN is measured to be -134.3 dBc/Hz at a 1-MHz offset achieving a figure of merit (FOM) of 204 dBc/Hz.

All-Digital Self-Interference Cancellation Technique for MIMO Full-Duplex Systems

In this paper, the MIMO full-duplex system is proposed to remove self-interference signal using modified DFT based channel estimation technique. In SISO full-duplex systems only single transceiver can transmit data on either side simultaneously whereas in MIMO full-duplex systems multiple transceivers can transmit data simultaneously from both sides. During MIMO full-duplex transmission selfinterference and circuit impairments may occur, to avoid such noises digital cancellation technique is used which is a lowest complexity self-interference cancellation technique in all fullduplex systems. In this technique receiver auxiliary chain and its copy circuit called ordinary receiver chain is used to cancel out the both self-interference and its circuit impairments. Noise added during wireless channel is suppressed by using passive suppression technique and Gaussian noise, phase noise and quantization noise is eliminated by the active cancellation technique. So, combination of active cancellation and passive suppression techniques are used to eliminate the circuit impairments. The proposed channel estimation technique is used to cancel out the self-interference produced at the output of both auxiliary and ordinary receiver chains. By using digital self-interference cancellation technique the amount of self-interference cancelled is 37dBm higher than the receiver noise floor. The achievable rate and throughput of MIMO full-duplex system is 28 bits/sec/Hz and 1049.04 Mbps respectively which is very large when compared to MIMO half-duplex , SISO full-duplex and SISO half-duplex systems. General Terms QAM, OFDM, Modified DFT based channel estimation, Digital cancellation.

EVALUATION OF INTEGRATED ANALOG RC FILTER STRUCTURES FOR MULTISTANDARD TRANSCEIVERS / INTEGRINIŲ ANALOGINIŲ RC FILTRŲ STRUKTŪRŲ DAUGIASTANDARČIAMS SIŲSTUVAMS-IMTUVAMS TYRIMAS

Multistandard transceivers usually have high order low pass filters in their receiver chains. Different filter topologies may have various component variation tolerances and different output noise. In this work, three 6th order filter with different topologies are analyzed for use in multistandard transceivers. Filters are designed in 0.18 µm and 65 nm CMOS technologies and simu-lated using Cadence software. The results show, that the filter frequency response variation in integrated circuits does not de-pend on the filter topology. Simulation results also show that the Leapfrog filter topology has the smallest integrated output noise in the filter bandwidth and is most suited for low noise applications. Daugiaustandarčiuose siųstuvuose-imtuvuose naudojami aukštesnės eilės žemųjų dažnių filtrai. Skirtingos filtrų struktūros gali būti nevienodai jautrios jas sudarančių elementų nuokrypiams ir daryti skirtingą įtaką daugiastandarčių siųstuvų-imtuvų triukšmams. Darbe pateikti trijų šeštosios eilės skirtingų struktūrų aktyviųjų RC filtrų, skirtų daugiaustandarčiams siųstuvams-imtuvams, tyrimo rezultatai. Filtrų struktūros modeliuojamos naudojant 0,18 μm ir 65 nm KMOP integrinių grandynų gamybos technologijas ir Cadence Virtuoso programinę įrangą. Iš imitacijos rezultatų matyti, kad moderniose integrinių grandynų technologijose filtrų dažninių amplitudės charakteristikų (DACh) parametrų nuokrypis beveik nepriklauso nuo filtro struktūros. Tarp analizuotų filtrų struktūrų mažiausia praleidžiamųjų dažnių juostoje integruota išėjimo triukšmo vidutinė kvadratinė vertė gaunama naudojant šuolinių grįžtamųjų ryšių struktūros filtrus.

Mitigating adjacent channel interference in vehicular communication systems

In the last few decades, dedicated wireless channels were specifically allocated to enable the development and implementation of vehicular communication systems. The two main protocol stacks, the WAVE standards proposed by the IEEE in the United States and the ETSI ITS-G5 in Europe, reserved 10MHz wide channels in the 5.9GHz spectrum band. Despite the exclusive use of these frequencies for vehicular communication purposes, there are still cross channel interference problems that have been widely reported in the literature. In order to mitigate these issues, this paper presents the design of a two-stage FIR low-pass filter, targeting the integration with a digital baseband receiver chain of a custom vehicular communications platform. The filter was tested, evaluated and optimized, with the simulation results proving the effectiveness of the proposed method and the low delay introduced in the overall operation of the receiver chain.

Passive compression technique applied to UWB beamforming and imaging architectures

Recent works have demonstrated the feasibility of microwave imaging using compressive techniques, exempting the use of active delay lines, phase shifters, or moving parts to achieve beamforming. With this method, waves are coded in a passive way by a compressive device to reduce the complexity of the transmitter and/or receiver chains of the telecommunication and radar systems requiring beamsteering. Such a technique is based on the exploitation of the frequency diversity, implying that a reduction of the compressive device's volume imposes a diminution of the number of driven antennas. In this paper, the improvement brought by simultaneous excitations of the compressive device is presented. Adapting a new mathematical formulation, it is shown that M inputs can send independent waveforms allowing the beamsteering of an N-elements antenna array, while maintaining N > M.

Instrumentation of the basic finner reference projectile for attitude measurements at supersonic velocities

The instrumentation of a reference projectile basic finner (BF) of caliber 28 mm is presented. This miniaturized electronic is very convenient for short distance firings and can withstand accelerations of about 10,000 g. Associated to an software defined radio (SDR) reception chain, it offers great flexibility. Examples of firing data are given as well as calibrated results. This instrumentation has been successfully used for 6 DoF analysis of the ballistic attitude in postprocessing. Furthermore, the onboard electronics can also be used in combination with a real-time processing unit for the in-flight computation of the attitude angles of the projectile.

Instrumentation of the basic finner reference projectile for attitude measurements at supersonic velocities

The instrumentation of a reference projectile basic finner (BF) of caliber 28 mm is presented. This miniaturized electronic is very convenient for short distance firings and can withstand accelerations of about 10,000 g. Associated to an software defined radio (SDR) reception chain, it offers great flexibility. Examples of firing data are given as well as calibrated results. This instrumentation has been successfully used for 6 DoF analysis of the ballistic attitude in postprocessing. Furthermore, the onboard electronics can also be used in combination with a real-time processing unit for the in-flight computation of the attitude angles of the projectile.

Time-Divided Spread-Spectrum Code-Based 400 fW-Detectable Multichannel fNIRS IC for Portable Functional Brain Imaging

A custom tranceiver IC is designed to implement a portable brain imaging system based on functional near-infrared spectroscopy (fNIRS). The fNIRS IC generates multichannel time-divided spread-spectrum codes (TDSSCs) and drives light-emitting devices in the transmitter (Tx) chain, and performs optimum filtering, quantization, and serialization in the receiver (Rx) chain. A dual slope ADC subsequent to an operational transconductance amplifier-C-based matched filter shares a capacitor to save area while achieving optimum signal-to-noise ratio (SNR) in the brain channel. The Rx chain including an off-chip TIA ensures sufficient electrical SNR irrespective of the brain region for the accurate extraction of hemodynamic response. The minimum detectable light power of the Rx chain is 400 fW. The output power of the Tx is made adjustable by controlling the occurrence rate and the power of the TDSSC to reduce subject-dependent measurement variations. The proposed fNIRS system measures 42 brain regions simultaneously, and the experimental results clearly verify the validity of the proposed portable fNIRS system.

Energy-Recycling Full-Duplex Radios for Next-Generation Networks

In this work, a novel energy-recycling single-antenna full-duplex (FD) radio is designed, in which a new 3-port element including a power divider and an energy harvester is added between the circulator and the receiver (RX) chain. The presence of this new element brings advantages over the state of the art in terms of both spectral efficiency and energy consumption. In particular, it provides the means of performing both an arbitrary attenuation of the incoming signal, which in turn increases the effectiveness of the state-of-the-art self-interference cancellation strategies subsequently adopted in the RX chain, and the recycling of a non-negligible portion of the energy leaked through the non-ideal circulator. The performance of this architecture is analyzed in a practically relevant 4-node scenario in which 2 nodes operate in FD and 2 nodes in half-duplex (HD). Analytical approximations are derived for both the achievable rates of the transmissions performed by the FD and HD radios and the energy recycled by the FD radios. The accuracy of these derivations is confirmed by numerical simulations. Quantitatively, achievable rate gains up to 40% over the state-of-the-art alternatives, in the considered scenario, are highlighted. Furthermore, up to 50% of the leaked energy at the circulator, i.e., 5% of the energy of the transmitted signal, can be recycled.

Day‐to‐day variability of equatorial electrojet and its role on the day‐to‐day characteristics of the equatorial ionization anomaly over the Indian and Brazilian sectors

AbstractThe equatorial electrojet (EEJ) is a narrow band of current flowing eastward at the ionospheric E region altitudes along the dayside dip equator. Mutually perpendicular electric and magnetic fields over the equator results in the formation of equatorial ionization anomaly (EIA), which in turn generates large electron density variabilities. Simultaneous study on the characteristics of EEJ and EIA is necessary to understand the role of EEJ on the EIA variabilities. This is helpful for the improved estimation of total electron content (TEC) and range delays required for satellite‐based communication and navigation applications. Present study reports simultaneous variations of EEJ and GPS‐TEC over Indian and Brazilian sectors to understand the role of EEJ on the day‐to‐day characteristics of the EIA. Magnetometer measurements during the low solar activity year 2004 are used to derive the EEJ values over the two different sectors. The characteristics of EIA are studied using two different chains of GPS receivers along the common meridian of 77°E (India) and 45°W (Brazil). The diurnal, seasonal, and day‐to‐day variations of EEJ and TEC are described simultaneously. Variations of EIA during different seasons are presented along with the variations of the EEJ in the two hemispheres. The role of EEJ variations on the characteristic features of the EIA such as the strength and temporal extent of the EIA crest has also been reported. Further, the time delay between the occurrences of the day maximum EEJ and the well‐developed EIA is studied and corresponding results are presented in this paper.

A Wideband Beamforming Lowpass Filter for 60 GHz Phased-Array Receivers

This paper presents an analog baseband beamforming topology, which combines phase shifting, signal combination, and biquadratic lowpass filtering in one block. This reduces the number of stages cascaded in a receiver chain, leading to a shorter signal path, thus improving the dynamic range. Flexibility of the proposed solution is illustrated with different possible implementations depending on the top-level chip floorplan. It is shown that the proposed structure does not introduce extra power consumption compared to the conventional approach, while obtaining a higher SNR. A four-antenna-path version of the proposed topology is implemented in 40 nm low-power CMOS as a prototype together with a variable gain block forming a complete analog baseband section for a phased-array receiver. The functionality includes beamforming with a resolution better than 6.8 degrees, fourth-order lowpass filtering with a 1 GHz cutoff frequency, variable gain between 10.6 and 30 dB and automatic DC offset compensation. Output IP3 above 10 dBm and output noise below 4.2 mVrms over the whole gain range yield an SFDR larger than 31.2 dB, which is sufficient for 16-QAM modulation according to IEEE 802.11ad. The circuit consumes between 30 and 42 mW.

MIMO 수중 통신에서 도착시간 차이에 따른 보상 알고리즘

In this paper, we proposed receiver structure based on an iterative turbo equalization to cope with phase difference between two sensors in MIMO underwater communication channel. In a space-time coded system, it is often assumed that there are no phase errors among the multiple transmitter and receiver chains. In this paper, we have studied the effect of the phase errors between different transmit sensors and different propagation paths in the environment of MIMO underwater communication system, and have shown through BER performance by computer simulations that the bit-error-rate performance can be severely degraded. A decision-directed estimation and compensation algorithm has been proposed to minimize their effects on the system performance. In this paper, we investigate the phase differences and their effects on multiple-input and multiple-output systems, and propose a compensation algorithm for underwater channel model to minimize their effects. 키워드 : 시공간 격자 부호, 터보 등화기, 수중 음향 통신, DD-Loop, MIMO Key word : Space time trellis code, Turbo Equalization, Underwater acoustic communication, Decision Directed Loop, MIMO(Multiple Input Multiple Output) Journal of the Korea Institute of Information and Communication Engineering 한국정보통신학회논문지(J. Korea Inst. Inf. Commun. Eng.) Vol. 19, No. 7 : 1531~1538 Jul. 2015

A CMOS Delta-Sigma PLL Transmitter with Efficient Modulation Bandwidth Calibration

A delta-sigma $(\Delta\Sigma)$ phase locked loop (PLL) transmitter with an efficient modulation bandwidth calibration technique is proposed in this paper. With the proposed technique, the digital-analog mismatch between digital pre-emphasis filter and PLL is calibrated. The loop filter $RC$ variation is tracked in the first place, and then the variation of the loop gain is calibrated by sensing the magnitude differences of the modulator between DC and ten times of the loop bandwidth. The proposed transmitter has been implemented in 0.18- $\mu{\rm m}$ CMOS technology for GSM/GPRS application. Measurement results show that the maximum RMS phase error of the proposed transmitter is 0.8 $^{\circ}$ . In addition, the measured calibration accuracies for $RC$ and loop gain variations are 0.5% and 0.8%, respectively. By reusing the PLL locking time, 18- $\mu{\rm s}$ calibration time is achieved. Moreover, most parts of the calibration circuitries can be shared with the receiver chain, reducing the circuit complexity overhead.