De-noising of GPS Receivers Positioning Data Using Wavelet Transform and Bilateral Filtering

The need for precise position and navigation aids in many areas of industry is becoming increasingly apparent. There are many errors associated with the navigation solution of the global positioning system (GPS), including satellite ephemeris error, satellite clock error, ionospheric delay, tropospheric delay, multipath, receiver measurement error and selective availability (SA). Noise can create an error between centimeters to several meters. In this paper, the proposed technique applied to smooth noise for GPS receiver positioning data is based upon the analysis of wavelet transform (WT), bilateral filter (BF) and diffusivity function. The WT is a powerful tool of signal processing for its multiresolutional possibilities. BF is a local, non-linear and non-iterative technique. It is applied to approximation subband. We decompose a GPS positioning data into low-frequency and high-frequency components and apply BF on the approximation coefficients and diffusivity function on the detail coefficients at each decomposition level for data smoothing. A single-frequency and low-cost commercial GPS receiver manufactured by Rockwell Company is used to test our method. The experimental results on measurement data demonstrate the effectiveness of the proposed method; so that the total root mean square (RMS) error reduces to less than 0.29 m with SA on and 0.15 m with SA off using Daubechie wavelet.     

基于双BP神经网络的室内可见光定位算法

为提高室内可见光定位的精度,提出了一种基于双反向传播(BP)神经网络的单发光二极管(LED)灯室内定位算法.首先在定位区域内使用BP神经网络确定待测目标粗略的位置范围,然后以该位置范围为限制条件,再次使用BP神经网络实现更精确的定位.室内定位系统采用单个LED灯作为发射器,3个水平光电探测器作为接收器接收光功率,避免了...     

Neural Technologies for Precise Timing in Electric Power Systems with a Single-Frequency GPS Receiver

The global positioning system (GPS), with its ability to provide time synchronization with accuracy to 200 ns over the wide area, provides an ideal tool for performing time tagging in electric power systems. The observed GPS pseudo-range varies from the true range because of range measurement errors. GPS errors sources are ionospheric delays, atmospheric delays, troposphericelays, multi-path effects and dilution of precision etc., affecting the GPS signals as they travel from satellite to user on Earth. In this paper neural models has been presented are for more accurate GPS timing in electric power systems with a single-frequency GPS receiver. The proposed methods use back-propagation (BP), extended Kalman filter (EKF) and particle swarm optimization (PSO) training algorithms, which achieves the optimal training criterion. We use actual data to evaluate the performance of the proposed methods. An experimental test setup is designed and implemented for this purpose. Results using the three methods are discussed. The experimental results obtained from a coarse acquisition (C/A)-code single-frequency GPS receiver are provided to confirm the efficacy of the approaches to give high accurate timing. The GPS timing RMS error using neural network based on PSO learning algorithm reduces to less than 105 and 36 ns, before and after SA, respectively.     

A 24-channel implantable neural recording based on time and frequency-division multiplexing

This paper presents a novel approach to encapsulate prerecorded neural signals in implantable neural recording microsystems. We have increased the number of channels and the reconstructed neural signal quality in the receiver by combining time-division-multiplexing (TDM) and frequency-division-multiplexing (FDM) method. Reducing the number of channels in each TDM module is the fundamental advantage of this method that leads to reduced crosstalk noise. We evaluate some possible configurations and propose an optimized system that has less power dissipation and area occupation than other configurations. A 24-channel implantable neural recording based on the optimized system is designed in both system and circuit level. In this system, first, channels are divided into three 8-channel groups then after multiplexing in the time domain, they are combined together by FDM method. Finally, a frequency modulator wirelessly transmits neural signals to an external setup. In addition, we adjust local carrier frequencies and the bandwidth of TDM to synchronize detection without transmitting pilot carrier. To justify the system operation, using 0.18 μm CMOS technology, we design the system in circuit level. The designed circuit consumes a power of 1.39 mW at a supply voltage of 1.8 V. This leads to a power consumption of 58 μW per channel.     

Design of an L1 band low noise single-chip GPS receiver in 0.18 μm CMOS technology

This article presents an L1 band low noise integrated global positioning system(GPS)receiver chip using 0.18 μm CMOS technology.Dual-conversion with a low-IF architecture was used for this GPS receiver.The receiver is composed of low noise amplifier(LNA),down-conversion mixers,band pass filter,received signal strength indicator,variable gain amplifier,programmable gain amplifier,ADC,PLL frequency synthesizer and other key blocks.The receiver achieves a maximum gain of 105 dB and noise figure less than 6 dB.The variable gain amplifier(VGA)and programmable gain amplifier(PGA)provide gain control dynamic range over 50 dB.The receiver consumes less than 160 mW from a 1.8 V supply while occupying a 2.9 mm2chip area including the ESD I/O pads.     

Low-power wake-up receiver with subthreshold CMOS circuits for wireless sensor networks

We developed a wake-up receiver comprised of subthreshold CMOS circuits. The proposed receiver includes an envelope detector, a high-gain baseband amplifier, a clock and data recovery (CDR) circuit, and a wake-up signal recognition circuit. The drain nonlinearity in the subthreshold region effectively detects the baseband signal with a microwave carrier. The offset cancellation method with a biasing circuit operated by the subthreshold produces a high gain of more than 100 dB for the baseband amplifier. A pulse-width modulation (PWM) CDR drastically reduces the power consumption of the receiver. A 2.4-GHz detector, a high-gain amplifier and a PWM clock recovery circuit were designed and fabricated with 0.18-μm CMOS process with one poly and six metal layers. The fabricated detector and high-gain amplifier achieved a sensitivity of ?47.2 dBm while consuming only 6.8 μW from a 1.5 V supply. The fabricated clock recovery circuit operated successfully up to 500 kbps.     

Design of a full-band CMOS UWB receiver and fast-hopping carrier generator for 3.1–10.6 GHz

This paper presents an interference rejection full-band UWB receiver and fast hopping carrier generator for 3.1–10.6 GHz. This receiver enables 11 bands of operation by embedding a tunable notch filter to eliminate interferers in a 5 GHz wireless local area network. The carrier generator can cover 3.1–10.6 GHz within less than 9.5 ns. The receiver, based on the proposed multi-band OFDM standard, consists of a zero-IF receive chain and required system noise figure, the receiver linearity specifications of which are discussed in this paper. It consists of a single-ended low-noise amplifier (LNA), a down-conversion mixer, a low-pass filter (LPF), and a programmable gain amplifier with an IO buffer. The LNA employs a common-gate topology of the 1st stage with dual-resonant loads, a cascade amplifier of the 2nd stage for mid-band resonance, and a tunable notch filter. The down-conversion mixer adopts a single-balanced architecture with LO cancellation. The LPF is implemented based on an active RC topology, and implements a four-stage programmable gain amplifier. The receiver dissipates 49.3 mA from a 1.8 V power supply. The average voltage conversion gain of the receiver IC is 73.5 dB, and the system noise figure is 8.4 dB. Input P1dB increases from ?36.8 dBm at 4 GHz to ?30.5 dBm at 10.3 GHz. The attenuation is 8.5 dB, which is achieved in the interference rejection band at 5.2 GHz. It occupies an area of 0.98 × 3.3 mm² including the bond pads.     

A 2.4 GHz ISM-band highly digitized receiver based on a variable gain LNA and a subsampled $$\varSigma \varDelta$$ ADC

In this paper, we present a complete multi-standard receiver based on a variable-gain LNA and an RF subsampled Sigma-Delta ADC. The receiver includes an RF digital down-conversion mixer and a polyphase multistage multi-rate decimation filter. The receiver is measured for 3 different standards in the 2.4 GHz ISM-band. Measurement results show that the receiver achieves 79, 73 and 63 dB of dynamic range for the Bluetooth, ZigBee and WiFi standards respectively. The complete receiver, implemented in 130 nm CMOS process, has a 300 MHz tunable central frequency and consumes 63 mW under 1.2 V supply.     

Real-Time Receiver Clock Jump Detection for Code Absolute Positioning with Kalman Filter

In global navigation satellite systems (GNSS) navigation the receiver and satellite clocks play a key role. The receivers are usually equipped with inaccurate quartz clocks, which experiment large drift relative to system time and consequently offset growing very fast; receiver manufactures bound the magnitude of the receiver clock offset to prevent it becomes too large and the actual bounding procedures vary from one manufacturer to another. The most common approach consists of introducing discrete jumps when the offset exceeds a threshold (usually 1 ms). This method is common in low-cost GNSS receivers and influences several applications as differential positioning, cycle-slip detection, precise point positioning technique, absolute positioning with Kalman filter. In this work some techniques to detect and account for millisecond clock jump, suitable for code positioning of a single receiver with Kalman filter, are proposed. Two deterministic algorithms to detect receiver clock jumps are shown: in measurement and parameter domain. The technique in measurement domain uses current pseudorange measurements compared with pseudorange and Doppler measurements at previous epoch; the technique in parameter domain compares current and previous least squares estimations of receiver clock bias, considering the clock drift. Two different approaches are described to account for the clock jumps, once detected, a deterministic one, consisting of fixing the pseudorange discontinuities, and a statistic one, consisting of suitably varying the Kalman filter settings. A static GNSS data set is processed with and without the proposed algorithms to demonstrate their efficiency.     

Simple 1 MM Receivers with a Fixed Tuned Double Sideband SIS Mixer and a Wideband INP MMIC Amplifier

We report on techniques to broaden the intermediate frequency (IF) bandwidth of the Berkeley‐Illinois‐Maryland Array (BIMA) 1mm Superconductor‐Insulator‐Superconductor (SIS) heterodyne receivers by combining fixed tuned Double Side Band (DSB) SIS mixers and wideband Monolithic Microwave Integrated Circuit (MMIC) IF amplifiers. To obtain the flattest receiver gain across the IF band we tested three schemes for keeping the mixer and amplifier as electrically close as possible. In Receiver I, we connected separate mixer and MMIC modules by a 1 ″ stainless steel SMA elbow. In Receiver II, we integrated mixer and MMIC into a modified BIMA mixer module. In Receiver III, we devised a thermally split block in which mixer and MMIC can be maintained at different temperatures–in this receiver module the mixer at 4 K sees very little of the 10–20 mW heat load of the biased MMIC at 10 K. The best average receiver noise we achieved by combining SIS mixer and MMIC amplifier is 45 ‐50 K DSB for ν_LO = 215–240 GHz and below 80 K DSB for ν_LO = 205 ‐ 270 GHz. Over an IF frequency band of 1 – 4 GHz we have demonstrated receiver DSB noise temperatures of 40 – 60 K. Of the three receiver schemes, we feel Receiver III shows the most promise for continued development.     

基于PIR的三角交叉定位技术研究

摘要：由于单个PIR构成的单节点探测视场存在大量的探测盲区,盲区所占面积相对较大,不能对目标实施有效定位,定位误差基本上达到1.5-2.5m左右,基于此,提出了三角交叉定位技术研究。文中采用位于同一平面内的三个节点,对同样位于同一平面的目标进行交叉定位,经过实验验证,目标定位误差可以减小到1m以内,定位精度得到了一定程度的提高,具有一定的实际应用价值。     

A 6 mW 750 MHz anti-aliasing filter for receiver analog front-end

A low power high speed continuous-time filter for receiver application in standard 90 nm CMOS process is presented. A biquad cell based on the open-loop topology is implemented. Besides, a differential voltage buffer with additional gain boost, high linear voltage-to-voltage conversion and low output impedance is introduced. In this work, a fourth-order filter is implemented. Simulation results show the 750 MHz cutoff frequency with less than ?50 dB IM3 for a 300 mVpp input. The power consumption for this filter is 6 mW at a 1.2-V supply.     

光学双向反射分布函数的测量装置研究

介绍了双向反射分布函数的测量原理和方法,搭建了双向反射分布函数的测量装置。该装置可以测量可见光和红外两个波段的双向反射分布函数。在可见光波段采用卤钨灯作为光源,采用光纤光谱仪作为光接收器,以10 nm的波长间隔测量双向反射分布函数。在红外波段采用碳化硅作为红外光源,采用热释电探测器作为光接收器,采用标准板相对定标的方法测量待测样板的双向反射分布函数。可见光波段双向反射分布函数的测量重复性不大于1.5%;3μm~5μm红外波段双向反射分布函数的测量重复性分别小于或等于2.5%、8μm~12μm波段的小于或等于3.0%。测量结果表明,该测量装置的有效性较高。     

A new method for improving Wi-Fi-based indoor positioning accuracy

Wi-Fi- and smartphone-based positioning technologies are playing a more and more important role in location-based service industries due to the rapid development of the smartphone market. However, the low positioning accuracy of these technologies is still an issue for indoor positioning. To address this problem, a new method for improving the indoor positioning accuracy was developed. The new method initially used the nearest neighbour (NN) algorithm of the fingerprinting method to identify the initial position estimate of the smartphone user. Then two distance correction values in two roughly perpendicular directions were calculated by the path loss model based on the two signal strength indicator values observed. The systematic error from the path loss model were eliminated by differencing two model-derived distances from the same access point. The new method was tested and the results compared and assessed against that of the commercial Ekahau RTLS system and the NN algorithm. The preliminary results showed that the positioning accuracy has been improved consistently after the new method was applied and the root mean square accuracy improved to 3.3 m from 3.8 m compared with the NN algorithm.     

室内外行人导航系统研究

采用微机电系统(MEMS)惯性传感器、MEMS磁传感器及小型全球定位系统(GPS)接收机为室内外行人导航数据源,基于Cortex-M4为内核,搭建了室内外行人导航系统硬件平台。重点研究了多传感器导航系统的结构、多源信息融合方法、多条件零速检测方法及零速修正等理论方法。并通过试验,采集实测数据进行分析、验证行人导航系统设计的性能。结果表明,在GPS信号良好情况下,定位误差在2.5m以内;无GPS信号期间,路线长度为110m时,定位误差在总路经的5%内。     

平台侧位置指纹定位系统中接收端问题的优化

当前室内位置指纹定位系统主要用于对移动端的定位.借鉴其定位机理,研究了对无线电发射端的定位,属于平台侧位置指纹定位系统.从部署接收端的位置以减小定位误差的角度出发,提出了增大参考点之间欧式距离确定接收端位置的方案.同时,提出利用覆盖率的概念确定定位区间的接收端个数以满足区间定位的需求.建立了接收端位置及个数优化问题的数学模型,并用遗传算法和全覆盖原则对优化问题进行求解,给出了优化问题的实现流程.针对不同空间,对优化问题进行了仿真,比较了经验布置接收端和优化布置接收端的定位结果误差及接收端是否满足全覆盖的定位结果误差,验证了所提方法的合理性,对定位前部署接收端的个数和位置有一定的指导意义.     

Current-mode analogue interface for high-speed low-current differential signalling

In this work, we propose high-speed low-current differential signalling (LCDS) over an electrical chip-to-chip interconnect by using a common-gate transimpedance amplifier followed by a common-source TIA stage. LCDS uses a current-mode receiver compared to a conventional voltage-mode receiver used in most of the signalling technologies such as low-voltage differential signalling, voltage-mode signalling and current-mode logic. The minimum detectable signal level possible with a current-mode receiver for the targeted bit-error rate (BER) makes LCDS an attractive choice. Also the input impedance of the LCDS receiver can be made equal to 100 Ω differential for matching the characteristic impedance of electrical chip-to-chip interconnect. The complete design, analysis and noise characterisation of the TIA front-end is presented. The CGCSTIA is implemented in 1.8 V, 0.18 μm digital CMOS technology. The input-referred noise current and 3-dB bandwidth of the receiver are 1.57 μA and 5.75 GHz, respectively. For the targeted BER of 10^?12, a data transfer rate of 6 Gb/s is achieved, while transmitting the data over a FR4 PCB trace of length 20 cm. The power dissipated in the current-mode receiver is 3.6 mW.     

基于反向学习策略的自适应花授粉接收信号强度指示室内可见光定位

为提高大型室内场所的定位精度,提出一种基于改进自适应花授粉算法的接收信号强度指示(RSSI)可见光定位方案。利用固定在屋顶呈网格型排布的LED发送位置信息,接收端采用基于反向学习策略和自适应花授粉算法的RSSI定位方法实现精确定位。传统花授粉算法具有易陷入局部最优、缺乏变异机制等缺点,利用反向学习策略可使初始种群分布更加均匀,通过提高种群多样性可使算法跳出局部最优;采用有利于全局广泛搜索的自适应移动因子提高收敛速度。在100 m×100 m×100 m大型室内场所的一层100 m×100 m×10 m的空间中,考虑热噪声和散射噪声干扰的情况,经过多次仿真可得,相比于传统定位算法,随机灯排布下采用改进花授粉的RSSI算法的定位误差小于±1 cm;采用网格型灯排布结合改进定位算法的室内可见光定位系统时,定位精度得到明显提升,定位时间大幅缩短。该方案具有定位精度更高、计算速度更快、工作稳定等优点。     

Design of Ka-band Monolithic Image Rejection Mixer

In this paper, a 30–40 GHz monolithic image rejection mixer is described. The mixer employs two drain LO injection mixer cells, which can perform well even with zero drain bias voltage. Also it employs Lange Coupler for RF quadrature signal generation. The mixer is fabricated by a commercial 0.18-μm pseudomorphic high electron-mobility transistor (pHEMT) process. It achieves image rejection ratio of more than 20.4 dB and conversion loss of less than 12.6 dB in the frequency range of 30 to 38 GHz.     

Bayesian Fusion for Indoor Positioning Using Bluetooth Fingerprints

This paper studies the use of received signal strength indicators (RSSI) applied to fingerprinting method in a Bluetooth network for indoor positioning. A Bayesian fusion (BF) method is proposed to combine the statistical information from the RSSI measurements and the prior information from a motion model. Indoor field tests are carried out to verify the effectiveness of the method. Test results show that the proposed BF algorithm achieves a horizontal positioning accuracy of about 4.7 m on the average, which is about 6 and 7 % improvement when compared with Bayesian static estimation and a point Kalman filter method, respectively.