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本文介绍一种数字可编程射频锁相源的设计,及其在IS-95标准的码分多址(CDMA)移动通信系统中的应用,它由电荷泵型的数字频率合成器,无源三阶环路滤波器,以及压控振荡器构成。作为CDMA移动通信系统本振源,为其提供射频上/下变频器和中频调制/解调器的本振信号、以及基带部分的参考基准信号,具有低相噪、低工作电压、低功耗的特点。文中还给出了使用LMX2332A/LM2337双环数字频率合成器研制的锁相振荡源的实例及其测试结果,其相位噪声在偏离载频10kHz处,均优于-92dBc。 相似文献
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1 IntroductionFortheMC CDMAmobilecommunicationsys tembasedonorthogonalfrequencydivisionmulti plexing ,thesynchronizationofthecarrierfrequencyatthereceivermustbeperformedveryaccurately ,ortherewillbealossoforthogonalityamongthesymbolsandamongthesub channe… 相似文献
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Data are presented which reveal a time synchronization error in CDMA (code division multiple access) spread-spectrum networks where mutual signal phase coherence is high among communicators. The error is not white noise but is, in fact, periodic with an amplitude, phase, and mean offset which appears to be related to a mixture of the carrier frequency, chip rate, and code frame rate. This periodicity is more evident as carrier and code phase coherence increases among participants in a network and high tracking accuracy is the goal. This has implications for future high-rate data communications and navigation networks in which errors may be attributed to local oscillator instabilities more than a transmission link. The data using a commercial modem suggest that improvements in local oscillator stabilities will improve coherence among network participants but will not necessarily reduce time synchronization errors 相似文献
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针对高速移动通信系统大多普勒频偏和导频资源受限条件下的载频同步问题,提出了一种级联递进载波同步方法。首先利用数据帧首尾导频块估计与校正接收信号多普勒频率变化率;然后设计了基于多级自相关运算的高精度多普勒频偏估计模型;最后采用三阶锁相环跟踪剩余的多普勒变化率和频率偏移。仿真结果表明,该方法多普勒频率变化率校正满足载波同步需求,具有较高的多普勒频偏估计精度和较低的解调误码率。 相似文献
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Jing Lei Tung-Sang Ng 《Broadcasting, IEEE Transactions on》2003,49(4):335-343
Due to its high-performance broadcast capability, M-ary phase-shift-keying (MPSK) direct sequence code division multiple access (DS/CDMA) technique is widely used in terrestrial and satellite communications to provide wired/wireless services such as audio broadcasting, video broadcasting and high-speed data transmission. However, both coherent and noncoherent MPSK modulation schemes are sensitive to the carrier frequency offset (CFO) incurred by transceiver oscillator instability and/or Doppler shift. In this paper, a nondata-aided and nonphase-based automatic frequency control (AFC) method for MPSK DS/CDMA transceivers is proposed. Different from phase-based AFC approaches, which utilize the frequency-offset-induced phase rotation and suffer from the modulo- 2/spl pi/ phase ambiguity, the proposed method exploits the frequency-offset-induced power degradation and has a wide tracking range of twice the symbol rate, which is independent of the phase keying number as well as the spreading code length. To shorten the tracking time of AFC, the improved steepest descent algorithm and the reshaped S curve are employed. Due to its wide tracking range, short tracking time and low implementation complexity, the proposed AFC method is attractive for terrestrial and satellite-based digital broadcasting. 相似文献
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由于发射和接收机振荡器的不稳定或/和信道的多普勒效应,使载波同步与补偿成为QAM信号接收的关键环节。针对非协作通信中各类载波同步算法只能校正较小的频率偏移的局限,根据QAM信号的基本特点,利用传输符号的统计独立特性,提出了一种新的数字载波频率估计方法。该算法采用开环方式,不需要导频数据,可以估计较大的频率偏移;没有反馈环路,复杂度低,实现起来比较简单。同时,该算法作适当改进,可以直接用于载波的估计。计算机仿真结果表明:该算法可以较好地对各种QAM信号中存在的较大频率偏移进行估计并做补偿;适当改进后可以直接用于估计载波频率,估计效果良好有效。 相似文献
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The performance and application of an optical heterodyne receiver which uses a carrier recovery demodulator are described. Phase sensitive demodulators used in coherent optical transmission are compared, and the suppression of both phase noise and frequency instability of light sources by a carrier recovery (CR-) demodulator is described. A carrier recovered PSK (CR-PSK) demodulator and a phase noise canceling circuit (PNC) for a coherent SCM receiver are introduced as examples of CR-demodulators. The relationship between laser diode spectral linewidths and the delay time difference between the two paths in the CR-PSK demodulator necessary to keep the system performance within a certain power penalty is then derived. In a preliminary experiment using 560-Mb/s CR-PSK transmission, a receiver sensitivity of -51.6 dBm was obtained, and a laser phase noise suppression of about 1/2 that of DPSK was confirmed. The results suggest the possibility of constructing a heterodyne receiver which has no AFC-loop. Applications of a CR-demodulator to an optical frequency division multiplexing (OFDM) system and to a multivalue modulation scheme are discussed 相似文献
8.
Lim K. Lee S.-H. Min S. Ock S. Hwang M.-W. Lee C.-H. Kim K.-L. Han S. 《Solid-State Circuits, IEEE Journal of》2006,41(11):2408-2416
This paper describes a fully integrated zero-IF receiver for cellular CDMA and GPS applications. The single-chip zero-IF receiver integrates the entire signal path for CDMA and GPS bands, including a low-noise amplifier (LNA), I/Q down-converters, baseband channel selection filters (CSFs), a voltage-controlled oscillator (VCO), and a local oscillator (LO) distribution circuit for each band. The cellular-band LNA achieves a noise figure (NF) of 1.2 dB, input third-order intercept point (IIP3) of 11 dBm, and gain of 15.5 dB. Cellular I/Q down-converter and baseband circuitries show 9-dB composite NF, 9 dBm IIP3 and 60-dBm input second-order intercept point (IIP2) without IIP2 calibration. The measured LO leakage is less than -110 dBm at LNA input. The phase noise of the cellular VCO is -134 dBc/Hz at 900-kHz offset with 1.76-GHz carrier frequency. Total GPS signal path achieves NF of 1.7 dB and gain of 74 dB with 42-mA current. The receiver is fabricated in a 0.35-mum SiGe BiCMOS process and packaged in a 6 mm times 6 mm 40-pin micro-lead-frame. Handset measurements report that the receiver meets or exceeds all of the CDMA-2000 requirements 相似文献
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Glisic S.G. Talvitie J.J. Kumpumaki T. Latva-aho M. Iinatti J.H. Poutanen T.J. 《Selected Areas in Communications, IEEE Journal on》1996,14(9):1796-1808
The performance analysis of a new concept of a code-division multiple-access (CDMA) based low Earth orbit (LEO) satellite network for mobile satellite communications is presented and discussed. The starting point was to analyze the feasibility of implementing multisatellite and multipath diversity reception in a CDMA network for LEO satellites. The results are used to specify the design parameters for a system experimental test bed. Due to the extremely high Doppler, which is characteristic of LEO satellites, code acquisition is significantly simplified by using a continuous wave (CW) pilot carrier for Doppler estimation and compensation. The basic elements for the analysis presented are: the channel model, the pilot carrier frequency estimation for Doppler compensation, and multipath and multisatellite diversity combining 相似文献
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《Microwave Theory and Techniques》1978,26(12):945-951
A 1.6-Gb/s 16-level superposed APSK modem using a newly developed baseband signal-processing coherent demodulator is described. ln the modulator, the superposing modulation method is adopted in which two QPSK carriers having different levels are superposed so that the combined signal forms a 16-level APSK carrier. Sixteen signal points are arranged in lattice form on the signal space. In the demodulator, a newly developed carrier recovery loop is adopted in which quantizing error signals are detected in the process of data regeneration; they are used for generating the phase error signal to control a VCO. The principles of operation and theoretical analysis of this carrier recovery loop is described, through which it is shown that the recovered carrier has inherently low-pattern jitter power. Furthermore, it features a very simple circuit configuration. The circuit configurations of an experimental modem and some important test results are deseribed in detail. It is shown that the modem has improved performance characteristics in such a high-speed region as 1.6 Gb/s while its circuit configuration is much simplified. 相似文献
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介绍了基于IS-95标准的CDMA系统PN偏置规划,推导出使用相同PN偏置的基站间再用距离,通过分析系统参数PILOT_INC,得出相邻偏置之间可用的最小距离,并阐述了实现PN偏置规划的步骤及方法。 相似文献
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A. P. Clark A. Aftelak M. Savjani C. Ang 《International Journal of Satellite Communications and Networking》1990,8(5):349-361
This paper describes a novel technique for the measurement and correction of the Doppler shift (frequency offset) in a received QPSK signal that has been transmitted over a satellite link. The satellite is here assumed to be in a non-geostationary orbit, and correction of the Doppler shift is required to be achieved as soon as the satellite rises above the horizon, when the Doppler shift may be very high and the signal/noise ratio very low. The receiver now has no prior knowledge of the transmitted data, so that a non-data-aided system must be used, capable of operating under seriously adverse conditions. The selected technique measures the DFTs of successive blocks of samples of the received and demodulated signal, and from the DFTs it derives a control signal for the VCO, which generates the in-phase and quadrature reference carriers for the coherent demodulator. The frequency of the latter is adjusted to reduce the residual Doppler shift in the demodulated signal to a sufficiently small value, so that correct phase synchronization of the VCO on to the received signal carrier can then be achieved by means of an appropriate conventional system (not considered here). The paper describes the new technique of Doppler shift correction, and presents the results of computer-simulation tests to measure the time taken to correct an initial Doppler shift of 5 kHz in the received QPSK signal, at very low signal/noise ratios. 相似文献
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按照低轨卫星数据传输的特点,设计一种格式的TDMA信号,并以此信号为例介绍TDMA信号侦收解调中的系列问题:信号检测、多普勒频移测量、载波恢复和定时恢复。其中多普勒频移的测量采用LP方法,频率测量误差小于100Hz;载波恢复采用判决反馈环路,能够很好地对残余频差和相差进行捕获和跟踪;定时恢复采用数据转换跟踪环。用接收到TDMA通信数据对算法进行了验证,能够达到很好的解调效果。 相似文献
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Code-division multiple-access (CDMA) with direct-sequence/spread-spectrum (DS/SS) modulated signals has emerged as a strong candidate for the air interface of the universal wireless personal communication network planned for the end of the century. In this paper, we take into consideration a low-complexity blind adaptive interference-mitigating detector (BAID) scheme that minimizes the detrimental effect of the multiple-access interference (MAI) on the bit-error-rate (BER) performance of a CDMA data demodulator. We describe a few modifications to the original algorithm that make it more suitable to a practical implementation with dual-binary phase-shift keying (D-BPSK)-modulated DS/SS signals. Specifically, we show how to make the BAID invariant to a possible carrier phase offset introduced in the front-end of the data demodulator, and we also suggest how to increase the robustness of such detector to asynchronous MAI. The uncoded BER performance of the resulting “extended” detector is then evaluated theoretically and by computer simulation in the case of coherent and differential signal detection 相似文献
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Describes a balanced pinFET receiver which employs two signal amplification paths for homodyne detection of multigigabit-per-second, pilot-carrier PSK optical signals. Using narrow-line 1.51 mu m semiconductor lasers, the authors have employed this receiver to phaselock a local oscillator to a 295 pW pilot carrier with 8 degrees RMS phase error.<> 相似文献
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