共查询到20条相似文献,搜索用时 31 毫秒
1.
Mihajlo C. Stefanovic Goran T. Djordjevic Ivan B. Djordjevic Nebojsa D. Stojanovic 《International Journal of Satellite Communications and Networking》1999,17(1):37-49
The purpose of this paper is to provide the theoretical approach for determining the bit error probability in detecting a coherent quaternary phase-shift-keyed signal transmitted over a soft-limited channel in the presence of the uplink and downlink noise, as well as the noisy carrier reference signal. The uplink noise is considered in the specific way through the envelope variations and the frequency offset of the signal remitted by the satellite station having influence on the variations of the phase-locked loop parameters in the receiving ground station, consequently on the probability density function of the phase error, i.e. the average bit error probability. The downlink noise is also taken into consideration. The determined results are based on the non-linear phase-locked loop model with primary emphasis on the degradations in the system performance produced by the imperfect carrier signal extraction. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
2.
3.
《Microwave Theory and Techniques》1984,32(12):1565-1572
The spectral distribution of the themal noise within a microwave cavity equipped with an extemal feedback loop has been calculated and measured. An equivalent electrical model is established from which the noise spectral density can be calculated at any post in the system, The effect of the gain and phase of the loop on the spectral distribution is measured with a spectrum analyzer through a heterodyne technique and comparison with theoretical calculations shows good agreement. Also, the modified cavity Q and resonant frequency is measured for various loop parameters. An experimental setup allowing precise measurement of frequency stability and FM noise close to carrier of microwave oscillators is presented and discussed. preliminary measurements of the short-term frequency stability of the system when operated as a microwave cavity-oscillator show a predominant flicker frequency noise. The measured FM noise close to carrier is related to time-domain measurements of frequency stabitity and to RF spectrum of the cavity-oscillator. 相似文献
4.
为了验证微波调制激光技术进行速度测量的可靠性,构建了一套通过微波调制激光技术测速的实验系统。利用激光作为载波,微波作为模拟调制信号对激光信号进行强度调制,光电探测器对信号光强度进行直接探测。利用射频电路,获得多普勒频移数据反演发射端和接收端相对运动速度。同时通过测量运动距离和时间计算平均运动速度,作为第三方数据,用于与微波调制激光技术测速的数据进行比较。理论分析了这套系统的原理并对其进行了实验验证。实验结果表明,利用微波调制激光技术测速的数据与第三方数据平均偏差小于2.0%,符合性好。 相似文献
5.
《Microwave Theory and Techniques》1979,27(12):969-974
A silicon bipolar transistor together with a barium titanate dielectric resonator were used to design a low noise microwave synthesizer. The oscillator was phase locked to a low-frequency (LF) reference with microwave frequency selection provided by a high-speed digital programmable divider within the phase-locked loop. The resulting FM noise Delta f/sub rms/ was 0.0003 Hz in a 1-Hz band greater than 1000 Hz from the 1-GHz carrier. 相似文献
6.
Consideration is presently being given to an optical-RF relay deep space communication link that transmits optical PPM data from spacecraft to orbital relay, then retransmits the data via microwave to ground. It is generally advantageous to use Reed-Solomon (RS) encoding over the PPM optical link for improved error correction. In this paper several demodulating schemes are considered for generating the RS symbols at the relay photodetector output, and the effect of each on overall RS decoding performance is computed. Both Poisson and Gaussian optical noise models are used in the evaluation. The effect on performance of bit errors in the relay downlink is also examined. 相似文献
7.
8.
The effects of impulsive noise on phase-locked loop (PLL) FM demodulators is investigated. The PLL FM demodulator used for the experiments is basically a second order loop employing an active filter. The impulsive noise used for this work is ignition noise. Impulse response of the receiver is investigated and the PLL FM demodulator is digitally simulated. The response of the receiver employing the PLL FM demodulator used in the ground terminal to an input signal consisting of unmodulated carrier and impulses is investigated experimentally. The system margin is fouind to be degraded by about 10 dB. 相似文献
9.
Heterodyne transmission experiments of multiple video channels using differentially encoded quadrature phase shift keying (QPSK) are described. Combining the QPSK microwave modulation format with the subcarrier multiplexing technique results in a total of 20 video channels at 50 Mb/s being transmitted on 10 microwave subcarriers. Using a differential encoding approach, this system provides good receiver sensitivity and bandwidth efficiency, while maintaining a simple receiver design. No carrier recovery circuit or phase-locked loop is required for demodulation, which greatly reduces the receiver complexity. It is demonstrated that only a standard delay and multiply demodulator are necessary. With optical heterodyne detection, a receiver sensitivity of -37.5 dBm is achieved for the 20 channel system. The extension of this technique to intensity modulated direct detection subcarrier systems along with migration scenarios for digital video and broadband services is discussed 相似文献
10.
11.
《Microwave Theory and Techniques》1964,12(3):316-322
This paper discusses some recent experimental results obtained using special gallium arsenide point-contact diodes for the generation of phase-locked carrier pulses in the microwave and millimeter-wave bands. Several methods of generating such pulses are described. 11.2-Gc microwave phase-locked carrier pulses of about 1.0-nanosecond base duration have been generated at a 160-megabit/second rate. These microwave pulses, which are generated directly from a baseband signal, normally have peak power levels in excess of 0.5 mw. Millimeter-wave phase-locked carrier pulses have also been generated at 56 Gc. These very high frequency pulses have a base duration as short as 0.25 nanosecond and occur at a 160-megabit/second rate. Furthermore, phase-locked carrier pulses have been generated at frequencies as high as 89.6 Gc. A simple method of generating nonphase-locked 0.3-nanosecond millimeter-wave carrier pulses directly from 1.92 gigabit/second rate baseband pulses has also been investigated. The experimental arrangement used to demonstrate the "turn on" and "turn off" principle of transient carrier pulse generation is described. 相似文献
12.
Using the nonlinear second-order phase-locked loop (PLL) model the performance of the heterodyne coherent optical phase shift keying (PSK) systems with Costas loop in multichannel environment is considered in this paper for the first time. The shot noise of the corresponding photodiodes and adjacent channel interferences are described through the signal-to-noise ratio (SNR) in the loop bandwidth, while the laser phase noise is described through the normalized frequency fluctuations instead of the phase ones. The theory and results presented in this paper can be applied when analyzing and optimizing the performance in the region where the linear PLL model is not enough good 相似文献
13.
14.
15.
Wei-Lung Mao 《Circuits, Systems, and Signal Processing》2007,26(1):91-113
Carrier phase measurement is essential for high-accuracy measurement in kinematic global positioning system (GPS) applications.
For GPS receiver design, a narrow noise bandwidth is desired to decrease phase jitter due to thermal noise. However, this
bandwidth will deteriorate the capability of the tracking loop and result in cycle slipping. Based on bandwidth adjustment
criteria, a novel intelligent GPS receiver is proposed for solving the carrier phase tracking problem in the presence of
high dynamic environments. A phase error estimator is developed in the carrier loop to conduct the phase error signals; i.e.,
frequency and frequency ramp errors. Two kinds of fuzzy inference (FI)-based approaches, fuzzy logic control and adaptive
neuro-fuzzy control methods, that are simple and have easy realization properties are designed to perform rapid and accurate
control of the digital frequency phase-locked loop (FPLL). A new design procedure for kinematic GPS receiver development
is also presented. The computer results show that the FI-based receivers achieve faster settling time and wider pull-in range
than the conventional tracking loops while also preventing the occurrence of cycle slips. 相似文献
16.
A low jitter,low spur multiphase phase-locked loop(PLL) for an impulse radio ultra-wideband(IR-UWB) receiver is presented.The PLL is based on a ring oscillator in order to simultaneously meet the jitter requirement, low power consumption and multiphase clock output.In this design,a noise and matching improved voltage-controlled oscillator(VCO) is devised to enhance the timing accuracy and phase noise performance of multiphase clocks.By good matching achieved in the charge pump and careful choice of the l... 相似文献
17.
脉冲多普勒雷达是一种新型体制雷达,其发展基础源于动目标显示雷达。过去,对脉冲多普勒雷达进行干扰的器件是行波管,在其螺线极与地之间加锯齿波信号实现载频移频,加噪声信号实现噪声调相,这种方法存在诸多弊端。随着数字技术的快速发展,数控移相器具备小体积、高速度、低输入、易控制等优点,而这些特点正是行波管所欠缺的。故采用数控移相... 相似文献
18.
卫星通信中多普勒频偏的预校正 总被引:1,自引:1,他引:0
在低轨道卫星通信中,由于多普勒效应,无线电信号会产生频率偏移现象,这为接收机设计带来了一定的困难。一种新方法可用于消除多普勒频偏的影响:根据卫星与地面接收站之间的相对位置和速度,可预先计算出信号的多普勒频偏。据此实时地修正接收机中数字频率合成器输出的本振频率,以达到消除多普勒频偏的目的。 相似文献
19.
Enric Vilar John Austin 《International Journal of Satellite Communications and Networking》1991,9(2):123-136
A theoretical and experimental study of Doppler correction strategies for elliptical orbit satellite communications is presented. Exact analytical expressions for Doppler shift and elevation angle as a function of perigee time of the ground-station are also presented. It is shown that for a 63° inclined Molnya orbit and a U.K. observer, the Doppler shift remains below about ± 10 ppm and the Doppler rate below about 6 × 10?4 ppm/s. Various strategies for continuous Doppler correction of the on-board oscillators are reviewed or proposed. These include a closed loop ground–satellite system and an on-board programmable correction approach. Two detailed theoretical and experimental studies of on-board encoded Doppler correction distribution systems are presented in the context of the UK CERS/TSAT mobile communications experiment. A frequency lock system which requires the distribution of only one signal and a phase-lock system requiring a master reference and the time-variant code word are described. Numerical values for a 1·5 GHz carrier are presented throughout but can be scaled to other frequencies. 相似文献
20.
The theoretical analysis of a digital satellite broadcasting system in the presence of phase noise is performed. An effective technique to design the carrier recovery circuit is also presented based on the analyzed loop parameters, such as degradation loss due to phase noise, average time to cycle slip, and carrier signal acquisition time. It is possible to design a system providing the optimal service and satisfying service requirements for a digital satellite broadcasting system. In this paper, the carrier recovery loop that provides optimal performance in the presence of phase noise exhibits the parameters of 0.707 for damping factor and 40 kHz for noise bandwidth. The designed phase-locked loop indicates a performance of 0.26 dB for impairment due to phase noise at 10-3 BER, 3.88×106 hours for average time to cycle slip, and 34 msec for carrier signal acquisition time. The carrier acquisition time of the designed carrier recovery circuit is in accordance with the analyzed result 相似文献