共查询到20条相似文献,搜索用时 28 毫秒
1.
基于小波变换的干涉信号包络提取方法研究 总被引:1,自引:0,他引:1
为了实现对宽谱光源自相干函数的测量,必须对宽谱光源干涉信号的包络进行提取.因此,宽谱光源干涉信号包络的提取就成为了测量光源自相干函数的关键因素.针对现有的包络解调方法的不足,建立了基于复Morlet小波的干涉信号包络提取方法.该方法采用复Morlet小波作为母小波,通过选择适合尺度参数和位置参数,可以有效地提取干涉信号的包络并具有良好的抗噪能力;利用计算机Matlab仿真证明了该方法的有效性;最后利用该方法对韩国Fiber Pro公司的白光干涉仪干涉输出信号进行包络提取,动态范围达到-60 dB. 相似文献
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The codeword error rate (WER) performance of noncoherent frequency-shift keying with soft decision decoding of block codes using Chase's second algorithm (1972) is investigated in a Rayleigh fading channel. The received signal envelope is sampled and used as channel measurement information. The theoretical upper and lower bounds of the WER are derived, assuming independent Rayleigh envelope samples in a received block. When the Golay (23, 12, 7) code is used, soft decision decoding with 6-bit error correction capability (3-bit error and 3-bit erasure) requires an average signal-to-noise power ratio about 5 dB lower than that for minimum distance decoding with 3-bit error correction to obtain a WER=10-3. The effects of bit interleaving on the WER performance when fading envelope variation is slow compared to the bit rate are investigated through computer simulations 相似文献
3.
An Interferometric Method for High Extinction Ratio Measurements With 60-dB Dynamic Range 总被引:1,自引:0,他引:1
《Photonics Technology Letters, IEEE》2008,20(24):2075-2077
4.
Low profile diversity antenna for MIMO applications 总被引:1,自引:0,他引:1
A low profile diversity antenna for MIMO application is introduced. The design is based on a double folded dipole antenna filled with a slab of ceramic of /spl epsiv//sub r/=6. Two diversity antennas operating at 5.2 GHz are designed and implemented on a handset for IEEE.11a wireless systems. The isolation is found to be better than 20 dB in both measurement and simulation and measured bandwidth is about 250 MHz at -10 dB. Simulated and measured radiation patterns are close to each other. The envelope cross-correlation is calculated to be much less than 0.1 and the ratio of the mean effective gain between the antennas is close to unity. 相似文献
5.
《Solid-State Circuits, IEEE Journal of》1985,20(3):697-702
This paper presents a monolithically integrated IF amplifier and envelope detector for an AM upconversion car-radio receiver. This receiver is intended for the reception of the long-wave and medium-wave frequency bands and uses an intermediate frequency of 10.7 MHz. Specific requirements resulting from the upconversion concept will be illustrated and the basic considerations for maximization of the signal-to-noise ratio as a function of the input signal level will be given. Furthermore, a new method will be presented for fixing the signal levels and the AGC speed in the amplifier. The amplifier uses two emitter-driven variable-gain pairs alternated by negative-feedback current amplifiers. It has an AGC range of 90 dB and a gain of 66 dB. The audio output level is constant within 0.2 dB over the full controll range. A cross-quad compensated envelope detector is driven at a level as low as 30 mV and shows less than 3-percent distortion at a modulation depth of 80 percent. 相似文献
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We discuss a possible method for interference control in radio systems whose desired signal is analog FM. The method utilizes the fact that the desired signal has a nearly constant envelope; with interference present, the composite envelope becomes noisy. A controlling processor measures this additional envelope noise, and iteratively adjusts the complex combining gain of an auxiliary signal to minimize the interference. The expected residual interference remaining after minimization is proportional to the reciprocal of the square of the rms envelope fluctuation of the desired signal. This result was confirmed in a laboratory simulation of an intersecting radio route case using both large and small index FM. Beginning with signal-to-interference ratios of 30 to 40 dB, the controller increased these numbers to about 60 dB, the expected theoretical limit for a signal with 0.1 percent rms envelope fluctuation. 相似文献
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Kimball D.F. Jeong J. Hsia C. Draxler P. Lanfranco S. Nagy W. Linthicum K. Larson L.E. Asbeck P.M. 《Microwave Theory and Techniques》2006,54(11):3848-3856
A high-efficiency wideband code-division multiple-access (W-CDMA) base-station amplifier is presented using high-performance GaN heterostructure field-effect transistors to achieve high gain and efficiency with good linearity. For high efficiency, class J/E operation was employed, which can attain up to 80% efficiency over a wide range of input powers and power supply voltages. For nonconstant envelope input, the average efficiency is further increased by employing the envelope-tracking architecture using a wide-bandwidth high-efficiency envelope amplifier. The linearity of overall system is enhanced by digital pre-distortion. The measured average power-added efficiency of the amplifier is as high as 50.7% for a W-CDMA modulated signal with peak-to-average power ratio of 7.67 dB at an average output power of 37.2 W and gain of 10.0 dB. We believe that this corresponds to the best efficiency performance among reported base-station power amplifiers for W-CDMA. The measured error vector magnitude is as low as 1.74% with adjacent channel leakage ratio of -51.0 dBc at an offset frequency of 5 MHz 相似文献
9.
为了提高功率放大器的回退效率以更好地适应第五代移动通信系统的高峰均比信号的需求,文中提出
了一种基于包络跟踪的J 类功率放大器的设计方法,通过对电源调制器的设计来动态调制J 类功率放大器的供电电
压,以降低漏极直流功耗,实现提高功率放大器效率的目标。最终的测试结果表明在3.4~3.6 GHz 频率范围内,当采
用带宽20 MHz、峰均比为8.6 dB 的正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)调制信号时,测得
恒压供电时的功率放大器的回退效率为25.3%~29%;然后采用带宽20 MHz、峰均比为6.4 dB 的64 正交调幅(Quadrature
Amplitude Modulation, QAM)调制信号时,测得恒压供电时的功率放大器的回退效率为33.1%~34.1%。而采用包
络跟踪动态供电时所测得的回退效率分别为30.2%~35.1%和37.1%~41.3%,回退效率提升5%~7%。经过数字预失
真处理之后,该功率放大器的邻近信道功率泄露比低于-46dBc,具有良好的线性度。 相似文献
10.
《Vehicular Technology, IEEE Transactions on》1974,23(3):72-83
Measurements of the amplitude probability distribution (APD) of the envelope and measurements of other parameters of automobile ignition noise were made at frequencies between 24 and 30 MHz. The measurements were conducted at a quiet site where several single stationary vehicles were operated at engine speeds corresponding to idle and cruise. Measurements were also made at two distances near a freeway, for light traffic (approximately 20 vehicles per min) and for heavy traffic (approximately 45 vehicles per min). The principal instrumentation consisted of several phase-stable receivers with coherent quadrature detectors whose outputs were digitized at a rate of 200 samples per quadrature component per second and recorded on magnetic tape for computer processing. About 10 min of data (about 120 000 samples) were obtained during each measurement. The computer plotted the APD on a Rayleigh scale in dB relative to thermal noise and calculated the mean noise power available at the antenna terminals (related by a constant to the noise factor Fa ) and Vd --the ratio in dB of rms to average voltage. The average power of the ignition noise increases with engine r/min and Vd usually decreases. Near a freeway, most of the noise is contributed by a small number of very noisy vehicles. The APD's for various situations are strikingly similar; all show that most of the noise envelope samples in a measurement are Rayleigh distributed. A small percentage of the noise samples do not follow the Rayleigh distribution, but are of higher amplitude. This percentage is higher for an engine at cruise speed than at idle speed, and higher for heavy traffic than for light traffic. 相似文献
11.
Single-sideband (SSB) and AM signals are analyzed using a waveform that can be varied in shape from a spike through a sine wave to a square wave by varying a parameter. The average sideband powers and the peak envelope powers are then calculated and compared. It is shown that the ratio of average sideband power to peak envelope power for AM is more favorable than that for SSB for `squarish' modulating signals. However, the ratio for SSB is about 9 dB higher than it is for AM for modulating signals ranging in shape from a sine wave to a spike 相似文献
12.
The effects of certain atmospheric conditions upon pulse-code modulation (PCM) data transmission at a carrier frequency of 15.3 GHz are discussed in this paper. Using an amplitude-shift keying (ASK) modulation to transmit 1300000 bit/s across a 9.5 mi line-of-sight path, the performance characteristics of the system, relating to conditions in the channel, were measured and are presented in this study. Theoretical curves of probability of error versus predetection signal-to-noise ratio (SNR), are compared to measured error probabilities; these are obtained at different received signal levels, and under various clear weather conditions ranging from humid to dry. Above 15 dB predetection SNR, the system operates more efficiently than theoretically predicted for ASK modulation over a Rayleigh fading channel. The detected envelope probability distributions are computed for different values of SNR. Results show that drier weather, which causes amplitude fluctuations of a shallow nature, results in greater error probabilities than those for more humid conditions; the term shallow fading is used to describe short term (5-10 min) received signal envelope variations of less than 1 dB. For example, error probabilities for a predetection SNR of 14 dB, ranged from 0.005 to 0.078, from humid to dry conditions respectively. These values fall between the theoretical values of 0.0005 for the nonfading case, and 0.0740 for Rayleigh fading. 相似文献
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This letter presents a new linearization method for mixers employing predistortion and envelope signal injection. In this technique the third order intermodulation distortion (IM3), at the output of a mixer in IF band, was cancelled by using a diode predistortor and injecting the envelope of the RF input signal to both the predistortor and the mixer. By properly adjusting the amplitude and polarity of the injected envelope signal, up to 26 dB improvement of the IM3 is obtained in a two tone test with 100 kHz separation at 1.9 GHz. This method operates very well over a wide range of output power up to the 1 dB compression point of the mixer. 相似文献
16.
提出了一种基于槽天线的小型化、高隔离度的超宽带(Ultra Wideband, UWB)多入多出(Multiple-Input Multiple-Output, MIMO)天线.该MIMO天线由两个槽天线单元构成, 为了增加天线阻抗带宽, 每个槽天线单元由末端带有圆形贴片的微带线和末端为圆形的槽线两部分耦合馈电.采用在地板上开槽和方向图分集方法, 减少地板表面波和空中电磁波影响, 达到提高天线隔离度的目的.数值仿真和实验结果表明:该天线在3.1~11 GHz频段内满足端口反射系数|S11| < -10 dB, 隔离度|S12|在7~11 GHz频段内小于-25 dB, 在3.1~7 GHz频段内小于-16 dB, 并根据仿真和测试S参数计算了包络相关系数. 相似文献
17.
为了消除采样过程中的噪声干扰,进一步提高重构图像质量,针对数字微镜阵列(DMD)与桶探测器在测量过程中点对点采样产生的起伏噪声导致图像信噪比降低的问题,提出基于哈达玛矩阵编码测量的压缩采样成像方法。首先采用DMD分区控制方法,利用哈达玛编码测量,计算获得低分辨率的粗糙图像,接着在预测的重要小波系数所在区域,对同一尺度上的重要区域利用哈达玛矩阵进行投影,同时计算出这些区域的小波系数,最后通过小波逆变换获得重构图像。实验表明,在测量噪声为0.2倍的热噪声下,只需要10%的采样率,通过哈达玛编码测量,图像峰值信噪比从13.98dB最高提高到34.56dB,提高了20.58dB,成像质量明显改善,清晰度高。当存在较大的测量噪声时,该方法可以大幅提高图像的信噪比,尤其适用于微弱光信号条件下的高灵敏压缩采样成像。 相似文献
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We have implemented an automated, nonmechanical approach to the measurement of polarization dependent loss (and, equivalently, gain). We use a deterministic fixed-states method to derive Mueller matrix elements from intensity measurements at specific polarization states. Voltage-modulated liquid-crystal variable retarders set the polarization states. Synchronous detection is employed to increase the signal-to-noise ratio (SNR) of the system and thereby allow measurement resolution to better than 0.001 dB. We present polarization-dependent loss measurements from 0.0016 to 0.56 dB at 1550 nm to verify performance 相似文献
20.
《Vehicular Technology, IEEE Transactions on》2009,58(5):2288-2298