共查询到20条相似文献,搜索用时 296 毫秒
1.
2.
简述了超外差式频谱分析仪的组成及其工作原理,论述了微波频谱分析仪灵敏度的基本概念,给出了频谱分析仪灵敏度的计算公式,讨论了频谱分析仪灵敏度与噪声系数、分辨带宽和射频衰减的关系。研究了改善微波频谱分析仪灵敏度的方法:降低噪声系数法、压窄分辨带宽法和减小射频衰减法。讨论了频谱分析仪本底噪声对小信号测量影响的修正方法。 相似文献
3.
4.
《Microwave Theory and Techniques》1977,25(4):294-318
A tutorial review of the basis for transmitter noise measurements shows that noise is best described and measured as AM and FM noise. The determination of RF spectrum is done by calculation after the AM and FM noise are known. The contribution of AM noise to RF spectrum shape is determined by the power spectral density shape of the AM noise. The contribution of FM noise to RF spectrum is to make the shape that of an RLC circuit resonant response rather than a delta function with a sideband structure. The measurement of AM noise is done with a direct detector diode. The measurement of FM noise for frequencies above 5 GHz is done with a discriminator based on a one-port cavity resonator. The measurement of FM noise below 5 GHz is done with an improved transmission line discriminator which is described in detail. Measurement of low-power low-noise signal sources is made posbible with an injection-locked oscillator for a preamplifier to the discriminator. The most widely used baseband analyzer is the constant bandwidth superhetdrodyne wave or spectrum analyzer. Most differences in measurement results are resolved by understanding the baseband analyzers. At least the baseband spectrum analysis of transmitter noise measurements can be automated with worthwhile savings in time and improvement of documentation. 相似文献
5.
由于功率计只能测试功率较大的微波信号,频谱仪测试脉冲信号存在失真现象,因此低功率超宽带线性调频脉冲信号功率测试在实际工程中是一个待解决的问题。在分析频谱仪功率测试原理的基础上,通过对信号频谱及频谱仪测试机理的理论分析,提出了采用频谱仪对线性调频脉冲信号功率测试的修正方法,并进行了详细分析研究,实测数据检验了该方法的有效性,解决了宽带低功率线性调频脉冲信号测试的难题。 相似文献
6.
This paper describes the theory and procedures necessary to understand and measure the emissions of an 8-VSB DTV transmitter. It starts with the FCC's requirements, then moves to the nature of the 8-VSB signal. The noise bandwidth of the signal is calculated and it is demonstrated how to relate this bandwidth to the FCC's requirement that the out of channel emissions be measured in a 500 kHz bandwidth. This discussion justifies the measurement procedure provided, showing how a spectrum analyzer or other specialty 8-VSB measurement equipment may be used to determine compliance with the FCCs out of channel emissions requirements. Methods of achieving measurements to the FCCs -110 dB specification are discussed. Effects of several factors that may affect measurement accuracy including measurement bandwidth, intermodulation, noise floor, logarithmic amplifier error, detector error and mismatch errors are discussed. An appendix gives an easy method for approximating the power of the 8-VSB signal by adding 12 dB to the pilot signal amplitude. The appendix also derives the relationship between the amplitude of the pilot signal and the bandwidth-dependent amplitude of the head of the 8-VSB signal 相似文献
7.
介绍了一种自主研制的新型电荷灵敏型三级放大器,其电路设计主要采用ADA4817高速低噪声集成运算放大芯片,该三级放大器噪声低、稳定性好、电路结构简单、性价比高、检修更换方便,可以不失真地放大上升时间在ns级的信号,放大器输出信号质量优异,可配合后续的多道分析器MCA8000D读取微通道板(microchannel plate,MCP)组件或单通道电子倍增器(single-channel electron multiplier,CEM)的单光电子谱,测试结果表明:自主设计的ADA4817型放大器在一定的方波标定脉冲信号下,其基线的宽度小于2 mV,上升沿时间约为800 ns,幅值约为40 mV,性能接近或略优于A250型放大器,可以更好地配合后续的多道分析器MCA8000D进行输出波形的分析和处理,完全满足MCP或CEM探测器的脉冲性能测试需求。 相似文献
8.
9.
We report the first definitive PM and AM noise measurements at 100 GHz of indium phosphide (InP) amplifiers operating at 5 K, 77 K, and room temperature. Amplifier gain ranged from +7 to +30 dB, depending on input RF power levels and operating bias current and gate voltages. The measurement system, calibration procedure, and amplifier configuration are described along with strategies for reducing the measurement system noise floor in order to accurately make these measurements. We compute amplifier noise figure with an ideal oscillator signal applied and, based on the PM noise measurements, obtain NF=0.8 dB, or a noise temperature of 59 K. Measurement uncertainty is estimated at /spl plusmn/0.3 dB. Results show that the use of the amplifier with an ideal 100-GHz reference oscillator would set a lower limit on rms clock jitter of 44.2 fs in a 20-ps sampling interval if the power into the amplifier were -31.6 dBm. For comparison, clock jitter is 16 fs with a commercial room-temperature amplifier operating in saturation with an input power of -6.4 dBm. 相似文献
10.
Hansen P.B. Eisenstein G. Wiesenfeld J.M. Tucker R.S. Raybon G. 《Electronics letters》1989,25(9):563-565
The authors report time-resolved gain and noise spectra measurements in an electrically pulsed travelling-wave optical amplifier. They demonstrate a modest (60 AA) blue shift in the gain spectrum and high (25 dB) gain in a 250 mu m-long amplifier driven by a 1 GHz, 60 ps pulse train.<> 相似文献
11.
F. Labaar 《Journal of Infrared, Millimeter and Terahertz Waves》1984,5(2):123-133
A test method is described that uses the Delay Line Bridge (DLB) discriminator as a phase modulation (PM)- or amplitude modulation (AM) detector. A brief discussion is given to explain the different measurement requirements for pulsed sources used in Doppler RADAR with stationary or slow moving transmitter platforms, and fast moving transmitter platforms. A practical solution is offered to the problem of inadequate isolation in present day W-band PIN switches. This measurement set-up, provides a direct measure of the level of spurious oscillations of the IMPATT source, the relative noise content in the turn-on and turn-off region of the RF pulse, and the phase ripple. It also illustrates the influence of reference source injection locking level on the measured characteristics. 相似文献
12.
13.
14.
A new discrete‐amplitude pulse width modulation (DAPWM) scheme for a high‐efficiency linear power amplifier is proposed. A radio frequency (RF) input signal is divided into an envelope and a phase modulated carrier. The low‐frequency envelope is modulated so that it can be represented by a pulse whose area is proportional to its amplitude. The modulated pulse has at least two different pulse amplitude levels in order that the duty ratios of the pulse are kept large for small input. Then, an RF pulse train is generated by mixing the modulated envelope with the phase modulated carrier. The RF pulse train is amplified by a switching‐mode power amplifier, and the original RF input signal is restored by a band pass filter. Because duty ratios of the RF pulse train are kept large in spite of a small input envelope, the DAPWM technique can reduce loss from harmonic components. Furthermore, it reduces filtering efforts required to suppress harmonic components. Simulations show that the overall efficiency of the pulsed power amplifier with DAPWM is about 60.3% for a mobile WiMax signal. This is approximately a 73% increase compared to a pulsed power amplifier with PWM. 相似文献
15.
为了提高半导体光放大器(SOA)增益系数谱测量的准确性,减少光谱仪分辨率和系统噪声对测量结果的影响,提出了由传统的Hakki-Paoli(HP)方法改进得到的基于小波去噪和去卷积过程的Hakki-Paoli(HP-DD)方法,分析了其原理,并给出去卷积的算法和小波去噪的原理。在数值模拟中,对模拟的放大自发辐射(ASE)谱进行处理,表明HP-DD方法能较大程度地改善增益系数谱的测量准确度。在实验中,通过对半导体光放大器的放大自发辐射谱进行实际测量,分别用HP-DD方法和HP方法求得增益系数谱,验证了HP-DD方法的测量结果的精确度有很大程度的改善。 相似文献
16.
Noise measurements were made on an InGaAsP semiconductor diode laser by monitoring and analyzing the mode-locked pulse train power spectrum. The noise content of the mode-locking RF source was observed to be transferred directly to the laser pulse train and, thus, careful selection of the drive oscillator is essential. Amplification of the laser pulses by an erbium-fiber amplifier did not lead to any increase in timing jitter and the additional amplitude noise present could be removed by using a more compatible pump source such as a diode laser operating at either 980 or 1490 nm 相似文献
17.
This paper presents a low-cost test technique using a new RF Built-In Self-Test (BIST) circuit for 4.5-5.5 GHz low noise amplifiers (LNAs). The test technique measures input impedance, voltage gain, noise figure, input return loss and output signal-to-noise ratio of the LNA. The BIST circuit is designed using 0.18 μm SiGe technology. The BIST circuit contains test amplifier and RF peak detectors. The complete measurement set-up contains LNA with BIST circuit, external RF source, RF relays, 50 Ω load impedance, and a DC voltmeter. The test technique utilizes output DC voltage measurements and these measured values are translated to the LNA specifications such as input impedance and gain through the developed equations. The technique is simple and inexpensive. 相似文献
18.
19.
随着通信和雷达的发展,脉冲信号的相位噪声成了影响整个系统性能的重要因素之一,采用传统模拟相位检波法测量脉冲信号相位噪声是一个非常大的挑战,因为这样的测试系统非常复杂,并且在测量相位噪声之前需要非常繁琐的校准程序,先进的正交数字相位解调和幅度解调技术能很好地解决这个问题。采用正交数字相位解调和幅度解调技术的系统不需要相位检波器和复杂的校准程序,利用极低噪声的参考源和互相关技术,提高了系统动态范围和测量灵敏度,实现了一键式精密测量脉冲相位噪声和调幅噪声。 相似文献
20.
This paper studies the coherence of the radio-frequency (RF) beat note between the two frequencies emitted by a two-eigenstate solid-state laser operating in pulsed regime. Depending on how the pulsed operation regime is obtained-passive Q switching using a saturable absorber or resonant amplitude modulation using pump-power modulation-we show theoretically and experimentally that the RF beat note loses or maintains its coherence from pulse to pulse. Namely, RF coherence is shown to be lost when the laser intensity vanishes between pulses, while it can be maintained if a slight amount of intensity remains inside the cavity between pulses. We give experimental demonstrations of these results for both Nd:YAG and Er-Yb:glass two-frequency pulsed lasers, in connection with applications to lidar-radar systems. 相似文献