Phase Noise Measurement System Research Articles

Research on the Linear Demodulation Range and Background Noise of Fiber-Optic Interferometer System

The linear demodulation range and background noise of the Michelson interferometer system are investigated with a laser phase noise measurement system. We have theoretically and experimentally analyzed the performance of the interferometer system by changing the frequency modulation amplitude of the laser and the optical path difference (OPD) of the interferometer, respectively. It is shown that the linear demodulation range of the Michelson interferometer system is finite, which depends on the parameters of the system, such as the sample frequency, the delay time between two interferometer arms, and the system bandwidth. Furthermore, the experimental results indicate that the background noise of the interferometer system can be reduced by using a sufficiently long OPD so that the smaller true phase information can be detected with the demodulation system. The parameters of the measurement system could be optimized to satisfy the demand of the phase demodulation with different levels, which is of great significance for the phase monitoring interrogator, such as fiber-optical interferometer sensors and distributed acoustic sensors.

1/f Additive Phase Noise Analysis for One-Port Injection-Locked Oscillators

The 1/f additive phase noise of one-port injection-locked oscillators is experimentally characterized and analyzed using a simple analytic model based on the generalized 1/f Kurokawa theory. To experimentally verify the prediction of the simple analytic model proposed, two negative-conductance transmission line pHEMT oscillators operating at 2.4828 GHz and 2.485 GHz were designed and fabricated. A new configuration for integrating an additive phase noise measurement system with a large signal network analyzer (LSNA) is introduced to jointly acquire both the noise and RF waveforms of the one-port injection-locked oscillator. The Kurokawa derivatives needed for the analytic expression were experimentally obtained using the LSNA measurements and optimized to accurately model the corner frequency. A good agreement between the predicted and experimental results was obtained for both the injection-locked and free-running oscillators. In contrast to phase noise measurements of the free-running oscillator, which can only characterize the oscillator-upconverted 1/f3 noise, the additive phase noise characterization of the injection-locked oscillator is shown to provide the means to directly observe and characterize the input-referred intrinsic 1/f noise source of the oscillator negative resistance.

An Efficient Cross-Correlation Method for a Digital Phase Noise Measurement System

In this paper, we propose a digital phase noise measurement using a 10-bit digital oscilloscope MXR608A from Keysight Technologies. The digital oscilloscope’s four channel data are used for digital phase noise measurement: two channels are assigned for the equally divided SUT (source under test), while the other two are assigned for the equally divided reference signals. First, we propose a cross correlation method to identify the phase noises added by the ADCs in the digital oscilloscope from the measured phase noises. Then, we propose a novel cross correlation method to extract the SUT phase noise. The cross-correlation output of the proposed method yields only the SUT phase noise and does not contain the reference signal phase noise unlike the traditional method. The proposed method was applied to measure the phase noises of the two SUTs, Keysight’s synthesized signal generator E8257D and function generator 33600A. The measured phase noises of the two SUTs were compared and found to show remarkable agreements with those measured using Keysight’s signal source analyzer E5052B. The phase noise floor of our digital phase noise measurement system is about -160 dBc/Hz.

Wideband Microwave Phase Noise Analyzer Based on All-Optical Microwave Signal Processing

An approach for wideband phase noise measurement of microwave signal sources is proposed based on all-optical microwave signal processing. In the proposed scheme, an optical carrier is sequentially modulated by the signal under test (SUT) in a phase modulator and a dual-polarization modulator to generate two +1st-order sidebands with orthogonal polarizations. A time delay is introduced between two sidebands by a span of low-loss optical fiber. Combined with a polarization controller and a polarizer, photonic microwave downconversion with a desired phase shift and time delay can be realized after photodetection, and the phase noise of the SUT can be calculated thereafter. Since all the microwave signal processing functions in the conventional photonic-delay-line-based phase noise measurement system are implemented in the optical domain, the proposed scheme has a large operational bandwidth and a high measurement sensitivity. In the experimental demonstration, accurate phase noise measurement of SUTs is achieved in a frequency range of 10-35 GHz, and a phase noise floor as low as −132.16 dBc/Hz at 10 kHz is obtained.

Ultra-Low Phase Noise Measurement of Microwave Sources Using Carrier Suppression Enabled by a Photonic Delay Line

We propose and demonstrate a photonic delay line based carrier suppression interferometer system for measuring the phase noise of microwave sources. We show both theoretically and experimentally for the first time that carrier suppression is capable of suppressing the effects of the residual phase noise of the microwave amplifiers and the relative intensity noise of light in the system by up to 70 dB, and therefore effectively eliminates the contributions of these noise sources to the noise floor of the phase noise measurement system. Using a 2-km photonic delay line, we achieved phase noise measurement floors of −126 dBc/Hz at 1 kHz and −152 dBc/Hz at 10 kHz around a 10 GHz carrier, respectively, which are 15 and 20 dB lower than those of a frequency discriminator based phase noise measurement system using the same length of fiber delay and the same optical and microwave components. The noise floor of −152 dBc/Hz at 10 kHz is also 8 dB and 17 dB lower than those of a Keysight E5052B phase noise measurement system with 100-times cross-correlation and without cross-correlation, respectively. Even lower phase noise floors are expected for such a carrier suppression system if microwave phase shifters with lower residual phase noise or a longer photonics delay line are used.

A Phase Noise Measurement System with Frequency Drift Compensation

Commercial equipment provides phase noise measurement solution for voltage-controlled oscillator (VCO), but it also needs to connect additional tuning voltage for VCO frequency stabilization. If the frequency-drifting VCO cannot be tuned directly, the measurement would be difficult. In this article, we present a prototype of a phase noise measurement system, without any connection for frequency stabilization. The innovation of this work is to compensate the frequency drift by introducing a delayed path. The frequency drift of the signal under test is calculated in advance, and then accurately compensates the delayed signal. The results are compared with commercial equipment, and it shows better performance when measuring frequency-drifting signal directly.

Phase noise measurement of an optoelectronic oscillator based on the photonic-delay line cross-correlation method.

Phase noise measurement of a dual-loop optoelectronic oscillator (OEO) based on a dual- photonic-delay line cross-correlation method is proposed and experimentally demonstrated. The dual-loop OEO and the phase noise measurement system are combined by sharing the transmitter of the optical link, which makes the structure of the system simpler. In part of the dual-loop OEO, the 10km long fiber is shared by the two loops of the OEO utilizing a wavelength division multiplexing technique. Higher quality factors are obtained simultaneously by the two loops. In part of the phase noise measurement system, a lower phase noise floor is realized through a cross-correlation method. In the experiments, a signal with oscillation frequency of 10.664GHz and a side-mode suppression ratio of 82.4dB is generated. Its phase noise is evaluated by the proposed system and PN9000C. The measured results of the two systems are in perfect agreement. The phase noise of the signal is measured as -122 dBc/Hz at a 10kHz frequency offset, and the phase noise floor of the 10μs delay phase noise measurement system is -148 dBc/Hz at a 10kHz offset at 10.6GHz, when the number of averaged results is 100.

Phase Noise Measurement of RF Signals by Photonic Time Delay and Digital Phase Demodulation

A simple and high-sensitivity frequency–discriminator-based phase noise measurement system using photonic time delay and digital phase demodulation is comprehensively investigated and experimentally demonstrated. By applying a low-loss optical fiber to provide a large amount of time delay, high phase noise measurement sensitivity and large operation bandwidth are guaranteed. Meanwhile, digital phase demodulation is employed to avoid sophisticated feedback control and complex calibration required in conventional frequency-discriminator-based phase noise measurement scheme, which not only eliminates the phase noise measurement error introduced by the feedback loop but also suppresses the influence of the amplitude noise in the signal under test. In addition, a solution for the in-phase and quadrature mismatch problem in the digital phase demodulation is proposed. An experiment is performed. Accurate phase noise measurement is achieved in a large bandwidth from 2 to 35 GHz. With a 2-km single-mode fiber serving as the delay line, phase noise measurement sensitivity as low as −134 dBc/Hz at 10 kHz is achieved at a RF frequency of 10 GHz. The phase noise sensitivity can be further improved by applying a longer fiber. The proposed system is simple, accurate, and stable, and can be applied for analysis of high-frequency and ultralow phase noise microwave signal sources.

Wideband microwave phase noise measurement based on photonic-assisted I/Q mixing and digital phase demodulation.

A wideband microwave phase noise measurement system is proposed based on quadrature phase demodulation of the mixing components of a signal under test (SUT) and its delayed replica. The time delay is introduced by a low-loss optical fiber, which can be sufficiently large to achieve a high phase noise measurement sensitivity, and the quadrature phase demodulation is achieved by photonic-assisted in-phase and quadrate (I/Q) mixing together with digital signal processing. Thanks to the optoelectronic hybrid quadrature phase demodulation, the use of feedback loops, which are usually required in conventional photonic-delay-line-based phase noise measurement systems, is avoided, and the measurable frequency range is expanded. An experiment is implemented. Accurate phase noise measurement of SUTs in a frequency range of 5-35 GHz is demonstrated. With a 2-km single-mode fiber serving as the photonic delay line, the phase noise floor is as low as -131 dBc/Hz at the offset frequency of 10 kHz. The proposed scheme can be applied for evaluating the performance of microwave systems using low-phase-noise and wideband tunable microwave sources.

Electro-optic comb based real time ultra-high sensitivity phase noise measurement system for high frequency microwaves

Recent progress in ultra low phase noise microwave generation indispensably depends on ultra low phase noise characterization systems. However, achieving high sensitivity currently relies on time consuming averaging via cross correlation, which sometimes even underestimates phase noise because of residual correlations. Moreover, extending high sensitivity phase noise measurements to microwaves beyond 10 GHz is very difficult because of the lack of suitable high frequency microwave components. In this work, we introduce a delayed self-heterodyne method in conjunction with sensitivity enhancement via the use of higher order comb modes from an electro-optic comb for ultra-high sensitivity phase noise measurements. The method obviates the need for any high frequency RF components and has a frequency measurement range limited only by the bandwidth (100 GHz) of current electro-optic modulators. The estimated noise floor is as low as −133 dBc/Hz, −155 dBc/Hz, −170 dBc/Hz and −171 dBc/Hz without cross correlation at 1 kHz, 10 kHz, 100 kHz and 1 MHz Fourier offset frequency for a 10 GHz carrier, respectively. Moreover, since no cross correlation is necessary, RF oscillator phase noise can be directly suppressed via feedback up to 100 kHz frequency offset.

Uncertainty analysis for a phase-detector based phase noise measurement system

Phase noise is an important parameter to characterise the frequency stability of oscillators and synthesised signal generators. Accurate measurement of phase noise is required for various applications in radar, communication and navigation systems. A single-channel phase-detector based phase noise measurement system is described. The system’s measurement errors and uncertainties have been analysed in details. The expanded uncertainty is about 2.7dB for calibrating phase noise of a signal generator at 0.001–1.6GHz for frequency offsets from 1Hz to 100kHz. The uncertainty budget for measuring a signal generator’s phase noise at 640MHz is also presented.

Photonic‐assisted wideband phase noise measurement of microwave signal sources

A photonic-assisted scheme for the phase noise measurement of microwave signal sources is proposed based on the optical delay-line method. In the proposed scheme, all the microwave signal processing is implemented in the optical domain, and the electrical devices that would limit the operation bandwidth and measurement sensitivity are avoided, leading to a large operation bandwidth and a high sensitivity. The feasibility of the proved phase noise measurement system is experimentally verified. A large operation bandwidth of 5–40 GHz is achieved, and a phase noise floor as low as −140 dBc/Hz at 10 kHz offset is obtained.

Flicker Noise in Opto-Electronic Oscillator and Photonic-Delay Homodyne Phase Noise Measurement System

In this paper, the effect of device flicker noise on the characteristics of both opto-electronic oscillator and Photonic-delay homodyne phase noise measurement system is analyzed. An analytic theory model of opto-electronic oscillator (OEO) is derived and verified by experiments in this paper, where the flicker and white noise are both considered. The sensitivity of Photonic-delay homodyne phase noise measurement system is improved by using high-linear photodetector and low-phase noise amplifier resulting from decreasing systematic phase noise.

Wideband Phase Noise Measurement Using a Multifunctional Microwave Photonic Processor

A novel scheme for measuring the phase noise of microwave signal sources is proposed based on the delay-line method using a multifunctional microwave photonic processor, which can simultaneously implement the electrical-to-optical conversion, provide a time delay, and control the phase of the output microwave signal. Thanks to the microwave photonic processor, the requirement for accurate phase control is relaxed and a large operation bandwidth of the phase noise measurement system can be achieved. An experiment is performed. The phase noise measured by the proposed system agrees well with the result measured by a commercial spectrum analyzer, and the noise floor of the measuring system is lower than −130 dBc/Hz at 10 kHz frequency offset. The large operation bandwidth is also verified by measuring the phase noise of a wideband signal source in a frequency range from 5 to 40 GHz without rebuilding the system.

基于光纤延时线的低相噪光电振荡器与高灵敏度相噪测量系统的研制

Injection-locking method is applied to X band low-phase noise and small-spur opto-electronic oscillator (OEO) in this paper. Based on the quasi-linear theory, a new analytical model is built, and the effect of injection power on the single side band (SSB) phase noise and spurs of OEO is also analyzed. Results suggest that only moderate injection power can make sure both of the low phase noise and small spurs. In order to measure super-low phase noise of oscillators, the cross-correlation measurement system based on the fiber delay line is built, where high linear photodetector and low-phase noise amplifier are used to improve systematic sensitivity. low-phase noise OEO (-125 dBc/Hz@1 kHz、-145 dBc/Hz@10 kHz) and high-sensitivity phase noise measurement system (-130 dBc/Hz@1 kHz、-168 dBc/Hz@10 kHz) in X-band is finished. Those high-level index has not been reported in China and is on the level with the best index reported in foreign literature.

Photonic-delay homodyne technology for low-phase noise measurement

The sensitivity of photonic-delay homodyne phase noise measurement system is improved by using high-linear photodetector and low-phase noise amplifier in this paper. The phase noise model for microwave link is proposed and the sensitivity of photonic-delay based measurement system is analyzed with this theory model. Results show that phase noise sensitivity in this measurement system is −130dBc/Hz at 1kHz and −145dBc/Hz at 10kHz, and in my knowledge it is the highest sensitivity for photonic-delay homodyne technology without cross correlation.

Study on low-phase-noise optoelectronic oscillator and high-sensitivity phase noise measurement system

An analytic model for an injection-locked dual-loop optoelectronic oscillator (OEO) is proposed and verified by experiments in this paper. Based on this theoretical model, the effect of injection power on the single-sideband phase noise of the OEO is analyzed, and results suggest that moderate injection is one key factor for a balance between phase noise and spur for OEO. In order to measure superlow phase noise of OEOs, a cross-correlation measurement system based on the fiber delay line is built, in which high linear photodetector and low-phase-noise amplifier are used to improve systematic sensitivity. The cross-correlation measurement system is validated by experiments, and its noise floor for the X band is about -130 dBc/Hz at 1 kHz and -168 dBc/Hz at 10 kHz after a cross correlation of 200 times.

Study and realization of loop filter of phase noise measurement system

Study and realization of loop filter of phase noise measurement system

Phase-Noise Measurement System for the Terahertz-Band

We present phase-noise measurements in support of terahertz electronics. By combining even-harmonic mixers with a 2.5 GHz frequency comb, we achieve a phase-noise measurement system in waveguide (WR1.5) by use of cross-spectral and digital phase-noise measurement techniques. At 670 GHz an upper bound of this system's noise floor is found to be -20, -40, and -60 dBc/Hz at 1, 100, and 10000 Hz offsets, respectively. In addition, a commercial, low-phase-noise, 670 GHz source is measured at offset frequencies from 0.1 Hz to 1 MHz.

Estimation of the uncertainty for a phase noise optoelectronic metrology system

The configuration of the phase noise measurement system operating in the X-band (8.2–12.4 GHz) using a photonic delay line as a frequency discriminator is presented in this paper. This system does not need any excellent frequency reference and works for any frequency in this band. Oscillator frequency fluctuation is converted into phase frequency fluctuation through the delay line. The measured phase noise includes the device under test noise and the instrument background. Then the use of a cross correlation decreases the cross spectrum terms of uncommon phase noise as √(1/m), where m is the average number. Using cross correlation on 500 averages, the noise floor of the instrument £(f) becomes, respectively, −150 and −170 dBc Hz−1 at 101 and 104 Hz from the 10 GHz carrier (−90 and −170 dBc Hz−1 including 2 km delay lines). We then focus on determining the uncertainty. There are two categories of uncertainty terms: ‘type A’, statistic contributions such as repeatability and experimental standard deviation; ‘type B’ due to various components and temperature control. The elementary term of uncertainty for repeatability is found to be equal to 0.68 dB. Other elementary terms still have lower contributions. This leads to a global uncertainty of 1.58 dB at 2σ.