Phase Noise Values Research Articles

Microwave Photonic Frequency Multiplier with Low Phase Noise Based on an Optoelectronic Oscillator

A microwave photonic frequency multiplier with low phase noise based on an optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. In this scheme, a dual-parallel Mach–Zehnder modulator (DPMZM) is employed to generate the third-harmonic frequency of the input radio frequency (RF) signal, while the oscillation frequency of the OEO is also three times the RF signal frequency. By adjusting the bias voltages of different arms in the DPMZM, a triple-frequency signal with a high side-mode suppression ratio of 64.8 dB can be obtained. The experimental results indicate that the output of the frequency-multiplier has a better single-sideband phase noise value, for instance, −126 dBc/Hz@10 kHz at 20.019 GHz. It has improvements of 34 dB and 43.5 dB compared with the input RF signal and the simulated electrical frequency tripler module, respectively.

Residual phase noise measurements of elements of the radio frequency path of radiometric receivers

In this work, the measurement of the residual phase noise of amplifiers and frequency multipliers using frequency doublers and step recovery diodes, were performed utilizing the interferometric method. The results obtained showed the possibility of using the interferometric method in measuring the phase noise of radio frequency paths of radiometric receivers. The measured values of residual phase noise can be used to evaluate the characteristics of the radio frequency paths of receivers.

Analysis and Implementation of a Frequency Synthesizer Based on Dual Phase-Locked Loops in Cesium Atomic Clock

The frequency synthesizer plays a crucial role in atomic clock technology. In this study, we demonstrate a direct microwave frequency synthesizer for a cesium atomic clock, employing frequency multiplication and a dual-phase-locked loop mode. A mathematical model of the frequency synthesis chain is established to estimate its performance. The phase-settling time and system stability are analyzed and studied in detail, and the obtained results are verified by experiments. An optimized realization of the frequency synthesizer shows that the phase-settling time can be adjusted within the range of 644.5 µs to 1.5 ms. Additionally, we measure the absolute phase noise values to be −63.7 dBc/Hz, −75.7 dBc/Hz, −107.1 dBc/Hz, and −122.5 dBc/Hz at 1 Hz, 10 Hz, 1 kHz, and 10 kHz offset frequencies, respectively.

Coherent dual-frequency signal generation in an optoelectronic oscillator.

Coherent dual-frequency microwave signal generation using an optoelectronic oscillator (OEO) is presented and demonstrated. In the proposed OEO, a dual-band bandpass filter (DB-BPF) is utilized to select two oscillation modes. An external signal is injected into the OEO loop with its frequency equaling the frequency interval of the two oscillation modes. Owing to the modulation nonlinearity of the Mach-Zehnder modulator, the two oscillation frequencies interact with the injection frequency. When the phase and gain conditions are satisfied within the loop, injection locking between the two oscillation signals will be established, and their phases will be synchronized. The effect of gain competition in the OEO loop, which leads to single-frequency oscillation, is suppressed. An experiment is carried out, and two frequencies, of 16.083 GHz and 9.998 GHz, are generated at the same time. The phase noise values are -140.1 and -141.0 dBc/Hz @ 10 kHz, respectively. The coherence between the generated signals and sidemode suppression performance are evaluated.

Local Oscillator Phase Noise Impact on M-ary Modulation Schemes

This paper presents the impact of a local oscillator phase noise on digital modulation schemes based on bit error rate and error vector magnitude. The adopted methodology enables base band metrics estimation which is dependent of a specific communication standard. A generic local oscillator phase noise model is presented to evaluate the impact of different phase noise values on error vector magnitude and bit error rate. For a phase noise of -65dBc @ 1kHz the error vector magnitude changes from 7% to 12.8%. Increasing the modulation order leads to bit error rate increment for the same phase noise value.

Supply less sensitive ring voltage-controlled oscillator for microwave L-band frequencies

PurposeThe primary aim of this paper is to present a novel design approach for a ring voltage-controlled oscillator (VCO) suitable for L-band applications, whose oscillation frequency is less sensitive to power supply variations. In a few decades, with the advancement of modern wireless communication equipment, there has been an increasing demand for low-power and robust communication systems for longer battery life. A sudden drop in power significantly affects the performance of the VCO. Supply insensitive circuit design is the backbone of uninterrupted VCO performance. Because of their important roles in a variety of applications, VCOs and phase locked loops (PLLs) have been the subject of significant research for decades. For a few decades, the VCO has been one of the major components used to provide a local frequency signal to the PLL.Design/methodology/approachFirst, this paper chose to present recent developments on implemented techniques of ring VCO design for various applications. A complementary metal oxide semiconductor (CMOS)-based supply compensation technique is presented, which aims to reduce the change in oscillation frequency with the supply. The proposed circuit is designed and simulated on Cadence Virtuoso in 0.18 µm CMOS process under 1.8 V power supply. Active differential configuration with a cross-coupled NMOS structure is designed, which eliminates losses and negates supply noise. The proposed VCO is designed for excellent performance in many areas, including the L-band microwave frequency range, supply sensitivity, occupied area, power consumption and phase noise.FindingsThis work provides the complete design aspect of a novel ring VCO design for the L-band frequency range, low phase noise, low occupied area and low power applications. The maximum value of the supply sensitivity for the proposed ring VCO is 1.31, which is achieved by changing the VDD by ±0.5%. A tuning frequency range of 1.47–1.81 GHz is achieved, which falls within the L-band frequency range. This frequency range is achieved by varying the control voltage from 0.0 to 0.8 V, which shows that the proposed ring VCO is also suitable for low voltage regions. The total power consumed by the proposed ring VCO is 14.70 mW, a remarkably low value using this large transistor count. The achievable value of phase noise is −88.76 dBc/Hz @ 1 MHz offset frequency, which is a relatively small value. The performance of the proposed ring VCO is also evaluated by the figure of merit, achieving −163.13 dBc/Hz, which assures the specificity of the proposed design. The process and temperature variation simulations also validate the proposed design. The proposed oscillator occupied an extremely small area of only 0.00019 mm2 compared to contemporary designs.Originality/valueThe proposed CMOS-based supply compensation method is a unique design with the size and other parameters of the components used. All the data and results obtained show its originality in comparison with other designs. The obtained results are preserved to the fullest extent.

A parity-time-symmetric optoelectronic oscillator with polarization multiplexed channels

In this manuscript, we experimentally demonstrate a parity-time-symmetric optoelectronic oscillator (OEO) with polarization multiplexed channels. We obtained a microwave single-mode oscillation at 9.5 GHz with phase noise values of −116.2 and −122.3 dBc Hz−1 at 10 kHz offset frequencies, and side mode suppression values below −68 and −75 dBc Hz−1, by utilizing a 1 km long and 5 km long single mode fiber delay lines, respectively. Our experimental results suggest that parity-time-symmetric OEOs with polarization multiplexed channels are simple and cost-efficient alternatives to their more complex counterparts.

All-optical microwave oscillator using cross-gain modulation of semiconductor optical amplifier and cascaded stimulated Brillouin scattering effects in optical fiber

In this paper, an all-optical microwave oscillator is proposed and experimentally demonstrated. Via cascaded stimulated Brillouin scattering effects, the second-order Stokes wave can be obtained. A microwave envelope can be generated by beating the continuous wave and the second-order Stokes wave. The functions of microwave envelope detection and feedback modulation are implemented by using cross-gain modulation of a semiconductor optical amplifier, further, the Vernier effect is used to improve the microwave signal. The second Brillouin-selective sideband amplification is employed to enhance oscillation frequency. In this reported scheme, the electrical microwave devices such as high-Q electrical bandpass filter and electro-optic modulator are not required in the microwave oscillation feedback loop. This all-optical microwave oscillator can shake off the electronic block. Meanwhile, the frequency of the generated microwave signal is twice the Stokes frequency shift of the stimulated Brillouin scattering. Furthermore, it can also result in phase noise reduction that only one laser source is used here. Finally, coupled cavities are used to suppress the harmonic presentation. The experimental results show that the all-optical microwave oscillator can generate a single-mode-microwave-oscillation signal with a frequency of 21.66 GHz. The phase noise value at 10 kHz frequency offset is −90 dBc/Hz.

Low-Timing-Jitter and Low-Phase-Noise Microwave Signal Generation Using a VCSEL-Based Optoelectronic Oscillator

This article presents the first results of the timing-jitter characterization of a VCSEL-based optoelectronic oscillator (VBO) at 2,5GHz. For all implementations, vertical-cavity surface-emitting lasers (VCSEL) emitting in the O and C-bands were characterized. The resonant cavity was modified through the optical delay line length to verify its impact on timing-jitter and phase noise of the VBO. The lowest peak-to-peak jitter value obtained experimentally was 71 mUI when the optical fiber length was 1 km, whereas the lowest phase noise was -124 dBc/Hz with 5 km. This phase noise value, measured at 10 kHz offset, represents an 8 dB improvement compared to previous results, and it is the lowest value reported in the literature for the VBO architecture at 2,5GHz.

Phase noise model for continuous-variable quantum key distribution using a local local oscillator

The value of residual phase noise, after phase compensation, is one of the key limitations of performance improvement for continuous-variable quantum key distribution using a local local oscillator (LLO CV-QKD) system, since it is the major excess noise. However, due to the nonideality of the realistic devices implemented in practice, for example, imperfect lasers, detectors, and unbalanced interferometers, the value of residual phase noise in the current system is still relatively large. Here, we develop a phase noise model to improve the phase noise tolerance of the LLO CV-QKD schemes. In our model, part of the phase-reference measurement noise associated with detection efficiency and electronic noise of Bob's detector as well as a real-time monitored phase-reference intensity at Bob's side is considered trusted because it can be locally calibrated by Bob. We show that using our phase noise model can significantly improve the secure key rate and transmission distance of the LLO CV-QKD system. We further conduct an experiment to substantiate the superiority of the phase noise model. Based on experimental data of a LLO CV-QKD system in the 25-km optical fiber channel, we demonstrate that the secure key rate under our phase noise model is approximately 40% higher than that under the conventional phase noise model.

Experimental demonstration of 1.3 μm VCSEL‐based optoelectronic oscillator at 12 GHz using optical injection‐locking technique

The experimental validation is presented of an optical injection-locked (OIL) vertical-cavity surface-emitting laser (VCSEL)-based optoelectronic oscillator (VBO) to overcome the direct-modulation bandwidth limitations of packaged VCSELs. A 1.3 μm VCSEL under OIL is directly modulated at 12 GHz. The carrier phase noise value is −97.7 dBc/Hz at 10 kHz offset. A time domain characterisation of the oscillator based on Allan variance is proposed. The performed measurements showed that the OIL technique allows an increase in the optoelectronic oscillator (OEO) carrier frequency in comparison with free-running VBOs while maintaining high spectral purity. The results for a 12 GHz delay-line OEO with amplitude modulation are also compared with the proposed approach.

One‐third optical frequency divider for dual‐wavelength optical signals based on an optoelectronic oscillator

An optical frequency divider for dual-wavelength optical signals based on an optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The Mach-Zehnder modulator in the OEO is biased at the minimum transmission point, the OEO-based frequency divided signal originates from system noise. When the oscillation phase and amplitude conditions met, it gets stabilised at an oscillation frequency which is one-third of the frequency interval of the injected dual-wavelength optical signal. A proof-of-concept experiment is verified. With the frequency interval of the dual-wavelength optical signal ranging from 101.4 to 120.6 GHz, the RF signals ranging from 33.8 to 40.2 GHz are successfully generated. The power ripple is lower than 2.92 dB and the rejection ratio of the harmonic components is larger than 39 dB for all the conditions. The phase noise values of the generated RF signals are kept to be around -105 dBc/Hz@10 kHz.

Design and Analysis of Varactorless 65 nm MMW Voltage Controlled Oscillator

In this work a novel inductive tuning technique for millimeter wave (mmw) applications is presented. Fine frequency tuning is performed using a transformer. For the LC tanks inductive element, transformer is used. To tune the VCO MOS switch is placed at center tapping of the secondary coil of the transformer. The simulation shows that by changing the operating condition of MOS switch frequency band from 59.1 GHz to 64.6 GHz is obtained. The proposed 60 GHz VCO is designed using UMC 65 nm CMOS single Poly eight Metal (1P8M) Technology. Obtained Frequency Tuning Range (FTR) is 8.89% and the corresponding phase noise variation is from − 112.4 dBc/Hz to − 115.9 dBc/Hz at 10 MHz offset from the carrier. The worst phase noise value is − 112.4 dBc/Hz which is obtained at 0.3 V tuning voltage. For 0.8 V supply voltage 7.44 mW of power is dissipated. And the calculated Figure of Merit (FOM) for whole FTR, ranges from − 179.89 dBc/Hz to − 182.62 dBc/Hz.

Self-interference cancelation in the presence of non-linear power amplifier and receiver IQ imbalance

In the in-band full-duplex(FD) systems, the self-interference (SI) power can be more than 100 dB higher than the power of the received data signal. In order to enable the FD transmission, several SI cancelation stages are needed in a FD transceiver. By combining the cancelation at the radio frequency (RF) with a specially designed antenna and cancelation circuitry and SI cancelation at the digital baseband, the required level of SI cancelation can be achieved even with a non-linear power amplifier. In this paper, a FD transceiver architecture is modeled with simulation tools that allow to use realistic antenna and analog transceiver models and at the same time enable algorithm studies. The analog SI cancelation at the RF is controlled by the baseband digital processing unit, and the tuning of the RF canceler is performed with an automatic gain control enhanced iterative algorithm. The combined cancelation performance of the antenna and RF canceler varies between 62 and 82 dB depending on the studied cases. The digital baseband SI cancelation is based on the Hammerstein model in order to take the power amplifier non-linearity into account. The coefficients of the Hammerstein model are estimated with a self-orthogonalizing adaptive algorithm. When realistic phase noise and IQ imbalance values are taken into account, the SI after all the cancelation stages can decrease the signal-to-interference-and-noise-ratio (SINR) by few decibels (dB). In order to further enhance the SI cancelation, the Hammerstein based SI canceler is extended to cancel also the effect of the receiver IQ imbalance. With the extended baseband canceler, the cancelation performance is mainly limited by the phase noise

A sub-harmonic injection locking clock multiplier with FLL PVT calibrator

Using the sub-harmonic injection locking technique, an enhanced differential Digitally Controlled Ring Oscillator (DCRO) with improved phase noise performance is proposed in this paper. All circuit blocks were implemented using digital design flow and designed using a hardware description language. A Frequency Locked Loop-based Process, Voltage and Temperature (PVT) calibrator was utilized to overcome PVT variations. The design was fabricated in 65 nm CMOS technology and its area is 0.017 mm2. The measured phase noise at 1 MHz offset and RMS jitter are −128 dB/Hz and 197fs, respectively. The design was tested in the presence of voltage and temperature variations. The maximum jitter difference percentage is 13.7% at 70 °C and 1.1 V and the phase noise value changes by a maximum of 0.7 dB over the whole range of voltages and temperatures. Furthermore, when the design was tested in the presence of switching noise, it provides up to 7 dB improvement in phase noise when compared to a single ended version of the DCRO.

A 1.8 V 18.13 MHz Inverter-Based On-Chip RC Oscillator with Flicker Noise Suppression Using Logic Transition Voltage Feedback

An inverter-based on-chip resistor capacitor (RC) oscillator with logic transition voltage (LTV) tracking feedback for circuit delay compensation is presented. In order to achieve good frequency stability, the proposed technique considers the entire inverter chain as a comparator block and changes the LTV to control the oscillation frequency. Furthermore, the negative feedback structure also reduces low-frequency offset phase noise. With a 1.8 V supply and at room temperature, the suggested oscillator operates at 18.13 MHz, consuming 245.7 μ W. Compared to the free-running case, the proposed technique reduces phase noise by 7.7 dB and 5.45 dB at 100 Hz and 1 kHz, respectively. The measured phase noise values are −60.09 dBc/Hz at 1 kHz with a figure of merit (FOM) of 151.35 dB/Hz, and −106.27 dBc/Hz at 100 KHz with an FOM of 157.53 dBc/Hz. The proposed oscillator occupies 0.056 mm2 in a standard 0.18 μ m CMOS process.

Multicast-enabled high-speed VCSEL technology for flexible data center networks

We experimentally demonstrate the multiple signal modulation on a single class 10 G vertical cavity surface emitting laser (VCSEL) carrier at 1 310 nm for next generation multicast-enabled data center networks. A 10 Gbit/s data signal is directly modulated onto a single mode VCSEL carrier. To maximize carrier spectral efficiency, a 2 GHz reference frequency (RF) clock tone is simultaneously modulated on the VCSEL phase attribute. The inherent VCSEL orthogonal polarization bistability with changing bias current is further exploited in transmission of a polarization based pulse per second (PPS) timing clock signal. Therefore, we simultaneously transmit a 10 Gbit/s directly modulated data, 2 GHz phase modulated RF and a polarization- based PPS clock signals using a single mode 10 GHz bandwidth VCSEL carrier. It is the first time that a single class 10 G VCSEL carrier is reported to transmit a directly modulated data, phase modulated RF clock and polarization based PPS timing signal simultaneously in a single wavelength. A of G.652 single mode fibre (SMF) transmission over 3.21 km is experimentally attained. A receiver sensitivity of −15.60 dBm is experimentally obtained for the directly modulated 10 Gbit/s data signal. A 3.21-km-long SMF transmission introduces a penalty of 0.23 dB to the data signal. The contribution of a 2 GHz phase modulated RF and a polarization-based PPS clock signal to this penalty is found to be 0.03 dB. An RF single- side band (SSB) phase noise values of −82.36 dBc/Hz and −77.97 dBc/Hz are attained without and with simultaneous directly modulated data and polarization-based PPS clock signals respectively for a 3.21-km-long SMF transmission. This work provides an alternative efficient and cost effective technique for simultaneous high-speed multiple information transmission to different network nodes within a data center network through shared network infrastructure.

Integrated optoelectronic oscillator

With the rapid development of the modern communication systems, radar and wireless services, microwave signal with high-frequency, high-spectral-purity and frequency tunability as well as microwave generator with light weight, compact size, power-efficient and low cost are increasingly demanded. Integrated microwave photonics (IMWP) is regarded as a prospective way to meet these demands by hybridizing the microwave circuits and the photonics circuits on chip. In this article, we propose and experimentally demonstrate an integrated optoelectronic oscillator (IOEO). All of the devices needed in the optoelectronic oscillation loop circuit are monolithically integrated on chip within size of 5×6cm2. By tuning the injection current to 44 mA, the output frequency of the proposed IOEO is located at 7.30 GHz with phase noise value of -91 dBc/Hz@1MHz. When the injection current is increased to 65 mA, the output frequency can be changed to 8.87 GHz with phase noise value of -92 dBc/Hz@1MHz. Both of the oscillation frequency can be slightly tuned within 20 MHz around the center oscillation frequency by tuning the injection current. The method about improving the performance of IOEO is carefully discussed at the end of in this article.

An injection-locked OEO based frequency doubler independent of electrical doubler phase noise deteriorating rule

We propose an injection-locked optoelectronic oscillator (OEO) based wide-band frequency doubler, which is free from phase noise deterioration in electrical doubler, by using a dual-parallel Mach–Zehnder modulator (DPMZM). Through adjusting the optical phase shifts in different arms of the DPMZM, the doubling signal oscillates in the OEO loop while the fundamental signal takes on phase modulation over the light and vanishes at photo-detector (PD) output. By controlling power of fundamental signal the restriction of phase-noise deterioration rule in electrical doubler is totally canceled. Experimental results show that the doubler output has a better phase noise value of, for example, −117 dBc/Hz @ 10 kHz at 6 GHz with an improvement more than 17 dB and 23 dB compared with that of fundamental input and electrical doubler, respectively. Besides, the stability of this doubler output can reach to 1.5×10−14 at 1000 s averaging time. The frequency range of doubling signal is limited by the bandwidth of electrical amplifier in OEO loop.

Confidence Estimates in Simulation of Phase Noise or Spectral Density.

In this paper, we apply the method of discrete simulation of power-law noise, developed by Timmer and König, Ashby, and Ashby and Patla, to the problem of simulating phase noise for a combination of power-law noises. We derive analytic expressions for the probability of observing a value of phase noise L(f) or of any of the one-sided spectral densities Sϕ(f), Sy(f) , or Sx(f) , for arbitrary superpositions of power-law noise.