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This paper investigates the effect of oscillator phase noise on a multiuser millimeter wave (mmWave) massive MIMO uplink as we scale up the number of base station antennas, fixing the load factor, defined as the ratio of the number of simultaneous users to the number of base station antennas. We consider a modular approach in which the base station employs an array of subarrays, or "tiles." Each tile supports a fixed number of antennas, and can therefore be implemented using a separate radio frequency integrated circuit (RFIC), with synchronization across tiles accomplished by employing a phased locked loop in each tile to synthesize an on-chip oscillator at the carrier frequency by locking on to a common lower frequency reference clock. Assuming linear minimum mean squared error (LMMSE) multiuser detection, we provide an analytical framework that can be used to specify the required power spectral density (PSD) mask for phase noise for a target system performance. Our analysis for the phase noise at the output of the LMMSE receiver indicates two distinct effects: self-noise for each user which is inversely proportional to the number of tiles, and cross-talk between users which is insensitive to the number of tiles, and is proportional to the load factor. These analytical predictions, verified by simulations for a 140 GHz system targeting a per-user data rate of 10 Gbps, show that tiling is a robust approach for scaling. Numerical results for our proposed design approach yield relatively relaxed specifications for phase noise PSD masks.

Cell-free massive multiple-input multiple-output (MIMO) is considered as a promising technology for satisfying higher rate requirement of users in beyond-5G networks. This paper investigates the impact of phase noise on the performance of cell-free MIMO systems which employ a large number of multi-antenna access points (APs). For both downlink and uplink transmissions, we derive the tractable closed-form achievable rate expressions when signal detection with channel state information (CSI) and channel distribution information (CDI), respectively, by utilizing the extended deterministic equivalence method in random matrix theory. The closed-form achievable rate expressions provide efficient evaluation for the impact of phase noise on system performance. The analytical results indicate that the phase noise influences the power of the desired signal, the beamforming uncertainty gain, and the inter-user interference increment caused by the pilot contamination. In addition, the special cases that only APs have phase noise and only users have phase noise are discussed. It is found that the impact of phase noise at users is more severe than that at APs. Besides, we discuss the system performance at low and high SNR regimes. It demonstrates that the phase noise is the major limitation of the system performance in high SNR regime while it can be neglected in low SNR regime. Furthermore, we formulate the max-min power control problem for both downlink and uplink transmissions to guarantee the users’ fairness and prove that the downlink max-min problem is a quasi-concave problem while the uplink max-min problem is a geometric programming (GP) problem. Then, the phase noise-aware max-min power control schemes for both downlink and uplink transmissions are proposed to ensure the users’ fairness. Finally, numerical results are provided to validate the analytical results and the proposed phase noise-aware power control scheme.

The oscillator phase noise is one of the key limitations in several fields of electronics. An electronic oscillator phase noise is usually described by the Leeson's equation. Since the latter is frequently misinterpreted and misused, a complete derivation of the Leeson's equation in modern form is given first. Second, effects of flicker noise and active-device bias are accounted for. Next the complete spectrum of an electronic oscillator is derived extending the result of the Leeson's equation into a Lorentzian spectral line. Finally the spectrum of more complex oscillators including delay lines is calculated, like opto-electronic oscillators.

In this work, the effect of oscillator phase noise on the bit error rate (BER) for high order QAM communication systems is analyzed. Two high frequency oscillators are designed, built and tested to get real phase noise data, and a BER simulation of a 1024 QAM signal through a super-heterodyne frequency down-converter is implemented using the measured data from the two oscillators as local oscillator sources for the down-converter. A third frequency source is also added to the simulation to visualize the dramatic effect of phase noise on the system BER analysis.

In this paper we investigate the direct effect of resonator quality factor ( $Q$ ) on the oscillator phase noise. We use 2-port contour mode resonators (CMRs), fabricated both with aluminum nitride (AlN) and aluminum scandium nitride (AlScN), as the frequency-determining element in the oscillator circuit. Over 70 oscillator configurations are tested using resonators with different $Q$ and with different piezoelectric layer. The testing of so many devices is possible because, in our setup, interfacing the circuit to the resonator is streamlined using RF probes. Our results show that higher resonator $Q$ yields better frequency stability of the oscillator, for both AlN and AlScN CMRs. Interestingly, the comparison between AlN-based oscillators and AlScN-based oscillators with equal $Q$ shows that AlScN-based oscillators’ Phase Noise is up 10 dBc/Hz better than the AlN oscillator at 1 kHz offset frequency, suggesting different intrinsic resonator flicker noise of the two piezoelectric layers. [2019-0200]

To meet the requirements of beyond 5G networks, the significant amount of unused spectrum in sub-TeraHertz frequencies is contemplated for high-rate wireless communications. Yet, the performance of sub-TeraHertz systems is severely degraded by strong oscillator phase noise. We investigate in this paper the design of digital communications robust to phase noise. This problem is addressed in three steps: the characterization of the phase noise channel, the design of the optimum receiver, and the optimization of the modulation scheme. This paper proposes a joint performance and implementation optimization. First, we address the design of the demodulation scheme for phase noise channels and propose the polar metric, a soft-decision rule for symbol detection. It is shown that performance gains are achieved for coded and uncoded systems with valuable complexity reductions of the receiver. Second, we investigate the optimization of the modulation scheme for phase noise. We demonstrate that using a constellation defined upon a lattice in the amplitude-phase domain leads to significant performance gains and a low-complexity implementation. Thereupon, we propose the Polar-QAM scheme with efficient binary labeling and demodulation. Numerical simulation results show that the proposed modulation and demodulation schemes offer valuable solutions to achieve high-rate communications on systems strongly impaired by phase noise.

Frequency delta sigma modulation (FDSM) is a unique analog to digital conversion technique featuring large dynamic range with wide frequency band width. It can be used for high performance digitaloutput sensors, if the oscillator in the FDSM is replaced by a variable frequency oscillator whose frequency depends on a certain external physical quantity. One of the most important parameters governing the performance of these sensors is a phase noise of the oscillator. The phase noise is an essential error source in the FDSM, and it is quite important for this type of sensors because they use a high frequency oscillator and an extremely large oversampling ratio. In this paper, we will discuss the quantitative effects of the phase noise on the FDSM output on the basis of a simple model. The model was validated with experiments for three types of oscillators. key words: delta sigma modulation, frequency delta sigma modulation, phase noise, microwave oscillator, Advance publication (published online immediately after acceptance)

Herein, a robust programmable stochastic weight generation method for a memristive neural network is proposed. There have been few prior algorithm suggestions for crossbar neural network‐based stochastic learning; however, there has not been much attention focussed on robust physical implementations. As a result, coming up with a robust method to provide the probability generator is an essential knob for its physical implementation. Here, implanting such stochastic behavior into the weight update signal itself is proposed, by multiplying it with the randomized probability sequence. To generate such probability sequence, bang‐bang dithering of a phase‐locked loop (PLL) with a binary phase detector (PD) is used. The programmable probability is enabled by introducing an offset for the PD outputs. Yet the dithering sequence has deterministic nature, phase noise of complementary metal–oxide–semiconductor (CMOS) ring oscillator to randomize the deterministic dithering is exploited. As a result, this lower power oscillator offers a better probability sequence, which enables an ultralow power circuit implementation.

International audience; The performance of sub-THz communications, contemplated for the next generation of wireless networks, are significantly degraded by oscillator phase noise. In this paper, we address the design of a single carrier transceiver resilient to phase noise. This problem is treated in two steps: First, we derive for phase noise channels the optimum symbol detection criterion. Second, we propose a phase noise robust modulation scheme with a comprehensive and efficient structure. System level simulations modeling the sub-THz propagation channel of a rich outdoor environment through ray tracing are also presented. Results show that optimizing the modulation and demodulation schemes is necessary to achieve high spectral efficiency in the presence of phase noise.

This paper shows how arrays of coupled resonant oscillators can provide wildly disordered phase responses corresponding to nonsynchronized regimes. The unpredictability of their time response makes oscillator arrays attractive randomness sources for cryptographic applications. We describe a possible implementation of a random number generator (RNG) combining the proposed randomness source with a few low cost elements needed for bit stream generation. Several bit stream sequences are simulated with a numerically efficient phase-domain model able to include oscillator phase noise and parameters variability. The randomness of the generated bit streams are checked with the tests provided by the National Institute of Standards and Technology. Our results show that the statistical properties of the proposed RNG are indeed resilient to temperature-induced thermal noise variations as well as to the statistical uncertainty of oscillating frequencies and coupling strengths.

We analyze the performance of a helmet-based frequency modulated continuous wave (FMCW) radar system for use in impact prediction in contact sports, or other risky environments. It has been shown that the head trauma and concussions can have significant detrimental effects on the health and quality life of contact sport athletes, from the high school to professional level. Impact prediction capability could be an important part of a comprehensive, helmet-based system for mitigating the neurological damage caused by impacts. Mitigation strategies include using imminent impact information in an audible warning system, or dynamic preloading and control of an active helmet suspension. Our analysis centers on the prediction of an impact offset parameter (and its uncertainty) in a representative player interaction scenario. We consider realistic radar measurement specifications consistent with our player interaction scenario, and COTS radar hardware, including oscillator phase noise, operation frequency, sweep frequency, bandwidth, range, target scattering cross-section, and antenna gain.

A high-resolution, high-bandwidth, and noise-scrambling, time-to-digital converter (TDC) is presented. Its architecture, which exploits harmonics in ring oscillators, provides a sample-and-hold mechanism in the form of relative phase. This storage mechanism is highly insensitive to noise and allows for oversampling between input events, therefore, can be designed for very high bandwidth. It can achieve lower quantization noise with fewer measurements than noise-shaping TDCs. This paper presents the architecture in detail, an in-depth analysis of noise sensitivity of the time storage mechanism, and the results from a prototype implemented in a 28-nm CMOS process.

When an antenna vibrates, it induces phase noise on the signals that it transmits and receives. This noise source is significant for microwave and millimeter-wave systems operating in high-vibration environments that require low phase noise at small frequency offsets. The purpose of this paper is to derive equations to compute phase noise from vibration parameters and to validate the equations with measurements. It is shown that the induced phase noise varies as ${f}_{v}^{-4}$ , where ${f}_{v}$ is the frequency of vibration. The results are then compared to the phase noise induced on an oscillator by vibration to determine the oscillator g sensitivity such that the oscillator and antenna phase noise contributions are equal. For state-of-the-art low-g-sensitivity oscillators, the phase noise contribution of the antenna can dominate at vibrational frequencies up to several kilohertz. The vibrational phase noise sensitivity of the antenna is also larger than the reported vibrational sensitivity of coaxial cables up to at least 1000-Hz vibrational frequencies and bandpass filters up to 300–1000-Hz vibrational frequencies depending on the filter quality factor.

In this paper, we present a bang-bang phase detector (BBPD) and a delay-line frequency discriminator-based phase noise filter (PNF). With a larger phase detection gain, the BBPD-based PNF enhances the sensitivity by suppressing the charge pump noise. A time-amplifier and a five times voting machine are introduced together with the sense-amplifier-flip-flop to minimize the BBPD noise to make its effects negligible in the PNF sensitivity. At 1-MHz offset, the PNF demonstrates 15-dB phase noise suppression with −120.2-dBc/Hz sensitivity. Its phase noise suppression offset frequency is from 100 kHz to 8 MHz with 10–10.1-GHz input frequency range. The circuit is fabricated in a 65-nm CMOS technology, and dissipates 98-mW power.

We present a novel Wiener smoothing filter procedure for pilot-symbol-assisted estimation of oscillator phase noise. The procedure consists of forward and backward first-order infinite impulse response filtering the pilot symbols and combining the filter outputs to generate an estimate of the phase noise. We analyze the mean-square-error performance of this pilot-symbol-assisted forward–backward Wiener smoothing filter (FBWSF) procedure and show its optimality under the assumption that the phase noise is modeled as a first-order autoregressive moving average process. We then apply the FBWSF as a code-aided phase noise compensation technique in an iterative receiver framework. The iterative receiver presented here first estimates phase noise roughly by using the pilot-symbol-assisted FBWSF; then, it refines the estimates with the code-aided version of FBWSF. The resulting receiver achieves excellent error performance at a feasible level of computational complexity.

Using the general expression of the phase variance expressed by the linear time variant (LTV) phase noise model, phase variances due to multi-Lorentzian and white noise sources of electrical oscillators have been extracted and phase noise expressions due to white and Flicker noises have been calculated. Despite the basic LTV model in which the expressed phase noise due to white noise is valid for offset frequencies larger than the −3 dB corner frequency of the output and it tends to infinity for small offset frequencies, in the proposed model, the extracted phase noises due to white and Flicker noises are valid for the entire spectrum and become limited for small offset frequencies. Comparison between the results of the proposed model by those of the harmonic balance technique shows the validity of the model. Also, the effects of the physical parameters of the oscillator circuit on the extracted phase noise can be observed in the expressions. The proposed model is applicable to calculate the phase noise of the oscillators with single perturbation source applied to the intended output node.

In this paper, we use synchronization to reduce phase-locked loop (PLL) phase noise and improve its locking behavior with an attenuated reference signal injection (RI) into a voltage-controlled CMOS delay-line ring-type oscillator. The transient and steady-state behavior of the PLL-RI are described by a nonlinear differential equation, which is further studied by the phase-plane method. The nonlinear equation is linearized for the small-signal condition and the s-domain noise transfer functions and noise bandwidths for different noise sources are derived. The effect of the loop parameters and the injection strength on the output phase noise, loop settling time, and lock in range is analyzed. Finally, the analysis is verified by the SPICE simulation and measurement results from an 1-GHz PLL-RI with 130-nm standard RF CMOS technology. Simulation and measurement results show phase noise reduction and improved settling behavior of a PLL-RI compared with a conventional PLL.

IEEE transactions on microwave theory and techniques 65(7), 2617 - 2624 (2017). doi:10.1109/TMTT.2016.2640286, We propose and theoretically and experimentally demonstrate a novel tunable spurious-free single-loop optoelectronic oscillator (OEO) with low drift and low-phase noise. In the proposed transposed-frequency OEO (TF-OEO), a nonreciprocal bias unit and an optical phase modulator in a fiber Sagnac interferometer function jointly as an intrinsically drift-free intensity modulator, which improves the long-term drift. Besides, a transposed-frequency low-noise filtered amplifier is used which replaces the conventional radio frequency (RF) bandpass filter (BPF) and RF amplifier with an intermediate frequency (IF) BPF, an ultralow phase noise IF amplifier, and a tunable local oscillator, to attain frequency tuning and singlefrequency selection with ultralow phase noise at the same time. The quality of the generated microwave signals is theoretically investigated and verified by experiments. Preliminary phase noise, frequency stability, spurious noise levels, and frequency tunability of the photonically generated microwave signal are also investigated. A microwave signal with a frequency tunable range of 15 MHz around 10.833 GHz is generated with no spurs. The generated microwave oscillation has a single-sideband phase noise of −120 dBc/Hz at 10 kHz offset from 10.833 GHz carrier, with 36 fs RMS timing jitter integrated from 1 kHz to 10 MHz. Long-term frequency stability measurements show ±0.05 ppm maximum fractional frequency deviation over 60 h, which is mainly limited by drift of the, Published by IEEE, New York, NY

We present a rigorous phase noise analysis of a generic harmonic oscillator where the active core can be modeled as a transconductor. Phase noise equations are derived without any specific assumption on the nature of the resonator in the oscillator; furthermore, we provide closed-form 1/f2 phase noise equations when the resonator consists of an arbitrary number of cascaded LC tanks, each tuned at a different harmonic of the oscillation frequency. We also show that the phase noise caused by transconductor white noise is always proportional to the phase noise caused by resonator losses, and that no flicker noise from the transconductor is up-converted into phase noise in an oscillator with an odd-symmetric voltage waveform. The phase noise for a number of different oscillators/resonators has been simulated, always obtaining an exceedingly good agreement between theoretical predictions and numerical results. (Less)

This work proposes a direct sequence spread spectrum transmitter with high transmission range and efficiency for audio signals. It is shown that by choosing high process gain for spread spectrum signal the data could reach a range of 55km in the 2.4GHz ISM band. By employing a light modulation scheme, we have a relaxed SNR requirement for having a low bit error rate (BER) which translates to relaxed error vector magnitude (EVM) condition. Therefore a switching power amplfier (PA) is used in this work which improves the transmitter’s efficiency while by taking PAs nonidealities into account we extracted the new equations to find the conditions to improve the efficiency compared to conventional zero current and zero current switching conditions. The PA efficiency is equal to 79.5% while having 30dBm output power. The mixer alongside power amplifier used in this work provide a conversion gain of 9 dB while having 16 dBm output compression point. The employed tunable quadrature oscillator has the ability to cancel phase and amplitude errors without comprimising the oscillator phase noise. The transmitter reaches an efficiency of 73.4% and an EVM of -32.75 dB.

The ideal behavior of communication system requires a single frequency carrier. In optical communication system, light is used as a carrier. Practical laser source has a finite linewidth due to variations in the frequency of operation, hence, resulting in undesired phase perturbations in the signal whereas the ideal requirement is the delta function spectral shape at the carrier frequency. The spectral shape gets broadened due to phase noise and is modeled as lorentzian shape. Linewidth is a measure of stability of laser phase noise with time. Coherent Optical Orthogonal frequency division multiplexing (CO-OFDM) along with the spectrally efficient Quadrature Amplitude Modulation (QAM) formats is emerging as one of the best solutions for future high speed fiber transmission systems. Though the coherent, receivers have advantages in terms of sensitivity and selectivity, laser phase noise is the main limitation of such systems as the laser phase noise further causes common phase rotation of all the subcarriers per symbol and also results in inter carrier interference. QAM formats are also susceptible to laser phase noise. Phase noise in coherent systems is governed by laser linewidth. Hence, it is very important to investigate the impact of laser linewidth in CO-OFDM systems. This paper investigates the tolerable laser linewidths for different QAM formats in a 40 Gbps COOFDM system.

This work presents a local oscillator (LO) phase noise model and its experimental validation for carrier to phase noise ratio (CPNR) and error vector magnitude (EVM) evaluation on a radio frequency (RF) transceiver. The proposed LO model is based on a type II charge pump phase locked loop with a combined phase noise source from the voltage controlled oscillator and input reference with a low pass characteristic. The obtained results of CPNR and signal to phase noise ratio are based on numerical simulations and validated with experimental measurements based on a commercial RF transceiver chip. The EVM of the transmitted RF channel is also measured and compared with CPNR.

We investigate the phase dynamics of a closed-loop MEMS-based oscillator and demonstrate how one can exploit nonlinear behavior to improve oscillator phase noise characteristics by synchronizing the oscillator with a weak harmonic drive. Analytical predictions are based on an oscillator model that incorporates a resonator element with a weak cubic (i.e., Duffing type) nonlinearity, weak coupling to a clean external harmonic drive, and both thermal and frequency noise terms. The method of stochastic averaging is used to derive an expression for the rate of phase diffusion induced by the noises, and the results predict a remarkable phase noise reduction of three order of magnitude when the oscillator is synchronized to the weak external field. The predictions are experimentally demonstrated using a closed-loop oscillator with a double-anchored double-ended-tuning-fork MEMS resonator with coupling to a small external sinusoidal signal from a signal generator, demonstrating a 30 dB/Hz drop in phase noise. The results show how one can generate a clean high-power signal from a relative noisy oscillator by synchronizing it with a low-power external signal. The results also confirm recent studies showing that the parameter range of synchronization is significantly expanded when the resonator operates in its nonlinear regime. [2016-0067]

In this paper, the effects of oscillator phase noise (PN) with arbitrary spectral characteristics on the self-interference (SI) cancelation capability of a full-duplex radio (FDR) transceiver are addressed, and design considerations for optimized phase-locked loop (PLL) design in FDR are given. This paper first presents a full-duplex transceiver model that inherently mitigates most of the phase-noise effects from the SI signal. The remaining effect of the PN is then analyzed, and closed-form expressions for the SI power are derived. In the simulations part, a practical PLL-type oscillator is used, which is based on the arbitrary mask phase-noise model. Analytical derivations are verified with the simulations, and the SI cancelation performance is thoroughly studied with various parameters. Design considerations are finally given for oscillator design in FDR transceivers, with the help of tangible parameters of the PLL-type oscillators.

In this paper, we showed the phase noise of voltage controlled oscillator(VCO) can be radically improved using FLL(Frequency Locked Loop). At first, a 5 GHz VCO is fabricated using a hair-pin resonator. The fabricated VCO shows a phase noise of -53.1 dBc/Hz at 1 kHz frequency offset. In order to improve the phase noise of the fabricated VCO, a FLL is constructed using the feedback loop that consists of the VCO, a frequency detector composed of 5 GHz resonator, loop-filter, and level shifter. The fabricated FLL is designed to oscillate at a frequency of 5 GHz, and its measured phase noise is about -120.6 dBc/Hz at 1 kHz offset frequency. As a result, the phase noise of VCO can be radically improved by about 67.5 dB applying FLL. In addition, the measured phase noise performance is close to that of crystal oscillator.

Modeling tank losses in a harmonic oscillator by means of an equivalent parallel resistance may lead to an optimistic estimate of phase noise, as recently experienced in a class-D CMOS oscillator. The discrepancy is significant if two conditions are fulfilled: The single-ended portion of the tank capacitance displays a non-negligible loss, and the loop gain of the oscillator is very large; in the latter case, a phase noise boost is likely to occur. In this brief, we derive phase noise equations that capture such behavior in a class-B oscillator, which is easier to approach than a class-D oscillator. The results, however, are (qualitatively) valid in general. Furthermore, the phase noise caused by the oscillator active core is always proportional to the phase noise caused by the tank losses independently of the amount of phase noise boost. The agreement between theoretical and simulation results is excellent.

Oscillator phase noise (PHN) can result in significant performance loss in coherent communication systems if not compensated appropriately. Most existing studies focus on either PHN estimation over additive white Gaussian noise channels or channel impulse response (CIR) estimation in the absence of PHN. In this study, joint CIR estimation and decoding over time-selective flat-fading channels impacted by PHN is studied. Both the time evolutions of CIR and PHN are approximated by autoregressive models. Building on this, factor graph of the joint a posteriori probability function is constructed and the sum–product algorithm is applied to derive messages on factor graph. Due to the non-linearity of PHN, no closed-form expressions of the messages can be obtained. To this end, the authors use canonical distribution approach, which approximates the messages by Gaussian and Tikhonov probability density functions on the sub-graphs of CIR and PHN, respectively. Accordingly, the messages can be calculated by updating the parameters of the canonical distributions. A mixed serial-parallel message passing schedule is presented to implement the algorithm, which enables the compromise between the bit error rate performance and the processing throughput. Simulation results show that the proposed joint estimation and decoding algorithm significantly outperforms the existing methods in fading channels impacted by PHN.

In this letter, the design of a low phase noise frequency synthesizer is presented. The synthesizer was designed to produce four frequencies: 10 MHz, 100 MHz, 1 GHz and 10 GHz. The 1-GHz signal is produced by frequency division whereas the 100-MHz output is generated by phase-locking a low phase noise oscillator to the 1-GHz signal, hence significantly reducing its phase noise. Both residual and total phase noise measurements are presented.

The effect of phase noise introduced by optical sources in spectrally-sliced optically enabled DACs and ADCs is modeled and analyzed in detail. In both data converter architectures, a mode-locked laser is assumed to provide an optical comb whose lines are used to either synthesize or analyze individual spectral slices. While the optical phase noise of the central MLL line as well as of other optical carriers used in the analyzed system architectures have a minor impact on the system performance, the RF phase noise of the MLL fundamentally limits it. In particular, the corresponding jitter of the MLL pulse train is transferred almost one-to-one to the system-level timing jitter of the data converters. While MLL phase noise can in principle be tracked and removed by electronic signal processing, this results in electric oscillator phase noise replacing the MLL jitter and is not conducive in systems leveraging the ultra-low jitter of low-noise mode-locked lasers. Precise analytical models are derived and validated by detailed numerical simulations.

Providing high-capacity radio connectivity for high-speed trains (HSTs) is one of the most important use cases of emerging 5G New Radio (NR) networks. In this article, we show that 5G NR technology can also facilitate high-accuracy continuous localization and tracking of HSTs. Furthermore, we describe and demonstrate how the NR network can utilize the continuous location information for efficient beam-management and beamforming, as well as for downlink Doppler precompensation in the single-frequency network context. Additionally, with particular focus on millimeter wave networks, novel concepts for low-latency intercarrier interference (ICI) estimation and compensation, due to residual Doppler and oscillator phase noise, are described and demonstrated. The provided numerical results at 30 GHz operating band show that sub-meter positioning and sub-degree beam-direction accuracies can be obtained with very high probabilities in the order of 95-99%. The results also show that the described Doppler precompensation and ICI estimation and cancellation methods substantially improve the throughput of the single-frequency HST network., Comment: This article has been submitted to IEEE Communications Magazine for a publication. This is the first revised version of the original article and is now under second review round

Satellite Precoding is a promising technique to meet the target data rates of the future high throughput satellite systems and the costs per bit as required by 5G applications and networks, but it requires strict synchronization among the transmitted waveforms, in addition to accurate channel state information. Most of the published work about this topic consider ideal oscillators, but in practice, the output of an oscillator is not a single spectral line at the nominal frequency. This paper proposes a model for the oscillator phase noise and analyzes the resulting received signal to interference plus noise ratio (SNIR) in a satellite communication system using Precoding. Simulations of a communication satellite system with a two-beam transponder and two receivers were performed to compute the effective SNIR. This work uses a simulator which also considers practical impairments such as time misalignment, errors in the channel state information, interference, thermal noise and phase noise masks for satellite oscillators. The Precoding methods used for the analysis are Zero Forcing (ZF) and Minimum Mean Square Error (MMSE). The obtained results prove that there is a degradation in the performance due to the use of independent oscillators but this effect is compensated by the precoding matrix.

International audience; In‐band full‐duplex (FD) transceiver has been recently proposed to double the channel efficiency. The main challenge of such FD transceiver consists in achieving an efficient self‐interference cancelation. This fact is prevented by receiver imperfections such as the oscillator phase noise, the analog‐to‐digital converter noise, and the nonlinear distortion (NLD) of the low‐noise amplifier (LNA). This paper deals with the mitigation of the NLD of the receiver's LNA by proposing a new FD transceiver architecture. Based on the fact that the NLD coefficients are changing slowly over time, then the period between two successive estimations of the NLD coefficients may be relatively long. Motivated by this fact, a new wire connection is introduced between the transmitting circuit and the receiving one in order to neglect the wireless channel effects when estimating the NLD coefficients. If the estimation of the NLD coefficients is required, then the transmitter stops the wireless transmission and sends a sequence to the receiver via the wire channel. This procedure does not affect the throughput rate since it is repeated every several frames due to the slow time‐variation of the NLD coefficients. The estimated coefficients are used to attenuate the effects of NLD at the receiver's side, where an auxiliary chain is introduced to act as reference to the receiver's ordinary chain. As a proof of the concept, intensive simulations have been done using realistic data parameters. Our numerical results corroborate the efficiency of the proposed architecture, where the NLD of LNA is highly attenuated leading to an efficient self‐interference cancelation.

Concepts for the generation and the measurement of highly linear frequency ramps are presented. The fractional ramp synthesiser concept shown here is able to generate frequency ramps with a very low phase noise level, a very good frequency linearity and reproducibility. Related to the bandwidth of the generated frequency ramps of 4.5 GHz a relative linearity error below 4·10–10 is demonstrated in a prototype system. This linearity error is close to the limit set by the phase noise floor of the ramp generators and marks a significant improvement over existing aproaches (Musch and Schiek, 2000). The basic measurement sensitivity due to the phase noise is 1.8·10–10 without averaging. As the phase noise is important for the linearity of the frequency ramp the set-up has to be optimised for a good phase noise behaviour, too. In order to achieve this good phase noise a special phase-frequency detector is introduced that is especially designed for the use in a fractional phase locked loop.

Oscillators are often followed by square wave forming circuits and frequency dividers. Traditionally, the level of the phase noise, transferred from the oscillator outputs to the square waves obtained is calculated ignoring the correlations in the oscillator phase noise spectrum. In this paper, accurate expressions are derived, taking into account the phase noise mechanisms in the oscillators. The phase noise power spectral densities are calculated in both the traditional way and by using the proposed expressions and they are compared. The situations where the proposed expressions can be useful are identified.

We investigate the dynamics of a pair of noisy coupled oscillators and derive operating conditions that minimize phase noise. The generic model employed allows for general nonlinear dynamics of the resonant elements of the oscillators, in terms of their amplitude-dependent frequencies, general asymmetric coupling, and both additive and multiplicative noise sources. The model is analyzed using the method of stochastic averaging and the results suggest an optimal operating point for minimizing phase noise in either of the oscillators by varying the operating amplitudes and the nature and strength of the coupling. We also show that the system with asymmetric coupling has the ability to reduce the phase noise of the noisier oscillator beyond the expected result for synchronized oscillators. The analytical predictions, which are validated by Monte-Carlo simulations, show how one can exploit nonlinear behavior to improve phase noise characteristics using a pair of coupled oscillators. The results also point to a means of designing and optimizing larger sets of coupled oscillators to improve phase noise performance.