Local Oscillator Phase Noise Research Articles

Performance Estimation for Broadband Multi-Gigabit Millimeter- and Sub-Millimeter-Wave Wireless Communication Links

With the growing interest in high-speed millimeter-wave (mmw) and sub-mmw communication links, detailed studies on the performance limits introduced by nonideal frontend characteristics, e.g., in-phase/quadrature amplitude and phase imbalance, as well as local oscillator phase noise, become indispensable. Only with a detailed insight into the system’s behavior, a proper dimensioning and optimization of such wireless links is possible. In this paper we present a performance estimation for broadband wireless links dedicated to multiple tens of Gbit data rate based on known approaches and verify the validity of the estimation by comparison with measurements performed on an E-band wireless frontend. For quadrature phase-shift keying modulated signals and symbol rates of 2 and 5 GBd, the relative error between estimation and measurement is between 1.1 and 2.1%. Furthermore, the estimation approach is used to investigate the performance limiting imperfection of wireless systems operating in the sub-mmw frequency range. Besides the channel noise, the phase noise of the carrier signal is determined as the main limiting factor, especially for systems utilizing extremely broadband modulation bandwidths.

Analytical BER performance in differential n-PSK coherent transmission system influenced by equalization enhanced phase noise

Long-haul high speed optical transmission systems are significantly distorted by the interplay between the electronic chromatic dispersion (CD) equalization and the local oscillator (LO) laser phase noise, which leads to an effect of equalization enhanced phase noise (EEPN). The EEPN degrades the performance of optical communication systems severely with the increment of fiber dispersion, LO laser linewidth, symbol rate, and modulation format. In this paper, we present an analytical model for evaluating the performance of bit-error-rate (BER) versus signal-to-noise ratio (SNR) in the n-level phase shift keying (n-PSK) coherent transmission system employing differential carrier phase estimation (CPE), where the influence of EEPN is considered. Theoretical results based on this model have been investigated for the differential quadrature phase shift keying (DQPSK), the differential 8-PSK (D8PSK), and the differential 16-PSK (D16PSK) coherent transmission systems. The influence of EEPN on the BER performance in term of the fiber dispersion, the LO phase noise, the symbol rate, and the modulation format are analyzed in detail. The BER behaviors based on this analytical model achieve a good agreement with previously reported BER floors influenced by EEPN. Further simulations have also been carried out in the differential CPE considering EEPN. The results indicate that this analytical model can give an accurate prediction for the DQPSK system, and a leading-order approximation for the D8PSK and the D16PSK systems.

An effect of phase noise for an indoor wireless system

This paper gives an overview of 60GHz indoor wireless channel characteristics and an effect on phase noise. The performance of OFDM system is severely degraded by the local oscillator phase noise, which causes both common phase error (CPE) and inter-carrier interference (ICI). In this paper, the phase noise suppression (PNS) algorithm in order to reduce the phase noise in OFDM-based 60GHz WPANs is considered. The PNS algorithm is very simple and easily designed to realize system but it requires more effort to reduce the IC.

Local oscillator phase noise limitation on the resolution of acoustic delay line wireless passive sensor measurement.

The role of the phase noise of a local oscillator driving a pulsed-mode RADAR used for probing surface acoustic wave sensors is investigated. The echo delay, representative of the acoustic velocity, and hence the physical quantity probed by the sensor, is finely measured as a phase. Considering that the intrinsic oscillator phase fluctuation defines the phase noise measurement resolution, we experimentally and theoretically assess the relation between phase noise, measurement range, and measurand resolution.

무선 LAN 시스템 성능개선에 관한 연구

본 논문은 4세대 무선 통신방식의 하나인 OFDM 기반의 60 GHz 무선 랜에서의 위상잡음의 영향에 관하여 논한다. 60 GHz 주파수 대역은 광대역 전송이 가능할 뿐만 아니라 실내 무선 환경에서의 무선 링크를 밀집 시킬 수 있다는 장점이 있다. 본 논문에서는 시스템 구현이 용이한 위상잡음 억제 알고리듬을 OFDM 기반의 60 GHz 무선 랜 시스템에 적용하고 이에 따른 성능을 SER 측면에서 분석하였다. 60 GHz 대역에서 발생하는 위상잡음 환경에서 위상잡음 억제 알고리듬을 적용한 경우, 그렇지 않은 경우에 비해 16-QAM, 64-QAM에서 각각 6 dB, 7.5 dB 정도의 SER 성능 향상을 보였다. We investigate the OFDM-based wireless LAN systems operating in the 60 GHz frequency band as part of the fourth-generation (4G) systems. The 60 GHz band is of much interest since this is the band in which a massive amount of spectral space has been allocated worldwide for dense wireless local communications. This paper gives an overview of 60 GHz band channel characteristics and an effect on phase noise. The performance of OFDM system is severely degraded by the local oscillator phase noise, which causes both common phase error and inter-carrier interference. In this paper, we apply phase noise suppression (PNS) algorithm that is easy for implementation to OFDM based 60 GHz wireless LAN system and analyze the SER performance. In case of using the PNS algorithm, SER performance is improved about 6 dB, 7.5 dB, respectively in 16, 64-QAM.

OFDM Inter-carrier Interference Due to Radio Frequency Synthesizer Phase Noise

Abstract This work presents the effects of radio-frequency Local Oscillator non-idealities on OFDM inter-carrier interference. The synthesizer has the main role on modulation and demodulation process of base band IQ signals to radio frequency channels which need to fulfill several requirements imposed by standards specifications. Phase and frequency stability are crucial, since the synchronization of the entire system depends on the accuracy of this circuit. The discussed OFDM system is based on a simulation scenario including radio-frequency channel conversion considering Local Oscillator with configurable phase noise power and bandwidth. This feature allows the study of global system based on Local Oscillator output spectrum. Sub-channel spacing, cyclic redundancy and pulse shaping are configurable. The obtained results indicate that free run oscillator phase noise characterization is not appropriate when the Local Oscillator in the radio-frequency front end is based on synthesizer architecture. System evaluation is based on error vector magnitude. The relation of this metric with the Local Oscillator phase noise allows the performance estimation of the global system.

Review On Ici Reduction Techniques In Ofdm System

Orthogonal frequency division multiplexing (OFDM) is a promising technique for the broadband wireless communication system. However, the inter-carrier-interference (ICI) produced by the phase noise of transceiver local oscillator is a serious problem. The variations in Time Offset (TO) can lead to inter-symbol- interference (ISI) in case of frequency selective channel. Literature survey of any research filed or subject is must required, before contributing in the research of that field. The literature review gives a detailed study of existing published material for clear understanding of that area. Therefore, this Paper presents a detailed literature survey of the area taken (i.e., OFDM). The study in this paper highlights different problems or issues of OFDM system like high PAPR, synchronization, and Inter-Carrier-Interference (ICI). This review also summarizes the methods available in the literature to overcome these problems.

Pilot-Symbol Assisted and Code-Aided Phase Error Estimation for High-Order QAM Transmission

In this paper, we present a novel phase error estimation scheme for low-density parity-check (LDPC) coded high-order quadrature amplitude modulation (QAM) transmission systems, and we provide a theoretical analysis of its performance. The scheme uses known pilot symbols which are assumed to be placed at equally spaced positions, and phase errors occurred at these pilot symbol positions are first estimated. They are then interpolated over the other positions by using a Wiener filter (WF), and estimation accuracy is next refined by using an LDPC code-aided phase-locked loop (PLL). We present an efficient implementation of this two-stage, Pilot-Symbol-Assisted and Code-Aided (PSA/CA) scheme and evaluate its performance by means of power spectrum analysis. We determine the mean square error at each step of the PSA/CA scheme, and we find an optimal value of the noise equivalent loop bandwidth of the PLL under the assumption that local oscillator phase noise can be modeled as a single-pole single-zero model. We show through simulations that the PSA/CA scheme has a very high phase noise tolerance comparable to that of state-of-the-art phase estimation schemes and provides a computationally efficient alternative.

Design of Local Oscillator Based on DDS of High Performance Short-Wave Receiver

Phase noise and spurious signals of local oscillator will affect the performance of short-wave receiver. The structure of receiver's front-end part based on DDS is introduced to realize a high-performance local oscillator of short-wave receiver. Then measures were taken to improve the LO's performance, including using external directly frequency multiplier as DDS' clock to improve the purity of frequency spectrum, tracking filter to degrade harmonics and gain control circuit to remain constant amplitude in the desired frequency range. At last, test results show that the above-mentioned measures improve the receiver's performance.

EVM Analysis for Broadband OFDM Direct-Conversion Transmitters

Low-cost orthogonal frequency-division multiplexing (OFDM) direct-conversion transceivers suffer from signal degradation through the impairments of the analog front end, e.g., due to in-phase and quadrature (IQ) imbalance, phase noise, and nonlinear power amplifier (PA) effects. This paper analyzes joint performance degradation due to these key transmitter imperfections. Error vector magnitude (EVM) is chosen as the figure of merit, which is motivated by its frequent use in the standards for specifying transmitter requirements. In particular, we derive closed-form EVM expressions for the challenging problem of wideband OFDM transmitter design and validate the analysis through simulations. Based on the study, it is possible to conclude that EVM is governed by the memory effects associated with the PA and the reciprocal of the image rejection ratio (IRR), which is defined by the IQ modulator. We also demonstrated that intercarrier interference (ICI) due to the local oscillator phase noise shows an approximately frequency-flat response.

Consideration on offset LO contribution in the phase noise of offset PLL architecture

ABSTRACTBased on experimental results, the phase noise of offset phase locked loop (PLL) is analyzed theoretically and experimented. Analyses are developed both to calculate the in‐band phase noise of a given synthesizer architecture and to predict the impact from the the phase noise of offset local oscillator (LO). This article verifies that the phase noise of offset LO give a direct impact on the in‐band phase noise of frequency synthesizer. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2699–2701, 2013

Effects of phase-locked loop bandwidth on error vector magnitude in transmitter

The error vector magnitude (EVM) is extensively applied as a measure of transmitters’ performance. In this paper, the effect of phase-locked loop (PLL) bandwidth on EVM is examined. The relationship between EVM and PLL based local oscillator phase noise is analyzed, and a simplified expression is used to evaluate the EVM. Dependence of EVM on loop bandwidth is investigated. Analytical and experimental results show that choosing the optimal loop bandwidth of PLL would minimize the EVM of transmitter.

Proposal of channel-grouping wireless-transceiver architecture for suppressing local-oscillator phase noise

This paper proposes an architecture-level solution to suppress the phase noise of local oscillators in wireless-transceiver LSIs. Because a phase-looked loop (PLL) supplies only one local oscillator (LO) frequency for multiple channels, large loop bandwidth of the PLL can be used for suppressing the phase noise. Simulation results show that a sixteen-channel grouping can suppress the phase noise more than 24dB in narrow-band wireless systems. Channel selection in receive mode can be ensured by a variable intermediate frequency (IF) complex band-pass filter. Local-leak and image signals in transmit mode can be suppressed by a quadrature up-conversion mixer and radio frequency (RF) band-pass filter with high-IF configuration. A digital-analog converter, analog-digital converter, and digital LSI are in charge of modulation and demodulation of the variable-IF signals.

Error-rate Floors in Differential n-level Phase-shift-keying Coherent Receivers employing Electronic Dispersion Equalisation

Abstract A model for the phase noise influence in differential n-level phase shift keying (nPSK) systems and 2n-level quadrature amplitude modulated (2nQAM) systems employing electronic dispersion equalization and quadruple carrier phase extraction is presented. The model includes the dispersion equalization enhanced local oscillator phase noise influence. Numerical results for phase noise error-rate floors are given for dual polarization (DQPSK, D16PSK and D64PSK) system configurations with basic baud-rate of 25 GS/s. The transmission distance in excess of 1000 km requires local oscillator lasers with sub-MHz linewidth.

Optimization and design of a novel prescaler and its application to GPS receivers

In this work, a novel prescaler based upon new current mode logic (CML) flip-flop architecture applied to global positioning system (GPS) receivers is proposed. Compared to traditional static current mode logic (CML) flip-flop, it introduces a clock-controlling transistor to reduce the time constant at sensing period. As a result, the speed has been maximized and the working range has been enlarged. The phase noise of local oscillator (LO) signals coming from the prescaler can be lowered by 6 dB, and the interference of voltage controlled oscillator (VCO) to radio-frequency (RF) front-end apartments (low noise amplifier, mixer, etc.) will be diminished so that the sensitivity of GPS receivers is enhanced. This prescaler’s maximum input frequency rises up to 6.9 GHz, 30% higher than that of traditional architecture, and its power is only 2.16 mW when the supply voltage is 1.8 V. The prescaler was manufactured in 0.18-μm CMOS process, and it has been successfully applied to GPS receivers.

Equalization-enhanced phase noise induced timing jitter

In electronic digital signal processing based optical communication systems, digital equalization for chromatic dispersion interacts with local oscillator phase noise to produce equalization-enhanced phase noise (EEPN). In addition to both phase and intensity noises, EEPN also induces timing jitter to the equalized signal. For a 100 Gbit/s quadrature-phase-shift keying signal with laser linewidth of 300 kHz, the timing jitter is up to 20% of the symbol interval for a transmission distance of 1500 km.

Influence of Pre- and Post-compensation of Chromatic Dispersion on Equalization Enhanced Phase Noise in Coherent Multilevel Systems

In this paper we present a comparative study of the equalization enhanced phase noise (EEPN) for pre- and post-compensation of chromatic dispersion in high capacity and high constellation systems. This is to our knowledge the first detailed study in this area for pre-compensation systems. Our main results show that the local oscillator phase noise determines the EEPN influence in post-compensation implementations whereas the transmitter laser determines the EEPN in pre-compensation implementations. As a result of significance for the implementation of practical longer-range systems it is to be emphasized that the use of chromatic dispersion equalization in the optical domain e.g. by the use of dispersion compensation fibers eliminates the EEPN entirely. Thus, this seems an efficient solution for such systems operating at high constellations in the future.

Spectrum Broadening Due to Phase Noise Interaction in Cognitive Radio Systems

Spectrum broadening due to the interaction of local oscillator (LO) phase noise with an adjacent channel signal is analyzed, and applied to the situation where a cognitive radio (CR) detector experiences in-band interference from a strong adjacent channel signal. Expressions for the resulting in-band interference and modified detection performance are presented.

Impact of phase to amplitude noise conversion in coherent optical systems with digital dispersion compensation

The impact of phase to amplitude noise conversion for QPSK, 16-QAM, and 64-QAM coherent optical systems are investigated with electronically-compensated chromatic dispersion (CD). The electronic equalizer is shown to convert the phase noise from the local oscillator (LO) to amplitude noise, limiting the amount of CD that can ideally be compensated digitally. The simulation results demonstrate that the performance of coherent systems can significantly be degraded with digitally compensated CD and LO phase noise. The maximum tolerable LO linewidth is also investigated for the different modulation formats and found to become increasingly stringent for longer transmission distance and higher symbol rate.

2.4 GHz bio‐radar system with improved performance by using phase‐locked loop

AbstractThis letter presents a novel bio‐radar system with phase‐locked loop (PLL) for noncontact measurement of vital sign. As the leakage of the phase noise of local oscillator (LO) through antenna is dominant factor for the distances larger than about 30 cm, the performance of a bio‐radar system can be improved with the PLL employment. The proposed bio‐radar and PLL are implemented by using conventional commercial components, and the measured result shows that the bio‐radar system performance is greatly improved with a PLL without any additional digital signal processing. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2074–2076, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25366