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Dual-polarization quadrature phase shift keying (DP-QPSK) modulation format is emerging as a main contender for 37.5 GHz frequency grid of WDM systems. However, the optical add drop multiplexers (OADMs) affect the performance of the system because of narrow channel spacing. The local oscillator (LO) is an important component of the digital coherent receiver. This paper analyzes the effects of LO parameter on the performance of the considered system. It is exhibited that optimum range of optical power and laser linewidth of the LO helps in improving the performance of the considered system. [ABSTRACT FROM AUTHOR]

In this paper, we present and compare two different full-band WR3.4 Sub-Harmonic Mixers (SHMs), featuring traditional GaAs and the novel low-barrier InGaAs discrete diodes. In this study, an Active Multiplier Chain (AMC) is used as a Local Oscillator source, which provides peak powers beyond 20 mW. The GaAs mixer presents Single-Sideband (SSB) Conversion Loss (CL) of 10 dB and Double-Sideband (DSB) Noise Temperature (NT) of 3000 K across the entire RF and IF bands when an LO power of 6–10 mW is applied. The low-barrier mixer featuring the new and improved batch of InGaAs diodes performs SSB Conversion Loss of 15 dB and DSB Noise Temperature of 9000 K, using LO powers of 0.5 mW. In this work, a comparison of the CL and NT of both mixers is carried out, highlighting the excellent performances of GaAs diodes and the minimum LO power requirements needed by InGaAs counterparts, as well as future perspectives in InGaAs mixer performances. The mixers and diodes were fully designed, fabricated, and tested at ACST GmbH. [ABSTRACT FROM AUTHOR]

Radio telescopes are among the applications with the highest demands on a local oscillator (LO), which is used to receive and process the signals coming from the sky. Therefore the modules providing the required LO signal have traditionally been big and complicated. To overcome this disadvantage, we implement our own integrated frequency synthesizer inside a small LO module in this article. With this synthesizer we are able to achieve a jitter of only 50 fs integrated from 10 Hz to 2.5 GHz offset at a carrier frequency of 75 GHz. This is in part achieved by a very low in-band phase noise of −111.8 dBc at 10 kHz offset. The stabilizable frequency range is 62–88 GHz. Thus achieving promising results to fulfill this very demanding task with integrated frequency synthesizers in the future. [ABSTRACT FROM AUTHOR]

In this paper, a continuous variable (CV) measurement‐device‐independent (MDI) quantum key distribution (QKD) protocol using Gaussian modulated coherent states is proposed. The MDI is first proposed to resist the attacks on the detection equipment by introducing an untrusted relay. However, the necessity of propagation of local oscillator between legitimate users and the relay makes the implementation of CV‐MDI‐QKD highly impractical. By introducing the plug‐and‐play (P&P) technique into CV‐MDI‐QKD, the problems of polarization drifts caused by environmental disturbance and the security loopholes during the local oscillator transmission are solved naturally. The proposed scheme is superior to the previous CV‐MDI‐QKD protocol on the aspect of implementation. The security bounds of the P&P CV‐MDI‐QKD under the Gaussian collective attack are analyzed. It is believed that the technique presented in this paper can be extended to quantum network. [ABSTRACT FROM AUTHOR]

Inspired by the Stewart platform, the theoretical model of a double-layered Stewart platform with local oscillators is proposed and its performance is studied based on numerical simulations and experimental methods. To validate the performance of the proposed technique we perform a vibration experiment, where the vibration isolation performance is estimated based on the ADAMS software. From the experimental analysis, we study the influence of the model parameters on the vibration isolation performance and highlight the advantages of the proposed double-layered platform over the traditional single-layered ones. The experimental results demonstrate that the oscillators can effectively suppress the transmissibility near the resonant frequency, which benefits the vibration isolation performance of the system. A double-layered Stewart platform with local oscillators is designed and manufactured. The advantages of the proposed platform over the single-layered ones are highlighted. The oscillators can effectively suppress the transmissibility near the resonant frequency. The proposed platform has better low-frequency vibration isolation performance. [ABSTRACT FROM AUTHOR]

An All-Digital Phase-Locked Loop (ADPLL) is an architecture that is widely employed in the communication system due to the advancement of the Complementary Metal-Oxide-Semiconductor (CMOS) technology process. A 2.4GHz Radio Frequency Identification (RFID) system needs a frequency synthesizer in the local oscillator architecture of the transceiver to generate a stable frequency tuning range Therefore, in this paper, a Digital Phase-Frequency Detector (DPFD) is designed to achieve the phase and frequency acquisition in the ADPLL system. The proposed DPFD is divided into two main parts, the first is the Phase Detector (PD) and the second is the Frequency Detector (FD). The PD has managed to detect the presence of the phase difference by recognizing two different input signals. The FD, on the other hand, is capable to detect the higher frequency by identifying the output signals from the PD in digital formation. In addition, a control unit module is developed to control and adjust the Preset Word (PW) for the system by using a binary search scheme. Comparison results show that the final value of the PW from the simulation is the same as from the manual calculation (theoretical values). The digital PFD and the PW control modules are designed and simulated by using Verilog HDL code. These two designed modules will be integrated into the targeted ADPLL to achieve fast locking performance and ultra-low power for Ultra-High Frequency (UHF) RFID applications. [ABSTRACT FROM AUTHOR]

Many varieties of technologies have been introduced for mobile communication and data traffic plays a major role in each generation of communication systems. 5G is termed as Next Generation Wireless Mobile Networks that has higher bandwidth, maximum spectral efficiency, super-speed connection, minimum energy consumption, when compared to 4G wireless networks. Next Generation of Mobile communication will use mmWave frequency bands for 5G systems. Millimeter wave transmission is one of the greatest technology in 5G mobile communication systems having higher bandwidth. It is also considered to be having high user demands and have a mobile growth in coming years. It is a promising technology having a non-shortage bandwidth and traffic demands. The major drawback in this system is Phase noise, In-phase and Quadrature timing mismatch, PAPR, local oscillator noise and blockage effects. The phase noise occurs due to the imperfections in local oscillators. In this paper, we discuss the Phase noise issues in millimeter wave systems. This review will act as guide for researchers to compare the various emerging phase noise problems and mitigation techniques for future 5G wireless networks. [ABSTRACT FROM AUTHOR]

Coherent reception becomes an interesting option when data rates in time-division-multiplexed (TDM) passive optical networks (PONs) grow beyond 50 Gbit/s. Controlling the wavelength, i.e., the optical frequency, and the phase of the laser acting as local oscillator (LO) is one of the main technical challenges in the design of coherent TDM PONs. In the optical network units (ONUs), low-cost lasers are required, which come at the expense of wavelength variations and drifts over multiple nanometers due to fabrication imperfections, and temperature variations. This contradicts the requirement of wavelength-stable LOs in coherent receivers. The use of a wavelength locker circuit and a temperature controller is considered as too complex for applications in access networks. In this work, we propose a novel colorless coherent architecture with high resilience to ONU laser wavelength drifts of up to $\pm$ 4 nm ($\pm$ 0.5 THz) for future 100 Gbit/s PON. It allows the use of distributed feedback lasers at the ONU side. This is rendered possible by generating a frequency comb with carefully chosen free spectral range in a quantum-dash mode-locked laser diode at the optical line terminal. In upstream operation, the frequency comb serves as an LO, whereas the same information is modulated onto all comb lines for the case of downstream. As a result, the ONU laser can drift over the entire comb bandwidth without substantial performance penalty. We experimentally demonstrate downstream and upstream operation with an aggregated raw data rate of 96 Gbit/s, respectively. We further introduce advanced digital signal processing (DSP) methods including a coarse frequency offset compensation (CFOC) and a multiple-input multiple-output (MIMO) equalizer to improve the performance of our concept. We show that the receiver sensitivity can be increased by 3 dB for a high-bandwidth receiver when using a 6 × 2 MIMO equalizer scheme. A 4 × 2 MIMO equalizer scheme enables colorless reception even with a limited-bandwidth receiver. [ABSTRACT FROM AUTHOR]

We present the demonstration of two novel chip-scale FMCW LiDAR optical engines in which all photonic components, including the laser sources, were integrated on single silicon chips. Using the first LiDAR chip design, with an integrated distributed Bragg reflector laser and grating couplers as input/output ports for the receive/transmit light, we demonstrated a maximum range of 28 m limited by transmit light output power of 2 mW. We further demonstrated a maximum range of 75 m using a second LiDAR chip architecture having an on-chip sampled grating distributed Bragg reflector master laser with integrated power amplifier in which the local oscillator light was obtained from the laser back facet. This maximum range can be further increased by improving the laser linewidth. The measured range dependence of the FMCW signal level for both LiDAR chips agreed well with theory. The chip-scale FMCW LiDAR optical engines can be used in conjunction with a variety of off-chip two dimensional beam scanners to realize a chip-scale scanning LiDAR solution. To the best of our knowledge, this is the first published demonstration of fully integrated FMCW LiDAR optical engines on a single silicon chip. [ABSTRACT FROM AUTHOR]

Summary: This study developed a local oscillator (LO) with low phase noise and low power consumption. The proposed oscillator core comprises a pair of cross‐coupled transistors, which are fed by another pair of transistors that injects current at moments close to the peak of output voltage. The position of the current injection transistors, which are inserted in series with the cross‐coupled transistors, affects the waveform of current injected into an inductive–capacitive (LC) tank. Installing a capacitor on the source node of the cross‐coupled transistors increases the current injected into the LC tank and thereby augments the output voltage amplitude and power efficiency of the LO. The resonator phase shift and Q can be corrected by adjusting the source capacitance, which filters noise. These changes reduce the phase noise to −123.4 dBc/Hz at a frequency offset of 1 MHz and improve oscillator performance with a figure of merit equal to −193.5 dBc/Hz. To evaluate the LC tank, a 5 GHz LO was simulated at 1.8 V power supply and 2.5 mW power consumption. The simulation was conducted using a practical 0.18 complementary metal–oxide–semiconductor model manufactured by the Taiwan Semiconductor Manufacturing Company. The simulation results confirmed the analytical findings. [ABSTRACT FROM AUTHOR]

This work aims to present the theoretical framework for the outage performance assessment of the joint impact of antenna misalignment and local oscillator (LO) phase noise (PHN) on terahertz (THz) wireless systems. In more detail, a closed form expression for the outage probability and a tight high signal to noise ratio (SNR) approximation were extracted. Our results reveal the detrimental impact of antenna misalignment and PHN and the importance of taking them into consideration when analyzing the performance of THz wireless systems. Furthermore, it was observed that the impact of the LO hardware impairments is more significant to the system performance compared to the antenna misalignment. [ABSTRACT FROM AUTHOR]

How to remove local oscillator (LO) side channel attacks has been a notoriously hard problem in continuous-variable quantum key distribution (CV-QKD). In the self-referenced CV-QKD schemes, the LO signal is locally generated at the receiver by an independent laser so that it is not co-transmitted with the quantum signal. This simple solution removes all LO side channels. However it also introduces some other practical vulnerabilities. Especially the polarization states of the quantum signal and LO signal may not be identical across the detector because of the presence of the polarization aberrations. Thus, the detection efficiency which is arguably the most critical experiment parameter of the practical implementation will be impaired. In this paper, we analyze the impact of polarization aberrations on the detection efficiency for CV-QKD and propose a self-referenced CV-QKD scheme in the presence of polarization aberrations by using an off-axis optical system. In the proposed scheme, the polarization states of the quantum signal would change with the off-axis optical system, thus impairing the heterodyne efficiency. Our security analysis shows a gap between the theory and practice of CV-QKD. [ABSTRACT FROM AUTHOR]

In this study, we propose an approach for the design and satisfy the requirements of the fabrication of a small, lightweight, reliable, and stable ultra-wideband receiver for millimeter-wave bands and the contents of the approach. In this paper, we designed and fabricated a stable receiver with having low noise figure, flat gain characteristics, and low noise characteristics, suitable for millimeter-wave bands. The method uses the chip-and-wire process for the assembly and operation of a bare MMIC device. In order to compensate for the mismatch between the components used in the receiver, an amplifier, mixer, multiplier, and filter suitable for wideband frequency characteristics were designed and applied to the receiver. To improve the low frequency and narrow bandwidth of existing products, mathematical modeling of the wideband receiver was performed and based on this spurious signals generated from complex local oscillation signals were designed so as not to affect the RF path. In the ultra-wideband receiver, the gain was between 22.2 dB and 28.5 dB at Band A (input frequency, 18-26 GHz) with a flatness of approximately 6.3 dB, while the gain was between 21.9 dB and 26.0 dB at Band B (input frequency, 26-40 GHz) with a flatness of approximately 4.1 dB. The measured value of the noise figure at Band A was 7.92 dB and the maximum value of noise figure, measured at Band B was 8.58 dB. The leakage signal of the local oscillator (LO) wa-97.3 dBm and -90 dBm at the 33 GHz and 44 GHz path, respectively. Measurement was made at the 15 GHz IF output of band A (LO, 33 GHz) and the suppression characteristic obtained through the measurement was approximately 30 dBc. [ABSTRACT FROM AUTHOR]

High bandwidth, low cost and small size has made Inter satellite optical wireless communication a promising and advance technology with an alternative to current microwave satellite systems. In this paper, advantages of coherent-detection quadrature phase shift keying (CO-QPSK) with DSP are investigated for the mitigation of non-linear effects. The technique of carrier phase estimation has been used to prolong the transmission range to several thousand kilometers. Further, 400 Gbps WDM-QPSK system has been analyzed for different distances with 30 dB transmitting power and 11 dB LO power. At last, system has been investigated at narrow channel spacing of 50 GHz and a brief comparison has been made with system having channel spacing of 100 GHz. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A method for the frequency determination of a local oscillator (LO) is presented to facilitate reception of the maximum number of satellite signals via the use of a multi‐global navigation satellite system (GNSS) receiver under interference. The authors have herein suggested a model for estimating the number of GNSS satellites with changing LO frequency. This estimation model was derived based on GNSS and interference spectra, used to determine the LO‐frequency value to avoid interference and facilitate reception of maximum GNSS signals. The proposed method was verified by means of an experiment involving the use of software‐defined radio receiver and actual GNSS signals. The authors expect the proposed method to be the basis of anti‐interference processes in reconfigurable GNSS receivers. [ABSTRACT FROM AUTHOR]

The assumption that observed signals are ideally received is commonly used in the literature on time-delay estimation. However, for practical digital receivers, the received radio-frequency signals are usually downconverted to the baseband and digitized by analog-to-digital converters. Because inaccurate and unstable system clocks are used, frequency and phase offsets are usually induced by the frequency-mixing procedure, whereas a time stretch may ensue from the sampling procedure. The aforementioned problems are almost inevitable for incoherent reception systems. Therefore, the neglect of imperfect reception for incoherent systems may reduce the performance of conventional time-delay estimation methods. In this paper, employing refined signal models developed specifically for incoherent time-delay estimation in active and passive systems, the corresponding joint maximum likelihood estimates of time delay and system-clock frequency error are proposed. The Cramér-Rao lower bounds (CRLBs) on time-delay and clock frequency error estimations are also derived. The performance of the proposed time-delay estimators can be improved for frequency/phase offsets and time stretches, approaching the performance of the CRLBs in scenarios of moderate and high signal-to-noise ratios. Furthermore, both CRLBs analysis and simulation results verify that the accuracy of the proposed time-delay estimator is unaffected by the performance of the system clock in moderate scenarios. [ABSTRACT FROM AUTHOR]

In this brief, a novel methodology for estimating the initial diode bias voltage in multiport receivers was developed. We tested the methodology for four different Schottky diodes from different vendors (Win Corp, HP, Hitachi, and Siemens), but the process can be applied to any diode. The analysis shows that setting the initial value for the optimizer where the diode's output dc voltage to input power sensitivity is highest yields the fastest convergence time for the error vector magnitude (EVM) optimizer algorithm. This point is located at the inflection point of the first derivative of the I-V curve fitting polynomial which was obtained in MATLAB and assures that the optimizer will not be trapped into local minima. To verify the results of this research, we used a Simulink model that emulates the radio frequency and digital base band parts of a six-port receiver. It was found that, by reducing the voltage difference between the estimated initial value and the optimum point, the optimizer needed less steps to reach the optimum value of the bias voltage. This work also provides the behavior of the variation of the initial estimates of the diode voltage with the polynomial degree. Hence, the necessary degree for the fitting polynomial can be determined based on the initial point variation analysis. [ABSTRACT FROM PUBLISHER]

A Nyquist folding receiver (NYFR) is a novel ultra‐wideband (UWB) receiver architecture, which can realise a wideband receiving with fewer components. Intercepted by the NYFR with a sinusoidal frequency modulation (SFM) local oscillator, a linear frequency modulation (LFM) signal will be converted into a LFM/SFM hybrid modulated signal. To simplify the processing of this kind of complicated signal, the authors propose improved dual‐channel NYFR architecture with an efficient parameter estimation algorithm. Compared with the existing parameter estimation methods for the NYFR, the proposed architecture offers better estimation performance, higher signal type adaptability, and simpler operation. [ABSTRACT FROM AUTHOR]

An ultra‐low‐LO (local oscillator)‐power X‐band down‐conversion ring mixer in 0.18‐μm CMOS process is presented. By using the weak‐inversion biasing technique, the proposed X‐band ring mixer exhibits low‐dc‐power consumption and low‐LO‐drive power while maintaining a reasonable conversion gain (CG). The measurement results show that the proposed mixer demonstrates a maximum CG of 1.75 dB with ultra‐low‐LO‐power of −8 dBm at RF of 12 GHz and IF of 100 MHz. The dc power is only 2 mW. The 3‐dB RF bandwidth is from 9 to 15 GHz and the output 1‐dB compression point (OP1 dB) is −14 dBm. [ABSTRACT FROM AUTHOR]

A radio frequency (RF) low voltage and low power down conversion mixer with high linearity using TSMC 0.18-μm technology is presented which operates in 2.4 GHz Industrial Scientific and Medical (ISM) band. The local oscillator (LO) frequency is 2.1 GHz with an input power of 5 dBm, whereas IF frequency is 300 MHz. Multiple gated transistors (MGTRs) method is used to increase the linearity of Gilbert cell mixer. In this method an auxiliary transistor is used parallel to the transconductance stage transistor. This increases linearity by decreasing of transconductance stage transistor. The simulation results show an IIP3 improvement of 16.55 dBm. The proposed low power and highly linear mixer consumes a power of 4.46 mW from 1.8 V a supply voltage. The noise figure (NF) and gain conversion are about 13.8 dB and 9.11 dB, respectively. [ABSTRACT FROM AUTHOR]

This paper introduces a 2nd harmonic extraction technique and its implementation in a 46.4–58.1 GHz frequency synthesizer. The frequency doubling approach is based on tapping second harmonic signals at the VCO supply and tail nodes and amplifying them to provide a differential output. Since the amplifiers do not load the VCO outputs, the proposed technique does not affect either the tuning range or the frequency of the VCO. Moreover, a novel noise bypass technique is utilized to ensure that the amplifiers do not degrade the VCO phase noise. As a result, the frequency synthesizer achieves 22.4% tuning range (46.4–58.1 GHz) and phase noise below –118 dBc/Hz while consuming 66 mW from a 1 V supply. The stacked common gate amplifier can also be utilized for voltage regulation, providing a relatively constant FOM performance over a 2X power dissipation range. The synthesizer occupies 0.6 mm \times 1 mm in IBM 32 nm SOI CMOS. [ABSTRACT FROM AUTHOR]

In this brief, we developed a detailed Simulink model that emulates the radio frequency and digital base band of a six-port receiver. In contrast to other results published in the literature, we not only provide a controlled continuous bias to the diodes. We propose a novel algorithm that reduces the error vector magnitude (EVM) by adaptively controlling the diode bias point. We will also show that when the algorithm is turned on in the model, the EVM becomes less sensitive to variations in the diode bias conditions. Another key feature of optimum diode bias control is that the local oscillator (LO) power requirements decrease and that the EVM is not sensitive to LO power variation. Results presented here show that for an LO power variation of more than 10 dB, we notice no EVM variation. [ABSTRACT FROM PUBLISHER]

The analysis and implementation of a dual-band direct-conversion millimeter-wave transmitter is presented. The proposed dual-band modulator uses high-impedance loads at two frequencies for the local oscillator driving amplifiers and power amplifier (PA) pre-amplifiers. To correct the amplitude and phase imbalance of the in-phase and quadrature channels at Q- and W-bands, the paper suggests a digitally controlled quadrature error correction stage to finely calibrate these errors and lower the error vector magnitude (EVM) without increasing the baseband digital-to-analog converter resolution. The transmitter is fabricated in 0.12- μm silicon-germanium BiCMOS process and occupies an area of 5.5 mm2. At 45-GHz carrier frequency, error correction improves the sideband suppression ratio (SSR) by 10 dB at 2.4-MHz IF frequency. The EVM is lowered from 3.21% to 2.38% for a 64-QAM constellation at a 2.4-Ms/s symbol rate. At 94-GHz carrier frequency, the SSR is improved from 24 to 41 dBc at 2.4-MHz IF frequency, and the EVM is lowered by more than 1% for a 16-QAM constellation at 3-Ms/s symbol rate. A dual-band PA breakout measurement indicates the peak power-added efficiency of 15% with 14-dBm maximum saturated power (Psat) at 43 GHz and 9-dBm Psat at 82 GHz is achieved. [ABSTRACT FROM AUTHOR]

Dynamics of a third-order optical phase locked loop (OPLL) with a resonant type loop filter (LF) has been studied analytically and numerically. The range of stable synchronous operating zone of such OPLL has been estimated analytically in system and signal parameters and obtained predictions are in good agreement with numerical results. Beyond the stable region, it is found that chaotic oscillation of phase error occurs through a sequence of period doubling bifurcation. In addition to this, tracking of such periodic as well as chaotic dynamics of third-order OPLL by another OPLL in master-slave configuration has also been explored here. The tracking is possible by slave OPLL within a very short range of effective frequency offset by keeping other design parameters within the stable mode of operation. The synchronization of the master and slave OPLLs has been studied in generalized sense by considering auxiliary system. The study is very important and helpful for optical signal processing and also in chaos-based secure communication. [ABSTRACT FROM AUTHOR]

Optoelectronic down-conversion of a terahertz optical beatnote to a RF intermediate frequency is performed with a standard Mach-Zehnder modulator followed by a zero dispersion-slope highly nonlinear fiber. The two interleaved optical combs obtained by four-wave mixing are shown to contain more than 75 harmonics enabling to conveniently recover the phase noise of a beatnote at 770 GHz at ~500 MHz. This simple four-wave mixing assisted down-conversion architecture is implemented to a two-frequency solid-state laser in order to directly phase-lock its frequency difference. This is illustrated on a beatnote at 168 GHz directly phase locked to the local oscillator at 10 MHz. [ABSTRACT FROM PUBLISHER]

In this paper, a wide locking range, quadrature output ring type injection locked frequency divider (ILFD) is presented for division ratios of 3 and 4. This ILFD proposes a novel injection scheme that shapes the injection signal to a proper form and provides a convenient situation for divider locking. Furthermore, two new wide locking range, low power consumption, injection locked ring oscillators (ILROs) are proposed for quadrature generation in local oscillator architectures. A novel cognitive radio quadrature local oscillator (LO) architecture is presented by utilizing the proposed ILFDs and ILROs to verify the effectiveness of the proposed circuits. Moreover, a new technique is implemented on the LO architecture to widen the frequency range without consuming any extra power. Because of using a single LC tank, this architecture is very compact. Also, it has the benefit of low power consumption and low output phase noise. [ABSTRACT FROM AUTHOR]

We demonstrate analytically a novel scheme to obtain polarization-independent operation in low-cost coherent OOK receivers, suitable for access networks. We move from a well-known phase-diversity receiver, exploiting a 3 × 3 coupler, three photodiodes, and basic analogue processing. If that receiver is modified to inject the local oscillator (or the signal) into two inputs with proper polarization states, we show, by both mathematical derivation and numerical simulations, that the resulting electrical signal can be polarization-independent; this is attained only if the frequency-detuning between the signal carrier and the local oscillator is high enough, so that intrinsic second order distortions can be spectrally isolated and suppressed by the low-pass filtering of the receiver. [ABSTRACT FROM PUBLISHER]

This letter demonstrates decision-directed Costas loop stable homodyne detection for 10-Gb/s binary phase shift keying signal fiber-transmission of over 100 km utilizing frequency-stabilized several kilohertz spectral linewidth external cavity laser diodes (E-LDs). We design a phase-locked loop circuit that adopts an injection-current controlled E-LD as its local oscillator; its low phase error allows it to achieve the standard deviation of 1.9°. Owing to this phase-lock performance and the highly coherent light source, the receiver sensitivity approaches within 6 dB of the shot noise limit and the phase-locked loop recovers the optical carrier stably even if the waveform is distorted by the chromatic dispersion of 880 ps/nm after fiber transmission. [ABSTRACT FROM PUBLISHER]

We demonstrate an ultra dense WDM passive optical network based on a simplified low-cost coherent receiver and free-running DFB lasers. The proposed 1.25 Gb/s system provides a high power budget , which can be exploited to support both large splitting ratio (1 × 128) and long reach (exceeding 60 km). The homodyne receiver is significantly simplified since it does not make use of any DSP and does not require phase/frequency locking; therefore, it allows for the use of a common free-running DFB as local oscillator rather than expensive low phase noise laser. Here, the proposed system is evaluated experimentally by using 5 × 1.25 Gb/s (gross data rate) channels on a 6.25 GHz grid. In the coherent receiver, a single free-running DFB laser was able to select each individual channel by thermal tuning and showed uniform performance. A -48 dBm average sensitivity at FEC level over a 66 km reach leaves enough margin for additional 30 dB splitting losses in the optical distribution network. [ABSTRACT FROM PUBLISHER]

This work develops a broadband quadrature voltage-controlled oscillator (QVCO) for digital video broadcasting (DVB) tuner applications. The QVCO is mainly based on a balanced voltage-controlled oscillator (VCO), which is a combination of two single-ended VCO. Two active ports and two resonant tanks balance the phase of outputs and also increase the operating range. Experimental results show that the proposed broadband QVCO achieves a 1.1 ~ 2.4 GHz wide tuning range with a 74 % fractional bandwidth. The phase noise and quadrature-phase error are respectively lower than -109 dBc/Hz at 100 kHz offset frequency and 5 degrees over the 1.3 GHz operating bandwidth. [ABSTRACT FROM AUTHOR]

In this report, we demonstrate how to obtain Raman spectra from single-beam CARS measurements under the condition of strong overlapping two-photon excited fluorescence (2PEF). Our approach is based on the use of a narrowband phase gate implemented via femtosecond laser pulse shaping from a single broadband laser source, without any use of polarization or amplitude modulation. The decisive quantity regarding the creation of 2PEF with shaped laser pulses is the second harmonic power spectrum, which shows a different dependence on the excitation phase from the CARS signal generation. By shifting the phase or the position of the gate in an appropriate way, it is possible to keep the second harmonic power spectrum and 2PEF constant, paving the way for an elimination of it. This allows to reconstruct the Raman signal and to retrieve quantitative information of resonances even when the fluorescence is about 160 times larger than the CARS signal. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The limited availability of analog-to-digital converters with high enough speed and dynamic range makes conventional heterodyne receivers still a reasonable solution for millimeter wave work when a wide frequency tuning range is desired. These basically well-known arrangements from the microwave bands may show surprising phenomena if the features of individual millimeter building blocks are not carefully analyzed. LNA gain below the frequency range of interest can be 10-20 dB more than expected which could severely impair the system noise performance after downconversion. Local oscillator tuning sensitivity above 1000 MHz/V, partly based on almost mandatory multiplication, together with very large tuning speed easily cause stability problems. Particularly active multipliers have often less than 20 dB rejection of fundamental frequency and unwanted harmonics output, which together with mixer LO/IF feed through can completely desensitize the front-end. An improperly matched mixer IF port may confuse even an experienced designer by phantom responses. Finally, modern logarithmic detectors chips can unexpectedly waste more than 10 dB of receiver sensitivity. [ABSTRACT FROM AUTHOR]

Frequency fluctuations caused by mechanical vibrations, power supply noise, and other mechanisms are detrimental to the phase estimator performance in high speed intradyne coherent optical receivers. In this letter, we propose the use of a low-latency parallel digital phase lock loop in combination with common feed-forward carrier phase recovery algorithms in order to compensate both the phase noise and laser frequency fluctuation effects on 16-quadrature amplitude modulation receivers. Numerical results demonstrate the excellent behavior of the proposed two-stage carrier recovery scheme. [ABSTRACT FROM PUBLISHER]

We report the first experimental demonstration of dispersion-enhanced phase noise (DEPN) in reduced-guard-interval (RGI) coherent optical orthogonal frequency-division multiplexing (CO-OFDM) systems. It is first shown that channel estimation enhances DEPN. Then we experimentally demonstrate that for 28 Gbaud dual-polarization QPSK (112 Gb/s) RGI CO-OFDM systems with different inverse fast Fourier transform sizes, the transmission distance at a bit error rate = 3.8×10-3 is limited to 1830-2550 km by DEPN when a distributed feedback laser with a 2.6-MHz linewidth is employed as the local oscillator. We also, however, show that using DEPN compensation can increase the distance to 3320-4400 km. [ABSTRACT FROM PUBLISHER]

A full-duplex radio over fiber link scheme with 16 quadrature amplitude modulation (16-QAM) 10 Gb/s downstream and 2.5 Gb/s upstream signals is proposed. In the downlink, the 60 GHz dual-tone optical millimeter-(mm-) wave signal carrier is generated by the 15 GHz local oscillator via a Mach-Zehnder modulator with frequency quadrupling. The 16-QAM 5 GHz IF signal is up-converted to 65 GHz by modulating it on one of the two tones with single-sideband (SSB) modulation at the central station. At the remote base station, the 65 GHz SSB optical mm-wave signal is detected by a high-speed photodiode. After the 60 GHz uplink dual-tone optical mm-wave carrier is abstracted by optimized filtering, the uplink 63 GHz mm-wave signal is modulated onto it to down-convert to the 3 GHz SSB optical IF signal. Since both the down- and uplink optical mm-wave signals have SSB spectra with the signal modulated on one of the two tones, they suffer little from the fiber dispersion. The simulation results show that the bidirectional signals have good performance even after being transmitted over 30 km standard single mode fiber. [ABSTRACT FROM PUBLISHER]

A unified receiver front-end (RFE) for mobile TV covering the VHF-III, UHF and L bands is described. Performance, power and area efficiencies are advanced in threefold: 1) a gain-boosting current-balancing balun-LNA exhibits high linearity, wideband output balancing and adequate S 11 against gain control; 2) a current-reuse mixer-low-pass-filter merges quadrature-/harmonic-rejection mixing and third-order current-mode post-filtering in one block, enhancing linearity and noise just where both are demanding, while saving power and area for its simplicity; 3) a direct injection-locked 4-/8-phase LO generator relaxes the master LO frequency by avoiding frequency division. Fabricated in 65-nm CMOS the RFE measures 4-dB noise figure, 17-to-35-dB gain range, and +32/-3.4-dBm IIP2/IIP3 with no tuning. The power consumption ranges from 43 (170 MHz) to 55 mW (1.7 GHz) at 1.2-/2.5-V supplies. The die size is 0.46 mm^2. [ABSTRACT FROM PUBLISHER]

This paper mainly focuses on the InGaP/GaAs hetero-junction bipolar transistor (HBT) which is fully based on integrated X-band monolithic microwave integrated circuit (MMIC) differential voltage controlled oscillator (VCO). This VCO is designed and fabricated with HBT tripler circuit techniques for triple multiplication of frequency component of core VCO output. The HBT-based differential VCO circuitry consists of a differential VCO and two triplers. The VCO design is concentrated in high oscillation frequency with the low phase noise by using the tripler circuit. The tripler is the smallest in size, with the lowest power consumption and X-band application frequency. The lowest frequency characteristic enables MMIC tripler differential VCO to be implemented in phase locked loop (PLL) circuit. This approach solves the problem of stable local oscillator (LO) signal. The differential VCO is based on the capacitive cross-coupled differential topology. The core differential VCO achieves the oscillation frequency of 3.583 GHz with the output power of 3.65 dBm, the phase noise of -96.7 dBc at 100 kHz offset and -118.85 dBc at 1 MHz offset at 2.9 V and 30 mA bias condition. At 5 dBm input power, the tripler's conversion loss is less than 30 dB with bias condition as 3 V and 26 mA. The tripler diferential VCO generates the oscillation frequency of 10.75 GHz with the output power of -25 dBm. The total size of fabricated MMIC tripler differential VCO is 995 × 850 μm2 area. [ABSTRACT FROM AUTHOR]

We report on the design, fabrication, and characterization of an 840-900-GHz frequency multiplier chain that delivers more than 1 mW across the band at room temperature with a record peak power of 1.4 mW at 875 GHz. When cooled to 120 K, the chain delivers up to 2 mW at 882 GHz. The chain consists of a power amplifier module that drives two cascaded frequency triplers. This unprecedented output power from an electronic source is achieved by utilizing in-phase power-combining techniques. The first stage tripler uses four power-combined chips while the last stage tripler utilizes two power-combined chips. The source output was analyzed with a Fourrer transform spectrometer to verify signal purity. [ABSTRACT FROM AUTHOR]

A digital predistortion (DPD) architecture is proposed to mitigate the phase noise of the local oscillator (LO). In this architecture, a novel dual‐feedback structure is designed to simultaneously capture the input and output signals of the power amplifier (PA) to perform the PA modelling and DPD linearisation, and thus relax the requirement on the LO phase noise. Experimental results validate the superior performances of the proposed linearisation architecture over the conventional DPD with LO phase noise. It is verified that the proposed DPD can achieve satisfactory performances even with low‐quality LOs of high phase noise levels. [ABSTRACT FROM AUTHOR]

In this paper, a new enhanced noise analysis for active mixers in nanoscale technologies, based on the variations of the two parameters W/L (transistor size) and fLO (local oscillator frequency) is presented. In this study, two important sections of an active mixer, the switching pair and the transconductor are considered. It is shown that the noise generated by the switching pair and the transconductor is reduced with the technology scaling from 90 nm to 45 nm. Also, it is shown that the variations of the noise generated by the switching pair due to W/L variations in a wide range of local oscillator frequency and in different technology nodes is less than the variations of the noise generated by the transconductor, which shows the importance of the transconductor in the generation of the total mixer output noise. For extracting the noise relations, the contribution of the gate resistance noise to the gate and drain total current noises is considered, whereas this noise is usually assumed to be an independent source in the literature. [ABSTRACT FROM AUTHOR]

A filtering technique to attenuate the receive-band noise enables a 65-nm CMOS WCDMA transmitter to achieve an output noise level of - 160 dBc/Hz at 80-MHz offset, while dissipating 65 mW. Using a feedback filtering technique, the circuit introduces a null with an arbitrary width at the receive frequency and eliminates the need for an external SAW filter. A stability analysis is performed to choose the most suitable architecture for the feedback path, which ensures stability over a wide range of loop-gain. Nonideal effects such as quadrature phase and gain errors, LO feedthrough, harmonic downconversion and phase-noise are also analyzed. [ABSTRACT FROM AUTHOR]

We demonstrate the first millimeter-wave Gb/s transmission of broadband wireless signals using uncooled directly modulated lasers to give a low-cost solution. Data signals to and from the base station are distributed at intermediate frequencies for reduced chromatic dispersion together with a remote 40-GHz local oscillator signal for frequency upconversion/downconversion. Coarse-wavelength-division-multiplexing components are employed throughout the network allowing uncooled lasers and low cost filters to be used. Error-free transmission (BER < 10-9) has been achieved for the downlink and the uplink. The paper also provides detailed system link analysis together with simulation results. [ABSTRACT FROM PUBLISHER]

Broadband access networks evolution towards 10-Gb/s user connectivity will foster the evolution of the photonic and wireless technologies needed to implement multi-Gb/s wireless links. In particular, provision of data rates in excess of 1 Gb/s using wireless technologies is limited by currently available electrical technologies due to the required bandwidths and frequencies of operation in the millimeter-wave (mm-wave) band. Microwave photonic techniques and technologies have shown a clear potential to overcome these limitations. In this paper, the detailed study of a photonic vector modulator (PVM) architecture and its performance limitations are presented. The PVM architecture is based on direct baseband modulation and dispersion induced quadrature condition. The limitation of this architecture is the presence of a local oscillator (LO) component in the generated mm-wave spectrum which limits the system dynamic range. To overcome this limitation, a third continuous-wave (CW) laser is used to remove the unwanted LO component by properly adjusting its wavelength and emitted power. After presenting the theoretical model, the LO suppression feature is demonstrated experimentally by generating a 1.25-Gb/s QPSK 41-GHz modulated carrier. The two options (with and without LO carrier) are compared in terms of relevant performance parameters. [ABSTRACT FROM PUBLISHER]

The present work addresses the design of a 65 nm CMOS wide-band single-sideband mixer for UWB synthesiser. The circuit has been designed inductorless and with few capacitors, in order to save silicon area and, at the same time, to get a mixer independent of the adopted frequency plan and synthesiser architecture. Particular attention has been paid to reducing the spurs as much as possible. In order to address a realistic investigation, the design has accounted also for the corner cases and the possible impairments in the input signals. A comparison with the state-of-the-art of the SSB mixers shows the low power consumption of the present work. [ABSTRACT FROM AUTHOR]

The effect of field and medium asymmetry on improvement of signal-to-noise ratio (SNR) in respect of homodyne detection technique is analysed theoretically. The analysis is applied to the sample of bulk GaAs irradiated by off-resonant nanosecond pulsed laser. The dependence of SNR on electric field amplitude and local oscillator (LO) phase is examined. It is found that SNR is maximum for the combination of asymmetric field and asymmetric medium. [ABSTRACT FROM AUTHOR]