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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]

Injection-locked frequency divider (ILFD) is an essential component of a phase-locked loop (PLL) used in a communication transceiver. Due to the rapid growth of virtual reality and artificial intelligence technologies, high-speed communication has become a crucial factor. As a result, highly efficient ILFDs must be engineered to ensure accurate high-speed communication. An optimized ILFD is anticipated to have a large locking range, a low power consumption, a low phase noise, and a low injection power for better functioning of a high speed PLL. However, there are inevitable trade-offs of frequency, phase noise, division ratio, and power consumption, making it more challenging to design an ILFD with a high division ratio at higher frequencies. Choosing an appropriate topology for different operational frequencies is also a challenging task for RFIC designers. This study exemplified different design architectures available for CMOS ILFDs in different super high frequency (SHF) and extremely high frequency (EHF) frequency ranges. The performance parameters of these architectures are analyzed, and a detailed discussion on the device’s performance is presented. This review will serve as a comparative study and reference for the RFIC designer’s future ILFD designs.

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]

Injection-locked frequency divider (ILFD) is an essential component of a phase-locked loop (PLL) used in a communication transceiver. Due to the rapid growth of virtual reality and artificial intelligence technologies, high-speed communication has become a crucial factor. As a result, highly efficient ILFDs must be engineered to ensure accurate high-speed communication. An optimized ILFD is anticipated to have a large locking range, a low power consumption, a low phase noise, and a low injection power for better functioning of a high speed PLL. However, there are inevitable trade-offs of frequency, phase noise, division ratio, and power consumption, making it more challenging to design an ILFD with a high division ratio at higher frequencies. Choosing an appropriate topology for different operational frequencies is also a challenging task for RFIC designers. This study exemplified different design architectures available for CMOS ILFDs in different super high frequency (SHF) and extremely high frequency (EHF) frequency ranges. The performance parameters of these architectures are analyzed, and a detailed discussion on the device's performance is presented. This review will serve as a comparative study and reference for the RFIC designer's future ILFD designs. [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]

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.

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]

Purpose: High resolution investigation of spectral lines of space sources requires low intrinsic noise of the radio telescope receiving system. It is provided with both input cryogenic amplifiers and low phase noise of local oscillators. To make spectral studies, it is neces ary to be able to tune the frequencies of local oscillators with a small frequency step. The paper presents the results of developing the frequency synthesizers, which simultaneously provide both a very high frequency resolution and low level of phase noise. The results of measurements of natural noise of the RT-32 radio telescope radio receiving systems are given also. Design/methodology/approach: The RT-32 receiving systems are constructed as heterodyne receivers with two stages of frequency conversion. Tuning of receiving systems with a frequency step of 10 or 20 MHz is provided by local oscillators of the first frequency conversion stage, and precise tuning is provided due to the ultra-high resolution 0.0001 MHz) of DDS-based (direct digital synthesizer) local oscillators of the second frequency conversion stage. Findings: It is shown that the application of direct digital synthesizers is possible only with the low values of frequency multiplication factors, as well as under the conditions of careful filtering of all reference signals. The parameters of the local oscillators were measured with the N9951A spectrum analyzer (Keysight Technologies) with the high resolution and wide dynamic range. To measure the radio telescope receiving system noise characteristics, a special matched loads with the possibility of cooling down to the liquid nitrogen temperature were made. The noise temperature measurements were made in different cross sections of the RT-32 receiving system. Comparison of such measurements in different configurations makes it possible to provide a preliminary estimation of the RT-32 self noise in the C- and K-bands. Conclusions: The results of measurements of self noise of radio receiving systems and phase noise of local oscillators of the RT-32 radio telescope show that within the C-band the radio telescope is capable to perform high-sensitive studies in both a wide frequency band and a narrow frequency band with the high spectral resolution. Within the K-band, the natural noise is comparable (≈60÷80 K) with the external noise that also allows studying the radiation of maser radio sources.

Purpose: A description of the original technical solutions of the solid-state highly stable local oscillators of the millimeter range and the results of the study of the main characteristics of the developed devices are given. The goal of the work is the development of small-sized stabilized generators with low power consumption for the use in the composition of superheterodyne receivers of the 2 mm and 3 mm ranges for aeronomic research. Design/methodology/approach: The created local oscillators are based on multiple multiplication of the reference signal with a phase locked loop. The output generator on the Gunn diode works without a varactor, with the frequency tuning by changing the voltage on the diode. To measure the spectral characteristics, a test signal of a separate highly stable heterodyne of an astronomical receiver was used. The spectrum of the investigated local oscillator was recorded by a parallel Fourier spectrum analyzer with the frequency resolution of 1 kHz per channel. Methods for the study of other basic characteristics were standard methods of radio measurements. Findings: Compact sources of the heterodyne signal of the mm-wavelength range with low power consumption (less than 20 W) were designed and tested. The output power of the local oscillators is at least 50 mW. The measured relative frequency instability is better than 10-8 when working with a thermostatted quartz reference source. The time resource of continuous work exceeds 2 years. Conclusions: Relative instability of frequency (10-8 ) and launch power (more than 50 mW) of the presented generators correspond to the characteristics of industrial mm-wavelength precision generators, the here developed generators (devices) being more economical, compact and cheaper. A number of proposed circuit and design solutions can be used by designers of similar equipment in the mm-wavelength range.

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]

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) was −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.

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]

We numerically investigate spin-controlled vertical-cavity surface-emitting lasers (spin-VCSELs) for local oscillators, which are based on an injection locking technique used in coherent optical communications. Under the spin polarization modulation of an injection-locked spin-VCSEL, frequency-shifted and phase-correlated optical sidebands are generated with an orthogonal polarization against the injection light, and one of the sidebands is resonantly enhanced due to the linear birefringence in the spin-VCSEL. We determine that the peak strength and peak frequency in the spin polarization modulation sensitivity of the injection-locked spin-VCSEL depend on detuning frequency and injection ratio conditions. As a proof of concept, 25-Gbaud and 16-ary quadrature amplitude modulation optical data signals and a pilot tone are generated, and the pilot tone is used for the injection locking of a spin-VCSEL. An orthogonally-polarized modulation sideband generated from the injection-locked spin-VCSEL is used as a frequency-shifted local oscillator (LO). We verify that the frequency-shifted LO can be used for the homodyne detection of optical data signals with no degradation. Our findings suggest a novel application of spin-VCSELs for coherent optical communications.