GHz Carrier Research Articles

A low-power quadrature voltage-controlled oscillators with LC emitter degeneration phase shift technique

This paper introduces a novel phase-shifting technique for quadrature voltage-controlled oscillators (QVCOs) utilizing an LC emitter degeneration architecture. The proposed technique enables a phase shift of up to ±90°in the transconductance of the coupling path while also generating a negative input resistance. This innovative approach avoids phase ambiguity, mitigates the trade-off between phase noise and phase error, and substantially reduces QVCO power consumption. Moreover, compared to conventional capacitance emitter degeneration methods, the LC emitter degeneration structure has a lower equivalent input capacitance, expanding the QVCO’s frequency tuning range. The designed QVCO is implemented using a 180 nm SiGe BiCMOS technology, occupying a compact area of 0.037 mm2. Post-layout simulation evaluations under various process, voltage, and temperature (PVT) conditions validate the robustness and reliability of the design. Results indicate a phase noise of 102.7 dBc/Hz at a 1 MHz offset from a 22.1 GHz carrier, a frequency tuning range of 25.2%, a phase error of 0.9°, and a power consumption of 12 mW from a 1.1 V supply, achieving a figure of merit (FoM) of 178.8 dBc/Hz.

5G Network Deployment Planning Using Metaheuristic Approaches

The present research focuses on optimizing 5G base station deployment and visualization, addressing the escalating demands for high data rates and low latency. The study compares the effectiveness of Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Simulated Annealing (SA), and Grey Wolf Optimizer (GWO) in both Urban Macro (UMa) and Remote Macro (RMa) deployment scenarios that overcome the limitations of the current method of 5G deployment, which involves adopting Non-Standalone (NSA) architecture. Emphasizing population density, the optimization process eliminates redundant base stations for enhanced efficiency. Results indicate that PSO and GA strike the optimal balance between coverage and capacity, offering valuable insights for efficient network planning. The study includes a comparison of 28 GHz and 3.6 GHz carrier frequencies for UMa, highlighting their respective efficiencies. Additionally, the research proposes a 2.6 GHz carrier frequency for Remote Macro Antenna (RMa) deployment, enhancing 5G Multi-Tier Radio Access Network (RAN) planning and providing practical solutions for achieving infrastructure reduction and improved network performance in a specific geographical context.

Unveiling out-of-loop attosecond timing jitter precision in Ti:sapphire mode-locked lasers with an optical heterodyne technique.

The out-of-loop timing jitter exhibited in free-running Ti:sapphire mode-locked lasers with attosecond resolution is demonstrated using an optical heterodyne technique. To assess the feasibility of the experiment and discrimination signal properties, numerical simulations were conducted for Ti:sapphire mode-locked lasers. For accurately characterizing the genuine phase noise exhibited by Ti:sapphire mode-locked lasers, out-of-loop measurements were conducted, and a straightforward yet improved optical heterodyne setup was employed, allowing simultaneous low-bandwidth locking and out-of-loop timing jitter measurements with two Ti:sapphire mode-locked lasers. The out-of-loop phase noise floor for a single mode-locked laser reaches -203.47 d B c/H z, assuming a 10 GHz carrier frequency. Additionally, the out-of-loop integrated timing jitter is 11.9 a s from 10 kHz to the Nyquist frequency (50 M H z).

Application of quantum-limited optical time transfer to space-based optical clock comparisons and coherent networks

With the demonstration of quantum-limited optical time transfer capable of tolerating the losses associated with long ground-to-space links, two future applications of free-space time transfer have emerged: intercontinental clock comparisons for time dissemination and coherence transfer for future distributed sensing in the mm-wave region. In this paper, we estimated the projected performance of these two applications using quantum-limited optical time transfer and assuming existing low-size, low-weight, and low-power hardware. In both cases, we limit the discussion to the simplest case of a single geosynchronous satellite linked to either one or two ground stations. One important consideration for such future space-based operations is the choice of reference oscillator onboard the satellite. We find that with a modestly performing optical reference oscillator and low-power fiber-based frequency combs, quantum-limited time transfer could support intercontinental clock comparisons through a common-view node in geostationary orbit with a modified Allan deviation at the 10−16 level at 10-s averaging time, limited primarily by residual turbulence piston noise. In the second application of coherence transfer from ground-to-geosynchronous orbit, we find the system should support high short-term coherence with ∼10 millirad phase noise on a 300 GHz carrier at essentially unlimited integration times.

On the Analyses of Propagation Characteristics and User Association for Sub-6 GHz and mmWave Carriers in Intelligent Reflecting Surfaces-Assisted Multi-tier 6G Networks

On the Analyses of Propagation Characteristics and User Association for Sub-6 GHz and mmWave Carriers in Intelligent Reflecting Surfaces-Assisted Multi-tier 6G Networks

23.1-Gb/s 135-GHz Wireless Transmission Over 4.6-Km and Effect of Rain Attenuation

In this article, we have experimentally demonstrated a fiber-wireless-integration <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D$</tex-math> </inline-formula> -band (110–170 GHz) transmission system. To extend the wireless transmission distance while maintaining the wireless bit rate as high as possible, we designed high-gain lens horn antenna modules consisting of a pair of dielectric plano-convex lenses and horn antennas for long-haul wireless links. In addition, we employ the Volterra nonlinear equalization (VNE) algorithm based on the multiple-input–multiple-output (MIMO) structure to precisely compensate for the in-phase/quadrature (I/Q) imbalance and nonlinear impairment of quadrature amplitude modulation (QAM) signals mainly caused by photoelectric (O-E) conversion and electric-photo (E-O) conversion. Meanwhile, one of the methods adopted in our experiment to decrease the influence of nonlinearity on high-order QAM signals is coupling the high-order modulation format with the probabilistic shaping (PS) technology. As a result of outdoor field experimental verification, the demonstration at 135 GHz carrier with a net rate of 23.1 Gb/s over 10 km optic-fiber and 4.6 km wireless transmission distance has been successfully carried out. It is, as we know, the first time that a record-breaking product of net bit rate and wireless transmission distance, i.e., 23.1 Gb/s <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 4.6 km <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 106.3 Gb/s <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot$</tex-math> </inline-formula> km, has been accomplished based on a fiber-wireless-integration system. Also, for the first time, we have measured the effect of rain attenuation for the 135 GHz millimeter-wave (mm-wave) wireless link and established more accurate rainfall models for the Shanghai region of China by comparing them with multiple rainfall models. This work can be used as a complement to the International Telecommunication Union-Radiocommunication sector (ITU-R) recommendations.

A Compact and Low Phase Noise Square-Geometry Quad-Core Class-F VCO Using Parallel Inductor-Sharing Technique

This article introduces a compact and low phase noise (PN) 19-GHz quad-core class-F voltage-controlled oscillator (VCO) based on a square-geometry transformer tank using the inductor-sharing technique. The proposed square-geometry transformer tank is inherently more compact than the prevalent topologies such as star geometry, dual-row geometry, and circular geometry. The inductor-sharing technique is introduced to merge neighboring inductors into smaller ones, which further reduces the chip area. Moreover, the proposed quad-core topology supports impedance boosting at harmonic frequencies without extra chip area consumption and class-F operation is adopted to achieve better PN performance. The quad-core VCO prototype is designed and fabricated in a 65-nm CMOS process. Measured performances are 17.6 to 19.4 GHz frequency range with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 137.2 dBc/Hz minimum PN at 10 MHz offset from 19 GHz carrier with 46 mW power consumption and 0.9-V supply, resulting a figure of merit (FoM) of 186.1 dBc/Hz. Thanks to the proposed square-geometry and inductor sharing technique, the proposed VCO is the smallest in quad-core VCOs with a similar operating frequency with a core chip area of 0.3 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 0.3 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2}$</tex-math> </inline-formula> and the corresponding FoM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm{A}}$</tex-math> </inline-formula> is 196.5 dBc/Hz.

Evaluation of Three-Level Code Division Multiplexing for High-Quality Radio over Fiber Communication

Radio over Fiber system (RoF) technology facilitates the transmission of wireless signals over optical fibers, which provides many benefits, including low signal loss, and immunity to electromagnetic interference. Despite these benefits, conventional RoF systems grapple with signal impairments and limited user capacity, as each user must be allocated a specific frequency. To address these limitations, this paper explores the implementation of the Three-Level Division Multiplexing (3LCDM) technique with RoF, a superior multiplexing strategy that allows two users to share a single channel, thereby doubling capacity. This innovative combination was evaluated for various cases using 2.4 GHz, 5 GHz, and the combination of 2.4 GHz and 5 GHz carrier frequencies, and its performance was compared with traditional RoF systems. Simulations were carried out using OptiSystem in cooperation with the MATLAB simulator. The findings of this study reveal that the 3LCDM-RoF system can accommodate twice the number of users as the conventional RoF system without the need for amplifiers. Furthermore, it supports higher bit rates and longer transmission distances. Specifically, the 3LCDM-RoF system achieved maximum data rates at maximum fiber length of 2 x 1.1 Gbps at 60 km, (2.4 GHz), 2 x 2 Gbps at 40 km (5 GHz), and 2 x 0.5 Gbps per channel at 43 km (combined 2.4 GHz and 5 GHz) respectively. Meanwhile, the conventional RoF with 2.4 GHz, 5GHz and the combination of 2.4 GHz and 5 GHz can only achieve maximum data rate at a maximum fiber length of 1.1 Gbps at 45 km, 1.6 Gbps at 35 km, and 0.4 Gbps at 35 km respectively

A 4–5.2 GHz PLL with 74.8 fs RMS jitter in 28 nm for RF Sampling Transceiver application

AbstractThis paper presents a novel ultra low jitter phase‐locked loop (PLL) circuit architecture for RF Sampling Transceiver. The programmable frequency divider with duty cycle expansion and the new phase frequency detector and charge pump circuit are used to solve the problem of voltage domain conversion of narrow pulses in the traditional high‐performance charge pump PLL structure. The traditional structure degrades charge pump linearity and noise, thus deteriorating overall jitter performance. Furthermore, voltage‐controlled oscillator uses the dual core structure and the second harmonic suppression technology, combined with the proposed new switching capacitor structure, and achieves −139.3 dBc/Hz phase noise at the 1 MHz frequency offset of the 5.2 GHz carrier under the open loop state. The PLL implemented in a standard Taiwan Semiconductor Manufacturing Company 28 nm process occupies a core area of 0.4 mm2 and generates a frequency ranging from 4 to 5.2 GHz using 50 MHz oscillator input, the power consumption is 40 mW. It achieves 74.8 fs root‐mean‐square jitter integrated from 10 KHz to 30 MHz. When the PLL output is divided by 2, the output phase noise at 1 MHz frequency offset is −125.75 dBc/Hz, and the PLL FoM is −246.

A 3.83–5.55 GHz high frequency resolution DCO with optimized switched‐capacitor ladder and low‐coupled eight‐shaped transformer

SummaryA high frequency resolution digitally controlled oscillator (DCO) is proposed for wireless transceivers, in which the scheme adopts an optimized cascaded differential switched‐capacitor (SC) ladder and a low‐coupled eight‐shaped transformer. The frequency resolution is further improved by the low electromagnetic coupling effect between the primary and secondary coils of the on‐chip transformer, thus reducing quantization noise and phase noise. An eight‐shaped transformer designed using two coils cross‐connected each other is adopted to reduce the magnetic coupling and frequency pulling. The proposed DCO is implemented in a TSMC 180‐nm CMOS process, and a tuning range of 36.7% from 3.83 to 5.55 GHz with a frequency resolution of 17 kHz is achieved. The phase noise is −120.29 dBc/Hz at 1 MHz offset from the 3.83 GHz carrier frequency. The DCO consumes 9.26 mA from a 1.8 V supply, while the figure of merit with tuning range is −191 dBc/Hz. The chip size is 0.294 mm2.

Study of 18.2-42.0GHz injection-locked frequency doubler with transformer input

This paper presents ultra-wideband 18.2-42.0 GHz LC injection-locked frequency doubler (ILFD) with transformer inputs. To expand the locking range, the proposed ILFD incorporates the transformer connected to the source of the gain-cell transistor to obtain high linearity of the input circuitry, moreover, the input matching frequency shifts from the free-run frequency of the oscillator. The measured maximum locking range exhibited 79.1% from 18.2 GHz to 42.0 GHz output at 0 dBm input power and the locked phase noise at 1MHz offset from 28 GHz carrier frequency was −112.1 dBc/Hz under 1.7 mW power consumption. Also, the lowest locked phase noise at 1 MHz offset from the carrier was −122.8 dBc/Hz under 21.2 mW power consumption, and it was only 2.2 dB degraded from the theoretical value. The process technology used in this work was TSMC-180nm CMOS.

Performance analysis of mmWave radio propagations in an indoor environment for 5G networks

Existing wireless communications in the sub-6 GHz bands are facing challenges from the growing demand for higher data rates and better quality of services. To satisfy these demands, the fifth generation (5G) mobile network would consider unused spectrum in the millimeter wave (mmWave) spectrum (30–300 GHz). The shortage of bandwidth in the sub-6 GHz band is solved using mmWave technology. Furthermore, mmWave provides significantly higher throughput, data rate, and capacity. Despite the fact that a huge bandwidth is employed, mmWave technology suffers from diffuse scattering from rough materials, path loss, reflection loss, atmospheric attenuation, building penetration loss, and shadowing which leads to a decrease in the transmitted signal power. Therefore, a reliable and accurate channel model is important in the mmWave bands, particularly for the indoor environment. Moreover, by using technologies like beam-forming and others coupled with mmWave, the listed impairments are minimized. In this work, we analyze the performance of different path loss models (CI, free space, and two rays) at 38, 60, and 73 GHz carrier frequencies in terms of path loss in terms of separation distance between transmitter and receiver. Additionally, we have evaluated the performance of the path loss with respect to the break point distance to enhance the received signal power and throughput. We have also done analysis of the directional power delay profile with received signal power, path loss and path loss exponent (PLE) at 38 GHz and 73 GHz mmWave bands for both LOS and NLOS by using uniform linear array (ULA) 2 × 2 and 64 × 16 antenna configurations using the channel model simulator (NYUSIM). The simulation results show the performance of different path loss models in the mmWave and sub 6 GHz bands. Path loss in the close-in (CI) model at mmWave bands is larger than that of free space and two ray path loss models, because it considers all shadowing and reflection effects between transmitter and receiver.

Design and planning of a 5G fixed wireless network

This research explains how to design and plan fixed wireless access connections in an urban setting using 5th generation (5G) technology in a multi-user urban scenario. Although the antennas used had a high gain, the 28 GHz carrier frequency proved incompatible with the connections due to path loss. The additional loss due to foliage led to a drop in the receiver sensitivity to -84 dBm. The loss due to weather conditions resulted in lower received signal strength. The lower frequency of 3.5 GHz performed better and is recommended to establish successful communication over multi-kilometer distances. As a result, this study demonstrates how vulnerable high 5G carrier frequencies are to typical path loss impairments.

60 Gbps real-time wireless communications at 300 GHz carrier using a Kerr microcomb-based source

Future wireless communication infrastructure will rely on terahertz systems that can support an increasing demand for large-bandwidth, ultra-fast wireless data transfer. In order to satisfy this demand, compact, low-power, and low noise sources of terahertz radiation are being developed. A promising route to achieving this goal is combining photonic-integrated optical frequency combs with fast photodiodes for difference frequency generation in the THz. Here, we demonstrate wireless communications using a 300 GHz carrier wave generated via photomixing of two optical tones originating from diode lasers that are injection locked to a dissipative Kerr soliton frequency microcomb. We achieve transfer rates of 80 Gbps using homodyne detection and 60 Gbps transmitting simultaneously both data and clock signals in a dual-path wireless link. This experimental demonstration paves a path toward low-noise and integrated photonic millimeter-wave transceivers for future wireless communication systems.

A Long‐Term Experimental Investigation on the Impact of Rainfall on Short 6G D‐Band Links

AbstractResults from a long‐term propagation campaign are presented, whose main goal is to investigate the impact of rainfall on short terrestrial links operating at frequencies in the D‐band, to be possibly exploited for backhaul links in future 6G mobile networks. To this aim, data are collected at two sites with different climatic conditions (Milan, Italy; Athens, Greece) for 24 and 20 months, respectively, using two links (path length of 325 and 100 m, respectively), operating at 156 GHz carrier frequency. At the same sites, disdrometers are also installed to concurrently collect information on precipitation, not only in terms of rain rate but also of its microphysical properties. The received power data are carefully pre‐processed to exclude outliers and further elaborated to derive the rain attenuation. The data are afterward used to evaluate the accuracy of different prediction models, both on an event basis and on a statistical basis. Results indicate that the information delivered by the Drop Size Distribution allows a more accurate estimation of the rain attenuation and that the model currently adopted by the ITU‐R to predict rain attenuation statistics on terrestrial links (recommendation ITU‐R P.530‐18) yields a significant overestimation for such short links, due to the unrealistic value of its path reduction factor. On the contrary, the statistical prediction model proposed by Lin turns out to offer a very satisfactory prediction accuracy.

Dual-frequency fundamental-mode NPRO laser for low-noise microwave generation.

Monolithic nonplanar ring oscillators (NPROs) have achieved great success in industry, scientific applications and space missions due to their excellent narrow-linewidth, low-noise, high beam-quality, lightweight and compact performances. Here, we show that stable dual-frequency or multi-frequency fundamental-mode (DFFM or MFFM) laser can be stimulated directly by tunning pump divergence-angle and beam-waist injected to NPRO. The DFFM laser has a frequency deviation of one free spectral range of the resonator and thus can be utilized for pure microwave generation by common-mode-rejection. To demonstrate the purity of the microwave signal, a theoretical phase noise model is established, and the phase noise and the frequency tunability of the microwave signal are experimentally studied. Single sideband phase noise for a 5.7 GHz carrier is measured as low as -112 dBc/Hz at 10 kHz offset, and -150 dBc/Hz at 10 MHz offset in the free running condition of the laser, which outperforms its counterparts from dual-frequency Laguerre-Gaussian (LG) modes. The frequency of the microwave signal can be efficiently tunned through two channels, with frequency tunning coefficients of 15 Hz/V by piezo, and -60.5 kHz/K by temperature, respectively. We expect that such compact, tunable, low-cost and low-noise microwave sources can facilitate multiple applications including miniaturized atomic clocks, communication and radar, etc.

A 7.6–12.3 GHz wide‐band PLL with an ultra low reference spur −81.1 dBc in 0.13 μm CMOS technology

AbstractThis paper presents a wide‐band charge‐pump phase‐locked loop (CPPLL) with reference spur reduction techniques. To broaden the frequency range without deteriorating phase noise, a 6‐bit capacitor array‐based VCO and an automatic frequency calibrator (AFC) are used. A compact loop filter technique saves the capacitor area and maintains the bandwidth. Also, a novel charge pump with dynamic current matching circuit is proposed to reduce the reference spur of the PLL. The current mismatch is less than 0.22 A (0.16%) over the voltage range from 0.75 to 1.55 V. Fabricated in 0.13 m CMOS technology, the proposed PLL achieves a locking range of 7.6–12.3 GHz (47.2%), with a 25 MHz frequency interval. The PLL consumes 23.3 mA from a 2.5 V supply voltage and occupies a core area of 0.92 mm 0.72 mm. The reference spur of the proposed PLL is measured to be −81.1 dBc, and in‐band phase noise reaches −110.8 dBc/Hz at 1 MHz offset frequency from the 9.5 GHz carrier frequency.

Photonic Generation of Background-Free Phase-Coded Pulses With Low Power Fluctuation Over the Multi-Octave Frequency Range

In this article, a photonic microwave signals generation scheme for background-free phase-coded (PC) radar pulse with multioctave tuning is experimentally demonstrated. Firstly, an optical frequency comb (OFC) demultiplexing technology based on optical injection locking (OIL) provides a power-equalized coherent optical local oscillator (LO) with ultra-broadband tuning capability. Then, a phase-modulated optical signal is produced based on the conversion intensity modulation to phase modulation. Finally, a background-free phase-coded signal can be obtained by beating the optical signal with LO at a balanced photodetector (BPD). The proposed scheme features a flat frequency response over an ultra-wideband frequency range without needing a broadband modulator and radio frequency (RF) synthesizer. A proof-of-concept experiment demonstrates that the power fluctuation of 0.5 Gbps background-free PC pulses is lower than 3.12 dB within 3∼24 GHz carrier frequency. Furthermore, the pulse compression performance and system stability are investigated, respectively.

A 6.7 GHz, 89.33 μW Power and 81.26% Tuning Range Dual Input Ring VCO with PMOS Varactor

This paper proposes an improved two-stage and four-stage CMOS ring-Voltage Controlled Oscillator (VCO) design with large frequency at output, improved phase noise, and reduced consumption of power. A PMOS varactor is used in conventional circuit to obtain high tuning-range and very low consumption of power. Cadence Virtuoso 90 nm technology was used to simulate this differential ring-VCO with the proposed dual input differential delay cell. This two-stage and four-stage design gives wider range of tuning from 1.254 to 6.694 GHz (81.26%) and 1.821 to 5.259 GHz (65.37%), respectively, with the change in [Formula: see text] from 0.1 to 1 V. The power-consumption of two-stage ring VCO and four-stage ring VCO varies from 48.02 to 89.33 [Formula: see text] and 66.81 to 157.02 [Formula: see text] respectively. The proposed two-stage and four-stage VCO exhibits −114.46 and −111.06 dBc/Hz at 1 MHz offset from 6.694 and 5.259 GHz carrier frequency, respectively. The proposed two-stage and four-stage differential ring-VCO results in wider tuning range and very low consumption of power and an improved figure of merit and phase-noise.

166% frequency tuning range power VCO using high-quality off-chip inductor

This work presents a complementary PMOS NMOS voltage-controlled power oscillator (VCO) based on a high quality (Q) factor off-chip inductor in 130 nm CMOS process. The proposed VCO achieves a frequency tuning range of 166% from 393 MHz to 4.17 GHz and this wide tuning range is divided into six bands where each band is also sub-divided into three bands using a single switching voltage. The proposed design takes into consideration the effect of the bond wire that is used to connect the off-chip inductor with the VCO core moreover, the measured SNP files of the off-chip inductors are utilized to ensure accurate results. This technique improves the figure of merit (FoM) by 4–25 dB compared to the conventional inductor VCO. Using six different values of the off-chip inductors, the proposed VCO works in six bands with a tuning range of 166%, and a minimum phase noise of − 127 dBc/Hz @ 1 MHz offset frequency 2.2 GHz carrier. Furthermore, the proposed VCO draws 1.37 mA from 1.1 V supply voltage and has a minimum achieved Figure-of-Merit (FOM) equal to -193 dBc/Hz with a maximum output power of 4.25 dBm. The VCO core area equals 0.07 {mathrm{mm}}^{2}, while the total chip area including RF pads and output buffers is {0.437mathrm{ mm}}^{2}.