GHz Carrier Frequency Research Articles

A 0.045- to 2.5-GHz Frequency Synthesizer With TDC-Based AFC and Phase Switching Multi-Modulus Divider

A 0.045- to 2.5- GHz wideband frequency synthesizer (FS) employing time-to-digital converter (TDC) based automatic frequency calibration (AFC) method and phase switching (PS) multi-modulus divider (MMD) is presented in this paper. The traditional counter-based AFC method takes several reference cycles to calculate the instantaneous voltage-controlled oscillator (VCO) frequency, while the proposed TDC-based technique consumes only 2 cycles. In order to suppress the quantization noise caused by the sigma-delta modulator (SDM) in the MMD, the loop division step is reduced from 2 to 0.5 by adopting the PS technique. The FS is designed and implemented using TSMC 180nm RF CMOS process and provides the phase noise performance of −99.5 / −123.5 dBc/Hz at 10kHz/1MHz offsets under 2.4 GHz carrier frequency. The AFC time measurement results for a 6-bit cap-array are 1.25-, 2.5- and 5- $\mathrm {\mu s}$ when employing 48-, 24- and 12-MHz reference frequencies respectively. The chip area including pads and I/Os is 2.31 mm $^{\mathbf {2}}$ and the total power consumption is 108 mW.

A Design of Wide-Range and Low Phase Noise Linear Transconductance VCO with 193.76 dBc/Hz FoMT for mm-Wave 5G Transceivers

This paper presents a wide-range and low phase noise mm-Wave Voltage Controlled Oscillator (VCO) based on the transconductance linearization technique. The proposed technique eliminates the deep triode region of the active part of the VCO, and lowers the noise introduced by the gm-cell. The switch sizes inside the switched capacitor bank of the VCO are optimized to minimize the resistance of the switches while keeping the wide tuning range. A new layout technique shortens the routing of the VCO outputs, and lowers the parasitic inductance and resistance of the VCO routing. The presented method prevents the reduction of the quality factor of the tank due to the long routing. The proposed VCO achieves a discrete frequency tuning range, of 14 GHz to 18 GHz, through a linear coarse and middle switched capacitor array, and offers superior phase noise performance compared to recent state-of-the-art VCO architectures. The design is implemented in a 45 nm CMOS process and occupies a layout area (including output buffers) of 0.14 mm2. The power consumption of the VCO core is 24 mW from the power supply of 0.8 V. The post-layout simulation result shows the VCO achieves the phase noise performances of −87.2 dBc/Hz and −113 dBc/Hz, at 100 kHz and 1 MHz offset frequencies from the carrier frequency of 14 GHz, respectively. In an 18 GHz carrier frequency, the results are −87.4 dBc/Hz and −110 dBc/Hz, accordingly.

Intermediate frequency variation in long‐range FMCW radar for harmonics cancellation

This study presents a technique for removing the inevitable harmonic distortions and intermodulation products that primary frequency-modulated continuous wave (FMCW) radars inherently generate in the baseband. The required mixers and baseband amplifiers are non-linear devices that introduce signal distortions, depending on the positions of targets in the field of view. Target distances are directly coupled to their corresponding baseband frequencies. The mitigation strategy presented in this study involves changing the resulting baseband frequencies of targets by varying the mixer deramping frequency input. After applying a processing algorithm that involves spectral rotation and combination, harmonic contributions can be suppressed to a high degree, while target-related signals remain the same. After only four iterations, a gain of 30 dB in spurious free dynamic range can be achieved that can even be improved with more time on target. This behaviour is not only observed in simulations, but is also proven with measurements using an FMCW radar, working at a 3 GHz carrier frequency. The algorithm is applicable to radar systems that work in any frequency band.

Design and Characterization of Wideband Aperture-Coupled Circularly Polarized Antenna for Gigabits Per Second Wireless Communication System

In this paper, design and characterization of an aperture-coupled circularly polarized (CP) rectangular patch antenna suitable for Gigabit per second wireless communications system is presented. The proposed antenna exhibits a large bandwidth of 2.77 GHz at centre frequency $${\text{f}}_{\text{c}}$$ = 19.5 GHz (about 15% of fractional bandwidth (FBW)). It also has a gain of about 7.25 dBi at 18 GHz with good stable gain and radiation characteristics in the frequency band of interest. For indoor wireless channel measurements, two developed prototypes are employed as single input single output transmit receive (TX–RX) antennas with a robust and versatile channel modeling system. We demonstrate a measurement campaign to investigate the dynamic range of the system by calculating path loss. The pulse dispersion effect is quantified by pulse fidelity factor (PFF). The measurements are performed in laboratory environment using Gaussian pulse based sounding signal modulated at 19.3 GHz carrier frequency. The design and characterization of compact size antennas with pertinent bandwidth and excellent radiation characteristics is one of our initiatives towards developing a millimeter wave (MMW) test bed system for channel modeling and measurement, since 5G wireless communication is supposed to operate in MMW band.

A 17.6-to-24.3 GHz −193.3 dB figure-of-merit LC voltage-controlled oscillator using layout floorplan optimization technique for Q-factor enhancement

This paper presents a 20 GHz low-phase-noise low-power LC voltage-controlled oscillator (VCO). It adopts a fully differential tuning varactor, a coarse and a fine capacitor array to cover wide tuning range with a small tuning gain to reduce the amplitude-to-phase noise conversion. A layout floorplan is proposed to reduce the impact of the parasitic resistance of the interconnect and thus improve the Q of the LC tank in the VCO. Hence, the phase noise can be reduced without increasing power consumption. Post-layout simulation results show that the VCO with the proposed layout floorplan can get the phase noise reduction from 1.6 to 3.3 dB compared to the VCO with other layout floorplans in the case of the same power consumption. Implemented in a 65 nm CMOS process, the prototype achieves 17.6–24.3 GHz frequency range, −124 dBc/Hz@10 MHz phase noise at 20.1 GHz carrier frequency, 4.9 mW DC power, and −193.3 dB figure-of-merit.

Learning to Predict the Mobility of Users in Mobile mmWave Networks

MmWave communication suffers from severe path loss due to high frequency and is sensitive to blockages because of high penetration loss, especially in mobile communication scenarios. It highly depends on line-of-sight channels and narrow beams, and thus efficient beam tracking and beam alignment are necessary techniques to maintain robust communication links, in which tracking user mobility lays the foundation for beam tracking. In this article, ML techniques are applied to learn the mobility of the mobile mmWave users and predict their moving directions. Moreover, this article builds up an experiment environment by using the National Instruments mmWave transceiver system and our designed high gain antenna operated at 28 GHz carrier frequency, and then collects experimental data of the transmitted mmWave signals, which are next trained by deep learning algorithms. A deep neural network is learned and then used to predict a user's moving direction with up to 80 percent prediction accuracy in mmWave communication without the support of traditional channel estimation.

An Ultra-Low Power, Adaptive All-Digital Frequency-Locked Loop With Gain Estimation and Constant Current DCO

In this paper, an ultra-low power, adaptive all-digital integer frequency-locked loop (FLL) with gain estimation and constant current digitally controlled oscillator (DCO) for Bluetooth low energy (BLE) transceiver in Internet-of-Things (IoT) is presented. For locking DCO frequency closest to the target channel, it adaptively controls capacitor banks with binary algorithm. With decrease in frequency resolution, DCO clock counts for each capacitor bank bit evaluation dynamically increases with the proposed technique for accurate frequency tracking. For compensating PVT variations and finding the BLE frequency deviation, the configurable digital DCO gain estimation is incorporated. The low power and constant current DCO operates in sub-threshold region and its power consumption is minimized by g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</sub> methodology optimization, constant current source for limiting current in DCO core through adaptive low-dropout regulator (LDO) and lowering the supply voltage. The proposed design is integrated in an ADPLL for BLE transceiver and it is fabricated with 1P6M TSMC 55 nm CMOS technology. The all-digital adaptive FLL is fully synthesizable and its area is 1800 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with 1.233 K gate count. The RMS current consumption is 103.32 μA from 1 V voltage supply with 103.32 μW power requirement. The experimental results reveal, DCO draws 480 μA current from 0.55 V supply voltage at center frequency. It has frequency resolution of 4.8 kHz. The oscillator PN, FOM and FOMT at 1-MHz offset frequency from 2.44 GHz carrier frequency are -122.85 dBc/Hz, 196.38 dBc/Hz and 208.19 dBc/Hz, respectively.

LTE-V2X System Performance Based on Urban-Low Speed Environment

Vehicular Ad Hoc Networks (VANETs) is an important field of study nowadays. VANETs attracts attention of vehicles communication researcher due to its potential to improve vehicle road safety, enhance traffic and travel efficiency, and provide convenience and comfort for passengers and drivers. Due to the fact that modern life, especially when travelling in vehicles, is in need for high throughput, this paper investigates the Block Error Rate (BLER) and throughput performance of vehicle-to-Infrastructure (V2I) communication between LTE node and vehicles in urban-low environment using two different stochastic channel model used urban-low areas because urban-low speed areas is the common road situation for a large number of users require connection with LTE node. Vehicle-to-Infrastructure - Urban (V2I-U) is used in urban areas and Vehicle-to-Infrastructure – Urban Small intersection (V2I-US) channel model, used as a reference model, has the largest maximum excess delay near to the 3GPP Extended Vehicular A (EVA) channel model. The performed simulation is done at low speed, 40 km/h in 10 MHz bandwidth for the 2.6 GHz carrier frequency. Results show that V2I-U meets the highest value in the throughput that reaches 20 Mbps as those obtained from the EVA one without huge effect on the BLER. This result can be attributed to the fact of using Line-of-Sight (LoS) which leads to less dispersion of the frequency and less doppler frequency shift.

Design of a Voltage-Controlled Oscillator for Ka-Band Applications

ABSTRACTA varactor-less cross-coupled voltage-controlled oscillator based on triple frequency is presented in this paper, which is optimized for a low phase noise and low power at the high frequency. The VCO consists a voltage to current, a triple frequency, and a mixer with band-pass filter. The varactor-less VCO adjusts the frequency with the current and voltage of transconductance cell. A network RF–CF–RF is applied to filter out the noise of current source at 2. The proposed circuit was simulated in a 0.18 µm CMOS RF technology with a 1.5 V supply voltage. The designed VCO demonstrates an oscillation frequency range from 11.59 to 13.96 GHz with the triple frequency from 35.8 to 40.3 GHz. The simulated VCO presents a phase noise of −110.1 dBc/Hz at 1 MHz offset from a 40.3 GHz carrier frequency. The total figure of merit (FOMT) is −193.113 and −190.83 dBc/Hz with a DC power of 11.32 and 19.56 mW for VCO and total structure, respectively. The layout of the VCO occupies an area of 695.10 µm 627.80 µm.

A robust multi‐sampling rate digital predistortion for ultra‐broadband power amplifiers

AbstractIn this letter, a robust multisampling rate digital predistortion (DPD) scheme is proposed to linearize ultra‐broadband power amplifiers (PAs) under the limited DAC sampling rate. In the ultra‐broadband scenarios, it is no longer affordable to employ DACs with 3‐5 times over‐sampling rate, which will inevitably lead to spectrum aliasing for the sake of high order basis function and compromise the DPD performance. In order to improve the modeling accuracy, the input signal with low sampling rate will be up‐sampled firstly to generate nonaliasing basis functions. Then, after filtering and down‐sampling operation, the coefficients are extracted with low sampling rate. Moreover, the conventional behavioral model is modified with the linear‐spline basis functions to improve the stability and complexity. Measurements on Doherty PA and class‐AB PA with 100 MHz, 200 MHz, and 500 MHz bandwidth input signal at 2.1 GHz carrier frequency show the EVM can be improved to 0.71%, 0.94%, and 1.86% respectively.

Microwave Photonic Multifunctional Phase Coded Signal Generator

A novel phase coded signal generator is proposed and experimentally verified. The scheme consists of a dual-polarization quadrature phase shift-keying (DP-QPSK) modulator and a phase modulator in a Sagnac loop. By properly adjusting the bias voltages of the DP-QPSK modulator and the polarization direction of the signal, two-order optical sideband is polarization separated from the carrier and −2-order sideband. We can modulate the two-order optical sideband with phase coded data and two phase coded signals will be generated which are the beating products between the modulated two-order optical sideband and the unmodulated optical sidebands in balanced detector. The distinct advantage of our approach is that we integrate multiple functions into a compact system which can simultaneously generate dual-band and multi-phase coded signal with doubled and quadrupled frequency. In the experiment, 1-Gbit/s binary and quaternary phase coded signals with 11 and 22 GHz carrier frequencies are generated by using of a 5.5 GHz local oscillator signal.

Photonic Generation of a Dual-Band Polyphase-Coded Microwave Signal With a Tunable Frequency Multiplication Factor

A photonic approach to generate dual-band polyphase-coded microwave signal with a tunable frequency multiplication factor is proposed. The scheme contains a dual-polarization quadrature phase-shift-keying (DP-QPSK) modulator, a polarization modulator (PolM), and a balanced detector. When the bias voltages of the DP-QPSK modulator is properly adjusted, a double-sideband signal will be generated with one sideband along the X polarization of the PolM, with the optical carrier and the other sideband along the Y polarization. Then, the PolM is employed to modulate the optical signal with a phase-coded microwave signal. After the photoelectric balanced detection, polyphase-coded microwave signals with frequency multiplication factors of one, two, and four can be generated. In addition, the proposed scheme can simultaneously produce two phase-coded microwave signals with different carrier frequencies. The proposed system finds a potential application in dual-band radar. In the experiment, a binary- and a quaternary-phase-coded signal with 5.5, 11, and 22 GHz carrier frequencies are generated.

Statistical Blockage Modeling and Robustness of Beamforming in Millimeter-Wave Systems

There has been a growing interest in the commercialization of millimeter wave (mmW) technology as a part of the Fifth-Generation New Radio (5G-NR) wireless standardization efforts. In this direction, many sets of independent measurement campaigns show that wireless propagation at mmW carrier frequencies is only marginally worse than propagation at sub-6 GHz carrier frequencies for small-cell coverage --- one of the most important use-cases for 5G-NR. On the other hand, the biggest determinants of viability of mmW systems in practice are penetration and blockage of mmW signals through different materials in the scattering environment. With this background, the focus of this paper is on understanding the impact of blockage of mmW signals and reduced spatial coverage due to penetration through the human hand, body, vehicles, etc. Leveraging measurements with a 28 GHz mmW experimental prototype and electromagnetic simulation studies, we first propose statistical blockage models to capture the impact of the hand, human body and vehicles. We then study the time-scales at which mmW signals are disrupted by blockage (hand and human body). Our results show that these events can be attributed to physical movements and the time-scales corresponding to blockage are hence on the order of a few 100 ms or more. Building on this fundamental understanding, we finally consider the broader question of robustness of mmW beamforming to handle blockage. Network densification, subarray switching in a user equipment (UE) designed with multiple subarrays, fall back mechanisms such as codebook enhancements and switching to legacy carriers in non-standalone deployments, etc. can address blockage before it leads to a deleterious impact on the mmW link margin.

1/f3 (Close-in) Phase Noise Reduction by Tail Transistor Flicker Noise Suppression Technique

In this paper, a novel circuit method is proposed to reduce 1/f3 (close-in) phase noise in a cross-coupled LC Voltage Control Oscillator (VCO) by suppressing flicker noise power of the tail transistor. Using an added resistor between drain and gate of the tail transistor, that works as a negative feedback, the tail transistor flicker noise is suppressed, and therefore, the 1/f3 output phase noise is reduced by 5.7[Formula: see text]dB. Also, the added resistor helps in better tail current shaping for phase noise reduction. The proposed oscillator is designed in a 0.18[Formula: see text][Formula: see text]m CMOS technology with 1.8[Formula: see text]V supply and 3.6[Formula: see text]mW power consumption. Post-layout simulations predict a phase noise of [Formula: see text][Formula: see text]dBc/Hz for the proposed oscillator at 100[Formula: see text]KHz offset from 3.1[Formula: see text]GHz carrier frequency. Mathematical analysis is included in the paper for confirmation of the phase noise performance enhancement. The Figure of Merit (FOM) of the proposed oscillator is 188.3 and 190.6[Formula: see text]dBc/Hz at 100[Formula: see text]KHz and 1[Formula: see text]MHz offsets, respectively.

Extending Spatial and Temporal Characterization of Indoor Wireless Channels From 350 to 650 GHz

Communication at terahertz carrier frequencies is a promising way to satisfy the ever-growing demands for high-speed wireless networks. The studies of terahertz wireless channels have so far been limited to the atmospheric transmission bands below 350 GHz. Availability of high-power transmitters and high-sensitivity receivers at higher frequencies necessitates extending the wireless channel studies to enable higher data-rate communication systems. With a view to assessing communication system design requirements at higher frequencies, we present the channel measurement results for 650-GHz carrier frequencies in comparison with 350 GHz carrier frequencies in a typical indoor environment. To obtain the spatial and temporal characteristics of the channel, the power angle profile and the power delay profile are measured based on new measurement methods. Multiple spatially resolvable paths are observed at both 350- and 650-GHz carrier frequencies. Signal-to-noise ratio of the received signal through the non-line-of-sight (NLoS) paths is sufficiently high to enable robust communication when the direct line-of-sight (LoS) path is blocked due to a moving object. The measurement results are used to calculate the reduction in the 650-GHz channel capacity in comparison with that of the 350-GHz channel for both LoS and NLoS paths. Channel dispersion characterization over a 10-GHz bandwidth shows that the delay spreads for the resolved LoS and NLoS paths are less than 80 ps for both 350- and 650-GHz bands. Therefore, no complicated equalizer is required to compensate for channel dispersion at both 350 and 650-GHz, which greatly simplifies the terahertz transceiver design.

RAYLEIGH FADING - SHADOWING OF OUTDOOR CHANNELS ANALYSIS BASED ON SNR-PDF MODEL

The outdoor transmission channels condition in multiple wireless signals systems changes continuously due to signals transfer path characteristics. The path loss, multiple reflected rays Rayleigh fading and shadowing presents an important factor that effects inconsistent with signals propagation through the wireless channels of communication systems. The solutions for these effects will contribute to minimize the error probability of transferred data and maximize the data rate in high speed systems. This paper deals with the analysis of error probability using Probability density function (PDF) model of Signal to Noise ratio (SNR) for different values of transmitted signals power at outdoor receiver of multi users systems. The proposed approach use Rayleigh fading channels, 2GHz carrier frequency, (0-30) dB SNR, (0.1,0.2,0.3), (1,2,3) and (10,20,30) PW. The relationship between error probability and SNR has been studied to determine efficient transmission channels. The proposed channel model has been simulated and analyzed using MATLAB R2012b software under different users power signals values. The obtained results have showed accuracy as well as efficiency of the proposed method where the error probability is decrease when the SNR increase and the error probability decrease when decrease in the transmitted power signal.

Pilot Allocation and Computationally Efficient Non-Iterative Estimation of Phase Noise in OFDM

This letter proposes a pilot subcarrier allocation approach for orthogonal frequency division multiplexing systems, which enables construction of symbol-wise phase-noise (PN) estimates with high efficiency and low overhead in a non-iterative manner. The complexity and performance of the overall PN suppression algorithm together with the proposed pilot allocation approach are evaluated in 5G single-user-multiple-input multiple-output (MIMO) and multi-user-MIMO radio links at 28 GHz carrier frequency, showing clear complexity-performance benefits against a state-of-the-art reference algorithm.

On-chip GaN-on-SiC VCO using a tunable substrate integrated waveguide loaded with complementary split ring resonator

ABSTRACTThis paper presents an S-band voltage-controlled oscillator (VCO) using a tunable half-mode substrate integrated waveguide (HMSIW) loaded with complementary split ring resonator (CSRR) in GaN-on-SiC high-electron-mobility transistor technology. A varactor connected to the center of the outer conductor of the HMSIW-CSRR changed the effective capacitance, resulting in a resonance frequency shift but a fixed transmission zero. Therefore, the S-band VCO can be tuned by the HMSIW-CSRR using harmonic suppression. The tunable HMSIW-CSRR VCO exhibited a frequency tuning range of 3.55–3.98 GHz with a varactor voltage of 0–6 V. The maximum output power was 21.1 dBm and rf-to-dc efficiency was 12.8% at 3.98 GHz. The lowest phase noise was −117 dBc/Hz with 1-MHz offset at a 3.56 GHz carrier frequency with 30.55 dBc of harmonic suppression.

Design of low phase-noise oscillators based on microstrip triple-band bandpass filter using coupled lines resonator

This paper presents new low phase noise oscillators employing a triple-band bandpass filter as a frequency stabilization element into the feedback loop. In addition, using triple-band bandpass filter (TB-BPF); three oscillators can be easily achieved separately, only by changing the length of the transmission line in feedback loop. The oscillators are designed at the spectrum-based quality factor (Qs) peak frequencies of bandpass filter to achieve low phase noise performance. Also, the oscillation frequencies of the oscillators are designed at 3.4, 4.33 and 6.89 GHz, resulting in achieving the simulated phase noise of these oscillators are −166, −154 and −150 dBc/Hz at the 1-MHz offset frequency respectively. The oscillator with 3.4 GHz carrier frequency is fabricated and the measured results show the 10.7 dBm output power and phase noise is −163 dBc/Hz at 1-MHz frequency offset. The figure of merit of the fabricated oscillator at 1 MHz offset frequency is −218.9 dBc/Hz.

Tri-Phasing Modulation for Efficient and Wideband Radio Transmitters

In this paper, we show that amplitude transitions that are inherent to the multilevel outphasing radio transmitter architecture distort the transmitted signal due to time-domain discontinuities. In order to address this challenge, we propose a new transmitter architecture called tri-phasing which avoids discontinuities in signal waveforms and thus achieves significantly better linearity than multilevel outphasing. The output waveform in tri-phasing can be made continuous by representing the baseband signal with three components. One of the three components is amplified by discrete amplitude steps, whereas the other two are used to compensate the instantaneous shift in the output waveform due to the discrete amplitude step and to provide fine amplitude resolution. An implementation of the tri-phasing transmitter requires three phase modulators and additional digital signal processing. The system-level simulations performed in this paper demonstrate that the ACLR of a multilevel outphasing transmitter with 4 amplitude levels and 10-bit phase resolution is limited to −48 dBc, when simulated with a 100 MHz carrier-aggregated LTE downlink signal at 2.46 GHz carrier frequency. The proposed tri-phasing transmitter achieves −58 dBc ACLR with the same simulation parameters, indicating that continuous amplitude transitions can significantly improve the transmitter linearity.