Millimeter-wave Signal Research Articles

Low phase noise and quasi-tunable millimeter-wave generator using a passively InAs/InP mode-locked quantum dot laser

A low phase noise millimeter-wave (MMW) signal generator is proposed and experimentally demonstrated with a C-band passively Fabry-Perot (F-P) quantum dot mode-locked laser. A novel method is proposed to generate low phase noise MMW signal, which is simply based on a commercial off-the-shelf dual-driven LiNbO3 Mach-Zehnder modulator and a passively F-P quantum dot mode-locked laser. MMW signal with the frequency of 30 GHz, 45 GHz and 90 GHz respectively is obtained experimentally. Single-sideband phase noise of the 30 GHz and 45 GHz MMW signal is −112 dBc/Hz and −106 dBc/Hz at an offset of 1 kHz, respectively. The linewidth of the 30 GHz and 45 GHz MMW signal is about from 225 Hz and 239 Hz. This is considered a very simple MMW generator with a quasi-tunable broadband and ultra-low phase noise.

Dual band radio-over-fibre millimetre–wave system utilizing optical frequency combs

Abstract The urge for high-speed data transmission never ends. The demand for seamless online video streaming services demands a faster data transmission rate. To fulfil the demand optical communication can be used to enhance the overall performance. The union of microwave and optical networks known as Radio-over-Fibre (RoF) technology, may be a reasonable solution for improving capacity and mobility likewise as decreasing costs within the access network. Millimetre-wave (mm-wave) signals can be utilized for multi-Gb/s transmission. But mm-wave generation in the electrical domain is less feasible. Here, the optical domain comes into play. In this paper, two mm-wave frequencies are generated using optical frequency combs (OFCs). This technique is an effective solution for the mm-wave RoF system for 5G and beyond. By simulation, the major restraints of linewidth and relative intensity noise (RIN) are explored. RIN level of −163 dB/Hz is achieved.

Joint access and backhaul resource allocation for D2D-assisted dense mmWave cellular networks

Device-to-Device (D2D) communication technology is a promising solution to solve the problem that millimeter-wave (mmWave) signal propagation is vulnerable to blockage and thus rapidly weakened. However, after introducing in-band D2D communication to dense mmWave cellular networks, we must consider how to reasonably share resources and effectively control interference between more types of communication links (e.g., D2D, access, backhaul), which makes the resource allocation problem more challenging. In other words, it is more challenging to investigate joint access and backhaul resource allocation problem for in-band D2D-assisted dense mmWave cellular networks. To address this challenging problem, we firstly decouple it into the two sub-problems (i.e., joint access and backhaul resource allocation sub-problem, and joint D2D access and forwarding link resource allocation sub-problem). Then, we formulate the two sub-problems as the two non-cooperative games respectively and prove that they are exact potential game and there exist feasible pure strategy Nash equilibrium under some mild conditions. Finally, based on the formulated game models, we propose a centralized algorithm and a decentralized algorithm to get resource allocation results respectively. The extensive simulation results show that the proposed algorithms can effectively mitigate the impact of blockage on network performance.

High-Density Plasma Diagnosis Using Quasi-Optical Millimeter-Wave Systems

This report proposes a quasi-optical millimeter-wave system based on a noninvasive measurement technique to diagnose high-density plasmas. The millimeter wave in the F-band (90–140 GHz) can interact with high-density plasma (1013–1014 cm−3) in the quasi-optical system, such that the plasma characteristics (e.g., plasma density and effective collision frequency) obtained using the Drude model can be measured with a high signal-to-noise ratio. High-density inductive radio frequency (RF) discharge argon plasma is generated in a helix of inductively coupled plasma using RF power of up to 1000 W at 13.56 MHz with a pressure of a few Torr. The millimeter-wave signals can be analyzed to estimate the plasma-density distribution by using the proposed axisymmetric 2-D multilayered plasma modeling. The experimental results agreed well with the model calculations. Qualitatively, the plasma density tends to increase with increasing RF power and gas pressure. The effective collision frequency decreases only with increasing gas pressure. The proposed measurement technique will also be applicable to measuring localized regions (with areas of a few square millimeters) of higher density plasma (1014–1017 cm−3) by using terahertz waves for various applications.

A simple photonic precoding-less scheme for vector millimeter-wave signal generation based on a single phase modulator

We propose and verify a simple precoding-less scheme to generate quadrature phase shift keying (QPSK) modulated vector millimeter-wave signal based on a single phase modulator (PM). The electrical vector data is first up-converted to achieve a 12 GHz radio frequency (RF) vector signal, then the RF vector signal is added with the other unmodulated RF source at 18 GHz, of which the generations are enabled by a digital signal processing (DSP). Next, the coupled RF source drive a PM to generate multi-frequency optical sidebands. A wavelength selective switch is adopted to pick out two optical sidebands at different frequencies which will beat frequency in the photo-detector (PD). In this scheme, we set up a simulation platform to generate 48 GHz QPSK modulated vector millimeter-wave signals and analyzed the performance. The results show when the input power for the generated 1-Gbaud/s vector millimeter-wave into PD is not less than −18 dBm, the bit-error ratio can be below 3.8 × 10−3, which demonstrate that the generated vector millimeter-wave signal enabled by our proposed scheme can work well.

Integrated waveguide true time delay beamforming system based on an SOI platform for 28 GHz millimeter-wave communication.

In this paper, we propose an on-chip waveguide beamforming system for a 28 GHz millimeter-wave signal based on silicon-on-insulator (SOI) technology. The system consists of four true time delay (TTD) lines, each of which consists of nine Bragg gratings with different periods. The minimum period of the grating is 312 nm, and the maximum period is 344 nm. By optimizing the position of the Bragg grating in the adjacent TTD lines, a time delay difference can be generated between the adjacent channels. By adjusting the operation wavelength of the optical carrier, the TTD lines can provide 9 different beamforming direction angles from -60∘ to 60° when the direction angular resolution is 15°. This proposed system has a useful application prospect in the phased array antennas of millimeter-wave communication.

Integrated group delay units for real-time reconfigurable spectrum sensing of mm-wave signals.

Real-time spectrum sensing is crucial to enable dynamic spectrum sharing for ubiquitous wireless communication with seamless high-quality wireless services. In this contribution, we demonstrate a reconfigurable real-time spectrum sensing photonic integrated chip (RTSS-PIC) for millimeter-wave (mm-wave) signals, based on the temporal discrimination of multi-channel input frequencies by the peak group delays of cascaded ring resonators. Large group delays and wide bandwidths are realized by the strategic tuning of thermal phase shifters. To make the spectrum sensing fully reconfigurable, positive and negative group delay profiles are utilized. Furthermore, a unique frequency-to-time mapping technique is introduced to analyze all input channels in real time. To illustrate the method, real-time spectrum sensing for two different mm-wave signals are finally tested by full-wave simulations of the proposed RTSS-PIC.

Filterless radio-over-fiber system based on polarization multiplexing to generate an 80 GHz millimeter wave.

We propose a filterless full-duplex radio-over-fiber system based on polarization multiplexing and demonstrate the generation of an 80 GHz millimeter wave using two Mach-Zehnder modulators. By adjusting the polarization direction, we could generate an 80 GHz frequency millimeter-wave signal and restore the original pure light carrier, providing a light source for the uplink. The simulation results show that the 80 GHz millimeter-wave signal was obtained with a 23.48 dB radio-frequency sideband suppression ratio. Furthermore, we showed that the proposed scheme is relatively flexible and free from the limitation of filter fixed bandwidth in addition to being simple and economical.

High-precision millimeter-wave frequency determination through plasmonic photomixing.

We present a technique for high-precision millimeter-wave frequency determination through plasmonic photomixing. Our technique utilizes a plasmonic photomixer pumped by an optical frequency comb with a high-stability millimeter-wave beat frequency. The plasmonic photomixer down-converts the millimeter-wave signal to the radio frequency regime at which high-accuracy frequency counters are available. The precision of this technique is determined by the frequency stability of the optical beat frequency, which can be directly characterized in the presented experimental setup. We demonstrate frequency measurement precision as low as 3.9×10-10 at 95 GHz through plasmonic photomixing without phase-locking the optical frequency comb.

300 GHz wave generation based on a Kerr microresonator frequency comb stabilized to a low noise microwave reference.

In this Letter, we experimentally demonstrate low noise 300 GHz wave generation based on a Kerr microresonator frequency comb operating in the soliton regime. The spectral purity of a 10 GHz GPS-disciplined dielectric resonant oscillator is transferred to the 300 GHz repetition rate frequency of the soliton comb through an optoelectronic phase-locked loop. Two adjacent comb lines beat on a uni-traveling carrier photodiode emitting the 300 GHz millimeter-wave signal into a waveguide. In an out-of-loop measurement, we measure the 300 GHz power spectral density of phase noise to be -88dBc/Hz, -105dBc/Hz at 10 kHz, and 1 MHz Fourier frequency, respectively. Phase-locking error instability reaches 2×10-15 at 1 s averaging time. Such a system provides a promising path to the realization of compact, low power consumption millimeter-wave oscillators with low noise performance for out-of-the-laboratory applications.

Dispersion-tolerant millimeter-wave signal generation by a single modulator

A new and simple scheme of generating millimeter-wave (mm-wave) signal with dispersion tolerance and multi frequency operation is proposed and experimentally demonstrated, which is based on a single polarization multiplexing binary phase-shift keying (BPSK) modulator. In our scheme, a sub-modulator on one branch of the modulator is worked at its quadrature transmission point (QTP) and driven by a clock signal, while the sub-modulator on the other branch is driven by baseband data. Experimental results show that after delivery over 80-km fiber, the bit error rate (BER) of the 6 Gbit/s on–off keying (OOK) modulation mm-wave signal can reach below 10−9. The scheme has the characteristics of dispersion tolerance and can be widely used in long-distance optical communication.

Transmitters for Combined Radio Over a Fiber and Outdoor Millimeter-Wave System at 25 GHz

In the modern wireless networks, millimeter-wave radio-frequency (RF) bands are becoming more attractive as they provide larger bandwidth and higher data rates than the today-used systems operating at frequencies below 6 GHz. In addition, according to the fact that coaxial cables exhibit extremely high attenuation for millimeter-wave RF signals, analog radio over fiber techniques (RoF) form a promising technology for delivering unaltered radio waveform to a remote antenna. This paper experimentally analyzes three types of RoF modulations, namely a directly modulated laser, an electro-absorption modulator, and a Mach-Zehnder Modulator. The primary focus is on the implementation of each RoF transmitter in an RoF system, such as those in 5G networks. The experimental study includes a detailed characterization of an RoF system with a 50-m long outdoor free-space RF channel operating in the frequency band of 25 GHz. Frequency response (S-parameters) and third-order nonlinear distortion are investigated in detail. Tests of EVM performance were conducted using an orthogonal frequency division multiplexing signal modulated with 16-quadrature amplitude modulation (16-QAM) with a long-term evolution signal. It is demonstrated that the transmitters studied can operate under a 13.5% EVM limit given for 16-QAM. Apart from the detailed system performance, the considerable power fluctuations in the 25 GHz free-space RF outdoor channel are reported.

A Compact Millimeter-Wave Frequency Conversion SOP (System on Package) Module Based on LTCC Technology

A novel compact millimeter-wave system on package (SOP) module is proposed in this paper. To achieve high integration, the 14 layers substrate of module is fabricated with low temperature co-fired ceramic (LTCC) technology, which is advanced in incorporating the passive components in multi-layers, thus realizing the signal vertical propagation for the SOP. The designed SOP covering 30~40 GHz is the core module for the millimeter-wave radar system. When the transmitting state of the system is initiated, the introduced SOP will up mix input intermediate frequency (IF) signal with local signal (LO) to millimeter-wave band. And the received millimeter-wave signal will be down-converted to the IF signal during the receiving state. The SOP integrates two frequency conversion channels and 34 monolithic microwave integrated circuit (MMIC) chips, with final size of 35 mm × 48 mm. In the whole working band, transmitting signal has a power range of 10~13 dBm with out-of-band spurious suppression below 50 dBc, while the channel under receiving has a gain of 11~15 dB with automatic gain control (AGC) of 0~50 dB and 1dB-step. The receiving and transmitting isolation between the two channels are both greater than 40 dB, and the T/R isolation in one channel is better than 40 dB.

Broadband Photonic Down-Conversion Preprocessor for ADC With Arcsine Equalization

It is a challenge to convert broadband millimeter-wave signals directly with electronic analog-to-digital converters (ADCs). The photonic down-conversion preprocessor is a promising solution. The arcsine equalization originated from the photonic sampled ADC is applied in the photonic down-conversion preprocessor to leverage the performance. We derive the working principle of the photonic down-conversion system with the arcsine equalization for the first time, and comprehensively investigate the evolution of signal-to-noise ratio (SNR) and signal-to-noise and distortion ratio (SINAD) after the equalization. It shows that the equalization works quite differently in the proposed system, effectively suppressing the nonlinearity from large modulation depth within a periodic frequency range. The common-mode noise is canceled and additional gain of SNR is achieved for any frequency. Factors affecting the performance are discussed in detail, guiding the optimal configuration to exploit the potential of the proposed system under different scenarios. Signals ranging from 31 GHz to 48.9 GHz are digitized via the proposed system with a bandwidth of 10 GHz and an effective number of bits (ENOB) of 5.9. A newly-defined figure of merit (FOM) is proposed to comprehensively and flexibly evaluate bandpass sampling systems and the proposed system displays a favourable performance.

Low complexity QPSK/8QAM millimeter-wave signal generation at D-band without phase pre-coding

In this paper, we propose a D-band quadrature-phase-shift-keying (QPSK) and 8-quadrature-amplitude-modulation (8QAM) millimeter-wave (mm-wave) signal generation based on frequency quintupling by only using a phase modulator (PM). The radio frequency (RF) at 25 GHz is used to drive PM. -3rd sideband and 2nd sideband of PM output is selected to generate 125 GHz mm-wave. We apply star-QPSK constellation distribution which is suitable for frequency quintupling mm-wave generation without pre-coding. For 8QAM, the distribution of constellation can be divided into QPSK set and star-QPSK set. Two sets of constellations will be rotated after photo detector (PD) according to the positive or negative of Bessel function, respectively, so as to realize 8QAM frequency quintupling photonic mm-wave generation without phase pre-coding. Moreover, there is no redundant operation in the generation, transmitting and receiving of mm-wave. The simulation results show that the bit-error-rate (BER) of 2Gbaud QPSK and 8QAM signals are lower than 3.8 ×10−3 in 15-km and 10-km optical fiber transmission, respectively. Compared with previous mm-wave generation schemes without phase pre-coding, the complexity of the proposed scheme is the lowest.

Terahertz electronics: Application of wave propagation and nonlinear processes

We review the recent advances on the implementation of electronic circuits that operate in the millimeter-wave (30–300 GHz) and terahertz (300–3000 GHz) frequency ranges. The focus of this article is on nonlinear phenomena in electronics. The different implementations of nonlinear circuits for the sake of millimeter-wave and terahertz signal generation are studied in this paper. The challenges of signal generation are examined and the benefits and limitations of different schemes of signal generation are discussed. It is shown that nonlinear devices such as electronic transistors exhibit major advantages enabling realization of low-cost and portable circuits for the emerging applications in these frequency ranges. We also review linear and nonlinear design methodologies employing the properties of electromagnetic waves. The electronic systems designed based on the presented ideas are shown to push the previously unbeatable limits of operation in millimeter-wave and terahertz frequency ranges. A discussion on remaining challenges and future directions concludes the paper.

MmASL

Home assistant devices such as Amazon Echo and Google Home have become tremendously popular in the last couple of years. However, due to their voice-controlled functionality, these devices are not accessible to Deaf and Hard-of-Hearing (DHH) people. Given that over half a million people in the United States communicate using American Sign Language (ASL), there is a need of a home assistant system that can recognize ASL. The objective of this work is to design a home assistant system for DHH users (referred to as mmASL) that can perform ASL recognition using 60 GHz millimeter-wave wireless signals. mmASL has two important components. First, it can perform reliable wake-word detection using spatial spectrograms. Second, using a scalable and extensible multi-task deep learning model, mmASL can learn the phonological properties of ASL signs and use them to accurately recognize the ASL signs. We implement mmASL on 60 GHz software radio platform with phased array, and evaluate it using a large-scale data collection from 15 signers, 50 ASL signs and over 12K sign instances. We show that mmASL is tolerant to the presence of other interfering users and their activities, change of environment and different user positions. We compare mmASL with a well-studied Kinect and RGB camera based ASL recognition systems, and find that it can achieve a comparable performance (87% average accuracy of sign recognition), validating the feasibility of using 60 GHz mmWave system for ASL sign recognition.

Photonic generation of millimeter-wave signal through frequency 12-tupling using two cascaded dual-parallel polarization modulators

In this paper, filterless photonic generation of millimeter-wave (mm-wave) signal through frequency 12-tupling via two cascaded dual-parallel polarization modulators (DP-PolMs) is proposed. The principle of operation of the proposed system is theoretically analysed and verified by computer simulation. From the theoretical analysis, the frequency 12-tupling mm-wave signal is shown to be generated by properly adjusting the modulation indices of PolMs, polarization directions of the modulated optical signals, and the phases of the RF drive signals applied to the DP-PolM. The simulation results show that the generated frequency 12-tupling optical mm-wave has high purity with an optical sideband suppression ratio (OSSR) of 25.1 dB and radio frequency spurious suppression ratio (RFSSR) of 19.1 dB. Theoretically obtained results are in good agreement with the simulation results. Furthermore, taking into consideration the practical implementation, the influence of non-ideal parameters on the OSSR and RFSSR are analyzed.

Hybrid precoding design in multiuser large‐scale antenna systems under correlated fading

Millimetre wave (mmWave) signal is promising for the challenge of bandwidth shortage and canmotivate the research on large-scale antenna arrays. In this paper, the authorsinvestigate the hybrid precoding design that combines with a radio frequency(RF) precoder and a digital precoder for multi-user multiple-input single-output(MU-MISO) systems with large-scale antenna arrays. In practical large-scaleantenna array systems, the small antenna spacing and the properties of ascattering environment can create a correlation between channel coefficients forseparated receive units. Such correlation prejudices the performance ofmulti-user systems. This study proposes two approaches to reduce the channelcorrelation by the hybrid precoding structure. The first approach selects somevectors with the smallest influence with each other from all array responsevectors to design an angular-based RF precoder. The second approach optimisesthe singular values characteristic of the virtual channel matrix before digitalprocessing for the RF precoder. Then, the MU-MISO baseband precoding isimplemented by reduced RF chains. Numerical results show that they havedifferent performance depending on the environment. The first can achieve betterperformance when the channel correlation is not too high, while the second ismore effective when the channel realisation is terribly ill-conditioned, especially for higher signal-noise ratio (SNR).

A Phase Calibration Method for Millimeter-Wave Up-Converter Using Electro-Optic Sampling

A phase measurement method using electro-optic sampling of millimeter-wave 4-tone signals is presented for phase calibration of frequency converters. Phase lock loop (PLL) circuits with high comparison frequencies of 2.6 and 15 GHz are used to synchronize the millimeter-wave 4-tone signal with a short optical pulse for low-jitter equivalent time sampling. A 4-tone separate detection method using a lock-in amplifier is applied for precise phase measurement with high frequency resolution. In addition, a phase-correction scheme using 4-tone signals with different frequency spacings is introduced for wideband phase calibration. The error vector magnitude (EVM) of the 10.2-Gbaud quadrature phase shift keying (QPSK) signal with 292.5-GHz carrier frequency is evaluated to confirm the effectiveness of the wideband phase calibration.