Quadrature Signals Research Articles

A 0.023–12 GHz ultra-wideband frequency synthesizer with FOMT of −251.8 dB

A fully integrated ultra-wideband fractional-N frequency synthesizer is presented in this paper. Ultra-wideband quadrature signals can be generated by an octave-wide fractional-N phase-locked loop (PLL) and an ultra-wideband local oscillator (LO) signal generator. An optimized dual-core voltage-controlled oscillator (VCO) is employed to maintain relatively constant loop parameters in the octave-wide operating range, while a negative-capacitance VCO (NC–VCO) is proposed to solve the frequency gap problem and enhance the design freedom of the wideband VCO. Moreover, a wide-range programmable multi-modulus divider (PMMD) with seamless switching and fractional division resolution is proposed for error-free division operation and quantization noise compensation in the fractional-N mode, respectively. Power-efficient design is mainly achieved by the presented hybrid LO generator with optimized divider topologies for different frequency ranges. Fabricated in a 55 nm CMOS process, 0.023–12 GHz continuous quadrature LO signals can be generated by the proposed frequency synthesizer which occupies an active area of 0.55 mm2 and consumes 75–104 mW from a 1.2 V supply. The measured phase noise is −108.1 dBc/Hz at 1 MHz offset from a 12 GHz carrier, and the I/Q phase error is less than 2.7° with FOMT of −251.8 dB.

Гомодинный квадратурный интерферометр перемещений. Эксперимент

In the previous work, the results of mathematical modeling of the optical scheme of a single-pass homodyne interferometer of displacements with the quadrature principle of phase registration are presented. The interferometer is built according to the Michelson scheme, and polarizing optical elements are used to obtain quadrature signals. The interferometer is supposed to be used as part of a new national standard of the kilogram based on watt balance method for precision measurements of the displacement and speed of the coil in the vertical direction. In this paper, experimental studies of the operation of a model of a homodyne quadrature displacement interferometer are presented. In this work, instead of a polarization beam splitter, a conventional (non-polarization) beam splitter and two polarizers are used in the optical scheme of a homodyne interferometer in the registration units. This added additional degrees of freedom when aligning optical channels for recording interference channels and made it possible to achieve the required signal shift by 90° with an accuracy of 0.1°. As a result, a displacement measurement error of 02. nm was experimentally achieved. Generalized expressions are obtained for quadrature signals for arbitrary azimuths of polarizers in three channels of recording interference signals. An assessment of the accuracy of displacement measurements using a quadrature homodyne interferometer was carried out and it was obtained that the expanded uncertainty of such measurements does not exceed 0.3 nm.

Novel Meteor Observations Using FM Radio Broadcast Over Gadanki, India

A novel GNU radio-based software-defined radio receiver using USRP (universal serial radio peripheral) front end and YAGI antenna is developed to record meteor echoes in passive mode using FM broadcast. Pilot observations are made for four days in August-September 2020 to record FM signals at 103.2MHz, 104MHz, and 107.5 MHz with a varying sample rate of 8 KHz and 200 KHz. The in-phase and quadrature signals are processed to obtain the amplitude and phase of the received signals for identification of the meteor echoes. A new algorithm is developed to automatically detect the echoes using a normalized amplitude threshold and a minimum temporal separation between two echoes. Overdense meteor echoes with a plateau-like amplitude response are found using a ratio test and remaining echoes are rejected. Thus, the system is able to detect almost all types of meteor echoes reported earlier. Notably, signatures of fragmentation and background wind are also observed in form of different phase patterns. Histogram of the meteor counts shows a peak for shorter durations indicating larger populations of the smaller size of meteoroids. The log-log plot of the meteor duration versus count is found to exhibit a characteristic transition of the slope. An empirical estimate of the height of the echoes is obtained. The echoes show micro-meteoroid populations which may depend upon the transmitting-receiving setup and the geometry. Hence, an inexpensive, low-power, portable, passive and automated meteor detection system is demonstrated which can be highly useful for understanding the meteor phenomena and estimation of atmospheric parameters.

A V-Band Integrated Receiver Front-End Based on 0.15 μm GaAs pHEMT Process for Passive Millimeter-Wave Imaging

The design, analysis, implementation and measurement of an integrated V-band receiver front-end based on 0.15 μm GaAs pHEMT process are presented in this paper. The front-end chip uses the super-heterodyne topology which consists of a low noise amplifier, an image reject mixer, and a multiply-by-four (×4) LO chain. In order to minimize the power consumed by LO chain, an active single-ended mixer is designed which requires extremely low LO power of -5 dBm. Meanwhile, the effect of signal coupling in the integrated chip is analyzed and solutions are proposed. By introducing appropriate filters into the circuit and optimizing the overall layout, the imbalance of in-phase and quadrature signals caused by unwanted coupling can be effectively mitigated, thus enhancing the image rejection of the chip. Probe and module tests are applied to the receiver front-end, and the measurement results reveal that the chip achieves -3 ± 0.7 dB conversion gain, 7 dB noise figure and more than 25 dB image rejection ratio in the RF frequency range of 52-56 GHz. Only one supply voltage of 3 V is required for the chip, and total power consumption is 312 mW. Moreover, with a continuously adjustable phase control of 360° and very broadband IF characteristics, the front-end chip is suitable for passive millimeter-wave imaging applications.

АНАЛИЗ ИСПОЛЬЗОВАНИЯ ФИЛЬТРА КАЛМАНА В ПРОЦЕДУРЕ ДЕТЕКТИРОВАНИЯ СИГНАЛА В СИСТЕМЕ С MIMO И ПРИЕМНИКОМ ПРЯМОГО ПРЕОБРАЗОВАНИЯ

Introduction: The procedure for detecting a quadrature amplitude modulation (QAM) signal in a communication system with multiple transmitting and receiving antennas (MIMO) is considered, which consists of two stages: obtaining soft solutions using the recurrent Kalman filtering algorithm, finding hard solutions by criterion of minimum distance between soft decision vectors and possible information symbols on each receiving antenna. The Kalman algorithm evaluates symbols at i-th time point in iterations. A comparison is made of noise immunity of QAM signal reception obtained using the Zero Forcing methods, the minimum mean square error (RMS), and recurrent Kalman procedure. Signal processing takes place under channel conditions with Rayleigh fading and Doppler spread spectrum. Cases are considered when the channel matrix is known exactly and when it is estimated by least squares method (LSM) using a first-order polynomial approximation for channel matrix elements. The channel matrix takes into account not only signal distortions due to the propagation medium, but also distortions obtained in the direct conversion receiver, such as amplitude and phase imbalance between signal quadratures, frequency shift due to non-ideal demodulation procedure, as well as DC drift. Result: The computational complexity of the detector based on Kalman algorithm is analyzede.

Spectrum Monitoring Based on Error Vector Magnitude and Received Signal Strength Indicator

Wireless communication systems may suffer from interferences caused by other emitters. Modern research and development on these systems is focusing on a more dynamic spectrum usage in order to mitigate or avoid such interferences. Nevertheless, this adaptability requires detecting them by either spectrum sensing or spectrum monitoring. While spectrum sensing observes the electromagnetic spectrum regarding the presence of signals, spectrum monitoring exploits the reception metrics during a communication for detecting interferences. This paper proposes a spectrum-monitoring algorithm that is making use of the error vector magnitude of the received signals. As a high error vector magnitude may indicate both an interference and a low signal power, the received signal strength indicator is used to distinguish these cases. The primary user presence is identified based on linear classification by the help of support-vector machines, which take the error vector magnitude, the received signal strength indicator, and the modulation order as input. The success of the spectrum-monitoring algorithm is demonstrated based on simulations of quadrature amplitude modulated signals.

Dual-Band Direct Conversion Receiver With Additive Mixing Architecture

A dual-band direct conversion receiver based on additive mixing architecture for low-cost and multi-mode wireless communication systems is proposed. The proposed receiver consists of two active four-port junctions for additive mixing and one-stage dual-band polyphase filter for quadrature LO signal generation. Each four-port junction is fabricated with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.18~\mu \text{m}$ </tex-math></inline-formula> CMOS technology and configured by an active balun, two buffer amplifiers, two active combiners and two power detectors. The proposed polyphase filter is implemented using type-I architecture adopting one-stage and R-LC resonance type for low power and dual-band operation. The phase and amplitude calibration schemes are also integrated to effectively correct I/Q mismatch within the proposed architecture. The calibration ranges for the phase and amplitude mismatches show 8° and 14 dB, respectively. The validity of the proposed receiver based on additive mixing method is successfully demonstrated by demodulating 16-QAM signals with 40 Mbps at the dual band of 900 MHz and 2.4 GHz.

Distributed Implementation of Control Barrier Functions for Multi-agent Systems

In this letter, we propose a distributed implementation framework for control barrier functions induced quadratic programs for multi-agent systems. The quadratic program aims at minimally modifying nominal local controllers, which relate to the underlying system tasks, while always respecting a single coupling constraint which relates to system safety. Unlike previous implementations, no approximation or pre-allocation of the coupling constraint over the agents is needed. Instead, to solve the quadratic problem exactly, an auxiliary variable is assigned to each agent and then locally updated and transmitted among agents. The proposed distributed implementation ensures that the control barrier function constraint is enforced at every time instant, and the optimal to the quadratic program control signal is achieved in finite time. The efficacy of our method is demonstrated through two numerical examples.

Observer-Based Quadrature Signal Generator for UPQC in a Single-Phase Distribution System

This paper presents a control algorithm for generation of reference voltage and current based on Observerbased QSG (Quadrature Signal Generator) for UPQC (Unified Power Quality Conditioner) in a Single-Phase Distribution System. The proposed UPQC is a combination of DSTATCOM and DVR used for load and source compensation such as voltage sag and swell, voltage and current harmonics etc. The proposed control algorithm is capable of generating reference signals from the distorted voltages and currents. In this paper, an improved OQSGbased PLL (Phase-Locked Loop) is utilized over OQSG to enable and operate with increased bandwidths that will improve the dynamic response, tracking accuracy and faster detection of reference signal under all varying load and grid conditions. The control algorithm is tested and evaluated using MATLAB / Simulink.

A New Approach to Fourth-Order Quadrature Signal Generation for a Fast and Noise-Free PLL Output Under Non-Ideal Grid Voltage Conditions

Dual quadrature signal generator (QSG) along with a positive sequence calculator (PSC) eliminates the negative sequence components from unbalanced grid voltages. The QSGs also offer attenuation to harmonics and dc-offset present in the sensed input voltages. Fourth-order QSGs offer superior harmonic attenuation with complete dc-offset rejection compared to lower-order QSGs. Therefore, dual fourth-order QSG + PSC is an apt solution for pre-filtering in phase-locked loops (PLLs) under non-ideal grid voltage conditions. Two fourth-order QSGs (FO-QSGs) namely, second-order SOGI-QSG (SO-SOGI-QSG) and cascaded SOGI-QSG have been proposed in the literature. Parameter selection for these FO-QSGs to achieve a faster dynamic response is challenging due to the higher order of the transfer functions. The response time of the QSGs directly impact the response time of the PLL. This paper proposes a new approach to fourth-order quadrature signal generation that achieves a lower settling time for the QSG compared to existing FO-QSGs. The proposed method achieves a faster response time by setting the QSG parameters using equations that directly relate to the system settling time. Using the proposed method, the QSG settles within 25.4 ms while maintaining a low total harmonic distortion.

3 × 3 MIMO Fiber–Wireless System in W-Band With WDM/PDM RoF Transmission Capability

We propose and demonstrate a 3 × 3 full multiple-input multiple-output (MIMO) fiber–wireless system in the W-band with wavelength-division multiplexing (WDM) and polarization-division multiplexing (PDM) radio-over-fiber (RoF) transmission capability. The system is realized using two highly stable RoF links based on the optical self-heterodyne method and PDM transmission in one of the RoF links. We experimentally demonstrate and confirm satisfactory performances for a 3 × 3 MIMO offset quadrature amplitude modulation-based filter-bank multicarrier signal. Total capacities of approximately 110 and 132 Gb/s, corresponding to spectral efficiencies of approximately 8.5 and 10.2 bits/s/Hz, respectively, are achieved for the system using antennas placed in the same and alternately different polarizations, respectively. The system is applicable to WDM and combined WDM/PDM RoF transmissions. It provides a scalable solution for facilitating large-scale MIMO signal transportation and can be a promising solution for future mobile transport and radio access networks in high-frequency bands.

Programmable Universal Filter and Quadrature Oscillator Using Single Output Operational Transconductance Amplifiers

This paper presents a new programmable universal filter and quadrature oscillator based on single output operational transconductance amplifiers (OTAs). The proposed universal filter and quadrature oscillator can be achieved into single topology by programming using analog switches. When the circuit programs as a universal filter, it can realize low-pass, high-pass, band-pass, band-stop and all-pass filters with orthogonal and electronic controls of the natural frequency and the quality factor. When the circuit programs as a quadrature oscillator, it provides three-phase quadrature output signals which the condition of oscillation and the frequency of oscillation can be controlled orthogonally and electronically. The proposed structure can be realized based on single output OTAs which is easily implemented both commercially available integrated circuits as OTAs and complementary metal-oxide semiconductor and bipolar junction transistor OTA as IC forms. The performance of the proposed circuit is investigated by SPICE simulation using standard 0.18 μm CMOS process and experiment test using LM13600 discrete component integrated circuit as OTAs is used to confirm the workability of the new circuit.

28–38-GHz 6-bit Compact Passive Phase Shifter in 130-nm CMOS

In this letter, a highly compact, bidirectional, wideband 6-bit resolution passive phase shifter (PS) is presented in low-cost 130-nm CMOS technology. A compact Lange differential hybrid is designed in this letter to provide quadrature signals from the input. The compact Lange hybrid is followed by a switching matrix that generates weighted sums of the quadrature signals to cover 360° and additional controlled loss using single pole single throw (SPST) switches. The matrix consists of 12 transistors, each of which is controlled by a three-level gate voltage (0, 0.6, and 1.2 V) providing higher resolution in phase shifts. The chip achieves the state-of-the-art performance with 10-dB insertion loss across 28–38 GHz. The chip also achieves an rms gain error of 0.6 dB and an rms phase error of 3° in the bandwidth, consuming no dc power and only 0.15 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> including baluns.

High Power RF Discharge Detection Technique Based on the In-Phase and Quadrature Signals

High power radio frequency (RF) breakdown testing is a subject of great relevance in the space industry, due to the increasing need of higher transmission power and smaller devices. This work presents a novel RF breakdown detection system, which monitors the same parameters as the microwave nulling system but with several advantages. Where microwave nulling--a de facto standard in RF breakdown testing--is narrowband and requires continuous tuning to keep its sensitivity, the proposed technique is broadband and maintains its performance for any RF signal. On top of that, defining the detection threshold is cumbersome due to the lack of an international standardized criterion. Small responses may appear in the detection system during the test and, sometimes, it is not possible to determine if these are an actual RF breakdown or random noise. This new detection system uses a larger analysis bandwidth, thus reducing the cases in which a small response is difficult to be classified. The proposed detection method represents a major step forward in high power testing as it runs without human intervention, warning the operator or decreasing the RF power automatically much faster than any human operator.

Impacts of Quadrature Signal Generation-Based PLLs on Low-Frequency Oscillation in an Electric Railway System

The low-frequency oscillation (LFO) issue has occurred frequently in single-phase electric train and traction network interactive systems (hereinafter train-network systems). On a single-phase electric train, the quadrature signal generation-based phase-locked loop (QSG-PLL) has been widely used to achieve unit power factor operation. The bandwidth of the single-phase PLL is close to the frequency of the LFO, but its impacts on the LFO are not considered fully in previous works. In this article, three typical QSG-PLLs are studied in depth, and their unified model is derived in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> frame. Furthermore, the impacts of the QSG-PLL structure and parameters on the LFO are revealed. The analysis results indicate that the QSG part plays an important role in the LFO analysis, but the parameters of the PLL part have slight impacts on the train’s impedance under the low-power operation mode. Three different QSGs can all be regarded as providing a second-order low-pass filter (LPF) to generate the virtual <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> component in the single-phase system. The higher damping ratio of the second-order LPF can increase the magnitude of the train’s impedance, which is beneficial to enhance the stability of the train-network system. Finally, experimental results via hardware in loop (HIL) are employed to verify the correctness of the theoretical analysis results.

A 24-GHz Fully Integrated CMOS Transceiver for FMCW Radar Applications

A 24-GHz fully integrated frequency-modulated continuous wave (FMCW) direct conversion transceiver, implemented in a 55-nm low-power CMOS technology with a maximum <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\mathrm {T}}$ </tex-math></inline-formula> of 190 GHz in typical operating conditions and packaged in a 5-mm <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> 5-mm 32-lead quad-flat no-leads (QFN) package, is presented in this article. The single-chip transceiver uses a single 2.5-V supply while all the core circuits are powered by integrated regulators. The complex low-noise transductor in the receiver uses a quadrature hybrid to generate quadrature signals in the receiving front-end. The analog signal processing circuits including high-pass filters, low-pass filters, and programmable amplifiers are implemented following the receiver front-end circuitry. The FMCW signals are generated by an on-chip 24-GHz fractional-N frequency synthesizer. The synthesizer is completely integrated with the transceiver and provides built-in digital frequency modulation to generate chirping signals for the down-conversion local oscillator (LO) and the transmitted signals. The transmitter is composed of a balanced class-AB power amplifier driven by the FMCW signals from the frequency synthesizer.

High-Stability PGC Demodulation Algorithm Based On a Reference Fiber-Optic Interferometer With Insensitivity to Phase Modulation Depth

An ameliorated phase generated carrier demodulation algorithm based on a reference interferometer is proposed. It is theoretically analyzed, numerically simulated, and experimentally verified in this paper. The method of matching the amplitude of the quadrature signal in the reference interferometer algorithm eliminates the harmonic distortion caused by modulation depth fluctuations, suppresses system noise, and improves system stability. In experiments, where the sensed signal amplitude is 0.68 rad, the frequency is 1 kHz, and the modulation depth ranges from 1.5 to 3.5 rad, the ameliorated algorithm has SINAD that reaches 24.5 dB, which is an average improvement of 7.9 dB over the PGC-DCM algorithm based on a reference interferometer and an average improvement of 3 dB over the PGC-Arctan algorithm based on a reference interferometer. The ameliorated algorithm achieves a THD of 0.451&#x0025;, which consistently maintains the best level of the traditional PGC algorithm based on a reference interferometer. The method provides an effective reference for signal processing in practical applications of fiber-optic sensors.

2.4 GHz Low-power Receiver Front-end Employing I/Q Mixer with Current-reused Quadrature Transconductor for Bluetooth Low Energy Applications

In this paper, a 2.4 GHz Bluetooth low energy (BLE) receiver front-end with a new inphase/quadrature (I/Q) down-conversion active mixer employing a current-reused quadrature transconductor is presented for low-power low-voltage Internet of Things applications. In the proposed I/Q mixer, the current-bleeding circuit, whose main role is to reduce the flicker noise in the switching stage, enhances the overall transconductance and provides quadrature signals with the main quadrature transconductor. Consequently, it improves the conversion gain and noise figure of the mixer without additional power consumption. The proposed BLE receiver front-end consists of a current-reused push-pull low-noise amplifier and an I/Q mixer with a current-reused quadrature transconductor. Simulated in a 65 nm CMOS process, the designed receiver front-end achieves a noise figure of 3.3 dB, conversion gain of 37.6 dB, and input-referred third-order intercept point of -22.73 dBm. It draws a bias current of 1 mA from a nominal supply voltage of 1 V. The active die area is 0.5 mm².

Elimination of parasitic interference effect in fiber-optic external sinusoidal phase-modulating interferometer based on Kalman filter

The fiber-optic external sinusoidal phase-modulating interferometer (ESPMI) is sensitive, accurate, and robust. However, parasitic interference hinders further improvement of its precision, and reduces its adaptability to measurement targets with different characteristics. In this paper, we analyzed the mathematical model of parasitic interference, and proposed a Kalman filter-based method to eliminate the parasitic interference effect in the ESPMI. This method works by filtering out the time-varying offsets in quadrature signals brought by the parasitic interference. Simulations and experiments were conducted to verify the effectiveness of the proposal. The experimental results showed that our proposal had great parasitic interference effect elimination ability. Compared with existing schemes, our method is highly accurate and low-cost with no loss in interferometric range, thus having catalytic effect on the application of ESPMI in related fields.

Seamless Fiber–Wireless System in W-Band Using Optical Phase Modulation and Self-Homodyne Receiver

We propose and demonstrate a seamless fiber–wireless system in the W-band using a simple transmitter, antenna site, and radio receiver. The transmitter utilizes an optical phase modulator instead of an optical in-phase/quadrature modulator for data modulation. A high-output optical-to-radio converter is fabricated and used for radio signal generation at the antenna site. The receiver employs a self-homodyne detector (SHD) that does not require a separate local oscillator source to receive and down-convert the signal to the microwave band. For a proof-of-concept demonstration, we successfully transmitted a high-order quadrature amplitude modulation orthogonal frequency-division multiplexing signal with a bandwidth of up to 4 GHz over the system. The performance of the signal transmission over the system using an envelope detector was also evaluated. Owing to its better received sensitivity, the SHD receiver exhibited better performance. The proposed system can facilitate the deployment of seamless access networks in high-frequency bands in future mobile networks.