Search Results (18)

This article is devoted to the investigation of synchronization noise immunity in quadrature chaos shift keying (QCSK) communication systems and its profound impact on system performance. The study focuses on Colpitts and Vilnius chaos oscillators in different synchronization configurations, and the reliability of the system in the particular configuration is assessed using the bit error rate (BER) estimation. The research considers synchronization imbalances and demonstrates their effect on the accuracy of data detection and overall transmission stability. The article proposes an approach for optimal bit detection in the case of imbalanced synchronization and correlated chaotic signals in data transmission. The study practically shows the importance of the proposed decision-making technique, revealing that certain adjustments can significantly enhance system noise resilience. Full article

In this paper, a novel Colpitts voltage-controlled oscillator (VCO) with low phase noise and an octave frequency tuning range is presented. To achieve low phase noise and a wide tuning range concurrently, the designed VCO employs quad-core-coupled structures, series resonators, dual-mode-coupled inductors, and push–push structures. The quad-core-coupled structures are used for phase noise improvement. The presented series resonators effectively expand the tuning range while reducing phase noise deterioration from amplitude-to-phase modulation (AM/PM) conversion. The dual-mode operation based on coupled inductors and quad-core structures further expands the tuning range. In addition, the adopted push–push structure increases the output frequency. Designed in a 180 nm SiGe BiCMOS process, the proposed Colpitts VCO operates from 7.2 to 14.5 GHz with an octave tuning range of 67.3%. The phase noise ranges from −131.4 to −121.8 dBc/Hz with a peak figure-of-merit (FoM) of 183.0 dBc/Hz and figure-of-merit-tuning (FoM_T) of 199.5 dBc/Hz at a 1 MHz offset. The proposed VCO exhibits superior performance in phase noise and tuning range and achieves an octave tuning range for the first time in Colpitts VCOs. Full article

This manuscript presents an experimental study of Quadrature Chaos Shift Keying (QCSK) as a means to tighten the physical layer security of Internet of Things (IoT) communication. Our study examines the characteristics and operational aspects of chaos oscillators, prioritizing low-power functionality, resilient chaotic oscillations, and resistance to parameter variations and noise. This study emphasizes the key role of chaos oscillators in enhancing IoT security, showcasing their potential to ensure data integrity. The findings elucidate the dynamics and synchronization stability of the selected oscillators, providing insights into their suitability for secure communication systems. This comprehensive analysis contributes to advancing secure communication methodologies for the expanding landscape of wireless sensor networks in the Internet of Things, underscoring the significance of chaos oscillators in ensuring robust and secure data transmission. Full article

Differential equations are useful mathematical tools for solving complex problems. Differential equations include ordinary and partial differential equations. Nonlinear equations can express the nonlinear relationship between dependent and independent variables. The nonlinear second-order neutral differential equations studied in this paper are a class of quadratic differentiable equations that include delay terms. According to the t-value interval in the differential equation function, a basis is needed for selecting the initial values of the differential equations. The initial value of the differential equation is calculated with the initial value calculation formula, and the existence of the solution of the nonlinear second-order neutral differential equation is determined using the condensation mapping fixed-point theorem. Thus, the oscillation analysis of nonlinear differential equations is realized. The experimental results indicate that the nonlinear neutral differential equation can analyze the oscillation behavior of the circuit in the Colpitts oscillator by constructing a solution equation for the oscillation frequency and optimizing the circuit design. It provides a more accurate control for practical applications. Full article

This paper investigates a simple memristor emulator consisting of a diode bridge and a capacitor. It exhibits pinched hysteresis loops, and what is more striking is the higher frequency, as it operates up to greater than 5 MHz. Based on the proposed memristor, a higher-frequency Colpitts circuit was established. According to the mathematical model of the system, the system only possesses one unstable equilibrium point. Period doubling bifurcation, reverse periodic doubling bifurcation, different types of periodic and chaotic orbits, transient chaos, coexisting bifurcations and offset boosting are depicted. More interestingly, it has coexisting multiple attractors with different topologies, such as a chaotic attractor accompanied with periodic orbits, period-1 orbits with bicuspid structure and periodic-2 orbits with tridentate structure. Moreover, a hardware circuit using discrete components was fabricated and experimental measurements were consistent with the MATLAB numerical results, further confirming the real feasibility of the proposed circuit. Full article

This paper demonstrates an on–off keying (OOK) super-regenerative quenching transmitter operating in 402–405 MHz MICs band applications. To reduce power consumption, the transmitter is controlled by a novel digital quenching signal controller that generates a digital control signal to start transmitter operation when a baseband signal is input to the transmitter. The digital signal controller consists of an envelope detector, a comparator, and a quench timer designed using a state machine to synchronize the operation between the digital controller and the input baseband signal. The transmitter consists of a Colpitts oscillator operating in double operating frequency followed by a frequency divider by 2; this configuration reduces system area and improves phase noise and signal spectrum. The proposed transmitter is implemented using UMC 130 nm CMOS technology and a 1.2 V supply. Simulation shows that the proposed transmitter can meet MICS band mask specifications with data rates up to 1 Mbps and total power dissipation of 537 uW. Full article

In this paper, we show that an additional inductor–capacitor–inductor filter can increase the oscillation amplitude of the enhanced swing Colpitts oscillator (ESCO), and call this topology the more enhanced swing Colpitts oscillator (mESCO). When it is connected with a rectifier, the DC–DC boost conversion ratio can be increased, especially for low-voltage sensor ICs or energy harvesting. This paper focuses on the electrical characteristics of mESCO. The oscillation frequency was modeled as a function of the circuit parameters of mESCO. The common gate voltage gain (A_CG), defined by the ratio of the drain voltage amplitude to the source voltage amplitude of the switching MOSFET of mESCO, was also modeled under the assumption that all the circuit elements are ideal. The model was validated with a SPICE simulation. For A_CG < 1.5, the model was in good agreement with the SPICE results within 10%. In addition, the drain voltage amplitude v_da was modeled by assuming that the average transconductance of the MOSFET in a half cycle is null when the long-channel Shockley model is used. v_da needs to be sufficiently high to have a large DC–DC boost conversion ratio. The model can predict the tendency that v_da increases as A_CG approaches unity. We found that the voltage difference of the drain voltage amplitude to the source voltage amplitude is a constant even when the circuit parameters, and thereby A_CG are varied. Full article

An inductively powered passive transmitter architecture for wireless sensornodes is presented in this paper. The intended applications are inductively powered internally illuminated photoreactors. The application range of photoreactors is wide. They are used, e.g., for microalgae cultivation or for photochemistry, just to name two important fields of use. The inductive powering system used to transmit energy to the wireless internal illumination system is to be additionally used to supply the here presented transmitter. The aim of expanding the named internal illuminated photoreactors with wireless sensors is to obtain a better insight into the processes inside it. This will be achieved by measuring essential parameters such as, e.g., the temperature, pH value, or gas concentrations of the medium inside the reactor, which for algal cultivation would be water. Due to the passive architecture of the transmitter electronics, there is no need for batteries, and therefore, no temporal limitations in their operational cycle are given. The data transmission is also implemented using the inductive layer in the low frequency range. The data transmitting coil and the energy receive coil are implemented as one and the same coil in order to avoid interference and unwanted couplings between them, and in order to save weight and space. Additionally, the transmitter works in a two-step alternating cycle: the energy harvesting step, followed by the data transmission step. The measured values are sent using on-off keying. Therefore, a Colpitts oscillator is switched on and off. The circuit is simulated using SPICE simulations and consequentially implemented as a prototype in order to perform practical analyses and measurements. The feasibility of our transmitter is therefore shown with the performed circuit simulations, and practically, by testing our prototype on an internal illuminated laboratory scaled photoreactor. Full article

In laparoscopic surgery for colorectal and gastric cancer, it is difficult to locate the tumor in the cavity for excision. Tumors in the colon or stomach are blocked by mucous membranes; thus, the view from the cavity is obscured. Therefore, to determine the location of the tumor, a marker can be installed around the tumor and the location of the tumor can be found using a sensor. Until now, most of the clip-detectors that have been developed can detect the location of tumors for either colorectal or gastric cancer. The research on the development of a detector that can detect the location of tumors for both colorectal and gastric cancer, is insufficient. Most detectors for tumor location determination are devised using a magnet by connecting a wire to a clip. In this method, the position of the magnet moves along the length of the wire. Therefore, it is difficult for the detector to detect the exact location of the tumor. Based on this method, this study designs a clip maker to determine the location of a tumor and a detector that can detect the clip. The clip and the sensing element are directly connected. The clip is developed using ferrite and coil to generate a magnetic field induced by an eddy current in the metal (clip), and the detector is designed using the Colpitts oscillator to induce a magnetic field. After installing the prepared clip at the tumor location, the detector is used to detect the clip, and accordingly, the location of the tumor can be identified using the detector. To test the performance of the clip and detector, we conducted animal experiments. In the course of the animal experiment, four clips were installed in the colon and stomach, and we succeeded in detecting all the clips. Because the clip-detector is used to locate the tumor during laparoscopic surgery, an endoscope must be used. Therefore, it is predicted that the demand for laparoscopic surgery and endoscopic medical industry will increase because of the clip-detector. Full article

During laparoscopic surgery for colorectal or gastric cancers, locating the tumor for excision is difficult owing to it being obscured by mucous membranes. Therefore, a clip can be installed around the tumor, which can be located using a sensor. Most of the clip–detectors developed thus far can only detect tumors in either the colon or stomach and require a wire to connect the clip and detector. This study designs a clip and detector that can locate a tumor in the stomach and colon. The clip contains a neodymium magnet that generates a magnetic field, and the detector includes a Colpitts oscillator that allows magnetic coupling of the clip and detector. After installing the prepared clip at the tumor location, the detector is used to locate the clip. To test the clip and detector, we conducted animal experiments, during which four clips were installed in the colon and stomach of a mini pig. We succeeded in locating the clips within 2.17 and 3.14 s in the stomach and colon, respectively, which were shorter than the detection times reported in previous studies. The demand for laparoscopic surgery and endoscopes is predicted to increase owing to this method. Full article

This paper examines the suitability of selected configurations of ultra-low voltage (ULV) oscillators as starters for a voltage boost converter to harvest energy from a thermoelectric generator (TEG). Important properties of particularly promising configurations, suitable for on-chip implementation are compared. On this basis, an improved oscillator with a low startup voltage and a high output voltage swing is proposed. The applicability of n-channel native MOS transistors with negative or near-zero threshold voltage in ULV oscillators is analyzed. The results demonstrate that a near-zero threshold voltage transistor operating in the weak inversion region is most advantageous for the considered application. The obtained results were used as a reference for design of a boost converter starter intended for integration in 180-nm CMOS X-FAB technology. In the selected technology, the most suitable transistor available with a negative threshold voltage was used. Despite using a transistor with a negative threshold voltage, a low startup voltage of 29 mV, a power consumption of 70 µW, and power conversion efficiency of about 1.5% were achieved. A great advantage of the proposed starter is that it eliminates a multistage charge pump necessary to obtain a voltage of sufficient value to supply the boost converter control circuit. Full article

Growing importance of wireless communication systems forces reduction of power consumption of the designed integrated circuits. The paper focuses on minimization of power consumption in a digitally controlled oscillator (DCO) that can be employed as oscillator in GPS/Galileo receiver. The new hybrid architecture of DCO combines good phase noise performance of a Colpitts oscillator and relaxed startup conditions of a cross-coupled differential pair oscillator. The proposed new DCO generates a quadrature signal in a current reused frequency divider. Such solution allows of the dissipated power to be reduced. The DCO has been implemented in 110 nm CMOS technology. It generates output signal in frequency range from 1.52 GHz to 1.6 GHz and consumes 1.1 mW from 1.5 V supply voltage. The measured phase noise equals −116 dBc/Hz at 1 MHz offset from 1.575 GHz output signal. Full article

A miniature sensor and control system is developed to facilitate human eye ciliary muscle movement detection and to drive the corresponding liquid crystal based lens to create an autofocusing lens for cataract patients. The movement of the ciliary muscle is detected by a marker that detunes a Colpitts oscillator. The change in oscillation frequency is measured by the implantable circuit and sent to an external control unit. This external unit calculates the corresponding focal length and returns corresponding commands to the implantable system to change differential signal driving the lens. The system is built with state-of-the-art Commercial-Off-The-Shelf (C.O.T.S.) components around a miniature ultra-low power Filed Programmable Gate Array (F.P.G.A) and a hand full analog components. The system fits on a 10 mm outer diameter Printed Circuit Board (PCB), consumes less than 2.5 mW and is able to measure up to 1 mm ciliary muscle displacements. Full article

Visible Light Communication (VLC) uses light-emitting diodes to provide wireless connectivity in public environments. Transmission security in this emerging channel is not trivial. Chaotic modulation techniques can provide encryption directly in the physical layer based on the random-alike evolution and strong synchronization prospect given by deterministic chaos. In secure chaotic inclusion or embedding methods, continuous-time chaos oscillator models need to be synchronized via a coupling carrier. Here we present a first numerical simulation study for the impact of the variable delays induced by line-of-sight and non-line-of-sight multipath fading in complete chaotic synchronization. More precisely, we analyze a chaotic Colpitts oscillator that is simultaneously transmitting the carrier to several mobile receivers via nine spotlights. Such induced delays depend on both the receiver position and the carrier frequency, influencing the complete synchronization required in modulation via chaotic inclusion. Correlation values for several receiver positions and carrier frequencies are presented, examining the progressive emergence of the multipath effect and its impact on chaotic synchronization. We show that, for the chaotic oscillator and coupling applied in the defined room settings, complete chaotic synchronization can be achieved and that it is robust up to the tens of MHz region. Full article

This paper presents a sensitivity-enhanced gas sensor based on a film bulk acoustic resonator (FBAR). It was designed and fabricated with micro through-holes in its top electrode for sensitivity enhancement. The sensor was driven by a Colpitts oscillator circuit, and the output signal had characteristics of a power of −2.6 dBm@3 V and a phase noise of −90 dBc/Hz@100 kHz. In order to test the performance of the sensor, it was used for the detection of relative humidity (RH) and ethanol. When the relative humidity ranged from 25% to 88%, the frequency shift of the sensor was 733 kHz, which was 3.2 times higher than that of the existing FBAR sensor with a complete top electrode. Fitting results of the frequency shift and the relative humidity indicated that the measurement error was within ±0.8% RH. When the ethanol concentration ranged from 0 to 0.2355 g/L, the frequency shift of the sensor was 365 kHz. The effect of the oscillator circuit on the adsorption reaction and temperature response of the FBAR sensor device was analyzed to optimize its detection application. Full article