Plataforma educativa para desarrollo de sistemas de software radio mediante modulación QPSK en Octave y Arduino

Nowadays, the development of software radio based systems has allowed the transmission of data at high speeds and frequencies in the order of Gigahertz (Jovanovic, 2018). For this, the digital system is characterized by using digital modulation techniques in software through transmission symbols in the DigitalEnd stage, applying digital-analog (DAC) and analogdigital (ADC) converters to vary the sampling frequency and transmit the data in the Front End, (Chien, 2001). This work presents a digital educational platform to simulate the characteristics of a Software Radio system and not a web platform. The present investigation is focused on the characterization of signals modulated by Octave considering in the first instance the quadrature modulation QPSK, where the transmission of the modulated signal is carried out by means of the Arduino board in a digital port, with a digital-analog approach (DAC) using PWM modulation a RC filter and an amplifier circuit, which synthesize the signal considering the limitations of the Arduino board. The proposed design presents an electronic platform that will allow the understanding of software-based radio systems.

Quadrature MC-DCSK Scheme for Chaos-Based Cognitive Radio

In this study, we investigate an enhanced architecture of multicarrier differential chaos-shift keying (MC-DCSK) scheme using quadrature modulation (QM), namely QMC-DCSK. The use of quadrature modulation aims at doubling the data rate over a defined bandwidth and hence improve bandwidth efficiency of the system. In the proposed scheme, the chaotic spreading sequence is transmitted on a predefined frequency while each of the remaining frequencies is phase-shifted at a [Formula: see text] angle in order to produce two quadrature subcarriers located at the same frequency. These subcarriers are modulated by the product of the chaotic spreading sequence and the corresponding bit substreams in parallel. Noncoherent demodulation is carried out in the receiver in order to recover the original data based on the sign of correlation values. Architecture and operation of the conventional and proposed schemes are described. The BER performance over a wireless channel is theoretically derived and then numerically verified. The bit rate, energy and bandwidth efficiencies are evaluated in comparison with those of MC-DCSK. In particular, the application of the proposed scheme to cognitive radio (CR) in the scenario of using multicarrier modulation and chaotic spread-spectrum is discussed and evaluated. The obtained results prove that QMC-DCSK is a fit technique for CR communications.

Automatic Frequency Tuning Technology for Dual-Mass MEMS Gyroscope Based on a Quadrature Modulation Signal

In order to eliminate the frequency mismatch of MEMS (Microelectromechanical Systems) gyroscopes, this paper proposes a frequency tuning technology based on a quadrature modulation signal. A sinusoidal signal having a frequency greater the gyroscope operating bandwidth is applied to the quadrature stiffness correction combs, and the modulation signal containing the frequency split information is then excited at the gyroscope output. The effects of quadrature correction combs and frequency tuning combs on the resonant frequency of gyroscope are analyzed. The tuning principle based on low frequency input excitation is analyzed, and the tuning system adopting this principle is designed and simulated. The experiments are arranged to verify the theoretical analysis. The wide temperature range test (-20 ∘ C –60 ∘ C ) demonstrates the reliability of the tuning system with a maximum mismatch frequency of less than 0.3 Hz. The scale factor test and static test were carried out at three temperature conditions (−20 ∘ C, room temperature, 60 ∘ C), and the scale factor, zero-bias instability, and angle random walk are improved. Moreover, the closed-loop detection method is adopted, which improves the scale factor nonlinearity and bandwidth under the premise of maintaining the same static performances compared with the open-loop detection by tuning.