Adaptive filter and pulse-shaping for interference cancellation of differential quadrature phase-shift keying modulation

Differential quadrature phase-shift keying (DQPSK) modulation methods and variations are commonly used in wireless communication, including high-speed optical fiber, Bluetooth, and satellite communication. DQPSK cannot be isolated from possible interference with its present application. The interference cancellation process has been observed and analyzed using a device model built in this study. The core components of the supporting block for this device model have raised cosine filters for pulse shaping and adaptive filters. The presence of these core components has resulted in a dramatic improvement in device efficiency, according to robust Simulink data. The best bit error rate (BER) of 5.7e-03 provides evidence of this.

Extended L-Band InAs/InP Quantum-Dash Laser in Millimeter-Wave Applications

We report on the generation and transmission of a millimeter-wave (MMW) signal with a frequency of 28 GHz by employing an InAs/InP quantum-dash dual-wavelength laser diode (QD-DWL) emitting in the ~1610 nm extended L-band window. The self-injection locking (SIL) technique has been engaged to improve the linewidth and reduce the noise of the optical tone. Besides, the transmission of a 2 Gbits/s quadrature phase-shift keying (QPSK)-modulated 28-GHz MMW beat tone over a hybrid 20-km radio-over-fiber combined with 5-m radio-over-free-space-optics and up to 6-m radio frequency wireless link has been demonstrated. Moreover, comparing the proposed QD-DWL with a commercial laser showcased similar performance characteristics, making the QD-DWL a candidate source for MMW applications.

A Reduction of Peak-to-Average Power Ratio Based Faster-Than-Nyquist Quadrature Signals for Satellite Communication

The increase in the throughput of digital television and radio broadcasting (DVB) channels can be achieved due to application of signals with a compact spectrum and a relatively small peak-to-average power ratio (PAPR). The reason is the usage of traveling wave tubes (TWT) for amplifying and transmitting signals from a satellite repeater in DVB-S2X systems. At the same time, given that the bandwidth allocated for transmission should be used as efficiently as possible, a high reduction rate of out-of-band emissions level is required. The most effective solution in this direction is the transition to spectrum-economic signals, such as optimal Faster-Than-Nyquist (FTN) signals, which can provide a certain reduction rate of the out-of-band emissions level and minimum acceptable PAPR. This article proposes a method for obtaining optimal FTN pulses, which have symmetry in time domain, with specified PAPR and reduction rate of out-of-band emissions for the quadrature phase shift keying (QPSK) and offset quadrature phase shift keying (OQPSK). The possibility of synthesizing signals with OQPSK modulation is presented theoretically for the first time. Optimal FTN signals can provide PAPR reduction by at most 3 dB and outperform known root raised cosine (RRC) pulses. The simulation model adopts an architecture for quadrature generation of optimal FTN signals with OQPSK modulation with blocks for adjustable pre-amplification, clipping, and power amplification. The proposed signals can be used to increase the spectral and energy efficiencies of satellite broadcasting systems, such as DVB-S2/S2X, as well as low-rate return channels of interactive broadcasting systems with a frequency resource shortage.

Algorithm for measuring distortion in a signal with quadrature phase shift keying (QPSK)

The article describes the types of distortion of the QPSK signal and the algorithms for measuring the parameters of distortions in the conditions of their simultaneous presence in the signal.