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Interrogators
Published in Albert Lozano-Nieto, RFID Design Fundamentals and Applications, 2017
The ASK signal is demodulated by detecting the envelope of the carrier, normally using a half-wave rectifier. This detects the peak amplitude of the signal generated by the transponder and feeds it into an RC circuit that charges and discharges accordingly. The time constant of the RC circuit must be chosen with these two considerations: (1) it must be small enough so the voltage across the capacitor diminishes fast enough in order to keep with the changes in the envelope of the signal, and (2) it must be high enough to avoid excessive ripple in the detected signal. After the envelope has been detected, the resulting signal is passed through a low-pass filter and a signal-shaping circuit and finally fed into a microcontroller. Figure 5.8 shows the schematic of the detector in the receiver section of a commercially available interrogator working in the LF range at 125 kHz.
Discrete signals
Published in J. Dunlop, D. G. Smith, Telecommunications Engineering, 2017
Although, strictly speaking, FSK is FM, it is more convenient to consider FSK as the sum of two ASK waveforms with different carrier frequencies. The spectrum of the FSK wave is thus the sum of the spectra of the two ASK waves. This spectrum is shown in Fig. 3.36. Using the FM analogy, it is possible to define a ‘carrier frequency’ fc = f0 + (f1 − f1)/2 and a ‘carrier deviation’ Δf =(f1 − f0)/2. The modulation index β is defined as β = Δf/B, where B = 1 /t1 is the bandwidth of the data signal. Using these definitions the bandwidth of the FSK signal is () BFSK=2B(1+β)
Modulation Schemes
Published in Stephan S. Jones, Ronald J. Kovac, Frank M. Groom, Introduction to COMMUNICATIONS TECHNOLOGIES, 2015
Stephan S. Jones, Ronald J. Kovac, Frank M. Groom
Amplitude shift keying (ASK) uses the basic form of an analog AM delivery system. The ASK technique overlays digital information onto the carrier frequency instead of the normal analog information that would be put on the carrier frequency. The transmission is sent through high- and low-amplitude signals. The high-amplitude signal is replaced by a binary 1 (1), and the low-amplitude signal is replaced by a binary 0 (Exhibit 3.20). Because there is a big difference between high- and low-amplitude signals, this replacement greatly reduces the chance of the signal being misread. This is important because AM is normally more susceptible to noise and energy spikes in the frequency. The downside to this method is the susceptibility to sudden gain changes. Also, it is an inefficient modulation technique.
Proactive flow control using adaptive beam forming for smart intra-layer data communication in wireless network on chip
Published in Automatika, 2023
Dinesh Kumar T.R., Karthikeyan A.
The power required for transmission throughout the data flow process is determined by numerous factors, including modulation type, transceiver noise, and attenuation introduced by the wireless medium. Given a transmitting and receiving antenna, the signal strength requirement is determined to determine the minimum transmitting power that assures a specified data rate and bit error rate (BER). The most extensively used modulation strategy in WiNoC for adjusting the baseband signal to the wireless medium is Amplitude Shift Keying (ASK) or On–Off Keying (OOK). The BER in ASK-OOK modulation is computed using, where Ebit denotes energy consumed per bit, TN is the noise introduced by the transceiver and P denotes the standard normal distribution's tail probability.
ASER of SISO system with rectangular QAM scheme over α-μ fading channels
Published in International Journal of Electronics Letters, 2022
To implement the high-speed mobile communication systems, quadrature amplitude modulation (QAM) technique can be used. QAM constellations are the basis of many high-speed mobile communication architectures: Wi-Fi (IEEE 802.11), WiMAX, cellular, digital video broadcasting (Suraweera et al., 2008). A large bandwidth is required for the multimedia transmission over wireless channels. The QAM is an efficient scheme, which can be used to meet the large bandwidth demand. Rectangular QAM (RQAM), square QAM (SQAM) and cross QAM (XQAM) are familiar QAM signal constellations that have numerous applications in communication systems. RQAM is a general modulation scheme which comprises SQAM, BPSK, QPSK, orthogonal binary frequency-shift keying and multilevel amplitude-shift keying (ASK) modulation schemes as particular cases (Proakis, 2001). The XQAM constellation has a cross shape by eliminating all the outer corner points from RQAM constellation to decrease the peak and average energy of the signal, and is found to be useful in the transmission for odd number of bits per symbol (Smith, 1975).
Photonics generation of microwave linearly chirped signal with amplitude and phase modulation capability
Published in Journal of Modern Optics, 2021
Xuan Li, Shanghong Zhao, Guodong Wang
In this paper, a photonics scheme is proposed to generate a frequency up-converted, bandwidth multiplied, amplitude and phase modulated linearly chirped waveform. The key components of the scheme including a dual-polarization binary phase shift keying (DP-BPSK) modulator, an optical filter (OF), a polarization controller (PC) and a polarization modulator (PolM). The DP-BPSK modulator is driven by a linearly chirped waveform and an RF signal, respectively. After the OF, an orthogonally polarized optical signal is obtained, i.e. a second-order optical RF sideband in one polarization direction while a second-order optical chirped sideband in another one. The PC is employed to select the data modulation format, i.e. amplitude modulation or phase modulation. Then the orthogonally polarized optical signal injected into the PolM to experience complementary phase modulations. After photodetection, a frequency up-converted and bandwidth doubled linearly chirped waveform with amplitude and phase modulation capability can be obtained. Amplitude shift keying (ASK), multiple ASK (MASK), phase shift keying (PSK), multiple PSK (MPSK) and quadrature PSK (QPSK) linearly chirped signals are demonstrated. A phase coherent demodulation structure in the transmitting end to monitor the waveform performance is introduced. The impact of finite polarization extinction ratio (PER) on the system performance is investigated. The proposed scheme features high frequency, broad bandwidth, large tunability, good modulation format agility and improved stability, which can be potentially employed in radar systems and wireless covert communications.