Explore chapters and articles related to this topic
Analog Modulation for Mobile Radio
Published in Michel Daoud Yacoub, Foundations of Mobile Radio Engineering, 2019
The standard AM scheme has in its favor ease of implementation and spectrum saving: Demodulation can be carried out by means of an envelope detector or a square-law detector, and the transmission bandwidth is only twice the message bandwidth. On the other hand, additional power is required to transmit the carrier. SSB modulation requires the minimum transmitter power and minimum transmission bandwidth but the receivers are more complex. The FM scheme usually needs more frequency spectrum but yields better performance in the presence of noise.
The Electromagnetic Phenomena as Incitants
Published in William J. Rea, Kalpana D. Patel, Air Pollution and the Electromagnetic Phenomena as Incitants, 2018
William J. Rea, Kalpana D. Patel
Frequency modulation (FM) is the coding of information in a carrier wave where the frequency varies and the amplitude remains constant. This wave is compared with the amplitude modulation (AM), in which the amplitude of the carrier wave varies while the frequency remains consistent.
Modulation
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Techniques that modulate the amplitude of the carrier are full-carrier amplitude modulation (AM), reduced- or suppressed-carrier double-sideband (DSB) AM, single-sideband (SSB) suppressed-carrier modulation, vestigial-sideband (VSB) modulation, and on–off keying (OOK). Techniques that modulate the frequency or phase angle of the carrier include frequency modulation (FM), phase modulation (PM), frequency-shift keying (FSK), and phase-shift keying (PSK). Simultaneous variation of amplitude and phase are applied in quadrature AM (QAM). Each technique has its own particular uses. Full-carrier AM is used in radio broadcasting; VSB was formerly used in analog television broadcasting. DSB appears in instrumentation systems utilizing carrier amplifiers and modulating sensors, while SSB finds use in certain high-frequency radio communications. FM is used in broadcasting and point-to-point mobile communications. OOK is commonly used to transmit digital data in optical fiber links. FSK, PSK, and QAM are found in digital communications; analog QAM was formerly used to transmit chrominance (color) information in color television broadcasting. The emphasis of this particular chapter will be instrumentation systems; those interested principally in communications applications could begin by consulting Refs. [1–4].
TSV fault contactless testing method based on group delay
Published in International Journal of Electronics, 2021
Yuling Shang, Yamin Zhao, Chunquan Li, Min Tan, Lizhen Zeng
The design of the mixed testing stimulus is based on the modulation method of measuring group delay. When the mixed testing stimulus passes the pending testing TSV, its phase change proportionally with the phase-frequency response of the TSV. The phase-frequency response of the faulty TSV is no longer linear, and it appears that the output response causes its RMS voltage to change significantly, so the TSV fault can be detected according to the CF value. The modulation method includes the amplitude modulation (AM) and the frequency modulation (FM). The better the anti-interference capability, the wider bandwidth and the greater the total power of the transmitted modulated signal can be obtained by FM. Thus, amulti-tone FM signal with wideband can be designed with the equation (14).
Surfing the Radio Spectrum Using RTL-SDR
Published in IETE Journal of Education, 2019
Antonios Valkanas, Divyanshu Pandey, Harry Leib
A sanity test to ensure correct hardware and software setup is to receive an FM broadcast signal. For this experiment, due to the strength of the signal, any antenna including the stock antenna that comes with the RTL-SDR kit will suffice. After connecting the dongle to the computer and starting SDR#, we surf the FM radio band (between 80 and 110 MHz). Using the FFT spectrum plot we tune to an FM radio station with a good signal level and adjust the receiver bandwidth to contain the entire signal. For FM radio the signal bandwidth is 200 kHz. We can get a high SNR if the receiver is located within a few kilometers of a radio station which is generally true in any urban environment. The FFT spectrum and the waterfall display is shown in Figure 6.
Experimental verification of trinary DC source cascaded H-bridge multilevel inverter using unipolar pulse width modulation
Published in Automatika, 2019
G. Irusapparajan, D. Periyaazhagar, N. Prabaharan, A. Rini ann Jerin
The 27-level single phase trinary sequence DC source CHBMLI is demonstrated in MATLAB/SIMULINK which is shown in Figure 2(e). The switching signals for proposed CHBMLI are generated using multicarrier sinusoidal unipolar PWM methods. Figures 3–6 shows the output voltage and current waveform for different types of carrier arrangement along with its voltage FFT plot at the modulation index of 1. The %THD depends on the range of switching frequencies. The frequency modulation index mf is defined as the ratio between the frequencies of the carrier fcr and modulating wave fm. When mf is a small number (i.e. less than 21), it's output spectrum contains low-frequency harmonics (sub-harmonics) causing high currents in transformers and inductors. Note that in the case of mf being a large number, the amplitudes of the sub-harmonics are highly reduced and do not pose critical problems with the currents by inductors and transformers. Therefore, the selected topology generates low order harmonics with the obtained high frequency, but the order harmonic values have considerable limits, i.e. within the IEEE 519 standard. Hence, low order harmonics do not affect the system. The FFT subplots are with low individual harmonic order and thus do not affect the system performance [31,32]. The simulation results are examined for different range of modulation index values of 0.85–1 and the values are tabulated. Table 2 shows the values of simulation parameters. The %THD (a quantity of similarity in shape concerning a waveform and its essential component) is evaluated for different types of carrier arrangement using the FFT block and their values are tabulated in Table 3. APODPWM provides lesser %THD as compared with other type of carrier arrangement. Table 4 shows the fundamental VRMS value of output voltage for different types of carrier arrangement. COPWM method provides better VRMS as compared to other methods. Table 5 presents the Crest Factor (CF) value which is used to identify peak current evaluation of the semiconductor device. The value of CF is almost same for all PWM methods at different modulation indices. Table 6 shows the Distortion Factor (DF) of the output voltage. PDPWM method provides lesser distortion factor as compared with other PWM methods. Table 7 shows the Form Factor (FF) associated with power quality problem. The formulas for calculating the CF, FF and DF are follows