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Electronic Communications
Published in Dale R. Patrick, Stephen W. Fardo, Electricity and Electronics Fundamentals, 2020
Dale R. Patrick, Stephen W. Fardo
FM signal reception is achieved in basically the same way as AM and CW. An FM superheterodyne circuit is designed to respond to frequencies in the VHF band. Commercial FM signal reception is in the 88- to 108-MHz range. Higher-frequency operation generally necessitates some change in the design of antenna, RF amplifier, and mixer circuits. These differences are due primarily to the in-creased frequency rather than the FM signal. The RF and IF sections of an FM receiver are somewhat different. They must be capable of passing a 200-kHz bandwidth signal in-stead of the 10-kHz AM signal. The most significant difference in FM reception is in the demodulator. This part of the receiver must pick out the modulating component from a signal that changes in frequency. In general, this circuit is more complicated than the AM detector. The AF amplifier section of an FM receiver is generally better than an AM receiver. It must be capable of amplifying frequencies of 30 Hz to 15 kHz. Figure 7-33 shows a block diagram of an FM super-heterodyne receiver. Some differences in FM reception are indicated by each functional block.
Modulation Techniques
Published in Stephen Horan, Introduction to PCM Telemetering Systems, 2018
Table 10.1 lists the parameter differences of FM and PM. Note that the units of several parameters are different. The modulation characteristics of FM are more affected by the amplitude of the message signal while PM is more affected by the derivative of the amplitude of the message signal. Since the derivative is affected by the harmonic content of the signal, PM is more affected by the shape of the amplitude spectrum of the message signal. Comparing output SNR improvement as a function of the signal’s spectrum and transmission characteristics will illustrate this. The mean-square bandwidth in Hz is defined for a message signal, m(t), in terms of its spectrum, M(ω), by the equation:5 () Bm2¯=∫−∞∞f2M(2πf)df∫−∞∞M(2πf)df
Signal Conversion Methods
Published in Clarence W. de Silva, Sensor Systems, 2016
In frequency modulation (FM), the frequency of the carrier signal is varied in proportion to the amplitude of the data signal (modulating signal) while keeping the amplitude of the carrier signal constant. Suppose that the data signal shown in Figure 4.1a is used to frequency modulate a sinusoidal carrier signal. The modulated result will appear as in Figure 4.1c. Since in FM, the information is carried as frequency rather than amplitude, any noise that might alter the signal amplitude would have virtually no effect on the transmitted data. Hence, FM is less susceptible to noise than AM. Furthermore, since in FM the carrier amplitude is kept constant, signal weakening and noise effects that are unavoidable in long-distance data communication/transmission will have less effect than in the case of AM, particularly if the data signal level is low in the beginning. However, more sophisticated techniques and hardware are needed for signal recovery (demodulation) in FM transmission because FM demodulation involves frequency discrimination rather than amplitude detection. FM is also widely used in radio transmission and in data recording and replay.
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).
Analysis of Cascaded Multilevel Inverter with a Reduced Number of Switches for Reduction of Total Harmonic Distortion
Published in IETE Journal of Research, 2023
Kola Muralikumar, P Ponnambalam
The FM index (mf) is the equivalent of MI for m. Taking into consideration, the modifications among the two forms of modulation, the (mf) modulation index is measured in a dissimilar way [29,30]. The FM index is equal to the ratio of frequency deviation to the modulating frequency. Taking an example of FM modulation index, if a signal has a deviation of ±5 kHz, and the modulating frequency is 1 kHz, then the MI for this particular instance is 5/1 = 5.