# Chapter 7: Angle Modulation Transmission – Tomasi Review

(Last Updated On: March 17, 2020) This is the summary notes of the important terms and concepts in Chapter 7 of the book "Electronic Communications System" by Wayne Tomasi. The notes are properly synchronized and concise for much better understanding of the book. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.

 CHAPTER 7 ANGLE MODULATION TRANSMISSION

 Items Definitions Terms 1 Two forms of angle modulation. FM and PM 2 Angle modulation was first introduced in the year ________ as an alternative to amplitude modulation. 1931 3 He developed the first successful FM radio system in 1936, and in July 1939, the first regularly scheduled broad-casting of FM signals began in Alphine, New Jersey. Also developed the superheterodyne receiver. Major E. H. Armstrong 4 A modulation that results whenever the phase angle (θ) of a sinusoidal wave is varied with respect to time. Angle Modulation 5 Varying the frequency of a constant-amplitude carrier directly proportional to the amplitude of the modulating signal at a rate equal to the frequency of the modulating signal. Direct Frequency Modulation ( FM ) 6 Varying the phase of a constant-amplitude carrier directly proportional to the amplitude of the modulating signal at a rate equal to the frequency of the modulating signal. Direct Phase Modulation ( PM ) 7 The relative angular displacement (shift) of the carrier phase in radians in respect to the reference phase. Phase Deviation (Δθ ) 8 The relative displacement of the carrier frequency in hertz in respect to its unmodulated value. Frequency Deviation (ΔF ) 9 The original unmodulated carrier frequency in the resultant angle-modulated waveform. Carrier Rests Frequency 10 The instantaneous change in the phase of the carrier at a given instant of time and indicates how much the phase of the carrier is changing with respect to its reference phase. Instantaneous Phase Deviation 11 The precise phase of the carrier at a given instant of time. Instantaneous Phase 12 The instantaneous change in frequency of the carrier and is defined as the first time derivative of the instantaneous phase deviation. Instantaneous Frequency Deviation 13 The precise frequency of the carrier at a given instant of time and is defined as the first time derivative of the instantaneous phase. Instantaneous Frequency 14 Are the output–versus-input transfer functions for the modulators, which give the relationship between what output parameter changes in respect to specified changes in the input signal. Deviation Sensitivities 15 Is called the modulation index or sometimes index of modulation. Peak Phase Modulation 16 The change in frequency that occurs in the carrier when it is acted on by a modulating-signal frequency. Frequency Deviation 17 The peak-to-peak frequency deviation (2Δf). Carrier Swing 18 The ratio of the frequency deviation actually produced to the maximum frequency deviation allowed by law stated in percent form. Percent Modulation 19 A circuit in which the carrier is varied in such a way that its instantaneous phase is proportional to the modulating signal. Phase Modulator 20 A circuit which the carrier is varied in such a way that its instantaneous phase is proportional to the integral of the modulating signal. Frequency Modulator 21 ________ of the first kind for several values of modulation index provides the number of side frequency pairs and their corresponding magnitude. Bessel Function 22 A side frequency is not considered significant unless it has amplitude equal to or greater than ____ of the unmodulated carrier amplitude. 1% 23 The modulation index is less than 1. Low-index Case 24 The modulation index is greater than 10. High-index Case 25 Modulation indices greater than 1 and less than 10. Medium Index 26 Low-index FM systems are sometimes called? Narrowband FM 27 A rule which is an approximation and gives transmission bandwidths that are slightly narrower than the bandwidths. It defines a bandwidth that includes approximately 98% of the total power in the modulated wave. Carson’s Rule 28 The worst-case modulation index and is equal to the maximum peak frequency deviation divided by the maximum modulating-signal frequency. Deviation Ratio ( DR ) 29 The FCC has assigned the commercial FM broadcast service a _______ band of frequencies that extends from 88 MHz to 108 MHZ. 20 MHz 30 The 20–MHz band is divided into 100, ________ wide channels beginning at 88.1 MHz. 200 kHz 31 To provide high-quality, reliable music, the maximum frequency deviation allowed is _______ with a maximum modulating-signal frequency of _______. 75 kHz ; 15 kHz 32 The highest side frequencies from one channel are allowed to spill over into adjacent channels, producing an interference known as _______. Adjacent Channel Interference 33 A _______ wide guard band is usually on either side of each assigned channel. 200 kHz 34 The noise voltage at the output of an FM demodulator increases linearly with frequency. This is called ______. FM Noise Triangle 35 The high-frequency modulating signals are emphasized or boosted in amplitude in the transmitter prior to performing modulation. Pre-emphasis 36 The reciprocal of pre-emphasis that restores the original amplitude-versus-frequency characteristics to the information signals. De-emphasis 37 A circuit that provides a constant increase in the amplitude of the modulating signal with an increase in frequency. Pre-emphasis Network 38 When the frequency of the carrier is modulated by the information signal, _______ results. Direct FM ( Indirect PM ) 39 When the phase of the carrier is modulated by the information signal, _______ results. Direct PM ( Indirect FM ) 40 Angle modulation in which the frequency of the carrier is varied directly by the modulating signal. Direct FM 41 Three common methods for producing direct frequency modulation. Varactor Diode, FM Reactance, Linear IC Modulations 42 Direct frequency modulator used for low-index Applications, such as two-way mobile radio. Varactor Diode Direct FM Modulator 43 A direct FM modulator using a JFET as the active device. FM Reactance Modulator 44 A complete FM modulator on a single 8-pin DIP integrated circuit chip. MC1376 45 Can generate a direct FM output waveform that is relatively stable, accurate, and directly proportional to the input modulating signal. Linear IC VCO and Function Generators 46 Angle modulation in which the frequency of the carrier is deviated indirectly by the modulating signal. Direct PM 47 Two common methods for producing direct phase modulation. Varactor Diode and Transistor Direct PM Modulator 48 The process of up-converting the frequency of the modulated carrier after modulation has been performed. Frequency Up-Conversion 49 Two basic methods of performing frequency up-conversion. Heterodyning and Frequency Multiplication 50 An up-conversion method where a low-frequency modulated carrier can either be up- or down-converted to a different location in the frequency spectrum without changing its modulation properties. Heterodyne Method 51 An up-conversion method where the modulation properties of a carrier can be increased at the same time that the carrier frequency is up-converted. Multiplication Method 52 Transmitters that produce an output waveform in which the frequency deviation is directly proportional to the modulating signal. Direct FM Transmitters 53 A circuit that compares the frequency of the non-crystal carrier oscillator to a crystal reference oscillator and then produces a correction voltage proportional to the difference between the frequencies. Automatic Frequency Control ( AFC ) 54 A frequency-selective device whose output voltage is proportional to the difference between the input frequency and its resonant frequency. Frequency Discriminator 55 A voltage added to the modulating signal to automatically adjust the master oscillator’s center frequency to compensate for the low-frequency drift. dc Correction Voltage 56 A ________ preceded by a differentiator generates a PM waveform. FM Modulator 57 Transmitters that produce an output waveform in which phase deviation is directly proportional to the modulating signal. Indirect FM Transmitters 58 Probably the most significant advantage of angle modulation transmission over amplitude modulation transmission. Noise Immunity 59 Allows a receiver to differentiate between two signals received with the same frequency. Capture Effect