Frenzel: Reviewer in Amplitude Modulation Circuits

(Last Updated On: May 14, 2020)

Frenzel: Reviewer in Amplitude Modulation Circuits

This is the summary notes of the important terms and concepts in Chapter 3 of the book COMMUNICATIONS ELECTRONICS by Louis E. Frenzel. This book introduces basic communication concepts and circuits, including modulation techniques, radio transmitters and receivers. It also discusses antennas and microwave techniques at a technician level and covers data communication techniques (modems, local area networks, fiber optics, satellite communication) and advanced applications (cellular telephones, facsimile and radar). The work is suitable for courses in Communications Technology. 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 3 Amplitude Modulation Circuits

1. Amplitude modulation can be accomplished by multiplying the carrier sine wave by a gain or attenuation factor that varies in accordance with the intelligence signal.

2. Amplitude modulation can be carried out by linearly combining the carrier and intelligence signals then applying the result to a nonlinear component or circuit. A diode is an example.

3. The simplest AM circuit uses resistors to linearly mix the carrier and information signal, a diode to rectify the result, and a tuned circuit to complete the waveform.

4. Amplitude modulation can be produced by feeding the carrier to a voltage divider or other network and then varying one of the resistive elements in accordance with the modulating signal. Common variable resistive components are diodes and FETs. PIN diodes are used at UHF and microwave frequencies.

5. Low-level modulation is the process of generating ‘the AM signal at low voltage and/or power levels and then using linear amplifiers to increase the power level.

6. High-level modulation is the processes of amplitude modulating the final power amplifier of a transmitter.

7. High-level modulation is accomplished with a collector (plate in vacuum tubes) modulator that varies the collector supply voltage in accordance with the modulating signal.

8. For 100 percent high-level modulation, the modulation amplifier must produce an out put wave whose peak-to-peak is 2 times the collector supply voltage.

9. For 100 percent high-level modulation, the modulation amplifier must generate an output power that is one-half of the final RF power amplifier input power (Pi =Vcc x Ic).

10. The simplest and best amplitude demodulator is the diode detector. The AM signal is rectified by a diode and then filtered by a capacitor to recover the envelope which is the original modulating information.

11. Balanced modulators are AM circuits that cancel or suppress the carrier but generate a DSB output signal that contains the upper (sum) and lower (difference) sideband frequencies.

12. A popular balanced modulator is the lattice modulator that uses a diode bridge circuit as a switch. The carrier turns the diodes off and on letting segments of the modulating signal through to produce a DSB output signal. A carrier suppression of 40 dB is possible.

13. Another widely used balanced, modulator is an integrated circuit (IC) using differential amplifiers as switches to switch the modulating signal at the carrier frequency. A popular device is the 1496 or 1596. Carrier suppression can be as high as 50 to 65 dB.

14. The most common way of generating an SSE signal is to use the filter method which incorporates a balanced modulator followed by a highly selective filter that passes either the upper or lower sideband.

15. To make both sidebands available, SSB generators use two filters, one for each sideband, or switch the carrier frequency to put the desired sideband into the fixed filter, bandpass.

16.Most SSB, filters are made with quartz crystals.

17.A quartz crystal is a frequency-determining component that acts like an LC circuit with a very high Q.

18. Crystals have series and parallel resonant modes. These can be combined into a lattice (bridge) circuit that provides extremely sharp selectivity over a desired bandwidth.

19. Ceramic filters use ceramic resonators that act like crystals but are smaller and lower in cost.

20. Mechanical bandpass filters are also used in SSE generators. These devices use multiple resonant disks that vibrate at some frequency in the 200- to 500-kHz range.

21. The phasing method of SSE generation uses two balanced modulators and 90° phase shifters for the carrier and modulating signal to produce two DSB signals that when added cause one sideband to be canceled out.

22. In phasing-type SSE generators, the accuracy of the phase shifters determines the degrees of unwanted sideband suppression.

23.Precision RC networks are normally used to produce the desired 90° phase shifts.

24. A demodulator for SSE is a mixer such as a balanced modulator that, is called a product detector. The carrier is reinserted in the receiver with a local oscillator.

25. Frequency translation or conversion is an AM process that converts a signal with any modulation to a higher (up conversion) or lower (down conversion) frequency.

26. Frequency conversion is produced by a circuit called a mixer.

27. Another name for frequency conversion is heterodyning.

28. Almost any low-level AM circuit can be used for mixing.

29. One of the most commonly used mixers is a single diode. Germanium or hot-carrier diodes are used for mixing at very high radio frequencies.

30.The inputs to a mixer are the signal to be translated fs and a sine “wave fo from a local oscillator (LO). The outputs are fo, fs, fo + fs, and fo fs. A tuned circuit at the output selects either the slim or difference frequency while suppressing the others. Any modulation on the input appears on the output signal.

31. Bipolar and field-effect transistors can be used as mixers by operating them in the nonlinear region of their characteristics.

32. Transistor mixers offer the benefit of gain over diode mixers.

33. Balanced modulators are widely used as mixers.

34. Doubly balanced modulators and GaAs FETs are the best mixers at VHF, UHF, and microwave frequencies.

35. A single transistor can be connected to perform both the mixer and LO functions. Such a mixer is called a converter and is used primarily in AM receivers at frequencies below 30 MHz.

36. A popular IC mixer is the NE602, which contains a cross-connected differential amplifier mixer circuit and an on-chip local oscillator.

Complete List of Reviewers in Communications Electronics per Chapter

Important List of Communications Engineering Materials

Share your Notes in Introduction to Electronic Communications

If you have some important review notes on this topic kindly write the notes on the comment section below. This will absolutely beneficial to those aspiring to become professional engineers by taking the Board Exam and eventually to become successful in their chosen field. Thank you.

Print Friendly, PDF & Email
Please do Subscribe on YouTube!

P inoyBIX educates thousands of reviewers and students a day in preparation for their board examinations. Also provides professionals with materials for their lectures and practice exams. Help me go forward with the same spirit.

“Will you subscribe today via YOUTUBE?”


Add Comment

PinoyBIX Engineering. © 2014-2020 All Rights Reserved | How to Donate? | Follow me on Blogarama Protection Status

Math Solution

Advanced Math problem age work mixture digit motion Analytic Geometry 01 problem Analytic Geometry 02 problem clock variation progression misc Combination problem Differential Calculus 01 Problem Differential Calculus 02 Problem Differential Equations Problem Fundamentals in Algebra Fundamentals in Algebra Problem Integral Calculus problem Permutation problem Plane Geometry problem Plane Trigonometry problem Probability problem quadratic equation binomial theorem logarithms Solid Geometry problem Spherical Trigonometry problem System of Numbers Problem Venn Diagram Problem

Questions and Answers in Mathematics

Advanced Math Age Work Mixture Digit Motion Algebra and General Mathematics Analytic Geometry 01 Analytic Geometry 02 Calculus Clock Variation Progression Misc Differential Calculus 01 Differential Calculus 02 Differential Equations Engineering Mathematics Geometry Integral Calculus Plane Geometry Plane Trigonometry Probability and Statistics Quadratic Equation Binomial Theorem Logarithms Solid Geometry Spherical Trigonometry System of Numbers Trigonometry


Pre-board in Electronics Engineering

Answers Pre-board in Electronics Engineering - Answers

Questions and Answers

Basic Television - Grob TV Boylestad Questions and Answers Computer Principles Electrical Circuit Electricity and Magnetism Fundamentals Electronic Circuits Floyd Questions and Answers Floyd Self-test Gibilisco Questions and Answers Grob Questions and Answers Industrial Electronics Principles and Applications Malvino Questions and Answers Microelectronics Power Generators / Sources / Principles and Applications Solid State Devices Tests and Measurements Vacuum Tubes

Pre-board in Communications Engineering


Questions and Answers

Acoustics Antennas Blake Questions and Answers Broadcasting and Cable TV System Digital Communication Networks Forouzan Frenzel Self-test Kennedy Questions and Answers Microwave Communications Miscellaneous Questions in Communications Modulation Navigational Aids and Radar Systems Noise Optical Fiber Communications Radiation and Wave Propagation Satellite Communications Transmission Fundamentals Wire and Wireless Communications

GEAS Solution

Dynamics problem Economics problem Physics problem Statics problem Strength problem Thermodynamics problem

Pre-board in GEAS

Questions and Answers in GEAS

Engineering Economics Engineering Laws and Ethics Engineering Management Engineering Materials Engineering Mechanics General Chemistry Giancoli Physics Physics Strength of Materials Thermodynamics
Online Tool: Electrical Charge Conversions
Online Tool: Electrical Charge Conversions
Online Tool: Color Code Conversions
Online Tool: Color Code Conversions
Online Tool: Weight Measurement Conversions
Online Tool: Weight Measurement Conversions
Online Tool: Temperature Measurement Conversions
Online Tool: Temperature Measurement Conversions