Chapter 5: Amplitude Modulation Reception - Review Notes

This is the summary notes of the important terms and concepts in Chapter 5 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 5

AMPLITUDE MODULATION RECEPTION

Items	Definitions	Terms
1	The reverse process of AM modulation.	AM Demodulation
2	The first stage of the receiver of which primary functions are detecting, band limiting, and amplifying the received.	RF Section
3	This section down-converts the received RF frequencies to intermediate frequencies (IFs).	Mixer / Converter
4	This section primary functions are amplification and selectivity.	IF Section
5	This section demodulates the AM wave and converts it to the original information signal.	AM Detector
6	This section amplifies the recovered information. Comprises several cascaded audio amplifiers and one or more speakers.	Audio Section
7	A receiver parameter that is used to measure the ability of the receiver to accept a given band of frequencies and reject all others.	Selectivity
8	The ratio of the bandwidth 60dB below maximum signal level and bandwidth 3dB below maximum signal level.	Shape Factor
9	The most prevalent form of noise and is directly proportional to bandwidth.	Thermal Noise
10	Noise reduction ratio achieved by reducing the Bandwidth.	Bandwidth Improvement
11	The corresponding reduction in the noise figure due to the reduction in bandwidth expressed mathematically in dB.	Noise Figure Improvement
12	The ________ of a receiver is the minimum RF signal level that can be detected at the input to the receiver and still produce a usable demodulated information signal. Also known as receiver threshold.	Sensitivity
13	Defined as the difference in decibels between the minimum input level necessary to discern a signal and the input level that will overdrive the receiver and produce distortion.	Dynamic Range
14	Defined as the output power when the RF amplifier response is 1 dB less than the ideal linear-gain response.	1-dB Compression Point
15	A measure of the ability of a communication system to produce, at the output of the receiver, an exact replica of the original source information.	Fidelity
16	Any frequency, phase, or amplitude variations that are present in the demodulated waveform that were not in the original information signal.	Distortion
17	The total phase shift encountered by a signal and can generally be tolerated as long as all frequencies undergo the same amount of phase delay.	Absolute Phase Shift
18	Occurs when different frequencies undergo different phase shifts and ay have a detrimental effect on a complex waveform.	Differential Phase Shift
19	Defined as the ratio of the power transferred to a load with a filter in the circuit to the power transferred to a load without the filter.	Insertion Loss ( IL )
20	A hypothetical value that cannot be directly measured. A parameter that is used in low-noise, sophisticated radio receivers rather than noise figure.	Equivalent Noise Temperature
21	The frequencies generated in the receiver and used for demodulation are synchronized to oscillator frequencies generated in the transmitter.	Coherent / Synchronous Receiver
22	Either no frequencies are generated in the receiver or the frequencies used for demodulation are completely independent from the transmitter’s carrier frequency.	Noncoherent / Asynchronous Receiver
23	One of the earliest types of AM receivers and are probably the simplest designed radio receivers available today.	Tuned Radio Frequency
24	A phenomenon at radio frequencies where current flow is limited to the outermost area of a conductor.	Skin Effect
25	A technique where TRF receiver’s instability can be reduced somewhat by tuning each amplifier to a slightly different frequency, slightly above or below the desired center frequency.	Stagger Tuning
26	Means to mix two frequencies together in a nonlinear device or to translate one frequency to another using nonlinear mixing.	Heterodyne
27	A broad –tuned bandpass filter with an adjustable center frequency that is tuned to desired carrier frequency.	Preselector
28	The most common intermediate frequency used in AM broadcast-band receivers is ________.	455 kHz
29	Consists of a series of IF amplifiers and bandpass filters and is often called IF strip.	IF Section
30	Refer to frequencies that are used within a transmitter or receiver that fall somewhere between the radio frequencies and the original source information frequencies.	Intermediate Frequency
31	Means that the two adjustments are mechanically tied together so that a single adjustment will change the center frequency of the preselector and, at the same time, change the local oscillator frequency.	Gang Tuning
32	When the local oscillator is tuned above the RF it is?	High-side Injection / High-beat Injection
33	When the local oscillator is tuned below the RF it is?	Low-side Injection / Low-beat Injection
34	The side frequencies undergo a sideband reversal during the heterodyning process called?	Sideband Inversion
35	The ability of the local oscillator in a receiver to oscillate above or below the selected radio frequency carrier by an amount equal to the intermediate frequency throughout the entire radio frequency band.	Tracking
36	The difference between the actual oscillator frequency and the desired frequency.	Tracking Error
37	Any frequency other than the selected radio frequency carrier that, if allowed to enter a receiver and mix with the local oscillator, will produce a cross-product frequency that is equal to the intermediate frequency.	Image Frequency
38	A numerical measure of the ability of a preselector to reject the image frequency.	Image-frequency Rejection Ratio
39	Occurs when a receiver picks up the same station at two nearby points on the receiver tuning dial.	Double Spotting
40	A high-gain, low-noise, tuned amplifier that, when used, is the first active stage encountered by the received signal.	RF Amplifier
41	High-performance microwave receivers require a ________ as the input stage of the RF section to optimize their noise figure.	Low-noise Amplifier ( LNA )
42	A FET with a metal-semiconductor junction at the gate of the device, called a Schottky barrier.	MEsa Semiconductor FET Semiconductor FET ( MESFET )
43	A wideband, unconditionally stable, low-power, dual-gain linear integrated-circuit RF amplifier manufactured by Signetics Corporation.	NE / SA5200
44	This section purpose is to down-convert the incoming radio frequencies to intermediate frequencies proportional to bandwidth.	Mixer / Converter Stage
45	The difference between the level of the IF output with an RF input signal to the level of the IF output with an IF input signal.	Conversion Gain
46	A configuration where the mixer excites itself by feeding energy back to the local oscillator tank circuit to sustain oscillations noise figure.	Self-excited Mixer
47	A low-power VHF monolithic double-balanced mixer with input amplifier, on-board oscillator, and voltage regulator.	NE / SA602A
48	Are relatively high-gain amplifiers that are very similar to RF amplifiers, except that IF amplifiers operate over a relatively narrow, fixed frequency band.	Intermediate Frequency ( IF ) Amplifier
49	The most common technique used for coupling where the voltage that is applied to the primary windings of a transformer is transferred to the secondary windings.	Inductive or Transformer Coupling
50	Ability of a coil to induce a voltage within its windings.	Inductance
51	Ability of one coil to induce a voltage in another coil.	Mutual Inductance
52	The ratio of the secondary flux to the primary flux.	Coefficient of Coupling
53	The transfer of flux from the primary to the secondary windings and is directly proportional to the coefficient of coupling.	Flux Linkage
54	The point where the reflected resistance is equal to the primary resistance an d the Q of the primary tank circuit is halved and the bandwidth doubled.	Critical Coupling
55	Is caused by the reactive element of the reflected impedance being significant enough to change the resonant frequency of the primary tuned circuit.	Double Peaking
56	The coefficient of coupling approximately 50% greater than the critical value yields a good compromise between flat response and steep skirts.	Optimum Coupling
57	IF transformers come as specially designed tuned circuits in groundable metal packages called _______.	IF Cans
58	A differential cascoded amplifier designed for use in communications and industrial equipment as an IF or RF amplifier at frequencies from dc to 120 MHz.	CA3028A
59	The function of this circuit is to demodulate the AM signal and recover or reproduce the original source information.	AM Detector
60	A simple noncoherent AM demodulator using a diode. Also called as diode, shape, or envelope detector.	Peak Detector
61	A distortion in the detection process where the RC time constant is too short, the output waveform resembles a half-wave rectified signal.	Rectifier Distortion
62	A distortion in the detection process where the RC time constant is too long, the slope of the output waveform cannot follow the trailing slope of the envelope.	Diagonal Clipping
63	A circuit that compensates for minor variations in the received RF signal.	Automatic Gain Control ( AGC )
64	It prevents the AGC feedback voltage from reaching the RF or IF amplifiers until the RF level exceeds a predetermined magnitude.	Delayed AGC
65	Is similar to conventional AGC except that the receive signal is monitored closer to the front end of the receiver and the correction voltage is fed forward to the IF amplifiers.	Forward AGC
66	Its purpose is to quiet a receiver in the absence of a received signal.	Squelch Circuit
67	Are used to remove sporadic, high-amplitude noise transients of short duration, such as impulse noise in the audio section of a receiver.	Limiters / Clippers
68	A method of measuring signal strength relative to noise strength where an RF carrier modulated 30% by a 1-kHz tone is applied to the input of the receiver.	Signal-to-Notched Noise Ratio
69	A National Semiconductor Corporation linear integrated circuit AM radio chip that has an onboard RF amplifier, mixer, local oscillator, and IF amplifier stages. An LIC audio amplifier, such as the LM386, and a speaker are necessary to complete a functional receiver.	LM1820
70	This receivers would need only two external components: a volume control and a station tuning control.	PLL Receivers
71	The ratio of the demodulated signal level at the output of the receiver (audio) to the RF signal level at the input to the receiver, or the difference between the audio signal level in dBm and the RF signal level in dBm.	Net Receiver Gain
72	Includes all the gains and losses incurred by a signal as it propagates from the transmitter output stage to the output of the detector in the receiver and includes antenna gain and transmission line and propagation losses.	System Gain

Complete List of Reviewers in Electronic Communications System per Chapter

Reviewer in Electronic Communications System by Wayne Tomasi

Important List of Communications Engineering Materials

Communications Engineering Coaching Materials

Series of Communications Engineering Exams: ECE Pre-Board

Series of Questions and Answers in Communications Engineering

Multiple Choice Questions in Data Communications and Networking

---