Amplitude Modulation Reception (Chapter 5) Flashcards by Gerund Juan

The reverse process of AM modulation.

AM Demodulation

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The first stage of the receiver of which primary functions are
detecting, band limiting, and amplifying the received.

RF Section

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This section down-converts the received RF frequencies to
intermediate frequencies (IFs).

Mixer / Converter

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This section primary functions are amplification and

selectivity.

IF Section

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This section demodulates the AM wave and converts it to the

original information signal.

AM Detector

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This section amplifies the recovered information. Comprises

several cascaded audio amplifiers and one or more speakers.

Audio Section

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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

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The ratio of the bandwidth 60dB below maximum signal level and
bandwidth 3dB below maximum signal level.

Shape factor

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The most prevalent form of noise and is directly proportional
to bandwidth.

Thermal noise

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Noise reduction ratio achieved by reducing the Bandwidth.

Bandwidth Improvement

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The corresponding reduction in the noise figure due to the

reduction in bandwidth expressed mathematically in dB.

Noise Figure Improvement

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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

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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

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Defined as the output power when the RF amplifier response is
1 dB less than the ideal linear-gain response.

1-dB Compression Point

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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

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Any frequency, phase, or amplitude variations that are present
in the demodulated waveform that were not in the original information signal.

Distortion

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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

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Occurs when different frequencies undergo different phase

shifts and ay have a detrimental effect on a complex waveform.

Differential Phase Shift

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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

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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

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The frequencies generated in the receiver and used for
demodulation are synchronized to oscillator frequencies generated in the
transmitter.

Coherent / Synchronous Receiver

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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

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One of the earliest types of AM receivers and are probably the
simplest designed radio receivers available today.

Tuned Radio Frequency

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A phenomenon at radio frequencies where current flow is

limited to the outermost area of a conductor.

Skin Effect

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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

Means to mix two frequencies together in a nonlinear device or to translate one frequency to another using nonlinear mixing.

Heterodyne

A broad –tuned bandpass filter with an adjustable center | frequency that is tuned to desired carrier frequency.

Preselector

The most common intermediate frequency used in AM | broadcast-band receivers is ________.

455 kHz

Consists of a series of IF amplifiers and bandpass filters and is often called IF strip.

IF Section

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

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

When the local oscillator is tuned above the RF it is?

High-side Injection / High-beat Injection

When the local oscillator is tuned below the RF it is?

Low-side Injection / Low-beat Injection

The side frequencies undergo a sideband reversal during the | heterodyning process called?

Sideband Inversion

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

The difference between the actual oscillator frequency and the desired frequency.

Tracking Error

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

A numerical measure of the ability of a preselector to reject the image frequency.

Image-frequency Rejection Ratio

Occurs when a receiver picks up the same station at two nearby points on the receiver tuning dial.

Double Spotting

high-gain, low-noise, tuned amplifier that, when used, is | the first active stage encountered by the received signal.

RF Amplifier

High-performance microwave receivers require a ________ as the input stage of the RF section to optimize their noise figure.

Low-noise Amplifier ( LNA )

A FET with a metal-semiconductor junction at the gate of the | device, called a Schottky barrier.

MEsa Semiconductor FET Semiconductor FET ( | MESFET )

This section purpose is to down-convert the incoming radio | frequencies to intermediate frequencies proportional to bandwidth.

Mixer / Converter Stage

A wideband, unconditionally stable, low-power, dual-gain | linear integrated-circuit RF amplifier manufactured by Signetics Corporation

NE / SA5200

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

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

A low-power VHF monolithic double-balanced mixer with input | amplifier, on-board oscillator, and voltage regulator.

NE / SA602A

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

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

Ability of a coil to induce a voltage within its windings.

Inductance

Ability of one coil to induce a voltage in another coil.

Mutual Inductance

The ratio of the secondary flux to the primary flux.

Coefficient of Coupling

The transfer of flux from the primary to the secondary | windings and is directly proportional to the coefficient of coupling.

Flux Linkage

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

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

The coefficient of coupling approximately 50% greater than the critical value yields a good compromise between flat response and steep skirts.

Optimum Coupling

IF transformers come as specially designed tuned circuits in | groundable metal packages called _______.

IF Cans

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

The function of this circuit is to demodulate the AM signal | and recover or reproduce the original source information.

AM Detector

A simple noncoherent AM demodulator using a diode. Also called as diode, shape, or envelope detector.

Peak Detector

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

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

A circuit that compensates for minor variations in the | received RF signal.

Automatic Gain Control | AGC

It prevents the AGC feedback voltage from reaching the RF or | IF amplifiers until the RF level exceeds a predetermined magnitude.

Delayed AGC

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

Its purpose is to quiet a receiver in the absence of a | received signal.

Squelch Circuit

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

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

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

This receivers would need only two external components: a | volume control and a station tuning control.

PLL Receivers

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

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