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ECE141 > Chapter 5 > Flashcards

Chapter 5 Flashcards

1
Q

The reverse process of AM modulation.

A

AM Demodulation

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2
Q

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

A

RF Section

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3
Q

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

A

Mixer /

Converter

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4
Q

This section primary functions are amplification and selectivity.

A

IF Section

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5
Q

This section demodulates the AM wave and converts it to the original information signal.

A

AM Detector

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6
Q

This section amplifies the recovered information. Comprises several cascaded audio amplifiers and one or more speakers.

A

Audio Section

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7
Q

A receiver parameter that is used to measure the ability of the receiver to accept a given band of frequencies and reject all others.

A

Selectivity

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8
Q

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

A

Shape Factor

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9
Q

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

A

Thermal Noise

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10
Q

Noise reduction ratio achieved by reducing the Bandwidth.

A

Bandwidth Improvement

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11
Q

The corresponding reduction in the noise figure due to the reduction in bandwidth expressed mathematically in dB.

A

Noise Figure Improvement

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12
Q

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.

A

Sensitivity

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13
Q

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.

A

Dynamic Range

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14
Q

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

A

1-dB Compression Point

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15
Q

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.

A

Fidelity

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16
Q

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

A

Distortion

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17
Q

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.

A

Absolute Phase Shift

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18
Q

Occurs when different frequencies undergo different phase shifts and have a detrimental effect on a complex waveform.

A

Differential Phase Shift

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19
Q

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.

A

Insertion Loss

IL

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20
Q

A hypothetical value that cannot be directly measured. A parameter that is used in low-noise, sophisticated radio receivers rather than noise figure.

A

Equivalent Noise Temperature

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21
Q

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

A

Coherent /

Synchronous Receiver

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22
Q

Either no frequencies are generated in the receiver or the frequencies used for demodulation are completely independent from the transmitter’s carrier frequency.

A

Noncoherent /

Asynchronous Receiver

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23
Q

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

A

Tuned Radio Frequency

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24
Q

A phenomenon at radio frequencies where current flow is limited to the outermost area of a conductor.

A

Skin Effect

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25
Q

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.

A

Stagger Tuning

26
Q

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

A

Heterodyne

27
Q

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

A

Preselector

28
Q

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

A

455 kHz

29
Q

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

A

IF Section

30
Q

Refer to frequencies that are used within a transmitter or receiver that fall somewhere between the radio frequencies and the original source information frequencies.

A

Intermediate Frequency

31
Q

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.

A

Gang Tuning

32
Q

When the local oscillator is tuned above

the RF it is?

A

High-side Injection /

High-beat Injection

33
Q

When the local oscillator is tuned below

the RF it is?

A

Low-side Injection /

Low-beat Injection

34
Q

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

A

Sideband Inversion

35
Q

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.

A

Tracking

36
Q

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

A

Tracking Error

37
Q

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.

Unwanted frequency

A

Image Frequency

38
Q

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

A

Image-frequency Rejection Ratio

39
Q

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

A

Double Spotting

40
Q

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

A

RF Amplifier

41
Q

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

A

Low-noise Amplifier

LNA

42
Q

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

A

MEsa Semiconductor FET Semiconductor FET

MESFET

43
Q

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

A

NE / SA5200

44
Q

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

A

Mixer /

Converter Stage

45
Q

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.

A

Conversion Gain

46
Q

A configuration where the mixer excites itself by feeding energy back to the local oscillator tank circuit to sustain oscillations noise figure.

A

Self-excited Mixer

47
Q

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

A

NE / SA602A

48
Q

Are relatively high-gain amplifiers that are very similar to RF amplifiers, except that IF amplifiers operate over a relatively narrow, fixed frequency band.

A

Intermediate Frequency

( IF ) Amplifier

49
Q

Is caused by the reactive element of the reflected impedance being significant enough to change the resonant frequency of the primary tuned circuit.

A

Double Peaking

50
Q

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

A

Optimum Coupling

51
Q

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

A

IF Cans

52
Q

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

A

AM Detector

53
Q

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

A

Peak Detector

54
Q

A distortion in the detection process where the RC time constant is too short, the output waveform resembles a half-wave rectified signal.

A

Rectifier Distortion

55
Q

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.

A

Diagonal Clipping

56
Q

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

A

Automatic Gain Control

AGC

57
Q

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

A

Delayed AGC

58
Q

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.

A

Forward AGC

59
Q

Are used to remove sporadic, high-amplitude noise transients of short duration, such as impulse noise in the audio section of a receiver.

A

Limiters /

Clippers

60
Q

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

A

PLL Receivers

61
Q

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.

A

Net Receiver Gain

ECE141 (3 decks)

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