Flashcards in Chapter 5 Deck (61):
The reverse process of AM modulation.
The first stage of the receiver of which primary functions are detecting, band limiting, and amplifying the received.
This section down-converts the received RF frequencies to intermediate frequencies (IFs).
This section primary functions are amplification and selectivity.
This section demodulates the AM wave and converts it to the original information signal.
This section amplifies the recovered information. Comprises several cascaded audio amplifiers and one or more speakers.
A receiver parameter that is used to measure the ability of the receiver to accept a given band of frequencies and reject all others.
The ratio of the bandwidth 60dB below maximum signal level and bandwidth 3dB below maximum signal level.
The most prevalent form of noise and is directly proportional to bandwidth.
Noise reduction ratio achieved by reducing the Bandwidth.
The corresponding reduction in the noise figure due to the reduction in bandwidth expressed mathematically in dB.
Noise Figure Improvement
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.
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.
Defined as the output power when the RF amplifier response is 1 dB less than the ideal linear-gain response.
1-dB Compression Point
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.
Any frequency, phase, or amplitude variations that are present in the demodulated waveform that were not in the original information signal.
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
Occurs when different frequencies undergo different phase shifts and have a detrimental effect on a complex waveform.
Differential Phase Shift
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.
( IL )
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
The frequencies generated in the receiver and used for demodulation are synchronized to oscillator frequencies generated in the transmitter.
Either no frequencies are generated in the receiver or the frequencies used for demodulation are completely independent from the transmitter’s carrier frequency.
One of the earliest types of AM receivers and are probably the simplest designed radio receivers available today.
Tuned Radio Frequency
A phenomenon at radio frequencies where current flow is limited to the outermost area of a conductor.
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.
Means to mix two frequencies together in a nonlinear device or to translate one frequency to another using nonlinear mixing.
A broad –tuned bandpass filter with an adjustable center frequency that is tuned to desired carrier frequency.
The most common intermediate frequency used in AM broadcast-band receivers is ________.
Consists of a series of IF amplifiers and bandpass filters and is often called IF strip.
Refer to frequencies that are used within a transmitter or receiver that fall somewhere between the radio frequencies and the original source information frequencies.
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.
When the local oscillator is tuned above
the RF it is?
High-side Injection /
When the local oscillator is tuned below
the RF it is?
Low-side Injection /
The side frequencies undergo a sideband reversal during the heterodyning process called?
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.
The difference between the actual oscillator frequency and the desired frequency.
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.
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.
A high-gain, low-noise, tuned amplifier that, when used, is the first active stage encountered by the received signal.
High-performance microwave receivers require a ________ as the input stage of the RF section to optimize their noise figure.
( LNA )
A FET with a metal-semiconductor junction at the gate of the device, called a Schottky barrier.
MEsa Semiconductor FET Semiconductor FET
( MESFET )
A wideband, unconditionally stable, low-power, dual-gain linear integrated-circuit RF amplifier manufactured by Signetics Corporation.
NE / SA5200
This section purpose is to down-convert the incoming radio frequencies to intermediate frequencies proportional to bandwidth.
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 configuration where the mixer excites itself by feeding energy back to the local oscillator tank circuit to sustain oscillations noise figure.
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.
( IF ) Amplifier
Is caused by the reactive element of the reflected impedance being significant enough to change the resonant frequency of the primary tuned circuit.
The coefficient of coupling approximately 50% greater than the critical value yields a good compromise between flat response and steep skirts.
IF transformers come as specially designed tuned circuits in groundable metal packages
The function of this circuit is to demodulate the AM signal and recover or reproduce the original source information.
A simple noncoherent AM demodulator using a diode. Also called as diode, shape, or envelope detector.
A distortion in the detection process where the RC time constant is too short, the output waveform resembles a half-wave rectified signal.
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 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.
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.
Are used to remove sporadic, high-amplitude noise transients of short duration, such as impulse noise in the audio section of a receiver.
This receivers would need only two external components: a volume control and a station tuning control.