The signals of a digital transmission could be

The original source information may be in digital form, or it could be analog signals that have been converted to digital pulses prior to receiver and converted back to analog signals in the trasmitter

With digital transmission systems, these are required to interconnect the various points within the system

Digital pulses cannot be propagated through a wireless transmission

system, such as

developed the first digital transmission system for the purpose of carrying digitally

encoded analog signals, such as the human voice, over metallic wire cables between

telephone offices

Digital transmission systems use _____ and ____ for their transmission medium

Advantages of Digital Transmission

is the processing of analog signals using digital methods and includes bandlimiting the signal with filters, amplitude equalization, and phase shifting

Disadvantages of Digital Transmission

consists essentially of sampling analog information signals and then converting those samples into discrete pulses and transporting the pulses from a source to a destination over a physical transmission medium

The four predominant methods of pulse

modulation include

PWM is sometimes called

as the width (active portion of the duty cycle) of a constant amplitude pulse

is varied proportional to the amplitude of the analog signal at the time the signal is sampled

the position of a constant-width pulse within a prescribed time slot is varied according to the amplitude of the sample of the analog signal

the amplitude of a constant width, constant-position pulse is varied according to the amplitude of the sample of the analog signal

the analog signal is sampled and then converted to a serial n-bit binary code for transmission

used as an intermediate form of modulation with PSK, QAM, and PCM, although it is seldom used by itself

are used in special-purpose communications systems mainly for the military but are seldom used for commercial digital transmission systems

is by far the most prevalent form of pulse modulation

is credited with inventing PCM in 1937 while working for AT&T at its Paris laboratories

is the preferred method of communications within the public switched telephone network because with it, it is easy to combine digitized voice and digital data into a single, high-speed digital signal and propagate it over either metallic or optical fiber cables

is somewhat of a misnomer, as it is not really a type of modulation but rather a form of digitally coding analog signals

is a binary system where a pulse or lack of a pulse within a prescribed time slot represents either a logic 1 or a logic 0 condition

are digital but seldom binary, as a pulse

does not represent a single binary digit (bit)

limits the frequency of the analog input signal to the standard voice-band frequency range of 300 Hz to 3000 Hz

periodically samples the analog input signal and converts those samples to a multilevel PAM signal

________ converts the PAM samples to parallel PCM codes, which are converted to serial binary data in the ________ and then outputted onto the transmission line as serial digital pulses

are placed at prescribed distances to regenerate the digital pulses

converts serial pulses received from

the transmission line to parallel PCM codes

converts the parallel PCM codes to multilevel PAM signals

is basically a lowpass filter that converts the PAM signals back to its original analog form

An integrated circuit that performs the PCM encoding and decoding functions is called

there are two basic techniques used to perform the sampling function:

natural sampling and flat-top sampling

is when tops of the sample pulses retain their natural shape during the sample interval, making it difficult for an ADC to convert the sample to a PCM code

The most common method used for sampling voice signals in PCM systems

its purpose is to periodically sample the continually changing analog input voltage and convert those samples to a series of constant-amplitude PAM voltage levels

when the amplitude of the sampled signal changes during the sample pulse time

Flat-top sampling introduces more aperture distortion than natural sampling and can operate with a slower analog-to-digital converter

Nyquist sampling theorem

is a nonlinear device (mixer) with two inputs: the sampling pulse and the analog input signal

occurs between the sampling pulse and the analog input signal

nonlinear mixing is also called as

The frequency that folds over

Its upper cutoff frequency is chosen such that no frequency greater than one-half the sampling rate is allowed to enter the sample-and-hold circuit, thus eliminating the possibility of foldover distortion occurring

The binary codes used for PCM

The codes currently used for PCM

sign bit

is the process of converting an infinite number of possibilities to a finite number of conditions

The magnitude difference between adjacent steps

If the magnitude of the sample exceeds the highest quantization interval ______, occurs

Assigning PCM codes to absolute magnitudes is called

The magnitude of a quantum is also called the

The resolution is equal to the voltage of the minimum step size, which is equal to the voltage of the least significant bit (Vlsb) of the PCM code

is equivalent to additive white noise as it alters the signal amplitude

quantization error is also called quantum noise

The maximum magnitude for the quantization error is equal to

is the ratio of the largest possible magnitude to the smallest possible magnitude (other than 0 V) that can be decoded by the digital-to-analog converter in the receiver

Dynamic Range

number of bits

is a numerical indication of how efficiently a PCM code is utilized

the magnitude change between any two successive codes is the same

occurs when the input signal is at its minimum amplitude

This type of coding compares the PAM signal to a ramp waveform while a binary counter is being advanced at a uniform rate

This type of coding determines each digit of the PCM code sequentially, also analogous to balance

are flash encoders and are more complex; however, they are more suitable for high-speed applications

With this type of coder, the entire PCM code word is

determined simultaneously. Also uses a successive

approximation register (SAR)

is the process of compressing and then expanding

Companding is a means of improving the resolution of a communications system

this companding is used in the United States and Japan

to be used to approximate true logarithmic companding and used in Europe

involves compression in the transmitter after the input sample has been converted to a linear PCM code and then expansion in the receiver prior to PCM decoding

Most of the more recently developed

codecs are called combo chips

uses a single-bit PCM code to achieve digital transmission of analog signals

The slope of the analog signal is

less than the delta modulator can maintain and is called slope overload

when the original analog input signal has a relatively constant amplitude, the reconstructed signal has variations that were not present in the original signal

Slope overload is more prevalent in analog signals that have gradual slopes and whose amplitudes vary only a small amount.

Granular noise is more prevalent in analog signals that have steep slopes or whose amplitudes vary rapidly

is a delta modulation system where the step size of the DAC is automatically varied, depending on the amplitude characteristics of the analog input signal

designed specifically to take advantage of the sample-to-sample redundancies in typical speech waveforms

All digital carrier systems involve the transmission of pulses through a medium with an infinite bandwidth

The secondary lobes are called ringing tails

The four primary causes of ISI

occurs when the peaks of pulses are reduced, causing improper ringing frequencies in the time domain

is a convenient technique for determining the effects of the degradations introduced into the pulses as they travel to the regenerator