Analogue And Digital Systems Computer Science Essay

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Analogue systems process analogue signals which are able to process any value within a reasonable range, for example the output from an LDR light sensor or a microphone.

An example of an analogue system is an audio amplifier. The amplifier produces an output voltage which can be any value within the range of its power supply.

An analogue signal is characterized by being continuously variable along amplitude and frequency. In the case of telephony, for instance, when you speak into a handset, there are changes in the air pressure around your mouth. Those changes in air pressure fall onto the handset, where they are amplified and then converted into current, or voltage fluctuations. Those fluctuations in current are an analogue of the actual voice pattern. All electronic circuits suffer from 'noise' which is unwanted signal mixed in with the desired signal, for example an audio amplifier may pick up some mains 'hum' (the 50Hz frequency of the UK mains electricity supply). Noise can be difficult to eliminate from analogue signals because it may be hard to distinguish from the desired signal.

Analogue signal

(ii). Digital signal

Digital systems process digital signals which can take only a limited number of values (discrete steps); usually just two values are used: the positive supply voltage (+Vs) and zero volts (0V).

Digital systems contain devices such as logic gates, flip-flops, shift registers and counters. A computer is an example of a digital system.

Digital signal typically require a large number of mathematical operations to be performed quickly on a set of data. Signals are converted from analogue to digital, manipulated digitally, and then converted again to analogue form, as diagrammed below. Many DSP applications have constraints on latency; that is, for the system to work, the DSP operation must be completed within some time constraint.

Digital (logic) signal

(B). There are 3 types of transmissions:

(i). Coaxial cable:

Coaxial cable: an electrical cable with an inner conductor surrounded by a tubular insulating layer mostly of a flexible material with a high dielectric constant, all of these are surrounded by a conductive layer which is of fine woven wire for flexibility, or of a thin metallic foil, and finally the coaxial cable is covered by a thin insulating layer on the outside. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis.

Coaxial cable is used a lot as a transmission line for radio frequency signals, in applications such as connecting radio transmitters and receivers with their antennas, computer network (Internet) connections, and distributing cable television signals.

An advantage of coaxial cables over other different types of transmission lines is that in a perfect coaxial cable the electromagnetic field carrying the signal exists only in the space between the inner and outer conductors. This gives coaxial cable runs to be installed next to metal objects such as gutters without the power losses that do occur in other transmission lines, and provides protection of the signal from external electromagnetic interference.

(ii). Optical fibres:

An optical fibre: a glass or plastic fibre that carries light along its length. Fibre optics is the overlap of applied science and engineering concerned with the design and application of optical fibres. Optical fibres are widely used in fibre-optic communications, which allows transmission over further distances at higher bandwidths rather than other forms of communications. Fibres are used instead of metal wires as signals travel along them without losing loss, and they are also immune to electromagnetic interference. Fibres are also used for illumination, and are wrapped in bunches so they can be used to carry images.

(iii). Wireless Links:

Wireless communication is the transfer of information over a distance without the use of electrical conductors or "wires". The distances involved may be short (a few meters as in television remote control) or long (thousands or millions of kilometres for radio communications). When the context is clear, the term is often shortened to "wireless". Wireless communication is generally considered to be a branch of telecommunications.

Common examples of wireless equipment in use today include:

Satellite television: allows viewers in almost any location to select from hundreds of channels.

Wireless gaming: new gaming consoles allow players to interact and play in the same game regardless of whether they are playing on different consoles. Players can chat, send text messages as well as record sound and send it to their friends. Controllers also use wireless technology. They do not have any cords but they can send the information from what is being pressed on the controller to the main console which then processes this information and makes it happen in the game. All of these steps are completed in milliseconds.

Wireless networking (i.e. the various types of unlicensed 2.4 GHz Wi-Fi devices) is used to meet many needs. Perhaps the most common use is to connect laptop users who travel from location to location. Another common use is for mobile networks that connect via satellite. A wireless transmission method is a logical choice to network a LAN segment that must frequently change locations. The following situations justify the use of wireless technology.

Wireless communication can be via: Radio frequency communication,

Task 2:

Level shifting:

A communication system including at least one controller for enabling a plurality of radio systems to communicate over a packet network, each radio system communicating one of at least two different radio signals transmitted using different radio-protocols, the communication system comprising: a plurality of gateways adapted to communicate over an IP link using a generic IP data packet protocol having a component for storing audio signals and a component for storing radio control signals; for each radio signal of the at least two radio signals: at least one gateway of the plurality of gateways converting audio and control protocol signals in the radio protocols to and from audio and control components of the generic IP data packet protocol for at least one radio system that communicates using the radio signal; and where in the component of the generic IP data packet protocol for storing radio control signals is configured to store at least one event selected from a group consisting of: activating a transmitter in a radio station; releasing a transmitter in a radio station; tuning a transmitter in a radio station to a specific RF channel; switching a receiver in a radio station to a specific RF channel; and monitoring the carrier status of a radio station.

In the component of the generic IP data packet protocol for storing radio control signals is configured to store at least one events selected from a group consisting of: sending a data packet to a specific subscriber unit via a radio station; receiving a data packet from a specific subscriber unit via a radio station; and sending a paging alert tone to a specific subscriber unit via a radio station.

An analogue-to-digital interfacing conversion

an input selector receiving at least one analogue signal and selectively outputting the at least one analogue signal based on a plurality of clock signals; an analogue-to-digital converter converting the at least one analogue signal output from the selector to at least one digital signal; a plurality of registers; and an output selector receiving each digital signal output from the analogue-to-digital converter and selectively routing the digital signal to one of the plurality of registers based on the plurality of clock signals, wherein the input selector includes at least one first logic controlled gate, each first logic controlled gate receiving one of the at least one analogue signal and selectively outputting the received analogue signal to the analogue-to-digital converter based on the plurality of clock signals.

Analogue to digital converters provide the link between analogue and digital domains. The ADC is required to be capable of converting analogue data to digital data in an accurate manner, appropriate to the bandwidth and resolution requirements of particular application. Analogue ICs often require the use of, and constantly consume, a DC bias current. Digital integrated circuits are ICs which process digital signals. A/D converters are designed to process analogue signals over a specified range of analogue signal values.

(B). Types of different transmission media:

Transmission Media Types

The most common type of media is copper cable. The most common types of copper cabling are twisted-pair and coaxial. Twisted-pair cabling used in a LAN is similar to the cabling used to connect your telephone to the wall outlet. Network coaxial cabling, on the other hand, is similar to the cable used to connect your television set to the cable TV outlet.

Another type of LAN connection media quickly gaining popularity is fibre-optic cable. Consisting of a number of glass or high-grade plastic optical strands surrounded by a tough cloth-and-plastic wrap, fibre-optic cables resemble coaxial cables from the outside. Fibre-optic network cabling is similar to the fibre-optic strand used in the fibre-optic lamps found in novelty stores, in which coloured lights feed into optical strands to create the appearance of dozens of pinpoints of light.

Wireless media, which is, in a sense, no media at all, is also gaining popularity. Wireless transmissions use radio waves or infrared light to transmit data. Many major network vendors now offer wireless network adapters.

Task 3:

A (I). Analogue to digital

A device for converting the information contained in the value or magnitude of some characteristic of an input signal, compared to a standard or reference, to information in the form of discrete states of a signal, usually with numerical values assigned to the various combinations of discrete states of the signal.

Analogue to digital conversion, the process whereby an ANALOGUE SIGNAL such as a voice recording consisting of continuously varying waves is converted into a binary DIGITAL SIGNAL. This is carried out by splitting the signal into a series of exact values represented by a binary number, a process called QUANTIZATION.

(1) Processing by a computer or by logic circuits, including arithmetical operations, comparison, sorting, ordering, and code conversion,

(2) Storage until ready for further handling,

(3) Display in numerical or graphical form, and

(4) Transmission.

(ii). Digital to analogue

Digital-to-analogue conversion is a process in which signals having a few (usually two) defined levels or states (digital) are converted into signals having a theoretically infinite number of states (analogue). A common example is the processing, by a modem, of computer data into audio-frequency (AF) tones that can be transmitted over a twisted pair telephone line. The circuit that performs this function is a digital-to-analogue converter (DAC).

In digital transmission the signals are converted into a binary code, which consists of two elements-positive and non-positive. Morse code and the "on and off" flashing of a light are basic examples. Positive is expressed as the number 1, while non-positive is expressed as the number 0. Numbers that are expressed as a string of 0s and 1s are called binary numbers. Every digit in a binary number is referred to as a bit and represents a power of two. For example, in the binary number 101, the 1 at the right represents 1 x 2°; the 0 in the middle represents 0 x 2¹; and the 1 to the far left represents 1 x 2². The decimal equivalent of 101 is (1 x 2²) + (0 x 2¹) + (1 x 2°) = 4 + 0 + 1 = 5. In a standard code used by most computers, the letter "A" is expressed in 8 bits as 01000001.

As an example of digital transmission, in a type of digital telephone system, coded light signals produced by a rapidly flashing laser travels through optical fibres (thin strands of glass) and are then decoded by the receiver. When transmitting a telephone conversation, the light flashes on and off about 450 million times per second. This high rate enables two optical fibres to carry about 15,000 conversations simultaneously. instances when a DAC is placed after an ADC, the analogue signal output is identical to the analogue signal input.

Binary digital impulses, all by themselves, appear as long strings of ones and zeros, and have no apparent meaning to a human observer. But when a DAC is used to decode the binary digital signals, meaningful output appears. This might be a voice, a picture, a musical tune, or mechanical motion.

Serial to parallel output conversion

A process of converting a set of parallel input data bits received from a data converter into a serial format, said process comprising the steps of:

providing a set of serial interface input signals, said set of serial interface input signals comprising, an input clock signal, a chip select signal, an internal data conversion status signal and, said set of parallel input data bits and, detecting said signal status of said chip select signal and said internal date conversion status signal, wherein said serial interface provides said received set of parallel input data bits as a set of serial data output bits in synchronization to said clock signal upon detecting an unasserted state of said chip select signal in combination with an unasserted state of said internal conversion status signal.

A serial interface process to provide one or more set of serial data output bits, said process comprising the steps of: receiving a set of input signals, said input signals comprising an input clock signal, a chip select signal, an internal data conversion status signal and, said set of parallel input data bits, detecting a first serial data output ready state comprising the steps of, detecting an unasserted state of said chip select signal, detecting an unasserted state of said internal data conversion status signal, detecting an asserted state of said chip select signal and, in response thereto, providing said received set of parallel input data bits as a set of serial data output bits in synchronization with said clock signal.

A process of converting a set of input data bits comprising the steps of: providing a set of input signals comprising, a chip select signal, an internal data conversion status signal and, said set of input data bits, detecting a signal status of said chip select signal and said internal data conversion status signal and, providing a set of data output bits as a function of said set of input data bits in synchronization with said clock signal upon detecting an unasserted state of said chip select signal in combination with an unasserted state of said internal data conversion status signal.

An interface process to provide one or more set of data output bits, said process comprising the steps of: receiving a set of input signals comprising, an input clock signal, a chip select signal, an internal data conversion status signal and, a set of input data bits detecting a first data output ready state comprising the steps of: an unasserted state of said chip select signal, detecting an unasserted state of said internal data conversion status signal and, detecting an asserted state of said chip select signal.

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