Principles of Communication Systems PDF

Principles of Communication Systems Communication System BS Electrical Engineering Engr. Christopher V. Maglaque, MEM, PECE Associate Professor 4  Allocation: Entry in the Table of Frequency Allocations of a given frequency band for the purpos...

Principles of Communication Systems Communication System BS Electrical Engineering Engr. Christopher V. Maglaque, MEM, PECE Associate Professor 4  Allocation: Entry in the Table of Frequency Allocations of a given frequency band for the purpose of its use by one or more terrestrial or space radio communication services or the radio astronomy service under specified conditions. Allotment: Communication Entry of a designated frequency channel in the agreed plan, adopted by the ITU, for use by one or more nations for a System terrestrial or space radio communication services in one or more identified countries or geographic areas and under specified conditions. Assignment: Authorization given by a nation for a radio station to use a radio-frequency channel under specified conditions.  Electromagnetic Spectrum The electromagnetic spectrum illustrates the range of frequencies applicable to electronic communication. Figure 1.9a shows the entire electromagnetic spectrum and Figure 1.9b shows the description of each spectrum. The electromagnetic waves are signals that oscillates. It consists of electric field and magnetic field. It is also characterized by its Communication amplitude, frequency or phase. System Figure 1.9a: Electromagnetic Spectrum  Electromagnetic Spectrum FREQUENCY RANGE DESIGNATIONS 30 Hz to 300 Hz ELF (Extremely Low Frequencies) 300 Hz to 3 kHz VF (Voice Frequencies) 3 kHz to 30 kHz VLF (Very Low Frequencies) 30 kHz to 300 kHz LF (Low Frequencies) Communication 300 kHz to 3 MHz MF (Medium Frequencies) System 3 MHz to 30 MHz 30 MHz to 300 MHz HF (High Frequencies) VHF (Very High Frequencies) 300 MHz to 3 GHz UHF (Ultra High Frequencies) 3 GHz to 30 GHz SHF (Super High Frequencies) 30 GHz to 300 GHz EHF (Extremely High Frequencies) 300 GHz to 300 THz Infrared Light 300 THz to 3 PHz Visible Light 3 PHz to 30 PHz Ultraviolet Light 30 PHz to 300 PHz X Rays 300 PHz to 3 EHz Gamma Rays 3EHz to 30 EHz Cosmic rays  It can be observed that the range of the electromagnetic spectrum is defined by its frequency and wavelength. Frequency is the number of cycles that occur in one second (Hertz) while wavelength is the length travelled by one cycle in meters. Figure 1.10a and Figure 1.10b shows an illustration of frequency and wavelength. Communication System Figure 1.10a: Frequency of a wave Figure 1.10b: Wavelength of a wave  WAVEFORM REPRESENTATION 1. Time Domain Representation A standard oscilloscope is used to display the amplitude versus time representation of the input signal Communication System  i. Frequency (f) The number of times a particular phenomenon occurs in a given period of time expressed in Hertz. ii. Wavelength (λ) Communication Wavelength is the distance between two points of similar System cycles of a periodic wave or the distance traveled by an electromagnetic wave during the time of one cycle typically expressed in meters. iii. Period (T) The time required for one complete cycle of a repetitive system, or simply the reciprocal of frequency.  Relation between Wavelength, Frequency, and Period Communication where: System λ=wavelength in meters c=speed of light (3x108) f=frequency in Hz T=period in sec  SAMPLE PROBLEMS: 1. Determine the wavelength of radio waves propagated using a frequency of 30 MHz. Communication System 2. If the measured wavelength is 6m, calculate the frequency in MHz.  Example: Find the wavelength of the following frequency: a. 97.1 MHz b. 590 kHz c. 107.5 MHz d. 2.2 GHz Solutions: ! The relationship between wavelength (λ) to frequency is 𝜆 = Communication " System  2. Frequency Domain Representation A spectrum analyzer is used to display the amplitude versus frequency representation of the input signal. Communication System The time and frequency domain representation of three sine waves  Bandwidth (BW) Bandwidth refers to the range of frequency in an electromagnetic spectrum. It is the difference between the highest frequency available in the spectrum to the lowest frequency. 𝑩𝑾 = 𝒇𝟐 − 𝒇𝟏 A channel bandwidth refers to the portion of electromagnetic Communication spectrum occupied by the modulated signal. Commonly it refers to the sidebands of the modulated signal. Figure 1.11 illustrate the System bandwidth of the voice frequency (VF) spectrum. Figure 1.11: Bandwidth of voice frequency spectrum  Example: 1. Determine the bandwidth of high frequency spectrum. Communication System  Example: Television has a 6 MHz bandwidth. Determine the lower side frequency of channel 2 if the higher frequency is 60 MHz Communication System  TRANSMISSION FACILITIES In terms of bandwidth, and in a contemporary digital context, transmission facilities can be categorized as narrowband, wideband, or broadband. 1. Narrowband A single channel (64 Kbps) or some number of 64 Kbps channels (N Communication ×64 Kbps), but less than wideband. System 2. Wideband Wideband is a multi-channel capacity that is between 1.544 Mbps and 45 Mbps according to U.S. standards (2.048 Mbps-34 Mbps according to European/international standards.) 3. Broadband Broadband is a multi-channel capacity which is 45 Mbps according to U.S. standards and 34 Mbps according to European/international standards.  TRANSMISSION IMPAIRMENTS. Signals travel through transmission media, which are not perfect. The imperfection causes signal impairment. This means that the signal at the beginning of the medium is not the same as Communication the signal at the end of the medium. What is sent is not what is received. Three causes of impairment are attenuation, distortion, System and noise. 1. Attenuation 2. Distortion 3. Noise  1. Attenuation Type of transmission impairment in which the signal loses strength due to the resistance and length of the transmission medium. Communication System  2. Distortion The alteration of information in which the original proportions are changed, resulting from a defect in communication system Communication System  3. Noise Type of transmission impairment in which an outside source such as crosstalk corrupts a signal. Communication System  CLASSIFICATION OF COMMUNICATIONS 1. Distress A mobile station in distress is in-need of immediate assistance. 2. Urgency Communication Radio messages with an urgency classification refer to a System situation that requires immediate attention and might conceivably become distress in nature. 3. Safety Radio communications with a safety classification refer to meteorological information, particularly about storms, hurricanes, etc.  MESSAGE PRIORITIES 1. Distress calls, messages, and traffic 2. Communications preceded by the urgency signal Communication 3. Communications preceded by the safety signal System 4. Communications relative to radio direction finding 5. Message relative to navigation of aircraft 6. Message relative to navigation, movements, and needs of ships and official weather-observation messages  OPERATIONAL WORDS CODE MEANING Roger I received your message. I have completed transmitting and await your Over reply. Go ahead Same as over. Communication Out I have completed my communication and do not expect to transmit again. System I have no further traffic. (Sometimes Clear used in place of Out) Wait for another call or further Stand by instructions. I am changing from one part of the message to another. (Also used to request the received operator to indicate Break if he has received the portion of the message transmitted thus far.) Copy Respond to Break  INTERNATIONAL PHONETIC ALPHABET Communication System Communication System QUESTIONS??? Communication THANK YOU & GOD BLESS System STAY SAFE!!!