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Components of a satellite communication system transponder
The document discusses the key subsystems of a communication satellite. It describes the transponder as the interconnected units that form a communication channel between the satellite's receiving and transmitting antennas. The main subsystems include the communication payload containing transponders, antennas, and switching systems; engines to reach the desired orbit; station keeping, tracking, and stabilization to maintain the correct orbit and antenna positioning; and a power subsystem using solar cells and batteries. The document then focuses on the structure and function of a transponder, including its input band-limiting filter, low-noise amplifier, frequency translator using an oscillator and mixer, output filter, and power amplifier.
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Components of a satellite communication system transponder
- 1. STRUCTURE OF COMMUNICATION SATELLITE: TRANSPONDER G O M 2 2 1 IFFAT ARA D E P T . O F G E O M A T I C S
- 2. SUBSYSTEM STRUCTURE • CommunicationPayload, normally composed of transponders, antennas, and switching systems • Engines used to bring the satellite to its desired orbit • Station Keeping Tracking and stabilization subsystem used to keep the satellite in the right orbit, with its antennas pointed in the right direction, and its power system pointed towards the sun • Power subsystem, used to power the Satellite systems, normally composed of solar cells, and batteries that maintain power during solar eclipse • Command and Control subsystem, which maintains communications with ground control stations. The ground control Earth stations monitor the satellite performance and
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- 4. A communications satellite'stransponder is the series of interconnected units that form a communications channel between the receiving and the transmitting antennas. It is mainly used in satellite communication to transfer the received signals
- 5. COMPOSITION OF ATRANSPONDER an input band-limiting device (a input band-pass filter), an input low-noise amplifier (LNA), designed to amplify the (normally very weak, because of the large distances involved) signals received from the Earth station a frequency translator (normally composed of an oscillator and a frequency mixer) used to convert the frequency of the received signal to the frequency required for the transmitted signal, an output band-pass filter a power amplifier (this can be a traveling-wave tube or a solid- state amplifier)
- 6. BAND-PASS FILTER System levelblock diagram of a band-pass filter.
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- 9. LNA A low-noise amplifier(LNA) is an electronic amplifier that amplifies a very low-power signal without significantly degrading its signal-to-noise ratio. An amplifier increases the power of both the signal and the noise present at its input. LNAs are designed to minimize additional noise.
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- 13. PARAMETERS OF LNADESIGN Gain Noise figure Non-linearity and Impedance matching.
- 14. FREQUENCY TRANSLATOR Normally composedof an oscillator and a frequency mixer
- 15. ELECTRONIC OSCILLATOR 1 MHzelectronic oscillator circuit which uses the resonant properties of an internal quartz crystal to control the frequency. Provides the clock signal for digital devices such as computers.
- 16. ELECTRONIC OSCILLATOR • Anelectronic oscillator is an electronic circuit that produces a periodic, oscillating electronic signal, often a sine wave or a square wave. • Oscillators convert direct current (DC) from a power supply to an alternating current (AC) signal. • They are widely used in many electronic devices. Common examples of signals generated by oscillators include signals broadcast by radio and television transmitters, clock signals that regulate computers and quartz clocks, and the sounds
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Editor's Notes
- #3 In the computer networking, data to be transmitted is the payload, but is almost always encapsulated in some type of a "frame" composed of framing bits and a frame check sequence. Examples are Ethernet frames, Point-to-Point Protocol (PPP) frames, Fibre Channel frames, and V.42 modem frames.
- #4 The bandwidth available from a satellite depends upon the number of transponders provided by the satellite. Each service (TV, Voice, Internet, radio) requires a different amount of bandwidth for transmission. This is typically known as link budgeting and a network simulator can be used to arrive at the exact value.
- #5 A communication channel or simply channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used to convey an information signal, for example a digital bit stream, from one or several senders (or transmitters) to one or several receivers. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second. Most communication satellites are radio relay stations in orbit and carry dozens of transponders, each with a bandwidth of tens of megahertz. Most transponders operate on a bent pipe (i.e., u-bend) principle, sending back to Earth what goes into the conduit with only amplification and a shift from uplink to downlink frequency. However, some modern satellites use on-board processing, where the signal is demodulated, decoded, re-encoded and modulated aboard the satellite. This type, called a "regenerative" transponder, has many advantages, but is much more complex.
- #6 A band-pass filter (also spelled bandpass) is a device that passes frequencies within a certain range and rejects (attenuates) frequencies outside that range.
- #7 A band-pass filter (also spelled bandpass) is a device that passes frequencies within a certain range and rejects (attenuates) frequencies outside that range.
- #8 A Band Pass filter will pass a particular band of frequency and attenuate the frequencies lesser and greater that the Lower Cut-off frequency and Higher Cut-off frequency.
- #9 A Band Pass filter will pass a particular band of frequency and attenuate the frequencies lesser and greater that the Lower Cut-off frequency and Higher Cut-off frequency.
- #10 An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the power of a signal (a time-varying voltage or current). An amplifier uses electric power from a power supply to increase the amplitude of a signal. A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is composed of semiconductor material usually with at least three terminals for connection to an external circuit. A bipolar junction transistor (bipolar transistor or BJT) is a type of transistor that uses both electron and hole charge carriers. The field-effect transistor (FET) is a transistor that uses an electric field to control the electrical behaviour of the device. FETs are also known as unipolar transistors since they involve single-carrier-type operation. A low noise amplifier is an electronic amplifier which is used in order to amplify possibly weak signals such as those received by an antenna. Low noise amplifiers are usually located very close to the detection device in order to reduce losses in the feed line. A low noise amplifier is a key component placed at the front end of a radio receiver circuit. By using a low noise amplifier, the effect of noise from subsequent stages of the receiving chain is diminished by the gain of the amplifier.
- #11 A low noise amplifier is an electronic amplifier which is used in order to amplify possibly weak signals such as those received by an antenna. Low noise amplifiers are usually located very close to the detection device in order to reduce losses in the feed line. A low noise amplifier is a key component placed at the front end of a radio receiver circuit. By using a low noise amplifier, the effect of noise from subsequent stages of the receiving chain is diminished by the gain of the amplifier. The most common sizes for nominal gain bandwidth are 3 MHz, 4 MHz and 10 MHz.
- #12 Amplifiers need a device to provide gain. In the 1940s, that device was a vacuum tube, but now it is usually a transistor or an integrated circuit. The transistor may be one of many varieties of bipolar transistors or field-effect transistors. In electronics, gain is a measure of the ability of a two-port circuit (often an amplifier) to increase the power or amplitude (the maximum displacement of a periodic wave) of a signal from the input to the output port by adding energy converted from some power supply to the signal.
- #13 Baseband refers to the original frequency range of a transmission signal before it is converted, or modulated, to a different frequency range.
- #14 Amplifiers need a device to provide gain. In the 1940s, that device was a vacuum tube, but now it is usually a transistor or an integrated circuit. The transistor may be one of many varieties of bipolar transistors or field-effect transistors. A bipolar junction transistor (bipolar transistor or BJT) is a type of transistor that uses both electron and hole charge carriers. The field-effect transistor (FET) is a transistor that uses an electric field to control the electrical behaviour of the device. FETs are also known as unipolar transistors since they involve single-carrier-type operation.
- #15 Oscillators are often characterized by the frequency of their output signal: A low-frequency oscillator (LFO) is an electronic oscillator that generates a frequency below approximately 20 Hz. This term is typically used in the field of audio synthesizers, to distinguish it from an audio frequency oscillator. An audio oscillator produces frequencies in the audio range, about 16 Hz to 20 kHz.[2] An RF oscillator produces signals in the radio frequency (RF) range of about 100 kHz to 100 GHz. Oscillators designed to produce a high-power AC output from a DC supply are usually called inverters. There are two main types of electronic oscillator — the linear or harmonic oscillator and the nonlinear or relaxation oscillator
- #16 Oscillators are often characterized by the frequency of their output signal: A low-frequency oscillator (LFO) is an electronic oscillator that generates a frequency below approximately 20 Hz. This term is typically used in the field of audio synthesizers, to distinguish it from an audio frequency oscillator. An audio oscillator produces frequencies in the audio range, about 16 Hz to 20 kHz.[2] An RF oscillator produces signals in the radio frequency (RF) range of about 100 kHz to 100 GHz.[2] Oscillators designed to produce a high-power AC output from a DC supply are usually called inverters. There are two main types of electronic oscillator — the linear or harmonic oscillator and the nonlinear or relaxation oscillator
- #17 Oscillation: পর্যাবৃত্ত গতি সম্পন্ন কোন বস্তুকণা যদি এর পর্যায়কালের অর্ধেক সময় একটি নির্দিষ্ট দিকে এবং বাকি অর্ধেক সময় পূর্বগতির বিপরীত দিকে চলে তবে তার সে গতিকে স্পন্দন/কম্পন (Oscillation) গতি বলে। অর্থাৎ, স্পন্দন গতিকে অগ্র পশ্চাৎ পর্যাবৃত্ত গতিও বলা যেতে পারে। সরল দোলকের গতি, কম্পনশীল সুর শলাকা, গীটারের তারের গতি ইত্যাদি স্পন্দন/কম্পন গতির উদাহরণ। এছাড়া, কঠিন বস্তুসমূহের অভ্যন্তরে পরমানু স্পন্দিত হয়। সাধারণভাবে বলা যায়, সকল শব্দের উদ্ভবই কোন না কোন স্পন্দন গতি থেকে হয়।
- #18 In electronics, a mixer, or frequency mixer, is a nonlinear electrical circuit that creates new frequencies from two signals applied to it. Mixers are widely used to shift signals from one frequency range to another, a process known as heterodyning, for convenience in transmission or further signal processing. For example, a key component of a super heterodyne receiver is a mixer used to move received signals to a common intermediate frequency. Frequency mixers are also used to modulate a carrier signal in radio transmitters.
- #19 In electronics, a mixer, or frequency mixer, is a nonlinear electrical circuit that creates new frequencies from two signals applied to it. Mixers are widely used to shift signals from one frequency range to another, a process known as heterodyning, for convenience in transmission or further signal processing. For example, a key component of a super heterodyne receiver is a mixer used to move received signals to a common intermediate frequency. Frequency mixers are also used to modulate a carrier signal in radio transmitters.