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Earth Station Transmitter
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Earth Station Transmitter



The Earth Station Transmitter is designed to teach ground-segment signal processing, modulation, and frequency conversion techniques. It includes an Analog Modulator and a Digital Modulator as well as two up converters.

The Analog Modulator section provides pre-emphasis baseband processing as well as wideband FM modulation, both commonly used in satellite communications systems. The 10 MHz bandwidth is sufficient for transmitting one composite television signal. The Wideband FM Modulator generates a modulated signal at 340 MHz, the first intermediate frequency (IF 1) of the transmitter.

The Digital Modulator section provides time-division multiplexing (TDM), scrambling, encoding and digital modulation. The TDM multiplexer allows multiplexing up to four data streams at a maximum data rate of 4 Mbit/s per stream. Three of the multiplexer inputs have BNC connectors whereas the fourth input has a USB connector for transmitting data from a computer. A fifth BNC input connector with its own Sampler is provided for a high bit-rate, unmultiplexed data stream of up to 20 Mbit/s. A switch allows selecting either the multiplexed or the high-bit rate data.

A Scrambler is used to ensure frequent transitions in the data and to spread the power smoothly over the available bandwidth. A Clock & Frame Encoder is used to add transitions to the multiplexed data in order to ensure reliable clock recovery in the receiver as well as control bits for frame synchronization. Both the Scrambler and the Clock & Frame Encoder can be switched on or off independently.

The Digital Modulator section uses DQPSK (differential quadrature phase-shift keying) modulation, a type of digital modulation commonly used in satellite communications systems. BNC connectors provide access to the I and Q channel signals of the DQPSK modulator. Front-panel test points provide access to signals at each intermediate stage of the modulation process. The DQPSK modulator generates a modulated signal at 340 MHz, the first intermediate frequency (IF 1) of the transmitter.

An SMA cable is used to connect the IF 1 signal from either the Analog Modulator or the Digital Modulator section to Up Converter 1, which shifts the signal frequency up to the IF 2 range (1.56 GHz). Up Converter 2 further shifts the signal frequency to produce the RF Output signal. Up Converter 2 includes a Channel selector to select one of six uplink frequencies in the 11 GHz range. It also has a Power Sensor to facilitate measurement of the transmitted power. A large-aperture horn antenna connected to the RF output transmits the uplink signal to the Satellite Repeater.

Additionally required equipment

Qty DescriptionModel Number
1 Power Cord - Type F 93992
1 Power Cord - Type B 95451
1 Power Cord - Type I 95451

Earth Station Transmitter
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