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Designing a digital satellite equipment control (DiSEqC)- compatible phantom antenna power-supply system

Maxim - 5339 app note

The MAX16948 is an automotive dual high-voltage, low dropout linear regulator (LDO)/switch with output current sensing. The device provides phantom power over the coax cable to remote radio frequency (RF) low-noise amplifiers (LNAs) in automotive systems with a maximum current of 300mA per channel. The device provides a fixed regulated output voltage of 8.5V or an adjustable 1V to 12V regulated output voltage (LDO mode).

The Digital Satellite Equipment Control (DiSEqC) standard is a communication protocol developed by Eutelsat used between satellite receiver (decoder), defined as master, and satellite peripheral equipment such as dish switchers, low-noise blocks (LNBs) and dish positioners, defined as slaves. The DiSEqC communication system uses only the existing coaxial cable, thus making DiSEqC ideal to reduce cost and improve reliability. The DiSEqC is an open standard with nonproprietary commands.

To allow one-way DiSEqC communication on the phantom antenna cable, a 22kHz tone-burst must be transmitted from the radio head unit and received by the remote antenna. The voltage amplitude of this tone-burst is 650mV, which is the value indicated by the DiSEqC standard. Note that the phantom antenna coax cable is also used to feed the LNA and to transmit the received radio signal. For this reason, the DiSEqC receiver must be able to reject the radio signal on the cable.

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