designing a phantom antenna power supply system

Description: A design for a phantom antenna power-supply system compatible with the Digital Satellite Equipment Control (DiSEqC) communication standard, utilizing the MAX16948 automotive dual, high-voltage LDO/switch. The application circuit provides a remote antenna power supply and enables one-way communication from the radio head unit to the remote antenna. This system architecture allows flexibility in the choice of DiSEqC tone-burst frequency (100Hz to 30kHz), enabling users to select the optimal frequency for their application. The MAX16948 is an automotive dual high-voltage, low dropout linear regulator (LDO)/switch with output current sensing. The device supplies phantom power over the coax cable to remote radio frequency (RF) low-noise amplifiers (LNAs) in automotive systems, with a maximum output current of 300mA per channel. It provides a fixed regulated output voltage of 8.5V or an adjustable output voltage ranging from 1V to 12V in LDO mode. The Digital Satellite Equipment Control (DiSEqC) standard is a communication protocol developed by Eutelsat, used between the satellite receiver (decoder), defined as the master, and satellite peripheral equipment such as dish switchers, low-noise blocks (LNBs), and dish positioners, defined as slaves. The DiSEqC communication system utilizes only the existing coaxial cable, making it ideal for cost reduction and improved reliability. DiSEqC is an open standard with nonproprietary commands. To enable 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, as specified by the DiSEqC standard. The phantom antenna coax cable is also employed to supply power to the LNA and to transmit the received radio signal. Therefore, the DiSEqC receiver must effectively reject the radio signal on the cable. In the DiSEqC application circuit, the MAX16948 operates in LDO mode, with the regulated output voltage dynamically adjusted to generate the DiSEqC pulses. The blue block represents the radio head unit, which includes the remote antenna power supply (MAX16948) that also functions as the DiSEqC tone-burst transmitter and tuner. The red block represents the remote antenna, consisting of the physical antenna, LNA, and DiSEqC receiver (the MAX931 low-power comparator). The coax cable facilitates communication between the radio head unit and the remote antenna (including both the radio signal and DiSEqC tone-burst) while also powering the remote LNA, thereby reducing costs and cable weight.

The phantom antenna power-supply system designed around the MAX16948 LDO/switch effectively addresses the requirements of modern satellite communication systems. The integration of the MAX16948 allows for efficient power distribution to remote components, ensuring that the RF LNAs receive adequate phantom power through the same coaxial cable used for signal transmission. This dual functionality not only simplifies the system architecture but also minimizes the physical footprint of installations, which is critical in automotive applications where space and weight are at a premium.

The flexibility of selecting the tone-burst frequency between 100Hz and 30kHz provides users with the capability to optimize performance based on specific environmental conditions or system requirements. The ability to dynamically adjust the output voltage in LDO mode for generating DiSEqC pulses enhances the system's adaptability, allowing for seamless integration with various satellite peripherals.

Furthermore, the DiSEqC standard's reliance on existing coaxial infrastructure significantly reduces installation costs and enhances reliability, as it eliminates the need for additional cabling. The design also includes provisions for the rejection of unwanted signals, ensuring that the integrity of the received radio signal is maintained while allowing for effective communication between the master and slave devices.

Overall, this phantom antenna power-supply system exemplifies a sophisticated approach to satellite communication, leveraging advanced components and standards to deliver a robust and efficient solution for modern automotive applications.A design for a phantom antenna power-supply system compatible with the Digital Satellite Equipment Control (DiSEqC) communication standard, using the MAX16948 automotive dual, high-voltage LDO/switch. The presented application circuit provides a remote antenna power supply and also enables one-way communic

ation from the radio head unit to the remote antenna. This system architecture offers flexibility in DiSEqC tone-burst frequency choice (100Hz to 30kHz), enabling users the ability to select the best frequency for their application. 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. In the DiSEqC application circuit (Figure 1), the MAX16948 is used in LDO mode and the regulated output voltage is dynamically changed to generate the DiSEqC pulses. The blue block is the radio head unit, which includes the remote antenna power supply (MAX16948) used also as DiSEqC tone-burst transmitter and the tuner.

The red block is the remote antenna formed by the physical antenna, the LNA, and the DiSEqC receiver (the MAX931 low-power comparator). The coax cable enables the communication between the radio head unit and the remote antenna (radio signal and DiSEqC tone-burst) and is also used to feed the remote LNA, saving cost and cable weight.