Passive Antenna Coupler

The Becker Electronics Passive Antenna Coupler is typically used to complement Becker Electronics Leaky Feeder Systems. Such system are often employed in Mining, Shipping, Motorway and In-Building communications applications to aid with the transmission and reception of radio and communication signals.

The classic radiating system consists of a series of Bi-Directional Amplifiers and Radiating cable segments repeated through-out the underground or in-building tunnels and passages. Successful radio communication is ensured whilst the mobile radio equipment is within reasonable proximity to the leaky feeder cable. For many applications this is accomplished using a combination of Radiating Cable, Amplifiers, Signal Splitters and peripherals.

In some instances, it is desirable to extend the radio coverage for short distances away from the main Leaky Feeder System, perhaps around corners or into metallic shielded cages. Often times, the small extension is an after thought and was not originally designed into the system Radio Frequency Plan. A device is needed to facilitate the radio coverage extension, without significantly impacting the existing mainline system. This requirement is met with the use of Passive Antenna Couplers.

The desirable technical criteria of such a device include the following:

• Minimal additional RF dB Insertion Loss from Main Line input to Main Line Output. This prevents the device from affecting the existing installation
• Minimal additional DC Power Consumption. Since the Power Supplies in the Leaky Feeder System are already installed and commissioned, the device must not draw any additional current that may affect the ability of the System Power Supplies to hold the communications system up
• Minimal impact on system reliability. The addition of any additional equipment into the main line system has an immediate effect on the systems MTBF. The device must endeavour to maintain a solid copper connection from main line input to main line output so as to minimise the impact on reliability
• Maximum RF dBm signal strength of the coupled signal in the downlink direction. This will maximise the downlink signal strength on the additional segment being added to the system
• Minimal RF dB coupling loss of the coupled signal in the uplink direction. This will maximise the uplink signal propagation on the additional segment being added to the system

The Passive Antenna Coupler satisfies all of these criteria to allow an additional coverage segment to be facilitated as effectively as possible. The device is differentiated from a 3-Way or 4-Way splitter in that it is an unbalanced split. A conventional 3-Way splitter splits the radio signal equally 50-50% between the Split Port and the Main Line Port. This is appropriate when the Main Line is being Split into 2 new main lines, each of which is intended to include further Bi-Directional amplifiers and other active components.

The Passive Antenna Coupler splits the main line signal with most of the RF Energy remaining in the main line and a tiny fraction being coupled off onto the system extension. The Coupling Loss (in dB) indicates this fraction. A coupling loss of -10dB infers that 10% of the Main Line RF signal is re-directed to the extension ports. A coupling loss of -20dB infers that 1% of the Main Line RF signal is re-directed to the extension ports.