Antenna Switch Control Method for Analog Radio Over Fiber Systems

摘要

A central node connected to a remote network node via a fiber optic link controls an antenna switch in the remote network node by controlling the DC bias current of the laser providing an optical transmission signal from the central network node to the remote network node via the fiber optic link. The remote network node converts the received optical transmission signal to an electrical transmission signal, and detects the DC level of the electrical transmission signal. If the detected DC level satisfies a predetermined condition, the remote network node connects the antenna port of the antenna switch, and thus the antenna, to a reception signal path of the remote network node. Otherwise, the remote network node connects the antenna port of the antenna switch, and thus the antenna, to a transmission signal path of the remote network node.

主权项

1. A first network node operatively connected to a second network node via at least one optical fiber, the first network node configured to wirelessly communicate with one or more wireless terminals via an antenna, the first network node comprising:
a fiber input; a fiber output; an antenna switch configured to selectively connect an antenna port to either a transmission port or a reception port, the transmission port operatively connecting to the fiber input via a transmission circuit path, the reception port operatively connecting to the fiber output via a reception circuit path, and the antenna port operatively connecting to the antenna; and a detection circuit configured to:
detect a direct current (DC) level of a transmission signal output by the fiber input;control the antenna switch to connect the antenna port to the reception port when the detected DC level satisfies a predetermined condition; andotherwise, control the antenna switch to connect the antenna port to the transmission port to transmit the transmission signal via the antenna; wherein the detection circuit comprises:
a DC extraction circuit configured to extract the DC level from the transmission signal; anda comparator configured to compare the extracted DC level to a reference level to determine whether the detected DC level satisfies the predetermined condition; and a reference circuit configured to set the reference level relative to an optimal DC level and responsive to an effective impedance of the transmission circuit path, wherein the optimal DC level comprises a DC bias value selected to optimize a quality of the transmission signal.