FBFN correction method for beam pointing error of LMDS system and a device thereof

#1. Field of the Invention

#The invention relates to a method for automatically correcting a beam pointing error at a customer premised equipment (CPE) of a local multipoint distributed system (LMDS) and a device thereof, particularly, to a method for correcting a beam pointing error by using a membership function, which is designed for a beam pointing error distributioin caused by wind force, based on a fuzzy basis function network (FBFN) rules. The device is capable of automatically pointing a main beam of a multi-beam planar array antenna on a base station to improve transiently a communication quality in the LMDS system on a bad weather condition. The correction device for the beam pointing error uses a multi-beam planar array antenna to obtain a direction-of-arrival (DOA) of a base station and uses a FBFN algorithm to estimate a beam pointing error so that a main beam of the planar array antenna can point at a main beam of the multi-beam planar array antenna on the base station so as to improve the quality of the communication. The FBFN algorithm includes thirteen normalized Gaussian membership functions and thirteen rules, which are generated based on the beam pointing error distribution caused by wind force.

#2. Description of the Prior Art

#This disclosure will present in detail the following description of preferred embodiments with reference to the following figures, wherein:

#FIG. 1 is a block diagram, showing a function of a beam pointing error correction device of an array antenna of a LMDS system, in accordance with one embodiment of the invention;

#FIG. 2 is a diagram, showing a signal flow of a beam pointing error correction device of an array antenna of the LMDS system, in accordance with the embodiment of the invention;

#Table 1 explains an example for a beam pointing error distribution simulating the wind force model in such as Taiwan area, in accordance with the embodiment of the present invention.

#As shown in FIG. 1, FIG. 1 shows a functional block diagram of a beam pointing error correction device of an array antenna of a LMDS system in accordance with one embodiment of the invention, in that the left-hand side shadow block is a FBFN beam pointing error correction processing means 1, which is disclosed by the invention and is one of the main features of the invention; reference number 2 represents an array antenna; reference number 3 represents a beam shaping circuit; and reference number 4 represents a DOA estimation means. The signal flow of the device shown in FIG. 1 is illustrated in FIG. 2. FIG. 2 is a diagram showing a signal flow of a beam pointing error correction device of an array antenna of the LMDS system in accordance with the invention. As shown in FIG. 2 by using a multi-beam planar array antenna 2, a signal transmitted from a base station (not shown) is received at a customer premise equipment (CPE) of a LMDS system (not shown)(step S1); then, 4-beams signals having different intensities are generated by a beam shaping circuit in a horizontal fixed pointing direction (step S2); subsequently, two adjacent beam signals having the most strong intensities are selected from the 4-beam signals having different intensities (step S3) and subtracted to each other to generate an estimated direction-of arrival (DOA) angular signal (step S4); then, the estimated DOA angular signal is transferred to a FBFN processing means for beam pointing error correction and calculated to obtain a correction angle, and finally, the correction angle is transferred to the beam shaping circuit to generate a fifth beam, and a main beam of the fifth beam is pointed at the base station for communication, where the array antenna of the LMDS system is a two dimensional planar array antenna (2×6 antenna elements), which may perform an angular correction for both of the horizontal and vertical beam pointing error. The planar array antenna is arranged as shown in FIG. 3, the full pointing signal pattern of the antenna are: 1 AF = ∑ n = 1 N ⁢ ⁢ [ ∑ m = 1 M ⁢ ⁢ I m ⁢ ⅇ j ⁡ ( m - 1 ) ⁢ ( kd x ⁢ sin ⁢ ⁢ θcosφ + β x ) ] ⁢ ⅇ j ⁡ ( n - 1 ) ⁢ ( kd y ⁢ sin ⁢ ⁢ θcosφ + β y ) ( 1 ) βx=−kdx sin θ0 cos φ0  (2)

#βy=−kdy sin θ0 cos φ0  (3)