A phase controller for an antenna array (ANT_0 -ANT_(L-1)), comprising: a determination circuit, for determining a direction index of the antenna array (ANT_0-ANT_(L-1)), and for calculating a phase index according to the direction index according to a congruence modulo equation; a switching box, connected to the determination circuit, for selecting L first frequency signals with L first phases among K first frequency signals with K different first phases according to the phase index, wherein L and K are integer larger than 1, and L is not larger than K; and a frequency synthesizing module, connected to the switching box, comprising L phase-coherent PLL frequency synthesizers for receiving the L first frequency signals with the L first phases to generate L second frequency signals with L second phases to L antennae of the antenna array (ANT_0 -ANT_(L-1)), wherein a second frequency of the second frequency signals is larger than a first frequency of the first frequency signals; wherein the L first phases respectively correspond to remainders of 2π of L different first phases; wherein the L second phases respectively correspond to remainders of 2π of L different second phases; wherein the K different first phases are 0, δφ, 2δφ,..., (K-1)δφ, the L different first phases are 0, Δθ, 2Δθ,..., (L-1)Δθ, the second different phases are 0, Δφ, 2Δφ,..., (L-1)Δφ, δφ is a phase resolution and equals to 2π/K, Δφ equals to kδφ, k is the direction index being an integer, Δθ equals to 1δφ, 1 is the phase index being an integer; wherein M is a frequency divisor is related to the L phase-coherent PLL frequency synthesizers; wherein if M and K are mutually prime integers, the congruence modulo equation is Ml≡k(mod K); or if M=P/Q, the congruence modulo equation is Pl=Qk(mod QK), wherein P and Q are mutually prime integers. a determination circuit, for determining a direction index of the antenna array (ANT_0-ANT_(L-1)), and for calculating a phase index according to the direction index according to a congruence modulo equation; a switching box, connected to the determination circuit, for selecting L first frequency signals with L first phases among K first frequency signals with K different first phases according to the phase index, wherein L and K are integer larger than 1, and L is not larger than K; and a frequency synthesizing module, connected to the switching box, comprising L phase-coherent PLL frequency synthesizers for receiving the L first frequency signals with the L first phases to generate L second frequency signals with L second phases to L antennae of the antenna array (ANT_0 -ANT_(L-1)), wherein a second frequency of the second frequency signals is larger than a first frequency of the first frequency signals; wherein the L first phases respectively correspond to remainders of 2π of L different first phases; wherein the L second phases respectively correspond to remainders of 2π of L different second phases; wherein the K different first phases are 0, δφ, 2δφ,..., (K-1)δφ, the L different first phases are 0, Δθ, 2Δθ,..., (L-1)Δθ, the second different phases are 0, Δφ, 2Δφ,..., (L-1)Δφ, δφ is a phase resolution and equals to 2π/K, Δφ equals to kδφ, k is the direction index being an integer, Δθ equals to 1δφ, 1 is the phase index being an integer; wherein M is a frequency divisor is related to the L phase-coherent PLL frequency synthesizers; wherein if M and K are mutually prime integers, the congruence modulo equation is Ml≡k(mod K); or if M=P/Q, the congruence modulo equation is Pl=Qk(mod QK), wherein P and Q are mutually prime integers.