Planar array antenna

1. A planar array antenna, comprising:

a multi-layer substrate having an intermediate layer conductor in a laminated face;

first and second slot lines formed in said intermediate layer conductor, and intersecting each other;

first and second microstrip lines formed on said multi-layer substrate, and traversing said first slot line, respectively, at a position corresponding to both end sides of said first slot line;

third and fourth microstrip lines formed on said multi-layer substrate, and traversing said second slot line, respectively, at a position corresponding to both end sides of said second slot line;

a first antenna element coupling to one end of said first microstrip line and one end of said third microstrip line;

a second antenna element coupling to the other end of said first microstrip line and one end of said fourth microstrip line;

a third antenna element coupling to one end of said second microstrip line and the other end of said fourth microstrip line;

a fourth antenna element coupling to the other end of said second microstrip line and the other end of said third microstrip line;

a fifth microstrip line provided on said multi-layer substrate, a top end side of said fifth microstrip line traversing said first slot line in a center region of said first slot line so as to be electromagnetically coupled to said first slot line; and

a sixth microstrip line provided on said multi-layer substrate, a top end side of sixth microstrip line traversing said second slot line in a center region of said second slot line so as to be electromagnetically coupled to said second slot line;

wherein each of said first to fourth antenna elements is an antenna element excitable in two directions.

2. The planar array antenna according to claim 1 , wherein said first to fourth antenna elements are disposed on a geometrically square apex, respectively.

3. The planar array antenna according to claim 2 , wherein said first to fourth antenna elements are an antenna element of a microstrip line type provided on a first principal surface of said multi-layer substrate, said first and second microstrip lines are provided on said first principal surface, and are directly connected to said antenna elements, said third and fourth microstrip lines are provided on a second principal surface of said multi-layer substrate, said fifth microstrip line is provided on said first principal surface, and said sixth microstrip line is provided on said second principal surface.

4. The planar array antenna according to claim 3 , wherein said third and fourth microstrip lines are electrically connected to said antenna elements through via holes provided on said multi-layer substrate.

5. The planar array antenna according to claim 3 , wherein said third and fourth microstrip lines are electromagnetically coupled to said antenna elements through openings provided in said intermediate layer conductor.

6. The planar array antenna according to claim 3 , wherein said each antenna element is provided in a shape of a regular square or a circle, and is excitable in two directions at the same frequency, thereby sharing a horizontal polarization and a vertical polarization.

7. The planar array antenna according to claim 2 , wherein said first to fourth antenna elements are an antenna element of a microstrip line type provided on a first principal surfaoe of said multi-layer substrate, said first to fourth microstrip lines are provided on said first principal surface, and are electrically connected to said antenna elements, and said fifth and sixth microstrip lines are provided on a second principal surface of said multi-layer substrate, and

wherein one of said fifth and sixth microstrip lines strides over the other of said fifth and sixth microstrip lines through an air bridge using a conducting wire in a region where said first and second slot lines intersect each other.

8. The planar array antenna according to claim 7 , wherein said each antenna element is provided in a shape of a regular square or a circle, and is excitable in two directions at the same frequency, thereby sharing a horizontal polarization and a vertical polarization.

9. The planar array antenna according to claim 2 , wherein said first to fourth antenna elements are an antenna element of a slot line type formed in said interlayer conductor, said first and second microstrip lines are electromagnetically coupled to said antenna elements provided on a first principal surface of said multi-layer substrate, said third end fourth microstrip lines are provided on a second principal surface of said multi-layer substrate, and are electromagnetically coupled to said antenna elements, said fifth microstrip line is provided on said first principal surface, and said sixth microstrip line is provided on said second principal surface.

10. The planar array antenna according to claim 9 , wherein said each antenna element is provided in a shape of a regular square or a circle, and is excitable in two directions at the same frequency, thereby sharing a horizontal polarization and a vertical polarization.

11. The planar array antenna according to claim 1 , wherein said each antenna element is provided in a shape of a regular square or a circle, and is excitable in two directions at the same frequency, thereby sharing a horizontal polarization and a vertical polarization.

12. The planar array antenna according to claim 1 , wherein said each antenna element is provided in a shape of a rectangle or an oval, thereby enabling to operate at plural frequencies.

13. The planar array antenna according to claim 1 , further comprising a delay circuit making a phase difference between said fifth microstrip line and said sixth microstrip line as 90 degrees.

14. The planar array antenna according to claim 13 , wherein said delay circuit is a power distributor/coupler having two input ports and two output ports, and high frequency components from one input port and the other input port are given a phase difference of π/2 which mutually advances and delays between said two output ports.

15. A planar array antenna, comprising:

a multi-layer substrate having an intermediate layer conductor on a laminated face; and

four pieces of planar antenna units formed on said multi-layer substrate, and disposed in a matrix pattern;

wherein each planar antenna unit comprises: first and second slot lines formed in said intermediate layer conductor, and intersecting each other; first and second microstrip lines formed on said multi-layer substrate, and traversing said first slot line, respectively, at a position corresponding to both end sides of said first slot line; third and fourth microstrip lines formed on said multi-layer substrate, and traversing said second slot line, respectively, at a position corresponding to both end sides of said second slot line; a first antenna element coupling to one end of said first microstrip line and one end of said third microstrip line; a second antenna element coupling to the other end of said first microstrip line and one end of said fourth microstrip line; a third antenna element coupling to one end of said second microstrip line and the other end of said fourth microstrip line; a fourth antenna element coupling to the other end of said second microstrip line and the other end of said third microstrip line; a fifth microstrip line provided on said multi-layer substrate, a top end side of said fifth microstrip line traversing said first slot line in a center region of said first slot line so as to be electromagnetically coupled to said first slot line, and a sixth microstrip line provided on said multi-layer substrate, a top end side of said sixth microstrip line traversing said second slot line in a center region of said second slot line so as to be electromagnetically coupled to said second slot line, and

wherein said fifth microstrip lines of two pieces of said planar antenna units adjacent to a first direction are commonly connected, thereby configuring a first common microstrip line, and said sixth microstrip lines of two pieces of said planar antenna units adjacent to a second direction different from said first direction are commonly connected, thereby configuring a second common microstrip line,

said planar array antenna, further comprising:

third and fourth slot lines formed on said intermediate layer conductor, and mutually intersecting;

a seventh microstrip line formed on said multi-layer substrate, a top end side of said seventh microstrip line traversing said third slot line in a center region of said third slot line so as to be electromagnetically coupled to said third slot line; and

an eighth microstrip line provided on said multi-layer substrate, a top end side of said eighth microstrip line traversing said fourth slot line in a center region of said fourth slot line so as to be electromagnetically coupled to said fourth slot line;

wherein said first common microstrip lines traverse said third slot line, respectively, at a position corresponding to both end sides of said third slot line, and said second common microstrip lines traverse said fourth slot line, respectively, at a position corresponding to both end sides of said fourth slot line.