A first antenna element is embodied in a blanched structure, and a second antenna element is embodied in a blanched structure. A low coupling circuit for increasing susceptance with an increase in frequency is interposed between the first antenna element and the second antenna element. The first antenna element and the second antenna element exhibit resonance of a Y12 component of an admittance matrix between first and second frequencies and between second and third frequencies. The first branch element and the third branch element assume a value of nearly a quarter of a resonant electrical length of the Y12 component of the admittance matrix between the first and second frequencies. The second branch element and the fourth branch element assume a value of nearly a quarter of the resonant electrical length of the Y12 component of the admittance matrix between the second and third frequencies.