Patent ID: 8081062

Claim:
An antenna system with a transmission part and a reception part highly isolated from each other, comprising: a transmission antenna for transmitting signals, the transmission antenna having a first feed point a and a second feed point b; a reception antenna for receiving signals, the reception antenna having a first feed point c and a second point d; a transmission hybrid coupler which is connected to the first feed point a and the second feed point b of the transmission antenna and transmits transmission signals which have a phase difference of 90° from each other; and a reception hybrid coupler which is connected to the first feed point c and the second feed point d of the reception antenna and receives reception signals which have a phase difference of 90° from each other, wherein a transmission coefficient from any one of the first feed point a and the second feed point b of the transmission antenna to any one of the first feed point c and the second feed point d of the reception antenna is substantially the same as a transmission coefficient from the other of the first feed point a and the second feed point b of the transmission antenna to the other of the first feed point c and the second feed point d of the reception antenna, so that signals leaking from the feed points a and b of the transmission antenna to the feed points c and d of the reception antenna are offset.