Large microstrip array antenna with hybrid feed network of standing and traveling waves

A novel design for large microstrip array antennas is presented. The design is based on combination of standing-wave and traveling-wave antennas. A standing-wave antenna provides a compact structure because it does not require quarter-wavelength transformers. However just with a standing-wave design, the array size has to remain relatively small. Thus the concept for traveling-wave antennas needs to be incorporated to produce a substantially large array antenna. As an example, an array of 512 elements was fabricated for the US DBS application and characterized. The operation frequency was set at about 12.5 GHz. A gain of 30 dBi was measured, which corresponds to an aperture efficiency of 50%.