Four beams helical antenna array for mobile satellite application

This paper describes the design and fabrication of an helical array antenna that produces four beams operating at 10 GHz. The antenna consists of 16 helical antennas of axial mode arranged in 4 by 4 array on a PCB. The distance between helices is determined such that the beam is tilted at a certain angle and the 3 dB power is at its normal axis. This is done by feeding the antenna in series via a microstrip line which also acts like a phase shifter. The couplers combine all the feeding microstrip lines into a single SMA connector at each side so that we have 4 output ports. Each port produces one beam at its particular angles. By employing switching, the desired beam can be chosen. In this manner we would be able to track any signal within its coverage without mechanically moving the antenna direction. From the measurement, it is found that the designed antenna is matched to 50 ohms with VSWR less than 1.3 and gain of 10 dB. The measured radiation patterns were also in agreement with the theoretical values.