Direction-Finding System Using Two-Element Time Modulated Array With and Without Modulation

In this paper, a Time Modulated Array (TMA) direction finding system using a two element antenna array is implemented in LabVIEW and is experimentally verified with continuous time and BPSK modulated signal as the source. The TMA involves high speed switches functioning periodically at the front end of the traditional antenna array. This makes the array output a periodic function of time and the harmonics involved has a direct relation with the incident angle of the signal. Thus a simple harmonic analysis technique can be used to find the Direction of Arrival(DoA) of the incoming signal. In this paper the system consists of a two monopole antenna array, an RF switch, Universal Software Radio Peripheral (USRP) and LabVIEW. The spectrum analysis and angle estimation is carried out in LabVIEW. The method is simple in terms of hardware and computational complexity. The simulation results give an estimate of the DoA with a maximum error of 2.23⁰ incident angles ranging from 0 to 90⁰. The results are verified experimentally with continuous time signal giving an estimate angle of arrival in a range 20⁰ to 70⁰ with a maximum error of 8.24⁰. Further, BPSK modulated signal is used to give an estimate angle within an angle of arrival ranging from -50⁰ to 50⁰ with a maximum error of 7⁰. The experiments are conducted in the laboratory environment.