FPGA implementation of a phased array DBF using polyphase filters

Efficient digital phased array beams require a high resolution timing vector. The timing coefficients cause speed bottleneck in FPGA implementation of such systems in the HF frequency range. We present polyphase structures to overcome the speed limitation for an ionospheric radar. The radar requires a constant phasing vector to steer the beam over a specified region of the ionosphere. Sixteen digital beams are derived from the vector with beam resolution of approximately three degrees. The phasing weights can be employed either in the time domain or in the frequency domain. Comparison of phase delay and time delay methods is presented for broadband frequencies of the radar. Performance of the proposed DBF system is discussed using clock efficiency and beam resolution.