Abstract
Antenna array-based multi-dimensional infinite-impulse response (IIR) digital beamformers are employed in a multitude of radio frequency (RF) applications ranging from electronically-scanned radar, radio telescopes, long-range detection and target tracking. A method to design 3D IIR beam filters using 2D IIR beam filters is described. A cascaded 2D IIR beam filter architecture is proposed based on systolic array architecture as an alternative for an existing radar application. Differential-form transfer function and polyphase structures are employed in the design to gain an increase in the speed of operation to gigahertz range. The feasibility of practical implementation of a 4-phase polyphase 2D IIR beam filter is explored. A digital hardware prototype is designed, implemented and tested using a ROACH-2 Field Programmable Gate Array (FPGA) platform fitted with a Xilinx Virtex-6 SX475T FPGA chip and multi-input analog-to-digital converters (ADC) boards set to a maximum sampling rate of 960 MHz. The article describes a method to build a 3D IIR beamformer using polyphase structures. A comparison of technical specifications of an existing radar application based on phased-array and the proposed 3D IIR beamformer is also explained to illustrate the proposed method to be a better alternative for such applications.
Highlights
Applications of antenna array-based electronically steerable directional beamformers can be found in a range of areas such as mobile communications, radar [1,2], microwave sensing, long-range detection and target tracking, cognitive radio and radio telescope arrays [3,4,5]
KatADC is a popular analog-to-digital converters (ADC) developed by Texas Instruments Inc. that is widely used in radio telescopes such as the Square Kilometer Array (SKA) [40]
The differential form infinite-impulse response (IIR) beam filters together with multirate structures help to overcome the limitations in operating frequencies in ADCs and Field Programmable Gate Array (FPGA) clock rates
Summary
Applications of antenna array-based electronically steerable directional beamformers can be found in a range of areas such as mobile communications, radar [1,2], microwave sensing, long-range detection and target tracking, cognitive radio and radio telescope arrays [3,4,5]. ROACH-2 multi-channel ADC cards have restrictions in maximum achievable sampling frequencies with an upper bound of 240 MSamples/s when all 16 inputs are enabled, limiting the maximum beamformer operating frequency at 240 MHz. In order to overcome these limitations, the authors in [19] proposed the use of multirate signal processing [20,21,22] to increase the real-time computational throughput at the cost of circuit complexity by parallel processing [23]. The authors in [19] describe a multirate 2D IIR RF beamformer realized on ROACH-2 with two polyphases that can operate at a frequency of 480 MHz. This paper concentrates on an extended design of the multirate wideband beamformer stated earlier that can operate close to 1 GHz and developed further to achieve 3D beamforming for planar antenna arrays. We will discuss the potential for practical realization by comparing this design with an existing real world application and probable future work related to this research
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
