Cooperative Base Line Interferometer for SWaP Optimized Direction Finding Receivers

Base line interferometer (BLI) is a popular direction of arrival (DOA) estimation technique for electronic warfare applications. For size, weight, and power (SWaP) optimized realization of the BLI, switched mode of operation is preferred which uses fewer number of receiver channels than the number of antenna elements and switches them among the antenna-pairs in a phased manner. Such switched operation, however, results in a suboptimal performance, since, as shown in this article, it reduces the tolerable phase-error margin (TPM), and thus, produces more erroneous DOA estimates. To overcome this, we propose a three-antenna BLI algorithm named as
Cooperative BLI (Co-BLI) triplet
which provides more TPM while maintaining high DOA estimation accuracy. This improvement comes at the cost of slight increase in implementation resources. To increase the estimation accuracy further, we next extend the proposed Co-BLI to the case of more number of antennas. For this, we also propose a way to reduce the number of antennas to form a higher order array and derive the expressions for all inter-element distances. For real-time operation, we develop a
Mapping-based Cooperative Ambiguity Table
(M-CAT): a look-up-table based implementation scheme where we show that by storing just a few combinations of the input ranges, one can estimate any DOA within the given field-of-view accurately, thus facilitating high throughput hardware implementation avoiding complex computations. The proposed algorithm has been validated through extensive MATLAB simulation studies and implemented in FPGA based real-time hardware.