32-Channel X-band digital beamforming plug-and-play receive array

Phased array architectures have evolved to a point where digital beamforming (DBF) is rapidly becoming the preferred approach for many new advanced communication and radar phased arrays that will be in production by the end of this decade. DBF is often touted as the ultimate in phased array performance, yet one of its biggest potential long-term advantages may be lower cost. Traditionally, two of the biggest cost drivers in analog phased arrays have been non-recurring engineering costs attributed to non-scalable one-of-a-kind array designs and low-volume production of high performance RF components. Very few phased arrays share common components to any great degree and nearly all utilize uniquely designed RF manifolds. The advent of DBF will likely foster scalable modular phased array designs that reduce design costs and promote higher-volume production of key RF components. Below L-band, DBF receiver components are now small enough to integrate directly behind the array within the element unit cell. Above L-band, DBF architectures often use subarrays, or row/column implementations because the receiver hardware is still too large. This paper introduces a prototype X-band receive-only DBF array with a modular, scalable architecture and a very compact profile. This DBF array architecture uses column-level digital beamforming in the azimuth plane without subarrays, and has a rectangular aperture of 512 elements, arranged in 32 columns of 1x16 elements. Each column is connected to one of 32 compact digital receiver modules, which in turn, plug directly into a 4-beam real-time parallel processor board. The DBF receiver modules are composed of two separable sections, an "RF front-end" and a "digital back-end". The RF front-end is designed for specific phased array frequency, bandwidth and dynamic range requirements, whereas the "digital back-end" design is generalized to interface with several different RF front-ends that operate at different frequencies. Interchangeability of RF front-ends is made possible using a standardized intermediate frequency (IF) interface between the RF front-end and the digital back-end, with fixed IF bandwidth and dynamic range. The overall architecture is scalable since more modules can be added to build a larger array aperture. The ke- y limiter of DBF architecture scalability is processor load. To address this problem, we are building a multi-beam parallel processor which itself is scalable. To that end, this paper reports our progress to date in the development of this prototype modular DBF array.