  The surge of massive antenna arrays in wireless networks calls for the
adoption of analog/hybrid array solutions, where multiple antenna elements are
driven by a common radio front end to form a beam along a specific angle in
order to maximize the beamforming gain. Many heuristics have been proposed to
sample the angular domain by trading off between sampling step size and
overhead, where arbitrarily small angular step size is only attainable with
infinite sampling overhead. We show that, for uniform linear and rectangular
arrays, lossless reconstruction of the array's angular responses at arbitrary
angular precision is possible using a finite number of samples without
resorting to assumptions of angular sparsity. The proposed method, sampling and
reconstructing angular domain (SARA), defines how many and which angles to be
sampled and the corresponding reconstruction. This general solution to scan the
angular domain can therefore be applied not only to beam acquisition and
channel estimation, but also to radio imaging techniques, making it a candidate
for future integrated sensing and communications (ISAC). Extensive simulation
results for target detection and radio imaging have demonstrated clear
advantages of SARA versus other considered baselines, both in terms of angular
reconstruction performance and computational complexity.
