This paper presents an angular-domain massive MIMO detector which exploits sparsity in massive MIMO channel along with a reconfigurable systolic array architecture to achieve high area efficiency. The underlying idea is to perform signal detection in the angular domain, where the channel matrix can have much lower dimension due the limited number of dominant angles (of arrival and departure) of the wireless signal. Evaluated using the measured massive MIMO channel, the proposed method results in 40%-70% reduction in processing complexity and memory requirements compared to traditional antenna-domain detection. This complexity reduction enables extensive hardware reuse where all the operations of detection processing are mapped to a condensed reconfigurable systolic array. The angular-domain zero-forcing detector, which supports 128 base station antennas and 16 users is implemented in a 28 nm FD-SOI technology. Synthesis result shows that our design attains a throughput of 510 MSps with an area of 537 kG.