Multi-antenna receivers are becoming popular in ambient backscatter communication (AmBC) because they help to improve the detection performance by improving the signalto-interference-plus-noise ratio (SINR) of the backscatter signal. Recent solutions, however, suffer from high implementation complexity and they tend to require the receiver to have high dynamic range. In this paper, a simplified receiver is proposed, which is able to overcome the above limitations. The receivers for the deterministic-unknown ambient signal and the Gaussian signal are derived using maximum-a-posteriori (MAP) criterion. Then, their detection performances are derived for bit-error-rate analysis. It is shown that the test statistic of the receiver is independent of the ambient signal type. The components for implementation are halved compared with the optimum AmBC receiver at the cost of an SINR penalty as low as 1-dB to achieve the same detection performance for the deterministic ambient signal and 3.6-dB for the Gaussian ambient signal. The dynamic range problem can be mitigated by implementing it fully in the analog domain. By providing attractive practical advantages mentioned above, the proposed simplified receiver, therefore, enables cost-effective AmBC receiver implementations.