  In this paper, we propose a two-bit reconfigurable intelligent surface
(RIS)-aided communication system, which mainly consists of a two-bit RIS, a
transmitter and a receiver. A corresponding prototype verification system is
designed to perform experimental tests in practical environments. The carrier
frequency is set as 3.5GHz, and the RIS array possesses 256 units, each of
which adopts two-bit phase quantization. In particular, we adopt a
self-developed broadband intelligent communication system 40MHz-Net (BICT-40N)
terminal in order to fully acquire the channel information. The terminal mainly
includes a baseband board and a radio frequency (RF) front-end board, where the
latter can achieve 26 dB transmitting link gain and 33 dB receiving link gain.
The orthogonal frequency division multiplexing (OFDM) signal is used for the
terminal, where the bandwidth is 40MHz and the subcarrier spacing is 625KHz.
Also, the terminal supports a series of modulation modes, including QPSK, QAM,
etc.Through experimental tests, we validate a few functions and properties of
the RIS as follows. First, we validate a novel RIS power consumption model,
which considers both the static and the dynamic power consumption. Besides, we
demonstrate the existence of the imaging interference and find that two-bit RIS
can lower the imaging interference about 10 dBm. Moreover, we verify that the
RIS can outperform the metal plate in terms of the beam focusing performance.
In addition, we find that the RIS has the ability to improve the channel
stationarity. Then, we realize the multi-beam reflection of the RIS utilizing
the pattern addition (PA) algorithm. Lastly, we validate the existence of the
mutual coupling between different RIS units.
