This study proposes a novel metamaterial-based cavity with a strong coupling effect between the transmitting and receiving devices. It is compact in size and the field distribution is uniform inside the cavity, which is realized by combining four artificial magnetic conductor surfaces at the four sidewalls and two metal palates at the top and bottom walls. The AMC consisting of a periodic array of square patches printed on the metal-backed double-layer dielectric substrate without connecting vias to enhance its operating bandwidth. Two monopole-type antennas are used as the transmitting and receiving terminals to examine the transmission property. The measured insertion loss of the metamaterial-based with different receiving positions are 1.06 dB, 2.26 dB, 2.02 dB, and 0.6 dB for position A, B, C, and D, respectively. The fabrication and measurement of the metamaterial-based cavity are demonstrated to validate its broad bandwidth and compact size.