Abstract: To address the bandwidth limitation issue in existing frequency-mixing-based retrodirective systems, this paper proposes a bandwidth-extended heterodyne retrodirective system. The system consists of an RF transceiver chain, a dual-channel synchronized frequency-conversion source, and a pair of orthogonally circularly polarized 1×8 array antennas. Its operating center frequencies are 3.5 GHz (right-hand circular polarization) and 5.6 GHz (left-hand circular polarization), enabling signal reception over 3.4–3.6 GHz and retrodirective transmission over 5.44–5.76 GHz. Measurement results show that the RF chain achieves a gain of up to 47 dB, the dual-channel frequency source exhibits low spurious output, and the antenna arrays maintain an axial ratio better than 4 dB. Monostatic RCS measurements further demonstrate that within the operating bandwidth, the system attains a 3 dB retrodirective power beamwidth of ±45°. These results confirm that the proposed architecture delivers robust wideband retrodirective performance across a broad angular range, providing an effective hardware platform for applications such as wireless power transfer and satellite communications.