Design of radio repeater system using a near-field cancellation technique

A new concept for implementation of a miniaturized high-gain and low-power radio repeater is presented in this paper. The proposed micro repeater has a simple RF architecture and can route multiple channels simultaneously. The repeater is composed of low-profile planar miniaturized antennas with vertically polarized radiation pattern, low-power high-gain amplifier chain, and a ring hybrid coupler as a feed network for the transmit antenna pair. By designing the radio repeater structure in symmetric manner and feeding the transmit antenna pair out-of-phase, a null-plane is created in which the receive antenna feed is placed. This way the mutual coupling between the transmit and receive antennas can be suppressed down to -86 dB. It is shown that 54 dB gain of RF amplifier can be inserted into the proposed radio repeater within very small physical dimensions (0.22 λ₀² × 0.03 λ₀). The operation principle and design guide are presented in this paper.