Isolation between three antennas at 700 MHz: for handheld terminals

To address the antenna design challenges posed by many frequency bands, introduced with long-term evolution deployment, this study proposes the use of separate transmit (Tx) and receive (Rx) narrow-band antennas. In addition, a diversity Rx (Dx) antenna is needed for multiple-input multiple-output performance. Although the isolation between two antennas at low frequencies (700 MHz) is crucial for the successful implementation of 4G in handheld terminals, it becomes more challenging when considering isolation among three antennas (one Tx and two Rx antennas) at low frequencies. Hence, a method that improves the isolation between the ports of one Tx and two Rx antennas is presented here.