A new RF interference cancellation using a novel 3-pole bandstop resonator designed using tapped CRLH T-line model

Abstract

Wideband interference signals appearing at 20 MHz, 15 MHz and even 10 MHz away from the edge of the mobile received signal can now be suppressed by more than 30 dB by following the new RF interference cancellation technique introduced in this paper using bandstop resonators. Furthermore, a new methodology for designing a 3-pole bandstop resonator with very sharp rejection is presented. The resonators are implemented using a power splitter and different number of cells from the composite right/left handed transmission (CRLH-T) line circuit model. Two resonators are fabricated and measured: using two cells; and three cells, showing an insertion loss of less than 1.2 dB. An interference cancellation test bench is set using two 9 MHz LTE modulated signals with equal average peak power (40 dBm). The power spectrum measurements show more than 30 dB cancellation for the interferer injected at 20 MHz separation from the desired signal using the two-cell resonator. More than 45 dB and 30 dB cancellation are also achieved for interferers with only 15 MHz and 10 MHz frequency separation using the three-cell resonator. The tests are repeated with high power interferers (e.g. 20 dB above the received signal level) and the same cancellation performance is maintained without retuning any of the components used.