The CER0637A from CTS Electronic Components is a RF Duplexer with Frequency 1.71 to 1.83 GHz, Band 1 1.81 to 1.83 GHz, Band 2 1.71 to 1.74 GHz, Power 3 W, Insertion Loss 2.5 dB. Tags: Ceramic, Surface Mount. More details for CER0637A can be seen below.