This part is a kind of semiconductor called STM-3116.

Function of this product has High Linearity Active Transmit Mixer.

Manufacturers : Sirenza Microdevices

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Some of the text within the PDF file :

Preliminary Product Description The Sirenza Microdevices’ STM-3116 is a high linearity active mixer for use in a wide variety of communication systems covering the 2100-2500 MHz frequency bands. This device operates from a single 5V supply and provides 17 dB of conversion gain while requiring only 0dBm input to the integrated LO driver. The STM-3116 also includes an integrated on chip IF amplifier and is fabricated using Silicon Germanium (SiGe) device technology. The RF and LO ports can be driven differential or single ended. Each broadband port has been designed to minimize performance degradation while operating into highly reactive components such as SAW filters. The device is packaged in an industry standard 16 pin TSSOP with exposed paddle for superb RF and thermal ground. STM-31 [ ... ]

STM-3116 PDF Datasheet Download