The SD15E3 from Sigatek is a frequency doubler with an input frequency of 3 to 6 GHz and output frequency from 6 to 12 GHz. This device has an insertion loss of under 15 dB and rejection of over 15 dBc. It can handle an input power of up to 10 dBm. The SD15E3 is available in a module with SMA connectors.
