Wideband GaAs MMIC Diode Frequency Doubler Using 4:1 Broadside Coupled Balun

A very wideband GaAs MMIC Schottky diode frequency doubler has been designed and tested; it has at least a 10-75 GHz output frequency range with indications it works to 90 GHz. Measured in a test fixture with 1.85 mm connectors over an output frequency of 10-67 GHz, it has 9 to 15 dB conversion loss, -15 to -25 dBc fundamental suppression, -22 to -35 dBc third harmonic suppression, and 15 to 20 dB input return loss, all including interconnect and connector losses. Additionally, calibrated wafer probe tests show it has under 16 dB conversion loss up to 75 GHz, and qualitative wafer probe tests indicates it works up to 90 GHz, in good agreement with simulated results. It is singly balanced with a broadside coupled 4: 1 transmission line transformer that provides wideband impedance match and input ground return. This appears to be the widest operating bandwidth reported for a GaAs MMIC diode frequency doubler. A family of frequency doublers and mixers has been designed and built that use this new circuit topology.