A single balanced diode mixer with defected ground structure (DGS) lowpass filter (LPF)

In this paper, a single balanced diode mixer using harmonic-suppressed defected ground strncture @GS) low-pass filter (LPF) with dumb-hell shape is presented. -F requency bandwidth is selected for a C-band, which is 5.72 ~ 5.82 GHz for RF, 5.58 ~5.68 GHz for LO, and 140 MHz for IF signals. A rat-race hybrid is designed for the accomplishment of the single balanced type of mixer. A lowpass filter using DGS is used for good conversion loss and unwanted 2nd and 3rd harmonic suppression. The mixer is compared to a reference mixer with conventional low-pass filter. When LO signal with the power of 4 dBm at 5.635 GHz is injected, a conversion loss of 6.2 dB is obtained for the mixer. Also, the LO to RF and LO to IF isolation of 30 dB and 40 dB are obtained, respectively. This mixer can be used in the area on wireless LAN application.