A Dual-Band Self-Oscillating Mixer for $C$-Band and $X$-Band Applications

A self-oscillating mixer that employs both the fundamental and harmonic signals generated by the oscillator subcircuit in the mixing process is experimentally demonstrated. The resulting circuit is a dual-band down-converting mixer that can operate in
C
-band from 5.0 to 6.0 GHz, or in
X
-band from 9.8 to 11.8 GHz. The oscillator uses active superharmonic coupling to enforce the quadrature relationship of the fundamental outputs. Either the fundamental outputs of the oscillator or the second harmonic oscillator output signals that exists at the common-mode nodes are connected to the mixer via a set of complementary switches. The mixer achieves a conversion gain between 5-12 dB in both frequency bands. The output 1-dB compression points for both modes of the mixer are approximately -5 dBm and the output third-order intercept point for
C
-band and
X
-band operation are 12 and 13 dBm, respectively. The integrated circuit was fabricated in 0.13-¿m CMOS technology and measures 0.525 mm
²
including bonding pads.