An MMIC wide-band doubly balanced resistive mixer with an active IF balun

In this paper, we present a wideband doubly-balanced resistive mixer fabricated using a 0.5 μm GaAs p-HEMT process. Three baluns are employed in the mixer. Local oscillator (LO) and radio frequency (RF) baluns operating over an 8 to 20 GHz range were implemented with Marchand baluns. In order to reduce the chip size, the Marchand baluns were realized using a meandering multi-coupled line, and inductor lines were inserted to compensate for the meandering effect. Over a frequency range of 8 to 20 GHz, the amplitude and phase unbalances of the LO and RF baluns were less than 1 dB and 6°, respectively. A 0.3 × 0.5 mm² IF balun was implemented through a DC-coupled differential amplifier. The measured amplitude and phase unbalances were less than 1 dB and 5°, respectively, from DC to 7 GHz. And the output third-order intercept (OIP3) and PldB, at a frequency of 1 GHz, were 18 dBm and 6 dBm, respectively. The mixer is 1.7 × 1.8 mm² in size, has a conversion loss of 5 to 11 dB, and an OIP3 of +10 to +15 dBm at 16 dBm LO power for the operating bandwidth.