A Highly Linear Single-Balanced Resistive X-band MMIC Mixer in GaN HEMT Technology

In this paper a highly linear X-band MMIC mixer implemented in a $0.25 \mu \mathrm{m}$ GaN HEMT technology is presented. The mixer is based on a single-balanced resistive architecture using a pair of symmetrical $\mathbf{4} \times \mathbf{1 2 5} \mu \mathrm{m}$ GaN HEMTs. A novel minituarized half-wavelength hair-pin type of balun creates the balanced LO signal to be fed to the gates. A lumped-element diplexer network is used to separate the IF and RF signals at the drains. The fabricated MMIC mixer demonstrates a 6.9 dB conversion loss at $10 \mathbf{~ G H z}$ with an LO power of $+\mathbf{2 4. 6} \mathbf{~ d B m}$ and a bandwidth from $7.8-12.2 \mathrm{GHz}$. Over the same bandwidth the single-tone second and third-order spurious responses are below -66 dBm and -98 dBm, respectively, at an RF input power level of -10 dBm. The experimental results furthermore show that the two-tone third-order input intercept point (IIP3) reaches $\sim 30$ dBm at an applied LO power of $+\mathbf{2 4. 6} \mathrm{dBm}$.