X-band Weaver-Hartley low-IF downconverter with a resonant LC load

An X-band Weaver-Hartley dual-conversion low-IF downconverter is demonstrated in this paper using 0.35-¿m SiGe heterojunction bipolar transistor (HBT) technology. The first image signal is shifted away from the IF band due to the complex Weaver architecture while the second image signal is eliminated by a polyphase filter in the following Hartley architecture. In this work, a resonant LC load is employed at the first-stage mixer to improve both gain and linearity. As a result, the demonstrated downconverter achieves a conversion gain of 8 dB, single-sideband noise figure of 18 dB, IP_1dB of -9 dBm, and IIP₃ of 0 dBm, respectively, while consuming 75 mW at a 3.3-V supply. Moreover, the first and second image-rejection ratios are better than 43 and 40 dB when IF frequency ranges from 15 to 100 MHz.