2.4/5.7-GHz dual-band Weaver-Hartley dual-conversion downconverters are demonstrated using 0.35-μm SiGe heterojunction bipolar transistor (HBT) technology with/without a correlated local oscillator (LO) generator. In the first implementation, the correlated LO generator consists of a divide-by-two frequency divider, a frequency doubler and a single-sideband upconverter and thus LO1(=2.5×LO2) signal is generated. As a result, the downconverter with the correlated LO signals has over 39 dB image-rejection ratios for the first/second image signals (IRR1/IRR2) of the dual-conversion system at both 2.4/5.7-GHz modes while the downconverter without the correlated LO generators has a 6-dB higher conversion gain and IRR1/IRR2 of more than 44 dB with the same dc power consumption (excluding the LO generator). On the other hand, a 10-GHz Weaver-Hartley downconverter is demonstrated with a resonant LC load at the first-stage mixer to improve the conversion gain at high frequencies. The downconverter achieves a conversion gain of 8 dB with IRR1/IRR2 better than 43/40 dB.
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