In this research paper, a mm-wave up-conversion mixer with very wide bandwidth is investigated. With most reported designs in the mm-wave range operating at small relative bandwidths, the large potential for data transmission speeds is not harnessed. With this, more spectrally efficient high-order modulation schemes become necessary which require complex digital-to-analog circuits and digital processing, resulting in high DC-power consumption.We study a concept that provides a very large RF bandwidth; this is achieved optimizing the input and output matching networks as well as the order of feeding LO and IF signal. To prove the concept, a chip was implemented in a 130nm SiGe BiCMOS technology. With 27.2mW of DC power, a conversion gain of -13 dB is combined with suppressing the LO and third harmonic signal by 20.7 dB and 22.1 dB respectively. At 103.9 GHz of RF bandwidth around a center frequency of 245 GHz, the state of the art is advanced by 23 %. This circuit can enable BPSK operation at transfer speeds higher than 100 Gbps.