A Wideband Two-Stage Double Balanced Mixing Structure for Mapping the In-Out Overlapped Frequency Bands

Abstract

A wideband two-stage mixing structure is proposed for multi band frequency mapping of the subsystems with overlapped input and output frequency bands. The proposed structure circumvents the image and leakage problems which are the major challenges in applications with overlapped input and output frequency bands. In such cases, the image and leaked harmonics cannot be filtered because they are inherently located in the working band. The challenges are overcome by using the proposed two-stage frequency mapping structure with a fixed and a variable local oscillator in the first and second stages of the mixers, respectively. By applying the proposed structure followed by the instructions to set the variables, filtering requirements become more relaxed. In addition, GaAs MMIC double balanced mixers are employed in this design to perform multi tune mixing. We have designed and investigated a test board as a real case of overlapped frequency mapping. It was fabricated on the RF Rogers-4003c substrate for the test and verification of the proposed idea. The test board can map any frequency band from 1 GHz to 4 GHz to the output frequency band 1 GHz to 5 GHz. The total gain variation across the whole frequency band was observed to be less than 5 dB.