Microwave Imaging (MI) of breast cancer is an emerging non-invasive and non-ionizing technique for breast cancer diagnosis based on microwave radiation backscattered by breast tissues. Usually, MBI explore dielectric properties of breast tissues to increase the imaging contrast between tumor and healthy tissue through an Inverse Image Reconstruction Algorithm. Furthermore, MBI systems could be cost-effectively, compact and recent developments drive them to wearable soon. Even X-ray Mammography is the gold-standard for imaging tumors inside breast; it still is low contrast for early diagnostic, painful and age- and dose-restricted because ionizing radiation. Then, in long-term, our group is motivated to develop MBI technique and cost-effectively wearable systems for in vivo early diagnosis of breast cancer as a complimentary to X-ray Mammography. In short-term, we had been designing our systems by simulations, manufacturing and initial in vitro tests in lab. This work presents initial results of design and simulation of a system based on hard and/or flexible antennas ranging between 0.001 GHz to 3 GHz for in vitro experimentation. In detail, two different shapes (rectangular patch and circular slot) of Micro strip Patch antennas were designed and simulated in FR4, Cotton, Polyester and Pyralux Polyimide (for Flexible antennas) materials. The resonance frequency of antennas depends on permittivity of substrate material and its geometry, so the High Frequency Simulation Software (HFSS) simulated scattering parameters of designed antennas, which were also tested on mimic-phantoms of breast. The simulation of rectangular patch and bow-tie antennas resulted on a like-Gaussian curve of microwave emission / detection peaked at 1.9-2.7 GHz with ~50-90MHz band width.