This work presents microstrip and Substrate Integrated Waveguide (SIW) based monopulse comparators (MC) working at two different frequency bands for automated target detection. Center frequencies of the comparators are 3.5 GHz and 28 GHz with their operating bands fall in the sub-6 GHz and millimeter wave frequency range. Planar microstrip line based design is adopted for making the comparator at lower band. Simulation result shows simulated impedance matching of > 14.4 dB at the input ports over 3.4-3.6 GHz. The maximum phase deviation at the sum port of the comparator is 2.2°. At the millimeter wave range of 27.75-28.25 GHz, comparators are designed for working in a single plane and dual plane configuration. SIW is used to design these two comparators at millimeter wave. Single plane MC shows average differential phases at its sum and difference ports are -1.34° and 176.58°, respectively, with a minimum simulated return loss of > 16.26 dB at the input ports. The maximum simulated phase deviation at the sum port of dual plane SIW MC is 13.8° with impedance matching > 15.5 dB for the input ports of the comparator. © 2020 IEEE.