A modular electronics enclosure for reducing electromagnetic interference (EMI) is disclosed. The electronics assembly includes a first electronic component having an output, a second electronic component having an input with an input impedance, and a circuit matching element having an input coupled to the output of the first electronic component and an output coupled to the input of the second electronic component. The output of the circuit matching element is configured to provide an output impedance that matches the input impedance of the second electronic component. The electronics assembly also includes a conductive surface that forms a volume that encloses the first electronic component and the circuit matching element. All non-conductive passages from the volume to the external environment have at least one cross-sectional opening having a continuous conductive perimeter with a maximum linear length within the opening of less than one quarter wavelength of a maximum shielding frequency.