  CORSIKA 8 is a new framework for air shower simulations implemented in modern
C++17, based on past experience with existing codes like CORSIKA 7. The
flexible and modular structure of the project allows the development of
independent modules that can produce a fully customizable air shower
simulation. The radio module in particular is designed to treat the signal
propagation and electric field calculation to each antenna in an autonomous and
flexible way. It provides the possibility to simulate simultaneously the radio
emission calculated with two independent time-domain formalisms, the "Endpoint
formalism" as implemented in CoREAS and the "ZHS" algorithm as ported from
ZHAireS. Future development for the simulation of radio emission from particle
showers in complex scenarios, for example cross-media showers penetrating from
air into ice, can build on the existing radio module, re-using the establishes
interfaces. In this work, we will present the design and implementation of the
radio module in CORSIKA 8, and show a direct comparison of radio emission from
air showers simulated with CORSIKA 8, CORSIKA 7 and ZHAireS.
