  Giant cluster radio relics are thought to form at shock fronts in the course
of collisions between galaxy clusters. Via processes that are still poorly
understood, these shocks accelerate or re-accelerate cosmic-ray electrons and
might amplify magnetic fields. The best object to study this phenomenon is the
galaxy cluster CIZA J2242.8+5301 as it shows the most undisturbed relic. By
means of Giant Metrewave Radio Telescope (GMRT) and Westerbork Synthesis Radio
Telescope (WSRT) data at seven frequencies spanning from 153 MHz to 2272 MHz,
we study the synchrotron emission in this cluster. We aim at distinguishing
between theoretical injection and acceleration models proposed for the
formation of radio relics. We also study the head-tail radio sources to reveal
the interplay between the merger and the cluster galaxies. We produced spectral
index, curvature maps and radio colour-colour plots and compared our data with
predictions from models. We present one of the deepest 153 MHz maps of a
cluster ever produced, reaching a noise level of 1.5 mJy/beam. We derive
integrated spectra for four relics in the cluster, discovering extremely steep
spectrum diffuse emission concentrated in multiple patches. We find a possible
radio phoenix embedded in the relic to the south of the cluster. The spectral
index of the northern relic retains signs of steepening from the front towards
the back of the shock also at the radio frequencies below 600 MHz. The spectral
curvature in the same relic also increases in the downstream area. The data is
consistent with the Komissarov-Gubanov injection models, meaning that the
emission we observe is produced by a single burst of spectrally-aged
accelerated radio electrons.
