  We investigate the Josephson radiation of nanowire (NW)-based Josephson
junctions in a parallel magnetic field. The Josephson junction made of an InAs
NW with superconducting Al leads shows the emission spectra which follow the
Josephson frequency $f_{J}$ over the range 4-8 GHz at zero magnetic field. We
observe an apparent deviation of the emission spectra from the Josephson
frequency which is accompanied by a strong enhancement of the switching current
above a magnetic field of $\sim 300$ mT. The observed modulations can be
understood to reflect trivial changes in the superconducting circuit
surrounding the device which is strongly affected by the applied magnetic
field. Our findings will provide a way to accurately investigate topological
properties in NW-based systems.
