Abstract: An ignition unit produces an ignition in a combustion chamber of a combustion engine in the following manner. The ignition unit comprises a radiofrequency resonator that radiates a plasma-creating radiofrequency field into the combustion chamber. The ignition unit further comprises a microwave resonator that radiates a plasma-boosting microwave field into the combustion chamber. In an embodiment, the microwave resonator has an output surface to which the combustion chamber is exposed when the ignition unit is fitted on the combustion engine. The radiofrequency resonator may comprise an electrode that is at least partially embedded in the microwave resonator. The electrode may have a tip that is located at a distance from the output surface so that the microwave resonator provides a barrier between the tip and the output surface.