Second harmonic suppression in helix traveling-wave tubes
A filter structure to suppress the second harmonic component in the RF signal of a traveling-wave tube (TWT) was developed and integrated into a helical delay line. Its effect is shown in simulation and measurement.
Second Harmonic Suppression in S-Band Traveling Wave Tube Tapers
Abstract Traveling wave tubes (TWTs) operating at S-band are to be improved by suppressing the second harmonic frequency. Among the different possibilities, two techniques, namely harmonic injection and a filter helix for frequency selective signal suppression, are studied in more detail and applied to S-band tubes in both simulation and measurement. In addition, their suitability to improve tube performance by reducing the second harmonic is discussed. Moreover, filter helix implementation in TWTs with an arbitrary pitch profile along the interaction area is considered. In this context, the dependence of the pitch discontinuity reflection coefficient on several filter helix parameters is investigated. The influence of those parameters on the filter performance is shown by filter helix optimization. Measurement results of the optimized filter helix TWT are presented.
The Invariance of the Vacuum is the Invariance of the World
The following theorem is demonstrated: If the vacuum is invariant under the group generated by the space integral of the time component of a local vector current, then the Hamiltonian is invariant also. A similar theorem holds for the group generated by the space integral of a space component of a local axial-vector current.