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V9 Technology™ from NJRC
The new limiting value for the power level of unwanted emissions was adopted as defined in the Appendix S3 of the Radio Regulations and agreed upon in the ITU Radiocommunication Assembly. These levels of the unwanted emissions were applied to marine radar systems to be mounted on marine vessels starting from January 1, 2003.
An electron tube called a magnetron is installed as an oscillator in the transmitter section of a marine radar system. Magnetrons are most widely used in marine radar systems, because they are of low cost (although they have some unfavorable characteristics in relation to their unwanted emissions).
The unwanted emission of the solid-state oscillator mainly comprises of higher harmonics, while that of the magnetron includes:
- higher harmonics (originating from the deformation of the oscillating waveforms),
- emissions having frequencies associated with the internal resonance mode of the magnetron itself (due to multi-cavity resonance mode), and
- relatively low-frequency emissions of several tens to several hundreds of MHz, whose generation is triggered by noise (due to the drift of oscillating frequency).
Among the multi-cavity resonance modes, the resonance mode having a desired frequency is called " mode", the resonance mode wherein the number of the pairs of high-frequency electric fields is less by unity than that of the mode is called "π -1 mode". The π-1 mode generates the unwanted emission, among others, that has the maximum power emission level. (See the diagrams shown below.)
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(a)π mode |
(b)π-1 mode |
NJRC has researched this dilemma for several years and has developed its patented new V9 Technology™. V9 Technology™ is a redesign of the internal structure of the magnetron. Its technological advances offer a spectrum with a narrow bandwidth, better symmetry, shorter rise time (typically 8-17 nanoseconds) and a lower π-1 spurious emission.
See the ASC (Advanced Spectrum Controlled) magnetrons section for a listing of NJRC’s new magnetrons utilizing V9 Technology™.
