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DISH SETUP: Single sat, Multi-Sat & Motorised
KA Band section
Increasing the Hughes LNB oscillator range
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<blockquote data-quote="Vipersan" data-source="post: 898166" data-attributes="member: 325666"><p>Hmm ..</p><p>seriously doubt its just shielding ..</p><p>Basic principles of DRO operation..require a resonance chamber in which the puck is located ...or it simply wont oscillate correctly..</p><p>Particularly at such high frequencies.</p><p></p><p><strong>4. Mechanical Consideration</strong></p><p></p><p>In a DRO, the electrical layout is only one aspect of the oscillator design. Mechanical interests also highly influence the local oscillator (LO)’s performance. The cavity’s size and height have loading effects on the LO which can reduce the phase noise performance and create an unwanted frequency drift over temperature. Under best conditions, the DR would be free to resonate in free space, but because of obvious real estate consideration, the LO needs to be constrained within a shielded cavity. The rules-of-thumb dictates that in order for the cavity to have a reasonable thermal and loading effects, the cavity should be at least three pucks high and three puck’s diameter wide. This height requirement is one reason most DRO designers prefer to set their DR on a standoff, so that the housing or PCB on which the DR usually rests does not affect the resonator’s performance. The PCB material’s mechanical integrity also needs careful consideration because of LO drift over temperature and long term aging effects, especially if the cavity is resting on the PCB.</p><p></p><p>Finally, the fine tuning and adjustment of the DRO will be set through a tuning screw that will increase the DR’s resonant frequency as it closes the electrical field above the puck. This should provide as much 80 MHz of tuning range. However, it is important to notice that tuning the frequency with a tuning screw is achieved at the cost of reduction in both unloaded Q and temperature stability. This worsen of temperature stability is due to the increasing slope of the tuning curve as the metal plate gets closer to the DR surface.</p></blockquote><p></p>
[QUOTE="Vipersan, post: 898166, member: 325666"] Hmm .. seriously doubt its just shielding .. Basic principles of DRO operation..require a resonance chamber in which the puck is located ...or it simply wont oscillate correctly.. Particularly at such high frequencies. [B]4. Mechanical Consideration[/B] In a DRO, the electrical layout is only one aspect of the oscillator design. Mechanical interests also highly influence the local oscillator (LO)’s performance. The cavity’s size and height have loading effects on the LO which can reduce the phase noise performance and create an unwanted frequency drift over temperature. Under best conditions, the DR would be free to resonate in free space, but because of obvious real estate consideration, the LO needs to be constrained within a shielded cavity. The rules-of-thumb dictates that in order for the cavity to have a reasonable thermal and loading effects, the cavity should be at least three pucks high and three puck’s diameter wide. This height requirement is one reason most DRO designers prefer to set their DR on a standoff, so that the housing or PCB on which the DR usually rests does not affect the resonator’s performance. The PCB material’s mechanical integrity also needs careful consideration because of LO drift over temperature and long term aging effects, especially if the cavity is resting on the PCB. Finally, the fine tuning and adjustment of the DRO will be set through a tuning screw that will increase the DR’s resonant frequency as it closes the electrical field above the puck. This should provide as much 80 MHz of tuning range. However, it is important to notice that tuning the frequency with a tuning screw is achieved at the cost of reduction in both unloaded Q and temperature stability. This worsen of temperature stability is due to the increasing slope of the tuning curve as the metal plate gets closer to the DR surface. [/QUOTE]
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DISH SETUP: Single sat, Multi-Sat & Motorised
KA Band section
Increasing the Hughes LNB oscillator range
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