Varactor to compensate ~200MHz temperature drift for 10GHz oscillator. SMV123x/BB857?
时间：04-06
整理：3721RD
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Hello! I am searching for current mass-production easily avaiable varactor diode in SMD package (something like SC-79).
I need to compensate temperature drift in 10GHz transceiver.
I am using parallel feedback with microstrip bandpass filter as a 10GHz resonator.
Currently using low-noise FET transistor. Part of oscillator output (drain) goes to 10GHz band-pass filter, and then through phasing line to the gate of transistor. Results are very good, tried variety of transistors, much better results than in series feedback. The only problem is temperature frequency drift between transceivers.
To solve this problem I want to use cheap varactor, adding it to the beginning of phasing line, where band-pass filter starts.
Schematics is similar to this 2.4GHz VCO: http://lea.hamradio.si/~s53mv/spectana/vco.html
but i want to attach varactor to phasing line, not resonating element of band-pass filter. as at this frequency size of SMD varactor pins can affect resonator too much when attached at different points. If it does not work well, there is a way to use separate microstrip nearby. so i hope i can use "big" and cheap varactor.
Currently prescaler IC able to measure frequency +-1MHz (insufficient, will be improved).
SMV123x-079LF http://www.skyworksinc.com/uploads/d...ts/200058Q.pdf
or BB857 varactor, can i achieve at least ~200MHz tuning range?
If somebody know current production SMD varactors can be used here, please reply.
12v DC available, but something that can work with max 5v tuning preferred.
Thanks!
I need to compensate temperature drift in 10GHz transceiver.
I am using parallel feedback with microstrip bandpass filter as a 10GHz resonator.
Currently using low-noise FET transistor. Part of oscillator output (drain) goes to 10GHz band-pass filter, and then through phasing line to the gate of transistor. Results are very good, tried variety of transistors, much better results than in series feedback. The only problem is temperature frequency drift between transceivers.
To solve this problem I want to use cheap varactor, adding it to the beginning of phasing line, where band-pass filter starts.
Schematics is similar to this 2.4GHz VCO: http://lea.hamradio.si/~s53mv/spectana/vco.html
but i want to attach varactor to phasing line, not resonating element of band-pass filter. as at this frequency size of SMD varactor pins can affect resonator too much when attached at different points. If it does not work well, there is a way to use separate microstrip nearby. so i hope i can use "big" and cheap varactor.
Currently prescaler IC able to measure frequency +-1MHz (insufficient, will be improved).
SMV123x-079LF http://www.skyworksinc.com/uploads/d...ts/200058Q.pdf
or BB857 varactor, can i achieve at least ~200MHz tuning range?
If somebody know current production SMD varactors can be used here, please reply.
12v DC available, but something that can work with max 5v tuning preferred.
Thanks!
BB857 is still in production at Infineon. This can give about 4pF variation between 0 to 5V bias, which should be fine for 2% variation at 10GHz.
http://www.infineon.com/dgdl/bb837_b...13d97339a9011a