DRO-Design (series-feedback)
时间：04-08
整理：3721RD
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Without experiences in designing DRO′s, I tried to develop some DRO-circuits with 2 different BJT′s (BFP405, NESG2120M05) in common emitter and series-feedback without success. The only simulation-tool I have is the freeware of ansoft designer without the possibility to simulate active devices.
To learn the functionality of a DR, the first step was to measure the S11-parameter of a quarter wavelengths in front of an open 50 Ohm-Transmission-Line placed DR. As I expected, the result was a bandpass-filter with narrow bandwidth (high Q) and a resonant frequency of 5.683 GHz.
To design the DRO, I used a design-example from the book ?Microwave Engineering?. One step was to calculate the length of the transmission line between the DR and the base of the BJT: I maximised the ΓOUT while I set ΓL=1/S11. The output-matching could be calculated by the resulting ZOut and was realised by transmission-lines. To unstable the transistor, I integrated a feedback-element at the emitter (I tried different lengths).
After building up the oscillator-circuits, in most cases the DRO′s oscillated without DR at a frequency near the ISM Band (~6 GHz). It seems that this frequency depends of the length of the transmission-lines at the emitter and base.
After placing the DR a quarter wavelength in front of the open end of the transmission-line (at the base), the frequency changed to different frequency?s near the ISM-Band (not the expected 5.683 GHz resonant frequency of the DR).
While I artificially increased the temperature, the frequency-drift over temperature (Δt≈70°C) was about 25MHz. It seems that the DR is not working properly, because we had the same temperature-drift without resonator.
Is there any possibility to find out if the DR is working?
The PDF in the attachment shows one of my DRO-Layouts.
I would appreciate it if you could give me some advice for further strategies to design a functional oscillator. Do you know any books or other literature that are useful to design a DRO? Unfortunately, the most literature i read uses tools like ADS, that i don`t have.
Mny tnx, 73
Guido
To learn the functionality of a DR, the first step was to measure the S11-parameter of a quarter wavelengths in front of an open 50 Ohm-Transmission-Line placed DR. As I expected, the result was a bandpass-filter with narrow bandwidth (high Q) and a resonant frequency of 5.683 GHz.
To design the DRO, I used a design-example from the book ?Microwave Engineering?. One step was to calculate the length of the transmission line between the DR and the base of the BJT: I maximised the ΓOUT while I set ΓL=1/S11. The output-matching could be calculated by the resulting ZOut and was realised by transmission-lines. To unstable the transistor, I integrated a feedback-element at the emitter (I tried different lengths).
After building up the oscillator-circuits, in most cases the DRO′s oscillated without DR at a frequency near the ISM Band (~6 GHz). It seems that this frequency depends of the length of the transmission-lines at the emitter and base.
After placing the DR a quarter wavelength in front of the open end of the transmission-line (at the base), the frequency changed to different frequency?s near the ISM-Band (not the expected 5.683 GHz resonant frequency of the DR).
While I artificially increased the temperature, the frequency-drift over temperature (Δt≈70°C) was about 25MHz. It seems that the DR is not working properly, because we had the same temperature-drift without resonator.
Is there any possibility to find out if the DR is working?
The PDF in the attachment shows one of my DRO-Layouts.
I would appreciate it if you could give me some advice for further strategies to design a functional oscillator. Do you know any books or other literature that are useful to design a DRO? Unfortunately, the most literature i read uses tools like ADS, that i don`t have.
Mny tnx, 73
Guido
Try to follow the recommendations presented here:
http://www.gedlm.com/DRO/DRO.asp