Ivan_Ryger
Junior Member level 1
Dear all, please have you got experience with design of microwave oscillator with interdigital filter?
I am currently building this oscillator for spectrum analyzer project:
http://lea.hamradio.si/~s53mv/spectana/vco.html
Unfortunately the oscillator according Fig. 4 does not work. I used BFP420 transistor instead of BFP183. It has higher transition frequency and therefore lower phase shift at operation frequency. I was advised by Matjaz Vidmar to use original transistor, but i cannot get it.
I used FR4 material of thickness 0.8 mm (according to original text). I measured the fabricated interdigital filter with center line short circuited at the end. It had S21 coefficient in peak at approx. -20dB.
If i removed the short circuit on center line and connected the tuning varicap, the attenuation further increased to level -40 dB, the peak in transmission characteristic could be tuned with external voltage applied on to varractor. The attenuation seems to me quite high (maybe low varicap Q-factor or losses in FR4 at 2GHz). I silver-coated the microstrips by wet chemical process and used colophone to prevent the lines from oxidation.
I would like to design my own oscillator but i have no experience with design of coupled transmission lines.
Have you got any litterature about these oscillators?
I cannot find the s-parameters of the transistors used.
I am currently building this oscillator for spectrum analyzer project:
http://lea.hamradio.si/~s53mv/spectana/vco.html
Unfortunately the oscillator according Fig. 4 does not work. I used BFP420 transistor instead of BFP183. It has higher transition frequency and therefore lower phase shift at operation frequency. I was advised by Matjaz Vidmar to use original transistor, but i cannot get it.
I used FR4 material of thickness 0.8 mm (according to original text). I measured the fabricated interdigital filter with center line short circuited at the end. It had S21 coefficient in peak at approx. -20dB.
If i removed the short circuit on center line and connected the tuning varicap, the attenuation further increased to level -40 dB, the peak in transmission characteristic could be tuned with external voltage applied on to varractor. The attenuation seems to me quite high (maybe low varicap Q-factor or losses in FR4 at 2GHz). I silver-coated the microstrips by wet chemical process and used colophone to prevent the lines from oxidation.
I would like to design my own oscillator but i have no experience with design of coupled transmission lines.
Have you got any litterature about these oscillators?
I cannot find the s-parameters of the transistors used.