SAW Sensor - Why is my circuit not oscillating?

[saviobez]

First, sorry for the bad english.
It's not the first time I've been looking for help on this circuit on the forum.
I'm from Brazil, I'm doing a university project using which basically consists of using a colpitts oscillator with differential pair, with a SAW sensor in its feedback loop. The SAW sensor has a frequency of 117MHz, and minimal insertion losses of ~-31dB. The challenge lies in designing the oscillator so that the gain compensates for the sensor losses. The SAW sensor model for Spice was used from another work (a master's thesis).

I managed to get my Colpitts Oscillator with differential pair oscillating at ~117MHz, but when I add the SAW the oscillation stops.

I'm not able to identify where exactly is the error of my circuit. Whether it's in the SAW model or my oscillator.
I would like any kind of help, be it articles or basic observations about my circuit.

Attached, I will put the images of the models used along with my SPICE file.

Thanks.

 

[deruik]

To begin with, sorry for the awful english. It's not whenever I've first been searching for help on this circuit on the gathering. I'm from Brazil, I'm doing a college project utilizing which essentially comprises of utilizing a colpitts oscillator with differential pair, with a SAW sensor in its criticism circle. The SAW sensor has a recurrence of 117MHz, and negligible inclusion misfortunes of ~-31dB. The test lies in planning the oscillator with the goal that the addition makes up for the sensor misfortunes. The SAW sensor model for Spice was utilized from another work (an expert's proposal). I figured out how to get my Colpitts Oscillator with differential pair wavering at ~117MHz, yet when I add the SAW the swaying stops. I'm not ready to recognize where precisely is the blunder of my circuit. Whether it's in the SAW model or my oscillator. I would like any sort of help, be it articles or fundamental perceptions about my circuit. Appended, I will put the pictures of the models utilized alongside my SPICE record. Much appreciated.

 

[Sunnysky]

To begin with, sorry for the awful english. It's not whenever I've first been searching for help on this circuit on the gathering. I'm from Brazil, I'm doing a college project utilizing which essentially comprises of utilizing a colpitts oscillator with differential pair, with a SAW sensor in its criticism circle. The SAW sensor has a recurrence of 117MHz, and negligible inclusion misfortunes of ~-31dB. The test lies in planning the oscillator with the goal that the addition makes up for the sensor misfortunes. The SAW sensor model for Spice was utilized from another work (an expert's proposal). I figured out how to get my Colpitts Oscillator with differential pair wavering at ~117MHz, yet when I add the SAW the swaying stops. I'm not ready to recognize where precisely is the blunder of my circuit. Whether it's in the SAW model or my oscillator. I would like any sort of help, be it articles or fundamental perceptions about my circuit. Appended, I will put the pictures of the models utilized alongside my SPICE record. Much appreciated.

Try an attenuator pad in your oscillator feedback to determine the surplus gain that it has and will be needed to overcome the SAW s21 losses.

 

[Sunnysky]

The C pad doesn't seem to work with the lack of gain >=1 at 0 deg. The power on oscillation decay time and phase shift from input to output ought to tell you the problem. https://www.researchgate.net/public..._an_EMC-Compliant_UHF_Oscillator/figures?lo=1