In the radiation detector the pulse shaping circuit consists of CR-RC circuit and amplifier.The function of pulse shaping amplifier is to improve Signal to Noise ratio.It also act as a filter to remove the noise since it consists of CR-RC circuit which represent differentiator and Integreator . The preamplifier input given to the pulse shaping circuit generates the Gaussian Pulse as the output response. I have seen that the tailing edge of the Gaussian pulse consists undershoot. There is a need for baseline restore through Pole-Zero circuit.Why this undershoot occur in the output of pulse shaping amplifier?How does Pole-Zero adjustment removes this undershoot?
I will be very much thankful for the reply.
Dear Manoj,
Welcome,
It is so that the differentiator is effective while the integrator is not since the signal appeared as a differentiated pulse, please see the given link below.
The c-r differentiator has the response Fd(S)= r 1sc1/ 1+sc1r1= sc1r 1for 1>>sc1r1> That is your differentiator has wcut off > wmin of the pulse. With wcutoff= 1/c1r1, While your integrator Fi(S)= 1/ 1 + sc2r2,
To be effective sc2r2 must be much greater than 1 and consequently, Fi(S)= 1/ sc2r2 which means that that wmax>> w cutoff. where wctoff= 1/c2r2 This means that the filters must be adjusted to pass the pulse with slight shaping from wmin to wmax.
Multiplying the two filters to get the overall transfer characteristics one obtains:
Fi Fd approximately = sc1r 1/ sc2r2 = c1r1/c2r2 which is the condition of compensation. since the pulse in this case will preserve its shape. while removing out of band noise and interference.
This may be a scenario for the understanding and solving the problem.
The link:https://figshare.com/articles/_The_differentiated_Gaussian_pulse_in_a_time_and_b_frequency_domains_used_to_power_the_implanted_antenna_/843366
Best wishes
Dear Manoj,
Welcome,
It is so that the differentiator is effective while the integrator is not since the signal appeared as a differentiated pulse, please see the given link below.
The c-r differentiator has the response Fd(S)= r 1sc1/ 1+sc1r1= sc1r 1for 1>>sc1r1> That is your differentiator has wcut off > wmin of the pulse. With wcutoff= 1/c1r1, While your integrator Fi(S)= 1/ 1 + sc2r2,
To be effective sc2r2 must be much greater than 1 and consequently, Fi(S)= 1/ sc2r2 which means that that wmax>> w cutoff. where wctoff= 1/c2r2 This means that the filters must be adjusted to pass the pulse with slight shaping from wmin to wmax.
Multiplying the two filters to get the overall transfer characteristics one obtains:
Fi Fd approximately = sc1r 1/ sc2r2 = c1r1/c2r2 which is the condition of compensation. since the pulse in this case will preserve its shape. while removing out of band noise and interference.
This may be a scenario for the understanding and solving the problem.
The link:https://figshare.com/articles/_The_differentiated_Gaussian_pulse_in_a_time_and_b_frequency_domains_used_to_power_the_implanted_antenna_/843366
Best wishes
I would like to add that the CR combination acts as a differentiator or high pass filter. The RC combination works as a low pass filter.
Hence, the product of two transfer functions will give output corresponding to a band pass filter circuit, which will eliminate high frequency noise from harmonics etc. The low pass filter will cut off supply hum etc.
I would recommend to read ORTEC's "Introduction to amplifiers" that briefly and in a simple language describes how CR-RC shaping circuits work, why there is a noticeable undershoot at shaper output, and how to adjust Pole-Zero network to eliminate this undershoot. (just pp. 4-7 of total 12:)
http://www.ortec-online.com/download/Amplifier-Selection-Guides.pdf
http://www.ortec-online.com/download/Amplifier-Selection-Guides.pdf
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