PRF protection 2

[cimbom]

Hello,

I have a pulse repetetion frequency protection circuit (PRFPC)project. Actually I designed a five order active filter (by using two LM741) for this work. My purpose is to attenuate the input voltage of the PRFPC with the multiplied of 0.25 (If Vin=4V=> Vout=1V) at 4kHz, which is a low-pass filter.

Although the circuit performance is perfect for high duty cycle operations (>%10), it is not good for low duty cycles (<%1) because of the capacitor characteristic used in the design. Do you have better idea for this purpose?

Thank you, I love all

 

[Skogsgurra]

Is this for the scan interlock in a linear accelerator? We had the same problem and we had to do it in a little MCU where we could adapt the monitoring and the reaction time to PRF and D.C. Works wonderfully. A lot safer than the old analogue thing, that actually did not warn early enough. Result: a hole in the titanium window, ruined vacuum and more than a week of lost production. So, be careful if your application is in that direction.

 

[cimbom]

Thanks skogsgurra,

I will use the circuit as the protection circuit of power amplifer transmitter bias. Since the amplifier is allready pushed in order to get more power than the power it is able to give in CW, when the higher PRF come to the bias, the transistor blows up.

I don't have any idea about MCU, is it microchip unit or somthing?

Do you know any chip that can do this protection?

Thanks again

 

[IRstuff]

An MCU is a microcontroller, with on-board timers and other I/O functions. You can then use the timer function to determine whether the duty cycle and PRF are within limits of the amplifier.

TTFN

 

[Skogsgurra]

Yes, IRstuff. That is exactly what we did.

 

[cimbom]

Thanks guys,

Your comments are very helpful. As I understood, I have to learn MCU programing.

I have no idea about programing mcu but I think I can cope with.

Have nice days

 

[electricuwe]

I would recommend to monitor not only the PRF but also the duty cycle. You will damage your amplifier if you operate at a high duty cycle even if the PRF is within limits.

 

[nbucska]

Anyone could recommend to ealkan an MCU which is easy to learn to program ?

<nbucska@pcperipherals.com>

 

[cimbom]

Thanks elctricuwe and nbucska,

I used a monostable multivibrator to protect the amplifier against duty cycle; there is no problem with duty cycle. Still struggeling to search a mcu which is appropriate for the design.

Actually I have another debate for you guys:

If you had two signals which are in different frequencies (Let's say one is 5MHz and the other 10MHz, both signal has the same amplitude 1V) flowing on two lines. And you wanted to combine these two signals in one line without damaging the sources of two signals. What method would you use.

I thought I could use a directional coupler to do that but the wavelength of the transmission line to design a directional coupler will be very long, so does the dimensions of the coupler. Even if I had a coupler to do that job, it would give very high loss because of the super possition analysis of combining two different frequencies by a coupler.

Another method I thought was to use two diods to do this job, but this time diods will have about 0.7V loss on them and more than half of the input voltage will be lost (1-0.7=0.3V we will have)

What else can do this job.


Thanks sharing your information. Have great days forever...

 

[IRstuff]

The frequencies seem low enough to use conventional op amp summer, preceded by a couple of buffer amps.

TTFN

 

[cimbom]

Additional components and supplies are pain in the neck. Nobody wants his or her circuit be complex and expensive. What can be the easy way? Innovations are hidden in details!

 

[melone]

You could try using schotty diodes (~.3V drop), or use an open collector / drain device at the source end of your signals. Then either one can pull the line , or both at the same time for that matter. Just remember to size your pull up correctly so as not to damage the device.