in the following schematic , this is the source of a high frequency signal , that will pass through a coaxial cable , the cable capacitance cause the signal to get distorted , I reduced the resistance R18 to 250Ohms , but the signal is still not satisfying , is there any other way to make it better without reducing the resistance further?

 

Hello,

How high is this mentioned frequency?
How long is the coax cable?
A driver between the MCU and coax might give better results.

Bertus

 

the signals are two inverted pwm signals , the problem is that there must be a 1 usec dead time between the two signals where they are both low , and it would be a problem if this deadtime period is received as a shorter or a longer .

the cable is about 10-15 meters

I checked the max232 and its delay was very high for me , is there another driver that would fit?

 

Hello,

It looks like you are using 5 Volts power supply.
You could try a 7407 open collector TTL buffer.
http://www.ti.com/product/sn7407

Bertus

 

Make sure the coax is matched at the source and load. Make sure the coax is correct for the highest frequency. Use diodes at the ends to quash overshoot if needed. If you want better advise, you will need to provide better details.

 

Try a simple transistor buffer. Use a small NPN, such as 2N2222A, as an emitter follower driver at the output of the 6N137. Add a 50 ohm load to ground at the far end of the coax.