This document describes the design, testing, and implementation of a switch driver circuit for a cellular signal blocking system. The author redesigned an existing switch driver board that was malfunctioning due to overheating transistors. Through testing and redesign, the author optimized the switch time and removed current spikes and interruptions. The improved switch driver board successfully switched voltages at 2.5 kHz and was integrated into the full system, which then passed all tests and was demonstrated to clients.

1. Project’s goal
Design of system witch produces the blocking of
cellular signals by transmission of two bandwidth RF
signals alternately as the output signal at the
antenna.

2. My part of project
My part of project was testing , debugging and redesign of the existed
switch driver witch was the trouble unit of the whole system.
I joined the project at the middle when RF switch board was already
prepared but it didn’t operate. The transistors on the board was
burned due to the excessively high currents flowed through them.
During my work by testing and redesign of the switch board I
succeeded to achieve the nice performance of the circuit witch
switched on frequency=2.5 kHz and more between 100v and -7v.
The board was successively integrated as the part of the whole system
, passed all tests and the system was sent to U.S.A and presented
successfully to client as a demo unit.

3. Solved problems
1) Removing of current spikes witch appeared during switch operation
2) Improvement and optimization of switch time.
3) Removing of interruption in RF switch unit caused by driver power
dripping up to 10 MHz by involving HPF into switch board.
4) Integrating and operating of the whole system as one unit until getting
the required results.
5) Power consumption optimization.
6)Documentation of the design process ,tests and changes were made.

4. The function of switch driver
•Switching on/off between two diodes in RF block
•Switching is made between 100V to -7V/-15V voltage value
•Switching frequency is 2.5 kHz

5. Block diagram

6. Switch driver scheme

7. Switch driver scheme(continue)

8. Checking of driver
Three PCB’s of driver were checked under
temperature of the room (25`C) and also
under temperature of 70`C

9. PCB#1(100V,-15V);T=25`C
•Resistors used via 100v path
•R161,163=2.2kOhm
•R5,R18=300Ohm
•Resistors used via -15v path
•R176,R178=1kOhm
•R12,R85=0.8kOhm
•I (via 100v path)=370mA
•I (via -15v path)=220mA
•T rise=19us
•T fall=19us

10. PCB#1(100V,-15V);T=25`C
•Resistors used via 100v path
•R161,163=2.2kOhm
•R5,R18=300Ohm
•Resistors used via -15v path
•R176,R178=1kOhm
•R12,R85=0.8kOhm
•I (via 100v path)=370mA
•I (via -15v path)=220mA
•T rise=19us
•T fall=19us

11. PCB#1 (100v,-15v) T=70`C
•I (via 100v path)=360mA
•I (via -15v path)=220mA
•T rise=18.4us
•T down=21us

12. PCB#2(100v,-7v) T=25`C
•Resistors and capacitors via 100v path
•R163,R161=8kOhm
•R78,R75=1.2kOhm
•C44,C34=4.7nF
•C45,C35 replaced by R=100Ohm
•Resistors and capacitors via -7v path
•R175,R176=10Ohm
•R12,R85=1kOhm
•C37,C47=20pF
•C36,C46 replaced by R=2kOhm
•I (via 100v path)=200mA
•I (via -7v path)=100mA
•T rise=24us
•T fall=24us

13. PCB#2(100v,-7v) T=25`C
•Resistors and capacitors via 100v path
•R163,R161=8kOhm
•R78,R75=1.2kOhm
•C44,C34=4.7nF
•C45,C35 replaced by R=100Ohm
•Resistors and capacitors via -7v path
•R175,R176=10Ohm
•R12,R85=1kOhm
•C37,C47=20pF
•C36,C46 replaced by R=2kOhm
•I (via 100v path)=200mA
•I (via -7v path)=100mA
•T rise=24us
•T fall=24us

14. PCB#2 (100v,-7v) T=70`C
•I (via 100v path)=200mA
•I (via -7v path)=100mA
•T rise=24.8us
•T fall= 27.2us

15. PCB#3(100v,-7v) T=25`C
•R163,R161=8kOhm
•R78,R75=1.2kOhm
•C44,C34=4.7nF
•C45,C35 replaced by R=100Ohm
•Resistors and capacitors via -7v path
•R175,R176=10Ohm
•R12,R85=1kOhm
•C37,C47=20pF
•C36,C46 replaced by R=2kOhm
•I (via 100v path)=240mA
•I (via -7v path)=110mA
•T rise=20.8us
•T fall=22.4us
•Resistors and capacitors via 100v path

16. PCB#3 T=70`C
•I (via 100v path)=250mA
•I (via -7v path)=110mA
•T rise=12us
•T fall=24us

17. Attentions and notes
•The time delay is caused during of feedback
circuit that prevents spikes of high current to
appear witch provides to the driver much
more stability and defense
•The Switch signal input should be connected
to the driver just after all other inputs are
connected ;that because of feature of HV
supply and circuit logic