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  1. obinobi

    RF2638 as a BPSK modulator

    Hi I have asked RFMD about acceptable voltage level. In case of single ended signal (IF- AC grounded through 1nF) safe voltage is close to Vcc (+3.0 V).Higher will damage the IC. Regarding transformer I think I have to remove him. Voltage on coil is equal: U=L x di/dt So in case of...
  2. obinobi

    RF2638 as a BPSK modulator

    Hi These resistors are 1kOhm not 10k as is on schematic. They role is to decrease voltage level from FPGA (3.3V logic) to smaller value acceptable by RF2638. FPGA works as a PRN generator. I didn't find any details in datasheet what is acceptable level for IF pins but I suppose it is +3 dBm...
  3. obinobi

    RF2638 as a BPSK modulator

    Hi Thank you for response. Data is comming through PRN pin connected to FPGA. Coaxial connector is for test purpose only. I was trying to add series resistor (about 100 Ohm) between C9 and transformer to decrease rise/fall time of the current - remove distortion of rectangular wave. But it...
  4. obinobi

    RF2638 as a BPSK modulator

    Hi I have attached schematic. The C9 is 10 nF. My IF rectangular wave is distorted a little bit. But it is not source of problem. The IF is driven by FPGA port. The series resistors have 1kOhm. Best regards
  5. obinobi

    RF2638 as a BPSK modulator

    Hi I would like to ask about implementation of RF2638 as a direct BPSK modulator. I see following problem - my output signal looks like ASK modulated signal not BPSK. Rectangular wave is connected to RF2638 through transformer. Any hints? Best regards
  6. obinobi

    Problem with ADL 5535

    Hi Thank you for yours responses. I have replaced an amplifier and after soldering I measured resistance between output and GND and it's 16 Ohm. So I am worry that IC is damaged during soldering - ESD or too high temperature. After connecting to the power supply current protection shows overload...
  7. obinobi

    Problem with ADL 5535

    Hi I build a simple PCB with based on RF amplifier ADL5535 very similar to eval board from Analog Devices. But I have following problem. After some short time - less than 1 or 2 minutes I observe rapidly increasing output current from DC power supply and it looks that output is almost shorted to...
  8. obinobi

    Opinion wanted: Should I buy Altium Designer ?

    cadstar vs. altium Hello I have used following tools: - Altium Designer - Mentor Graphics DxDesigner and Expedition - Zuken Cadstar In my oponion Cadstar is quite good but I prefer Altium because in my opinion featerues related with setting rules, drawing etc are better and more advanced...
  9. obinobi

    Anyone want to get involved in Digital Radio project

    Hello I am electronics design engineer with experience in analog and digital electronics (programming FPGA too), PCB design plus some experience with RF. If you are interested please contact with me via PM. Best regards
  10. obinobi

    No thermal relief at high current DC-DC converter?

    pcb thermal relief rule Hello It depends from kind of pads without thermal relief. In case of THT it shouldn't be a problem but in case of SMD it depends from manufacturer. Few rules which help you to design a layout without thermal reliefs: - in case of SMD components like resistors or...
  11. obinobi

    Looking for a DxDesigner and Expedition tutorial for PCB designing

    Hello I have question regarding DxDesigner and Expedition. Do you have contact with any tutorial which may drive me through PCB design process? Best regards
  12. obinobi

    crystal, EMI and capacitor

    Hello So you may implement shielding of clock net and oscillator. I mean ground plane under and copper plane nearby the crysta connected together through viasl. It's should be enough. Best regards
  13. obinobi

    crystal, EMI and capacitor

    Hello Did you want to use 40 MHz for some external bus clocking? If yes you may add a RC on a clock net (but not on a oscilator) circuit to increase fall and rise time of clock signal. It will decrease higher harmonics of the clock signal. Best regards
  14. obinobi

    How to configure 4 layer pcb

    4 layer pcb recommendation Hello I just want to share with you some information about 20-H rule. You may find in the internet some documentation which describes 20-H rule and impact on radiated emission. Some simulation and measurements show that in some cases such power plane topology may...
  15. obinobi

    Where to get a pre-routed BGA footprint for XILINX parts ?

    bga pcb layout Hello You have to consider number of layers in PCB required for proper layout. It will have impact on decoupling capacitors placement. Best regards
  16. obinobi

    How to configure 4 layer pcb

    4-layer pcb layout gnd signal Hello So I think that you may use configuration proposed above. If you think that you will have problems with radiated emission (in case of plastic housing) you may route noisy traces on third layer. But remember about having a proper distance from noisy tracks to...
  17. obinobi

    How to configure 4 layer pcb

    internal layer gnd vcc frequency Hello Below is my proposal Top layer - routing for high speed signal First internal - solid ground plane Second internal - power supply layer Bottom layer - ground plane + routing Advantage of these solution is good power decoupling. Disadvantage is that high...
  18. obinobi

    Simulation of radiated emission

    Hello Please find in attachment and link below some pictures of near field probe. http://www.conformity.com/artman/publish/printer_168.shtml Best regards
  19. obinobi

    Simulation of radiated emission

    Hello Below there is a link to probe manufacturer. http://www.hameg.com/330.0.html?L=0 The cost should be less than 900 Euro. If you want to made near field probe you may use semi rigid coaxial cable like below. **broken link removed** If I find some articles about making near field probes I...
  20. obinobi

    Simulation of radiated emission

    Hello I have proposal of other approach to your problem. Did you try to find source of problems using near field probe connected to spectrum analyzer? I am just asking because building a model of your PCB may take a big amount of time (I am not familiar with CST - so I am not sure that you may...

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