Quadrature Phase Shift Keying on FPGA

An FPGA, or Field Programmable Gate Array, is a special type of chip that you can customize to act like any digital circuit you want using code. While regular computers and microcontrollers run instructions one after another like following a recipe, an FPGA can perform many tasks all at once, because it doesn’t run software , it becomes the hardware you describe. You write that behavior using special languages like Verilog or VHDL , and software like Vivado or Modelsim turns your code into a file that configures the chip’s internal wiring.

Here , we are using the FPGA to simulate and test QPSK , Quadrature Phase Shift Keying , it is a digital modulation technique used for wireless/wired communication. Modulation is the process of varying a characteristic (amplitude, frequency, or phase) of a high-frequency carrier wave to encode and transmit a low-frequency message signal. This technique is essential for communication, as it allows low-frequency signals, such as audio or data, to travel long distances over a transmission medium by being superimposed onto a high-frequency wave.

Quadrature Phase Shift Keying (QPSK) is a modulation technique that allows the transmission of multiple bits simultaneously by representing possible states with different levels and phases. It improves spectral efficiency by transmitting two bits using the same spectrum width as BPSK, with the I (in phase) and Q (quadrature) channels modulated onto carriers 90° apart.

I am using a Basys 3 FPGA Development Board for implementing the program . The Board has 16 slide switches from which a 16-bit input signal can be given , this 16-bit signal is converted to 8-bit transmission signal by pairing up consecutive bits and transmitting them 2-bits at a time. The Output is given through Monitor , the FPGA has built in VGA Cable . In the monitor , the following metrics are displayed :

• Constellation Diagram
• Input Signal Waveform
• Output waveforms :
  I-phase waveform
  Q-phase waveform
  Final Modulated Wave

So this is what I am doing with the FPGA , a demonstration into the powerful capabilities and Versatility of FPGAs , and an intro into the world of Signal processing through RTL Programming . Feel Free to reach out regarding any questions or suggestions .