QPSK and QAM Bandwidth Calculation

The bandwidth for a QPSK (Quadrature Phase Shift Keying) signal can be estimated using the following formula:

Bandwidth (B) = Rb / 2

Where:

• Rb = Bit rate

Example Calculation for QPSK:

Let’s say we have:

• Input: Bit rate = 1 Mbps

Then, the bandwidth would be:

Bandwidth = 1 x 10^6 / 2 = 500,000 Hz or 500 KHz

For QAM (Quadrature Amplitude Modulation), the bandwidth is calculated as follows:

Bandwidth (B) = Rb / log2(M)

Where:

• Rb = Bit rate
• M = Number of different symbols

64-QAM Calculation

Here’s an example calculation for 64-QAM:

• Input #1: Rb = 1 Mbps
• Input #2: M = 64

Then, the bandwidth is:

Bandwidth = 1 x 10^6 / log2(2^6) = 1 x 10^6 / 6 = 166,667 Hz = 166.67 KHz

256-QAM Calculation

Let’s look at an example for 256-QAM:

• Input #1: Rb = 1 Mbps
• Input #2: M = 256 = 2^8

The bandwidth calculation is:

Bandwidth = 1 x 10^6 / log2(2^8) = 1 x 10^6 / 8 = 125,000 Hz = 125 KHz