Maximum output power of Base Station

5G is a revolutionary technology that brings super-fast speeds, quick response times, and the ability to connect tons of devices at once. To make sure 5G networks work smoothly and safely, careful testing is a must. One key test is measuring how much power the base stations (the big antennas that send out the 5G signals) are using.

Total output power refers to the maximum power level a 5G base station can transmit across its assigned frequency range.

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Think of a 5G base station like a giant speaker that broadcasts the 5G signal. The total output power is like the volume control for that speaker. Measuring this "volume" is super important for a few reasons:

• Good Reception: Just like you want your music to be loud enough to hear but not so loud it hurts your ears, 5G signals need the right amount of power. Too low, and your phone won't get a good signal; too high, and it might cause problems for other networks.
• Following the Rules:? There are rules about how loud the "speaker" (base station) can be, so it doesn't interfere with other things.? Measuring the power ensures these rules are followed.
• Protecting the Equipment:? Just like playing music too loud can damage your speakers, too much power can harm the base station.? Checking the power level keeps everything running smoothly and safely.

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Even though 3GPP TS 38.521 mainly focuses on testing 5G devices, it gives us clues about how power measurements fit into the big picture of 5G testing:

• Power Control (Uplink Power Control):? Imagine your 5G phone as a walkie-talkie. It talks to a base station, adjusting its power up or down depending on how well it hears the base station. This saves battery and keeps the connection strong.
• Power Limits (Maximum and Minimum Output Power): 3GPP TS 38.521 checks if your phone can shout (maximum power) and whisper (minimum power) as needed. This is like testing if your walkie-talkie can work close to someone or from far away.
• Clear Messages (Error Vector Magnitude (EVM)): EVM is like checking if your walkie-talkie message is clear, not garbled. The test makes sure your phone sends clear messages at all power levels, even when shouting or whispering.
• Staying in Your Lane (Spectral Emissions):? The test also ensures your phone doesn't talk over other walkie-talkies on different channels. This is like making sure you're not interrupting others' conversations.

General Testing Procedure for Total output power

Setup:

• Connect: Use RF cables to connect the 5G device or base station (the Device Under Test or DUT) to the spectrum analyzer's input. Ensure proper impedance matching and use attenuators if necessary to protect the analyzer.
• Configure Analyzer: Set the spectrum analyzer's reference level, frequency span, resolution bandwidth (RBW), and other parameters according to the test specifications (e.g., 3GPP standards, manufacturer guidelines).

Calibration:

• Zero Calibration: Perform a zero calibration to establish a baseline measurement with no input signal. This accounts for any background noise in the system.
• Reference Level Calibration: Calibrate the analyzer's reference level using a known signal source. This ensures accurate power readings throughout the test.

Signal Transmission:

• Activate DUT: Initiate the 5G device or base station to transmit the desired signal (e.g., a specific 5G NR test model).
• Capture Signal: The spectrum analyzer will capture the transmitted signal, displaying it on the screen.?

Measurement Analysis:

• Identify Peak Power: Observe the spectrum display and locate the peak power of the transmitted signal. This is the highest point on the graph (usually in dBm).
• Total Channel Power: Calculate or read the total channel power, which integrates the power across the entire signal bandwidth.
• Power Spectral Density: Analyze the power spectral density (PSD) to understand the distribution of power across different frequencies within the signal.

Comparison and Verification:

• Compare to Specifications: Compare the measured power values (peak, total channel, PSD) against the specified limits. Check for compliance with regulatory standards and manufacturer specifications.

Key Checks for Accurate Measurements

To achieve reliable and accurate total output power measurements, several factors need to be carefully considered:

• Attenuation: An attenuator is typically used between the base station and the signal analyzer to protect the analyzer's sensitive components and ensure accurate readings.
• Multiple Ports: If the base station has multiple output ports, all ports except the one being measured should be properly terminated to prevent reflections that could affect the measurement.
• Measurement Points: To account for frequency-dependent variations, measurements should be taken at the upper, middle, and lower frequencies within the base station's assigned frequency range.

Challenges in 5G Total Output Power Measurement

5G presents unique challenges for Total output power measurements due to following reasons:

1. Wider Bandwidths: 5G utilizes wider bandwidths compared to previous generations, making accurate power measurements more complex. Measurement systems need to handle these wider bandwidths without sacrificing accuracy.
2. Higher Frequencies: 5G's expansion into mmWave frequencies introduces challenges related to path loss, signal propagation, and antenna characteristics, requiring specialized measurement setups.
3. Beamforming: 5G's use of beamforming technology, where signals are focused in specific directions, necessitates sophisticated measurement techniques to accurately capture and assess the power in dynamic beam patterns.
4. Device Complexity: The increasing complexity of 5G devices, with multiple antennas and complex signal processing, adds to the difficulty of isolating and measuring individual power components.

Thanks everyone

Ravi Shekhar

reference : TS 38.521 ,38.104 ,Keysight

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