In this article, we will present a practical solution to the challenges faced in mobile wireless communication systems. With the issuance of 3G licenses, China has officially entered the 3G era, bringing both opportunities and new challenges for telecom operators and mobile device manufacturers. As mobile phones communicate wirelessly, issues such as frequency band control, signal quality monitoring, and power management become critical. Spectrum analyzers, often referred to by RF engineers as "RF multimeters," offer a powerful tool to address these challenges effectively.
**Question 1: Each carrier must manage its own frequency band**
The International Telecommunication Union (ITU) strictly defines frequency bands for different communication services, including industrial, scientific, fixed, mobile, and satellite communications. Even within the same frequency band, there are specific allocations. If a carrier’s bandwidth exceeds its allocated range, it can cause interference with other services and even affect its own communication quality. Therefore, testing the bandwidth and signal energy concentration is essential to ensure compliance and performance.
**Question 2: Ensuring high-quality communication signals**
During wireless communication, noise from various sources can degrade signal quality. This noise affects the signal-to-noise ratio (SNR), which is crucial for maintaining clear and reliable communication. Monitoring SNR helps identify and mitigate signal degradation, ensuring better user experience.
**Question 3: Addressing breathing and near-far effects**
In wireless networks, the "breathing effect" occurs when interference in one cell causes the base station's effective coverage area to fluctuate. Similarly, the "near-far effect" arises when a mobile device transmits at maximum power, leading to excessive radiation when it is close to the base station. To combat this, real-time power control is necessary, which requires continuous monitoring of signal strength.
Spectrum analyzers like the RIGOL DSA1030A are ideal tools for solving these issues. The DSA1030A offers a frequency range of 9 kHz to 3 GHz, a display average noise level of -148 dBm, and excellent phase noise performance. It also includes advanced features like ACP (Adjacent Channel Power) and OBW (Occupied Bandwidth) measurements, making it suitable for analyzing TD-SCDMA signals and other wireless communication standards.
For example, using ACP measurement, you can assess the main channel power, adjacent channel power, and the signal-to-noise ratio between them. In a TD-SCDMA test, the main channel energy was measured at -10.69 dBm, concentrated within a 1.6 MHz bandwidth, meeting the standard requirement. Adjacent channel suppression levels were -51.32 dB and -51.66 dB, which are sufficient for most applications.
OBW measurement helps determine if the signal's energy is contained within a specified bandwidth. By setting the power ratio to 99%, the occupied bandwidth was found to be 1.396666 MHz, confirming the signal's compliance with design specifications.
To address the third issue, the Pass/Fail function on the DSA1030A allows users to define upper and lower limits for signal measurements. When enabled, the analyzer automatically checks if the signal meets the criteria, stopping the test if it fails and highlighting the problematic frequencies and amplitudes.
Additionally, the DSA1030A supports saving and loading measurement settings, which streamlines the process and reduces errors. Users can store configurations on a USB drive and transfer them between devices, making it easy to replicate tests across different locations. Measured data can also be exported to a computer for further analysis or reporting.
Overall, spectrum analyzers play a vital role in managing and monitoring wireless communication systems, ensuring optimal performance, minimizing interference, and improving signal quality. Whether for troubleshooting, compliance testing, or performance optimization, these tools are indispensable in modern mobile communication environments.
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