Two Case Studies - Surveyor 4D
Introduction
Surveyor 4D software is useful for monitoring RF signals, creating alarm based automatic monitoring, observing the modulation in real-time. In this document, two case studies of surveyor 4D are discussed - 1) using a mobile phone’s Bluetooth (BT) signal and 2) an Internet of Things (IoT) device i.e. LoRa signal.
Case Study with BT signal
A typical Bluetooth operation frequency range is 2400 - 2483.5 MHz. KeySight RF sensors can detect up to 6 GHz Radio Frequency (RF) signals. In this case study, we have successfully detected a BT signal using KeySight Rf sensors and Surveyor 4D software. We have tuned the software in 2.4GHz with a 20 Mz span to observe the Bluetooth signal.
1. Data Collection
When surveyor 4D software is open it will show an arbitrary range of frequency and bandwidth. For observing a BT signal, the spectrogram and spectral window should be tuned to 2.4 GHz. To set those parameters, refer to Signal Surveyor 4D Software.
The generic process is explained there. After setting up the desired frequency range, the spectrogram and spectrum will look like the below figure.
2. Results
Now, switch on your phone’s BT and observe the change in the spectrum. The presence of the signal is clearly visible both in the spectrogram as well as the spectrum. You can also see the bandwidth and signal strength of the received signal. The below figure is a snapshot of that.
3. Modulation recognition
You can further check the modulation of the signal using Surveyor 4D. A few of the most common responses from the modulation window are summarized in the below Table 1. For more details, refer to [1].
TABLE 1
For the BT signal, the modulation has been come out to be “unknown” which can be observed from the below figure.
Case study using LoRa signal
Low-Range (LoRa) equipment is a low power device that is especially used in IoT applications. The LoRa equipment used for this case study has a frequency range of 902 - 915MHz. A typical LoRa bandwidth is either 125 kHz, 250 kHz, or 500 kHz. In this case study, we have used 923 MHz operating frequency LoRa and successfully detected the signal using surveyor 4D.
1. Data Collection
For generating IoT signal, two Ronoth LoRa equipment were used - one used as sender and another one as a receiver. Both pieces of equipment were connected to the same computer. Once they are connected, they need to be activated for transmission using the command window. The steps are as follows:
Type “device manager” in your computer search bar.
Go to “Port”
Note down the port numbers for both the LoRa equipment
Open two different command window
Activate the receiver first using the example command $python radio_receiver.py COM6. Use your COM port number instead of COM6
Now activate the sender using the example command $python radio_sender.py COM7
2. Results
Once the sender and the receiver are transmitting and receiving successfully, switch to the Surveyor 4D screen. As mentioned earlier, we have used a 923 MHz operating frequency. With the LoRa signals, the screen will look like the below figure with a span of 20MHz.
The spectrogram and spectrum window with the LoRa signal will look like the below figure.
The signal is clearly visible in both the windows at around 923 MHz frequency. Now, we can check the modulation of the signal. Assign the center frequency and bandwidth you want to observe. In the below figure, it can be observed that there is another “unknown” modulation apart from the noise. In TABLE: 1 above, the reason for the “unknown” modulation is explained.
Insights
Comparing the above two case studies, the following insights can be drawn:
Characteristics of the signal: For the BT signal, we can observe the signal using multiple center-frequencies. Whereas the LoRa signal is using only one frequency.
Bandwidth: We can observe two different bandwidth from all the windows (spectrogram, spectrum, and modulation window).
Modulation: If we focus on the modulation window, we can observe that more noise is detected in the case of LoRa compared to the BT. This is because of multiple BT signal within a fixed span of frequency. The frequency chosen was 20 MHz, and within that, there are multiple BT signals, but only one LoRa signal.
Duration: We can also observe a signal duration using Surveyor 4D. From the spectrogram, it is clear that the duration of one LoRa signal is greater than one BT signal.