The V-LD1 is an easy-to-use 61 GHz FMCW distance radar sensor with integrated signal processing (Figure 1). No special knowledge in analogue or digital signal processing is needed to adapt the module to different applications, resulting in a fast time to market. Transmit frequency and sweep bandwidth are controlled internally, and a selection of settings is available to adapt to application requirements.

V-LD1 module mounted on evaluation PCB and the view of evaluation kit with mounted plastic lens.
Figure 1: V-LD1 module mounted on evaluation PCB and the view of evaluation kit with mounted plastic lens.

The beam width of the module itself is 170 × 60 degrees. However, RFbeam also offers a plastic lens that narrows the beam to 8 × 8 degrees (as shown in Figure 1), which is perfect for contactless tank level gauging applications. For applications requiring other beams, RFbeam offers the development of custom lens designs. Additionally, RFbeam provides full integrations of the lens into custom housings, ensuring optimal performance for specific needs. The use of a dielectric lens allows to radiate into a tank either through plastic walls, optical windows or using a watertight flange/lens assembly.

The V-LD1 module with dimensions of 12 mm × 16 mm can be integrated onto any OEM PCB using a standard SMT reflow process. Operating on a single 1.8 V power supply, it ensures low-power consumption, making it ideal for battery-operated systems. Once powered, the sensor defaults to a SLEEP mode to conserve energy. It remains in this low-power state until the host system, such as a microcontroller unit (MCU), sends a command to start a measurement. This command wakes the sensor momentarily to perform a measurement before it returns to SLEEP mode, making it ideal for battery-operated devices.

The V-LD1 needs only a connection to a power supply and a serial interface of a host (for example MCU or PC) to read out the distance measurement data and configure the sensor if needed. Further it is also possible to read out advanced processing data like the ADC or FFT values or to start a firmware update over the integrated bootloader.

Theory of Operation

The V-LD1 is a digital FMCW distance measurement sensor and consists of an analogue RF frontend and a powerful signal processor with a fully digital serial interface. The RF frontend features a PLL controlled transmitter with a FMCW modulation mode and one receiver. The signal processing unit controls the FMCW modulation and samples the ADC values for further processing.

A range FFT is then calculated to measure the distance to all targets inside of the antenna beam. The sensor can separate targets based on the distance resolution of the used distance setting. Further the signal processing is capable to compute a high accuracy distance of one target if this option is enabled. The user has full access to analog sampled signals and FFT raw data.

Distance Range

The sensor allows setting the maximum unambiguous distance measurement range, with options of 20 m or 50 m. The resolution depends on whether high-precision mode is enabled. In low-precision mode, the resolution is 3.934 cm at 20 m and 9.943 cm at 50 m.

Precision

By default, the sensor operates in high-precision mode. For single targets the accuracy is typically 1 mm with an accuracy of ±5 mm for both range settings and over specified temperature range. The high accuracy mode can be turned off to reduce computation time and power consumption, which can be advantageous for less demanding applications.

Distance Filter

To filter out unwanted targets, a minimum and maximum distance range can be configured. This filter adjusts the search area in the FFT spectrum, enabling to focus on specific distance ranges of interest or exclude objects at the bottom of the tank or near the top.

Target Filter

The target filter parameter allows choosing which target to measure. Options include measuring the distance to the strongest target above the threshold, the nearest target, or the farthest target.

Threshold Offset

This parameter sets the distance in dB between the raw FFT data floor and the threshold line. Lowering the offset increases sensitivity, making the sensor more responsive to weaker signals, while raising the offset reduces sensitivity, helping to filter out less significant measurements. The threshold offset is displayed as a red line in the control panel view of the FFT signal.

Chirp Integration Count

This feature controls the number of FMCW sweeps integrated per measurement, which can lower the noise floor. This is useful for measuring low-reflective materials like oil, grain or animal feed. Increasing the chirp integration count reduces the FFT noise floor and improves the signal-to-noise ratio, though it also extends measurement time and increases power consumption.
 
control panel software
Figure 2: Screenshot of the control panel software.

V-LD1 Evaluation Kit with Control Panel Software

To enable a fast development, RFbeam provides the V-LD1 evaluation kit, a powerful tool to evaluate the use of the V-LD1 for your application idea. The kit consists of a PCB with a mounted V-LD1 sensor in the centre together with the focusing lens. Further, it features an easy connection to a PC over a simple USB connection without the need of an external power supply. With the supplied powerful Control Panel software (Figure 2), the development time is reduced drastically. All the sensor parameters can be modified using the Control Panel. The influence of changed parameters can be directly checked in the real-time views of the software. The Control Panel features a lot of different views to analyse the measured data in detail. A special view of a tank level display is also provided. It is possible to record all measured data and replay it directly in the software to analyse different application scenarios offline without the sensor. To realize the own application ideas, a Python script is available from RFbeam to read out the distance information and to set the parameters of the V-LD1 module. The datasheets of the V-LD1 module and V-LD1 evaluation kit can be downloaded from our website.

RFbeam microwave is a leading manufacturer of 24 GHz and 60 GHz radar modules. Production takes place at certified partners in Switzerland and other countries. The products are exported worldwide. Key markets are traffic sensors, security and movement detection and industrial sensing.