As it turns out, one could surely bet on an image that pops into your mind when the word RADAR is perceived. In almost a hundred years of its heritage, the RADAR device has managed to make a way from a bulky, rotating, and oversized installation to small-sized embedded electronics of today. Sizes and technologies do change, but the word RADAR still means the same – radio detection and ranging. In the meantime, as the RADAR considered in this article did lose its size and power, it gained so much more in return, in terms of integration level and versatility. Needless to say, any reader of this article has already had a close encounter with some kind of embedded RADAR by this time.
The main advantages of technology that enabled the use of RADAR in a smaller form factor, are those in the field of monolithic microwave integrated circuits (MMIC). This terminology corresponds to all integrated microwave devices, but the RADAR principles and techniques are the ones most important in this case. To properly address them, a sentence or two must be stated.
CW and FMCW Techniques
The continuous-wave (CW) technique is based on the principle of the Doppler effect. In such a realization, the RADAR device emits a constant frequency signal continuously into the surrounding space. If the traveling signal hits an appropriate object (the target) in its vicinity it will reflect back. The RADAR then perceives the reflected signal as an echo. The change in phase between the emitted and echoed signal is used to calculate the target’s velocity.
In the case of the frequency-modulated continuous-wave (FMCW) technique, the time delay between the emitted and echoed chirp is used for measuring the distance of the target(s). The emitted and echoed signals are mixed early on in the signal processing chain, then they are quantized and relayed across the platform for further processing. The final result of such processing methods is numeric parameters of distance, position, or velocity of the target (if needed all parameters are available simultaneously).
Mentioned techniques are oftentimes built in the integrated circuits. Even though the development of such devices is an ongoing work, a broad range of commercial devices are available off-the-shelf. To analyze and use one of them as an example, Infineon’s BGT24MTR11 RADAR IC is selected. The BGT24MTR11 is a 24 GHz radar, capable of utilizing both the CW and FMCW techniques. Besides the IC, a few more components are necessary, such as external PLL and some additional amplifiers. To speed up the development process an Infineon’s development kit ‘Distance2Go’ is acquired since it features BGT24MTR11 on board.
Some of the BGT24MTR11 features are:
- Measuring the distance of multiple targets in a user-configurable range.
- Detecting motion, presence, speed, and direction of movement (approaching or retreating) for human targets
- Small form factor: 5 x 3.6 cm
- Operational in different weather conditions such as rain, fog, etc.
- Can be hidden in the end application as it detects through non-metallic materials
Throughout this blog post series, an in-depth analysis of the basic operations for the selected RADAR IC is planned. The capabilities, limitations, signal processing, and implementation steps are to be disclosed in the following posts.