MFCW-Radar
Figure 1: VCO tuning voltage for S-MFCW
MFCW-Radar
MFCW-Radar (Multi-Frequency Continuous Waveform) is a continuous wave radar that operates on several transmission frequencies simultaneously and uses common signal processing for the echo signals. The advantage over FMCW radar is that the receiver requires a much smaller bandwidth. This type of radar generally uses spectrogram analysis of the echo signal received and mixed down into the baseband and is, therefore, able to detect and resolve two targets with different speeds but at the same distance. However, two targets with the same speed but at different distances cannot be resolved. In general, no fixed targets or tangentially flying targets can be detected with this method.
The so-called “Successive MFCW radar” (S-MFCW) does not transmit simultaneously, but uses the FMCW radar with the modulation type “staircase voltage”. This reduces the hardware effort, especially when using phased array antennas. Within these voltage steps shown in Figure 1 for tuning the VCO, usually, only the Doppler frequencies are measured. However, direct phase measurement to calculate a distance is also possible but requires that the target speed is not too high and that the change in distance during the dwell time is therefore negligible.
The MFCW method allows for highly accurate Doppler frequency measurements. This technique can be utilized to detect small drones that are hovering within a fixed target environment. Specifically, the micro-Doppler frequencies of their rotor blades are analyzed to ensure reliable detection.
