Signal Modulation
Continuous wave frequency modulated radar transmits a radio signal that increases in frequency over time. An fmcw radar system compares the time-delayed echo against the original transmission to determine target distance. The frequency difference between the two signals remains proportional to the round trip travel time of the pulse.
Measurement Performance
System resolution depends directly on the bandwidth of the frequency sweep. A wider sweep allows for finer separation between two objects positioned at similar distances. Hardware constraints limit the maximum sweep rate because high-speed frequency hopping causes phase noise that degrades distance precision.
Signal processing filters remove low-frequency noise components from the mixer output to improve the detection threshold in high-interference environments.
Calibration Procedure
Instrument accuracy relies on the linearity of the frequency ramp generated by the local oscillator. Deviation from a perfect sawtooth pattern introduces errors in the distance calculation that require digital compensation. Technicians verify the slope of the sweep against reference targets with known positions to build a correction table for the processing unit.
Calibration drift occurs when temperature shifts change the characteristic response of the voltage-controlled oscillator. Periodic verification against a stable delay line maintains the specified distance accuracy over time.
Operational Boundary
Range ambiguity appears when the return signal arrives after the start of the next frequency sweep cycle. Practical applications limit the sweep period to ensure the maximum expected distance falls within the unambigous interval. Atmospheric conditions and surface reflectivity influence the signal-to-noise ratio at the receiver front end.
Digital integration of multiple sweep cycles improves detection reliability in environments that contain high levels of ambient electromagnetic background radiation. High-speed signal processing hardware restricts the effective maximum bandwidth of the system.
