Signal-to-Noise Ratio

SNR (Signal to Noise Ratio) is the fundamental metric used to evaluate the performance of a radar system.

This ratio compares the received signal power from a target against the background noise,

that originates within the system itself, primarily from thermal and phase noise.

 

 

 

 

 

 

1. Impact of SNR

A high SNR is critical to minimize false alarms and enhance measurement precision.

If the SNR is too low, the target signal becomes indistinguishable from the noise floor,

leading to missed detections or increased False Alarm Rates.

	A higher SNR reduces detection errors and enhances measurement precision.
	False alarms occur when time-varying noise is too high

2. Supplementary: SCNR

SCNR (Signal-to-Clutter-plus-Noise Ratio) is a more realistic performance metric than SNR.

In real-world applications, the system is limited not just by internal noise, but by clutter.

Clutter refers to unwanted reflections from stationary objects like walls, furniture, or appliances.

Clutter can lead to false alarms and measurement errors by interfering with target detection.

 

 

 

 

3. Noise Source in Radar

 

Category	Noise Source	Spectrum Characteristics
Thermal Noise	LNA, Mixer, ADC, resistors, internal RF receiver thermal noise	Flat noise floor across the entire spectrum
Static Clutter	Walls, floor, ceiling, furniture, fixed objects, stationary human body	Strong peak near 0 Hz Doppler or fixed range bins
Dynamic Clutter	Curtains, fans, air conditioners, plants, vibrating or moving objects	Spread energy in low Doppler regions with temporal variation
Multipath Clutter	Reflections from walls, ceiling, floor, metallic objects, corner reflections	Ghost peaks at incorrect range/doppler positions
External Interference	Other radars, Wi-Fi, Bluetooth, LTE/5G, SMPS, motors, fluorescent lamps, inverters	Narrowband tones, spurs, spikes, or elevated spectrum regions

 

4. SNR Calculation Example

 

 

Parameter	Symbol	Value	Converted Value	Descritpion
Transmit Power	P_t	10 dBm	0.1 W
TX Antenna Gain	G_t	8 dBi	6.31	Conversion to Linear Gain
RX Antenna Gain	G_r	8 dBi	6.31	Conversion to Linear Gain
Wavelength	λ	12.4 mm	0.0124 m
Target RCS	σ	0.5 m²		Estimated RCS of Stationary human
Range	R	8 m		Target Distance

 

 

Parameter	Symbol	Value	Converted Value	Description
Thermal Noise Density	k•T	-174 dBm/Hz
IF/Baseband Bandwidth	B	1 MHz	60 dB-Hz	Conversion to dB
Noise Figure	F	10 dB