SAGE Millimeter offers Radar Target Simulator for Doppler Radar System Calibrations and Testing in the frequency range of 24 to 94 GHz. The simulator is based on Single Side Band (SSB) Modulation techniques. The simplified block diagram of the simulator is shown in the figure shown below.
It is well known that the relationship between the Doppler frequency and target speed is governed by the following equation.
FRF is the frequency of the transmitted frequency from DUT Radar in Hz
C is the speed of light (3 x 108 meter/sec.)
V is the target speed in travel in meters/sec.
ϴ is the angle between the moving target and the radar beam.
The two extremes are 1) no Doppler shift Fd = 0 when the moving target direction and radar beam are perpendicular (ϴ=90°) and 2) Fd = 2 V FRF / C when the moving target direction and radar beam are parallel or ϴ is very small (0 to 10°).
Some Doppler Shifts (Intermediate Frequency) in common microwave and millimeter wave bands are listed in the table below if the Radar is aiming the target directly, i.e., ϴ=0°.
|Target Speed (Km/Hr.)||100/500||100/500||100/500||100/500|
|Doppler Shift or IF(Hz)||4,472/22,361||6,574/32,870||14,166/141,666||17,407/87,037|
To operate the simulator, a function generator capable of delivering two orthogonal output signals (IF-I and IF-Q) in the frequency range of Doppler shift of the DUT due to the target speed and the 10 VP-P equal amplitude is required.
Once the function generator is located and set up for operation, follow the steps below to operate the Doppler Target Simulator.
- Connect the signal outputs of the function generator to the IF inputs of the simulator.
- Emit the radar signal from the DUT radar system towards the simulator antenna port (ANT). The returned Doppler shifted frequency Fo+IF or Fo-IF is received by the Radar and Radar display the speed of the target.
- Vary the frequency of the function generator to simulate the speed of the target.
- Vary the phase of the function generator (the phase difference of the IF-I and IF-Q signal, 90 of –90 degrees) to simulate the direction of the moving target, i.e., approaching and receding target.
To measure the relative sensitivity of the DUT Radar, a variable attenuator is added to the antenna port of the simulator. From the famous Radar Equation shown below, one can estimate the Radar detection range by reading the attenuation value from the attenuator.
Pr is returning power to the receiving antenna
Pt is the transmitting power
Gt is the gain of the Radar antenna
Rt is the distance from the Radar to the target
SAGE Millimeter offers two types for attenuator for Radar sensitivity: Level Setting and Direct Reading. The correspondent model numbers at 76.5 GHz, for instance, is STR-773-12-L1 and STR-773-12-D1, respectively. While level setting version is more geared up for production “go or no go” testing, the direct reading version is for R&D project setups, where the quantified Radar sensitivity information is the interest. For instance, a 6 dB attenuation reading increase on the direct reading attenuator indicates that the DUT Radar detection distance is increased by 100%.