Doppler Radar Target Simulators


SAGE Millimeter offers Doppler Radar Target Simulators for Radar manufacturers and developers to test and evaluate their Radar systems’ performance in an economic way by replacing expensive and time-consuming field tests. The standard models are offered to cover common radar frequency bands of 24.125 GHz, 35 GHz, 77 GHz, 79 GHz and 94 GHz with an operating bandwidth from ±100 to ±250 MHz, respectively. The actual operating bandwidth can be extended to ±500 MHz and up to ±1,000 MHz for 77 GHz, 79 GHz and 94 GHz models. While the level setting series is a lower cost version, the direct reading series can give exact sensitivity information by reading the dB difference from the attenuator directly after calibration. Figure 1 and Figure 2 shows the level setting and the direct reading 77 GHz Radar simulators, respectively. Various antennas, such as SAGE’s SAR series can be selected from SAGE Millimeter’s standard antenna offerings and added to the antenna port. These Radar Target Simulators are designed and fabricated for Doppler Radar Target Simulation, which will simulate the Radar Target Size, the Speed of the Radar Target and Moving Direction of the Radar Target.

Figure 1 SAGE Millimeter Level Setting Series
Figure 1. Level Setting Series
Figure 2 SAGE Millimeter Direct Reading Series
Figure 2. Direct Reading Series

The core technology implemented in the Doppler radar simulators are single sideband modulator-based with the following working mechanism. The radar signal emitted by the Radar (Device) Under-Testing (DUT) is received through the antenna port and fed into the single sideband modulator through a diplexer. The single sideband modulator modulates the incoming signal and sends either upper or low band signal back to the diplexer. The frequency shifted signal is transmitted back to the antenna as Doppler signal for the DUT to receive. The amount of frequency shifting equals the input modulation frequency, i.e., the intermediate frequency (IF). By adjusting the intermediate frequency (IF), the phase of the IF’s “I” and “Q” channels and the routing attenuation, the speed, direction and radar cross-section of the Radar target can be simulated. The amplitude of the input modulation frequency is ±10 Vp-p.

The simplified block diagram of the simulator with the signal flowing is shown in the Figure 3.

Figure 3 SAGE Millimeter Block Diagram
Figure 3. The Simplified Block Diagram with the Signal Flow of the Radar Simulator

The following steps show the detailed operating procedure:

  1. Use a function generator which can deliver two orthogonal sine wave signals (IF-I and IF-Q) in the frequency range of the TBD target speed and ±10 Vp-p amplitude level. For example, if the interested target speed is at 80 kilometers per hour and your radar under testing is at 24.125 GHz (Fo), the IF-I and IF-Q frequency is 3,575 Hz.
  2. Connect the output of the function generator to the IF inputs of the simulator.
  3. Select a proper antenna, such as, SAR series, from SAGE Millimeter’s standard offerings and install it onto the antenna port.
  4. 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 the Radar will display the speed of the target.
  5. Vary the frequency of the function generator to simulate the speed of the target.
  6. Vary the phase of the function generator (the phase difference of the IF-I and IF-Q signal, 90 or –90 degrees) to simulate the direction of the moving target, i.e., approaching and receding target.

Vary the path attenuation by adjusting the attenuator value to simulate the target radar cross section or the distance. While the level setting attenuator can only give relative ranging (distance) information, the direct reading attenuator can give the exact ranging information directly after system calibration by using the Radar Equation.

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