TIDUF89 September   2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Detection Theory
    2. 1.2 Multi-Pass Architecture
  8. 2System Overview
    1. 2.1 System Design Theory
      1. 2.1.1 Long Detection Range
        1. 2.1.1.1 Antenna Design for Long Detection Range
        2. 2.1.1.2 SNR Compensation for Long Detection Range
        3. 2.1.1.3 Smart Detection Logic
      2. 2.1.2 Low Power Consumption
        1. 2.1.2.1 Efficient Chirp Design
        2. 2.1.2.2 Deep Sleep Power Modes
        3. 2.1.2.3 Hardware Accelerator
      3. 2.1.3 Low False Alarm Rate
        1. 2.1.3.1 Typical Causes of False Alarms
        2. 2.1.3.2 False Alarms Outside the Detection Zone
        3. 2.1.3.3 False Alarms Within the Detection Zone
        4. 2.1.3.4 Adaptive State Machine
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Software Requirements
    3. 3.3 Test Setup
      1. 3.3.1 Test 1 - Detection Range
      2. 3.3.2 Test 2 - False Alarm Rate
      3. 3.3.3 Test 3 - Power Consumption
    4. 3.4 Test Results
  10. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
  11. 5Tools and Software
  12. 6Document Support
  13. 7Support Resources
  14. 8Trademarks
  15. 9About the Authors

1.2 Multi-Pass Architecture

While a good detection system has all three of these qualities (low power, long range, low false alarm rate), the recommendation is to prioritize some over others in specific scenarios to extract the best overall system performance. The IWRL6432AOP navigates this balance by using multiple detection modes. This design guide assumes that three modes are used, but the logic can apply for two modes, or even more than three modes if necessary.

First pass mode is the default option for the radar. In first pass mode, the IWRL6432AOP operates in the lowest possible power configuration while still maintaining the ability to detect at long ranges. IWRL6432AOP does have some false alarms, even in low-noise conditions to achieve long range at the lowest possible power. For best results, the first pass mode need to be as low-power as possible, even at the expense of some false alarms.

When detections occur in first pass mode, the radar switches to second pass mode, which uses a higher-power chirp that reduces the false alarm rate of the radar, and achieves the same detection range as the first pass mode. There is no advantage for the second pass mode to detect objects at further ranges than the first pass mode, since the first pass mode is what triggers the second pass mode. The second pass mode do not have nearly as many false alarms as the first pass mode, but is acceptable to still wake up sometimes from winds, bushes and trees.

Finally, a third pass mode can be used to eliminate any false positives still detected in second pass mode. The third pass mode cannot have any false alarms if possible, since the third pass mode can be used to awaken the camera, which can draw 10-100 times more power than the radar.


TIDEP-01035 Multi-Pass Architecture State Machine

Figure 1-2 Multi-Pass Architecture State Machine

By cycling between the three power modes, the IWRL6432AOP is able to take advantage of the lowest-power consumption of the first pass mode when there is very little ambient motion, while also benefiting from the minimal false alarm rate of the third pass mode. The second pass mode serves to make sure that in times of high ambient movement in the scene, when first pass mode can be too sensitive to be effective, the radar still has a reasonably low power mode.

Table 1-1 Power, Range and False Alarm Rate for Each Mode
First Pass ModeSecond Pass ModeThird Pass Mode
Power ConsumptionLowMediumHigh
False Alarm RateHigh, even in low-movement scenariosModerate, only when there is wind, trees, or bushesLow
Detection RangeEqualEqualEqual
Percent of Time Spent in Mode HighMediumSmall