VSWR-Based Ultra-Short-Range Detection for Radar Blind Spots
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electronic devices with wireless capabilities face challenges in accurately estimating distances to external objects due to a blind spot near the device where wireless circuitry fails to detect their presence, potentially exceeding regulatory limits on specific absorption rate (SAR) and maximum permissible exposure (MPE).
Innovation Solution
Incorporating ultra-short range (USR) detector circuitry with a voltage standing wave ratio (VSWR) sensor, including a directional coupler and phase/amplitude detector, to detect objects within a threshold distance using VSWR measurements, and processors to analyze these measurements for object presence, ensuring compliance with SAR and MPE regulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long range spatial ranging circuitry is used to estimate distance to external objects, then the ability to detect objects at a distance is improved, but a blind spot is created near the device where objects cannot be detected
Solution Approach 1:
The detection system is segmented into two distinct components: long range spatial ranging circuitry for detecting objects beyond a threshold distance, and ultra-short range (USR) detector circuitry for detecting objects within the threshold distance. This segmentation resolves the blind spot problem by dividing the detection space into two zones, each handled by specialized circuitry optimized for its range.
2Measurement precision
If transmit power is increased to improve detection range, then the ability to detect distant objects is improved, but regulatory limits on SAR and MPE may be exceeded
Solution Approach 1:
The transmit power level is made dynamic rather than fixed. The system continuously monitors VSWR measurements and adjusts the transmit power accordingly: using higher power when no objects are detected (improving detection range), and reducing power when objects are detected within the threshold distance (preventing SAR/MPE violations). This dynamic adjustment resolves the contradiction between detection range and safety limits.
Solution Approach 2:
A feedback mechanism is implemented where VSWR measurements from the USR detector are fed back to control the transmit power level of the long range spatial ranging circuitry. The system uses real-time detection data to adjust transmission parameters, ensuring both effective detection and compliance with regulatory exposure limits.
3Reliability
If VSWR measurements are used to detect nearby objects, then the blind spot coverage is improved, but measurement robustness is reduced by background interference
Solution Approach 1:
The system performs preliminary background VSWR measurements when no objects are present to establish a baseline. These background measurements are then subtracted from real-time VSWR measurements to cancel out background interference and isolate the signal caused by nearby objects. This preliminary action resolves the measurement robustness issue by pre-characterizing and removing background effects.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The USR detector effectively covers the blind spot of long-range spatial ranging circuitry, accurately detecting nearby objects and adjusting transmit power levels to maintain regulatory compliance, enhancing object detection accuracy and safety.
Implementation Method 1
The USR detector circuitry may include a voltage standing wave ratio (VSWR) sensor. The VSWR sensor may gather VSWR measurements such as complex scattering parameter values (e.g., S11 values) in response to radio-frequency signals on the transmit path.
Implementation Method 2
The VSWR sensor may gather VSWR measurements using radar signals transmitted by the long range spatial ranging circuitry, radio-frequency signals transmitted by the wireless communications circuitry, and/or test signals generated by a dedicated signal generator.
Data Source
AI summary
An electronic device may include a processor and wireless circuitry with transmit and receive antennas. Radar circuitry may use the transmit and receive antennas to perform spatial ranging on external objects farther than a threshold distance (e.g., 1-2 cm) from the transmit antenna. The wireless circuitry may include a voltage standing wave ration (VSWR) sensor coupled to the transmit antenna to detect the presence of objects within the threshold distance from the transmit antenna. This may serve to cover a blind spot for the radar circuitry near to the transmit antenna. The VSWR sensor may gather background VSWR measurements when other wireless performance metric data for the wireless circuitry is within a predetermined range of satisfactory values. The background VSWR measurements may be subtracted from real time VSWR measurements to perform accurate and robust ultra-short range object detection near to the transmit antenna.