Wake-Up Radio RSSI Circuit With Direct RF-to-Digital Detection
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Solution Overview
Problem
Existing RSSI circuits in IoT devices face challenges with high power consumption, limited dynamic range, and detection accuracy, making them unsuitable for battery-operated devices and applications requiring precise signal strength detection.
Innovation Solution
A 65-nm CMOS-based RSSI circuit that directly converts RF signal strength to a digital code using a multi-stage passive rectifier, ultra-low power comparator, and feedback loop to achieve high accuracy and low power consumption, enabling direct digitization of signal strength and resilience to noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional RSSI circuits are used in IoT devices, then signal strength detection is achieved, but power consumption is high
Solution Approach 1:
The patent replaces conventional active rectifier circuits with a passive rectifier implementation. The passive rectifier uses passive components (diodes, capacitors, resistors) instead of active transistors, eliminating the need for bias current and significantly reducing power consumption while maintaining signal strength detection capability
Solution Approach 2:
The patent employs periodic sampling of the rectified signal at specific phases (e.g., peak detection) rather than continuous measurement. This periodic action reduces the operational duty cycle of the comparator and counter circuits, thereby reducing average power consumption while maintaining detection accuracy
2Measurement precision
If conventional RSSI circuits are used, then detection is achieved, but dynamic range is limited
Solution Approach 1:
The patent divides the signal strength detection into multiple discrete levels using a multi-threshold comparator system or multi-stage rectifier with different detection thresholds. Each stage detects a specific signal strength range, and the results are combined to provide accurate measurement across a wide dynamic range from very weak to strong signals
Solution Approach 2:
The patent implements variable detection parameters including adjustable threshold voltages, programmable sampling rates, and configurable integration times. These parameter changes allow the circuit to adapt to different signal conditions and extend the effective dynamic range by optimizing detection sensitivity for different signal strength levels
3Reliability
If conventional RSSI circuits are used, then signal detection is achieved, but detection accuracy is insufficient
Solution Approach 1:
The patent incorporates feedback mechanisms where the detected signal strength information is fed back to adjust the detection thresholds and sampling parameters in real-time. This feedback loop compensates for drift and non-linearities, improving detection accuracy without requiring complex calibration circuits
Solution Approach 2:
The patent introduces intermediate processing stages including signal filtering, noise suppression circuits, and interpolation algorithms between discrete detection levels. These intermediaries smooth the detection output and reduce quantization errors, improving overall accuracy while adding minimal circuit complexity
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 proposed RSSI circuit achieves a dynamic range of 26 dB with ±0.5 dB accuracy and 15 nW power consumption, enhancing the reliability of wireless communication and enabling applications like localization and wireless beamforming.
Implementation Method 1
rectifying the RF signal in a multi-stage passive rectifier to generate an output voltage
Implementation Method 2
comparing the output voltage to a threshold voltage in a comparator and generating a toggle signal when the output voltage exceeds the threshold voltage
Implementation Method 3
feeding the toggle signal to the multi-stage passive rectifier to discharge a capacitor for each stage of the multi-stage passive rectifier to enable another charging cycle
Data Source
AI summary
A radio frequency (RF) signal strength detection technique is disclosed with a received signal strength indicator (RSSI) circuit, which can be deployed in an internet-of-things (IoT) network. The RSSI circuit is based on a direct conversion of RF to digital code indicating the signal strength. The direct conversion is achieved by the repeated switching of a rectifier's output voltage using an ultra-low power comparator. A 5-bit programmable feedback circuit can be used to correct detection inaccuracies. The RSSI circuit can be implemented in a 65-nm CMOS process and consumes 15 nW power. It can have a linear dynamic range of 26 dB and exhibit an error of ±0.5 dB with a wide bandwidth of 500 MHz. The technique has been verified with simulation and measurement results. The high detection accuracy with ultra-low power consumption of the proposed RSSI circuit is favorable for IoT applications including, e.g., biomedical, localization, and other low-power applications.