Long-Range Transceiver Duty Cycling for Harvested-Power IoT
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Solution Overview
Problem
Existing long range transceivers for IoT applications face challenges in operating efficiently on harvested energy due to high power consumption, particularly in receive and transmit modes, which limits their ability to maintain low average power consumption and extend communication range.
Innovation Solution
A low power long range transceiver design that includes an antenna, analog front-end circuit, demodulator, and controller to manage power consumption by amplifying, shifting frequency, filtering RF signals, and employing bit-level duty cycling to reduce power usage, allowing operation below 1 mW in receive mode and a few mW in transmit mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If long range transceiver operates in receive or transmit mode, then communication range is extended, but power consumption increases to 48 mW
Solution Approach 1:
The transceiver employs duty cycling where the radio operates in periodic intervals rather than continuously. The system wakes up at scheduled intervals to transmit or receive data, then returns to sleep mode. This periodic operation allows the device to achieve kilometer-range communication over time while maintaining average power consumption at 50 μW, as the high-power transmit/receive operations occur only during brief active windows.
Solution Approach 2:
The system dynamically adjusts its operational state between sleep, active transmit, and active receive modes. The controller dynamically manages the power state of various components including the low noise amplifier, mixer circuit, and demodulator based on communication requirements, enabling the transceiver to adapt power consumption to actual communication needs rather than operating at fixed high power levels.
2Use of energy by moving object
If duty cycling is used to reduce average power to 50 μW, then power consumption decreases, but average data rate drops to 1.04 bps
Solution Approach 1:
The system performs preliminary actions by pre-scheduling communication intervals and pre-charging storage capacitance before actual data transmission. The controller plans communication windows in advance, allowing the system to accumulate sufficient energy in storage capacitance before high-power transmit operations. This preliminary energy accumulation enables higher data rates during active periods while maintaining low average power consumption.
Solution Approach 2:
The transceiver maintains continuous useful action through overlapping communication intervals and efficient packet transmission. By optimizing the duty cycle timing and ensuring continuous data readiness during active periods, the system maximizes data throughput during each wake window. The continuous monitoring and intelligent scheduling ensure that communication opportunities are not lost, maintaining higher effective data rates than simple periodic duty cycling would suggest.
3Productivity
If transceiver transmits 100-bit packet at 1 kbps, then data transmission is completed, but storage capacitance requirement increases to 1.6 mF
Solution Approach 1:
The transceiver segments the data transmission into smaller packets and distributes transmission across multiple duty cycle intervals. Rather than transmitting all 100 bits in a single continuous high-power operation that would require 1.6 mF of storage capacitance, the system breaks down the transmission into manageable chunks, each requiring less energy accumulation. This segmentation reduces the peak power duration and corresponding storage capacitance requirements for each transmission event.
Solution Approach 2:
The system changes operational parameters including data rate, packet size, and transmission timing to optimize power-capacitance trade-offs. By adjusting these parameters dynamically based on available energy and communication requirements, the transceiver can transmit data packets with reduced storage capacitance requirements compared to fixed high-power transmission modes.
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 design achieves an average power consumption of 50 μW, enabling kilometer-range communication while reducing the required storage capacitance, thereby enhancing the efficiency and effectiveness of energy harvesting for IoT sensor nodes.
Implementation Method 1
The low noise amplifier is configured to receive the RF signal from the antenna and amplify the RF signal
Implementation Method 2
The mixer circuit is configured to receive the amplified RF signal from the low noise amplifier and operates to shift the amplified RF signal to an intermediate signal having a different frequency
Implementation Method 3
an antenna configured to receive an RF signal
Data Source
AI summary
A low power long range transceiver is presented. The transceiver includes: an antenna configured to receive an RF signal; an analog front-end circuit configured to receive the RF signal from the antenna and pre-condition the RF signal by at least one of amplify the RF signal, shift frequency of the RF signal and filter the RF signal; and a demodulator configured to receive the preconditioned signal from the front-end circuit and an assertion trigger signal signifying an end of a predefined time period, where the demodulator, in response to the assertion trigger signal, outputs a data value for a given data bit in the RF signal. A controller is also configured to receive the assertion trigger signal and, in response to the assertion trigger signal, disables at least one component of the transceiver, thereby reducing power consumption.