Bluetooth Receiver ADC Sampling for Low-Power AGC Timing
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Solution Overview
Problem
Bluetooth receivers consume excessive power by performing Automatic Gain Control (AGC) on every received packet, even if the packet is not intended for the station, as the destination cannot be determined until the Access Address (AA) field is read, leading to unnecessary power usage.
Innovation Solution
A power-saving multi-rate sampling front end that adjusts the ADC sample rate based on connection state, using a variable gain amplifier and a clock generator to set the ADC sample rate to a lower rate when connected, allowing the AGC process to complete during the preamble interval and continuing into the AA field, thereby reducing power consumption by sampling at a lower rate when connected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the ADC sample rate is reduced to save power when connected, then power consumption is reduced, but the AGC process cannot complete during the preamble interval
Solution Approach 1:
The patent applies dynamics by making the ADC sample rate variable rather than fixed. The clock generator dynamically adjusts the ADC sample rate based on connection state: using a first (higher) sample rate when not connected to ensure AGC completes during preamble, and a second (lower) sample rate when connected to reduce power consumption. This dynamic adaptation resolves the contradiction between power saving and AGC completion timing.
2Adaptability or versatility
If AGC is performed on every packet, then the receiver can handle packets of varying strength, but excessive power is consumed receiving packets not intended for the station
Solution Approach 1:
The patent segments the packet reception process into distinct phases with different operational modes. The connection state processor divides reception into connected state (where power-saving low sample rate is used) and not connected state (where full-performance high sample rate is used). This segmentation allows the receiver to maintain adaptability for handling packets of varying strength while reducing power consumption by only performing full AGC processing when necessary.
3Use of energy by moving object
If the ADC sample rate is lowered when connected, then power consumption decreases, but the AGC process must continue into the AA field
Solution Approach 1:
The patent maintains continuity of useful action by allowing the AGC process to continue seamlessly from the preamble interval into the AA field when operating at the lower sample rate during connected state. Rather than interrupting or restarting AGC, the system continuously adjusts gain throughout the packet reception, ensuring that power-saving mode does not compromise the completeness or accuracy of the AGC process.
Data Source
AI summary
A Bluetooth receiver has an RF front end which has a gain control input, the RF front end converting wireless packets into a baseband signal which is coupled to the input of an analog to digital converter (ADC). A clock generator provides a clock coupled to the ADC, and an AGC processor performs an AGC process to provide a gain which places the baseband symbols in a range that is less than 90% of the input dynamic range of the ADC. When in a connected state, the clock generator provides a clock which is slower than is required to complete the AGC process during a preamble interval, and the AGC process uses a few initial bits of the address field. The remaining bits of the address field is compared with the corresponding address bits of the receiver to determine whether to receive the packet.