PLL Frequency Scan While Keeping the Radio Active
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Solution Overview
Problem
Conventional frequency scan techniques in wireless localization systems are time-consuming and power-intensive due to multiple transitions between active and inactive modes during the tuning of phase locked loops (PLL) for each target frequency.
Innovation Solution
The method involves maintaining the wireless radio in an active mode throughout the frequency scan by coarsely tuning the PLL using pre-calibrated coarse frequency settings, interpolating values, or triggering a coarse frequency tuning engine, allowing the PLL to be placed in an open loop state, computing and programming fractional divider values, and then closing the loop after settling, thereby reducing the need for transitions between active and inactive modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional frequency scan techniques are used with multiple transitions between active and inactive modes, then the PLL can be tuned to each target frequency, but the frequency scan time increases and power consumption increases
Solution Approach 1:
The patent applies preliminary action by pre-calibrating coarse frequency tuning values for multiple target frequencies before the actual frequency scan operation. During the scan, the radio controller directly programs the PLL with pre-computed fractional divider values corresponding to each target frequency, eliminating the need for time-consuming frequency transitions and mode switches. This preliminary preparation of tuning parameters enables direct frequency switching while maintaining accurate locking at each target frequency.
Solution Approach 2:
The patent maintains the radio in a continuous active state throughout the frequency scan operation, avoiding transitions to inactive modes between frequency changes. The PLL remains continuously operational with its output signal actively generated and monitored throughout the entire scan process. This continuous operation eliminates idle time and mode transition overhead, allowing the useful action of frequency tuning and signal generation to proceed without interruption across all target frequencies.
2Measurement precision
If conventional frequency scan techniques are used with multiple transitions between active and inactive modes, then the PLL can be tuned to each target frequency, but power consumption increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing fractional divider values for all target frequencies before the scan operation. This eliminates the need for real-time frequency computations and iterative tuning procedures during the scan, reducing processing power requirements. The radio controller directly programs these pre-computed values into the PLL, minimizing energy-consuming operations while ensuring accurate frequency locking at each target frequency.
Solution Approach 2:
The patent keeps the radio continuously active during the frequency scan, avoiding repeated wake-up and sleep transitions that would consume significant power. By maintaining the PLL in a continuous locked state and the radio in an active mode throughout the scan, the system eliminates the overhead of mode transitions while reducing the total energy consumption associated with frequent power state changes and re-initialization sequences.
3Loss of time
If the PLL is coarsely tuned using pre-calibrated settings and placed in open loop state, then frequency scan time is reduced, but frequency tuning precision may be affected
Solution Approach 1:
The patent applies preliminary action by pre-calibrating coarse frequency tuning values and pre-computing exact fractional divider settings for all target frequencies before the scan operation. This preliminary preparation ensures that when the PLL is rapidly tuned using pre-programmed values, it directly locks to the precise target frequency without requiring iterative adjustments. The pre-computed fractional divider values compensate for the open-loop tuning approach, maintaining frequency locking accuracy while enabling rapid frequency transitions.
Solution Approach 2:
The patent implements feedback mechanisms to verify and maintain frequency locking accuracy during the rapid frequency scan. The phase-locked loop continuously monitors the locked state at each target frequency, and the radio controller can detect and correct any frequency deviations. This feedback ensures that even though the PLL is coarsely tuned using pre-calibrated settings in open-loop mode, the final frequency accuracy meets the required precision standards for wireless communication operations.
Data Source
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AI summary
A method of performing a frequency scan at a radio includes placing the radio in an active mode and, while maintaining the radio in the active mode, for each of a plurality of target frequencies determining a coarse frequency tuning value based on the target frequency. The radio places a phase locked loop (PLL) in an open-loop configuration and while the PLL is in the open-loop configuration, programs the VCO with the coarse frequency tuning value. The radio programs the divider with a feedback adjustment based on the target frequency, places the PLL in a closed-loop configuration, and in response to the PLL reaching a settled state, performs an operation based on an output signal of the PLL.