Phase-Shift Leakage Cancellation for Accurate RF Range Detection
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Solution Overview
Problem
Electronic devices with wireless circuitry face challenges in accurately detecting the distance of external objects due to radio-frequency impairments like on-chip leakage, which complicates range detection operations.
Innovation Solution
Incorporating a phase shifter on the transmit path that toggles between two phase states, 180 degrees out-of-phase, and using mixer circuitry to subtract reflected signals to isolate the signal of interest, thereby mitigating the effects of on-chip leakage and other radio-frequency impairments without increasing physical separation between transmit and receive paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If on-chip leakage is present in the wireless circuitry, then the wireless communications can be performed, but the range detection accuracy deteriorates
Solution Approach 1:
The patent applies preliminary anti-action by introducing a cancellation signal that is 180 degrees out of phase with the leakage signal. This cancellation signal is generated in advance and subtracted from the received signal to preemptively counteract the harmful leakage effect before it degrades the range detection accuracy. The phase shifter pre-adjusts the cancellation signal to achieve destructive interference with the leakage component.
Solution Approach 2:
The patent converts the harmful leakage signal into a beneficial cancellation opportunity. By deliberately generating a signal that mirrors the leakage characteristics and then inverting its phase, the system transforms the problematic leakage into a useful reference for creating the cancellation signal. This approach turns the harmful RF impairment into the basis for its own countermeasure.
2Measurement precision
If physical separation between transmit and receive paths is increased to reduce on-chip leakage, then leakage effects are reduced, but device complexity and size increase
Solution Approach 1:
The patent introduces a phase shifter and signal cancellation circuit as intermediary components between the transmit and receive paths. These intermediaries process the received signal to extract and cancel the leakage component without requiring physical separation. The phase shifter acts as a mediator that adjusts the phase of the cancellation signal to match the leakage signal, enabling electronic rather than physical isolation.
Solution Approach 2:
The patent changes the phase parameter of the cancellation signal to achieve leakage suppression. By adjusting the phase shift to 180 degrees relative to the leakage signal, the system transforms the cancellation signal into an effective countermeasure. This parameter-based approach (phase modulation) replaces the need for spatial separation, maintaining a compact device layout while achieving high range detection accuracy.
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
This approach allows for accurate detection of range between the device and external objects by effectively removing the impact of on-chip leakage, enhancing signal quality and precision without altering the physical layout of the wireless circuitry.
Implementation Method 1
A real-time phase control circuit may toggle the phase shifter between a first state and a second state during transmission of the signal bursts. In the first state, the phase shifter receives a first phase vector element. The first phase vector element may control the phase shifter to apply a first phase shift to the signal bursts. In the second state, the phase shifter receives a second phase vector element. The second phase vector element may control the phase shifter to apply a second phase shift to the signal bursts.
Implementation Method 2
Mixer circuitry may downconvert the first reflected signals to first baseband signals. The mixer circuitry may downconvert the second reflected signals to second baseband signals.
Implementation Method 3
The second baseband signals may be subtracted from the first baseband signals to recover a signal of interest associated with reflection of the transmitted signal bursts off an external object. Toggling the phase shifter between the first and second states and performing this subtraction operation may serve to remove the effects of on-chip leakage and/or other radio-frequency impairments on the signal-of-interest
Implementation Method 4
The wireless circuitry may include a transmit path coupled to a transmit antenna. The sensing circuitry may include a receive path coupled to a receive antenna. During range detection operations, the signal generator may generate signal bursts.
Implementation Method 5
The receive path may be used to receive first reflected signals while the signal bursts are transmitted using the phase shifter in the first state. The receive path may also be used to receive second reflected signals while the signal bursts are transmitted using the phase shifter in the second state.
Data Source
AI summary
An electronic device may include wireless circuitry with a transmit antenna and a receive antenna. Signal bursts may be transmitted by the transmit antenna. A phase shifter may be toggled between a first state that applies a first phase shift and a second state that applies a second phase shift to the signal bursts. The second phase shift may be approximately 180 degrees out-of-phase with the first phase shift. A receive path may receive first reflected signals while the phase shifter is in the first state and second reflected signals while in the second state. The first and second reflected signals may be used to cancel the effects of on-chip leakage or DC offset to recover a signal-of-interest associated with reflection of the signal bursts off an external object. The signal-of-interest may be used to detect a range to the external object.