Adaptive Multipath Equalizer for RF Receiver Signal Reconstruction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Radio frequency (RF) receivers face signal degradation due to multipath interference from reflected signals, particularly in systems like automobile radio receivers that experience changing positions relative to fixed antennas, leading to destructive interference and poor signal quality.
Innovation Solution
A multipath equalizer is implemented in the digital signal processor (DSP) of the radio receiver, using a digital filter with adaptive coefficients to remove out-of-phase interference by assuming a 2-ray propagation channel model and truncating the infinite impulse response (IIR) filter to eight terms, allowing for efficient signal processing in low-cost integrated circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the receiver constantly changes position relative to a fixed antenna, then the receiver can maintain line-of-sight connection, but signal quality deteriorates due to multipath interference and destructive interference from reflected signals
Solution Approach 1:
The patent converts the harmful reflected signals into beneficial components by using them in the equalization process. The multipath equalizer uses the known transmitted signal and the received signal to estimate channel impulse response, then reconstructs the transmitted signal by combining the direct path signal with compensated reflected signals. This transforms the previously harmful interference into useful information for signal recovery.
Solution Approach 2:
The patent dynamically adjusts equalizer coefficients based on changing channel conditions. The system continuously estimates the channel impulse response and updates the equalizer parameters to match the current multipath environment. This allows the receiver to adapt to varying positions and reflected signal conditions, maintaining signal quality despite changes in the electromagnetic environment.
2Reliability
If multipath equalization is implemented to improve signal quality, then signal-to-noise ratio improves, but device complexity increases due to additional signal processing requirements
Solution Approach 1:
The patent creates a digital model (copy) of the channel impulse response to represent the physical propagation path. By estimating the channel characteristics from the received signal and using this model for equalization, the system avoids the need for complex hardware modifications. The digital signal processor uses software-based filtering and signal reconstruction algorithms that are more flexible and less complex than hardware-based solutions.
3Reliability
If adaptive filtering is used to remove out-of-phase interference, then signal quality improves, but processing time and computational energy increase
Solution Approach 1:
The patent performs channel estimation and equalizer coefficient calculation in advance, using the known transmitted signal and received signal to pre-compute the channel impulse response. This preliminary processing allows the actual signal reconstruction to use simpler, pre-determined coefficients rather than requiring complex real-time adaptive calculations during signal playback, reducing the computational energy needed during critical signal recovery operations.
Data Source
AI summary
A radio receiver has a multipath equalizer that includes a filter and a coefficient estimator. The filter provides a reconstructed signal by applying a transfer function including a reflection coefficient and a delay coefficient to a multipath radio signal. The coefficient estimator adapts the reflection coefficient and the delay coefficient in response to a deviation in magnitude of the reconstructed signal from a normalized value. In one form, the coefficient estimator adapts at least one of the reflection coefficient and the delay coefficient by estimating a partial derivative using a predetermined number of terms. In another form, the coefficient estimator acquires an initial value of the delay coefficient by determining a global minimum as a lowest one of a plurality of local minimums, each determined using a plurality of values of the delay coefficient, and selecting the initial value of the delay coefficient as its value at the global minimum.