Precoder Transformation for Equal Transmit Power in Coupled Antennas
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Solution Overview
Problem
Existing wireless communication systems assume that precoders with equal L2 norm result in antenna patterns with equal transmit power, which is incorrect when antennas are coupled and transmission lines are used, leading to variations in transmit power due to mutual coupling and phase dependencies.
Innovation Solution
Transforming precoders to ensure equal transmit power by scaling or multiplying them with a transformation matrix, based on transmission line impedance and antenna array impedance, to map all precoders to antenna patterns with equal power, using quadratic forms to express transmit power variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If precoders with equal L2 norm are used in coupled antenna systems with transmission lines, then the system complexity remains simple and computation is easy, but the transmit power varies due to mutual coupling and phase dependencies
Solution Approach 1:
The patent transforms precoders by applying a transformation matrix that modifies the amplitude and phase parameters of each precoder vector. This transformation is based on the quadratic form expressing transmit power variations due to mutual coupling, ensuring that all transformed precoders produce equal transmit power despite the original precoders having equal L2 norms. The transformation matrix incorporates coupling coefficients and phase information to compensate for power variations.
2Power
If precoders are transformed to ensure equal transmit power, then transmit power equality is achieved, but the computation complexity increases due to transformation matrix application
Solution Approach 1:
The patent pre-computes the transformation matrix based on the antenna coupling characteristics and transmission line parameters before actual precoding operations. The transformation matrix is derived from the quadratic form that models transmit power variations, and this pre-computed matrix is then applied to all precoders in the codebook. This preliminary action avoids repeated complex calculations during channel estimation and data transmission phases.
3Ease of operation
If the assumption of equal transmit power for equal L2 norm precoders is maintained, then system operation is simplified, but channel estimation accuracy deteriorates due to actual power variations
Solution Approach 1:
The patent replaces the incorrect assumption-based operation with a physics-based transformation approach. Instead of relying on the simplified assumption that equal L2 norm precoders produce equal power, the system applies a transformation matrix derived from the actual electromagnetic coupling physics (represented by the quadratic form). This substitution ensures that channel estimation and data transmission use precoders with truly equal transmit power, improving accuracy while maintaining reasonable operational complexity.
Data Source
AI summary
A precoded signal including reference symbols can be received. Channels for the reference symbols can be estimated. A channel for the data symbols can be estimated by taking an inner product of a conjugate of a data symbol precoder and the reference symbol channel estimates. Received data symbols can be demodulated based on the estimated channel.