Wireless Transmitter Spectrum Equalization via Loopback
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Solution Overview
Problem
Wireless communication transmitters often have uneven characteristic frequency responses due to analog devices like power amplifiers, leading to non-compliant output spectrum flatness and memory effect distortions, especially affecting low-power signals in WLAN standards.
Innovation Solution
A method involving the use of single-frequency signals with different predetermined frequencies, loopbacked through an analog-to-digital converter to calculate the transmitter's frequency response, and designing a pre-equalizer with specific equalizing sequences to correct the transmission spectrum, including steps like mixing, low-pass filtering, and inverse Fourier transform to achieve a flat impulse response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If analog devices like power amplifiers are used in the transmitter, then the transmitter can be manufactured with conventional components, but the frequency response becomes uneven and causes spectrum flatness non-compliance and signal distortions
Solution Approach 1:
The patent applies preliminary equalization by calculating the frequency response of the power amplifier and designing equalizer coefficients before actual transmission. The equalizer pre-compensates for the uneven frequency response characteristics of the analog device, ensuring that the overall system achieves flat spectrum compliance before signals are transmitted.
Solution Approach 2:
The patent changes the parameters of the equalizer by calculating different equalizer coefficients based on the measured frequency response of the power amplifier. The equalizer parameters are adjusted to compensate for the specific uneven frequency response characteristics, transforming the system from non-compliant to compliant with spectrum flatness requirements.
2Device complexity
If conventional transmitters with power amplifiers are used, then the device complexity is reduced, but memory effect distortions occur especially affecting low-power signals
Solution Approach 1:
The patent performs preliminary equalization by calculating the frequency response and designing equalizer coefficients before transmission. This pre-processing step compensates for memory effect distortions that would otherwise affect low-power signals, improving reliability without adding complex hardware structures.
Solution Approach 2:
The patent introduces an equalizer as an intermediary component between the signal source and the power amplifier. The equalizer processes the signal to pre-compensate for the nonlinear effects and memory effects of the power amplifier, thereby improving signal accuracy without requiring changes to the power amplifier itself.
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
The method effectively equalizes the transmission spectrum of wireless communication transmitters, ensuring compliance with WLAN standards by compensating for uneven frequency responses, thereby reducing signal distortions and improving transmission quality.
Implementation Method 1
mixing the output of the transmitter in response to the inputted single-frequency signals with a signal from the local oscillator
Implementation Method 2
low-pass filtering the above mixing result
Implementation Method 3
performing an analog-to-digital conversion for the obtained baseband part of frequency response
Implementation Method 4
applying inverse Fourier transform to the equalizing sequence H[k]
Data Source
AI summary
This disclosure provides a method for equalizing the transmission spectrum of a wireless communication transmitter. The method includes: providing a plurality of single-frequency signals; respectively inputting the plurality of single-frequency signals into the transmitter, wherein each single-frequency signal has a predetermined frequency and all the predetermined frequencies are different from each other; loopbacking the plurality of single-frequency signals to an analog to digital converter so as to generate a plurality of digital loopback signals; calculating a frequency response of the transmitter at base band circuit according to the plurality of digital loopback signals; and equalizing the transmission spectrum of the transmitter according to the frequency response of the transmitter.