Frequency Modulator Calibration to Reduce Local Oscillator Coupling
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Solution Overview
Problem
In wireless communication systems, isolating the local oscillator signal from the output signal of a frequency modulator is challenging, leading to inefficient use of the allocated frequency spectrum and increased in-band noise due to unmodulated local oscillator signals being transmitted.
Innovation Solution
A calibration process is applied to the frequency modulator using offset signals to reduce the coupling of unmodulated local oscillator signals to the output, utilizing a grid space in computer memory to iteratively determine and compensate for characteristic bias voltages, thereby reducing the unmodulated signal to a threshold level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a local oscillator is used to convert baseband signals to transmission frequencies, then signal transmission capability is improved, but unmodulated local oscillator signals couple to the output and cause in-band noise and spectral inefficiency
Solution Approach 1:
The patent applies preliminary calibration action by determining characteristic bias voltages of the frequency modulator before normal operation. The calibration process pre-adjusts offset signals to compensate for the local oscillator coupling issue, preventing the harmful effect from occurring during actual signal transmission.
Solution Approach 2:
The patent changes the electrical parameter (bias voltage) of the frequency modulator to alter its coupling characteristics. By adjusting the characteristic bias voltages through calibration, the system modifies the modulator's operating point to minimize local oscillator signal coupling to the output.
2Productivity
If calibration is performed to reduce local oscillator coupling, then spectral efficiency is improved, but device complexity increases due to additional calibration circuitry and procedures
Solution Approach 1:
The frequency modulator performs self-calibration by determining its own characteristic bias voltages through the calibration process. The device uses internal resources and automatic calibration routines to adjust its own parameters, reducing the need for external calibration equipment and manual intervention.
Solution Approach 2:
The calibration process implements feedback by measuring the actual coupling characteristics of the frequency modulator and using this information to adjust the bias voltages. The system continuously monitors and refines the calibration parameters to optimize performance, creating a closed-loop control mechanism.
Data Source
AI summary
A processor can be configured to execute instructions stored in the memory to position a first point in a grid space that represents an unmodulated signal component of a first signal based on a characteristic of a frequency modulator generating the first signal. The frequency modulator can include a first input to receive data from a baseband source and can include a second input to receive a second signal from a local oscillator. The processor can determine, in the grid space, a first angle between a first line segment from a reference point to the first point and a second line segment from the first point to a point representing the first offset signal applied to the frequency modulator. The processor can additionally apply a second offset signal, based on the first angle, to compensate for the characteristic of the frequency modulator.