Wireless Transmitter Frequency Planning for In-Band IM3 Control
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Solution Overview
Problem
Existing wireless communication devices face challenges in meeting stringent spectral emission limits due to non-linearity in transmitters, leading to spurious emissions outside the assigned channel bandwidth, which can be costly to mitigate with increased linearity.
Innovation Solution
The solution involves positioning the third-order intermodulation product within the assigned channel bandwidth by adjusting the local oscillator frequency and modulation frequency, allowing for compliance with out-of-band spurious emission limits without requiring a highly linear transmitter, thus enabling a lower-cost or simplified communication device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the transmitter is made more linear to reduce spurious emissions, then spectral emission limits are met, but device complexity and cost increase
Solution Approach 1:
The patent converts the harmful third-order intermodulation product, which normally appears as spurious emissions outside the channel bandwidth, into a beneficial in-band signal by carefully selecting the local oscillator frequency. The intermodulation product at frequency w_LO - 3w_IQ is positioned within the assigned channel bandwidth where it can be filtered along with other out-of-band emissions, thereby meeting spectral emission limits without requiring a highly linear transmitter.
2Object-affected harmful factors
If the local oscillator frequency is adjusted to position the third-order intermodulation product within the channel bandwidth, then compliance with emission limits is achieved, but frequency planning complexity increases
Solution Approach 1:
The patent changes the frequency parameter of the local oscillator from a conventional choice to a specifically calculated value that satisfies the condition w_LO - 3w_IQ falls within the assigned channel bandwidth. This parameter change transforms the intermodulation product from a harmful out-of-band emission to an in-band signal that can be managed through standard filtering, simplifying overall emission compliance.
3Object-affected harmful factors
If a highly linear transmitter is used to meet spectral limits, then emission compliance is achieved, but power consumption increases
Solution Approach 1:
The patent converts the harmful effect of transmitter non-linearity, which generates power-consuming intermodulation products, into a beneficial outcome by positioning the third-order intermodulation product within the channel bandwidth. This allows the use of less linear, more power-efficient transmitters while still meeting spectral emission limits through strategic frequency planning and standard filtering.
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 easier compliance with spectral emission limits, reducing the need for costly linearization and minimizing power consumption by maintaining the third-order intermodulation product within the assigned channel bandwidth, even with variable transmission bandwidths.
Implementation Method 1
converting in-phase and quadrature-phase components of a modulation signal at a modulation frequency to a radio frequency by mixing the in-phase and quadrature-phase components with the local oscillator signal
Data Source
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AI summary
A wireless communication device (400) is arranged to transmit a transmission signal in an assigned channel bandwidth. The wireless communication device (400) comprises: a local oscillator (460) arranged to generate a local oscillator signal at a local oscillator frequency and a modulator (434) arranged for converting in-phase and quadrature-phase components of a modulation signal at a modulation frequency to a radio frequency by mixing the in-phase and quadrature-phase components with the local oscillator signal. The local oscillator frequency is arranged to place a third order intermodulation product having a frequency equal to the local oscillator frequency minus three times the modulation frequency within the assigned channel bandwidth.