VHF Datalink APSK Modulation With PA Linearity Control
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Solution Overview
Problem
Current VHF Datalink Mode 2 (VDLM2) communication systems do not provide sufficient data rate to support new air traffic management applications such as 4D trajectories and uplinked weather data, which require higher bit rates than existing infrastructure can handle.
Innovation Solution
A VHF communications transceiver using amplitude and phase shift keying (APSK) modulation with a power amplifier and linearity controller to achieve higher data rates across VHF channels, with a bandwidth of at least 8.33 kHz and a data rate per Hertz of greater than or equal to 3 bits per second per Hertz, and employing TDMA with a global navigation satellite system (GNSS) time signal for precise timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If VDLM2 technology is used with D8PSK modulation, then communication compatibility is maintained, but data rate is insufficient for new ATM applications
Solution Approach 1:
The patent changes the modulation parameter from D8PSK to APSK (Amplitude and Phase Shift Keying), which provides higher spectral efficiency and enables data rates of at least 3 bps/Hz. This parameter change allows the system to support new ATM applications requiring higher bandwidth while maintaining VHF channel compatibility.
2Use of energy by moving object
If power amplifier is operated at high efficiency, then energy consumption is reduced, but nonlinear distortion increases affecting signal quality
Solution Approach 1:
The patent applies pre-distortion technique where the modulated signal is pre-distorted before being amplified by the power amplifier. This preliminary action compensates for the nonlinear distortion that will occur during amplification, allowing the power amplifier to operate at high efficiency while maintaining signal quality and low bit error rates.
3Productivity
If multiple VHF channels are used with bandwidth of 8.33 kHz, then spectral efficiency is improved, but timing synchronization becomes more critical
Solution Approach 1:
The patent employs TDMA (Time Division Multiple Access) with feedback mechanisms where ground stations provide timing signals to aircraft based on GNSS time. This feedback loop enables precise timing synchronization across multiple VHF channels, allowing the system to achieve high spectral efficiency with 8.33 kHz bandwidth while maintaining accurate time slot allocation and signal reception.
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
Enables aeronautical data links with significantly higher data rates than VDLM2, supporting applications like 4D trajectories and uplinked weather, while maintaining low bit error rates and operational efficiency across a range of VHF channels.
Implementation Method 1
an amplitude and phase shift keying (APSK) modulator configured to modulate signals for transmission
Implementation Method 2
a power amplifier configured to amplify the modulated signals prior to the transmission
Implementation Method 3
control linearity of the power amplifier according to at least one of a Cartesian feedback amplifier linearization, pre-distortion amplifier linearization or feedforward amplifier linearization
Implementation Method 4
control linearity of the power amplifier according to at least one of a Cartesian feedback amplifier linearization, pre-distortion amplifier linearization or feedforward amplifier linearization
Implementation Method 5
The timing signal is obtained based on a global navigation satellite system (GLASS) time signal and/or a clock device having a time precision with 100 microseconds
Data Source
AI summary
A very high frequency (VHF) transceiver can include an amplitude and phase shift keying (APSK) modulator configured to modulate signals for transmission across a first VHF channel of a plurality of VHF channels used to communicate between or among aircraft and one or more ground stations. Each of the VHF channels can have a bandwidth of at least 8.33 kilo Hertz (kHz) with a data rate per Hertz (Hz) greater than or equal to 3 bits per second per Hz (bps/Hz). The VHF transceiver can include a power amplifier configured to amplify the modulated signals prior to the transmission. The VHF transceiver can include a linearity controller configured to control linearity of the power amplifier according to at least one of a Cartesian feedback amplifier linearization, pre-distortion amplifier linearization or feedforward amplifier linearization to mitigate nonlinear distortion associated with signals output by the power amplifier.