Phased Array Carrier Frequency Offset Compensation
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Solution Overview
Problem
Conventional RF communication systems face challenges in compensating for carrier frequency offset, especially in ultrahigh bandwidth systems like millimeter wave or terahertz systems, where digital compensation is impractical due to frequency differences between local oscillators causing constellation rotation.
Innovation Solution
A phased array system with a beam steering circuit that calculates and applies offset cancellation to phase rotators, using a signal generator and phase controllers to adjust the phase rotators based on the carrier frequency offset, allowing for analog low-cost compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital compensation is used to correct carrier frequency offset, then constellation rotation is corrected, but the system becomes impractical for ultrahigh bandwidth systems due to complexity and cost
Solution Approach 1:
The patent replaces digital signal processing (electronic/computational system) with an analog phased array beamforming system. The beam steering circuit performs carrier frequency offset compensation through analog phase rotation of antenna elements, substituting complex digital compensation with a simpler analog beamforming approach that is practical for ultrahigh bandwidth systems.
Solution Approach 2:
The patent changes the operating parameters by using phase shifters to adjust the phase of signals at different antenna elements. By modifying the phase parameter of the transmitted signals, the system creates an effective phase rotation that compensates for carrier frequency offset without requiring complex digital processing.
2Reliability
If local oscillator frequencies are made identical, then carrier frequency offset is eliminated, but frequency matching becomes difficult to achieve
Solution Approach 1:
The patent applies preliminary counter-action by introducing phase rotations through the beam steering circuit that preemptively compensate for the expected carrier frequency offset. Instead of trying to prevent the frequency mismatch, the system proactively counteracts its effects through analog phase adjustment of the antenna array signals.
Solution Approach 2:
The phased array beamforming system acts as an intermediary between the local oscillators. Even when local oscillators have frequency mismatches, the beam steering circuit mediates by applying phase corrections to the transmitted signals, effectively bridging the frequency difference through analog processing.
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 solution effectively compensates for carrier frequency offset in ultrahigh bandwidth systems, maintaining beam direction and system functionality by adjusting phase rotators on a per symbol basis, making it practical for millimeter wave or terahertz frequency ranges.
Implementation Method 1
a plurality of phase rotators that are coupled between the signal generator and the phased array
Implementation Method 2
the beam steering circuit calculates an offset cancellation for the offset between the first carrier frequency and the second carrier frequency
Implementation Method 3
a phased array; a plurality of phase rotators that are coupled between the signal generator and the phased array
Data Source
AI summary
A method for communicating signals in an ultra high bandwidth system that compensates for carrier frequency offset is provided. A baseband transmit signal having a plurality of data bits is generated. The baseband transmit signal is upconverted to a radio frequency (RF) transmit signal using a first local oscillator signal having a first carrier frequency. An offset cancellation for the offset between the first carrier frequency and a second carrier frequency for a second local oscillator signal that is used to downconvert an RF receive signal is calculated. The offset cancellation is applied to a plurality of phase rotators, and the RF transmit signal is transmitted over a phased array.