RF Transmission Phase Calibration Using Higher-Order DFT Bins
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Solution Overview
Problem
In multi-channel RF circuits, particularly in radar systems, accurately measuring the phase and amplitude of RF output signals is challenging due to temperature-dependent variations and production tolerances, which affect the phase lag and gain of each channel, especially when both channels are active, making it difficult to achieve balanced phases and amplitudes for beam forming applications.
Innovation Solution
A method and circuit that include a transmission channel, a test phase shifter, a phase mixer, an analog-to-digital converter, and a monitor circuit to generate compensated phase information by applying phase offsets and using discrete Fourier transform (DFT) on the mixer output signal to accurately measure and calibrate the phase and amplitude of RF output signals across multiple channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase measurement methods are used in multi-channel RF circuits, then the measurement process is simple, but the measurement precision deteriorates due to temperature-dependent variations and production tolerances affecting phase lag and gain
Solution Approach 1:
The patent applies periodic action by using a sequence of phase offsets that are applied periodically to the reference signal. The test phase shifter introduces different phase offsets in a periodic manner, allowing the measurement system to capture multiple samples that can be processed using DFT to extract accurate phase and amplitude information while compensating for temperature-dependent variations.
Solution Approach 2:
The patent implements feedback by using the measured phase and amplitude information to generate compensated phase values. The monitor circuit continuously measures the actual phase and amplitude of the RF output signals, compares them with desired values, and uses this feedback to determine compensation values that are applied to correct the phase errors in the transmission channels.
2Adaptability or versatility
If both transmission channels are active simultaneously, then the system operates in realistic beam forming conditions, but it becomes difficult to measure and balance the phase and amplitude of individual channels
Solution Approach 1:
The patent applies segmentation by separating the measurement of each transmission channel's phase and amplitude characteristics even when both channels are active. The monitor circuit processes the combined output signals by using the known phase offsets and DFT processing to extract individual channel parameters, effectively segmenting the measurement task to achieve accurate measurements in realistic operating conditions.
3Manufacturing precision
If phase calibration is performed to achieve balanced phases across channels, then beam forming accuracy improves, but the device complexity increases due to additional measurement and compensation circuits
Solution Approach 1:
The patent applies universality by designing the monitor circuit to perform multiple functions: it measures both phase and amplitude of the RF output signals, processes signals from multiple transmission channels, and generates compensation values that can be applied to different channels. This multi-functional approach achieves accurate beam forming calibration without requiring separate dedicated circuits for each measurement and compensation task.
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 enables precise measurement and calibration of phase and amplitude across multiple RF channels, ensuring balanced output signals even when both channels are active, improving the accuracy of beam forming techniques and radar system performance.
Implementation Method 1
a phase mixer configured to mix the phase-shifted signal and the transmit monitoring signal to generate a mixer output signal including a plurality of direct current (DC) values
Implementation Method 2
an analog-to-digital converter (ADC) configured to sample the mixer output signal in order to provide a sequence of DC sample values
Implementation Method 3
a monitor circuit configured to apply a discrete Fourier transform (DFT) to the sequence of DC sample values to generate a plurality of DFT bins with corresponding DFT bin values
Data Source
AI summary
A circuit includes a transmission channel that outputs a continuous-wave signal based on a reference signal, a transmit monitoring signal path that couples out a portion of the transmit signal as a monitoring signal, a test phase shifter that receives the reference signal and generates a phase-shifted signal based on a sequence of phase offsets applied to the reference signal, a phase mixer that mixes the phase-shifted signal and the monitoring signal to generate a mixer output signal including a plurality of direct current (DC) values, an analog-to-digital converter that samples the mixer output signal in order to provide a sequence of DC values; and a monitor circuit that applies a discrete Fourier transform (DFT) to the sequence of DC values to generate a plurality of DFT bins with corresponding DFT bin values, and generate compensated phase information of the transmission channel using at least two DFT bin values.