Integrated VCO Frequency Calibration Without a Separate Calibration Oscillator
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Solution Overview
Problem
Current automotive radar systems are bulky due to discrete component assembly and suffer from noise susceptibility in tuning voltage transmission, as well as increased cost and space usage from requiring a separate calibration VCO for frequency calibration.
Innovation Solution
An integrated frequency calibration architecture where the free-running VCO operates in both normal and calibration modes, with a phase lock loop and tuning voltage measurement, and a reference crystal oscillator located on the DSP module, allowing for digital board-to-board connections and reduced noise, and incorporating a VCO tuning circuit on the RF module for precise frequency control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If discrete components are assembled on printed circuit boards, then the radar system can be constructed with separate functional modules, but the overall system size increases and becomes bulky
Solution Approach 1:
The patent combines the calibration VCO and free-running VCO into a single shared VCO structure. The calibration function is integrated by using the same VCO for both calibration and normal operation, eliminating the need for separate calibration hardware components and reducing overall system volume while maintaining modular assembly benefits.
2Measurement precision
If a separate calibration VCO is used for frequency calibration, then accurate frequency calibration can be achieved, but the system cost and space usage increase
Solution Approach 1:
The VCO is designed to serve dual purposes: frequency calibration during initialization and normal radar operation. The same VCO structure performs both calibration and signal generation functions, eliminating the need for a separate calibration VCO and reducing device complexity while maintaining calibration accuracy through the shared phase-locked loop mechanism.
3Ease of operation
If the tuning voltage is transmitted across board-to-board connections, then the VCO can be controlled from the DSP module, but the tuning voltage becomes more susceptible to noise
Solution Approach 1:
The patent extracts the VCO and its control circuitry from the RF module and places it on the DSP module, co-locating the voltage control oscillator with its control logic. This eliminates the need for analog tuning voltage transmission across board-to-board connections, removing the noise susceptibility associated with long analog signal paths while maintaining ease of operation through integrated digital control.
4Measurement precision
If the calibration VCO operates at the same frequency as the free-running VCO, then frequency calibration can be performed, but signal interference and noise increase due to signals with similar frequencies in close proximity
Solution Approach 1:
The patent implements periodic frequency sweeping of the VCO during calibration mode, where the VCO frequency is swept across a range including the reference frequency. This periodic sweeping approach allows calibration to be performed at specific moments in time rather than continuously, reducing signal interference while maintaining calibration capability through time-separated operation modes.
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 reduces system size, minimizes noise interference, and eliminates the need for a separate calibration VCO, resulting in a more compact, accurate, and cost-effective frequency calibration method for automotive radar systems.
Implementation Method 1
frequency calibrating a free running voltage controlled oscillator comprises implementing a phase lock loop on the voltage controlled oscillator at a programmed frequency
Implementation Method 2
a mixer translates the reference frequency to direct current (DC), causing an impulse in the baseband filter
Data Source
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AI summary
In an exemplary embodiment, a free running VCO has two modes: a normal operating mode and a calibration mode. In the calibration mode, the free running VCO is phase lock looped with itself instead of a calibration VCO. Furthermore, in an exemplary embodiment, a tuning voltage for the free running VCO is adjusted to offset any tuning error. In addition, in various embodiments a reference crystal oscillator used in the phase lock loop is located on a DSP module instead of on the RF module. In yet another exemplary embodiment, the free running VCO is the only high frequency VCO on a radio frequency module.