RF BIST Using PLL Oscillator to Avoid Intermodulation Distortion
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Solution Overview
Problem
Existing built-in self-test (BIST) methods for radio frequency systems face complications such as intermodulation distortion and image signals due to digital-to-analog conversion and frequency upconversion processes, which complicate reliability and increase testing costs.
Innovation Solution
The method generates an analog radio frequency stimulus signal using phase-locked loops (PLLs) or oscillator circuitry, eliminating the need for digital-to-analog conversion and upconversion, thereby avoiding intermodulation distortion and image signals, and allows for direct analysis of the device under test's output signal for performance qualities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If digital-to-analog conversion and frequency upconversion processes are used in BIST, then the system can perform frequency conversion, but intermodulation distortion and image signals are introduced which complicate reliability and increase testing costs
Solution Approach 1:
The patent extracts and removes the problematic digital-to-analog conversion and frequency upconversion stages from the BIST signal path. By generating the RF stimulus signal directly at the desired frequency using a voltage-controlled oscillator (VCO) within the phase-locked loop, the system eliminates the sources of intermodulation distortion and image signals while retaining the essential frequency conversion capability through the downconverter only.
Solution Approach 2:
Instead of the conventional approach of generating a low-frequency signal and upconverting it to RF, the patent inverts the process by directly generating the RF signal at the target frequency and then downconverting it. This reversal eliminates the need for RF power amplifiers and upconversion mixers, thereby removing the sources of distortion and image signals that compromise BIST reliability.
2Adaptability or versatility
If digital-to-analog conversion and upconversion stages are included, then frequency conversion is achieved, but device complexity and testing costs increase
Solution Approach 1:
The patent removes the unnecessary digital-to-analog converter, RF power amplifier, and upconversion mixer stages from the BIST circuit. By using the phase-locked loop's VCO to generate the RF stimulus signal directly, the system achieves frequency conversion capability with significantly reduced circuit complexity, requiring only the downconverter, analog-to-digital converter, and digital signal processor.
Solution Approach 2:
The phase-locked loop circuit is utilized for multiple functions: it generates the RF stimulus signal, provides frequency synthesis, and enables precise frequency control. This multi-functionality eliminates the need for separate dedicated components for signal generation and frequency conversion, thereby reducing overall device complexity while maintaining full frequency conversion capability.
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 enhances the reliability and efficiency of BIST by reducing distortion and costs, enabling faster and less expensive testing, and allowing for on-chip or system-on-chip implementation, with the ability to measure intermodulation distortion and detect faults within the RF system.
Implementation Method 1
generating an analog radio frequency stimulus signal via oscillator circuitry
Implementation Method 2
the oscillator circuitry is included in a plurality of phase-locked loops and is configured to generate a corresponding plurality of test tones
Implementation Method 3
a frequency conversion stage including at least one of a mixer and a local oscillator
Data Source
AI summary
Techniques for performing built-in self-test (BIST) of performance of an RF system are disclosed. The techniques may be used, for example, for measuring distortion generated by the RF system under test, detecting faults in the system, determining calibration of the system, and/or assisting in compensating analog circuitry that is sensitive to temperature, supply voltage, and/or process variations. Also, a BIST architecture for determining RF performance of an RF systems is disclosed.