Open-Loop VCO Self-Test for Multiband Frequency Verification
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Solution Overview
Problem
The complexity of electronic devices has increased the need for reliable testing of digital circuits, but existing methods often require expensive and time-consuming automated test equipment, especially for multiband voltage controlled oscillators (VCOs), which are difficult to test accurately due to high frequencies and extensive testing times.
Innovation Solution
Implementing built-in self-test (BIST) circuitry with a programmable Vtune voltage generator integrated into coarse tuning circuitry allows for self-testing of multiband VCOs in an open loop configuration, reducing the need for external test equipment and improving testing efficiency by measuring frequency overlap, monotonicity, and range errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external test equipment is used to test multiband VCOs, then measurement accuracy can be achieved, but testing time increases and costs increase
Solution Approach 1:
The patent implements a built-in self-test (BIST) mechanism where the VCO tests itself using internal circuitry including a test counter, frequency-to-digital converter, and control logic. The VCO output is fed back to its own input through a test mode switch, allowing the device to autonomously measure its frequency characteristics without external equipment, thereby eliminating testing time loss while maintaining measurement precision through calibrated internal reference circuits
Solution Approach 2:
The test equipment is integrated directly into the VCO circuitry, making the VCO multi-functional by combining both oscillation generation and self-testing capabilities. The same VCO circuit serves dual purposes: normal operation mode and self-test mode, eliminating the need for separate external testing equipment and reducing both time and cost overhead
2Reliability
If external test equipment is used to test multiband VCOs, then comprehensive testing can be performed, but costs increase
Solution Approach 1:
The patent merges the test equipment functions directly into the VCO integrated circuit by combining the test counter, frequency-to-digital converter, mode switch, and control logic with the VCO's existing circuitry. This integration eliminates separate testing equipment and reduces system cost while maintaining comprehensive testing capability across all VCO frequency bands through the multi-band test mode
Solution Approach 2:
The VCO performs comprehensive self-testing using its own internal resources including its output signal, internal counters, and digital converters. The self-test mechanism autonomously evaluates frequency accuracy, band switching, and modulation performance across all operating bands without requiring external testing equipment, thereby ensuring reliability while minimizing device complexity and cost
3Stability of the object's composition
If traditional closed-loop testing is used, then system stability is maintained, but testing flexibility and speed decrease
Solution Approach 1:
The patent implements a dynamic testing approach by introducing a mode switch that allows the VCO to operate in either normal closed-loop mode or self-test open-loop mode. During self-testing, the feedback loop is temporarily reconfigured to feed the output back to the input through a test path, enabling rapid frequency measurement and band switching evaluation without the constraints of maintaining system stability, thereby increasing testing speed while preserving stability during normal operation
Data Source
AI summary
Methods and apparatus for self testing a multiband voltage controlled oscillator (VCO) are disclosed. A tuning voltage of the VCO is adjusted where the output of the VCO does not affect the input to the VCO. Frequency bands in the VCO are selected. Output frequencies of the VCO are measured.