Mixed-Domain Oscilloscope Internal Chirp Generator Time Alignment
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Solution Overview
Problem
Mixed-domain oscilloscopes lack the capability to provide 'poor man's network analyzer' functionality due to their use of fixed local oscillators, which restricts their ability to perform vector measurements, unlike traditional spectrum analyzers that use swept or stepped LOs.
Innovation Solution
Incorporating an internal chirp generator and time alignment logic, allowing the MDO to transmit a chirp signal and align it with acquisitions, enabling the measurement of scalar S parameters and other parameters like distance-to-fault, by processing a large swath of frequencies simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional swept or stepped LO approach is used in MDO, then the instrument can provide 'poor man's network analyzer' capability, but the MDO cannot perform vector measurements
Solution Approach 1:
The patent implements a dynamic chirp signal generator that produces frequency-modulated signals with linearly varying frequency over time. This dynamic frequency modulation allows the MDO to sweep through a wide bandwidth range while maintaining the ability to perform both scalar and vector measurements, resolving the contradiction between adaptability and measurement precision.
Solution Approach 2:
The patent changes the operating parameters by using a chirp signal with continuously varying frequency instead of fixed or stepped LO frequencies. This parameter change enables the system to cover wide bandwidths while maintaining phase coherence necessary for vector measurements, thus resolving the technical contradiction.
2Device complexity
If fixed local oscillators are used in MDO, then the instrument structure is simplified, but the ability to process wide bandwidth and perform scalar measurements is limited
Solution Approach 1:
The patent employs periodic chirp signals that sweep through the frequency range in a systematic manner. This periodic frequency modulation allows the simplified fixed LO structure to effectively process wide bandwidths by sequentially sampling different frequency segments, maintaining structural simplicity while enhancing bandwidth processing capability.
Solution Approach 2:
The fixed LO structure is enhanced with dynamic frequency modulation through the chirp generator, allowing the system to adapt to wide bandwidth requirements without changing the fundamental fixed LO architecture, thus resolving the contradiction between device complexity and adaptability.
3Measurement precision
If swept or stepped LO method is used, then scalar measurements can be obtained, but time alignment with acquisition is difficult
Solution Approach 1:
The patent introduces a time alignment logic unit that acts as an intermediary between the chirp signal generator and the acquisition system. This intermediary component receives timing information from the chirp generator and uses it to precisely synchronize the acquisition window with the signal under test, eliminating time alignment errors while maintaining scalar measurement accuracy.
Solution Approach 2:
The system implements feedback mechanisms where timing information from the chirp signal is fed back to the acquisition trigger system, enabling automatic time alignment. This feedback loop ensures that scalar measurements are accurately correlated with the corresponding time intervals, resolving the contradiction between measurement precision and time alignment accuracy.
Data Source
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AI summary
A mixed-domain oscilloscope (MDO 105) includes a signal generator (160) configured to generate a test signal (137) having a span ranging from a user-configurable start frequency to a user configurable stop frequency, an output channel (115) coupled to the signal generator and configured to transmit the test signal, an RF input channel (120) configured to receive a return signal (142) based on the test signal, an acquisition section (114) configured to acquire and digitize the return signal as an acquisition record, and a ramp busy signal generator (170) configured to substantially time-align the acquisition record with the test signal. The test signal includes a chirp signal that is a linearly swept sine wave that spans between the user-configurable start frequency and the user-configurable stop frequency. Methods include calibrating the chirp signal, connecting the MDO in various test configurations relative to external return loss bridge and DUT equipment, and performing measurements such as S21 (db), S11(db), and distance-to-fault type measurements.