Gated Sweep Local Oscillator Pre-Sweep Transient Stabilization
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Solution Overview
Problem
Existing spectrum and power measurements on time-varying signals face challenges due to inaccurate triggering, transient responses of analyzer components, and the need for multiple sweep segments, leading to measurement errors and inefficiencies in time-gated techniques like Gated LO, Gated Video, and Gated FFT.
Innovation Solution
Implementing an intelligent local oscillator (LO) with pre-sweep and post-sweep functions, allowing for stabilization of LO and IF filter transients before measurement and a calibrated back-up operation to ensure linear sweeping and accurate frequency resetting between gate segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Gated LO measurements are used to achieve flexible frequency span and faster measurement completion, then measurement speed and flexibility are improved, but transient response errors and LO settling delays increase measurement inaccuracies
Solution Approach 1:
The patent applies preliminary action by performing a pre-sweep of the local oscillator before the actual measurement sweep. This pre-sweep prepares the LO and IF filters in advance, allowing them to be in a known state at the start of the measurement, thereby eliminating settling transients and improving frequency accuracy without sacrificing measurement speed.
Solution Approach 2:
The patent implements feedback by measuring the actual LO frequency at the start and end of each sweep segment using a frequency counter, then using this measured information to correct frequency errors in the spectrum display. This closed-loop approach compensates for LO non-ideal behavior and maintains measurement precision.
2Adaptability or versatility
If multiple sweep segments are required to complete a spectrum measurement with gated LO, then frequency span coverage is improved, but the number of segments increases measurement complexity and time
Solution Approach 1:
The patent uses feedback to measure and record the actual frequency span covered in each sweep segment, then uses this information to automatically calculate and adjust the display frequency span to match the actual measured range. This eliminates the need for conservative span estimates and reduces the number of segments required.
Solution Approach 2:
The patent dynamically changes the display frequency span parameter based on actual measurement data from each sweep segment. By adjusting the displayed span to match the actual measured frequencies, the system achieves complete frequency coverage with fewer segments and reduced complexity.
3Ease of operation
If LO sweeping is performed precisely for the duration of the gate, then measurement timing is simplified, but frequency errors accumulate due to non-ideal LO behavior at segment boundaries
Solution Approach 1:
The patent applies preliminary action by performing a pre-sweep before the measurement gate to establish a known starting frequency for the LO. This pre-sweep ensures the LO begins at an accurate frequency point, preventing error accumulation at segment boundaries while maintaining simple gate-synchronized timing.
Solution Approach 2:
The patent implements feedback by measuring the actual LO frequency at the start and end of each sweep segment with a frequency counter, then using these measured values to correct frequency display errors. This compensates for LO non-ideal behavior without complicating the basic gate-synchronized sweeping operation.
4Measurement precision
If delay is added to the measurement process to account for IF filter settling time, then transient response errors are reduced, but measurement speed decreases
Solution Approach 1:
The patent applies preliminary action by performing a pre-sweep that allows the IF filters to settle before the actual measurement begins. This pre-sweep prepares the filter bank in advance, eliminating the need for additional delay time during the measurement gate and maintaining high measurement speed while ensuring accurate frequency response.
Solution Approach 2:
The patent converts the potentially harmful effect of filter settling time into a benefit by using the pre-sweep period specifically for this purpose. The time that would otherwise be wasted as delay is instead utilized to prepare the IF filters, transforming a source of error into a preparation opportunity that improves both accuracy and speed.
Data Source
AI summary
A measurement technique that provides a full solution to the gated local oscillator sweep measurement and improves the accuracy of signal analyzers in gated sweep mode by pre-sweeping the local oscillator at the beginning of a gate pulse and over-sweeping the local oscillator at the end of each gate pulse.