RF Signal Measurement Using Re-sampled ADC Clock
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for measuring device under test (DUT) parameters using repetitive complex modulated RF signals face challenges when pulse widths are less than the repetition period, as the RF signal becomes chopped, making it difficult to reconstruct and measure the complex modulation.
Innovation Solution
A test system that generates a complex and pulse modulated RF signal with on-pulses shorter than the repetition period, allowing for accurate measurement by sampling the IF signal at a re-sampled ADC clock frequency, which aligns with the pulsed waveform, enabling effective digitization and reconstruction of the RF signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pulse width is made shorter than repetition period to enable measurement of pulsed RF signals, then measurement capability is improved, but signal reconstruction becomes difficult and measurement precision deteriorates
Solution Approach 1:
The system performs preliminary synchronization by locking the ADC sampling clock to the pulse repetition frequency before signal acquisition. This preliminary action ensures that sampling occurs at optimal moments within each pulse cycle, enabling accurate reconstruction of pulsed RF signals even when pulse width is shorter than the repetition period.
Solution Approach 2:
The invention utilizes periodic pulse modulation with repetition frequencies between 100 Hz to 10 kHz, synchronizing the ADC sampling process to this periodic pattern. By aligning sampling cycles with the periodic pulse structure, the system can accurately capture and reconstruct signals despite the pulse width being less than the repetition period.
2Device complexity
If conventional superheterodyne receiver is used with standard ADC sampling, then device complexity is reduced, but measurement precision deteriorates for pulsed modulated signals
Solution Approach 1:
The invention changes the sampling rate parameter dynamically by adjusting the ADC clock frequency to match the pulse repetition frequency of the modulated signal. This parameter adjustment enables the conventional superheterodyne receiver to accurately measure pulsed modulated signals without requiring complex additional hardware, maintaining device simplicity while improving measurement precision.
3Measurement precision
If pulse width is increased above repetition period to maintain signal integrity, then signal reconstruction is simplified, but loss of time increases and productivity decreases
Solution Approach 1:
By utilizing periodic pulse modulation with controlled repetition frequencies (100 Hz to 10 kHz), the system achieves accurate signal reconstruction within each pulse cycle without requiring the pulse width to exceed the repetition period. This periodic approach maintains signal integrity while maximizing measurement throughput and productivity.
Solution Approach 2:
The preliminary synchronization of ADC sampling to pulse repetition frequency ensures that each pulse is sampled optimally, enabling complete signal reconstruction within the available pulse width. This eliminates the need to increase pulse width beyond the repetition period, thereby maintaining high measurement productivity.
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
Enables accurate measurement of DUT parameters even when pulse widths are shorter than the repetition period, expanding the types of RF signals that can be measured and simplifying digital filtering requirements.
Implementation Method 1
the superheterodyne receiver acquires the output RF signal, down converts the output RF signal to a lower frequency intermediate frequency (IF) signal
Implementation Method 2
The IF signal may be digitized using an analog to digital converter (ADC), which samples the IF signal at a lower rate than the modulation
Data Source
AI summary
A method for measuring modulated radio frequency (RF) signals from a device under test (DUT) includes inputting a test RF signal to the DUT, where the test RF signal is modulated with a repetitive complex waveform and a pulsed waveform, the repetitive complex waveform including multiple RF tones with an RF tone spacing and an RF repetition period, where a pulse width of the pulsed waveform is less than the RF repetition period; acquiring an output RF signal from the DUT responsive to the input test RF signal; down converting the output RF signal to an intermediate frequency (IF) signal; sampling the IF signal using an analog to digital converter (ADC) having an ADC clock frequency; measuring ADC samples of the IF signal; and reconstructing the test RF signal modulated with the repetitive complex waveform using the measured ADC samples.