Dual-Path Angle Modulator With Continuous Gain Calibration
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Solution Overview
Problem
Conventional dual path angle modulators require calibration procedures that disrupt normal operation and are impractical for systems like CDMA, where continuous operation is necessary, due to the need for matching gains in both modulation paths to prevent noise normalization and ensure accurate wide bandwidth angle modulation.
Innovation Solution
A multiple path angle modulator with a closed secondary loop that automatically adjusts the high frequency gain scaling factor in real-time, allowing continuous calibration of both phase modulation paths during normal operation, eliminating the need for shutdowns or specific calibration timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single wide band loop is used for phase modulation, then the modulation bandwidth is sufficient for high speed links, but a lot of noise is present in the output signal
Solution Approach 1:
The phase modulation system is divided into two separate paths: a narrow band main loop for low frequency modulation and a wide band auxiliary path for high frequency modulation. This segmentation allows each path to be optimized for its specific frequency range, with the main loop providing noise filtering for low frequencies and the auxiliary path handling high frequency content without introducing excessive noise.
2Object-affected harmful factors
If a dual path modulation system with a narrow main loop is used, then noise is controlled, but the higher frequencies outside the main loop require additional calibration to ensure flat overall gain
Solution Approach 1:
A feedback mechanism is implemented where the output of the main loop is mixed with the auxiliary path output, and the combined signal is fed back to an ADC for digital processing. The digital circuitry continuously monitors and adjusts the scaling factor MS to balance the gain between the direct path and auxiliary path, eliminating the need for manual calibration procedures and ensuring flat overall frequency response.
Solution Approach 2:
The scaling factor MS in the auxiliary path is made dynamically adjustable through digital control. By continuously varying this parameter based on feedback from the ADC and digital processing, the system automatically compensates for gain mismatches between paths, eliminating the need for fixed manual calibration and adapting to drift in analog circuitry.
3Measurement precision
If manual calibration procedures are used to balance gain between paths, then accurate wide bandwidth angle modulation is achieved, but normal system operation is disrupted and system downtime is required
Solution Approach 1:
The calibration function is transformed from a discrete, interruptive procedure into a continuous, background process. The digital circuitry continuously monitors the phase and frequency of signals from both paths and dynamically adjusts the scaling factor MS in real-time, ensuring accurate gain balancing is maintained throughout system operation without requiring shutdowns or calibration modes.
Solution Approach 2:
The system performs its own calibration automatically through digital processing of feedback signals. The digital circuitry monitors the output phase and frequency, compares it with the desired modulation signal, and self-adjusts the auxiliary path scaling factor to maintain optimal gain balance, eliminating the need for external calibration equipment or manual intervention.
4Speed
If the auxiliary modulation path gain is increased to cover wider bandwidth, then high frequency modulation is improved, but the mismatch between direct path and auxiliary path increases
Solution Approach 1:
The gain of the auxiliary modulation path is made dynamic rather than fixed. The scaling factor MS is continuously adjusted based on real-time feedback from the ADC and digital processing, allowing the system to optimize the auxiliary path gain for wide bandwidth coverage while simultaneously compensating for any phase or frequency mismatches with the direct path, ensuring both high frequency capability and accurate phase matching are achieved.
Data Source
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AI summary
A multiple path angle modulator includes a closed secondary loop added to a main control loop to automatically adjust a scaling factor related to high frequency gain. The main control loop is configured as a primary path to process the low frequency portion of the angle modulation signal, and the secondary loop is configured as an auxiliary path to process the high frequency portions of the angle modulation signal. The secondary loop senses calibration information and uses it to continuously calibrate the gain within the modulation loop in real time while the system performs its primary operation, thereby eliminating the need for a system shut down or calibration specific timing, such as a lapse time, to balance the modulation paths. Calibration is continuously performed as a background process. The angle modulator is applicable to all modulation type systems.