GPS Receiver Digital Threshold Loop for Narrowband Jamming Rejection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing GPS receivers face challenges in interference resistance, particularly with narrow-band Gaussian-type interference signals, due to the variability of radiofrequency elements and limited bandwidth, making it difficult to calibrate and effectively reject subtle interference.
Innovation Solution
A receiver design with a digital section that includes a fixed-gain amplifier and an amplitude bit threshold feedback loop, allowing for constant duty cycle maintenance and conversion of narrowband jamming signals into sinusoidal signals, thereby overcoming the limitations of analog and radiofrequency elements and expanding the loop's bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If variable gain amplifiers are used in the analog section to normalize instantaneous peak amplitude, then narrowband jamming signals can be converted into sinusoidal signals, but the variability of radiofrequency elements makes calibration difficult and reduces manufacturing precision
Solution Approach 1:
The patent replaces the analog variable gain amplifier system with a digital signal processing system. The analog section uses fixed gain amplifiers, and the normalization function is transferred to the digital section where threshold values are dynamically adjusted based on signal characteristics. This substitution eliminates the calibration problems associated with analog variable gain elements while maintaining the ability to convert narrowband jamming signals into sinusoidal signals for effective rejection.
Solution Approach 2:
The patent changes the operating parameters from analog variable gain control to digital threshold adjustment. By modifying the decision thresholds in the digital section rather than changing analog amplifier gains, the system achieves dynamic adaptation to signal conditions without the manufacturing and calibration issues of variable gain amplifiers. The digital thresholds can be precisely controlled and adjusted based on detected signal characteristics.
2Adaptability or versatility
If analog gain control loops are implemented with variable gain amplifiers, then signal levels can be dynamically adjusted, but the loop bandwidth is limited and reaction time is increased
Solution Approach 1:
The patent replaces the analog gain control loop with a digital threshold adjustment mechanism. Instead of using variable gain amplifiers controlled by analog loops, the system uses fixed gain amplifiers combined with digital signal processing that dynamically adjusts decision thresholds. This digital approach eliminates the bandwidth limitations and slow response characteristics of analog control loops while maintaining dynamic adaptation capability.
Solution Approach 2:
The patent implements preliminary normalization in the analog section using fixed gain amplifiers, so that the signal is pre-conditioned before entering the digital section. This preliminary action reduces the burden on the digital processing stage and allows faster response times compared to relying solely on slow analog control loops for all adjustments.
3Adaptability or versatility
If multi-channel systems are implemented, then reception capability is improved, but differential errors between channels make calibration extremely difficult
Solution Approach 1:
The patent replaces analog variable gain control with digital signal processing in multi-channel systems. By using fixed gain amplifiers in the analog section and performing all dynamic adjustments digitally, the system eliminates the differential errors between channels that plague analog multi-channel systems. Each channel can be independently calibrated with fixed gain elements, and digital processing ensures consistent performance across all channels without the compounding calibration difficulties of multiple variable gain amplifiers.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The receiver has an analog section (5) comprising a controller (50) with an amplifier (51), and an analog-to-digital converter (55) in output of the controller. A digital section (6) is formed downstream of the analog section, and comprises a comparator (62) arranged to work out an amplitude bit (M) on basis of comparison of an output signal of the analog section with an amplitude bit threshold. The digital section comprises a threshold control loop arranged to maintain an activity duty cycle of the bit as constant and to convert a narrow band jamming signal into a sinusoidal jamming signal. An independent claim is also included for a method for receiving a radio frequency signal, which is embedded in a jamming signal by a receiver.