Digitally Tuned Band-Stop Filter for Frequency-Hopping Interference
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Solution Overview
Problem
Frequency-hopping spread spectrum communications are susceptible to interference from collocated radio frequency emitters, leading to loss or corruption of information, especially in critical mission communications, as conventional filters can inadvertently attenuate both interfering and intended signals, making it difficult to discern the signal of interest.
Innovation Solution
A digitally tuned frequency hopping band-stop filter circuit with a tunable filter and a tuning processor that adjusts filter control signals based on input and output power comparisons to attenuate interfering signals while minimizing attenuation of intended signals, using a sampling system to detect and adjust for excessive attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional filters are used to block interfering signals, then interference from collocated RF emitters is reduced, but intended signals are also attenuated
Solution Approach 1:
The filter dynamically adjusts its frequency response by hopping between different stopband frequencies according to a pseudorandom sequence, allowing it to adaptively block interfering signals while passing intended signals at different frequencies
Solution Approach 2:
The filter changes its stopband frequency parameter over time according to a pseudorandom hopping sequence, transforming from a static filter into a time-varying filter that can distinguish between interfering and intended signals based on frequency position
2Object-affected harmful factors
If the filter attenuates interfering signals strongly, then interference is reduced, but the signal of interest may be excessively attenuated
Solution Approach 1:
The filter incorporates power samplers that monitor input and output signal powers and feed this information back to adjust the filter's operation, ensuring that intended signals are not excessively attenuated while interfering signals are blocked
Solution Approach 2:
The filter applies partial attenuation by using a pseudorandom hopping sequence that only blocks interfering frequencies at specific times, allowing intended signals to pass through when the filter is not positioned at their frequencies
Data Source
AI summary
A digitally-tunable filter includes a tunable filter circuit (110) for generating an output signal by processing an input signal based at least on a plurality of filter control signals (114). The filter also includes an input power sampler (118) for sampling an input power of the input signal, an output power sampler (120) for sampling an output power of the output signal, and a tuning processor (112) for generating the plurality of filter control signals based on at least one channel control signal (116) associated with a current communications channel and a comparison of the input and the output powers. In the filter, the plurality of control signals configure the tunable filter circuit to attenuate at least a portion of the input signal if a difference between the input power and the output power is less than a threshold value.