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Cross-interference in HOK/HKW data #613
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@pasha-ponomarenko has there been any change in the interference behavior after HKW increased the number of range gates (starting in ~April 2023)? And do you know if there is a similar issue at other co-located radar sites such as Syowa or Dome C? |
@egthomas, it looks like HKW switched to 110 gate on 28 March 2023. It did not change in any noticeable way the noise/interference background at HKW, which remained quite bad. It also seems like the overall noise/interference situation at HKW became worse on 2 April 2022. |
Just adding a comment from Sessai on 24 April 2024: |
So it looks like this issue might have a bit wider scope covering Syowa and Dome C radars as well. Now, I wonder if any of these radars keep I&Q data. |
Discussion
Topic: Mitigating cross-interference effects between HOK and HKW radars
Description
Since the inception of HKW radar in 2014 both HOK and HKW datasets appear to contain an excessive amount of "salt-and-pepper" noise. Importantly, it disappears in one radar when another one is not operating. A detailed investigation during my stay in Japan in early 2023 revealed that this interference is caused by power spikes surrounding additional blanking pulses designed to protect receiving circuitry in one radar from emission of the other one. As the radars use different pulse sequences and number of range gates, the additional blanking pulses are distributed more or less randomly across all range gates. This component is highly visible in FITACF3 data but it is effectively "swept under the carpet" in FITAF2.5 data by overfiltering together with a large amount of otherwise valid data. The HOK/HKW SuperDARN engineer Mr Hamaguchi suggested that we can effectively remove the switch-related power spikes in I&Q data by identifying the pulse locations through low values of sample power. Our preliminary tests using IDL DLLs from RST showed that this approach works for at least some typical data, and now we should implement the I&Q filtering in RST. Emma has already started working on this.
A detailed description of this artifact and preliminary results of its mitigation can be found in our SD'23 presentation "Cross-interference effects at Hokkaido East/Hokkaido West radars: source identification and problem mitigation"
(2-Ponomarenko_Interference.pdf)
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Details
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Example of cross-interference:
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