How to record IQ data to external USB hard disk with  spectrum analyzer? - Page 1
Forum section: electronics / testgear

author: nicegirl
author_rank: Contributor
timestamp: March 06, 2022, 03:31:57 pm
content: I bought a 2nd hand keysight n9020a spectrum analyzer.I plan to connect this spectrum analyzer with external USB hard disk,then record the IQ data of signal.Googled lots of topics,but has no any answer.How to record IQ data to external USB hard disk with spectrum analyzer(such as keysight n9020a)?Thanks in advance.

author: rob77
author_rank: Super Contributor
timestamp: March 06, 2022, 06:51:05 pm
content: does any SA support such a thing ? and even if it supports it, you would be seriously limited by the USB drive's throughput. i highly doubt any SA will have a USB3 port with mass storage support, and USB2 mass storage will limit you to 15Msa/s or below.don't know what your use case would be , but i would definitely go for a SDR hardware and a computer for recording. USB2 SDR connected to a computer with SSD storage will easily get you to 20Msa/s. if you invest into a USB3 or PCIe SDR hardware the max bandwidth will be much higher.

author: rob77
author_rank: Super Contributor
timestamp: March 06, 2022, 06:59:49 pm
content: checked the n9020a brochure.... it has USB2 ports only and analysis bandwidth of 160MHz.. that would yield 320Mbyte/s of IQ data at 8 bit resolution... that's only 10 times more data than the USB2 mass storage can handle

author: Joel_Dunsmore
author_rank: Regular Contributor
timestamp: March 07, 2022, 01:17:33 am
content: Quote from: nicegirl on March 06, 2022, 03:31:57 pmNever done direct saves like that. But for sure you can load up the VSA code (89600) and then do a one-time capture, then save the IQ data from VSA. I have done that myself recently, see this example from ARFTG/RWW student-design contest for doing some DPD work:(actually, I was running the 89600 on a PNA and UXA but the 89600 code is the same). The part you want is starts at 10:50 in the video.

author: pdenisowski
author_rank: Super Contributor
timestamp: March 11, 2022, 12:36:05 am
content: Quote from: rob77 on March 06, 2022, 06:51:05 pmIt's important to differentiate between capturing and saving a relatively short snapshot of IQ data and streaming IQ data to an external device. Many Rohde and Schwarz spectrum analyzers and receivers can do both.In the first case, the IQ data is acquired and stored locally on the analyzer and then this data is copied as a file to a USB drive (so drive throughput is not critical). However, the capture length is usually on the order of milliseconds or single digit seconds, depending on the IQ "bandwidth".https://www.rohde-schwarz.com/webhelp/FSW_HTML_UserManuals_en/Content/subprojects/fsw_k70/2b759318b3654a88.htm?Highlight=exportIn the second case, a special high-speed interface can be used to stream data to an external device that can record very large amounts of IQ data either for analysis or for reply using a vector signal generator.https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_common_library/dl_brochures_and_datasheets/pdf_1/IQW_bro_en_5215-7951-12_v0900.pdf

author: nicegirl
author_rank: Contributor
timestamp: March 11, 2022, 08:09:20 am
content: True.Can I record IQ data into internal hard disk and copy data through USB?

author: Joel_Dunsmore
author_rank: Regular Contributor
timestamp: March 11, 2022, 08:50:01 pm
content: Not sure of that directly. Here is an old video of a streaming solution:

author: geggi1
author_rank: Frequent Contributor
timestamp: March 11, 2022, 09:17:57 pm
content: I see from some of your other postings that you are posting about VLF and lower frequencies and assume that this post ins in the same area of frequency.You should look into RTL-SDR dongles with a up-converter. Some of the SDR sowtware can store to disc and can maybe be used for your project.

author: rob77
author_rank: Super Contributor
timestamp: March 14, 2022, 07:21:56 am
content: Quote from: geggi1 on March 11, 2022, 09:17:57 pmyou can easily do that in gnuradio , the gnuradio companion is an amazing visual tool to play around with SDR devices

author: Berni
author_rank: Super Contributor
timestamp: March 14, 2022, 10:10:48 am
content: Nice bit of kit you bought there.According to the datasheet the instrument is capable of making 4M point long captures of IQ data. So at full analysis bandwidth this gives you a few 10s of milliseconds of recording time in one continuous capture.But since you are talking about the external drive i would guess you have long recordings in mind. For that this instrument is unfortunately the wrong tool for the job. What you actually want for this is a SDR radio. Those will continuously receive the signal into IQ and stream it over USB in real time. You can fit a lot of IQ data over a USB 3.0 port. Then you typically just just need a console app to write that data directly to a disk drive.There are really cheep SDRs like the RTL SDR or you can get more proper better performing purpose built SDRs like the HackRF One, BladeRF, SignalHound... etc. Also no worries if the 3 or 6 or 8GHz or whatever is not enough for you, you can still buy buy a mixer block from MiniCircuits and feed in a carrier from a RF synthesizer to get it receiving at any frequency you like. If you got a 100GHz synthesizer and mixer around then you can receive 100GHz signals.

author: PA0PBZ
author_rank: Super Contributor
timestamp: March 14, 2022, 10:51:57 am
content: Judging from your other posts it looks like you are interested in 10Hz-9KHz, did you know that your PC already has a receiver for that built-in? It's called soundcardThere's lots of software that can create and store I/Q data from that, no need for anything fancy like a spectrum analyzer!

author: nicegirl
author_rank: Contributor
timestamp: March 14, 2022, 04:16:00 pm
content: It's the first time I know this.I has only antenna with sma connection,I have no idea how to connect antenna to sound card.Could you pls help to give some tutorial to know the requirement of antenna and sound card.

author: Berni
author_rank: Super Contributor
timestamp: March 14, 2022, 06:22:04 pm
content: You seam to be very confused...What are you trying to do anyway?

author: geggi1
author_rank: Frequent Contributor
timestamp: March 14, 2022, 08:32:54 pm
content: Google SAQ soundcard reciever.https://alexander.n.se/en/the-radio-station-saq-grimeton/lyssna-pa-saq/http://www.dl1dbc.net/SAQ/https://www.prinz.nl/SAQ.htmlYou should also look into the early SDR recievers like the Softrock that probably can be modified to these low frequencies.