Monday, 13 January 2014

Christmas comes late: Red Pitaya- Software defined instrumentation- order for first batch

I occasionally troll through the "Kickstarter" projects for interesting ones, with both BladeRF and HackRF having their funding from there.

Some weeks ago I came across the "Red Pitaya" It seemed like "manna from heaven", a software-defined instrumentation system. Just what I wanted, not having the deep pockets needed for serious HF test gear.

I thought I had missed out on the first run, but was down for a subsequent one. However, I received a quote last night, that I immediately accepted. They are due to be shipped February 24, that's only about 45 sleeps... plus shipping time from Slovenia (Eastern Europe is booming, we don't hear much about it here (Australia). I will try and write it up on my other blog on multilevel change)

These are the objectives:

OSCILLOSCOPE: 2 channels @ 125 MS/s 14 bit digital with external or signal based triggering capability
SPECTRUM ANALYZER: 2 channels with 50 MHz bandwidth signal with waterfall diagram capability
ARBITRARY WAVEFORM GENERATOR: 2 channels @ 125 MHz 14 bit arbitrary waveform generation with external triggering capability
FREQUENCY RESPONSE ANALYZER: 2 channels with 60 MHz bandwidth
2x2 MIMO PID programmable controller"
This is what it looks like, except the production ones are red:
The "diagnostics kit" I have ordered includes a couple of probes and the software on an SD card. (Edit) The device runs Linux on its own CPU, loaded on the SD card, but the device can interface to tablets and PCs for a GUI.
The Red Pitaya (0-60 MHz) is a bit of a HF version of the UHF BladeRF (300 - 3000 MHz), albeit with the Red Pitaya being ADC-based compared with the BladeRF using a field programmable RF transceiver. (Edit)  The distinction seems a bit blurred as the first block of the TRX is an ADC. Reading the lower RX part of the block diagram, the chip has the usual elements of a superhet RX; RF amplifier, (quadrature) mixer, IF filters and amplifiers, before the ADC (see LMS6002D data sheet for more detail). The BladeRF TRX chip has a conventional RF frontend ahead of the ADCs as they can't sample at the 300 - 3000 MHz range.
As such, the BladeRF only needs a simple RF frontend so it can be attached to an antenna (see schematics on Nuand site). However, the need for sophisticated RF filtering is a major issue in the amateur SDR community, primarily to get selectivity. (1st IF taps in conventional TRX are one way around this; see other posts)

The Red Pitaya has the high impedance needed for instrumentation, but it would seem it would not require too much to implement a RF frontend for it. The Red Pitaya does work as a spectrum analyser, which are basically radios without the demodulation. One of the projected further uses of the Red Pitaya is as a SDR (RX and/or TRX?), so we shall have to wait and see.
Ironically, I use my BladeRF with SDR Console V2 as a spectrum analyser for my work on amateur TV, in which it excels. See other blog posts for details.

Ok, I dug a hole, then dug deeper! The distinction between the different devices, be they RX, TX, TRX or test instruments gets blurred with software-defined gear.

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