{"id":29054,"date":"2017-11-08T09:20:58","date_gmt":"2017-11-08T13:20:58","guid":{"rendered":"https:\/\/swling.com\/blog\/?p=29054"},"modified":"2017-11-08T09:20:58","modified_gmt":"2017-11-08T13:20:58","slug":"airspys-latest-the-airspy-hf-sdr","status":"publish","type":"post","link":"https:\/\/swling.com\/blog\/2017\/11\/airspys-latest-the-airspy-hf-sdr\/","title":{"rendered":"Airspy’s latest: The Airspy HF+ SDR"},"content":{"rendered":"

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SDR manufacturer, Airspy, has a new product shipping “really really really soon” (per their website<\/a>). The Airspy HF+ promises improved frequency agility through the use of high-performance passive mixers with a polyphase harmonic rejection structure. Airspy states that no external band filters are required as they are with many budget SDRs.<\/p>\n

There are many other improvements over their previous iterations. Here’s the product information copied from the Airspy HF+ page on Airspy’s website:<\/p>\n

(Source: Airspy<\/a>)<\/p>\n

The Software Defined Radio revolution brought great flexibility in VHF and UHF reception. Today we offer the best wide band receivers which address these needs. We also provide a high performance extension for weak-signal wide band reception on HF \u2013 something other competing solutions fail to address efficiently.<\/p>\n

Airspy HF+ is a paradigm shift in high performance HF radio design. It is a joint effort between Airspy, Itead Studio and a top-tier semiconductor company to build a state of the art SDR for HF and VHF bands.<\/p>\n

Like most high-end HF receivers, the HF+ uses very high dynamic range ADC\u2019s and front-ends. But unlike the current offerings in the market, it also brings more frequency agility by using high performance passive mixers with an excellent polyphase harmonic rejection structure. No external band aid filters are required like the lower end HF receivers, which makes it the ideal companion for light portable high performance operation.<\/p>\n

Both the architecture and level of integration achieved in this design allow us to bring top performance reception at a very affordable price.<\/p>\n

All the major SDR software is supported. Check the download page.<\/p>\n

State of the Art SDR streaming technology!<\/h2>\n

We concentrated state of the art DSP and networking techniques into our SpyServer software to allow multiple users to stream high quality IQ data from the same receiver at the same time. No compromises in the quality were made like it is usually done in Web SDR interfaces. You get actual IQ data you can process with your plugins and extract the last bit of information out of it.
\nThe server software is highly scalable and can run on computers as small as the\u00a0$7 Orange Pi Zero<\/a>\u00a0to top end 64bit servers with multiple cores\/cpus, including the popular Raspberry Pi series.<\/p>\n

HF Tuner<\/h3>\n

Airspy HF+<\/strong>\u00a0achieves excellent HF performance by means of a\u00a0low-loss band filter<\/strong>,\u00a0high linearity LNA<\/strong>,\u00a0high linearity tunable RF filter<\/strong>, a\u00a0polyphase harmonic rejection (HR) mixer<\/strong>\u00a0that rejects up to the 21st harmonic and multi-stage analog and digital\u00a0IF filtering<\/strong>.
\nThe 6 dB-stepped AGC gain is fully controlled by the software running in the DSP which optimizes the gain distribution in real time for optimal sensitivity and linearity. Harmonic rejection is a key issue in wide band HF receivers because of the large input signal bandwidth of the input signal. The output of the IF-filter is then digitalized by a high dynamic range sigma delta IF ADC for further signal processing in the digital domain.<\/p>\n

VHF Tuners<\/h3>\n

Excellent VHF performance is also achieved by using optimized signal paths composed of\u00a0band filters<\/strong>,\u00a0high linearity LNAs<\/strong>\u00a0with a stepped AGC, a\u00a0polyphase harmonic rejection mixer<\/strong>\u00a0and\u00a0IF filters<\/strong>\u00a0optimized for their respective bands.
\nThe amplifier gain is switchable in 3 dB-steps and fully controlled by the AGC running in the DSP. The RF signal is converted to baseband by a high linearity passive mixer with a polyphase harmonic rejection structure. The low-IF signal is then converted into the digital domain by the same IF ADC used in the HF chain.<\/p>\n

IF Sampling<\/h3>\n

The IF analog to digital converter (ADC) is a 4th order multi-bit noise shaping topology; it features very high dynamic range and linearity. The IF-ADC sampling rate is determined by a control algorithm running in the embedded DSP. This advanced technique adjusts the sampling rate depending on the tuning frequency with the goal of avoiding the disturbances and spurs generated by the switching discrete-time sections of the IF-ADC.<\/p>\n

Digital Down Converter<\/h3>\n

Once the IF signal is digitalized, the high sample rate I\/Q stream is then frequency translated and processed with cascaded CIC and FIR decimation stages. After every stage, the sample rate is reduced and the resolution increased. The final signal at the output has\u00a018bit<\/strong>\u00a0resolution and an alias rejection performance of\u00a0108 dBc<\/strong>. The data is then scaled to 16bit and sent to the Micro-Controller for streaming over USB.<\/p>\n

Architectural Advantages<\/h3>\n

The main advantages over techniques from the legacy super-heterodynes up to the now mainstream direct sampling is that the whole receiver chain is well protected against out of band blockers while still relaxing the RF filtering constraints, making it simple and cost effective.
\nThe natural filtering of the sigma-delta ADC combined with the excellent linearity and sensitivity of the analog chain reaches an unprecedented level of performance and integration.<\/p>\n

Use it over the network!<\/h3>\n

Connect as many SDR applications as needed to the\u00a0HF+<\/strong>, over the Internet or in your own local network with near zero latency thanks to the new SPY Server software.
\nThis setup basically brings all the flexibility of Web based SDRs while still benefiting from the full power of desktop applications. The IQ data is processed in the server with state of the art DSP and only the required chunk of spectrum is sent over the network. What is sent is the actual IQ signal, not compressed audio. This means you can use all your favorite plugins to process the IF, eliminate noise and perform heavy lifting of the signals as you are used to do with locally connected SDR\u2019s.
\nWe have a tradition of building multi-tools, so we made sure the SPY Server runs on 32\/64bit Windows and Linux on Intel and ARM processors without any compromises. Low cost Raspberry Pi 3 and Odroid boards are in the party.<\/p>\n

Technical specifications<\/h2>\n
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