[USRP-users] N210 / WBX General Questions
[USRP-users] N210 / WBX General Questions
Hi,
Q1 -- 25 Ms/s -- excellent info.
Q2 -- any info would be appreciated. I guess I'm wondering about MDS
(sensitivity) and Dynamic range. The filters in the N210 would be
interesting -- how good are they, for example one radio I have is
quotes as 115+ dB 80% alias free.
Obviously I'll see this for myself once I get the hardware, I'm just
wonder what I can expect.
is even less meaningful than usual.
I personally use the BASIC_RX with some gain/filtering up-front for
doing riometry at 38Mhz with a USRP2,
and it's easily sensitive down to -125dBm or so.
The ADC on the N210 has an SFDR of somewhere in the neighbourhood of
80dB, with saturation occurring
somewhere around +10dBm.
The N210 FPGA uses a multi-stage CIC decimator with one or two half-band
filters afterwards. The filtering
effect will depend somewhat on the decimation ratios. The out-of-band
attenuation I've found is usually on
the order of 90dB or better, but I'll let the designers chime in with
specific figures.
If you're using the BASIC_RX, it has no filtering at all, so you have to
do any analog anti-alias filtering
yourself, or filtering for the nyquist zone you wish to operate at.
The BASIC_RX has useful analog
performance up to about 250MHz, but the N210 ADC samples at 100MHz.
So you either low-pass to
50Mhz, or you bandpass to be within the Nyquist zone of interest.
--
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
Neither the BASIC_RX nor the LFRX have any gain at all, so quoting MDSis even less meaningful than usual.I personally use the BASIC_RX with some gain/filtering up-front fordoing riometry at 38Mhz with a USRP2,and it's easily sensitive down to -125dBm or so.The ADC on the N210 has an SFDR of somewhere in the neighbourhood of80dB, with saturation occurringsomewhere around +10dBm.The N210 FPGA uses a multi-stage CIC decimator with one or two half-bandfilters afterwards. The filteringeffect will depend somewhat on the decimation ratios. The out-of-bandattenuation I've found is usually onthe order of 90dB or better, but I'll let the designers chime in withspecific figures.If you're using the BASIC_RX, it has no filtering at all, so you have todo any analog anti-alias filteringyourself, or filtering for the nyquist zone you wish to operate at.The BASIC_RX has useful analogperformance up to about 250MHz, but the N210 ADC samples at 100MHz.So you either low-pass to50Mhz, or you bandpass to be within the Nyquist zone of interest.
Which USRP Is Right for You?
When choosing the right USRP device for your application, a good place to start is by asking yourself a few questions related to signal parameters, size, weight, power, cost (SWaP-C), performance, and environmental application requirements. Question one: What center frequency and bandwidth do I require?
This question is easy enough to answer, but the next one is more involved: How do I plan to move signal data on or off the device?
This brings into focus the importance of data interfaces. For example, the USRP-290x&#;models are connected to the host through USB and are limited by the maximum sustained bandwidth of that interface, whereas the&#;Ettus USRP X440 is equipped with two 100 GbE interfaces capable of moving much more data.
To learn more about USRP interface bandwidth considerations, read about USRP Bandwidths and Sampling Rates on the Ettus Research knowledge base.
Most USRP devices have a maximum frequency up to 6 GHz and some higher; however, the NI Ettus USRP X410 can operate in the 7 GHz band. On the lower frequency end, some radios go down to 75 MHz and some as low as DC depending on the analog chipset used. See Figure 16 for a breakdown of each model.
Figure 3: The Ettus USRP X410, built on an RFSoC, is a high-frequency wideband SDR with a center frequency up to 7.2 GHz
Cost and Performance Trade-offs
There are trade-offs to consider when choosing a USRP device, specifically cost versus performance. If you require a radio at a great value and you do not have advanced FPGA or wide bandwidth requirements, the NI USRP 290x or Ettus Research B200mini are great options. If you need the widest bandwidth and frequencies up to 7.2 GHz, the NI Ettus USRP X410 may be the best fit. There are many options available in between these two examples. Figure 15 below gives a full break down across all models.
Figure 4: USRP B200 and USRP B200mini Low SWaP-C SDRs
If you need frequencies up to 7.2 GHz, the NI Ettus USRP X410 may be the best fit. If you require the widest possible instantaneous bandwidth, the NI Ettus USRP X440 may meet the need. There are many options available beyond these examples; Figure 16 provides a full breakdown across all models.
Figure 5: The Ettus USRP X440 offers up to 1.6 GHz bandwidth per channel, with a direct sampling transceiver architecture
Stand-Alone or Host-Connected SDR Options
The USRP was conceived as a computer peripheral to connect software to the electromagnetic spectrum. Applications have evolved since the first USRPs, and many require an embedded processor onboard. You may require this stand-alone configuration if your application has the SDR physically distributed from a centralized control system or deployed on its own. If stand-alone is a key requirement, you will need to decide if a Xilinx Zynq&#; Multiprocessor System on Chip (MPSoC) or RF System On Chip (RFSoC) is sufficient or if you require a powerful Intel X86 processor onboard. Table 1 provides a breakdown of various models and their onboard processors; consult USRP specification documents for more details.
Radio ModelOnboard ProcessorUSRP N320, USRP N321, USRP N310Xilinx Zynq MPSOCUSRP E31XXilinx Zynq MPSOCUSRP E320Xilinx Zynq MPSOCNI Ettus USRP X410, USRP X440Xilinx Zynq Ultrascale+ RFSOC ZU28DRUSRP Intel Core i7 EQ (2 GHz Quad Core)
Table 1: Stand-Alone Capable USRP Models with Onboard Processors
Figure 6: USRP Stand-Alone SDR with Built-in Intel Core i7
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If you want to learn more, please visit our website Highmesh.
Ruggedization and Harsh Environments
Although many USRPs are used in the lab, some applications require operation in outdoors or in harsher environments. If your application requires extended operating temperatures or can&#;t rely on air-cooling, you may want to consider the Ettus Research branded Embedded Series for your application. Additionally, under the Ettus Research brand, there are options to configure the USRP B205mini for extended temperature range with the use of the industrial grade aluminum enclosure assembly for low SWaP operation. Alternatively, if you have extreme environmental requirements, we would love to connect you with our experienced ruggedization partners; contact us to explore these options.
Figure 7: Embedded Series, USRP E320
Multichannel Synchronization
Many applications require multiple input and multiple output (MIMO) configurations with varying levels of synchronization. Some MIMO systems simply require a shared clock for ADCs and DACs, while others require every channel to be locked to a common clock and local oscillator for a full phase coherent operation.
A common MIMO application is for communications with spatial multiplexing. As this only requires clock synchronization, most USRPs with an external 10 MHz reference clock will be sufficient. An example of such a system was built by The University of Bristol and Lund University when they broke the wireless spectral efficiency world record using an SDR-based massive MIMO system. The system used in this application is composed of NI USRP Software Defined Radio Devices with onboard FPGAs.
Figure 8: USRP N320 and N321 with Built-In LO Distribution Interfaces
When a full phase coherent operation is required, you have a few options to consider. If you require up to four channels of receive only operation, the Ettus Research USRP X310 with two TwinRx daughterboards can be set up to share the LO and operate in a phase coherent manner. If more than four channels are required, then consider the Ettus Research USRP N320 and N321 (shown in Figure 8) or the NI Ettus USRP X440. Since the USRP X440 is built with a direct-sampling intermediate frequency (IF) architecture, synchronization can be achieved by sharing sample clocks across up to eight transmit and eight receive channels. It is prepared for multidevice synchronization to an externally provided reference clock signal.
The USRP N321 comes equipped with built-in LO distribution hardware allowing for up to&#;128 x 128 phase coherent operation: a 32 x 32 configuration example is shown in Figure 9.
Figure 9: USRP N320 and N321 Multichannel Phase Coherent System
Distributed Multi-Radio Synchronization
In some applications, radios require synchronization but are not co-located. In these instances, a full phase coherent operation is a challenge; however, one can use GPS-based synchronization to get frequency and phase stability with a GPS disciplined oscillator (GPSDO). Many USRP models are equipped with a GPSDO from the factory. To learn more, read &#;Global Synchronization and Clock Disciplining with NI USRP-293x Software Defined Radio.&#;
Figure 10: USRP X310 with Onboard GPS Disciplined Oscillator
Inline Signal Processing and FPGA Considerations
Some applications have processing requirements that are best suited for an onboard FPGA. These applications often have wide signal bandwidths or low/deterministic latency requirements. In these cases, picking a radio with the ability to program the FPGA is important. Many of the USB and lower-cost USRP models, such as the USRP B200mini or the N210, are built with smaller FPGA devices and as such do not have the space to add user code. Many of the higher end radios come equipped with Kintex 7 class devices all the way up to the state-of-the-art Ettus USRP X410 and X440 with the Xilinx Zynq UltraScale+ RFSoC. Devices built on Xilinx Zynq include additional cores such as onboard soft-decision forward error correction (SD-FEC), multi-Arm processors, and built-in ADCs and DACs.
USRP ModelOnboard FPGAUSRP N320, USRP N321, USRP N310Xilinx Zynq MPSOCUSRP E31XXilinx Zynq MPSOCUSRP E320Xilinx Zynq MPSOCEttus USRP X410, USRP X440Xilinx Zynq Ultrascale+ RFSOC ZU28DRUSRP , USRP X310Xilinx Kintex 7 410T
Table 2: Comparison of FPGA Enabled USRPs
Figure 11: Comparison of FPGA Resources across NI FPGA Products
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