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This enables the power calbration API for X300 and X310. The uhd_power_cal.py script will be able to create calibration files for X300 series USRPs. The multi_usrp calls *_power_reference will be functional, assuming there is calibration data available for the given system.
133 lines
6.8 KiB
Text
133 lines
6.8 KiB
Text
/*! \page page_twinrx TwinRX Daughterboard
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\tableofcontents
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\section twinrx_dboards TwinRX Properties
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The TwinRX is a two-channel superheterodyne receiver designed for high performance spectrum monitoring and direction
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finding applications. The receiver is tunable from 10 MHz - 6 GHz and has 80 MHz of instantaneous bandwidth per
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channel, providing the versatility necessary to analyze a variety of signals in multiple bands of interest. Each
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channel has an independent RF signal chain with preamplifiers, preselectors, and two mixer stages for superior
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selectivity. Users can tune the two channels independently to simultaneously monitor uplink and downlink
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communication with a combined bandwidth of 160 MHz. The ability to share the LO between channels across multiple
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daughterboards enables the phase-aligned operation required to implement scalable multi-channel phased-arrays.
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The receiver is capable of fast frequency hopping to detect frequency agile emitters.
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The TwinRX daughterboard only works with the X300/X310 series of USRPs.
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\subsection twinrx_dboards_mcr Master Clock Rate, Tick Rate, and Sampling Rate
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Due to the specific configuration of the analog filters, the TwinRX only
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supports a master clock rate of 200 MHz. Since the X300/X310 only has a single
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master clock, this means that the only valid tick rate for the X300/X310 is
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200 MHz, even if there is another daughterboard in the same device which could
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support a different tick rate.
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The maximum supported sample rate is 200 Msps if using one channel and
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100 Msps if using both channels. TwinRX only supports instantaneous
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bandwidth up to 80 MHz, so a sample rate of 100 Msps or less is sufficient
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for all applications. Decimation from the 200 Msps tick rate to the desired
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sample rate is handled automatically when using the default FPGA images
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either by setting the sample rate (if using the multi_usrp API) or by
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setting the output rate of the DDC (if using the RFNoC API).
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IMPORTANT NOTE: If building a custom RFNoC image and using both channels
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of the TwinRX, the 400 Msps produced by the Radio block (2 channels at
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200 Msps each) exceeds the 200 Msps throughput capacity of the crossbar
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in the RFNoC framework. To resolve this, a block that consumes the 400 Msps
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and produces less than 200 Msps must be statically connected to the Radio
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block. The default X300 and X310 FPGA images have a DDC block statically
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connected to the Radio block which handles the decimation automatically by
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setting the output rate on each channel of the DDC to 100 Msps or less.
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It is recommended to leave the DDC statically connected to the Radio for
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custom RFNoC FPGA images, but the DDC can be replaced by a custom block
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as long as it consumes the 400 Msps and produces an aggregate of less than
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200 Msps.
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\image html TwinRX_Block_Diagram.png "TwinRX Block Diagram"
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\subsection twinrx_frequency_bands Frequency Bands
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The receive filter banks uses switches to select between the available filters. These paths are also dependent on the
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antenna switch settings. Incorrectly setting the switches generally results in attenuated input / output power. Receive
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filters are band pass (series high & low pass filters).
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Source code related to controlling the filter band and antenna switches resides in twinrx_experts.cpp. Specifically,
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refer to the `twinrx::twinrx_freq_path_expert` class. Generally, these methods set the switches depending on the state
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of the receive streams.
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The following sections provide switch setting tables for antenna and filter selection for frontend's receive paths. For
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further details refer to the schematics.
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| Band | Range |
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|--------|---------------|
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| LB1 | 10 - 500 MHz |
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| LB2 | 500 - 800 MHz |
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| LB3 | 800 - 1.2 GHz |
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| LB4 | 1.2 - 1.8 GHz |
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| HB1 | 1.8 - 3.0 GHz |
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| HB2 | 3.0 - 4.1 GHz |
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| HB3 | 4.1 - 5.1 GHz |
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| HB4 | 5.1 - 6.0 GHz |
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\subsection twinrx_lo_sharing Local Oscillator Sharing
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The TwinRX has the ability to export the two Local Oscillator (LO) signals from one channel to the companion channel
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on the same daughterboard and/or to one or more other TwinRXs in order to form a phase-synchronous multi-channel
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receiver.
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| Connector | Description | Min | Nominal | Damage |
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|-------------|--------------|----------|-----------|--------------|
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| J1 | LO2 Export | 0 dBm | 3 dBm | NA (Output) |
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| J2 | LO2 Input | 0 dBm | 2 dBm | 20 dBm |
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| J3 | LO1 Export | -12 dBm | 5 dBm | NA (Output) |
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| J4 | LO1 Input | -10 dBm | -5 dBm | 10 dBm |
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\subsection twinrx_antenna_routing Antenna Routing
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The TwinRX has two external antenna connectors (RX1 and RX2) which can be switched internally to either
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receiver channel. By default RX1 is connected to the first channel and RX2 to the second.
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When routing the antennas in any configuration other than the default there are some behavioral changes to be aware of.
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As can be seen in the block diagram above the signal path from each antenna can be switched into a resistive divider
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and then to either or both of the receive channels. If the divider is in use the incoming signal will be slightly
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attenuated when compared to the direct passthrough. If both receive channels are configured to use the same antenna
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the first two amplifiers and are a variable attenuator are shared. The effect of this is that the first channel's gain
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settings for those amplifiers will override the second channel's. If both channels are tuned to the same frequency band
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and at similar gain settings the effect will be minimal, but if the frequency or gain difference is large the resulting
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gain on the second channel could be significantly lower or higher than expected. Additionally the signal path length
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will increase in comparison to the direct antenna mapping so the phase of the received signal will be different
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depending on the antenna mapping.
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\subsection twinrx_power_cal Power Calibration
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The X300/X310 motherboards support power-calibrating the daughterboards, and
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therefore TwinRX can also make use of this calibration API (see also \ref page_power).
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However, unlike other daughterboards, the relationship between actual, received
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power, and power measured at the ADC depend on more parameters than with the
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other daughterboards. First of all, the TwinRX has two complete analog receiver
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chains, unlike all the other daughterboards. Both receiver chains can be connected
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to any RF input, which already increases the number of combinations that need to
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be calibrated. Furthermore, the RF paths inside the daughterboard have an
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optional switch, which allows both receivers to receive from the same input, at
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different frequencies.
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single chan
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x3xx_power_cal_rx_rx1 + serial:{0, 1}
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x3xx_power_cal_rx_rx2 + serial:{0, 1}
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dual chan
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x3xx_power_cal_rx_rx1 + serial:{00, 11}
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x3xx_power_cal_rx_rx2 + serial:{00, 11}
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*/
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// vim:ft=doxygen:
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