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diff --git a/host/docs/twinrx.dox b/host/docs/twinrx.dox new file mode 100644 index 000000000..c85b78b4c --- /dev/null +++ b/host/docs/twinrx.dox @@ -0,0 +1,73 @@ +/*! \page page_twinrx TwinRX Daughterboard + +\tableofcontents + +\section twinrx_dboards TwinRX Properties + + +The TwinRX is a two-channel superheterodyne receiver designed for high performance spectrum monitoring and direction +finding applications. The receiver is tunable from 10 MHz - 6 GHz and has 80 MHz of instantaneous bandwidth per +channel, providing the versatility necessary to analyze a variety of signals in multiple bands of interest. Each +channel has an independent RF signal chain with preamplifiers, preselectors, and two mixer stages for superior +selectivity. Users can tune the two channels independently to simultaneously monitor uplink and downlink +communication with a combined bandwidth of 160 MHz. The ability to share the LO between channels across multiple +daughterboards enables the phase-aligned operation required to implement scalable multi-channel phased-arrays. +The receiver is capable of fast frequency hopping to detect frequency agile emitters. + +\image html TwinRX_Block_Diagram.png "TwinRX Block Diagram" + +\subsection twinrx_frequency_bands Frequency Bands + +The receive filter banks uses switches to select between the available filters. These paths are also dependent on the +antenna switch settings. Incorrectly setting the switches generally results in attenuated input / output power. Receive +filters are band pass (series high & low pass filters). + +Source code related to controlling the filter band and antenna switches resides in twinrx_experts.cpp. Specifically, +refer to the `twinrx::twinrx_freq_path_expert` class. Generally, these methods set the switches depending on the state +of the receive streams. + +The following sections provide switch setting tables for antenna and filter selection for frontend's receive paths. For +further details refer to the schematics. + +| Band | Range | +|--------|---------------| +| LB1 | 10 - 500 MHz | +| LB2 | 500 - 800 MHz | +| LB3 | 800 - 1.2 GHz | +| LB4 | 1.2 - 1.8 GHz | +| HB1 | 1.8 - 3.0 GHz | +| HB2 | 3.0 - 4.1 GHz | +| HB3 | 4.1 - 5.1 GHz | +| HB4 | 5.1 - 6.0 GHz | + +\subsection twinrx_lo_sharing Local Oscillator Sharing + +The TwinRX has the ability to export the two Local Oscillator (LO) signals from one channel to the companion channel +on the same daughterboard and/or to one or more other TwinRXs in order to form a phase-synchronous multi-channel +receiver. + +| Connector | Description | Min | Nominal | Damage | +|-------------|--------------|----------|-----------|--------------| +| J1 | LO2 Export | 0 dBm | 3 dBm | NA (Output) | +| J2 | LO2 Input | 0 dBm | 2 dBm | 20 dBm | +| J3 | LO1 Export | -12 dBm | 5 dBm | NA (Output) | +| J4 | LO1 Input | -10 dBm | -5 dBm | 10 dBm | + +\subsection twinrx_antenna_routing Antenna Routing + +The TwinRX has two external antenna connectors (RX1 and RX2) which can be switched internally to either +receiver channel. By default RX1 is connected to the first channel and RX2 to the second. + +When routing the antennas in any configuration other than the default there are some behavioral changes to be aware of. +As can be seen in the block diagram above the signal path from each antenna can be switched into a resistive divider +and then to either or both of the receive channels. If the divider is in use the incoming signal will be slightly +attenuated when compared to the direct passthrough. If both receive channels are configured to use the same antenna +the first two amplifiers and are a variable attenuator are shared. The effect of this is that the first channel's gain +settings for those amplifiers will override the second channel's. If both channels are tuned to the same frequency band +and at similar gain settings the effect will be minimal, but if the frequency or gain difference is large the resulting +gain on the second channel could be significantly lower or higher than expected. Additionally the signal path length +will increase in comparison to the direct antenna mapping so the phase of the received signal will be different +depending on the antenna mapping. + +*/ +// vim:ft=doxygen: |