RVP8 User’s Manual March 2006 1. Introduction and Specifications Introduction and Specifications The RVP8 Lineage SIGMET Inc. has a 20-year history of supplying innovative, high-quality signal processing products to the weather radar community. The history of SIGMET products reads like a history of weather radar signal processing: Year Model Units Sold 1981 FFT 10 First commercial FFT-based Doppler signal processor for weather radar applications.
RVP8 User’s Manual March 2006 Introduction and Specifications Open Hardware and Software Design Compared to previous processors that were built around proprietary DSP chips, perhaps the most innovative aspect of the RVP8 is that it is implemented on standard PC hardware and software that can be purchased from a wide variety of sources. The Intel Pentium/PCI approach promises continued improvement in processor speed, bus bandwidth and the availability of low–cost compatible hardware and peripherals.
RVP8 User’s Manual March 2006 Introduction and Specifications Standard LAN Interconnection for Data Transfer or Parallel Processing For communication with the outside world, the RVP8 supports as standard a 10/100/1000 Base T Ethernet. For most applications, the 100 BaseT Ethernet is used to transfer moment results (Z, T, V, W) to the applications host computer (e.g., a product generator).
RVP8 User’s Manual March 2006 1.1 Introduction and Specifications System Configuration Concepts The hardware building blocks of an RVP8 system are actually quite few in number: S RVP8/IFDt IF Digitizer Unit- This is a separate sealed unit usually mounted in the receiver cabinet. The primary input to the IFD is the received IF signal.
RVP8 User’s Manual March 2006 Introduction and Specifications RVP8 Configuration Example: Basic Magnetron System Optional Digital STALO DAFC Triggers IF Signal IF Magnetron Burst IFD COAX Uplink Fiber Downlink RVP8/Rx ËËËËË ËËËËË ËËËËË 14-Bit SBC RS232C Antenna Angles 10/100 BaseT LAN Interface Mouse Utilities Monitor Keyboard S IFD- IF Digitizer installed in the radar receiver cabinet. This can be located up to 100 meters from the RVP8 main chassis (fiber optic connection).
RVP8 User’s Manual March 2006 Introduction and Specifications RVP8 Configuration Example: High Performance Klystron IF Signal Reference Clock IF Tx Waveform IFD 14-Bit RVP8/Rx COAX Uplink Fiber Downlink Digitally Synthesized COHO IF Tx Waveform Pulse width Triggers Parallel or Synchro AZ Connector Panel Parallell or Synchro EL 10/100/1000 Base T Mouse Utilities Monitor ËËËË I/OĆ62 ËËËË SBC ËËËË ËËËË RVP8/Tx Keyboard S RVP8/Tx- The digital transmitter card provides the digital Tx waveform.
RVP8 User’s Manual March 2006 Introduction and Specifications RVP8 Configuration Example: Dual Polarization Magnetron System Optional Digital STALO Horizontal IF Signal DAFC IFD COAX Uplink 14-Bit IF Magnetron Burst Horz Fiber Downlink Synch Clock COAX Uplink IFD 14-Bit Vertical IF Signal Fiber Downlink Vert Polarization Control Pulse Width Control Triggers Connector Panel Parallel or Synchro AZ Parallell or Synchro EL RVP8/Rx ËËËË I/OĆ62 ËËËË SBC ËËËË ËËËË RVP8/Rx 10/100/1000 BaseT LAN
RVP8 User’s Manual March 2006 Introduction and Specifications COTS Accessories Aside from the basic PCI cards required for the radar application, there are additional cards that can be installed to meet different customer requirements, e.g., S 10/100–BaseT Ethernet card for additional network I/O (e.g., a backup network). S RS-232/RS-422 serial cards for serial angles, remote TTY control, etc. S Sound card to synthesize audio waveforms for wind profiler applications. S GPS card for time synch.
RVP8 User’s Manual March 2006 1.1.1 Introduction and Specifications IFD IF Digitizer The IFD 14-bit IF digitizer is a totally sealed unit for optimum low-noise performance. The use of digital components within the IFD is minimized and the unit is carefully grounded and shielded to make the cleanest possible digital capture of the input IF signal. Because of this, the IFD achieves the theoretical minimum noise level for the A/D convertors. There are 4 inputs to the IFD: S IF video signal.
RVP8 User’s Manual March 2006 1.1.2 Introduction and Specifications Digital Receiver PCI Card (RVP8/Rx) The RVP8/Rx card receives the digitized IF samples from the IFD via the fiber optic link. The advantage of this design is that the receiver electronics (LNA, RF mixer, IF preamp, and IFD) can be located as far as 100–meters away from the RVP8 main chassis. This makes it possible to choose optimum locations for both the IFD and the RVP8, e.g.
RVP8 User’s Manual March 2006 Introduction and Specifications Calibration Plot for RVP8/IFD The figure above shows a calibration plot for a 14-bit IFD with the digital filter matched to a 2 microsecond pulse. The performance in this case is >100 dB dynamic range. The RVP8 performs several real time signal corrections to the I/Q samples from the Rx, including: Amplitude Correction- A running average of the transmit pulse power in the magnetron burst channel is computed in real-time by the RVP8/Rx.
RVP8 User’s Manual March 2006 Introduction and Specifications Digital IF Band Pass Design Tool The built–in filter design tool makes it easy for anyone to design the optimal IF filter to match each pulse width and application. Simply specify the impulse response and pass band and the filter appears. The user interface makes it easy to widen/narrow the filter with simple keyboard commands. There is even a command to automatically search for an optimal filter.
RVP8 User’s Manual March 2006 1.1.3 Introduction and Specifications Mother Board or Single-Board Computer (SBC) The dual-CPU Pentium mother board or single-board computer (SBC) acts as the host to the Linux operating system and provides all of the compute resources for processing the I/Q values that are generated by the RVP8/Rx card. Standard keyboard, mouse and monitor connections are on the Rx backpanel, along with a 10/100/1000 BaseT Ethernet port.
RVP8 User’s Manual March 2006 Introduction and Specifications be precise or repeatable. In contrast, the RVP8/Tx can perform precise phase modulation to any desired angle, without requiring the use of external phase shifting hardware. S Pulse Compression- There is increasing demand for siting radars in urban areas that also happen to have strict regulations on transmit emissions.
RVP8 User’s Manual March 2006 1.1.5 Introduction and Specifications I/O-62 PCI Card and I/O Panel The SIGMET I/O-62 is a short format PCI card that provides extensive I/O capabilities for the RVP8. A typical installation would have one I/O-62 and an RVP8 Connector Panel shown above. The Softplanet is used to interconnect the I/O 62 with other SIGMET PCI cards. Note that the identical card is used in the SIGMET RCP8 radar/antenna control processor which in general does not use the Softplanet connection.
RVP8 User’s Manual March 2006 Introduction and Specifications Run Time FPGA Configuration The SIGMET I/O-62 card is built around a 100K–Gate FPGA which, in addition to driving the I/O signals on the 62-position connector, also coordinates the PCI and Softplanet traffic. These chips are SRAM–based, meaning that they are configured at run time. This allows the FPGA code to be automatically upgraded during each RVP8 code release without needing to physically reprogram any parts.
RVP8 User’s Manual March 2006 Introduction and Specifications 1.2 Comparison of Analog vs Digital Radar Receivers 1.2.1 What is a Digital IF Receiver? A digital IF receiver accepts the analog IF signal (typically 30 MHz), processes it and outputs a stream of wide dynamic range digital “I” and “Q” values. These quantities are then processed to obtain the moment data (e.g., Z, V, W or polarization variables).
RVP8 User’s Manual March 2006 1.2.2 Introduction and Specifications Magnetron Receiver Example A typical analog receiver for a magnetron system is shown in the top portion of Figure 1–1. The received RF signal from the LNA is first mixed with the STALO (RF–IF) and the resulting IF signal is applied to one of several bandpass filters that match the width of the transmitted pulse. The filter selection is usually done with relays. The narrow band waveform is then split.
RVP8 User’s Manual March 2006 Introduction and Specifications Figure 1–1: Analog vs Digital Receiver for Magnetron Systems Classic Analog Receiver for Magnetron IF Filters Matched to Pulse Widths BPF LOG Analog RF From LNA Analog IF BPF X Split LOG BPF Digital Atten BPF Split STALO Quad Phase Detector AFC Signal Linear Amp Q Control Bits From IAGC Logic Line Drivers Phase Locked IF AFC RF Tx Burst IF Tx Sample Split X I IAGC COHO Low Q Locking COHO RVP8 Magnetron Interface Analog
RVP8 User’s Manual March 2006 1.2.3 Introduction and Specifications Klystron or TWT Receiver and Transmit RF Example A typical analog receiver for a klystron system is shown in the top portion of Figure 1–2. The arrangement of components is similar to the magnetron case, except that the COHO operates at a fixed phase and frequency, a phase shifter is included for 2nd trip echo filtering and there is no AFC feedback required.
RVP8 User’s Manual March 2006 Introduction and Specifications 1.3 RVP8 IF Signal Processing 1.3.1 IFD Data Capture and Timing The RVP8 design concept is to perform very little signal processing within the IFD digitizer module itself. This is to minimize the presence of digital components that might interfere with the clean capture of the IF signals.
RVP8 User’s Manual March 2006 1.3.2 Introduction and Specifications Burst Pulse Analysis for Amplitude/Frequency/Phase The burst pulse analysis provides the amplitude, frequency and phase of the transmitted pulse. The phase measurement is analogous to the COHO locking that is performed by a traditional magnetron radar. The difference is that the phase is known in the digital technique, so that range dealiasing using the phase modulation techniques is possible.
RVP8 User’s Manual March 2006 1.3.
RVP8 User’s Manual March 2006 Introduction and Specifications S Computation of “I” and “Q” quadrature values (also performed during the band pass filtering step). S Transmit burst sample frequency, phase and amplitude calculation S I and Q phase and amplitude correction based on transmit burst sample. S Interference rejection algorithm. S AFC frequency error calculation with output to IFD for digital or analog control of STALO (for magnetron systems).
RVP8 User’s Manual March 2006 1.4 Introduction and Specifications RVP8 Weather Signal Processing The processing of weather signals by the RVP8 is based on the algorithms used in the previous generation RVP7 and RVP6. However, the performance of the RVP8 allows a different approach to some of the processing algorithms, especially the frequency domain spectrum processing. All of the algorithms start with the wide dynamic range I and Q samples that are obtained from the Rx card over the PCI bus.
RVP8 User’s Manual March 2006 1.4.1 Introduction and Specifications General Processing features Figure 1–4 shows a block diagram of the processing steps. These are discussed below. Autocorrelations The autocorrelations R0, R1 and R2 are produced by all three processing modes. However, the way that they are produced is different for the three modes, particularly with regard to the filtering that is performed. S Pulse Pair Mode — Filtering for clutter is performed in the time domain.
RVP8 User’s Manual March 2006 Introduction and Specifications Time (azimuth) Averaging The autocorrelations are based on input “I” and “Q” values over a selectable number of pulses between 8, 9, 10, ...,256. Any integer number of pulses in this interval may be used including DFT/FFT and random phase modes. Selectable angle synchronization using the input AZ and EL tag lines assures that all possible pulses are used during averaging for each, say, 1 degree interval.
RVP8 User’s Manual March 2006 Introduction and Specifications Thresholding The RVP8 calculates several parameters that are used to threshold (discard) bins with weak or corrupted signals. The thresholding parameters are: S Signal quality index (SQI=|R1|/R0) S LOG (or incoherent) signal-to-noise ratio (LOG) S SIG (coherent) signal-to-noise ratio S CCOR clutter correction These parameters are computed for each range bin and can be applied in AND/OR logical expressions independently for dBZ, V and W.
RVP8 User’s Manual March 2006 Introduction and Specifications PRF1 PRF2 Unambiguous Range (km) 3 cm 5 cm 10 cm 500 375 300 11.25 18.75 37.50 1000 750 150 22.50 37.50 75.00 2000 1500 75 45.00 75.00 150.00 500 400 300 15.00 25.00 50.00 1000 800 150 30.00 15.00 100.00 2000 1600 75 60.00 100.00 200.00 1.4.
RVP8 User’s Manual March 2006 1.4.4 Introduction and Specifications Random Phase Processing for 2nd Trip Echo Second trip echoes can be a serious problem for applications that require operation at a high PRF. Second trip echoes can appear separately or can be overlaid on first trip echoes (second trip obscuration).
RVP8 User’s Manual March 2006 Introduction and Specifications 1.5 RVP8 Control and Maintenance Features 1.5.1 Radar Control Functions The RVP8 also performs several important radar control functions: S Trigger generation- up to 6 programmable triggers. S Pulsewidth control (four states controlled by four bits). S Angle/data synchronization- to collect data at precise azimuth intervals (e.g., every 0.5, 1, 1.5 degrees) based on the AZ/EL angle inputs.
RVP8 User’s Manual March 2006 1.5.2 Introduction and Specifications Power-Up Setup Configuration The RVP8 stores on disk an extensive set of configuration information. The purpose of these data is to define the exact configuration of the RVP8 upon startup. The setup information can be accessed and modified using either a local keyboard and monitor, or over the network.
RVP8 User’s Manual March 2006 1.6 Introduction and Specifications Support Utilities and Available Application Software The RVP8 system includes a complete set of tools for the calibration, alignment and configuration of the RVP8. These includes the following utilities: S ascope- a comprehensive utility for manual signal processor control and data display of moments, times series and Doppler spectra. ascope includes a realistic signal simulator capable of producing both first and second trip targets.
RVP8 User’s Manual March 2006 1.7 Introduction and Specifications System Network Architecture The RVP8 provides considerable flexibility for network operation. This allows remote control and monitoring of the system from virtually anywhere on the network, subject to the user’s particular security restrictions. Unlike the previous generation RVP7, which used a SCSI interface, the RVP8 uses a network interface exclusively.
RVP8 User’s Manual March 2006 1.8 Introduction and Specifications Open Architecture and Published API SIGMET recognizes that certain users may require the ability to write their own signal processing algorithms which will run on the RVP8. To accommodate this, the RVP8 software is organized to allow separately compiled plug-in modules to be statically linked into the running code.
RVP8 User’s Manual March 2006 Introduction and Specifications 1.9 RVP8 Technical Specifications 1.9.1 IFD Digitizer Module, Rev E or later Input Signals S IF Received Signal: 50W, + 6.5 dBm full–scale, +20dBm absolute max S IF Burst or COHO: 50W, +6.
RVP8 User’s Manual March 2006 1.9.2 Introduction and Specifications RVP8/Rx PCI Card, Rev C or later Pulse Repetition Frequency S 50 Hz to 20 KHz +0.1%, continuously selectable. IF Band Pass Filter S Programmable Digital FIR with software selectable bandwidth. Built-in filter design software with graphical user interface. Impulse Response S Up to 3024 FIR filter taps, corresponding to 75 msec impulse response length for 72 MHz IF samples at 125 meter range resolution.
RVP8 User’s Manual March 2006 1.9.3 Introduction and Specifications RVP8/Tx PCI Card Analog Waveform Applications S Digitally synthesized IF transmit waveform for pulse compression, frequency agility, and phase modulation applications. S Master clock or COHO signal to the radar; can be phase locked or free running, arbitrary frequency. Analog Output Waveform Characteristics S Two independent, digitally synthesized, analog output waveforms (BNC).
RVP8 User’s Manual March 2006 1.9.4 Introduction and Specifications SIGMET I/O-62 PCI Card S Short format PCI card with 62-position “D” connector. Multiple cards may be installed. S Includes D/A, A/D, discrete inputs and outputs (TTL, wide range, RS422, etc.) See summary table below. S I/O pin assignment mapping by softplane.conf file. S Standard or custom remote backpanels available.
RVP8 User’s Manual March 2006 1.9.5 Introduction and Specifications I/O-62 Standard Connector Panel S Mounts on front or rear of standard 19” EIA rack S Connects to I/O-62 via 1:1 62–pin 1.8–m cable (provided). S Provides standard inputs and outputs required by most weather radars such as triggers, polarization control, pulse width control and antenna angles.
RVP8 User’s Manual March 2006 1.9.6 Introduction and Specifications RVP8 Processing Algorithms Input from Rx Board S 16–bit I/Q samples S Optional dual-channel I/Q samples (e.g., for polarization systems or dual frequency systems) IQ Signal Correction Options S Amplitude jitter correction based on running average of transmit power from burst pulse.
RVP8 User’s Manual March 2006 Introduction and Specifications S W Spectrum width, 8 or 16 bits S I/Q Time series, 16 bits each per sample S DFT Doppler Spectrum output option in DFT mode, 16 bits per component S Optional: ZDR, PHIDP, RHOHV, LDR, RHO, 8 or 16 bits Data Quality Thresholds S Signal–to–noise ratio (SNR) Used to reject bins having weak signals. Typically applied to dBZ.
RVP8 User’s Manual March 2006 1.9.7 Introduction and Specifications RVP8 Input/Output Summary Ethernet Input/Output from Host Computer S Data output of calibrated dBZ, V and W during normal operation. Full I/Q timeseries recording with a separate tsarchive utility, or through a customer’s application using a public API. Signal processor configuration and verification read–back is performed via the Ethernet interface. RS-232C Serial Data I/O S For real time display/monitoring or data remoting.
RVP8 User’s Manual March 2006 1.9.8 Introduction and Specifications Physical and Environmental Characteristics Packaging S Motherboard Configuration S Custom PC configurations available or packaged by customer. S Dimensions of standard 4U chassis 43.2 wide x 43.2 long x 17.8 cm high 17 wide x 17 long x 7.00 inch high S Dimensions IF Digitizer 2.5 wide x 10.9 long x 23.6 cm high 1 wide x 4.3 long x 9.3 inch high S Redundant Power Supplies. Three hot–swap modules with audio failure alarm.
