RXM-25 Transceiver Architecture
The RXM-25 weather radar is equipped with a feature-rich, high performance, state-of-the-art RF transceiver incorporating many unique enhancements not found in competing systems. The entirety of the transceiver is contained in a single antenna-mounted enclosure eliminating costly waveguide rotary joints and enabling simplified maintenance procedures.
Antenna Duplexer
The antenna is coupled to the transmit and receive subsystems through an efficient duplexer utilizing low-loss (<0.5 dB) ferrite circulators.
Transmitter Calibration Path
Each transmit pulse is sampled through a calibrated directional coupler for transmitter frequency estimation and power calibration.
Transmitter
An efficient magnetron-based transmitter provides 25 kW of peak transmit power. The transmit tube is excited by a high-reliability modulator consisting entirely of solid-state components. The magnetron has a useful operating life approaching 10,000 hours, as well as very low replacement cost (around 2,000 USD). Utilizing a proprietary quick-change bracket, the magnetron in an RXM-25 can be replaced by an unskilled technician in under 15 minutes.
Internal Receiver Calibration
Integrated ambient and hot reference loads enable absolute receiver power and channel-to-channel phase calibration as well as supporting built-in-self-test capabilities
Receiver Source Switch
Band-matched, low-loss front end switches allow the receiver to sample the transmit pulse, backscatter from the antenna, or either of the internal calibration sources. These switches feature fast (10 ns) switching time and very low video transients enabling viewing of the calibration sources on a pulse-to-pulse basis.
Low Noise Amplifier
Ultra-low noise figure, high linearity LNAs are employed giving the entire receiver a typical noise figure of less than 3 dB with all front-end losses included, while maintaining an excellent dynamic range of over 120 dB at 1 dB compression.
Band Pass Filter
Custom-designed cavity filters offering very low insertion loss and steep skirt selectivity attenuate out of band signals prior to downconversion.
Downconversion Mixer
Downconversion to IF is accomplished through the use of high linearity image rejection mixers. The combination of the filter and mixer allows the use of just a single downconversion stage while maintaining well over 60 dB of rejection in the lower sideband.
Phase-locked X-Band Local Oscillator
The RXM-25 is equipped with an ultra-stable phase locked dielectric resonator to generate the local downconversion oscillator. Exceptional performance is attained with an additive phase noise figure of just 3 dB over 20 log(N) and an SFDR over 80 dB. For applications in demanding RF environments the system can be equipped with an optional programmable synthesizer allowing the system IF to be tuned to avoid interferers.
Ultra-low Phase Noise Ovenized Oscillator
Utilizing a precision SC-cut ovenized crystal, the RXM-25 receiver's frequency reference exhibits a best-in-class noise figure of -174 dBc at 10 kHz. Networked radar operation is enhanced through the use of GPS discipline of this local frequency reference.
Data Acquisition
Data is acquired utilizing Ridgeline Instruments' proprietary eDAQ1b reconfigurable data acquisition system. With an instantaneous sampled bandwidth of 125 MHz, over 115 dB of dynamic range (at 100 meter gate spacing), 16384 maximum gates, Gigabit Ethernet interface, and user-friendly configuration tools, the eDAQ1b outperforms all competing solutions.