FrontX: Difference between revisions
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==Technical Overview== | ==Technical Overview== | ||
===Block Diagram=== | ===Block Diagram=== | ||
[[Image:front_blk_diagram.png|center| | [[Image:front_blk_diagram.png|center|700px]] | ||
The radar block diagram is shown above. Most of the radar electronics is housed in the Antenna-Mounted Electronics Enclosure, including the digital exciter/receiver (DXR) and the radar interface module. The interface module allows the DXR to control the phased array antenna according to pre-programmed scanning patterns. The output data from the DXR passes through a fiber-optic rotary joint to the compute server for further processing into meteorological moment data. Processed data is archived locally to a data storage module and can be periodically downloaded by end-users. | The radar block diagram is shown above. Most of the radar electronics is housed in the Antenna-Mounted Electronics Enclosure, including the digital exciter/receiver (DXR) and the radar interface module. The interface module allows the DXR to control the phased array antenna according to pre-programmed scanning patterns. The output data from the DXR passes through a fiber-optic rotary joint to the compute server for further processing into meteorological moment data. Processed data is archived locally to a data storage module and can be periodically downloaded by end-users. | ||
Revision as of 08:33, 2 February 2024
| Deployment Type | Trailer-mounted |
|---|---|
| Frequency | 9.41 GHz (X-band) |
| Operating Modes | ATSR, Single-Polarization |
| Range Resolution | 30-150m |
| Typical Range | 60 km |
| Antenna | 1m (1.5x2.6°) |
| Transmitter | 64 T/R modules (70W) |
| Receiver | CSU DXR |
Front-X is an X-band dual-polarization phased array radar demonstrator radar. The objective of this radar system is to demonstrate dual-polarization capability and to study the limits of phased array antennas on polarization measurements. The radar is a test-bed to validate new radar waveforms, pulsing schemes, signal processing algorithms and scanning strategies that take advantage of electronic beam steering.
The radar consists of an X-band dual-polarization active phased array antenna that generates a fixed beam in one axis and can scan electronically in the other axis. The antenna array is composed of 64 radiating elements, each driving a patch array antenna that develops a fixed pattern 2.6° wide. Beam width is 1.5°x2.6°, with over 90° electronic scan range. Transmit peak power is 70 W, with a duty cycle up to 33%. Antenna polarization is switched between horizontal and vertical on an alternating basis. The antenna instantaneous bandwidth is 30 MHz tunable over the 9.21 – 9.61 GHz frequency range.
Technical Overview
Block Diagram
The radar block diagram is shown above. Most of the radar electronics is housed in the Antenna-Mounted Electronics Enclosure, including the digital exciter/receiver (DXR) and the radar interface module. The interface module allows the DXR to control the phased array antenna according to pre-programmed scanning patterns. The output data from the DXR passes through a fiber-optic rotary joint to the compute server for further processing into meteorological moment data. Processed data is archived locally to a data storage module and can be periodically downloaded by end-users.
The antenna array panel contains the transmit signal up-converter from IF to X-band, as well as the downconverter from X-band to IF. It also contains the beam steering computer that computes the phase shifts and attenuations applied to each element. A serial port allows the DXR host computer to program a beam steering sequence, which the beam steering computer steps through each time it receives a transmit trigger. An additional trigger signal controls the polarization switch within each array element. The serial port also sends status and health messages to the DXR host computer.
Phased Array Antenna
The phased array antenna consists of a linear array of 64 elements, each driven by a T/R module. The array element is a linear patch array, with a fixed pattern 2.6° wide. The beam steering logic built into the array commands the attenuators and phase shifters to form and steer a beam 1.5° wide. The dual polarization capability of the antenna allows the study of the polarization isolation requirements of the antenna, by measuring the effects of limited isolation when steered off boresight, and comparing it to measurements of the same target when mechanically steered. The characteristics of the phased array are given below.
| Parameter | Min | Typ | Max | Units |
|---|---|---|---|---|
| Center Frequency | 9.41 | GHz | ||
| Antenna Instantaneous Bandwidth | 400 | MHz | ||
| Integrated Cross Polarization Ratio | -20 | dB | ||
| Peak cross polarization ratio | -30 | dB | ||
| Beamwidth (fixed axis) | 2.6 | degrees | ||
| Beamwidth (scanning axis) | 1.5 | degrees | ||
| Beam matching between polarizations | 5 | % | ||
| Sidelobe level (fixed axis) | -25 | -22 | dB | |
| Sidelobe level (scanning axis) | -22 | dB | ||
| Overall noise figure | 7 | 9 | dB | |
| Pulse width | 50 | μs | ||
| Pulse width | 33 | % |
T/R module
The block diagram of each T/R module in the phased array is shown above. Each T/R module can output a minimum of 30.5 dBm at 9.41 GHz. On receive, the LNA has a noise figure of 5 dB, with a -35 dBm compression point. The elements offer a 30 dB isolation between transmit and receive, and 33 dB isolation between H and V polarization. Note that the output goes through a polarization selection switch that determines the transmit and receive polarization of the antenna. The switching is accomplished in < 1 μs.
The T/R module uses a common-leg architecture, so the same phase shifter and attenuator is used on both transmit and receive paths. Both the phase shifter and step attenuator offer 6 bits resolution. The phase shifter achieves an RMS phase error of 3.5°.
