Transcript
Beam-Forming Array Antenna Range Measurement Specifications Measurements of the field patterns of the beam-forming array prototypes and final receiver will require a significant enhancement of the Green Bank outdoor antenna range capabilities and automation. The goal is to measure the amplitude and phase patterns of all elements in an array of up to 37 elements, at 20 frequencies, in both co- and cross-polarization, in one planar slice through the field pattern within one day. Data need to be monitored in real time to be sure that the measurement system is working well, but most heavy duty data analysis can be done off-line. The current outdoor antenna range controls the transmitting frequency synthesizer but not the turret rotator. The present receiver is manually tuned and measures phase and amplitude for a single channel with a second input channel for phase reference. The turret readout and receiver phase and amplitude are digitized for storage in machine-readable form. Very little data display or analysis software is available. Instrument and turret control and data monitoring for the upgraded antenna range should be implemented in the most expedient fashion. This could be based on something like LabView or wholly or partially implemented as a home-grown system. It probably makes sense to write the data analysis software in the glish/Aips++ environment since the same concepts and some of the same techniques will apply to beam-forming array receiver calibration and data reduction. This glish/Aips++ software might also serve a near-real-time data monitoring function. Immediate access to the data from the Unix/Linux environment on the local network is desirable.
Figure 1. Antenna range configuration for beam-forming array measurements
The array element pattern measurement specs are as follows: Simultaneous array outputs: Frequency range: Frequency resolution: Frequency stability: Transmitted polarization: Dynamic range: Amplitude accuracy:
Phase accuracy relative to phase reference antenna: Phase/Amplitude readout interval: Azimuth scan range: Azimuthal turret position accuracy: Perpendicularity of array axis to turret rotation axis: Lateral motion of array on turret platform: Physical indexing off array to turret rotation axis: Manual rotation of array around its axis: Accuracy of rotation of array around its axis: Array backplane diameter:
38 (37 elements, one polarization or 19 elements, both polarizations, receive only) 1.2 to 1.8 GHz #1 MHz Consistent with phase accuracy specified below Linear, any orientation under automated control > 40 dB below peak response of one element < 0.2 dB to 20 dB below peak response < 0.3 dB to 30 dB below peak response < 0.5 dB dB to 40 dB below peak response < 1 degree to 20 dB below peak response < 2 degrees to 30 dB below peak response < 4 degrees to 40 dB below peak response #0.5 degrees azimuth ±110 degrees from face-on to transmitting antenna 0.5 degrees
0.5 degrees not required ±5 mm 90 degrees 0.5 degrees #1.6 meters
Measurement automation and user interface requirements: Automated functions: Transmitted frequency Transmitting antenna polarization orientation Turret rotation (start, stop, rate) Any necessary receiver tuning and setup Data acquisition control and storage User interface: GUI panel for control of all automated functions Method for programming a set of measurements, e.g., set frequency, execute turret scan, save data, return turret to start, change transmitted polarization, execute turret scan, save data, return turret to start, change transmitted polarization, set frequency, etc. Data format: For local use only One file per turret scan ASCII header with measurement parameters Binary data table of typically 400 groups of 38 phases and amplitudes at 0.5-degree azimuth sample intervals. Azimuth scan limits and sampling interval can vary.
