1990 Technical Papers

A Millimeter Compact Range

Authors: James D. Huff, Christopher B. Brechin
Publication: AMTA 1990
Copyright Owner: NSI-MI Technologies

The compact range mechanically collimates electro-magnetic energy, thus creating a plane wave useful for testing antennas in a far field environment. Since this collimation can be achieved in a relatively small space, the tests can be performed in an environmentally controlled chamber. With the increasing use in both military and commercial applications of antennas operating at millimeter wavelengths, there is increasing need for small compact ranges operating in the 26.5 to 100 GHz frequency range. This paper describes the development of a small compact range with a two foot diameter test zone that operates from 26.5 GHz to greater than 100 GHz.

An Overview of Parameters Determining Productivity and Sensitivity in RCS Measurement Facilities

Authors: Edward B. Hart, William G. Luehrs
Publication: AMTA 1990
Copyright Owner: NSI-MI Technologies

A major objective in the design of an RCS measurement facility is to obtain the greatest possible productivity (overall measurement efficiency) while maintaining the accuracy and sensitivity necessary for low radar cross section targets. This paper will present parameters affecting the total throughput rates of an indoor facility including instrumentation, target handling, and band changes - one of the most time consuming activities in the measurement process. Sensitivity and accuracy issues to be discussed include radar capabilities, feeds and feed clustering, compact range, background levels, and diffraction control.

High Speed Measurements of T-R Modules

Authors: John R. Jones, Curtis E. Green
Publication: AMTA 1990
Copyright Owner: NSI-MI Technologies

An s-parameter measurement system and a procedure are described for making fast s-parameter measurements on multi-state devices. A sample test problem is considered and the application of the system and the procedure to this test problem is discussed. The important features of the system are described and timing measurements of system operation are presented.

High-Speed Testing of Microwave Antennas

Authors: Joseph H. Pape
Publication: AMTA 1990
Copyright Owner: NSI-MI Technologies

State-of-the-art microwave antennas often incorporate the ability to operate in many operating states and over wide frequency ranges. Adaptive arrays and electronically scanned antennas may have programmable beam shapes, configurations or scan positions resulting in several thousand operational states. In addition, these antennas may also require testing at many frequencies. To be properly characterized, these antennas may require testing in all these states. The amount of data required to characterize these antennas, coupled with the requirement to maximize antenna range throughput and minimize costs, puts ever increasing demands on the test equipment designed to perform these measurements. This paper describes a new automated microwave measurement system utilizing a high speed measurement receiver and an 80386 PC based computer to rapidly test these new generation antennas. The recently introduced Scientific-Atlanta Model 2095 Microwave Measurement System incorporates a unique data acquisition coprocessor (DAC) for high speed test device control, instrument timing, frequency control, data buffering and transfer to the system controller. Antenna measurements on multi-beam and multi-port antennas can be made in a fraction of the time associated with other types of test systems. The various timing parameters of the Model 2095 are described with special emphasis on how these independent and variable factors inter-relate to each other. A method is presented to calculate total test time, given the test requirement and timing for state changes of the AUT. Examples of typical test scenarios are presented as a further aid in understanding system timing.

Integrated Radar Measurement System

Authors: Marvin L. Wolfenbarger
Publication: AMTA 1990
Copyright Owner: NSI-MI Technologies

This paper presents an overview of the Integrated Radar Measurement System (IRMS) installed at the Air Force Radar Target Measurement Facility (RATSCA'D for AFSC/6585 TG/RX Holloman AFB, New Mexico.

Longitudinal Translation at Selected Points a Measured Technique Revisited

Author: Doren W. Hess
Publication: AMTA 1990
Copyright Owner: NSI-MI Technologies

The extraneous signals that perturb antenna patterns can be found and identified by a method known as "longitudinal translation at selected points". The method is usually applied to certain selected angular points on the antenna pattern. With this technique the composite pattern -- consisting of the direct-path signal and the reflection signal -- is measured at a series of translation distances along the axis of the antenna range. By utilizing both the amplitude and phase of the received signal, one can remove the signal that results from stray reflection and retain the desired direct path signal. The result is an improved and more accurate version of the pattern. In this presentation I review this technique as specifically applied to compact range antenna measurements, and apply it to several patterns, to demonstrate the method.

Productivity Improvements for a Gated-CW RADAR

Author: J. B. Wilson
Publication: AMTA 1990
Copyright Owner: NSI-MI Technologies

This paper will describe new developments in a gated-CW radar that has been designed to improve the productivity and sensitivity of RCS measurements. Improvement in data acquisition speeds result from the design of a fast synthesizer, a data acquisition co-processor and pulse modulator. Each of these new products have been specifically designed to take advantage of the high speed capabilities of Scientific-Atlanta’s Model 1795 Microwave Receiver. The RF sub-system has also been designed to permit continuous 2-18 GHz, full polarization data acquisitions. Critical RF components are now mounted at the feed in the chamber, improving the sensitivity and ringdown of the the system. Productivity in analysis activities has been improved by the use of a multi-tasking system controller which permits simultaneous use of the system for acquisitions, analysis, and plotting.

The Effects of Non-Systematic Instrumentation Errors on Measurement Uncertainty

Author: 0. M. Caldwell
Publication: AMTA 1990
Copyright Owner: NSI-MI Technologies

The effects of non-systematic receiver instrumentation errors on precision antenna measurements are investigated. A simple uncertainty model relating dynamic range to random perturbation effects on amplitude measurements is proposed. Examples of measurement uncertainty versus both input level and measurement speed are presented using data taken on modern measurement receivers. Data are compared w1th the model to estimate measurement uncertainty at various pattern levels and acquisition speeds. Equivalent dynamic range specifications are deduced from the measured data.

Use of Clustered Feeds in a Compact Range for RCS Measurements

Authors: Marion C. Baggett and Dr. William G. Swarner
Publication: AMTA 1990
Copyright Owner: NSI-MI Technologies

Increased productivity and higher resolution imaging capabilities are becoming of greater concern for RCS ranges. The ideal measurement scenario involves taking data on all desired frequencies for a target configuration in a single rotation. This could involve one or more frequencies in several bands, imaging data on more than one band or very high resolution imaging data covering several bands. Placing several feeds in a cluster at the focal point of an offset fed com-pact range can provide these capabilities. The effects of feed clustering such as beam tilt are discussed along with cluster sizes that provide little if any degradation in compact range performance. Experimental data is shown that gives an indication of the quality of data that may be obtained. The concepts are also applicable for outdoor ranges that have an array of antennas offset from range boresight.