Abstract: The present radar altimeter operates in accordance with the frequency modulated continuous wave principle in the C-band. The altimeter is constructed with microminiaturized integrated circuits and provides a completely digital signal evaluation and mode control which enables the transmitter to produce a wave-form providing the altimeter with the following advantages. A silent mode during the signal evaluation greatly improves the resistance of the altimeter against electronic countermeasures. The transmitter frequency is stabilized and a compensation for Doppler frequency drift is provided. Further, the altimeter is able to discriminate between intended proper targets on the one hand and false or erroneous targets on the other hand. The altimeter is equipped with a self-testing unit which provides different functions in different modes.

Abstract: For effectively suppressing echo of an electromagnetic wave emitted from an electromagnetic device (24) disposed in a closed space (13) which is defined by a shielding wall (10), an electromagnetic anechoic chamber comprises an absorption member (28) disposed in the space. The wall has an inner surface which reflects the electromagnetic wave into the space as a reflected wave. The reflected wave is directed to a particular position in the space. The absorption member is located at the particular position. Preferably, the inner space is formed along a substantially ellipsoidal shape having a first and a second focus point (14, 16). The electromagnetic device and the absorption member are locsated at the first and the second focus points, respectively.

Abstract: A moving target detector (MTD) in a radar system uses corrected weighting coefficients to compensate for pulse stagger effect on transmitted pulses. Transmitted pulses are sampled when the radar is switched to a test mode for determining a correction factor which is used to calculate the corrected weighting coefficients. The radar return signals are processed in the MTD by a finite impulse response (FIR) filter using the stored corrected weighting coefficients calculated for each sequence of transmitted pulses including block stagger and pulse stagger sequences.

Abstract: An electromagnetic test method simulates the effects of plane electromagnetic wave illumination on a conducting body. A conductive sheet is placed in the vicinity of the body and connected to an electrical ground. Alternating current from a current generator is injected into the conducting body via electrodes positioned at spatially separated points on the body's surface. The fields generated by the injected currents and the mirror currents in the grounded conducting sheet induce fields which create an overall current distribution in the conducting body substantially identical with that resulting from the incidence of a plane electromagnetic wave upon the body.

Abstract: A radio-frequency unechoic chamber (electric wave nonreflecting room) is disclosed. The radio-frequency unechoic chamber comprises radiowave reflectors which are provided on all inside of peripheral walls whose upper portion is open and a screen to cut off reflected waves which is arranged between an antenna and the mounting table of a test apparatus and which has a gap for allowing only direct waves from said antenna to pass.

Abstract: Measurement of radar cross section is provided by a rotatable platform which supports a test subject to be measured, the rotatable platform and a rotator thereof being enclosed within a fixture configured as a body shaped as an airfoil. A second rotator rotates the fixture body to face a radar antenna which illuminates the test subject, the orientation of the fixture body being selected to minimize a radar cross section of the fixture body. The configuration of the generally airfoil shape minimizes radar cross section in a preferred direction of the body. A metallic seal in the form of a thin foil overlays an interface between the rotatable platform and a surface of the fixture in the manner of a fairing which reduces spurious reflections from the vicinity of the rotator, the seal being formed of a foil having a thickness substantially less than one-quarter wavelength of radiation of the antenna to inhibit generation of reflections from the seal.

Abstract: A thermally insulated test chamber for performing antenna testing over a broad frequency range. An antenna to be tested is placed within the test chamber, which is constructed of non-RF-reflective styrofoam sheets surrounding the antenna on all sides. The air in the test chamber is heated or cooled, as desired, for testing the antenna over a range of temperatures.

Abstract: A test facility, especially for the seeker or search heads of intelligent guided ammunition, including a target simulator for the reflection of a target signature through the intermediary of antenna elements towards the search head which is mounted on a turntable or rotary member with a flight simulator. Arranged between the target simulator and the search head is a quasi-optical coupling which follows the beam geometry by means of an imaging system and, on the one hand, the search head, as well as, on the other hand, the target simulator are located in or proximate to the applicable focal point of the resultingly produced path of transmission.

Abstract: The radar includes a linearly frequency-modulated microwave frequency signal generator (1), a transmitter-receiver antenna (2) and coupling means (3, 6; 48) in order to sample a local oscillation signal and an echo signal and in order to transmit these two signals to the inputs of a mixer (5) which provides at its output a subtractive beat signal between these two signals. The line lengths are adjusted in order to produce a static adjustment of the phase between the local oscillation signal and the interference antenna reflection signal. A phase control loop including an amplifier (36) and a low-pass filter (37) is connected between the output of the mixer and an input of a phase-shifting circuit (35; 54) placed in the local oscillation channel; the closed control loop cut-off frequency is just below the frequency of the subtractive beat signal.

Abstract: An almond shaped radar cross-section test body for use in microwave anechoic chambers, which exhibits a large dynamic scattered field over large angular regions.

Abstract: A boresight chamber apparatus employs a near field measurement technique for measuring the amplitude and phase distributions of an antenna under test and then deriving the boresight error from such measurements. The antenna under test is mounted within an anechoic test chamber on a wall of the chamber. Located adjacent the antenna is a near field probe which is moved along a line parallel to the plane of the antenna. The probe, as moved, scans parallel to the surface of the antenna. At prescribed equally spaced points along the line, the amplitude and phase difference between reference signal and the amplitude and phase developed by the antenna is measured. These measured data allow one to calculate the boresight error of the antenna. The probe position is controlled by a computer which also samples the output of the phase comparator at each of the points that the probe is positioned in to thereby derive an accurate representation of the amplitude and phase distributions of the antenna.

Abstract: A test system for microwave circuits such as employed in aircraft wherein a plurality of antennas are connected to a single processor whereby the continuity of the antennas and connectors between the antennas and the processor can be determined. A test signal is applied to the various antennae of the aircraft and the return signals therefrom received by a test antenna disposed in conjunction with a low-loss coupler from outside of the aircraft. An automated test circuit provides for inputting an identifier of the antenna and circuit portion being tested, and for determining the fault location within the circuit as a function of the circuit portion under test and the distance to the fault; and for displaying the fault location within the circuit. In one embodiment, the low-loss coupler includes the use of a plurality of test antennas in combination with a divider circuit connected to the test antennas by transmission lines.

Abstract: A radar target simulator apparatus and method especially useful with a pulse compression radar located in a remote, unattended, and unpowered, terrain. Provision for generating signals which will pass through moving target indication (MTI) and minimum velocity threshold circuits are included. Transmission of the detected simulated target data through narrow-band communications lines, such as telephone lines, is contemplated. The capability for minimum discernible signal and radar power output evaluations are also provided.

Abstract: Apparatus for reducing the composite coupling signal in a frequency modulated, continuous wave radar having a single antenna and a duplexer includes a modulation signal generator coupled to a continuous wave oscillator to provide input to the duplexer. A directional coupler at the duplexer input provides input to an adjustable phase-shifter which provides a phase-shifted signal to an RF mixer. The RF mixer receives a second input from the output of the duplexer and provides a mixed signal. A level modulator having an adjustable control input receives a portion of the modulated signal from the modulation signal generator. The level modulator then provides an output to the audio amplifier which also receives the mixed signal from the RF mixer. The audio amplifier provides an output signal having reduced composite coupling signal components.

Abstract: The circular phased array antenna includes a plurality of radiating elements spaced about the circumference of a mounting ring. The radiating elements are fed with r.f. currents having relative phase and amplitude distribution to form a focused beam from the antenna. The beam is steerable to a selected direction. The monitor system includes a probe element mounted near each radiating element, phase shifters and couplers for combining signals from the probes into a transmission line. The amplitude of the transmission line signal is compared with a known value of signal for a normally operating antenna for each beam direction. A failure alarm is generated whenever the difference between the compared signals exceeds tolerance.