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The report describes the results of the Non-Sampling UHF Single Frequency Repeater research and exploratory development program. The effort was concentrated on the system design of a high gain, single antenna non-sampling repeater. The effort included analytical and experimental data which defined to the technical and practical limits of isolation techniques, including antenna/hybrid matching, orthogonal mixing, and frequency offset within a 50 KHz (or 100 KHz) channel. Automatic search and acquisition techniques were also developed. In addition to reporting on the exploratory model and its performance in the laboratory, this report includes the results of flight tests and recommendations for future development. (Author)

An initial design for a 10 x 10 element heterodyne array was developed using 77 K, 1500-MHz photodiodes. Five PV-HgCdTe 150-MHz MHz photodiodes were then tested on a subassembly of a heterodyne matrix array structure with NEP's below 1.5 x 10 to the minus 19th power W/Hz measured out to 150 MHz. A thermal analysis was performed for 77 and 4.2 K matrix arrays with 150 and 1500 MHz operation to determine the cooler requirement for each case and the effect of the thermal loading on photomixer performance. A thermal mockup of the 77 K, 1500-MHz, 10 x 10 array was tested verifying the multi-cable thermal load analysis, the greater than 30-dB isolation between channels, and the greater than 24-hour operating time of the thermal mockup dewar., See also report dated Oct 1972, AD0750402.

Analyses were performed on various aspects of the multielement heterodyne technology including high density cabling techniques, image plane dissection to provide 10 x 10 (100 element) spatial elements, heating effects in a matrix array, and 4 K cooler requirements to obtain the desired system sensitivity. Measurements were carried out on HgCdTe photodiodes that showed cutoff frequencies of greater than 200 MHz and a maximum noise equivalent power (NEP) of 1.7 x 10 to the minus 19th power W/Hz over the 200 MHz bandwidth. (Author), Also includes Quarterly technical status rept. no. 2. See also report dated Oct 1972, AD0750402. Sponsored in part by DARPA.

The N13 oven was redesigned to obtain additional room for insulation material and employ a longer dewar flask. A redesigned prototype N13 unit was constructed and is under test.

This report describes an investigation of circuit techniques to minimize spurious responses in varactor-tuned filters. Design equations for the center frequency, bandwidth and insertion loss of single and multiple-resonator filters are presented. Series-resonant filters with one and two resonators were constructed and measurements of their performance characteristics were made. One- and two-resonator filters were also constructed using a pair of opposingly biased varactors (push-pull circuit) for each resonator. Measurements show that such a circuit can significantly reduce the second-harmonic generation and the response to a signal at one half the tuned frequency.

The report describes the work performed during the second quarter of a study of a reflector antenna that provides zoom (variable beamwidth) and scan capability using controlled aperture amplitude and phase. The antenna consists of a primary reflector (paraboloid) and a secondary reflector/lens. It operates as a lens in conjunction with one feed for scanning in the receive mode and as a reflector in conjunction with another feed for zooming in the transmit mode. Switching between a zooming transmit mode and a scanning receive mode results in a versatile radar antenna with an inherent duplexing capability. The performance of this antenna system is being analyzed numerically with the aid of digital computers. This report describes the development of a computer program for solving the Fraunhofer aperture integral efficiently and with good accuracy.

Described is a continuation of research into the application of mathematical techniques to the evaluation of practical airport capacity and delays. Since the primary task was to develop a handbook for determining airport capacity and delays by the engineer in the field, the main effort was concentrated on developing existing mathematical models for universal application. Therefore, this report contains the background material relevant to the handbook, describes the mathematical models used, and discusses the preparation of their respective inputs. These inputs vary with runway configuration, runway use, aircraft population, and operating rules (VFR or IFR) . The airport surveys that were analyzed to provide input values and operating parameters are also described. An IBM 7090 Fortran program was written to automatically compute the inputs and model outputs in the form of delays versus operating rates and capacities of airport runway configurations. The use and application of this program is described.

Calculations of the expected performance of the unmatched Bendix circulator, as predicted by Bosma's analysis, were completed. Experimental data was obtained using the proper center conductor that agreed qualitatively with the theory. The qualitative study of idealized input impedance of a parametric amplifier, performed during the early phases of this program, was used to double-tune the balanced C-band parametric amplifier so that the phase shift would be a linear function of frequency. This technique was very successful, providing a 500-Mc instantaneous bandwidth with a gain of about 10 db, a noise figure of 3.55 db, and a relatively flat phase characteristic. The amplifier has been packaged in a standard 19 by 24 inch rack mount, and is completely self-contained.

The Federal Aviation Agency is investigating the use of the SAGE air defense system for enroute air-traffic control. The program of SAGEAIR TRAFFIC INTEGRATION AND THE EXPERIMENTAL SYSTEM USED IN THIS PROGRAM IS KNOWN AS SATIN. A beacon code-usage plan that provides for display filtering in both manual and automatic systems is developed. The performance of the AN/FST-2 as a beacon data processor is analyzed. The performance includes target detection, release, center marking, and code readout. Deficiencies in code-readout performance are indicated and possible remedies are suggested. The code- processing performance of the AN/FSQ-7 is analyzed and determined to be adequate when the AN/FST-2 deficiencies are corrected.

Several criteria relating to the handling of general aviation on airports have been developed. In many cases, modifications of existing criteria are suggested. These include the subjects of runway-length corrections, instrument-approach needs, airspace needs, annual capacity of air ports, guidance for planning separate runway facilities for general aviation, procedures for performing economic analyses, and the effects of airport accessibility. The study has concentrated on planning for general aviation in metropolitan areas. Observations of generalaviation operations at air-carrier and generalaviation airports have indicated that new criteria for determining the numbers of airports required in metropolitan areas are needed. In developing regional plans and individual airport plans,the importance of using a cost-versusbenefit economic analysis is stressed. The criteria developed have been tested by applying them to the Lambert-St. Louis airport and to regional planning for the Washington, D. C. area.

Assuming future use of runway approach and flareout guidance in extremely low visibility, this report describes an investigation of suggested techniques for aircraft guidance during landing and takeoff roll and taxiing in poor visibilities down to zero-zero conditions. The techniques examined are: ILS localizers (including DME); gyro compasses and inertial systems; infrared; magnetic cables; aircraft radar; light and line patterns from conventional light sources including lasers and radioactive materials; and miscellaneous techniques including wheel tracks. These systems are judged relative to the operational requirements and considerations, including some economic analysis. It is concluded that, for landing and takeoff ground operations, improved ILS localizer plus DME offers the best solution. For taxiing operations, magnetic leader cables show the most promise. Research programs are indicated as being necessary for both ILS/DME and leader cables.

This report describes the development and analysis of preferred circuit techniques for the reduction of certain RFI effects in reflection - type parametric amplifiers. Emphasis is placed on reducing spurious responses and increasing the saturation power of paramps. Some of the preferred-circuit techniques are incorporated in experimental models and extensive measurements are reported which support the theoretical predictions of the effects of intermodulation products on paramp performance and the effect of the balanced configuration on spurious responses. Many additional characteristic of the models are described.

Techniques for the design, construction, and evaluation of a 10-db directional coupler, a 0 to 40 db variable attenuator, a 90-degree phase shifter, and a duplexer to operate in the 300 to 1000 gc region were investigated theoretically and experimentally. Quasi-optical, oversize, trough, and Goubau-beam waveguide were studied. Quasi-optical techniques used in oversize wave guide were found to be most suitable and were used in constructing the components. These com ponents were evaluated at 0.9-mm wavelength. The experimental data showed good agreement with the design theorhus, submillimeter compo nents using quasi-optical techniques in over size waveguide can be successfully designed annd fabricated. Some components had higher inser tion loss than desired due to the dielectric dissipation effects. These losses are reduced by using a multiple-dielectric-slab coupling structure.

The capture-effect glide-slope system is explained by comparison with a standard null reference system, and the relative advantages of the glide-slope system are analyzed. A general exposition of monitor techniques leads to an analysis of capture-effect monitor problems; solutions for the particular capture-effect monitor problems are presented and logically justified. The recommended solution for the oncourse monitor is recognized as the monitordetector location is found on the antenna mast midway between the middle and bottom glide-slope antennas. An alternative solution for the course-width monitor is recognized as the monitor-detector location for the second null of the top-antenna resultant, where the middleand bottom-antenna resultants are in phase opposition at the 180-degree dephase point for middle and bottom antennas.

The report describes the results of a program investigating means of reducing the intermodulation products generated in collocated 100-watt transmitters operating in the 225 to 400 MHz frequency range. The IM reduction technique considered a cascade of four tunable isolators and a standard tunable filter to achieve a net antenna-to-transmitter isolation of 80 dB. The major accomplishment on the program was the development of a tunable, compact, lumped-parameter UHF isolator having a power handling level in excess of 100 watts with a typical forward loss of 0.5 dB, and a 20-dB isolation bandwidth of 4.3 to 7.6 percent.

This report describes the program of RF doppler detector improvement sponsored by the FAA and undertaken to eliminate deficiencies in the radio detectors used in the TRACE installation at NAFEC. Previous detectors detected aircraft but were also triggered by small, close-in, unwanted targets such as birds and rainfall. Four X-band FM-CW doppler detectors and two dual-antenna CW S-band doppler detectors that were modified from GFE supplied by the FRE DEVELOPED UNDER THIS PROGRAM AND DELIVERED TO NAFEC for test and experimentation. These detectors eliminate or greatly reduce detection of the unwanted targets by producing a dead zone immediately in front of the detector. The X-band FM-CW detector produces this zone where detection is eliminated by a frequency modulation technique, while the CW S-band unit uses physical separation of the receiver and transmitter antennas to achieve the same result. In addition, audio analysis equip ment for storing and processing received signals was furnished to the FAA to aid in testing the equipment.

The purpose of the program is to continue the research on 10.6 micrometer image upconversion detectors and to determine the feasibility of developing a 10.6 micrometer range gated upconversion imaging laser radar receiver with 150 by 150 resolution elements. An experimental model image upconverter capable of real time direct viewing has been assembled. Imaging characteristics such as resolution, field of view, and the upconversion efficiency of the experimental model were measured by arranging the model in the Fourier space and the image space configurations. Analysis describing the optical transfer function of the Fourier space configuration and the line spread functions of non-Fourier space configuration are presented. The crystal birefringency is included in the analysis. Calculation of resolving power and some consideration on the object optics are also included. Measurements of conversion efficiency and realistic estimates of practically achievable efficiency are presented and realistic values for the SHG d coefficients of proustite are considered., See also AD741227.

The Seventh Communications Division of the International Civil Aviation Organization (ICAO) has recommended the adoption of a digital code for automatic height transmission via the AIR TRAFFIC CONTROL RADAR BEACON SYSTEM. Salient features of the code are (1) One-hundredfoot digitizing increments; (2) Range from -1000 feet to +126,750 feet; (3) Compatibility with limited- capability 500-foot incremented code; (4) Unambiguous unit-distance characteristic; (5) Height transmission with respect to a fixed datum of 1013.2 millibars (29.92 inches of mercury). The code, as recommended by ICAO, is tabulated for height increments in increasing numeric order and for the equivalent octal Mode 3/A reply in increasing numeric order. The PULSE POSITIONS column lists the timesequence assignment of the pulse-transmission reply, and the HEIGHT CODE POSITIONS column gives a rearrangement of the code information in significant-digit sequence. Five-hundred-foot increments are extracted from the tables by omitting the C information pulses for the appropriate integer multiple of 500-foot height.

Research was continued on the development of a low noise, small signal, varactor diode parametric amplifier operating over a range of 2 to 4 gc. Two single-diode varactor mounts, each having a 40-percent instantaneous bandwidth, were cascaded to yield an overall gain of 10 db from 2 to 3 gc (3-db points). The noise factor of these combined amplifiers varied linearly from 1.8 db at 2 gc, to 3 db at 2.8 gc. The noise factor above 2.9 gc peaked very sharply to about 5.5 db. The reason for this peak is not yet apparent. The configuration of the final engineering model was fixed-four stages will be used and the package will accommodate either the balanced or unbalanced varactor mount.

Elements of the basic system for spotting airborne objects are described, and by means of a model radar set, the effects of such parameters as frequency, pulse width and repetition frequency, bandwidth of receiver and antenna beamwidth are evaluated, particularly with respect to range. Use of doppler effect and moving-target indicators described, also beacons. Principles of tracking radar.

The UHF Same Frequency Repeater suffered from low usable isolation because of the limitations in manually tuning the matching network of a hybrid to equal the constantly varying impedance of an antenna. Operation of the repeater was further hampered by the adjustments necessary to accommodate band switching. An Automatic Impedance Matching (AIM) network was developed to continuously adjust the impedance of the matching network to automatically maintain a high isolation between the transmitter and receiver ports of the hybrid. A common RF switch was also designed as part of this program so that channel switching could be accomplished with only one control, without the need to make readjustments. RFI due to incomplete transmitter shutdown was eliminated by the addition of a coaxial relay. Other sources of RFI were eliminated by replacing most RF cables with double-shielded coax., Supplement 1 to Rept. no. AIL-4190-2 dated Nov 69, AD-865 283.

This report describes an experiment that was performed to evaluate a new low-angle tracking (LAT) radar technique which uses array antenna technology. The process enables the radar to track targets in elevation in the low-angle region between one beamwidth and the horizon. The technique uses the array facility to form two beams, and a two-channel receiver system which forms the ratio of the signals from each beam. By design this ratio is proportional to target elevation angle. The antenna patterns are designed to suppress the multipath signal energy, but residual image signal energy entering the receiver is processed with the target signal without degradation of system performance. This technique was implemented and tested on an over-water range using an aircraft as the test target to gather data and evaluate system performance under varying reflective surface conditions. The system operated at 5.5 GHz and used a 12-foot array aperture. Tracking data was collected between elevation angles of 5 to 20 millirads with one-tenth beamwidth accuracy. A description of the flight test is given and a summary of the experimental data is presented. (Author)

The report describes a theoretical investigation of field effect transistor (FET) amplifiers and mixers. An experimental investigation of the FET amplifier was performed at VHF (60 MHz), and of the FET mixer at MF (500 kHz) and HF (20 MHz). The theoretical and experimental investigation was performed on four junction FET (JFET) devices (2N3823, 2N4416, CM647, CP650) and one Metal Oxide Silicon FET (MOSFET) device (3N152). The emphasis of the investigation was on the spurious signal generation and interference effects. A large signal model is developed for the FET and from this model, equations are derived that enable the circuit designer to predict levels of RFI in his circuits. Measurements were made of the significant interference effects in FET amplifiers and mixers and a comparison of the results showed good agreement. In addition to the discussion of RFI performance the tradeoffs between RFI performance and power gain, noise figure, and bandwidth are discussed. These considerations enable the circuit designer to make the necessary compromise to obtain a circuit that most nearly satisfies electromagnetic compatibility and system electrical performance simultaneously. (Author)

A Target Simulator was designed, built, and installed in the Signal Processing Test Facility (SPTF) located at the Floyd Test Annex, RADC, Rome, N.Y. It is used to generate fixed and moving targets for evaluation of the performance of the high-resolution Signal Processing Subsystem (SPSS). The fixed targets are delayed replicas of the transmitted radar signal and are introduced into the radar receivers at simulated ranges of approximately 100 and 500 miles. The moving target is internally generated by the target simulator and is used to test the performance of the range tracking subsystem of the SPSS. (Author)

The report covers research on microwave superconducting receiver techniques. An analysis of Josephson mixer operation, including characterization into a mathematical model suitable for analytical and computer study and a rigorous formulation of the generation of steps due to microwaves in the DC I-V characteristic, has been carried out. Experimental observation of the Josephson mixing action at 10 to 15 GHz has been obtained and is in agreement with the theory developed. The conversion loss, noise factor, and sensitivity of Josephson mixers have been measured. Using a point contact junction at 13 GHz, a minimum detectable signal of -90 dbm/MHz (measured) and -105 dbm/MHz (corrected) was obtained. Superconducting, miniature microstrip resonators operating at 10 to 15 GHz have been constructed using vacuum-deposited lead on low-loss sintered alumina substrate. Unloaded Q's (at 14.3 GHz) as high as 200,000 and 500,000 have been measured at 4.2 and 1.8 K respectively. The vacuum deposition technique used would permit the simulataneous fabrication of large numbers of miniature multielement filters and preselectors with low insertion loss and good skirt rejection. (Author)

A packaged infrared 10.6-micron heterodyne receiver was developed for radar application. It combines sensitivity approaching the quantum-noise limit with gigahertz IF bandwidth. Signal processing electronics was also provided for search and acquisition of the doppler-shifted radar return signal, and other functions. The receiver has as its principal components a cryogenically cooled Ge:Cu infrared mixer element, and associated broadband IF preamplifier, IF and signal processing electronics, and peripheral monitor and control electronics. The receiver is suitably packaged for operational use in a 10.6-micron pulsed radar system. Design considerations and measured receiver characteristics are presented. Receiver noise properties for IF frequencies up to 1200 MHz and mixer noise characteristics were measured. The measured noise equivalent power was 8.1 x 10 to the minus 20th power w/Hz at 1.4 kHz, less than 1.5 x 10 to the minus 19th power w/Hz from 10 to 800 MHz, and less than 2.25 x 10 to the minus 19th power w/Hz up to 1200 MHz. (Author)

The report covers research into superconducting receiver techniques concerned principally with the development of superconducting microwave mixers utilizing the Josephson effect and superconducting, ultra-high Q, microwave resonators, filters, and preselectors. The theory of operation of Josephson mixers, characterization into a mathematical model suitable for analytical and computer study, and a rigorous formulation of the DC I-V characteristics has been obtained. Experimental observation of the Josephson mixing action has been observed which is in excellent agreement with the theory developed. Superconducting, miniature microstrip resonators were built and the results of experimental determination of their Q's is reported. (Author)

The program has demonstrated the following technological elements. A structure to support a 3 x 3 configuration of high performance 10.6 micrometer mixer elements. An array of microlenses that generate receiving antenna beams in registration and crossing each other at a point 3 dB below their peak responses. A mixer-preamplifier combination with measured NEP values of better than 2 x 10 to the -19th power watts/Hz from 10 MHz to 1500 MHz. A microstrip cabling technique to handle the microwave IF signals detected by the infrared mixers. Adequate thermal conductivity in the array structure to extract the heat dissipated by the local oscillator beam and dc bias current. At least 30 dB of electrical isolation at 1500 MHz between adjacent cooled mixer elements.

The report covers the development of an X-band, integrated, low-noise sweeping receiver or Integrated Microwave Amplifier-Converter (IMAC) covering 8-10 GHz. Based on a system tradeoff study, the following components were selected for the IMAC: Wideband, circulator-coupled, tunnel diode RF amplifiers; varactor-tuned, tunnel diode oscillator; image-phased balanced mixer; wideband IF amplifier; narrowband IF filter. The report details the design, construction, and testing of the above components of the IMAC and includes a study of system reliability. (Author)

This research, primarily for the study and investigation of techniques leading to improved multicouplers, was part of the long range plan to improve the compatibility of collocated transceivers during adjacent channel operations. Of primary significance was the work done on superconducted resonators in the 225-400 MHz band. The information derived from this effort can be used as a basis for the design of diplexers utilizing superconducted resonators which, while somewhat costly to operate, may be required to solve specific interference problems on critical communication links. (Author)

A report is made on a program to demonstrate the feasibility of a 10. 6-micron coherent receiver array with 1.5-GHz IF bandwidth, 3 X 3 elements with -3 db antenna-beam crossovers, and near quantum-noise limited sensitivity. The two primary areas of investigation were: (1) coherent array development, which includes the formulation of an analytical model of a coherent multiple-beam array, computer-generated antenna patterns, laboratory verification of these patterns, and formulation of diffraction-limited image dissection techniques, and (2) mixer development, which included achieving Ge:Cu mixer response to 1.43 GHz (with NEP equal to, or less than 1.5 X 10 to the 19th power Hz/watt over this band), analysis of wideband photovoltaic mixing, measurements of 9 mixers of various types, and continued development of a single amplifier to cover the band from 10 MHz to 1.5 GHz.

This report describes a study and investigation of the split aperture technique for antenna intrabeam signal processing. This technique makes use of phase and amplitude information received on a number of subapertures of a large aperture antenna, in conjunction with a priori information on the number of targets in the antenna beam, to provide an improvement in angular resolution. A computer simulation is described which estimates the location of the multiple targets as a function of the relative target amplitudes and phases, S/N ratio, position in the beam and system measuring accuracy. Results obtained from an experimental setup to simulate two targets are presented and compared with the calculated results. Suggestions for possible system implementations are given. Section 1 presents a historical development of the problem, Section 2 a theoretical formulation of the split aperture technique, Section 3 the experimental measurements, and Sections 4 and 5 the conclusions and recommendations. The computer programs and signal processing techniques are presented. (Author)

A theoretical and experimental investigation of circuit techniques was conducted to provide circuits with minimum interference susceptibility for receiver application. The circuits considered are solid-state circuits for predetection functions in receivers, operating in the frequency range from 1 MHz to 10 GHz, and include bipolar transistor amplifiers, field-effect transistor amplifiers, parametric amplifiers, tunnel-diode amplifiers, crystal-diode mixers, and varactor-tuned filters. Investigations were also conducted to determine the nonlinearities and RFI characteristics of microelectronic receiver circuits and the Hall-effect mixer. Measured and predicted results of intermodulation, harmonic distortion, and cross-modulation are shown graphically for the circuits investigated. Techniques to minimize interference susceptibility and performance tradeoffs are discussed and are illustrated by developed circuits and measured data. (Author)

This report describes an investigation of radio frequency interence (RFI) in tunnel-diode amplifiers. Equations are derived which predict the harmonic and intermodulation power levels, or rejection of harmonics and intermodulation, and the percent cross-modulation as a function of tunnel-diode and circuit parameters. The parameters that must be known to make use of the equations are the diode peak voltage and current, bias voltage, source impedance, and amplifier gain. A push-pull, tunnel-diode amplifier was developed to demonstrate the feasibility and the advantages of a balanced amplifier. Measurements were made of the significant intermodulation and cross-modulation interference effects and then compared with the predicted effects. The results agreed with the theoretical predictions. (Author)

This report concerns the investigation of methods and techniques as well as the selection of materials and the evaluation of electronic components used in the final model. During this period, both types were re-designed several times in order to meet the electrical, thermal, and mechanical requirements of the program. All considerations which led to the adopted designs are presented and discussed. For detailed data, reference should be made to the four previously issued quarterly reports. Also described in this report are the difficulties encountered, their solutions, and the reasons for not meeting some of the objective specifications such as warm-up for the N13 oven.

Criteria are presented for the design of an optimally reproducible, low-cost, high-performance, parametric amplifier for use in electronically steerable radar systems. The basic amplifier configuration is that of a circulator-coupled balanced varactor parametric amplifier with the varactor pair connected essentially at the ferrite junction reference plane at the amplifier port of the circulator. A new signal frequency equivalent circuit of a pumped varactor pair has been presented with all circuit element values characterized in terms of fundamental varactor quantities. An existing design theory for a linear phase parametric amplifier has been extended to yield gain- and phase-bandwidth limitations and required circuit element values in terms of fundamental varactor quantities. The theory indicates that the gain-bandwidth and phase-linearity objectives can be met using two cascaded 10-db linear phase amplifier stages, each using a balanced pair of silicon varactor diodes of quality factor 21, a self-resonant frequency of 14.5 GHz, a nonlinearity ratio of 0.3 and a pump frequency of 17.87 GHz. A prototype model of a three-port stripline circulator was constructed for use in this amplifier. Its performance has been optimized with respect to ferrite material and magnetic field intensity for a suitable, though not sufficiently broad-band impedance characteristic over the 3.1 to 3.7 GHz range. (Author)

Design criteria are presented for the attainment of high-performance, low-cost parametric amplifiers for application to electronically steerable radar systems. A detailed comparison is made between the single-diode and balanced parametric amplifier configurations in order to establish optimum parameter requirements. It is shown that the balanced parametric amplifier offers the greatest potential for achieving the overall requirements of this program. The balanced paramp approach requires a varactor quality factor (M) of 15 to 20 GHz, and a corresponding idler frequency from 11.6 to 14 GHz. (Author)