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The novel application of correlation radiometer theory to the detection of self-luminous objects at close range is presented in the context of human presence detection. Modifications and additions to techniques developed in radio astronomy and remote sensing for close-range terrestrial situations are developed and discussed. To demonstrate the new techniques, a Ka-band correlation radiometer is presented, which detects the presence of a stationary human in an outdoor environment. The correlation radiometer fringe frequency is analyzed in the context of the scanning beam detection system and is estimated using MUSIC and ESPRIT. The visibility, sensitivity, spatial resolution, and dwell time of the system are analyzed. Finally, the correlation response is included in a statistical classifier in conjunction with responses from total power radiometers. Experimental results show improved detection capability over using the total power sensors alone. Index Terms--Correlation radiometry, human presence detection, millimeter-wave radiometry, object detection, remote sensing.

A novel method of human presence detection using passive millimeter-wave (MMW) sensors is presented. The method focuses on detecting a standing human from a moving platform in a cluttered outdoor environment using MMW radiometry, which has not been attempted before. [K.sub.a]-band radiometers are used in the total power mode, as well as correlation mode, which ideally responds well to self-luminous objects such as humans. The intrinsic radiative power from a human is derived, as well as the responses of the total power and correlation modes. A summary of the system hardware design is presented, as well as experimental results. Lastly, a simple Bayesian classification formulation is introduced and shown to produce promising results in classification of humans and nonhumans. Index Terms--Correlation radiometry, human presence detection, microwave radiometry, muitisensor systems, robot sensing systems, site security monitoring.

A tunable, electrically small, wire antenna is developed for HF/VHF ground wave transmission. A variable capacitor is serially connected to tune the resonant frequency of the antenna. The optimal position for the placement of the capacitor is evaluated by numerical simulation. The tuning range and sensitivity are also investigated. A prototype antenna is built and tested, and the measured tuning performance is compared to the simulation results. Transmission loss tests are carried out in several nonline-of-sight environments. The measured transmission loss of the tunable small antenna is found to be within 1 to 2 dB of that of a commercial whip across the tested frequency range. Index Terms--HF antennas, monopole antennas, tunable antennas, VHF antennas, wire antennas.

We report on the use of a genetic algorithm (GA) in the design optimization of electrically small wire antennas, taking into account of bandwidth, efficiency and antenna size. For the antenna configuration, we employ a multisegment wire structure. The Numerical Electromagnetics Code (NEC) is used to predict the performance of each wire structure. To efficiently map out this multiobjective problem, we implement a Pareto GA with the concept of divided range optimization. In our GA implementation, each wire shape is encoded into a binary chromosome. A two-point crossover scheme involving three chromosomes and a geometrical filter are implemented to achieve efficient optimization. An optimal set of designs, trading off bandwidth, efficiency, and antenna size, is generated. Several GA designs are built, measured and compared to the simulation. Physical interpretations of the GA-optimized structures are provided and the results are compared against the well-known fundamental limit for small antennas. Further improvements using other geometrical design freedoms are discussed. Index Terms--Genetic algorithms, small antennas, wire antennas.

The application of genetic algorithm (GA) optimization to the design and analysis of planar monopole antennas is presented. GA is first used to optimize the impedance matching bandwidth of two particular planar element shapes, the bow-tie (BT) and reverse bow-tie (RBT). The results of this study indicate that the RBT can achieve a significantly wider bandwidth with a much smaller size than the traditional BT. In a follow-on study, GA is used to generate arbitrarily shaped planar monopole designs, which exhibit improved broadband performance and/or reduced size compared with the RBT. The designs generated by the GA demonstrate a better tradeoff between matching bandwidth and electrical size compared with planar monopole designs previously characterized in the literature. Analysis of results from simulation and measurement are presented, which provide insight into the operation of these antennas as well as the key parameters that lead to improved performance. Finally, a performance bound is generated to relate the bandwidth limitation of planar monopoles to size. Index Terms--Genetic algorithms (GA), planar monopole antennas, size-reduced antennas, ultrawide-band antennas.

This paper describes a new technique to compensate output variations of total power radiometers due to physical temperature changes of the instrument. This technique performs the correction without the addition of expensive microwave hardware required in Dicke switching or many other widely used methods. A characterization period, over which the input antenna temperature is known, indicates the appropriate output adjustment needed for a change in physical temperature of the radiometer. The method effectively corrects the output in an example radiometer system built with inexpensive commercially available parts. For a 30-K variation in physical temperature, the measured data shows an improvement from 60-K peak-to-peak error to 6.9 K with an average absolute error of 1.1 K. Index Terms--Microwave radiometer, microwave receiver, passive sensing, remote sensing, temperature compensation, total power radiometer.

A novel conical monopole antenna composed of multiple spiral wires for the HF to VHF frequency bands is presented. The antenna exhibits broad bandwidth and good efficiency in an electrically small package. Broadbanding and impedance matching techniques used during the design process of this antenna are described. Measured data from a VHF version of this antenna is shown. The performance of this antenna is then compared to the performance of other electrically small antennas. Index Terms--Conical antennas, folded antennas, helix antennas.

A technique for enhancing the gain of a wide-flare angle pyramidal horn is described. The gain of the antenna is increased by placing simple metal strips or baffles inside the horn near its throat. Two baffles, an E- and an H-plane baffle, are described and analyzed. The baffles are first analyzed through two-dimensional (2-D) numerical calculations and then through measurements in an experimental X-band horn. Each baffle enhances the antenna's gain in the respective plane. When the baffles are implemented together the gain enhancement is additive in decibels. The numerical calculations and measurements show that baffles can be used to significantly reduce the size of pyramidal horn antennas. Index Terms--Antenna gain, horn antennas.