Abstract: According to certain embodiments, a temperature measurement system includes a radiometer coupled to an antenna and a signal processor. The radiometer is operable to generate two or more signals representing electro-magnetic radiation received at a corresponding two or more differing frequencies. The signal processor receives the two or more signals from the radiometer while the antenna is placed adjacent to a surface of a substrate, and compares the two or more signals with one another to determine a brightness temperature of the substrate at a depth of the substrate from the antenna.

Abstract: In one embodiment, a system includes a first cold noise source, a first radiometer receiver, and a first detector. The first cold noise source generates a first thermal radiation signal having a first carrier frequency band. The first thermal radiation signal carries a first information signal. The first cold noise source also transmits the first thermal radiation signal through a first antenna. The first radiometer receiver receives the first thermal radiation signal through a second antenna, and the first detector extracts the first information signal from the first thermal radiation signal.

Abstract: In one embodiment, a system includes a first cold noise source, a first radiometer receiver, and a first detector. The first cold noise source generates a first thermal radiation signal having a first carrier frequency band. The first thermal radiation signal carries a first information signal. The first cold noise source also transmits the first thermal radiation signal through a first antenna. The first radiometer receiver receives the first thermal radiation signal through a second antenna, and the first detector extracts the first information signal from the first thermal radiation signal.

Abstract: Apparatus and a method for radiometric temperature measurement comprises a radiometer receiver coupled to an antenna/calibration switch that has coupled thereto a brightness temperature signal. A driver coupled to the antenna/calibration switch controls the operation of the switch between an antenna mode and a calibration mode. An adjustable cold/warm noise source is coupled to the antenna/calibration switch to provide a calibration radiation temperature applied through the antenna/calibration switch in the calibration mode to the radiometer receiver. An output of the radiometer receiver is coupled to the adjustable cold/warm noise source and is adjusted in accordance with the output of the radiometer receiver for a null comparison measurement. Also coupled between the output of the radiometer receiver and the antenna/calibration switch is a mode selector switch that operates to a mode one position to couple the output of the radiometer receiver to the adjustable cold/warm noise source.

Abstract: Apparatus and a method for radiometric temperature measurement comprises a radiometer receiver coupled to an antenna/calibration switch that has coupled thereto a brightness temperature signal. A driver coupled to the antenna/calibration switch controls the operation of the switch between an antenna mode and a calibration mode. An adjustable cold/warm noise source is coupled to the antenna/calibration switch to provide a calibration radiation temperature applied through the antenna/calibration switch in the calibration mode to the radiometer receiver. An output of the radiometer receiver is coupled to the adjustable cold/warm noise source and is adjusted in accordance with the output of the radiometer receiver for a null comparison measurement. Also coupled between the output of the radiometer receiver and the antenna/calibration switch is a mode selector switch that operates to a mode one position to couple the output of the radiometer receiver to the adjustable cold/warm noise source.

Abstract: A radiometer calibrating system utilizes an adjustable noise source for calibrating a radiometer. The noise source includes a transistor configured as a noise equivalent circuit having a gate port, drain port and source port. A source inductance providing series feedback for the noise source has one end coupled to the source port of the noise equivalent circuit and another end connected to the ground. A bias circuit controls the amount of DC bias applied to the noise equivalent circuit. In order to match the impedances in the noise source, an output impedance matching network is connected to the drain port and an input impedance matching network is connected to the gate port of the noise equivalent circuit. The output and input impedance networks have an output port and input port, respectively.

Abstract: A radiometer calibrating system utilizes an adjustable noise source for calibrating a radiometer. The noise source includes a transistor configured as a noise equivalent circuit having a gate port, drain port and source port. A source inductance providing series feedback for the noise source has one end coupled to the source port of the noise equivalent circuit and another end connected to the ground. A bias circuit controls the amount of DC bias applied to the noise equivalent circuit. In order to match the impedances in the noise source, an output impedance matching network is connected to the drain port and an input impedance matching network is connected to the gate port of the noise equivalent circuit. The output and input impedance networks have an output port and input port, respectively.

Abstract: A radiometer calibrating system utilizes an adjustable noise source for calibrating a radiometer. The noise source includes a transistor configured as a noise equivalent circuit having a gate port, drain port and source port. A source inductance providing series feedback for the noise source has one end coupled to the source port of the noise equivalent circuit and another end connected to the ground. A bias circuit controls the amount of DC bias applied to the noise equivalent circuit. In order to match the impedances in the noise source, an output impedance matching network in connected to the drain port and an input impedance matching network is connected to the gate port of the noise equivalent circuit. The output and input impedance networks have an output port and input port, respectively.

Abstract: A microwave active noise source and method used for calibrating a radiometer includes a transistor configured as a noise equivalent model having a gate port, drain port and source port. During calibration of the radiometer the drain port is terminated and a bias circuit applies DC bias to the noise equivalent model. The bias circuit controls the DC bias such that a hot thermal radiation temperature and a cold thermal radiation temperature are alternately generated at the gate port of the noise equivalent model. A source inductance coupled to the source port of the noise equivalent model provides series feedback. To match the impedances in the noise source, an output matching impedance network is connected to the drain port and an input matching impedance network is connected to the gate port of the noise equivalent model. The input matching impedance network includes an input port for outputting the hot and cold thermal radiation temperatures used to calibrate the radiometer.

Abstract: A high frequency target seeking device, using a stabilized reflector antenna, performs range search and tracking functions and target angle search and tracking functions. A technique is provided for target range discrimination using several narrow band i.f. filters, also thereby improving signal-to-clutter ratio and signal-to-receiver noise ratio. Target search is accomplished with simultaneous range and antenna azimuth scanning, with the range bins and the antenna beam swept across the target. A multiplexer selects the range bin having signals indicative of the target. Target range tracking is accomplished by the multiplexer additionally automatically selecting range bins adjacent to the target's range bin and comparing their output signals. Antenna stabilization is accomplished utilizing signals from vehicle pitch, roll, and yaw rate sensors, and antenna elevation and azimuth rate and angle sensors.

Abstract: An apparatus for rapidly starting and stopping a conical scan antenna beam in which a feed rotating about a centerline provides a non-conical scan antenna beam during a search mode. When a target is detected a solenoid moves an actuator pin which displaces one end of the feed from the centerline providing a conical scan antenna beam for target tracking.

Abstract: An air-to-ground tracking guidance system wherein a tracker/illuminator and a terminally guided seeker are utilized. Target track is initially established by the tracker/illuminator which also provides a target illuminating signal. Semi-active tracking utilizing the reflected target illuminating signal is employed by the seeker after launch. During this period of operation, the seeker is prevented from tracking the tracker/illuminator by means of a unique guard radiation system. The semi-active mode is supplemented by an active mode in which the seeker tracks reflections of a target illumination signal emitted therefrom and a passive mode during which the seeker tracks the radiometric thermal emission from the target. While in the semi-active mode, the seeker establishes a range track that is independent of the semi-active mode of operation. This permits the seeker to automatically convert the mode of operation to active and passive at the desired positions along the seeker's track.

Abstract: An improved microwave radiometric system features the employment of incoherent noise illumination of a selected target for improving the measured radiometric temperature contrast between the target and its spatial background and for increasing the distance at which such a target may be detected. Broad band noise illumination is cyclically transmitted and the receiver is cyclically activated in the high frequency signal comparison system under control of a phase locking loop so that optimum comparison is achieved over a variety of target distances.

Abstract: A continuous-wave frequency-modulation active radiometric target seeking device performs search, acquisition, and tracking functions. A technique is provided for target range discrimination and recognition using a pair of narrow band i.f. filters also improving both signal-to-clutter ratio and signal-to-receiver noise ratio. Target search is accomplished with simultaneous and synchronized range and antenna azimuth scanning with range bins effectively swept across the target by variably modulating the transmitted carrier frequency. Recognition of a substantially point target is achieved by a bipolar pulse discriminator responsive to the i.f. filter pair. Upon target acquisition, tracking is maintained by imposing a high frequency dither upon the modulation frequency in a closed loop control using only a single i.f. filter.

Abstract: An improved high frequency radiometric system features time shared passive and active modes of operation for correlation of active and passive signal returns. The processed, normalized, and stored passive signals are subtracted from similarly treated active signals to suppress the effect of returns from back ground terrain, thus enhancing true target recognition. A second channel provides discrimination against jamming and spurious signals, thus reducing false alarms.

Abstract: The improved radiometric target seeking system incorporates automatic gain control features including phase tracking automatic gain and automatic gain scan amplitude controls in a system which is basically a dual-axis, gimballed, conical-scan radiometric sensor designed to operate in either active or passive modes and to provide angular line-of-sight rate steering signals to guidance control apparatus. Target-derived automatic gain control signals permit separation of desired stationary target signals from significant background clutter, and a unique adaptive processor minimizes degradation of tracking response and accuracy.