Abstract: A surface acoustic wave (SAW) device is provided which includes a piezoelectric substrate, an input transducer formed on the substrate for launching acoustic surface waves along a propagation path on the substrate, an output transducer formed on the substrate across the propagation path from the input transducer for receiving acoustic surface waves generated by the input transducer, and at least one area of acoustic energy absorbing material, preferably polyimide, formed on the substrate between the edge of the substrate and a corresponding transducer. The acoustic absorber is patterned on the SAW device substrate while the device is still in wafer form using photolithographic processing techniques.

Abstract: A wetness indicator used on absorbent pads such as diapers for visually signalling the presence of water. The wetness indicator preferably comprises a hydratable salt mixture applied to a water permeable membrane and visible from an external observation of the absrobent pad. The hydratable salt has the characteristic of changing from the color it exhibits in its normal, anhydrous state to a contrasting color when it becomes hydrated. The wetness indicator is physically disposed within the pad so that it contacts water as it reaches the absorbent layers of the pad. The wetness indicator is constructed so that the hydratable salt mixture does not leach back into the absorbent layer or into contact with the wearer of the pad. The hydratable salt may be arranged to combine with a binder upon hydration to reduct toxicity.

Abstract: Representations of signal edges of a repetitive signal are sampled without triggering, then sorted out based on frequency and sequence and then superimposed along a common time base of one period in order to reconstruct a signal. In a specific embodiment of a method according to the invention, a string of samples of a repetitive, input signal with high frequency components is captured without triggering with relatively low time resolution to determine an approximate waveform from the low resolution samples, then digital signal processing techniques in the form of a fast Fourier transform are applied to a reconstructed time record of the input signal to obtain an accurate frequency for each signal component, and finally the sampled waveform is reconstructed by overlaying sampled components with reference to a common time or phase reference. The FFT is employed to determine the frequency of each signal component very accurately.

Abstract: A method and apparatus for calibrating absolute and relative measurements of modulation and/or demodulation transfer characteristics of electro-optical and opto-electrical devices during setup of a lightwave component measurement system for characterizing performance of fiber optic systems and associated components. The lightwave component measurement system calibrated in accordance with the method of the invention provides the capability to measure the optical, electrical, and, especially, the electro-optical (E/O) and opto-electrical (O/E) components with specified measurement performance. In accordance with the calibration method of the invention, when the lightwave component measurement system is used to characterize an E/O or O/E device, an initial calibration reference is established based on the known characteristics of a lightwave source and lightwave receiver included in the lightwave component measurement system.

Abstract: Upon the adjustment of a control setting of a test instrument, the current data (taken before the change is effected) is manipulated by recalculating the trace data in light of any adjustment that is entered by a user. This represents an estimate of the effect of the adjustment in the control setting, and this estimate is redrawn on a display device. This modified image is preferably displayed before the real new image is ready to be displayed. This provides immediate feedback to the user so that adjustments can be effected without slowing the measurement process. Various embodiments provide panning or repositioning the trace left and right while changing the x-axis center frequency; stretching or compressing the trace (spanning) while changing the frequency span; or using a combination for adjustments to only the start or stop frequency. In one embodiment, the estimate can be displayed only after the user has committed to having a new measurement performed.

Abstract: By combining four hexagonal ferrite spheres under the same electromagnet structure, a magnetically tuneable bandpass filter can be built in waveguide yielding high off resonance isolation, while keeping insertion loss to a reasonable value. Implementations of this filter in A, Q, U, and V bands have typical off resonance isolation greater than 70 dB and insertion loss less than 13 dB for full-band tuning. The filter can be utilized as a preselector for swept-frequency signal analyzers, for example.

Abstract: A signal measurement system with softkey menus for guiding a user in selecting a desired test setup, including selection and connection of the device to be tested, as well as selecting calibration measurement and test measurement for the device. In response to a given softkey selection, the signal measurement system prompts the user with a set of displayed textual instructions and pictorial diagrams via a user interface to step the user through setup, calibration, and measurement processes. Preferably, a signal processing unit (or analyzer) included in the signal measurement system incorporates the user interface in firmware to guide and aid the user in connecting the device to be tested to the signal measurement system for the desired test, and leading the user through calibration and measurement processes. The analyzer preferably displays the softkey menus, instructional text displays, and pictorial block diagram displays on a cathode ray tube included in the analyzer to guide the user.

Abstract: An actual optical field spectrum is mixed down to baseband and can be observed directly to measure the optical field spectrum of an optical signal based on a local oscillator approach. This local oscillator approach is achieved without adding an additional local oscillator. A single optical source, such as a laser, is controlled by a modulation source for selectively modulating the optical signal produced by the optical source. Accordingly, the optical signal produced by the optical source alternates between two states, namely, an unmodulated state and a modulated state which carries the optical field spectrum of interest. Preferably, the optical signal produced by the optical source is routed to an optical conduit in parallel with an optical delay line. Although the two states of the optical signal produced by the optical source occur sequentially in time, they are mixed together concurrently after being channeled through the parallel optical circuit comprising the optical conduit and the optical delay line.

Abstract: A test method and apparatus to aid a site operator in discriminating between signals measured at different times, as well as enabling a level of automation which is appropriate using state-of-the-art instrumentation for performing EMI measurements, such as open-site EMI measurements. Preferably, discrimination between the two signals is based on the two signals being separated by at least a frequency E defined as:E=2(frequency span/N)+K * RBWwhere:E=possible frequency error of a signal; frequency span=frequency range swept by a measuring receiver, for example, a spectrum analyzer;N=number of points measured;RBW=resolution bandwidth of a resolving bandpass filter of the measuring receiver; andK=constant less than or equal to one to account for unknown signal characteristics.With the specific application to open-site EMI measurements, preferably signals are allowed to be falsely detected as separate signals in order to take into account unknown signal characteristics, i.e., 1 RBW.fwdarw.K * RBW.

Abstract: An apparatus and method for calibrating a yttrium-iron-garnet-tuned filter (YTF) is disclosed. Instead of using both tune+span information from the 1st LO, only the sweep ramp used to span the 1st LO is used for the YTF's s own swept spans, and the YTF has its own tune information created independently of tune of the YIG oscillator. This allows calibration at any time, both in the factory or in the field.

Abstract: A precision transmission line in the form of a short air line, and calibration of a network analyzer using the short air line, are disclosed. The short air line is approximately one-quarter wavelength at the middle frequency of the measurement frequency range. One embodiment comprises a very short coaxial air line. The inner conductor is threaded onto a mating inner conductor, such as the inner conductor of the network analyzer test port. For reliable interface at the other end of the inner conductor, a precision coaxial connector is preferably provided for connection to a device under test. The outer conductor is then attached coaxially to the inner conductor between the network analyzer test port and the device under test. Another embodiment comprises a waveguide for calibrations at higher measurment frequencies. In the case of the waveguide, locating structure is provided for properly orienting the waveguide with respect to the network analyzer test port and the device under test.

Abstract: A portable interactive electro-optic data input/output, storage, processing, and display device responsive to hand printed text and hand drawn graphics. The device preferably comprises a combined flat panel display and pen sensing surface constructed from non-mechanical, non-emissive display elements, such as liquid crystal display elements. The device also comprises an input pen for manual entry of hand printed text and hand drawn graphics, as well as commands, directly onto the display surface for providing an electronic writing and drawing slate. The display elements themselves are preferably utilized as input pen sense locations. The flat panel display and pen sensing surface is constructed so that there is no display distortion when the input pen is in contact with the surface. Rapid input pen sensing is provided for accommodating natural pen movement on a high resolution, large area display.

Abstract: This invention is directed to an NPIN (or PNIP) diode structure and epitaxial process for fabricating same wherein the thickness and doping levels of the intermediate layers of the structure and such that these layers are substantially depleted of majority carriers and therefore enable the structure to be operated at zero volts DC bias. This structure may be utilized either as an efficient detector diode or a mixer diode substantially free of odd order harmonic mixing products, and both devices may be fabricated in a single molecular beam epitaxial process with the advantage of high control over epitaxial layer thickness and impurity concentration.

Abstract: A FET variable absorptive attenuator utilizes FETs as variable resistors controlled by voltages applied to their gate terminals, the FETs preferably being arranged in a T configuration with resistors connected in parallel with two series FETs, as well as a shunt FET in the form of a distributed shunt FET. One control voltage adjusts the resistances of the series FETs, and another controls the resistance of the distributed shunt FET. A proper combination of the two control voltages yields a desired level of attenuation with optimum input/output impedance matching. The resistors allow the series FETs to be biased well below their pinch-off voltages to minimize the parasitic capacitances of the series FETs at relatively high attenuation settings, improving the isolation for high attenuation settings at relatively high frequencies and also enabling the attenuator to function as a switch. They also improve the power-handling capability at high attenuation settings.

Abstract: A tracking YIG tuned filter-mixer circuit is provided. In the preferred embodiment, four YIG-tuned resonators are combined to provide a tracking filter-mixer with a switched input. Field coils produce a magnetic tuning field that is uniform over the four YIG resonators. The first YIG resonator acts as the first stage of the filter, and in combination with a PIN diode circuit switches the RF input signal either to an output port or into the succeeding stages of the filter mixer. The second YIG resonator acts as the second stage of the filter. The third YIG resonator acts as the third stage of the filter, and as a fundamental mixer for combining the input RF signal with a swept LO signal to produce the IF output signal. The fourth YIG resonator acts as a discrimintor, comparing the LO frequency to the filter tuning frequency to generate an error signal for the field coil drive circuit.

Abstract: An RF network analyzer is disclosed which is suitable for both laboratory and automated production measurements. An important feature of the invention is the ability of the user to completely specify the method of calibration to be used. In particular the user can select any three arbitrary RF standards having known electromagnetic response characteristics and can attach them in any arbitrary order to perform the calibration of the instrument. This calibration is carried out by measuring the RF scattering parameters S.sub.11, S.sub.21, S.sub.12, and S.sub.22, storing the data in a memory, and then calculating vector error correction coefficients that are characteristic of systematic errors introduced by the RF network analyzer into measured scattering parameters.

Abstract: A finline structure comprises a dielectric substrate-mounted circuit disposed within a waveguide having on the substrate integrated distributed capacitance elements at least partially formed by laterally separated metallization layers. Thin-film construction techniques may be employed in construction. In general, the distributed capacitance elements permit the biasing of a plurality of circuit elements in a finline transmission medium. In selected structures, r.f. continuity is effected between traces and metallization layers while maintaining d.c. isolation. Examples are described of circuits which can incorporate an integrated capacitor, including but not limited to detectors, r.f. modulators, r.f. attenuators, amplifiers, and multipliers. According to the invention, a plurality of elements, as well as multiple port elements, may be selectively biased while retaining d.c. isolation and r.f. continuity.

Abstract: A bus system is disclosed in which stations having a message to send request access to a parallel bus and an arbitrator responding to the requests connects the transmitters of the stations to the bus in sequence. The words of a message placed on the bus respectively represent the address of the station to which the message is to be delivered, the address of the sending station, and data. A station asserts a signal on one control line in response to its address being on the bus and asserts a signal on another control line if it cannot receive a message. Whether the entire message is placed on the bus or not by the sending station and loaded into the registers of the receiving station depends on whether or not their signals are asserted. An external data transfer means places signals to a station on another parallel bus on an external bus. The external bus is in the form of a loop so that the message eventually returns to the station that sent it.

Abstract: A keyboard assembly has a PC board providing a series of switch contacts and a molded rubber keyboard providing a rubber base sheet overlying the PC board and having a series of rubber keys integral with the base sheet. Each key has contacts on its bottom surface for closing each of the switch contacts when its key is depressed. Stabilizing membranes prevent the keys from wobbling or binding. The membrane snugly engages each key, and the membrane is flexible along its Z axis but sufficiently stiff along its X and Y axes to limit the movement of the keys to strictly linear movement toward and away from their respective PC board switches.

Abstract: Nonrefractory micrometer-thick deposited metal or metallization, for example, aluminum and aluminum alloy films, on integrated circuits are planarized by momentarily melting them with optical pulses from a laser, such as a xenon chloride excimer laser. The substrate, as well as any intervening dielectric and conducive layers, are preheated to preferably one-half the melting temperature of the metal to be planarized, thereby enhancing reflow of the metal upon melting. This improves planarization and reduces stress in the resolidified metal. Laser planarization offers an attractive technique for fabricating multilayer interconnect structures, particularly where a number of ground or power planes are included. Excellent step coverage and via filling is achieved without damaging lower layers of interconnect.