Abstract: A communications system, such as part of a real-time location system, includes a transmitter that can be part of a location processor, tag emission reader or tag interrogator that generates a frequency shift key (FSK) modulated wireless communication signal representative of digital data and transmits the communications signal over a wireless communications channel. A receiver such as incorporated within a tag transceiver used in the real-time location system receives the FSK modulated communication signal. The receiver includes a circuit for calculating the magnitude of low and high tones of the FSK modulated communication signal and a threshold for amplitude shift keyed (ASK) channel data and FSK channel data to derive the digital data even in the presence of on-tone jammers in the communications channel.

Abstract: An elapsed time clock is incorporated into a part call tag for requesting replenishment of components used by workstations of a manufacturing facility. One or more transmission readers spatially distributed around the manufacturing facility detect a part call signal transmitted from the part call tag. A reader output processing subsystem processes part call signals detected by at least one of the tag transmission readers to recover information contained in the part call signal. A management processor associates the recovered information with a respective workstation, and what component is to be replenished. The elapsed time clock is reset when the part call tag is operated to transmit a part call signal, and thereby serves as a call tag ‘stop watch’—informing workstation personnel of the length of time that has elapsed since the last part call transmission from that tag.

Abstract: A communication system provides robust, short range radio communications between battery operated devices by using ON-OFF-KEYED (OOK) modulation and either frequency shift keyed (FSK) modulation or pulse position/width modulation (PPM/PWM), in combination with a prescribed communications protocol. The system transmitter requires no local oscillator and is only active during actual communication, so that its current drain is not a significant factor in total battery life. Also, the receiver is active for only a small fraction of time. The need for large, complex and expensive filters is minimized by using a single IF band-pass filter in active form or passively in the form of a low cost ceramic filter such as those used in inexpensive transistor radios. The digital transmitter and receiver portions of the system are implemented by low cost, and ultra low power CMOS logic.

Abstract: A call tag-based material replenishment system employs a tagged object radio location infrastructure of the type described in the U.S. Pat. No. 5,920,287. For each different part used by a lineside workstation an associated ‘call’ tag is placed at or near that workstation. To initiate replenishment of a part, a ‘call’ push-button on a call tag is operated. In response to the operation of the call button, an RF signal burst containing tag identity and status data is transmitted from the call tag. This information is recovered by a spatially distributed reader and processor subsystem for application to an asset management database. The database associates the call tag's identification data with a particular part, to enable a resource management operator to specify what component is to be accessed from storage and delivered to the requesting call tag's workstation.

Abstract: To reduce the size and power dissipation of a feed-forward amplifier, two identical high power amplifiers in a quadrature combined configuration function both as the main amplifier and as the error amplifier. The feed-forward amplifier has two control loops to increase amplifier linearity and reduce intermodulation distortion. A first loop is provided to subtract a properly scaled and delayed sample of the amplifier input spectrum from a scaled and phase shifted sample of its output spectrum which contains intermodulation distortion. The result of this subtraction (if the samples are maintained at the same amplitude and 180 degrees out of phase) is a signal rich in the intermodulation products of the amplifier.

Abstract: A first loop is provided to subtract a properly scaled and delayed sample of the amplifier's input spectrum from a scaled and phase shifted sample of its output spectrum which contains intermodulation distortion. The result of this subtraction (if the samples are maintained at the same amplitude and 180 degrees out of phase) is a signal rich in the intermodulation products of the amplifier. A feature of the invention is a differential phase-amplifier comparator which compares the signals prior to and after amplification and generates control signals for amplitude and phase trimmers for the signal prior to the amplifier and thus maintains the required equal amplitude and 180 degree phase relationship required for carrier cancellation. The signals before amplification and after amplification are subtracted leaving substantially the intermodulation products resulting from amplification.