Abstract: A thick film resistor (TFR) is provided that is capable of being compensated for impedance variations related to the TFR laser-trimming process. According to the invention, a thick film capacitor (TFC) metallization is provided in parallel with the thick film to compensate the RF impedance. A method is also provided for calculating the exact length of the TFC metallization necessary to compensate the RF impedance. Once this length (L) is known, the TFC metallization can be laser-trimmed to obtain the desired length.

Abstract: A low power digital receiver (10) is provided that contemporaneously selects the lowest possible sampling signal frequency (34) (from a plurality of available sampling signals), and received signal level (28) to properly digitize (32) and recover a desired signal. Digitization is performed after the first IF using broadband stages (28, 30, and 32) that are temporarily enabled (44) to rapidly digitize the first IF signal. This, together with the low sampling rate, minimizes the power consumption of the receiver (10) thereby permitting portable and mobile digital receiver embodiments.

Abstract: An AM Stereo receiver is described which includes an AGC having an output which indicates whether the received signal has significantly decreased in level and having a clamping circuit for controlling the voltage at the input of a VCO. The clamping circuit is further defined as having a window detector for sensing a change in the voltage at the input of the VCO according to a predetermined threshold; a selectable controller, responsive to the window detector, for adjusting the voltage at the input of the VCO; and a window reduction circuit, responsive to the output signal of the AGC, for altering the predetermined threshold to provide the controller with a more sensitive indication of a drift in the voltage at the input of the VCO. The receiver additionally includes a conventional locked loop driver for steering the VCO according to the phase of the received input signal.

Abstract: A load pull isolation switch for a signal source is discolsed which substantially eliminates the effects of load pull caused by a variable impedance load when selectively coupled and decoupled to a signal source. By judiciously choosing the timing criteria for activating the isolation switch, convention load pull isolation stages are eliminated.In another embodiment, the load pull isolation switch is disclosed as incorporated in a mobile radio having a fast locking synthesizer. The timing of the operation of the isolation switch is controlled by a microprocessor-controller which not only handles data and control functions for the mobile radio, but also has the necessary method steps incorporated as software within the microprocessor-controller. Such an arrangement is useful for sending voice or data as in a time division multiplex system.

Abstract: Disclosed is a method to dynamically allocate a number of data channels on a trunked radio system (100). The data activity is monitored during a predetermined time interval. If activity is above a predetermined maximum, an additional channel may be reserved for data use. Conversely, if data traffic is low, a data channel may be reallocated for voice message use. Moreover, should the amount of data traffic among the available data channels be unbalanced, the present method contemplates reassigning subscriber units (114 or 116) to the available data channels to balance the data traffic load, thereby providing superior access time and system performance.

Abstract: In a digital communication system, a residual signal is generated, encoded, and combined with an encoded information signal in a manner that does not appreciably degrade the encoded information signal. The information contained within the residual signal may be used by the receivers to improve the quality of the recovered signal. The residual signal is modulated such that it may only be recovered when the signal-to-noise ratio is sufficiently high. In this way, the quality of the recovered signal improves with increased signal-to-noise ratio.

Abstract: An improved apparatus and method for a sigma delta converter for bandpass signals is disclosed, suitable for use in mobile radio applications, between the front end and digital signal processing stages, that includes at least one bandpass filter, an n-level quantizer, an n-level digital-to-analog (D/A) converter, and a direct current (DC) feedback network. The sigma delta converter for bandpass signals may be configured in a second order or a fourth order embodiment and achieves analog-to-digital conversion of a signal having a non-zero frequency carrier or suppressed carrier with improved signal-to-noise ratio performance and with minimal quantization error. As a result, the sigma delta conversion occures earlier in a receiver chain and a dynamic range of about 95-98 dB is achieved.

Abstract: An impeller is positioned within the flow of a fluid to be used to irrigate an area. The impeller drives a generator, which operates to charge and sustain a storage battery. The battery powers a receiver having an identification code by which the receiver may be addressed to receive commands, such as, for example, to open or close a valve, thereby providing fluid to irrigate an area. By opening the valve, the fluid flow is increased, and more power is generated and stored in the battery. In this way, power is generated automatically for the receiver, which, in turn, controls the fluid flow for irrigation.

Abstract: Coupled transmission line resonators, such as those in a solid-dielectric ceramic block filter, are fabricated with tuning regions formed by notches in the outer conductor extending longitudinally parallel with the inner conductors from both the low-impedance ends and the high-impedance ends of the resonators. Removing conductive material from the notches in the vicinity of the low-impedance ends of the resonators decreases their resonant frequencies; removing conductive material from the notches in the vicinity of their high-impedance ends increases their resonant frequencies. Sensitivity of tuning depends on the depth of the notches. By situating all tuning regions along a common side of a filter, tuning both higher and lower in frequency may be accomplished without a need to re-orient the filter in a production-line fixture.

Abstract: Disclosed is a method to dynamically allocate a number of data channels on a trunked radio system (100). The data activity is monitored during a predetermined time interval. If activity is above predetermined maximum, an additional channel may be reserved for data use. Conversely, if data traffic is low, a data channel may be reallocated for voice message use. Moreover, should the amount of data traffic among the available data channels be unbalanced, the present method contemplates reassigning subscriber units (114 or 116) to the available data channels to balance the data traffic load, thereby providing superior access time and system performance.