Tektronix, Inc.

Seiko Communications Holding N.v.

Seiko Communication Systems

James D English

Daniel J Park

Jeffrey R Owen

Bruce C Nepple

Garth Upshaw

An FM signal or protocol analyzer (PA) system: The PA system is capable of analyzing the broadcast signal at many levels, from analysis of the physical RF link to comprehensive analysis of the subcarrier messaging. The PA system is built on a computer including special hardware and software. The custom hardware comprises at least one precision RF receiver and signal processing circuitry. The custom software includes data acquisition, data analysis and data presentation software. As a feature of the present invention, a PA system is designed to be 'user friendly.' As such, it operates in a windowing environment and makes extensive use of graphical displays. The PA system can operate in a networking environment so the receiver and signal processing circuitry can be physically distant from the user's display and keyboard, in another computer connected to the network. The look and feel of the PA system being operated over a network is similar to the look and feel of a PA system with all its components being local, except for any performance limitations that are imposed by network throughput.

Analyzer for frequency modulated signals

A subcarrier signal generator includes a finite impulse response (FIR) filter responsive to selected FIR coefficients. A first set of FIR coefficients represents an ideal subcarrier shape and center frequency. A calibration step monitors the resulting subcarrier signal and produces a new set of FIR coefficients corresponding generally to the ideal subcarrier signal shape and center frequency, but predistorted according to the compliment of error detected in the actual subcarrier signal. By then loading the new set of FIR coefficients and operating the subcarrier generator, frequency-dependent distortions in the output stage of the subcarrier generator cancel predistortion reflected in the new FIR coefficients. As a result, a high quality subcarrier signal results without use of expensive output stage devices in the subcarrier signal generator.

Amplitude and phase error normalization of subcarrier generator

An improved method and apparatus for automatically tuning an antenna includes adaptive antenna tuning based on a current radio reception frequency and on prior antenna tuning cycles to establish a predictor value. The predictor value establishes an antenna tuning voltage sub-range most likely to contain the optimum antenna tuning voltage, but is a smaller range than the full antenna tuning voltage range. The antenna tuning voltage sub-range is then traversed while monitoring a signal strength indicator to identify an antenna tuning voltage providing optimum tuning conditions. Because only a sub-range of the full antenna tuning voltage range need be traversed, by virtue of the predictor value, relatively small increments in antenna tuning voltage may be used in traversing this sub-range. As a result, the execution time and accuracy of the antenna tuning method of the present invention is improved relative to prior automatic antenna tuning methods.

Adaptive automatic antenna tuning method and apparatus

A time variant frequency correction technique uses a frequency conversion circuit to obtain an intermediate frequency and an adjusted local oscillator frequency from an input signal frequency, a local oscillator frequency and a reference oscillator frequency. The intermediate frequency and adjusted local oscillator frequency are simultaneously counted during a period determined by the reference frequency. The resulting counts are used to calculate the input frequency independent of time variations in the local oscillator frequency for display on a display device.

Time variant frequency correction technique

A resonator is initially charged by applying a drive signal offset from the expected resonant frequency of the resonator for a selected period of time. After the drive signal is removed from the resonator a period counter is used to count the period of the output signal of the resonator as it rings down. For low-Q resonators an amplifier is included to amplify the resonator output signal before being applied to the period counter to increase the number of cycles of that signal which are within the dynamic range of the period counter.

Method and apparatus for measuring the resonant frequency of a high Q

A constant amplitude, variable-bandwidth filter is provided having a variable resistor and a high-Q passive filter cascaded between a pair of amplifiers. The input amplifier having a low output impedance and the output amplifier having a low input impedance. As the resistance of the variable resistor is varied, the Q of the system varies and thus its bandwidth. The gain of the system also varies as the variable resistor is varied. To compensate for the gain variation, a current, equivalent to the value of the output voltage of the input amplifier divided by the value of the equivalent series resistance of the high-Q passive filter, is inserted at the node where the variable resistor and the high-Q passive filter are coupled one to the other. This results in a constant current at resonance being conducted by the high-Q passive filter, independent of the selected overall bandwidth of the filter.

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Aloha, OR, United States of America

James D English