Novatel Communications Ltd.

Kovatel Communications, Ltd.

Glyn Roberts

Kiomars Anvari

Gordon Paynter

Remesh B Krishnasastry

A selection system in a space diversity system of a mobile receiver combines the ultra high frequency signals after they have been frequency shifted to an intermediate frequency. The system combines the intermediate frequency signals depending on the ratio of the magnitudes of these signals. If the ratio of the magnitude of the received signals is equal to or greater than a preset magnitude level, for example, 5 db, a control unit selects only the received signal having the largest magnitude. Otherwise, the control unit linearly combines both received signals Specifically, if the absolute value of the difference in received phase signals is less than 90.degree., the output of a phase detector causes the control unit to pass both received signals to a summer that linearly combines them prior to demodulation. Otherwise, the control unit inverts the phase of one of the received signals prior to passing both received signals to the summer.

Selection circuit in a space diversity reception system for a mobile

A receiver suitable for use in a radio-telephone system for recovering data from encoded, quadrature-modulated communication signals employs a feedback arrangement for suppressing cross-talk between the receiver's in-phase and quadrature channels to improve data recovery rates during decoding. The receiver converts in-coming analog communication signals into in-phase and quadrature digital signals, which may have cross-talk components. The receiver has an attenuator for subtracting feedback signals from the in-phase and quadrature digital signals to produce cross-talk-attenuated in-phase and quadrature digital signals, a decoder for decoding the cross-talk-attenuated in-phase and quadrature digital signals to generate first and second data output signals, and the above-mentioned feedback arrangement, which preferably employs a recoder and cross-correlation techniques, for generating the feedback signals.

Receiver employing correlation technique for canceling cross-talk

In a digital radio-telephone receiver, an open-loop arrangement for generating a received-signal-strength-indicating ('RSSI') value suitable for use in mobile assisted hand-off within a cellular telephone system. The receiver has an amplifier for amplifying a received signal with a gain controlled by a gain-control signal, and an automatic-gain-control circuit ('AGC') responsive to the amplitude of the amplifier output and coupled in a feedback-loop for applying an AGC signal to the amplifier as the gain-control signal. An RSSI value is generated by (i) opening the AGC feedback loop so that the AGC output signal is not applied to the amplifier, (ii) applying a ramp signal of increasing amplitude to the VGA while the AGC monitors the signal envelope, and (iii) when the signal envelope passes a pre-selected threshold, applying the then-occurring ramp-signal value to a calibrated look-up table to obtain the corresponding RSSI value stored therein. Preferably, the receiver also employs a digital multiplexer ('MUX'), which provides to the amplifier as the gain-control signal, in response to a select signal, the ramp signal during a first period of time, and the AGC signal during a second period of time.

Cellular radio-telephone receiver employing improved technique for

A voltage-controlled oscillator includes a compensating signal value calculator which calculates the value of a function representing the portion of the oscillator temperature-frequency transfer curve corresponding to the ambient temperature. A signal corresponding to the calculated value is then applied to the voltage-controlled oscillator as the control voltage. Basically, an oscillator temperature-frequency transfer curve is partitioned into n segments. For each segment an offset value, x.sub.n, equal to the difference between the frequency at the start of the segment and the desired frequency, is stored in a look-up table. When a compensating signal value is required, the compensating signal value calculator retrieves from the look-up table the x.sub.n values corresponding to the segment immediately preceding and succeeding segment k, segments 'k-1' and 'k+1'. The retrieved values are labeled x.sub.k, x.sub.k-1, and x.sub.k+1, respectively. It then calculates a function representing the portion of the transfer curve passing through three points corresponding to the values: ##EQU1## The compensating signal value is then calculated by substituting the actual delta T value into the equation. If the oscillator output frequency has shifted due to aging of the crystal, an aging offset value, x.sub.A, is added to the equation, and the compensating signal compensates for frequency variations related to both temperature and aging.

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Calgary, Canada

Glyn Roberts