Abstract: A communication system for a vehicle is provided. The system includes a transmitter, first and second antennas and a splitter. The transmitter outputs transmission signals. The second antenna is spaced from the first antenna to provide spatial diversity between the transmission signals radiated out by the first and second antennas. The splitter has an input that is in communication with an output of the transmitter. The splitter has a first output that is in communication with the first antenna and a second output that is in communication with the second antenna. The splitter is configured to provide an unequal passive power splitting between the first output and the second output of the splitter.

Abstract: A method for air to ground uplink synchronization comprises initiating a downlink synchronization of user equipment onboard an aircraft with a ground base station; computing a range to the base station based on a downlink path loss; selecting an initial time advance (TA) value from a set of predetermined TA values based on the range; and sending a first random access channel (RACH) request with the initial TA value to the base station in a first attempt to synchronize an uplink signal and attach the user equipment to a network. If the user equipment fails to attach, a next RACH request is sent with a next TA value to the base station, in a next attempt to synchronize the uplink signal and attach the user equipment to the network. If the user equipment fails again to attach, the method is repeated until the user equipment is attached to the network.

Abstract: A method for air to ground uplink synchronization comprises initiating a downlink synchronization of user equipment onboard an aircraft with a ground base station; computing a range to the base station based on a downlink path loss; selecting an initial time advance (TA) value from a set of predetermined TA values based on the range; and sending a first random access channel (RACH) request with the initial TA value to the base station in a first attempt to synchronize an uplink signal and attach the user equipment to a network. If the user equipment fails to attach, a next RACH request is sent with a next TA value to the base station, in a next attempt to synchronize the uplink signal and attach the user equipment to the network. If the user equipment fails again to attach, the method is repeated until the user equipment is attached to the network.

Abstract: A method of estimating Doppler shift for air to ground communications comprises obtaining an initial position of an aircraft during flight, wherein the aircraft includes an onboard database with stored positions for a plurality of ground station towers; when a subsequent position of the aircraft nears a stored position of a closest ground station tower, requesting a Doppler shift estimation for the closest ground station tower; obtaining a current position of the aircraft when requesting the Doppler shift estimation; defining an aircraft position vector from the initial position to the current position; defining a tower position vector from the initial position to the stored position; subtracting the aircraft position vector from the tower position vector to determine an aircraft to tower position vector; differentiating the aircraft to tower position vector with respect to time to determine a velocity magnitude to the closest ground station tower; and calculating a Doppler shift.

Abstract: Symbol decoding errors at a receiver utilising a flash analog to digital converter (ADC) can be reduced by adjusting a reference voltage level of the ADC where a decoding error rate at the reference voltage level exceeds a threshold.

Abstract: Symbol decoding errors at a receiver utilising a flash analog to digital converter (ADC) can be reduced by adjusting a reference voltage level of the ADC where a decoding error rate at the reference voltage level exceeds a threshold.

Abstract: Provided by the invention is a fast, continuously variable AGC that can be used to control the gain of an optical amplifier. The AGC is designed around a controller having control coefficients that may be dynamically adjusted according to operating conditions. According to an embodiment of the invention provided is an AGC that can operate at much higher speeds in comparison with prior art AGC designs that have fixed control coefficients, while simultaneously maintaining stability over all operating conditions.

Abstract: In a method and apparatus for tracking dynamic characteristics of an optical amplifier, optical signal probes are used to determine the gain and the corner frequency of the optical amplifier. A first optical probe having a predetermined modulation frequency above an expected corner frequency of the amplifier is used to estimate the gain of the optical amplifier. A second optical probe signal having a second predetermined modulation frequency at or below the expected corner frequency of the amplifier is used to estimate the corner frequency. These parameters can be used to optimize gain control of an optical amplifier.

Abstract: In a method and apparatus for tracking dynamic characteristics of an optical amplifier, optical signal probes are used to determine the gain and the corner frequency of the optical amplifier. A first optical probe having a predetermined modulation frequency above an expected corner frequency of the amplifier is used to estimate the gain of the optical amplifier. A second optical probe signal having a second predetermined modulation frequency at or below the expected corner frequency of the amplifier is used to estimate the corner frequency. These parameters can be used to optimize gain control of an optical amplifier.

Abstract: A radio transceiver system uses a single variable local oscillator frequency source which is used in mixing both before and after a band-pass filter. This causes a reduction in band-pass filter bandwidths. In an all-band transceiver for PCS for example the effect of this reduced bandwidth requirement is to increase the spacing between the transmit bands and the receive bands and thereby enable a reduction in transmission noise interfering with the reception bands.

Abstract: A self balancing matrix amplifier is provided in which a plurality of input signals are divided with an input transform matrix, amplified by a number of amplifiers, and recombined with an output transform matrix to form amplified versions of the input signals. One of the inputs is set aside as a monitor input, and this is connected to the characteristic impedance of the system. The output corresponding to this input is monitored for gain imbalances which should be zero if the entire matrix amplifier is perfectly balanced. Then, on the basis of the monitored phase and gain imbalances, attenuators and phase adjusters in series with each of the amplifiers are iteratively controlled so as to insert phase shift or gain/loss so as to reduce the monitored phase and gain imbalances.