A time shared power amplifier for amplifying first and second modulated carrier signals for transmission. The carrier signals are modulated by first and second data signals, respectively. The first and second signals are characterized by bursts of data separated by periods of silence. If either of the data signals is presented for transmission while the other is being transmitted, the later one is stored in a storage buffer until the earlier one has been transmitted. Thus, each signal is transmitted during the other's silent periods, and since only one carrier is being transmitted at any given time a much smaller amplifier can be used to amplify the carriers to a given power level than would be required if both carriers had to be transmitted at once.

Time shared very small aperture satellite terminals

A radio communication device, suitable for use in a portable computer, is capable of operating at any one of a set of common frequencies which are legally permissible in all countries (or a set of countries) and at any frequency on which it detects that a transmission of its own type is being used for a transmission from another device. Thus, users can legally operate the device in different countries, while manufacturers can obtain certification for use in those countries. If the user attempts to select a frequency which is not one of the common frequencies nor detected by transmission, an indication that such frequency is not available is provided to the user.

Radio communication device and method

A transmitter using a dual conversion system which effects frequency conversion twice has a local oscillator (113) for generating a first local oscillation signal, a multiplier (118) for multiplying the frequency of the first local oscillation signal to produce a second local oscillation signal, a first mixer (115) for mixing the first local oscillation signal and first IF signal to produce a second IF signal, and a second mixer (120) for mixing the second local oscillation signal and second IF signal to produce a signal to be transmitted. A voltage controlled filter (116) whose center frequency varies with the frequency of the first local oscillation signal is connected to the output of the first mixer (115).

Dual conversion transmitter

A radio frequency receiver front-end includes a low noise amplifier, a mixing stage, and a selectable channel filter. The low noise amplifier is operably coupled to amplify inbound RF signals to produce amplified inbound RF signals. The mixing stage is operably coupled to mix amplified inbound RF signals with a 1st local oscillation to produce a 1st intermediate frequency (IF) signal. The selectable channel filter is operably coupled to pass a 1st channel of the 1st IF signal when a channel select signal is in a 1st state and to pass a 2nd channel of the 1st IF signal when the channel select signal is in a 2nd state to produce a selected channel.

RF transmitter and receiver front-end

A transmitter control system for transmitters having means for selectively switching one channel to another in the multiple channels and means for controlling the transmitter output so as to deactivate, activate and reduce the transmitter output. The system comprises comparator means for comparing a start signal from the transmitter output control means with a detected signal of the transmitter output, the output of the comparator means being adapted to selectively drive at least one of the channel switching means for switching channels and a transmitter power reduction control circuit included in the transmitter output control means upon occurrence of a detected signal of the transmitter output indicative of a failure of the transmitter.

Transmitter control system

A voltage variable filter circuit useful, for example, in a radio frequency transmitting device and having a center frequency which is changeable with changes in an applied voltage employs one or more voltage variable reactive elements in the filter in conjunction with circuitry for changing the direct current voltage across such reactive elements to change the reactance thereof and therefore also change the center frequency of the filter. To extend the range of filter variation, additional reactance may be selectively introduced into the filter circuit. In the environment of a multi-channel radio frequency transmitting device, a selector switch simultaneously selects one radio frequency channel for transmission and a unique voltage source for application to the voltage variable reactance so that the filter is appropriately tuned for the selected channel.

Lowell G. Atkinson

Papers

Multi-channel R.F. transducer with channel selector coupled to selected channel filter