A radio transceiver has a single reference oscillator and a receiving frequency synthesizer and a transmitting frequency synthesizer. The synthesizer frequencies are selected so that the receiving intermediate frequency and a transmitting intermediate frequency (produced by the transmitted frequency mixing with the received frequency) are spaced widely apart. Thus, any beat note between the two intermediate frequencies is outside the passband or filter bandwidth in the receiver circuit.
A cell enhancer for use by one cellular provider in a cellular radio-telephone system particularly in a cell including a diversity function includes a first amplifier system for amplifying both up-link and down-link signals between a first set of upstream and downstream antennas and a second amplifier system for amplifying at least the up-link signals between a second set of upstream and downstream antennas. The upstream antennas have a selected minimum correlation between them to ensure that the diversity at the cell site is maintained.
It is desirable that a cordless telephone system include a single base unit and at least two remote handunits. With such a system, two users may maintain participation in a three-way conversation while being free to move about within reasonable transmitting distance to and from the base unit. Circuitry is provided in which a signal received from one handunit is transmitted to the other handunit, and sidetone from one handunit is transmitted back to that handunit.
A mobile station equipment for a mobile radio telephone system uses a voltage-controlled, temperature-compensated crystal oscillator (VC-TCXO) as a reference oscillator for local oscillators in frequency converters which convert an RF signal into IF signals. The oscillation frequency of the VC-TCXO is controlled by counting the second IF information and evaluating its difference from a certain reference value. At reception, the local oscillators have their reference frequency stabilized based on the stable frequency information from the base station. The equipment is compact and has reduced power dissipation and lower manufacturing cost.
A circuit for alternately providing a first frequency to a receiver stage (20) and a second frequency to a transmitter stage (25) of a transmitter and receive circuit (11). The circuit comprises an oscillator (38), a first switch (33), a second switch (42), and a control circuit (29). The first switch (33) couples information to the oscillator (38) to be transposed on the second frequency during transmission. The second switch (42) couples the oscillator (38) to either the transmitter stage (25) or the receiver stage (20). Prior to changing oscillator frequency the control circuit (29) disables both outputs of the second switch (42). The control circuit (29) alternately tunes the oscillator (38) to the first frequency and enables the second switch (42) such that the oscillator (38) is coupled to the receiver stage (20) and tunes the oscillator (38) to the second frequency, enables the first switch (33), and enables the second switch (42 ) such that the oscillator (38) is coupled to the transmitter stage (25).
It is desirable that a cordless telephone system include a single base unit and at least two remote handunits. With such a system, two users may maintain participation in a three-way conversation while being free to move about within reasonable transmitting distance to and from the base unit. Circuitry is provided in which the signal received from one handunit is transmitted to the other handunit, and sidetone from one handunit is transmitted back to that handunit. The base unit comprises first and second double conversion intermediate frequency arrangements with respective first IF frequency portions being tuned away from a nominal frequency value by a substantially equal amount in opposite directions.
