Abstract: A circuit is provided for use in a dual mode mobile phone for selectively one of phase modulating or frequency modulating an RF signal. The circuit includes an IQ generator for generating one of first quadrature waveshapes or second quadrature waveshapes in response to a modulating signal; a quadrature mixer for mixing the first quadrature waveshapes or the second quadrature waveshapes with an RF signal to generate a phase modulated RF signal or a frequency modulated signal, respectively; and a limiter, such as at least one limiting amplifier, that has an input coupled to an output of the quadrature mixer for reducing an amplitude modulation component of only the frequency modulated signal. The at least one limiting amplifier has an input coupled to a limit control signal that has a magnitude selected for setting a dynamic range of the at least one limiting amplifier. The phase modulated signal may be a .pi./4-DQPSK signal.

Abstract: Disclosed are various embodiments of circuitry for coupling first and second transceivers of a dual band radio telephone to integral and external antennas. The circuitry uses impedance matching lengths of transmission lines and switches arranged to provide a minimum insertion loss. Also disclosed is an embodiment for use with a single band radio telephone, such as a digital TDMA radio telephone that either transmits or receives at any given time. Also disclosed is an antenna switching arrangement for a dual band phone that eliminates a requirement for duplexers.

Abstract: Disclosed is a transmitter circuit (14) for use in radio telephone (10), the transmitter circuit including a power amplifier (17D) having an output coupled to an antenna (12) for transmitting an amplified modulated RF signal; a variable gain driver amplifier (17C) having an output coupled to an input of the power amplifier and an input coupled to an output of a modulator (14A), the variable gain driver amplifier being required to output the modulated RF signal within a predetermined dynamic power range having a maximum value; and at least one programmable gain amplifier (PGA1, PGA2) coupled in series between the output of the modulator and the input of the variable gain driver amplifier. The at least one programmable gain amplifier has a dynamic range selected for reducing the dynamic range requirement of the variable gain driver amplifier to be less than the predetermined dynamic power range.

Abstract: A method of controlling an external radio frequency amplifier of a radio telephone and a control system therefore. The power amplifier of the transmission side of the radio frequency amplifier is controlled to turn on and off, on the basis of at least one control signal (BENA1, BENA2) entering the radio frequency amplifier separate from a signal to be transmitted from the radio telephone. The control signal (BENA1, BENA2) contains information about the starting and ending instant of transmission.

Abstract: A dual-mode radiotelephone terminal includes a .pi./4-shift DQPSK modulator (11). A dual-mode modulation is achieved by mixing an output of a transmitter oscillator (16) with an output of an offset oscillator (18) to form an injection signal (LO) at a final transmitter frequency, the injection signal being further modulated with a quadrature modulator in a digital mode of operation. In an analog mode of operation the transmitter oscillator or the offset oscillator is frequency modulated and the quadrature modulator is disabled with a bias signal, thereby passing the frequency modulated injection signal without substantial attenuation. The LO signal is regenerated and also phase shifted with a circuit (35) having a frequency multiplier (30) and a frequency divider (34). The circuit outputs two local oscillator (LO) signals (LOA and LOB), each of which directly drives an associated quadrature mixer (36, 38) of the modulator.

Abstract: A dual mode transmitter with bias control is described wherein an RF signal from a system modulator is fed to a gain control circuit, which can be either a voltage controlled amplifier or attenuator. The ultimate transmitter output power level depends on the attenuation/gain of the gain control circuit. The output signal from the gain control circuit is fed to a driver amplifier which amplifies the signal and feeds it to a power amplifier circuit, which may be comprised of several stages of bipolar transistors or GaAs FETs. The modulated signal to be transmitted is then fed from the power amplifier circuit through a coupler to an antenna terminal. The coupler is connected to an RF detector and is used for RF level monitoring. The Rf level signal from the RF detector is applied to a comparator circuit. An improved combination is provided by incorporating a bias control circuit. A Vpwr signal is applied as one input to the bias control circuit and a mode signal is applied as the other input.

Abstract: A dual-mode radiotelephone terminal includes a .pi./4-shift DQPSK modulator (11). A dual-mode modulation is achieved by mixing an output of a transmitter oscillator (16) with an output of an offset oscillator (18) to form an injection signal (LO) at a final transmitter frequency, the injection signal being further modulated with a quadrature modulator in a digital mode of operation. In an analog mode of operation the transmitter oscillator or the offset oscillator is frequency modulated and the quadrature modulator is disabled, thereby passing the frequency modulated injection signal without substantial attenuation. The LO signal is regenerated and also phase shifted with a circuit (35) having a frequency multiplier (30) and a frequency divider (34). The circuit outputs two local oscillator (LO) signals (LOA and LOB), each of which directly drives an associated quadrature mixer (36, 38) of the modulator.

Abstract: Structure and technique, for calibrating a vector modulator that does not require a network analyzer, are disclosed which are incorporated in a vector modulation system comprising a standard vector modulator circuit including means for shifting phase to adjust the relative phases of the I and Q components of the modulated RF carrier. Means for attenuating are included in the I and Q modulation system to adjust the relative amplitude of the modulation signals. The disclosure describes a technique wherein the microwave transmitter's I and Q phase difference is measured by measuring the power levels of the I and the Q signals. The power levels are compared and a correction value is stored in a read-only memory to compensate for the error.

Abstract: Electronic apparatus generates first and second output signals having a quadrature phase relationship therebetween. A local oscillator signal with a reference phase is applied as an input to first and second signal branches. The second signal branch includes a phase control circuit for subjecting input signals passing therethrough to a determined phase shift. The phase control circuit is responsive to an applied DC control signal to adjust any phase shift error through the phase shift circuit from a predetermined phase shift to assure that the second output signal exhibits the required quadrature phase relationship to the first output signal. A memory/microprocessor combination stores a digital value that is indicative of a DC control signal which must be applied to the control circuit to alter the phase shift through the phase control circuit to the predetermined phase shift. The microprocessor accesses the digital parameter and applies it to the phase control circuit through a digital to analog converter.