US 5,432,473 AGranted

Dual mode amplifier with bias control

AssigneeNokia Mobile Phones Ltd.

InventorsHeikki Mattila, Jorma Matero, Hannu Pakonen

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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. When the mode signal is "on" or present it signifies that the digital transmission mode is to be employed. When the mode signal is " off" or at zero level, it indicates that the analog transmission mode is to be employed. The bias control circuit provides three bias signal outputs, V.sub.b1 applied to the driver amplifier, and V.sub.b2 and V.sub.b3, applied to the power amplifier. The levels of V.sub.b1, V.sub.b2 and V.sub.b3 are varied for the analog and digital transmission modes.

Claims7

Dependent claims

An amplifier structure for a dual mode signal transmission system of the type wherein modulated signals are transmitted in a digital or analog transmission mode comprising:

a gain control means responsive to a modulated signal for varying the amplitude of said modulated signal,
an amplifier circuit means including a plurality of amplifier stages connected to the output of said gain control means for amplifying said modulated signal,
an antenna output terminal connected to said amplifier circuit means for coupling said modulated signal to a transmission antenna,
a source of voltage Vpwr representative of the desired signal level for the modulated signal coupled to said antenna output terminal,
a feedback circuit means connected to the said antenna output terminal, said source of voltage Vpwr and said gain control means for comparing the level of said modulated signal and the level of said Vpwr signal and providing a difference signal value exclusively to said gain control means
and a bias control signal means having first and second input terminals and a plurality of output terminals, said first input terminal being connected to said source of Vpwr signal, said second terminal being connected to a dual state mode signal, and said plurality of output terminals being connected exclusively to said amplifier means,
wherein said bias control means is responsive to said Vpwr signal and to said dual state mode signal in a first state for producing bias signals on said plurality of output terminals for biasing said amplifier means at first bias levels for analog mode transmission, and said bias control means is responsive to said Vpwr signal and to said dual state mode signal in a second state for producing bias signals on said plurality of output terminals for biasing said amplifier means at second bias levels for digital mode transmission.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/092,245Filed 14 Jul 1993
Granted: 11 Jul 1995
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

H03F 1/302
Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters: in bipolar transistor…
H03F 3/72
Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements: gated amplifiers, i.e. amplifiers which are rendered…
H03G 3/3042
In high-frequency amplifiers or in frequency-changers: in modulators, frequency-changers, transmitters or power amplifiers
H04B 2001/0416
With power amplifiers: having gain or transmission power control