Nokia Mobile Phones Limited

Nokia-mobira Oy

Risto Vaisanen

Jukka Sarasmo

Vesa Pekkarinen

Aki Leppanen

Peter Lussenhop

Method and circuit arrangement for reducing offset voltage of a signal

The present invention relates to the extension of the RSSI range of a radio transceiver, in which the RSS value is monitored continuously during reception by a limiter circuit (1). This extension is performed by switching into the operating state of attenuation components (3, 4) which are already present in the receive path of the radio transceiver and in addition to an attenuation function have at least one further function required for operating the radio transceiver. Furthermore, a method is specified by means of which the additional attenuation of such a component (3, 4) which can be switched over can be established and stored in the radio transceiver.

Method for extending the RSSI range and radio transceiver operating in

The invention relates to processing of radio frequency signals, particularly to the balancing of signals. The phasing and balancing member according to the invention is based on the use of four parallel strip lines (10, 20, 30, 40). The strip lines are combined as two pairs (10, 40; 20, 30), which are located within each other. In the line pair (20, 30) connected the unbalanced signal the other ends (22, 32) are interconnected, and in the line pair (10, 40) connected to the balanced signal the other ends (12, 42) are connected to a point corresponding to the signal's zero potential. In the different lines of each pair the signal travels in opposite directions, whereby the radiation fields generated by the signals travelling in the different lines substantially cancel each other. Preferably capacitive members (50, 60) are further connected to those ends (14, 44; 24, 34) of the strip line pairs which are connected to the signals, whereby each strip line pair in combination with the capacitive member connected to it forms a resonance circuit.

Series of strip lines for phasing and balancing a signal

A method of generating the different frequency signals required in transmission and reception in a digital radio telephone for operation on at least two different frequency bands. According to the method the mixing frequencies (F1, F2) are selected so that from the frequencies obtained as the mixing results it will always be possible to select the intermediate frequencies (IF1, IF2) required in reception and the transmission frequency (FTX) required in transmission for a radio telephone operating on the desired frequency band.

Method to generate different frequency signals in a digital radio

A booster (2) of a digital portable radio telephone (1) is connected to a connector (11) by arranging a switch (9) in the control signal (TXC-DA) path, said switch changing, under the control of a logic control signal (BST), the power control circuit signal (TXC) of the portable radio telephone into a fixed signal (V.sub.bst). As a result, a transmit signal of constant power is led to the booster amplifier to be amplified to the level of the control signal (TXC-DA). Similar power control circuits (4,14) are arranged in the portable radio telephone and in the booster amplifier, whereby the properties of the transmit pulse are preserved in booster use.

Circuit for controlling the transmit power level in a booster amplifier

In a method according to the invention the tuning information determined by a measuring computer (20) is stored in the memory of the radio telephone (1). In operation the microprocessor (10) receives from the sensors (14) information e.g. about the temperature, according to which it selects from its memory tuning data and adjusts signal levels and deviations through logic controlled amplifiers (16, 17). The tuning can be made automatically, without opening the casing of the radio telephone.

Logic controlled tuning signal level and deviation compensation in a

In the simplified diode mixer according to the invention the transformer supplying the local oscillator signal is replaced by a circuit means that prevents build-up of a d.c. voltage at the terminals of the mixer diodes (3, 4). The circuit means can be e.g. a coil (5), a strip line, or a diode pair. The filters (1, 2) for the signals to be mixed are realized as band-pass filters. The mixer is used e.g. in a GSM mobile phone.

Transformerless diode mixer

In the method of tuning the received signal strength indicator the tuning results for selected operating conditions are stored in the microprocessor (10) memory. When the radio telephone (1) is in use, the received signal strength indicator (RSSI) reading is corrected with the tuning result in order to select the strongest antenna signal. The tuning is performed by connecting the tuning equipment (2)to the external interfaces (31, 32) of the radio telephone without opening it.

Method of tuning and compensating the received signal strength indicator

Radio telephone tuning information is determined by a measuring computer (20) stored in the memory of the radio telephone (1). A microprocessor (10) receives from the sensors (14) information about the operating temperature, according to which appropriate tuning data is selected from memory. The information is used to adjust signal levels and deviations through logic controlled amplifiers (16, 17). The tuning can be made automatically without opening the casing of the radio telephone.

An IQ modulator/demodulator wherein the 90.degree. phase quadrature branches of an input signal are connected to different terminals of a common bridge, from which also the quivalents I and Q signals are obtained. To the bridge is also connected a local oscillator signal through a transformer. The transformer can be replaced with an active circuit, whereby the entire demodulator can be implemented in the form of an integrated circuit.

I/Q modulator and demodulator having a single bridge

The present invention relates to an offset voltage zeroing method of a D/A converter, with the aid of which oscillations of the output voltage of said D/A converter can be radically reduced. An output signal of the converter is carried to a first terminal of a capacitor (5). A second terminal of the capacitor is coupled to a reference voltage (V.sub.ref) with a controllable switch (6) as long as there are no pulses in the output of the converter. As a result, an amended output signal is obtained from the second terminal.

Method for amending the effect of offset voltage variations from the

The present invention concerns a circuit for forming low power levels in a transmitter of a radio telephone. By a power amplifier (1) of the transmitter is formed the maximum power level and a plurality of lower power levels. As taught by the invention, very low power levels can be produced by controling the power of the RF signal leaking through the power amplifier (1) when said signal is not amplified by the power amplifier. For controlling the leakage power, a PIN diode attenuator (4) connected before the power amplifier (1) is used.

Circuit for forming low power levels in a transmitter of a radio

An automatic gain control circuit (AGC) in a receiver for a digital radio telephone. Most of the total gain control of the received signal is accomplished in the base band frequency sections, i.e. in the I and Q branches, where the signal amplification is controlled step by step, and only a minor part of the total gain control is performed in the RF stage. High amplification steps are formed with amplifiers (9a, 10a, 11a, 12a; 9b, 10b, 11b, 12b), wherein the desired amplifier is activated with a digitally controlled (A, B) multiplexer (13a, 13b), and low amplification steps are formed with a resistance attenuator (14a, 14b), in which a signal of desired level is selected by a digitally controlled (C, D, E) multiplexer (15a, 15b). In addition, the RF amplifier (2) has two amplification levels and the desired amplification is selected with a digital control (F). With the different digital control combinations (A, B, C, D, E, F) the entire gain control range required of the receiver can be covered.

Automatic gain control circuit in a radio telephone receiver

In a method and apparatus according to the invention the tuning information determined by a measuring computer (20) is stored in the memory of the radio telephone (1). When the radio telephone is in operation the microprocessor (10) receives from the sensors (14) information e.g. about the temperature, and it selects from its memory tuning information, with which the transmitter (11) power is controlled via a D/A-converter (15). The tuning can be made automatically, without opening the casing of the radio telephone.

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Salo, Finland

Risto Vaisanen