Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: The present invention concerns a circuit processes the power signal emitted from an RF power sensor (SK) of a radio telephone to create a detector voltage which is proportional to the power level of the radio telephone transmitter. The circuit comprises a transistor (Q2) acting as an active rectifier, which in the ascending part of the positive half cycle of the power signal charges a capacitor (C3). During the descending part of the power signal the capacitor starts to discharge with a time constant which is remarkably greater than the cycle length of the power signal. The transistor is biassed by means of a transistor (Q1) so that it is conductive even at the lowest power levels.

Abstract: A circuit for forming low power levels in a radio telephone transmitter in which high power levels are produced in a controllable amplifier stage (1), for instance in a class-C power amplifier. According to the procedure, a RF signal is before the amplifier stage (1) divided into two branches in a power divider (4), in one of which the Rf signal is conducted to said amplifier stage (1) for forming high power levels, and in the other branch the RF signal is conducted to an element (5) by which low power levels are produced, and said branches are combined in the output (RFout) of the transmitter. The element (5) may be a PIN diode attenuator.

Abstract: The invention relates to the forming of a control pulse for the transmitter in a GSM radio telephone system. A cos.sup.2 pulse is formed by means of an analog circuit from a rectangular pulse which is first shaped into a triangular pulse which may be somewhat clipped at its peak. The triangular pulse is further shaped into a cos.sup.2 pulse. The circuit also includes the selection of the abruptness of the triangular pulse and, thereby, the abruptness of the cos.sup.2 pulse.

Abstract: In a digital radio telephone transmitter an output pulse with e.g. cos.sup.2 -shaped edges is produced by a voltage controlled power amplifier (4). When known control loop circuitry is used, the power (Pout) of the output pulse will rise almost step-wise at the beginning of the pulse, which leads to the spreading of the spectrum and to rise time delays of the output pulse with respect to the control pulse (TXC) at different power levels. According to the invention a good cos.sup.2 -shape of the output pulse (Pout) and its tracking of the control pulse (TXC) almost without delay is achieved so that a squarewave pulse (V.sub.p) is added to the control voltage (V2) of the power amplifier (4), the pulse (V.sub.p) starting and ending substantially at the same time as the control pulse (TXC). In a preferred embodiment the squarewave pulse (V.sub.p) is added to the control voltage (V2) only during that time when the control voltage (V2) is below that value, at which the control loop begins to operate.

Abstract: An RF connector for connecting a radiotelephone (1) to an external antenna, whereby the telephone and a corresponding device rack (2) are connected to the external antenna by two pairs of matching metal plates (1a, 2a, 1b, 2b) that provide a capacitive two-wire connector-interface. In order to avoid too large a size and too high an attenuation, a coil (3a, 3b) is connected in series with the pair of plates (1a, 2a; 1b, 2b) constituting each capacitor. The coil and capacitor are dimensioned so that they form a resonant circuit with an attenuation of nearly 0 at the desired transmission frequency. A first balancing transformer (4) before the resonant circuit transforms the signal into a balanced signal, and a second balancing transformer (5) after the resonant circuit transforms the signal back to an unbalanced signal to be transmitted further on a coaxial cable.

Abstract: The invention relates to an RF-shielded hybrid circuit which comprises a printed circuit board (1) of an insulating material, with foils on both sides, components placed on one side of the printed circuit board, and an RF-shield housing (5) made of metal sheet and fitted around at least part of the circuit. It is the object of the invention to provide an RF-shield which can be manufactured automatically and which at the same time ensures a relatively simple and compact structure. In order to achieve this, the RF-shield for the circuit is made up on the one hand of a cup-like cover (5) the peripheral area of which extends substantially around the edge of the printed circuit board (1), with the exception of the area of the connectors (2) of the printed circuit board, and which is placed over the components, and on the other hand of an earth foil (2a) which faces away from the components of the printed circuit board and is soldered by its edge to the peripheral area (5a) of the cover (5).