Nokia Corporation

Nokia Mobile Phones Limited

Markus Pettersson

Jarmo J Heinonen

Simo Murtojarvi

Harri Kimppa

Sami Vilhonen

Kjell Östman

Sami Vihonen

Kari Vigelius

The invention relates to a calibration method and a calibration arrangement for an active filter intended to be used especially in portable radio apparatus. The filter () according to the invention is an active RC filter and it is integrated except for one or more of its capacitances or one or more of its resistances. Advantageously the highest capacitance or the highest resistance is left unintegrated. When using an external capacitance, the principle of the calibration is as follows: The integrated resistances are corrected using a common coefficient such that the external capacitance together with the integrated resistances produces the correct time constants (). Then the integrated capacitances are corrected using a common coefficient such that they together with the internal resistances that were corrected in the previous phase produce the correct time constants (). If the filter comprises multiple circuit stages, the two-phase calibration process described above is repeated for each circuit stage.

Method and arrangement for calibrating an active filter

A circuit arrangement that stacks a modulator and automatic gain control (AGC) amplifier so as to re-use the modulator output current to drive the AGC amplifier, thereby saving power consumption and avoiding an unnecessary signal transformation between the two stages. A balanced circuit topology is used. The modulation signal can be selected over a wide range (100 MHz to 5.4 GHz) and the circuit arrangement is therefore particularly suitable for wireless applications (e.g. GSM-EDGE) and for integrated circuit fabrication.

Stacked modulator and automatic gain control amplifier

Disclosed is a method for operating a mobile station () that includes an RF receiver () having an RF front end (A) followed by a base band section (B). The base band section includes an AGC block (') that contains a DC blocking capacitor (C) coupled in series between an input node (Vin) of the AGC block and an input to a gain element (A). The method has steps of tuning from a current RF channel to another RF channel to make a signal strength measurement, and reducing a time constant of the AGC circuit by shorting around the DC blocking capacitor. Also disclosed is a method for operating the mobile station where the base band section includes the AGC block that contains an AC coupling capacitance coupled in series with a first resistance (R) between an input node of the AGC block and an input to the gain element. This method has steps of operating the AC coupling capacitance and the first resistance as a first order low pass filter for attenuating the AC value of an input signal, and closing at least one switch for switching in additional capacitance and resistance for transforming the first order low pass filter to a second order low pass filter for increasing the attenuation of the AC value of the input signal. In these various embodiments circuit topologies are described for both inverting and non-inverting operational amplifier implementations.

Direct conversion receiver architecture

The invention relates to a phase-locked loop structure providing local oscillator signals. In order to enable an improved supply of local oscillator signals, the phase-locked loop structure comprises a first phase-locked loop including a first voltage controlled oscillator and a second phase-locked loop including a second voltage controlled oscillator. A first local oscillator output provides a first local oscillator signal, wherein a signal output by the first voltage controlled oscillator is forwarded to the first local oscillator output. A second local oscillator output provides a second local oscillator signal. A selection component forwards a signal output by the first voltage controlled oscillator or a signal output by the second voltage controlled oscillator to the second local oscillator output. The invention relates equally to a corresponding communication unit and to a corresponding method.

Provision of local oscillator signals

A modulator having a high signal-to-noise ratio. The modulator comprises a switching arrangement and a driver arrangement coupled to the switching arrangement, said driver arrangement comprising driver components and among the driver components a low-pass filter arrangement. The modulator can be used, for example, in the transmitters of dual-band mobile stations without separate filters for each frequency band.

Growing community of inventors

Turku, Finland

Markus Pettersson