Abstract: 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 (100) 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 (1). 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 (2). If the filter comprises multiple circuit stages, the two-phase calibration process described above is repeated for each circuit stage.

Abstract: A communication device, such as a mobile telephone, has a digital signal processor, fast randomly accessible storage and relatively slow storage devices. Instructions are transferred from the slow storage devices to the fast storage devices for execution by the digital signal processor. The device is configure to operate at a full data rate or at a reduced data rate (usually half-rate) within a time division multiplex. Transmission data is stored in the fast storage device during reduced data rate operation. The device is configured to change from reduced data rate operation to full data rate operation, while maintaining communication. While processing previously stored half-data rate data, program instructions for the full data rate mode of operation are written to the fast storage means, while said data is being processed and thereby being removed from said storage means.

Abstract: The object of the invention is a method and a circuit arrangement for the processing of a signal in connection with its reception, when the signal conforms to one or more system specifications. The invention is preferably applied in receivers operating on two frequency ranges or in receivers intended to be used in two radio communication systems. Preferably the receiver is a part of a mobile station or a base station of a cellular system. An inventive idea is that before the analog-to-digital converter (324) the intermediate frequency signal (IF1, IF2) is processed on a wide band (310, 320) so that both the narrow band signal and the broadband signal are on the pass-band of the signal line. Then, when a narrow band signal is received, the signal also contains signals outside the band of the payload signal.

Abstract: The object of the invention is a method and a circuit arrangement for processing a spread spectrum signal and a frequency modulated signal. According to the invention the radio frequency signal is received (1, 2), the received signal is converted into an intermediate frequency signal (3, 4a, 4b), and then an intermediate frequency signal processing (6, 30, 31, 40) is made and the processed intermediate frequency signals are converted (32, 42a, 42b) into baseband signals. The signal derived from the received signal is converted (41) into a digital sampled signal which is processed (32, 42a, 42b, 111, 120, 121) digitally, whereby the either a signal derived from the received spread spectrum signal or a signal derived from the received frequency modulated signal, respectively, is selected (5) as the signal which is converted to the digital sampled signal.

Abstract: A/D and D/A converters are effectively utilized in a mobile phone, for example, by multiplexing the signals before the conversion. Both time division multiplexing and frequency division multiplexing can be used. When frequency division multiplexing is used, the IF signal (D) coming from the radio part and the baseband signal (A) coming from the microphone are summed (30) before the A/D conversion (31). The converted signal (K, L) is directed through filters (32, 34) in separate branches to digital signal processing (28). After that, the coded microphone signal (I, Q) is modulated (41, 42) to the intermediate frequency and added to the received, decoded baseband signal (M). The summed signal is directed to a D/A converter (45) and thereafter the signals are again separated by means of filters (46, 47). When time division multiplexing is used, the arrangement can also be used for measuring other signals of the mobile station.

Abstract: A digital radio communication system includes a receiver for receiving a signal stream that includes data frames, each frame including a data signal sequence and a synchronizing signal sequence. The communication system synchronizes the receiver by employing the signal stream. The receiver comprises: a sampling circuit for sampling symbol levels in the synchronizing signal sequence; cross correlation circuitry for comparing values derived from the sampled symbol levels with an expected set of values and producing an error value output; and correction circuitry that is responsive to the error output and produces a sample control output to the sample circuitry to alter the times of sampling of the symbol levels so as to reduce the error output and achieve time synchronization with the received synchronizing signal sequence. A further embodiment of the invention is described in relation to a CDMA receiving system.

Abstract: Disclosed herein are methods and apparatus for generating digital receiver and transmitter AGC values for a spread spectrum transceiver. A method includes the steps of (a) integrating the power of a received and sampled signal; (b) calculating a logarithm of the received integrated power; (c) subtracting a predetermined reference value from the logarithm of the power to generate a first error signal; (d) filtering the first error signal; (e) comparing the filtered first error signal to a predetermined first threshold; (f) incrementing or decrementing a first counter value and resetting a filter accumulator as a function of the result of the step of comparing; and (g) converting the first counter value to an analog voltage for controlling the gain of a spread spectrum receiver amplifier. The logarithm is preferably the second logarithm of the power. The method further includes generating a transmitter AGC value.

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: A method for use in a digital data transfer apparatus, such as a radio telephone (10), that includes an adaptive equalizer, such as an adaptive filter (32), for receiving, correcting, and outputting data symbols. The method determines correction coefficients for the adaptive equalizer and includes a first step of, for every data symbol output by the adaptive equalizer, maintaining a first matrix R that is a NxN channel correlation matrix and a second matrix P that is a N.times.1 cross correlation vector between a received signal and a transmitted symbol. The method includes a second step of, for every k.sup.th symbol output by the adaptive equalizer, determining a set of correction coefficients (C) for the adaptive equalizer based upon the matrices R and P. A third step of the method applies the set of determined correction coefficients to the adaptive equalizer so as to optimally correct a subsequently received data symbol.