Abstract: A Finite Impulse Response (FIR) filter circuit (60) includes delay elements (63, 64, 66), multipliers (71, 72, 73, 74), a summing device (78), and a digital integrator (69) at the output of the FIR filter circuit (60). A method for processing data using the FIR filter circuit (60) includes differentially encoding data prior to storing or processing of the data. The method provides a technique for compressing data since less memory is needed to store derivative data. The method further includes integrating the derivative data using the digital integrator (69) to decompress the derivative data.

Abstract: A transceiver (10) includes a transmitter (16) that receives a digital data stream from a digital signal processor (18) to delay lines (20, 30). The delay lines (20, 30) provide an address to a ROM look-up table (40). Another input of the look-up table (40) receives a signal that selects protocols such as TDMA, CDMA, and GSM. A multi-accumulator fractional-N synthesizer (48) receives phase derivative coefficients and a DAC (46) receives amplitude modulation coefficients from the look-up table (40) based on the selected protocol. The analog output signals from the DAC (46) and the synthesizer (48) are received by a variable gain amplifier (54) that generates an RF amplitude and frequency modulated output signal for transmission from the transmitter (16).

Abstract: A transceiver (10) includes a transmitter (16) that receives a digital data stream from a digital signal processor (18) to delay lines (20, 30). The delay lines (20,30) provide an address to a ROM look-up table (40). Another input of the look-up table (40) receives a signal that selects protocols such as TDMA, CDMA, and GSM. A multi-accumulator fractional-N synthesizer (48) receives phase derivative coefficients and a DAC (46) receives amplitude modulation coefficients from the look-up table (40) based on the selected protocol. The analog output signals from the DAC (46) and the synthesizer (48) are received by a variable gain amplifier (54) that generates an RF amplitude and frequency modulated output signal for transmission from the transmitter (16). The look-up table (40) stores phase derivative coefficients and amplitude modulation coefficients that correct for non-linearity in the variable gain amplifier (54).

Abstract: A wireless communication system (10) uses a phase detector (28) having a first pair of flip-flops (50, 56) for detecting the phase difference between an input frequency and a reference frequency. The first pair of flip-flops control current sources (66, 70) in the charge pump of the phase detector to modulate the error signal. A second pair of flip-flops (52, 58) detect when the input frequency is more than 2.pi. ahead of or behind the reference frequency. The second pair of flip-flops increment and decrement a counter (54) which in turn controls additional current sources (78-88) in the charge pump. The additional current sources extend the linear operating range of the error signal when the phase error exceeds .+-.2.pi..

Abstract: An equalizer (106, 146) for use in systems such as an asymmetric digital subscriber line (ADSL) transceiver (5) reduces the number of calculations required for updating the equalizer coefficients. The equalizer (106, 146) takes advantage of the substantially symmetrical phase and amplitude distortion of the signal constellation, which causes both the amplitude and the phase relationship of the calculated error term for each constellation point to be equal. Instead of performing a full complex multiplication, the equalizer (106, 146) uses some but not all of the product terms between the real and imaginary components of the calculated error term and the conjugate of the received data estimate in the coefficient update calculation. The result is then scaled to account for the missing terms. The resulting equalizer (106, 146) requires fewer calculations for coefficient updating.

Abstract: In a digital demodulator (10) a single sampling moment (28) occurs within each symbol (22). A data estimator (34) identifies a data code and a phase error for each symbol. The data from three symbols (22) are compared to identify whether a phase trajectory is determinate or indeterminate. The phase error from a current symbol is combined with phase trajectory direction data to determine whether a current phase error is in a direction of a next data code or a previous data code. When determinate trajectories are found, phase errors in the direction of a next data code urge the sample moment (28) to occur earlier in the symbols (22) and phase errors in the direction of a previous data code urge the sample moment (28) to occur later in each symbol (22). When indeterminate trajectories are found, substantially no influence is exerted over the timing of the sample moment (28).