Abstract: A receiver for an orthogonal frequency division multiplex radio signal in which a carrier frequency is modulated by sub-carrier signals (S1) coded with data. Analogue signal processing means (3 to 12) produces base-band analogue signals (I-Rx, Q-Rx) in phase quadrature and analogue-to-digital converters (13, 14) convert the analogue signals to phase quadrature digital signals (xI(n), xq(n)). The digital signal processor includes the OFDM demodulator (15) and mismatch compensation (17, 18). The mismatch compensation (17, 18) combines each of the reproduced sub-carrier signals (RI) with a limited number of the reproduced sub-carrier signals (RI-Rk) according to respective frequency offset coefficient (I, k) that is a function of an estimated value of the offset (fc) of the reference frequency relative to the carrier frequency.

Abstract: A time trigger for instruction execution can be contained within the instruction itself. A time stamp value associated with each of a sequence of instructions, which are written into a FIFO memory (9) by an application specific controller (1), is compared with the output value of a counter (11). When the two values are equal, a comparator 10 sends a command to an instruction decoder (8) to execute the current instruction. The invention has the advantage of a reduced interrupt overhead and his particular application to HiperLAN 2 systems in which it can be incorporated without affecting the protocol handling.

Abstract: A receiver for an orthogonal frequency division multiplex radio signal in which a carrier frequency is modulated by sub-carrier signals (S1) coded with data. Analogue signal processing means (3 to 12) produces base-band analogue signals (I-Rx, Q-Rx) in phase quadrature and analogue-to-digital converters (13, 14) convert the analogue signals to phase quadrature digital signals (x1(n), xq(n)). The digital signal processor includes the OFDM demodulator (15) and mismatch compensation (17, 18). The mismatch compensation (17, 18) combines each of the reproduced sub-carrier signals (R1) with a limited number of the reproduced sub-carrier signals (R1-Rk) according to respective frequency offset coefficient (1, k) that is a function of an estimated value of the offset (fc) of the reference frequency relative to the carrier frequency.

Abstract: A signal processor identifies a burst frequency in a communication channel. Buried in a multitude of RF transmitted incoming data is a sinusoidal burst frequency. The incoming data is stored, and the mean and variance of zero crossings of the incoming data is determined and an indicator is calculated. The indicator is compared to a threshold. When the indicator becomes greater than the threshold, then the burst frequency is identified. Next, the start of the burst frequency must be located. The mean and variance of the frequency of the burst signal is determined. The minimum variance is the start of the burst frequency. Other tests are performed to validate the burst frequency and minimize the probability of falsely identifying the burst frequency. The burst frequency is used to calibrate a crystal oscillator that controls the downconversion of the incoming data.

Abstract: A mobile communications device is arranged to receive a modulated signal having a predetermined frequency. A frequency demodulator of the device demodulates the modulated signal, and a frequency correction arrangement calibrates the demodulation frequency of the device to the predetermined frequency by providing a preliminary difference estimation between the predetermined frequency and the demodulation frequency using a broadband portion of the modulated signal, followed by a main difference estimation (between the predetermined frequency and the demodulation frequency) using a dedicated narrowband portion of the modulated signal.