Abstract: A D.C. offset canceling and gain adjusting techniques permitting completion of correction of D.C. offsets and gain adjustment of amplifiers for amplifying reception signals in a radio communication system are provided. A communication semiconductor integrated circuit has a plurality of low-pass filters and variable gain amplifiers which are alternately connected in multiple stages, and high gain amplifier circuits for amplifying reception signals to a predetermined amplitude level. Offset cancellation values are generated by detecting D.C. offsets of amplifiers for amplifying reception signals according to a set gain, and stored into a memory, and read out of the memory to cancel the D.C. offsets of the amplifiers when starting reception and altering the gain. Gain setting in a high gain amplifying section is accomplished using rough and precise settings.

Abstract: A D.C. offset canceling and gain adjusting techniques permitting completion of correction of D.C. offsets and gain adjustment of amplifiers for amplifying reception signals in a radio communication system are provided. A communication semiconductor integrated circuit has a plurality of low-pass filters and variable gain amplifiers which are alternately connected in multiple stages, and high gain amplifier circuits for amplifying reception signals to a predetermined amplitude level. Offset cancellation values are generated by detecting D.C. offsets of amplifiers for amplifying reception signals according to a set gain, and stored into a memory, and read out of the memory to cancel the D.C. offsets of the amplifiers when starting reception and altering the gain. Gain setting in a high gain amplifying section is accomplished using rough and precise settings.

Abstract: A D.C. offset canceling technique and a gain adjusting technique permitting completion of correction of D.C. offsets and gain adjustment of amplifiers for amplifying reception signals in a relatively short period of time in a radio communication system, such as a wireless LAN, are to be provided. A communication semiconductor integrated circuit (high frequency IC) has a plurality each of low-pass filters and variable gain amplifiers which are alternately connected in multiple stages, and high gain amplifier circuits for amplifying reception signals to a predetermined amplitude level while eliminating unnecessary waves. Offset cancellation values are generated by detecting in advance D.C. offsets of amplifiers for amplifying reception signals according to a set gain, and stored into a memory, and read out of the memory to cancel the D.C. offsets of the amplifiers at the time of starting reception and altering the gain.

Abstract: The invention comprises: processing for receiving an OFDM packet having a preamble and the following data transmission symbol, in which packet the subcarrier interval of the preamble is set wider than that of the data transmission symbol; processing for estimating a DC offset occurring at a receiving side by using the received preamble; processing for correcting the DC offset on the received data transmission symbol, according to the estimation result of the DC offset; and processing for demodulating the DC offset corrected data transmission symbol. Thus, it is possible to estimate a DC offset and then correct the DC offset according to the estimated value, in the OFDM packet with no nul symbol defined there.

Abstract: A wireless LAN system has auto gain control with no work load applied to its baseband processing block. When the wireless LAN system gets ready to receive a signal, the gain control circuit switches between the receiving antennas. The gain control circuit sets gain setting value time divisional data according to the level of a received signal to roughly control the gain to be set in the LAN and the gain to be set in two programmable gain amplifiers.

Abstract: In a radio communication system having a plurality of antennas, a reception-system circuit including variable gain amplification circuits for amplifying a signal received from either of the antennas and a frequency conversion circuit for down-converting the received signal to a signal of a lower frequency, and a signal measuring circuit for detecting intensity of the received signal, whereby a signal received by either of the antennas is selected in accordance with a reception state and amplified and demodulated, change rates with time of a signal which is formed by the signal measuring circuit are determined in respect of either of the signals received by the plurality of antennas and a control signal for selecting a reception antenna is generated in accordance with a differences between the change rates.

Abstract: The invention comprises: processing for receiving an OFDM packet having a preamble and the following data transmission symbol, in which packet the subcarrier interval of the preamble is set wider than that of the data transmission symbol; processing for estimating a DC offset occurring at a receiving side by using the received preamble; processing for correcting the DC offset on the received data transmission symbol, according to the estimation result of the DC offset; and processing for demodulating the DC offset corrected data transmission symbol. Thus, it is possible to estimate a DC offset and then correct the DC offset according to the estimated value, in the OFDM packet with no nul symbol defined there.

Abstract: A D.C. offset canceling technique and a gain adjusting technique permitting completion of correction of D.C. offsets and gain adjustment of amplifiers for amplifying reception signals in a relatively short period of time in a radio communication system, such as a wireless LAN, are to be provided. A communication semiconductor integrated circuit (high frequency IC) has a plurality each of low-pass filters and variable gain amplifiers which are alternately connected in multiple stages, and high gain amplifier circuits for amplifying reception signals to a predetermined amplitude level while eliminating unnecessary waves. Offset cancellation values are generated by detecting in advance D.C. offsets of amplifiers for amplifying reception signals according to a set gain, and stored into a memory, and read out of the memory to cancel the D.C. offsets of the amplifiers at the time of starting reception and altering the gain.

Abstract: Disclosed here is a wireless LAN system employed for quick and accurate auto gain controlling with no work load to be applied to its baseband processing block. When the wireless LAN system gets ready to receive a signal, the gain control circuit switches between the receiving antennas alternately. The gain control circuit, when receiving a signal over a predetermined receiving sensitivity, sets gain setting value time divisional data according to the level of the received signal measured by the first measurement circuit to roughly control the gain to be set in the LNA and the gain to be set in the two programmable gain amplifiers provided in the front steps of the LPF/PGA circuits. The gain control circuit then cancels the DC offset while the second measurement circuit measures the signal level.