Abstract: A wireless communication apparatus for receiving a packet formed of a signal modulated by OFDM includes the following elements. A band-pass filter extracts an OFDM signal of a desired band. A low-noise amplifier having a gain controlled according to a received-signal intensity amplifies the desired OFDM signal. A frequency converter down-converts the amplified OFDM signal into a baseband signal. An analog-digital converter converts the baseband signal into a digital signal. A first high-pass filter removes a DC offset from the baseband signal corresponding to a predetermined preamble portion of the packet. A frequency-offset estimator estimates a frequency offset from the sample signals constituting the baseband signal from which the DC offset has been removed by the first high-pass filter. A frequency-offset corrector removes the estimated frequency offset from the baseband signal.

Abstract: An automatic gain control circuit able to perform high speed and correct level acquisition, able to prevent occurrence of error, and able to prevent a crash of the system. An amplification gain controller outputs a gain control signal to an automatic gain control amplifier to amplify the received signal with maximum value when receiving a burst detection trigger signal. A second gain control signal based on the detected reception signal power is calculated when receiving a first burst synchronization detection signal; and this second gain control signal is output to the automatic gain control amplifier. A received digital signal is amplified with the second gain and integrated to find the reception signal power, from which a third gain control signal is calculated and outputted to the automatic gain control amplifier to amplify the received signal with this third gain.

Abstract: A wireless communication apparatus for receiving a packet formed of a signal modulated by OFDM includes the following elements. A band-pass filter extracts an OFDM signal of a desired band. A low-noise amplifier having a gain controlled according to a received-signal intensity amplifies the desired OFDM signal. A frequency converter down-converts the amplified OFDM signal into a baseband signal. An analog-digital converter converts the baseband signal into a digital signal. A first high-pass filter removes a DC offset from the baseband signal corresponding to a predetermined preamble portion of the packet. A frequency-offset estimator estimates a frequency offset from the sample signals constituting the baseband signal from which the DC offset has been removed by the first high-pass filter. A frequency-offset corrector removes the estimated frequency offset from the baseband signal.

Abstract: In a sampling block 40a-1, an intermediate frequency signal RIFs is sampled at a frequency of the intermediate frequency signal RIFs multiplied by “1/(m+0.25)” or “1/(m+0.75)” (m: 0 or natural number), to generate signals having phase differences “0”, “?/2”, “?”, and “3?/2”. A polarity adjustment block 40a-2 matches a polarity of the signal having phase difference “?” with that of the signal having phase difference “0”. Further, it matches a polarity of the signal having phase difference “3?/2” with that of the signal having phase difference “?/2”. In a signal synthesis block 40a-3, the signal with phase difference “0” and the signal with phase difference “?” having phase difference “?” from each other are synthesized and held to be output as a demodulated signal PI. Further, the signal with phase difference “?/2” and the signal with phase difference “3?/2” having phase difference “?” from each other are synthesized and held to be output as a demodulated signal PQ.

Abstract: In a sampling block 40a-1, an intermediate frequency signal RIFs is sampled at a frequency of the intermediate frequency signal RIFs multiplied by “1/(m+0.25)” or “1/(m+0.75)” (m: 0 or natural number), to generate signals having phase differences “0”, “?/2”, “?”, and “3?/2”. A polarity adjustment block 40a-2 matches a polarity of the signal having phase difference “?” with that of the signal having phase difference “0”. Further, it matches a polarity of the signal having phase difference “3?/2” with that of the signal having phase difference “?/2”. In a signal synthesis block 40a-3, the signal with phase difference “?” and the signal with phase difference “?” having phase difference “?” from each other are synthesized and held to be output as a demodulated signal PI. Further, the signal with phase difference “?/2” and the signal with phase difference “3?/2” having phase difference “?” from each other are synthesized and held to be output as a demodulated signal PQ.

Abstract: An automatic gain control circuit able to perform high speed and correct level acquisition, able to prevent occurrence of error, and able to prevent a crash of the system, a method of same, and a demodulation apparatus, provided with an amplification gain controller 211 for outputting a gain control signal to an automatic gain control amplifier 201 so as to amplify the reception signal with the maximum value when receiving a burst detection starting use trigger signal, calculating a second gain based on a reception signal power value detected at a reception signal power monitor 202 when receiving a first burst synchronization detection signal from the burst detector, outputting the gain control signal to the automatic gain control amplifier 201 so as to amplify the reception signal with the second gain, receiving the digital reception signal amplified with the second gain and integrating the same to find the reception signal power value, calculating a third gain based on the found reception signal power value

Abstract: In a variable gain amplifier apparatus, wide input dynamic range can be secured and low noise characteristic can be obtained by employing first and second variable gain amplifiers have different noise characteristics and different saturation input levels and receive a same input signal. Output signals of the first and second variable gain amplifiers are added to each other to provide an output signal of the variable gain amplifier apparatus. Desired noise characteristic and saturation input level characteristic of the variable gain amplifier apparatus can be obtained by selecting the noise characteristics and the saturation input levels of the first and second variable gain amplifiers appropriately. This allows the variable gain amplifier apparatus to have a wide input dynamic range and low noise characteristic.