Abstract: A method for receiving at a receiver having a variable filter a transmitted signal that includes a periodic training signal. The method includes (a) receiving and sampling the transmitted signal at the receiver to produce a digital complex baseband signal; (b) filtering the digital complex baseband signal with the variable filter; (c) detecting the periodic training signal in the filtered digital complex baseband signal; (d) determining a desired channel impulse response based on the detected periodic training signal; (e) calculating filter coefficients required by the variable filter to achieve the desired channel impulse response; and (f) adjusting the variable filter according to the calculated filter coefficients. A receiver for implementing the method is also provided.

Abstract: A transmitter for transmitting an OFDM signal in a communications channel, including: (a) a plurality of base-band OFDM modulators, each for modulating a respective baseband data signal onto a plurality of orthogonal sub-carriers and outputting a respective baseband sub-channel OFDM signal, and (b) a fast convolution filter and up-converter for applying fast convolution filtering and digital up-conversion to the sub-channel OFDM signals to output a combined OFDM signal that includes each of the sub-channel OFDM signals, the fast convolution and up-converter filtering each of the sub-channel OFDM signals and frequency shifting all of the sub-channel signals to respective designated frequencies within the combined OFDM signal.

Abstract: A transmitter and corresponding method for transmitting an OFDM signal in a communications channel, including a plurality of base-band OFDM modulators, each for modulating a respective data signal onto a plurality of orthogonal sub-carriers and outputting a respective sub-channel OFDM signal; and a fast convolution filter and up-converter for applying fast convolution filtering and digital up-conversion to the sub-channel OFDM signals to output a combined OFDM signal that includes each of the sub-channel OFDM signals, the fast convolution and up-converter filtering each of the sub-channel OFDM signals and frequency shifting all of the sub-channel signals to respective designated frequencies within the combined OFDM signal. A corresponding receiver is also provided.

Abstract: A communications system for transferring signals from a wireless transmitter to a hub station, comprising a wireless transmitter configured to transmit a data signal using multiple sub-carriers, a plurality of base stations each configured to receive the multiple sub-carrier data signal and relay the multiple sub-carrier data signal to a hub station; and a hub station configured to receive and combine the multiple sub-carrier data signals from the plurality of base stations. The wireless transmitter may use an orthogonal frequency division modulation (OFDM) scheme to transmit portions of the data signal in parallel on multiple sub-carriers.

Abstract: One aspect of the present invention is a frequency conversion circuit having a pair of local oscillators. The local oscillators are frequency synthesizers based on an external frequency reference. The frequency conversion circuit is configured to perform a frequency conversion to an input signal equal to a frequency difference of signals from the pair of local oscillators; to generate an oscillator frequency difference signal; to generate an error signal using the oscillator frequency difference signal and an internal reference signal derived from the external frequency reference; and to adjust a phase of one of the pair of oscillators using the error signal. The above-described frequency conversion circuit embodiment essentially eliminates divider phase noise such as that generated by traditional prescalers. In addition, the use of two local oscillators provides a frequency conversion circuit capable of wide-range frequency conversion and high resolution.

Abstract: Pseudo random training symbols and/or a constant modulus pilot carrier in OFDM symbols are used to train an adaptive antenna array to cancel unwanted multipath signals and suppress interfering signals. Power variance and power level measurements taken from a plurality of antenna branches during the training symbols and/or the constant modulus pilot carrier are used to determine appropriate weights to be applied to each antenna branch.