Abstract: An R-C polyphase network that provides bandpass shaping and amplification to maintain the quadrature phase output is provided. In one implementation, a polyphase device comprises two transistors each having a collector, a base and an emitter. Positive and negative components of an input signal are coupled to a respective base of the transistors, the transistors adapted to drive the R-C polyphase network. Inputs of the R-C polyphase network are coupled to the collectors of the transistors. The R-C polyphase network includes an inductor and has first output and a second output offset in phase. The inductor is adapted to provide bandpass filtering of the first output and the second output to reduce harmonics and spurious content in the output, as well as provide amplification of the outputs relative to the input signal.

Abstract: A frequency multiplier circuit is provided that does not rely on filtering to remove unwanted harmonics and spurious content. In one implementation, a frequency doubler comprises a first rectifier doubler stage adapted to receive a first input signal having a first frequency and output a first rectified signal having multiple harmonics; a second rectifier doubler stage adapted to receive a second input signal having the first frequency and offset in phase from the first input signal and to output a second rectified signal, which has the multiple harmonics and is offset in phase from the first rectified signal; and a differential amplifier stage adapted to sum the first and second rectified signals to produce an output signal including a desired output harmonic having a frequency that is double the first frequency. The summing results in the substantial cancellation of unwanted output harmonics in the output signal.

Abstract: A control interface scheme provides for communicating control information between integrated circuits (ICs) in a wireless communication chipset. A serial 3-wire bus is configured to communicate a series of control words assembled on a digital IC to an analog IC prior to a data portion of a frame used by the wireless communication chipset in communicating data. The control words include control settings for use by the analog IC during the data portion of the frame. The control settings, which are stored in registers on the analog IC, include gain settings for two receivers and a transmitter, as well as phase lock loop (PLL) control information and power management information. Several timing signals generated on the digital IC are used by the analog IC during the data portion of the frame to select among the registers to obtain the appropriate control settings at the appropriate times.

Abstract: The present invention advantageously addresses the needs above as well as other needs through a method and apparatus for providing distributed admission control for a communication network. The method and apparatus are configured to receive new flows at a terminal and determine at the terminal the amount of resources available to the terminal. The terminals accept new flows if there are sufficient available resources and deny new flows if there is insufficient available resources. The method and apparatus further manage the bandwidth for flows of the communication network from an access point. The access point includes a bandwidth manager which reserves bandwidth for flows if there is available time within communication frames.

Abstract: The present invention provides a method and apparatus for distributing communication scheduling. The method and apparatus schedule communication across a plurality of links through a link scheduler and schedule flows to be communicated across the plurality of links through a flow scheduler. Typically, the link scheduler is positioned a distance from the flow scheduler. In one embodiment, the method and apparatus utilize a plurality of flow schedulers where each schedules flows across one of the plurality of links.

Abstract: A pilot phase tracking loop for an OFDM receiver including a phase rotator receiving an incoming signal, a fast Fourier transform coupled to a phase rotator output, and a pilot phase error metric including a discrete Fourier transform portion coupled to the phase rotator output. The pilot phase error metric determines a phase error estimate associated with a received OFDM symbol, e.g., a data symbol, from the phase rotator output. A loop filter is coupled to the pilot phase error metric output and an oscillator is coupled to the loop filter output. The oscillator output is coupled to the phase rotator to adjust the phase of subsequent OFDM symbols of the incoming signal. Phase noise introduced by a radio portion of the OFDM receiver and OFDM transmitter is reduced by the baseband portion of the OFDM receiver improving OFDM signal tracking under poor SNR conditions.

Abstract: The present invention provides a method and apparatus for signal processing for signal modulation and demodulation. In signal processing the present invention maintains substantially identical gain and group delays between transmit in-phase (I) and transmit quadrature-phase (Q) paths by receiving a digital transmit I baseband signal and a digital transmit Q baseband signal of a first multicarrier communication signal. A digital transmit IF signal is digitally constructed from the transmit I and Q digital baseband signals including bandpass sampling and the digital transmit IF signal is converted to an analog transmit IF signal. The present invention additionally maintains substantially identical gain and group delays between receive I and Q paths.

Abstract: A method of transmission level security, and a corresponding transmission security system, the method consists of the steps of: forming a plurality of digital signals representing a symbol to be transmitted over a communication medium, wherein respective ones of the plurality of digital signals are modulated onto respective ones of a plurality of subcarriers according to a multiple carrier modulation scheme; and introducing a predetermined group delay distortion in one or more of the plurality of subcarriers, such that portions of the one or more of the plurality of subcarriers will be received outside of a time window corresponding to the symbol at a receiver. In one implementation, an equipped receiver substantially removes the predetermined group delay distortion such that the portions of the one or more of the plurality of subcarrier fit within the time window.

Abstract: A pilot phase tracking loop for an OFDM receiver including a phase rotator receiving an incoming signal, a fast Fourier transform coupled to a phase rotator output, and a pilot phase error metric including a discrete Fourier transform portion coupled to the phase rotator output. The pilot phase error metric determines a phase error estimate associated with a received OFDM symbol, e.g., a data symbol, from the phase rotator output. A loop filter is coupled to the pilot phase error metric output and an oscillator is coupled to the loop filter output. The oscillator output is coupled to the phase rotator to adjust the phase of subsequent OFDM symbols of the incoming signal. Phase noise introduced by a radio portion of the OFDM receiver and OFDM transmitter is reduced by the baseband portion of the OFDM receiver improving OFDM signal tracking under poor SNR conditions.

Abstract: A method and apparatus of pilot phase error estimation in an orthogonal frequency division multiplexed (OFDM) receiver including the steps of: determining pilot reference points corresponding to a plurality of pilots of an OFDM preamble waveform; and estimating an aggregate phase error of a subsequent OFDM data symbol relative to the pilot reference points using complex signal measurements corresponding to each of the plurality of pilots of the subsequent OFOM data symbol and the pilot reference points. For example, a maximum likelihood based estimation is performed using the complex signal measurements and the pilot reference points. Thus, the poor phase performance in a radio portion of the OFDM receiver is compensated for by the pilot phase error estimation in the baseband portion of the OFDM receiver and improved OFDM signal tracking accomplished under poor SNR conditions.

Abstract: A pilot phase tracking loop for an OFDM receiver including a phase rotator for receiving an incoming signal, which is coupled to a Fourier transform, which is coupled to a pilot phase error metric for determining a phase error estimate associated with a received OFDM symbol, e.g., a data symbol. The pilot phase error metric is coupled to a loop filter, which is coupled to an oscillator, which is coupled back to the phase rotator. The phase rotator rotates the incoming signal by the filtered phase error estimate for subsequent OFDM symbols to reduce the phase noise of the signaling output from the phase rotator. Thus, the phase noise introduced by a radio portion of the OFDM receiver and an OFDM transmitter is compensated for by the pilot phase error estimation in the baseband portion of the OFDM receiver and improved OFDM signal tracking is accomplished under poor SNR conditions.

Abstract: A method of transmission level security, and a corresponding transmission security system, the method consists of the steps of: forming a plurality of digital signals representing a symbol to be transmitted over a communication medium, wherein respective ones of the plurality of digital signals are modulated onto respective ones of a plurality of subcarriers according to a multiple carrier modulation scheme; and introducing a predetermined group delay distortion in one or more of the plurality of subcarriers, such that portions of the one or more of the plurality of subcarriers will be received outside of a time window corresponding to the symbol at a receiver. In one implementation, an equipped receiver substantially removes the predetermined group delay distortion such that the portions of the one or more of the plurality of subcarrier fit within the time window.

Abstract: A probing scheme for diversity antenna branch selection makes use of a physical waveform frame structure that includes a diversity selection portion. The diversity selection portion may be located anywhere in the physical waveform frame structure and includes one or more antenna branch probing portions. Several antenna branch switching time intervals are interleaved with the antenna branch probing portions. Several repeated Orthogonal Frequency-Division Multiplexing (OFDM) symbols are used to form the antenna branch probing portions and the switching time intervals. Diversity reception in radio frequency (RF) communications is performed by receiving a frame having the diversity selection portion with a system having L antenna branches and n RF receivers, and then taking measurements from n of the L antenna branches during one of the antenna branch probing portions.

Abstract: A diversity antenna branch selection module includes first and second computation stages. The first computation stage computes an approximate bit error probability for each of K sub-carriers in an Orthogonal Frequency-Division Multiplexing (OFDM) signal for each of L different antenna branches n antenna branches at a time. The second computation stage processes the approximate bit error probabilities to identify a group of n of the L different antenna branches that minimizes an approximate bit error probability of a signal that will eventually be constructed from sub-carriers that are each received by any one of the n antenna branches in the identified group. The module is ideal for use in a system having n radio frequency receivers and for wireless local area network (WLAN) applications operating at high frequencies, such as 5 to 6 GHz, in multipath environments.

Abstract: A method, and means for accomplishing the method, of pilot phase error estimation in an orthogonal frequency division multiplexed (OFDM) receiver consists of the steps of: determining pilot reference points corresponding to a plurality of pilots of an OFDM preamble waveform; and estimating an aggregate phase error of a subsequent OFDM data symbol relative to the pilot reference points using complex signal measurements corresponding to each of the plurality of pilots of the subsequent OFDM data symbol and the pilot reference points. For example, a maximum likelihood based estimation is performed using the complex signal measurements and the pilot reference points. Thus, the poor phase performance in a radio portion of the OFDM receiver is compensated for by the pilot phase error estimation in the baseband portion of the OFDM receiver and improved OFDM signal tracking accomplished under poor SNR conditions.

Abstract: A card-based diversity antenna structure includes a card and at least two antenna elements. The card has active circuitry attached thereto and connectors located at a first end thereof configured for engagement with an interface slot. The at least two antenna elements are attached to the card at a second end thereof and are coupled to the active circuitry. At least two antenna elements are sufficiently spaced apart so as to achieve spatial diversity. The polarizations of two of the at least two antenna elements may be orthogonal to each other so as to achieve polarization diversity. The antenna structure delivers good receive and transmit diversity performance and is well suited to the form factor limits imposed by the dimensions of small cards, such as PCMCIA cards. The configuration is very convenient for application in the 5 to 6 GHz frequency band.

Abstract: An antenna assembly that can conform to two or more noncoplanar walls of a housing associated with numerous different devices that communicate in a WLAN. At least two antenna elements are included with a first antenna element attached to a portion of a first wall and a second antenna element attached to a portion of a second wall. Active circuitry is attached to the backside of the antenna assembly and coupled to the antenna elements. The antenna assembly can be included on a base that can be easily added-on to a product. Spatial and/or polarization diversity can be achieved in a small form-factor at high frequencies, including the 5 to 6 GHz frequency band.

Abstract: An antenna assembly that can conform to two or more noncoplanar walls of a housing associated with numerous different devices that communicate in a WLAN. At least two antenna elements are included with a first antenna element attached to a portion of a first wall and a second antenna element attached to a portion of a second wall. Active circuitry is attached to the backside of the antenna assembly and coupled to the antenna elements. The antenna assembly can be included on a base that can be easily added-on to a product. Spatial and/or polarization diversity can be achieved in a small form-factor at high frequencies, including the 5 to 6 GHz frequency band.

Abstract: A method of transmission level security, and a corresponding transmission security system, the method consists of the steps of: forming a plurality of digital signals representing a symbol to be transmitted over a communication medium, wherein respective ones of the plurality of digital signals are modulated onto respective ones of a plurality of subcarriers according to a multiple carrier modulation scheme; and introducing a group delay distortion in one or more of the plurality of subcarriers, wherein a peak-to-peak variation of the group delay distortion is greater than a guard time interval corresponding to the symbol, such that portions of the one or more of the plurality of subcarriers will be received outside of a time window corresponding to the symbol at a receiver.

Abstract: An antenna structure for small wireless communication devices includes multiple antenna elements to achieve diversity and uniform hemispherical coverage gain. Individual patch antennas are located on separate surfaces of a polyhedron or hemispherical dome structure. The antenna structure is well-suited for operation at high frequencies, including the 5 to 6 GHz band. The antenna elements and RF circuitry can be combined in a small integrated enclosure, and the structure is suited for use in a base station of a WLAN.