Abstract: The present invention relates to a circuit structure for realizing real-time pre-distortion calibration of broadband IQ modulation, comprises a baseband generation module, for the calibration signal generator to generate two orthogonal sine cosine calibration signals respectively according to the calibration bandwidth and the order of the pre-distortion filter, and the data switch is switched to the relevant data channel; a digital-to-analog conversion module, for converting the signals into analog I and Q baseband signals; a frequency synthesis module, for generating signals in a certain frequency range; a IQ modulation module, for mixing the analog baseband signal with the local oscillator signal; an amplitude control module, for continuous adjustment of the RF signal power. The present invention also relates to a method for realizing real-time pre-distortion calibration processing of broadband IQ modulation.

Abstract: A frequency delta-sigma modulation signal output circuit includes: a phase modulation circuit configured to generate n delay signals obtained by delaying a measurement target signal, n being an integer of 2 or more, and generate a phase modulation signal by randomly selecting one of the n delay signals in synchronization with the measurement target signal; and a frequency ratio digital conversion circuit configured to generate a frequency delta-sigma modulation signal using a reference signal and the phase modulation signal.

Abstract: Systems, methods and devices for transmitting and receiving and demodulating transpositional modulated signals, for increasing information bandwidth of defined communication channels, and for time-delay shifting an input signal in accordance to an input control signal are provided. One such method of increasing the information bandwidth of a defined communication channel includes receiving a first modulated signal having a first carrier signal frequency; receiving a second modulated signal having a second carrier signal frequency, the second modulated signal being modulated with information independent of information modulating the first carrier signal, the second carrier signal frequency being harmonically or sub-harmonically related to the first carrier signal frequency; and combining the first and second signals.

Abstract: A method for transporting communications signals includes receiving an analog IF signal at a first unit. The analog IF signal includes a first carrier having a first frequency and a first bandwidth and a second carrier having a second frequency different from the first frequency and a second bandwidth. The analog IF signal is converted to a digitally sampled IF signal having the first carrier located in a first Nyquist zone, the second carrier located in a second Nyquist zone, an image of the first carrier located in a third Nyquist zone, and an image of the second carrier located in the third Nyquist zone. The image of the first carrier and the image of the second carrier is transmitted from the first unit to a second unit, where the image of the first carrier and the image of the second carrier is then converted to the analog IF signal.

Abstract: A four-element wideband photonic DF system with robust symmetrical number system preprocessing utilizes dual electrode Mach-Zehnder modulators (DE-MZMs) to conduct phase detection for direct wideband direction finding (DF) of RF signals, such as microwave signals, in which the normalized magnitude of the output signal phase detector circuit is equal to |sin(?/2)| where ? is the phase difference between the plane waves arriving at the reference and measurement antennas of a linear DF array. The method and system allow fine angular resolution using a much smaller array size than is typically required for linear arrays employing super-resolution signal processing techniques.

Abstract: A phase shifter component is described. Inputs are arranged to selectively receive an inphase component of an in-phase (I) signal or an outphase I signal 180° out of phase with the inphase I signal, and to selectively receive an inphase component of a quadrature-phase (Q) signal or an outphase Q signal 180° out of phase with the inphase Q signal. A first gain portion includes only two transistor elements arranged to amplify the received outphase or inphase I signal. A second gain portion includes only two transistor elements arranged to amplify the received outphase or inphase Q signal. The first and second gain portions are configured to control the gain of the received outphase or inphase I signal and the received outphase or inphase Q signal, respectively, to provide a composite output signal with a desired phase shift between 0° and 360°.

Abstract: Methods, apparatuses, computer program products, and computer readable media are disclosed herein. In one aspect, an apparatus can include a transmission line configured to accept a radio frequency signal from an antenna, wherein the antenna is configured to receive the radio frequency signal from a satellite. The apparatus can further include a system on a chip comprising a direct conversion receiver, a digital signal processor configured to process a digital representation of a baseband receive waveform to determine received information, and a wireless networking interface configured to send the received information to a satellite communications indoor unit.

Abstract: Provided is a system and method for synchronization between digital-to-analog converters (DAC) for high speed signal processing. A synchronization method of a multi-DAC apparatus may include: inputting a clock to a multiplexer (MUX) DAC; dividing the clock into a first clock and a second clock; transferring a phase difference between the first clock and the second clock to a D flip-flop; and synchronizing the first clock and the second clock by processing the phase difference.

Abstract: A circuit includes a switched modulator stage combining an information signal with a square wave carrier to produce a first modulated signal; and a second modulation stage forming additional steps in the first modulated signal to produce a second modulated signal.

Abstract: A parametric audio system that permits greater control over the bandwidth of a modulated signal. The system includes a carrier signal generator for generating a carrier signal, at least one audio signal source for generating at least one audio signal, and a modulation component for generating an envelope signal based on the at least one audio signal, modulating the phase of the carrier signal based on a predetermined function to generate a first modulated signal, and multiplying the envelope signal and the first modulated signal to generate a second modulated signal. By selection of the predetermined function, the modulation component can alter the spectrum of the second modulated signal, thereby permitting greater control over the bandwidth of the second modulated signal.

Abstract: A polar modulator of the present invention includes: a first function block which generates an amplitude signal and a phase signal; a second function block which adjusts the signal delay between the amplitude signal and the phase signal; a third function block which allows the low frequency component of the amplitude signal to pass therethrough; a fourth function block which modulates the phase of the phase signal; a fifth function block which outputs a modulation voltage, based on the amplitude signal; a sixth function block which modulates the amplitude of the phase signal, based on the modulation voltage; a seventh function block which measures the temperature of at least one function block; and an eighth function block which calculates a compensation amount for the signal delay, based on the measured temperature. The second function block adjusts the signal delay, based on the compensation amount.

Abstract: A power amplifier comprises: polar modulator that receives modulated signal including amplitude-modulated component and phase-modulated component, outputs the amplitude-modulated component, superimposes the modulated signal on carrier wave to generate signal output as RF-modulated signal, and delays at least one of the amplitude-modulated component and the RF-modulated signal; first amplitude modulator that receives the amplitude-modulated component, pulse-modulates the amplitude-modulated component to generate signal output as pulse-modulated signal, and amplifies the amplitude-modulated component with the amplitude-modulated component and the pulse-modulated signal as control signals; second amplitude modulator that receives the amplitude-modulated component and the pulse-modulated signal, and amplifies the amplitude-modulated component with the amplitude-modulated component and the pulse-modulated signal as control signals; and first RF amplifier that receives the RF-modulated signal, amplifies the RF-modu

Abstract: Disclosed is a polar modulation transmission circuit wherein distortion components resulting from variations between individual amplifiers are compensated for with few man-hours, and deterioration in signal quality is effectively suppressed. A frequency converter (180) converts the frequency of an output signal of a high frequency power amplifier (170) and outputs a frequency domain signal, and a phase compensation unit (150) measures the power level, for each delay amount, at a low frequency band and high frequency band wherein the detuning frequency from the frequency domain signal is the same, calculates the “unlevel amount” (relative level difference) between the power level of the low frequency band and power level of the high frequency band for each delay amount, and determines the compensation characteristics on the basis of the relationship of the unlevel amount (relative level difference) to the delay amount.

Abstract: The present invention relates to a polar modulation apparatus and method, in which a polar-modulated signal is generated based on separately processed phase modulation (PM) and amplitude modulation (AM) components of an input signal. An amplified polar modulated output signal is generated in accordance with the phase modulation and amplitude modulation components by using a differential power amplifier circuitry(30) and supplying an amplified phase modulation component to a differential input of the differential power amplifier circuitry(30). A bias input of the differential power amplifier circuitry(30) is controlled based on the amplitude modulation component, so as to modulate a common-mode current of the differential power amplifier circuitry(30). Thereby, a new concept of a polar modulator with static DC-DC converter and power and/or efficiency and/or linearity controlled output power amplifier can be achieved.

Abstract: The pulse modulated RF power control method includes an output amplitude control step for controlling amplitude of a pulse output, and a duty control step for controlling a duty ratio of the pulse output. The output amplitude control step performs a constant amplitude control to control an amplitude value of the pulse output so that the amplitude value becomes equal to a set amplitude value. The constant amplitude control according to the output amplitude control, for instance, gives a feedback of the amplitude value of the pulse output outputted by the power control, obtains a difference value between the feedback value and the set amplitude value, and controls the amplitude value of the pulse output so that the difference value becomes zero.

Abstract: A device is provided for use with an input signal including a first packet of a first modulation type in series with a second packet of a second modulation type. The device includes a gain adjustment portion and a gain portion. The gain adjustment portion can output a first gain adjustment signal based on the first packet or can output a second gain adjustment signal based on the second packet. The gain portion can output a first signal corresponding to the first packet and can output a second signal corresponding to the second packet. The first signal is based on the input signal and a first gain factor. The second signal is based on the input signal and a second gain factor. The first gain factor is based on the first gain adjustment signal. The second gain factor is based on the second gain adjustment signal.

Abstract: Disclosed are a data receiving apparatus that may discriminate a type of a received data frame, and a data transmission apparatus that may apply a constellation mapping scheme to a data frame so that a data receiving apparatus may discriminate the data frame in accordance with the constellation mapping scheme applied to the data frame.

Abstract: A device may be capable of communicating using at least two type types of modulation methods. Methods and systems are provided for communication of data according to a communications method in which a master transceiver communicates with one or more slave transceivers according to a master/slave relationship. A first data message may include first information and second information that are modulated according to a first modulation method. The second information may include lower data rate data. A second data message may include third information that may be modulated according to the first modulation method and that may indicate an impending change to a second modulation method. The second modulation method may be used for transmitting fourth information, and the fourth information may be included in the second message. The fourth information may include higher data rate data, for example Internet access data.

Abstract: Apparatus for generating a modulation signal for use in modulating the power supply of a power amplifier uses coarse and fine control for controlling the amplitude of the modulation signal, and thereby controlling the output power of the power amplifier. The modulation signal may be generated in the digital domain and converted to the analog domain by a digital-to-analog converter, with the digital-to-analog converter providing the fine control and a variable gain amplifier providing the coarse control of the analog signal.

Abstract: Apparatus and methods for improving the spectral performance of a polar modulator are described. A composite FM signal component of a composite polar transmit signal may be processed by monitoring the FM signal to detect a transient burst component, and, responsive to detection of a transient burst, generating a spectrally friendly replacement signal component that may be combined with the FM signal to improve spectral performance of the composite signal. In addition, an associated AM component of the composite transmit signal may be filtered to further improve spectral performance.

Abstract: A transmission circuit according to the present invention includes: an amplitude signal driving section (220) that generates a control voltage based on an amplitude signal in a high-output mode, and generates a control voltage at a predetermined level and a bias current based on the amplitude signal in a low-output mode; a variable gain adjustment section (114) that adjusts a power level of the phase signal; and a power amplifier (130) which amplitude-modulates the phase signal having the adjusted power level on the basis of the control voltage, in the high-output mode, and to a power supply terminal of which the control voltage is supplied and which amplitude-modulates the phase signal having the adjusted power level on the basis of the bias current, in the low-output mode.

Abstract: The present disclosure relates to using windowing to reduce the bandwidth of an amplitude modulation (AM) power supply input signal (PSIS), which is fed to an AM power supply to provide envelope power to an RF power amplifier stage via an AM power supply output signal. By reducing the bandwidth, noise levels from the AM power supply may be reduced. However, although the bandwidth of the AM PSIS is reduced, the AM power supply output signal may track the AM of the RF power amplifier stage closely enough to meet linearity requirements and to provide high efficiency. The windowing may be based on dividing a stream of AM input samples into a stream of input windows, from which a stream of output windows is created to provide a stream of windowed AM input samples that are used to provide a windowed AM PSIS to the AM power supply.

Abstract: A method for modulating a signal transmitted by a first device to a second device which is energised by the signal, wherein the first device is further arranged to amplitude modulate the signal so as to transmit data thereon, the method further comprising phase modulating the signal.

Abstract: The present invention relates to a polar modulation apparatus and method, in which a polar-modulated signal is generated based on separately processed phase modulation (PM) and amplitude modulation (AM) components of an input signal. An amplified polar modulated output signal is generated in accordance with the phase modulation and amplitude modulation components by using a differential power amplifier circuitry and supplying an amplified phase modulation component to a differential input of the differential power amplifier circuitry. A bias input of the differential power amplifier circuitry is controlled based on the amplitude modulation component, so as to modulate a common-mode current of the differential power amplifier circuitry. Thereby, a new concept of a polar modulator with static DC-DC converter and power and/or efficiency and/or linearity controlled output power amplifier can be achieved.

Abstract: A modulation system can switch between two modulation modes. In order to comply with limits on peak power in spectral bands outside the RF operating one the transmitter is required to ramp down to a condition of minimal power. To avoid fixed ramping and trailing bits, the transmitting signal is subjected to FIR filtering. The two FIR filters are primed with a sequence using a parallel input mode before serially entering the information data.

Abstract: A circuit for providing AM/PM modulation is described. The circuit provides two drive signals which are later combined in a constructive/destructive fashion. The circuit provides AM modulation with a drive signal having a consistent power level modulated to have varying pulse widths in order to provide variable power within each cycle.

Abstract: A device may be capable of communicating using at least two type types of modulation methods. The device may include a transceiver capable of acting as a master according to a master/slave relationship in which communication from a slave to a master occurs in response to communication from the master to the slave. The master transceiver may send transmissions discrete transmissions structured with a first portion and a payload portion. Information in the first portion may be modulated according to a first modulation method and indicate an impending change to a second modulation method, which is used for transmitting the payload portion. The discrete transmissions may be addressed for an intended destination of the payload portion.

Abstract: A digital amplitude modulator. The digital amplitude modulator is configured to modulate the amplitude of an input carrier signal based on input digital data and generate a corresponding output signal. The digital amplitude modulator includes a first variable gain amplifier for receiving the input carrier signal and generating a corresponding first amplified carrier signal, a second variable gain amplifier for receiving the input digital data and generating corresponding digital amplitude control data and a plurality of selectively activatable amplifier stages. Each amplifier stage receives a replica of the first amplified carrier signal and generates a corresponding second amplified carrier signal when activated. The output signal corresponds to a combination of the second amplified carrier signals generated by the activated amplifier stages.

Abstract: A modulating means for modulating and/or demodulating data for transmission from a first device to a second device, wherein the modulating means is capable of modulating and/or demodulating data according to at least a first and a second modulation technique.

Abstract: Provided is a PLL oscillation circuit that can reduce the variability of modulation sensitivity of a VCO 101 and obtain a desired output amplitude quickly with high precision. An amplitude detector 103 detects an output amplitude of the VCO 101. An amplitude controller 105 controls a current value of a variable current source 109 so as to have an output amplitude of the VCO 101 detected by the amplitude detector 103 to be a desired amplitude. A LPF 108 is connected between the amplitude controller 105 and the variable current source 109. A switch 107 connects or disconnects the LPF 108 between the amplitude controller 105 and the variable current source 109. The amplitude controller 105 is connected to the variable current source 109 through either the LPF 108 or the switching switch 107.

Abstract: A modulator arrangement includes a power amplifier which receives a carrier signal and has a current control input and a voltage supply input. The modulator arrangement further includes a supply voltage modulator having an output coupled to the voltage supply input and an input coupled to the data input and a bias current modulator with an output coupled to the current control input and an input coupled to the data input. A control unit is provided which has a power control output coupled to the supply voltage modulator and to the bias current modulator to control the supply voltage modulator and the bias current modulator depending on a power control signal.

Abstract: A method for amplitude modulating a carrier signal according to one embodiment includes splitting the carrier signal into first and second paths; phase modulating the carrier signal on the first path; phase modulating the carrier signal on the second path; combining the phase modulated carrier signal on the first path with the phase modulated carrier signal on the second path for generating an amplitude modulated output signal; and wherein a first feedback loop couples the amplitude modulated output signal to circuitry for phase modulating the carrier signal on the second path but not to circuitry for phase modulating the carrier signal on the first path, the first feedback loop being for reducing a residual phase variation of the amplitude modulated output signal. Additional systems and methods are also presented.

Abstract: The present invention relates to a polar modulation apparatus and method, in which an in-phase and a quadrature-phase signal are processed in the analog domain to generate an analog signal corresponding to a derivative of a phase component of said polar-modulated signal. The analog signal is then input to a control input of a controlled oscillator (40). As an example, the processing may be based on a differentiate-and-multiply algorithm in the analog domain. Thereby, phase and envelope signals are generated in the analog domain and bandwidth enlargement due to the processing of the polar signals and corresponding aliasing can be prevented to obtain a highly accurate polar-modulated output signal.

Abstract: A modulation system includes an amplitude modulation path and a phase modulation path coupled to the amplitude modulation path. One of the amplitude modulation path and the phase modulation path receive a reduced current such that the reduced current reduces power consumption by the system. Preferably, the amplitude modulation path receives the reduced current. The amplitude modulation path has a first set of components and a second set of components. The first set of components consumes less power by using slower operation. The second set of components consumes less power by effectively not operating, or being turned off.

Abstract: A transmission circuit for outputting transmission signals with a low distortion and a high efficiency over a wide range of output power is provided. A signal generation section (11) generates an amplitude signal and a phase signal. An angle modulation section (12) performs angle modulation on the phase signal and outputs an angle-modulated signal. A regulator (14) receives the amplitude signal via a variable gain amplification section (18) and supplies a voltage controlled based on the magnitude of the amplitude signal to the amplitude modulation section (15). The amplitude modulation section (15) performs amplitude modulation on the angle-modulated signal and outputs a modulated signal to the variable attenuation section (16). When the value of power information is smaller than a predetermined threshold value, the control section (19) increases the gain of the variable gain amplification section (18) and the attenuation of the variable attenuation section (16).

Abstract: A single subscriber line multi-point communication system is disclosed. In general, the multi-point communication system can include a first transceiver coupled to a subscriber line capable of transmitting and receiving at least two modulation methods, either of said modulation methods being operable to transmit a test signal, and a second transceiver coupled to said subscriber line capable of transmitting and receiving said at least two modulation methods, the second transceiver being operable to receive the test signal and determine at least one channel parameter from the test signal. A master transceiver that can be used in various embodiments of a single subscriber line multi-point communication system, and a tributary transceiver are further disclosed.

Abstract: A modulated optical system with anti-clipping reduces or corrects clipping that might occur in the laser as a result of negative spikes or peaks in a multichannel RF signal. The system generally detects an envelope of the RF signal to generate an anti-clipping signal that follows at least a portion of the envelope and prevents one or more negative peaks from causing clipping by adjusting a bias current in response to the anti-clipping signal. The system may also reduce cross modulation by clamping the anti-clipping signal at an anti-clipping limit during lower power periods of the RF signal.

Abstract: In an adaptive modulation and coding method one or more adjustable values are created (S1), each corresponding to at least one of a plurality of available modulation and coding levels applicable to a signal transmitted from a transmitter to a receiver, and each representing a change to the level(s) to which it corresponds. One or more of said adjustable values is/are adjusted in dependence upon whether or not the signal is received successfully by the receiver (S2-S5). One of said available modulation and coding levels is selected (S6-S8) to apply to the signal based on such an adjustable value. Such a method can enable the appropriate modulation and coding level to be selected even when the path and channel conditions vary. The method is applicable to selecting modulation and coding levels in a high-speed downlink packet access system of a wireless communication network.

Abstract: A distortion compensating circuit is provided in which, in the polar modulation system, while suppressing increase of compensation data and increase of the circuit scale, a modulated signal can be correctly expressed, or low-distortion characteristics of a power amplifier can be realized. Based on a steady characteristic compensating circuit 11 which stores an output signal amplitude and output phase characteristics with respect to a control voltage in a steady state, amplitude adjustment is executed on amplitude information r11(t) on which amplitude correction is performed, by a first amplitude information adjusting portion 13, whereby the output-response characteristics of an output signal amplitude of an amplifier with respect to a change of the control voltage can be improved.

Abstract: Direct digital QAM modulation at an RF frequency is obtained from digitally synthesized RF signals which are generated for use as the two vectors. The two vectors are individually controlled in phase and summed to provide a combined phase and amplitude modulation that forms the modulated signal. The synthesized RF signal is generated from a higher reference frequency using a variable pulse stretching technique implemented with programmable delay lines. The amount of the pulse stretch in each cycle is controlled by a phase increment value. Pulse stretching can be extended beyond one cycle by pulse swallowing, allowing the generation of an RF signal from DC up to and including the input reference frequency. Phase modulation is added by digital control of the pulse stretching according to the phase modulation data bits.

Abstract: The invention is directed at a hybrid modulation apparatus which combines a polar modulation circuit and a linear modulation circuit. The hybrid apparatus allows a communications device to function as a polar or a linear modulation circuit with less components as the output of the linear modulation circuit is an input of the polar modulation circuit.

Abstract: A low noise RF driver circuit including at least two series-coupled driver stages which receive a frequency modulated signal and an amplitude modulated signal that is applied to the supply voltage input of the driver stages, and provide a combined output signal. The RF driver circuit can be implemented in CMOS technology and integrated with other components of an RF communication subsystem, such as an RF transceiver circuit and power amplifier. Each driver stage includes a complementary pair of transistors with source degeneration resistors for linearity and gain control.

Abstract: Transmission apparatus capable of reducing distortion of the vector modulation wave that is the transmission output to a sufficiently small level is provided. An amplifying section (105) generates a vector modulation wave based on an amplitude component modulation signal and a phase modulation wave. A synchronous demodulating section (107) detects the vector modulation wave, generates a synchronous demodulation signal, and sends this to a band filtering section (108). The band filtering section (108) extracts a signal of the frequency component of the distortion from a synchronous demodulation signal outputted by the synchronous demodulating section (107).

Abstract: An IQ modulator's performance is optimized through determination of suitable control parameters by the application of known DC biases as the I and Q inputs. Also known are the relative amplitude and actual phase of the sine and cosine carriers to be modulated before they are summed. It is shown that by measuring an RMS voltage Atotal an appropriate number of times for a related combination of the applied DC biases in conjunction with the other known input parameters, a number of behavior parameters that are indicative of mixer performance can be discovered through analysis, such as the solution of a system of linear equations. The combination of behavior parameters may be assigned a Figure Of Merit (FOM) that can be taken as an indication of the degree to which mixer operation approaches ideal behavior. The control parameters may be perturbed over a selected range, and the extraction of the behavior parameters repeated.

Abstract: Provided is a transmission modulation apparatus, using polar modulation of two-point modulation scheme, capable of completing a timing adjustment of a BB phase modulation signal and BB amplitude modulation signal in a short time. A phase modulation section (10) that performs two-point modulation with a PLL circuit is provided with a switch (17) to make the PLL circuit open loop, and when a first delay section (5) corrects the deviation in synchronization between the BB phase modulation signal and BB amplitude modulation signal, the switch (17) is turned off to make the PLL circuit open loop.

Abstract: A single subscriber line multi-point communication system is disclosed. In general, the multi-point communication system can include a first transceiver coupled to a subscriber line capable of transmitting and receiving at least two modulation methods, either of said modulation methods being operable to transmit a test signal, and a second transceiver coupled to said subscriber line capable of transmitting and receiving said at least two modulation methods, the second transceiver being operable to receive the test signal and determine at least one channel parameter from the test signal. A master transceiver that can be used in various embodiments of a single subscriber line multi-point communication system, and a tributary transceiver are further disclosed.

Abstract: Polar modulators include a phase splitter, a controller, variable current sources, transistor circuits, and a combiner. The phase splitter splits a RF carrier signal into quadrature component signals that are 90 degrees out of phase with each other. The controller generates modulation control signals based on information that is to be transmitted. The variable current sources each generate a variable amplitude current signal based on a different one of the modulation control signals. Each of the transistor circuits amplify a different one of the quadrature component signals with a variable amplification based on the variable amplitude current signal from a different one of the variable current sources to generate an amplitude adjusted quadrature component signal. The combiner combines the amplitude adjusted quadrature component signals from each of the transistor circuits to generate a phase-modulated RF carrier output signal.

Abstract: A transmitter system is provided. In one embodiment, the transmitter system includes a data modulation unit, which generates a stream of data that is synchronized with a master clock. The transmitter system additionally includes a transmitter that transmits the stream of synchronized data by way of an attached antenna. In another embodiment the transmitter system includes a Medium Access Control (MAC) layer that includes a clock synchronization device, a frequency divider, a slot allocation unit, and a multiplexer/demultiplexer. This Abstract is provided for the sole purpose of complying with the Abstract requirement rules that allow a reader to quickly ascertain the subject matter of the disclosure contained herein. This Abstract is submitted with the explicit understanding that it will not be used to interpret or to limit the scope or the meaning of the claims.

Abstract: A method and apparatus for producing a modulation scheme usable in conjunction with information transmission and reception via waveforms, such as electromagnetic waves. The modulation scheme is usable for such purposes as resolving range ambiguities and overcoming fading and interference problems via use of offset signals that vary in frequency over time (e.g., chirp signals), which spread the signal over a larger bandwidth. The method includes coding a symbol signal onto a split data stream containing a reference signal (e.g., a chirp), to which a time delay has been applied, then recombining the split streams to produce a composite waveform. The method can also include demodulating a composite received waveform by applying a reference signal to the waveform and then band pass filtering the waveform into discrete symbol data. Apparatus and systems are also provided for performing the method.

Abstract: A system and method for training a radio receiver to mitigate the effects of ISI caused by multi-path includes receiving a header of a transmitted packet at the receiver, the header containing at least one flag to identify a corresponding reference training sequence to be selected by the receiver and to indicate whether a training sequence is inserted in a packet. The receiver decodes the header to determine whether a training sequence is indicated by the flag and to select the corresponding reference training sequence. The training sequence is transmitted positioned within a data packet at a midamble between the header and a first segment of the data packet. The received training sequence is compared with the selected reference training sequence and the equalization parameters of the receiver are adjusted based on the results of the comparison. The selected reference training sequence corresponds to the modulation scheme applied to the payload.