1. A method for employing a complex, constant envelope flat spectrum chirp sequence of the length q such that it is mapped by the q-point inverse discrete Fourier transform to another complex, constant envelope sequence comprising:
choosing a number p such that p and q are mutually prime integers having opposite parities;
computing components z(r) of the flat spectrum chirp according to the formula z(r)=exp (j*\u03c0*m*p*r2q) where j2=\u22121, r is an integer r such that 0\u2266r<q; and m equals either 1 or \u22121 for all r; and reducing the peak-to average power ratio of a complex waveform obtained as the q-point inverse discrete Fourier transform of a complex message of the length q, by means of multiplying the r-th component of said message by the r-th component of said flat spectrum chirp, for integer r such that 0<=r<q.
2. The method of claim 1 wherein a plurality of said messages is consecutively retrieved from a data stream; for each message retrieved, parameters of the flat spectrum chirp are determined based on the value of a current element of a pseudorandom sequence; said pseudorandom sequence may be held proprietary by the owner of the data stream for security reasons.
3. The method of claim 1 further comprising restoring said message from said waveform by means of dividing the r-th component of the q-point discrete Fourier transform of the waveform by the r-th component of the flat spectrum chirp, for integer r such that 0\u2266r<q.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An industrial vehicle comprising:
an engine;
a hydraulic pump driven by the engine, wherein the hydraulic pump generates hydraulic pressure;
a cargo handling tool;
a mast to which the cargo handling tool is attached;
a plurality of hydraulic actuators driven by the hydraulic pressure, wherein the hydraulic actuators include a first hydraulic actuator that lifts and lowers the cargo handling tool and a second hydraulic actuator that tilts the mast;
an instruction member that instructs operations of the hydraulic actuators;
a supply oil passage that supplies hydraulic oil discharged from the hydraulic pump to the hydraulic actuators; and
a controller that controls the engine,
wherein when the mast is being tilted forward, the controller performs revving control that raises the engine speed when detecting that an operation of the instruction member instructs a load operation that applies load to the engine.
2. The industrial vehicle according to claim 1, further comprising:
an attachment that moves the cargo handling tool; and
a third hydraulic actuator that moves the attachment,
wherein the load operation is one of lifting of the cargo handling tool, backward tilting of the mast, and movement of the attachment.
3. An industrial vehicle comprising:
an engine;
a hydraulic pump driven by the engine, wherein the hydraulic pump generates hydraulic pressure;
a cargo handling tool;
a mast to which the cargo handling tool is attached;
a plurality of hydraulic actuators driven by the hydraulic pressure, wherein the hydraulic actuators include a first hydraulic actuator that lifts and lowers the cargo handling tool and a second hydraulic actuator that tilts the mast;
an instruction member that instructs operations of the hydraulic actuators;
a supply oil passage that supplies hydraulic oil discharged from the hydraulic pump to the hydraulic actuators; and
a controller that controls the engine,
wherein when the cargo handling tool is being lowered, the controller performs revving control that raises the engine speed when detecting that an operation of the instruction member instructs a load operation that applies load to the engine.
4. The industrial vehicle according to claim 3, further comprising:
an attachment that moves the cargo handling tool; and
a third hydraulic actuator that moves the attachment, wherein
the load operation when the cargo handling tool is being lowered is one of lifting of the cargo handling tool, forward tilting of the mast, backward tilting of the mast, and an movement of the attachment.
5. The industrial vehicle according to claim 3, further comprising:
an oil tank; and
a return oil passage that returns hydraulic oil discharged from the hydraulic pump to the oil tank, wherein
the controller is configured to compare an engine speed with a predetermined threshold and send hydraulic oil to the return oil passage when the engine speed is lower than the threshold,
the threshold is switched between a first threshold and a second threshold, which is set at a lower engine speed than the first threshold, and
the controller is configured to, upon receipt of an instruction to perform the load operation when the cargo handling tool is being lowered, send hydraulic oil to the return oil passage, perform the revving control, and switch the threshold to the second threshold.
6. The industrial vehicle according to claim 5, wherein the controller returns the threshold to the first threshold when the revving control ends.