Sideband suppression in angle modulated signals
AssigneeZbw LLC
InventorSam Cowan
Life of this patent
Estimating the term…
Abstract
In an angle modulated radio transmitter, the total power is the same when modulated or unmodulated. Angle modulation produces multiple sideband pairs. The power in the sidebands is derived from the carrier. When a complex modulating waveform is used, the power (and therefore the amplitude) of the carrier varies. A system and method is provided for dramatically minimizing, to nearly zero, the bandwidth needed to transmit digital information using sideband suppression of angle modulated signals. The systems described use various techniques to suppress sideband pairs, leaving the carrier signal. The amplitude variations of the carrier are used to convey information. In some examples, techniques are used to filter and/or phase out one or more sideband pairs, leaving the carrier signal.
Claims9
A method of minimizing the bandwidth needed to transmit signals using angle modulation, the method comprising:
- providing a modulating input signal;
- phase modulating the modulating input signal using first phase modulation circuitry;
- phase shifting the modulating input signal by 90 degrees using first phase shift circuitry;
- phase modulating the 90 degree phase shifted modulating input signal using second phase modulation circuitry;
- phase shifting the modulating input signal by 180 degrees using second phase shift circuitry;
- phase modulating the 180 degree phase shifted modulating input signal using third phase modulation circuitry;
- phase shifting the modulating input signal by 270 degrees using third phase shift circuitry;
- phase modulating the 270 degree phase shifted modulating input signal using fourth phase modulation circuitry;
- and combining outputs of the first, second, third, and fourth phase modulation circuitry to thereby provide for phasing out one or more sideband pairs from the modulating input signal.
A system for suppressing sidebands in angle modulated signals comprising:
- first phase modulation circuitry modulates a modulation signal;
- first phase shift circuitry phase shifts the modulation signal by a first amount;
- second phase modulation circuitry modulates the shifted modulation signal;
- and
- second phase shift circuitry phase shifts the modulation signal by a second amount;
- third phase modulation circuitry modulates the modulation signal shifted by the second phase shift circuitry;
- third phase shift circuitry phase shifts the modulation signal by a third amount;
- fourth phase modulation circuitry modulates the modulation signal shifted by the third phase shift circuitry;
- and
- summing circuitry combines outputs of the first, second, third, and fourth phase modulation circuitry;
- wherein the first, second, and third phase shift circuitry shifts the modulation signal by 90, 180, and 270 degrees, respectively.
Dependencies are inferred from the claim text.