Receiving device

1. A receiving device that receives a first modulated signal having a spread-spectrum modulation applied, and outputs a determination signal, the receiving device comprising:

a correlational operation circuit that executes a correlational operation between the first modulated signal and a first spread-spectrum signal string, and outputs a first correlational signal; and

a determination circuit that determines an amplitude value of the first correlational signal, and outputs the determination signal, the determination circuit including:

a first detector that outputs a first detection signal, when the first detector detects that a value of the first modulated signal exceeds a first threshold value,

a second detector that outputs a second detection signal, when the second detector detects that a value of the second modulated signal exceeds a second threshold value,

a detected signal selector that outputs the determination signal of a first value, when the first detection signal is inputted, and outputs the determination signal of a second value, when the second detection signal is inputted,

a first half-wave rectifier located on a pre-stage of the first detector, and

an amplitude inverter and a second half-wave rectifier located on a pre-stage of the second detector,

wherein the first half-wave rectifier applies a half-wave rectification to the first correlational signal, and outputs a first half-wave rectified signal to the first detector,

wherein the amplitude inverter inverts the amplitude value of the first correlational signal, and outputs a second correlational signal,

wherein the second half-wave rectifier applies the half-wave rectification to the second correlational signal, and outputs a second half-wave rectified signal to the second detector, and

wherein the second detector outputs the second detection signal when the second detector detects that a value of the second half-wave rectified signal exceeds the first threshold value.

2. A receiving device according to claim 1 , wherein:

the first detector includes:

a first amplitude adjuster that adjusts an amplitude value of the first half-wave rectified signal, and outputs a first adjusted signal; and

a first latch that synchronizes with a specified clock signal, latches a first signal of the first value when a value of the inputted first adjusted signal becomes equal to the first threshold value or more, latches a first signal of the second value when a value of the first adjusted signal becomes less than the first threshold value, and outputs the latched first signal as the first detection signal;

and the second detector includes:

a second amplitude adjuster that adjusts an amplitude value of the second half-wave rectified signal, and outputs a second adjusted signal; and

a second latch that synchronizes with a specified clock signal, latches a second signal of the first value when a value of the inputted second adjusted signal becomes equal to the first threshold value or more, latches a second signal of the second value when a value of the second adjusted signal becomes less than the first threshold value, and outputs the latched second signal as the second detection signal;

and the detected signal selector includes a third latch that inputs a third signal of the first value, latches a fourth signal of the first value, when the first detection signal is inputted as a clock signal, latches a fourth signal of the second value, when the second detection signal is inputted as a reset signal, and outputs the latched fourth signal as the determination signal.

3. A receiving device according to claim 2 , wherein the first detector further includes a first Schmidt trigger circuit located between the first amplitude adjuster and the first latch, and the second detector further includes a second Schmidt trigger circuit located between the second amplitude adjuster and the second latch, wherein:

the first Schmidt trigger circuit: possesses a third threshold value and a fourth threshold value that is lower than the third threshold value; generates a fifth signal of the first value, when a value of the first adjusted signal becomes equal to or higher than the third threshold, and the value of the first adjusted signal becomes equal to or higher than the fourth threshold; generates a fifth signal of the second value, when the value of the first adjusted signal becomes lower than the fourth threshold, and the value of the first adjusted signal becomes lower than the third threshold; and outputs the generated fifth signal to the first latch as a first Schmidt trigger signal;

and the second Schmidt trigger circuit: possesses the third threshold value and the fourth threshold value; generates a sixth signal of the first value, when a value of the second adjusted signal becomes equal to or higher than the third threshold, and the value of the second adjusted signal becomes equal to or higher than the fourth threshold; generates a sixth signal of the second value, when the value of the second adjusted signal becomes lower than the fourth threshold, and the value of the second adjusted signal becomes lower than the third threshold; and outputs the generated sixth signal to the second latch as a second Schmidt trigger signal.

4. A receiving device according to claim 1 , wherein the correlational operation circuit formed of plural shift registers includes:

a delay unit that stores and delays the first modulated signal by the number of signals contained in one cycle of the first spread-spectrum signal string; and

an arithmetic operation unit that multiplies each delayed signals of the first modulated signal by each spread-spectrum signals of the first spread-spectrum signal string for the number of signals contained in one cycle, adds each multiplied signals for the number of signals contained in one cycle, and outputs a sum of added signals as the first correlational signal.

5. A receiving device according to claim 4 , wherein the delay unit is formed of a first charge coupled device.

6. A receiving device according to claim 1 , further comprising a preprocessing circuit, wherein:

the preprocessing circuit preprocesses the first modulated signal in a manner that the maximum power of the first modulated signal becomes a specified value, and outputs a preprocessed signal to the correlational operation circuit.

7. A receiving device according to claim 1 , further comprising an optical/electrical converter located on a pre-stage of the correlational operation circuit, wherein:

the optical/electrical converter inputs a first optical modulated signal of an optical signal to convert it into an electrical signal, and outputs a converted signal to the correlational operation circuit as the first modulated signal.

8. A receiving device according to claim 7 , wherein the optical/electrical converter is formed of a second charge coupled device.