Two-point frequency modulation apparatus, wireless transmitting apparatus, and wireless receiving apparatus
A two-point frequency modulation apparatus is provided that reduces input timing difference and improves modulation accuracy. Two-point frequency modulation apparatus 10 has: PLL circuit 11 ; frequency division ratio generator 13 that generates the frequency division ratio in frequency divider 111 based on first digital baseband signal S 1 and carrier signal; adder 114 that adds second digital baseband signal S 2 to the output signal of loop filter 113 ; a delay index calculator (filter coefficient calculator 17 ) that calculates the delay index based on the magnitude of change in the amplitude of the output signal of adder 114 ; and a delay adjuster (digital filter 18 ) that shifts the phase of one of first digital baseband signal S 1 and second digital baseband signal S 2 according to the delay index so as to reduce the phase difference.
1. A two-point frequency modulation apparatus, comprising:
a PLL circuit;
a frequency division ratio setter that sets a frequency division ratio in a frequency divider in the PLL circuit based on a first digital baseband signal and a carrier signal;
a signal adder that adds a second digital baseband signal to an output signal of a loop filter;
a delay index calculator that calculates a delay index based on a magnitude of change in an amplitude of the signal combining the output signal and the second digital baseband signal; and
a delay adjuster that shifts a phase of one of the first digital baseband signal and the second digital baseband signal according to the delay index so as to reduce a phase difference between the first digital baseband signal and the second digital baseband signal.
2. The two-point frequency modulation apparatus of claim 1 , wherein the delay index calculator comprises a storage table that stores information representing the delay index.
3. The two-point frequency modulation apparatus according to claim 1 , wherein the delay adjuster comprises a digital filter that uses the delay index calculated by the delay index calculator as tap coefficients and shifts a phase of one of the first digital baseband signal and the second digital baseband signal according to the tap coefficients.
4. The two-point frequency modulation apparatus according to claim 1 , wherein the delay index calculator and the delay adjuster add the first digital baseband signal and the second digital baseband signal and detect a point where an amplitude value of a result of the addition is maximum so as to adjust a delay difference at a minimum.
5. The two-point frequency modulation apparatus according to claim 1 , wherein the delay index calculator and the delay adjuster add the first digital baseband signal and the second digital baseband signal, said second digital baseband signal being an inverted version of the first digital baseband signal, and detect a point where an amplitude value of a result of the addition is maximum so as to adjust a delay difference at a minimum.
6. The two-point frequency modulation apparatus according to claim 1 , further comprising an inverter that inverts the second digital baseband signal in relation to the first digital baseband signal.
7. The two-point frequency modulation apparatus according to claim 6 , wherein the inverter is provided in one of a signal input port that supplies the first digital baseband signal and the second digital baseband signal and the delay adjuster.
8. The two-point frequency modulation apparatus according to claim 1 , wherein the delay adjuster is provided on at least one of a supply route of the first digital baseband signal and a supply route of the second digital baseband signal.
9. A wireless transmitting apparatus comprising the two-point frequency modulation apparatus of claim 1 .
10. A wireless communication apparatus comprising the two-point frequency modulation apparatus of claim 1 .