Continuously variable phase frequency shift keying
View Patent ↗Method for modulating an RF signal includes the steps of modulating an RF signal using frequency shift keying (FSK) modulation to define a plurality of symbols ( 203 0 , 203 1 ). The FSK modulation includes transitioning the modulated signal ( 204 ) between at least two different frequencies (f 1 and f 0 ) during a guard period ( 210 ). The method includes the further step of varying a frequency of the modulated signal 204 during the guard period ( 210 ) in accordance with a predetermined rate of change. The predetermined rate of change is selected to minimize a bandwidth of the RF signal.
1. A method for modulating an RF signal, comprising
modulating an RF signal using frequency shift keying (FSK) modulation to define a plurality of symbols, said FSK modulation including transitioning an FSK tone between at least two different frequencies beginning at a transition start time;
defining a guard period time interval during which samples of the FSK tone are not used for identifying said plurality of symbols, said guard period extending a predetermined duration from said transition start time;
generating said FSK tone by using a sinusoidal waveform generator which determines a sinusoidal output sample value based on an input phase angle, and generates each said sample value by adding a delta phase angle to a previous said input phase angle; and
performing operations in a phase domain to vary a frequency of said FSK tone in accordance with a predetermined rate of change, said operations including selectively varying said delta phase angle during said guard period to change said frequency of said FSK tone in accordance with a selected frequency transition profile.
2. The method according to claim 1 , wherein said predetermined rate of change is selected to minimize a bandwidth of said RF signal.
3. The method according to claim 1 , wherein said frequency of said FSK tone is continuously monotonically varied between at least a first one of said two different frequencies to at least a second one of said two different frequencies.
4. The method according to claim 1 , wherein said performing step further comprises varying said frequency of said FSK tone during at least about 20% of a total time interval comprising said guard period.
5. The method according to claim 1 , wherein said performing step further comprises varying said frequency of said FSK tone during at least about 40% of a total time interval comprising said guard period.
6. The method according to claim 1 , wherein said performing step further comprises varying said frequency of said FSK tone during at least about 60% of a total time interval comprising said guard period.
7. The method according to claim 1 , wherein said predetermined rate of change is linear.
8. The method according to claim 1 , wherein said predetermined rate of change is non-linear.
9. The method according to claim 1 , further comprising selecting said FSK modulation to be a continuous phase frequency shift modulation (CPFSK).
10. The method according to claim 1 , wherein said frequency is continuously varied in accordance with a pattern defined by a raised cosine curve.
11. A method for modulating an RF signal, comprising
modulating an RF signal using frequency shift keying (FSK) modulation to define a plurality of symbols, said FSK modulation including transitioning an FSK tone between at least two different frequencies beginning at a transition start time;
defining a guard period time interval during which samples of the FSK tone are not used for identifying said plurality of symbols, said guard period extending a predetermined duration from said transition start time;
generating said FSK tone by using a sinusoidal waveform generator which determines a sinusoidal output sample value based on an input phase angle, and generates each said sample value by adding a delta phase angle to a previous said input phase angle; and
performing operations in a phase domain to vary a frequency of said FSK tone, said operations including selectively varying said delta phase angle during said guard period to change said frequency of said FSK tone in accordance with a predetermined profile selected to minimize an RF bandwidth of said RF signal.
12. The method according to claim 11 , wherein said frequency is continuously varied in accordance with a pattern defined by a raised cosine curve.
13. A method for modulating an RF signal, comprising
modulating an RF signal using frequency shift keying (FSK) modulation to define a plurality of symbols, said FSK modulation including transitioning an FSK tone between at least two different frequencies beginning at a transition start time;
defining a guard period time interval during which samples of the FSK tone are not used for identifying said plurality of symbols, said guard period extending a predetermined duration from said transition start time;
generating said FSK tone by using a sinusoidal waveform generator which determines a sinusoidal output sample value based on an input phase angle, and generates each said sample value by adding a delta phase angle to a previous said input phase angle;
performing operations in a phase domain to vary a frequency of said FSK tone, said operations including selectively varying said delta phase angle during said guard period to change said frequency of said FSK tone in accordance with a predetermined profile that is exclusive of frequency discontinuities;
wherein said operations exclusively vary a frequency of said FSK tone during at least about 20% of a total time interval comprising said guard period in accordance with a predetermined rate of change selected to minimize an RF bandwidth of said RF signal.
14. The method according to claim 13 , wherein said predetermined rate of change is selected to minimize a bandwidth of said RF signal.
15. The method according to claim 13 , wherein said FSK tone frequency is continuously monotonically varied between at least a first one of said at least two different frequencies to at least a second one of said two different frequencies.
16. The method according to claim 13 , wherein said predetermined rate of change is linear.
17. The method according to claim 13 , wherein said predetermined rate of change is non-linear.
18. The method according to claim 13 , further comprising selecting said FSK modulation to be a continuous phase frequency shift modulation (CPFSK).
19. The method according to claim 13 , further comprising selecting said predetermined rate of change to concentrate spectral energy between at least a first one of said two different frequencies and a second one of said two different frequencies.
20. The method according to claim 13 , wherein said frequency is continuously varied in accordance with a pattern defined by a raised cosine curve.
21. The method according to claim 1 , wherein said delta phase angle is changed for each sample during said guard period.