GMSK modulator formed of PLL to which continuous phase modulated signal is applied
First Claim
Patent Images
1. A modulator, comprising:
- a source of a continuous phase modulated signal, in which the continuous phase modulated signal carries a baseband information signal;
a voltage controlled oscillator having an oscillator output and a voltage control port;
a coupler on the oscillator output; and
a phase difference detector having a first input connected to the source of a continuous phase modulated signal, a second input connected to the coupler to form a feedback path and an output connected to supply a voltage error signal to the voltage control port, whereby the voltage controlled oscillator, the coupler and the phase difference detector form a phase locked loop and wherein the voltage error signal has a voltage proportional to an instantaneous phase difference between the continuous phase modulated signal and a signal appearing at the oscillator output.
1 Assignment
0 Petitions
Accused Products
Abstract
A Gaussian Minimum Shift Keying modulator that provides direct modulation of a carrier signal, produced by a single microwave high power voltage controlled oscillator. A continuous phase frequency shift keyed modulated signal with a modulation index of 0.5 is produced at the desired output frequency using a full 360 degree linear continuous phase modulator, controlled by a linear baseband signal that is the integral of the binary baseband information signal. This modulated signal is used as the reference signal for a phase locked high power voltage controlled oscillator. The phase locked loop provides frequency tracking and Gaussian spectral shaping to the modulated output signal.
-
Citations
22 Claims
-
1. A modulator, comprising:
-
a source of a continuous phase modulated signal, in which the continuous phase modulated signal carries a baseband information signal; a voltage controlled oscillator having an oscillator output and a voltage control port; a coupler on the oscillator output; and a phase difference detector having a first input connected to the source of a continuous phase modulated signal, a second input connected to the coupler to form a feedback path and an output connected to supply a voltage error signal to the voltage control port, whereby the voltage controlled oscillator, the coupler and the phase difference detector form a phase locked loop and wherein the voltage error signal has a voltage proportional to an instantaneous phase difference between the continuous phase modulated signal and a signal appearing at the oscillator output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A Gaussian minimum shift keying modulator for providing direct and efficient modulation of a microwave carrier signal, the modulator comprising:
-
a linear 360 degree continuous phase modulator that is controllable by a linear modulation signal to provide continuous phase frequency shift keying modulation of a carrier signal at a subharmonic frequency of a desired output frequency, and output a continuous phase frequency shift keying modulated signal, with a modulation index of 0.5, at the desired output frequency; a voltage controlled oscillator having a voltage control port and an oscillator output; a phase locked loop configured for providing a baseband error signal to the voltage control port of the voltage controlled oscillator, whereby the voltage controlled oscillator may track the frequency of the same frequency continuous phase frequency shift keying modulated signal, with a modulation index of 0.5, while imposing a filtering characteristic on the baseband error signal that shapes the voltage controlled oscillator modulated output signal to have a spectrum corresponding to a Gaussian minimum shift keying modulated signal spectrum; and a baseband modulation signal generator having means to integrate an input baseband binary information signal and to supply the integrated signal as a modulating signal in the continuous phase modulator. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
-
Specification