Automatic frequency control system by quadrature-phase in frequency or phase demodulating system

A process for automatically controlling frequency during quadrature phase demodulation of frequency or phase modulated signals, comprising the steps of:

• receiving frequency or phase modulated radio frequency signals exhibiting a carrier frequency;
• amplifying the radio frequency signals to provide amplified signals;
• mixing a first local frequency signal with said amplified signals to produce first intermediate signals;
• mixing a second local frequency signal with said amplified signals to produce second intermediate signals;
• said first and second local frequency signals exhibiting the same frequency as said carrier frequency, with said first and second local signals differing in phase;
• converting a phase relation between said first and second intermediate signals into digital signals by applying a formula MODULO (.pi./2.sup.n) to a comparison of phases of said first and second intermediate signals;
• generating a plurality of data signals on the basis of said digital signals, with said data signals representing information about changes of phase, on the basis of said digital signals, said data signals including a first interrupt signal representing changes in phase of said formula;
• storing said data signals representing said information during each period of a sampling signal;
• generating a demodulated signal by interpolating said stored data signals representing said information;
• determining an electrical current value accompanying said demodulated signal and generating a parameter value indicative of said electrical current value;
• and
• controlling generation of said first and second local frequency signals in dependence upon said parameter value.

A process for controlling frequency during quadrature phase demodulation of frequency modulated signals and phase modulated signals, comprising the steps of:

• converting a phase relation between first and second quadrature-phase intermediate frequency signals into digital signals by applying a formula MODULO (.pi./2.sup.n) to a comparison of phases of said first and second intermediate frequency signals;
• generating a plurality of data signals on the basis of said digital signals, with said data signals representing information about changes of phase, said data signals including a first interrupt signal representing changes in phase of said formula;
• generating a demodulated signal on the basis of said data signals representing said information, by interpolating said data signals representing said information;
• determining a direct current value characteristic of said demodulated signal and generating a parameter value indicative of said direct current value, said parameter value being comprised of a plurality of bits;
• controlling generation of first and second local oscillation frequency signals in dependence upon said parameter value.

A process for controlling frequency during quadrature phase demodulation of frequency or phase modulated signals, comprising the steps of:

• generating a plurality of local oscillation signals having the same frequency but differing in phase, for mixing with an input signal, representative of said frequency or phase modulated signals, to provide a plurality of phase differing intermediate signals;
• converting a phase relation between said plurality of phase differing intermediate signals into digital signals by applying a formula MODULO (.pi./2.sup.n) to phases of said phase differing intermediate signals;
• generating a plurality of data signals on the basis of said digital signals, with said data signals representing information about changes of phase, said data signals including a first interrupt signal representing changes in phase of said formula;
• generating a demodulated signal on the basis of said digital signals by interpolating said digital signals;
• determining a direct current value characteristic of said demodulated signal during a period of a sampling signal, and generating a parameter value indicative of said direct current value characteristic, said parameter value comprising a plurality of bits;
• and
• controlling said step of generating said plurality of local oscillation signals in dependence upon said parameter value.

A frequency control circuit, comprising:

• means for converting a phase relation between first and second intermediate frequency signals having the same frequency but differing in phase, into digital signals by comparing phases of said first and second intermediate frequency signals;
• means for generating a plurality of data signals on the basis of said digital signals, with said data signals representing information about changes of phase between said first and second intermediate frequency signals, said data signals including a first interrupt signal representing changes in phase;
• means for generating a demodulated signal on the basis of said data signals, by interpolating said data signals, and for determining a direct current value characteristic of said demodulated signal during a current period and generating a parameter value indicative of said direct current value;
• and
• means for generating said first and second intermediate frequency signals in dependence upon said parameter value.