US 5,497,509 A · FM-PM receivers with increased sensitivity

Abstract

Signal processing apparatus (410), for processing angularly modulated signals, provides improved sensitivity by reducing both the deviation of the modulation and the frequency of the bandwidth filter below the value calculated by Carson's rule. The signal processing apparatus (410) includes a closed loop (438) and a phase locking oscillator (270, 304, 318, 332, or 392) that is interposed into the closed loop (438). Both the frequency of the angularly modulated signal and the deviations of the angular modulation are reduced in the closed loop (438), and the demodulated output of the angularly modulated signal is produced in a conductor (436) of the closed loop (438). The phase locking oscillator (270, 304, 318, 332, or 392) includes both a forward path (204) and a feedback path (206), and an output frequency of the phase locking oscillator (270, 304, 318, 332, or 392) is phase locked to a reference frequency. The phase locked output frequency, in a conductor (230), is used as an input to the closed loop (438), and a derived signal, in the conductor (436) of the closed loop (438), which is the demodulated output of the angularly modulated signal, is used to vary the phase locked output frequency in the conductor (230). This varying of the phase locked output frequency includes separately modulating a frequency in the forward path (204) and a frequency in the feedback path (206) of the phase locking oscillator (270, 304, 318, 332, or 392). Modulation of frequencies in both paths (204 and 206) is accomplished without changing the reference frequency.

Claims46

Dependent claims

A method for processing angularly modulated signals that includes the steps of preselecting an angularly modulated signal, filtering said angularly modulated signal, mixing said angularly modulated signal with an other signal, and producing a demodulated output of said angularly modulated signal, which method is characterized by:

a) reducing the required bandwidth of said filtering step below the value calculated by Carson's rule by modifying said preselected signal prior to said filtering step;
b) reducing the bandwidth of said filtering step below the value calculated by Carson's rule;
c) phase locking an output frequency to a reference frequency;
d) the first said reducing step comprises converting said angularly modulated signal as a function of said phase locked output frequency;
and
e) the first said reducing step further comprises D.C. modulating said phase locked output frequency as a function of said demodulated output without varying said reference frequency.

3 more elements

A method which comprises receiving an angularly modulated signal that includes modulation deviations, reducing said deviations subsequent to said receiving step, and producing a demodulated output of said angularly modulated signal subsequent to said reducing step, the improvement in which said reducing step is characterized by:

a) phase locking an output frequency to a reference frequency;
b) D.C. modulating said phase locked output frequency as a function of said demodulated output without varying said reference frequency;
and
c) converting said angularly modulated signal as a function of said phase locked output frequency.

1 more element

Signal processing apparatus (410) which comprises preselector means (420) for proselecting a modulated signal that includes deviations, reducing means (418 and 200, 236, 310, 330, or 390) for reducing said deviations, and processing means (416), including said reducing means, for producing a demodulated output of said modulated signal, the improvement in which said reducing means comprises:

phase locking oscillator means (270, 304, 318, 332, or 392) for supplying an output frequency to said processing means that is phase locked to a reference frequency (218 or 240);
and
D.C. modulator means (272, 306, 320, 334, or 394), being operatively connected (266, 268) to said demodulated output and to said phase locking oscillator means, for D.C. modulating said phase locked output frequency as a function of said demodulated output without changing said reference frequency.

Signal processing apparatus (410), comprising a closed loop (438), for processing angularly modulated signals, the improvement which is characterized by:

phase locking oscillator means (270, 304, 318, 332, or 392), having both a forward path (204) and a feedback path (206), being interposed into said closed loop, and having an output frequency that is phase locked to a reference frequency, for supplying said phase locked output frequency to said closed loop;
means (426) for deriving a signal from said closed loop;
D.C. modulator means (272, 306, 320, 334, or 394), being operatively interposed into said closed loop, being operatively connected to said phase locking oscillator means and to said derived signal, for D.C. modulating said feedback path in response to said derived signal without changing said reference frequency;
and
means (264), being operatively connected to said forward path and to said derived signal, for modulating said forward path in response to said derived signal.

2 more elements

Dependencies are inferred from the claim text.

FM-PM receivers with increased sensitivity

Life of this patent

FM-PM receivers with increased sensitivity

Life of this patent

Abstract

Claims46