# US 4,394,628 A · Modulation systems

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- Number: US 4,394,628 A
- Document ID: US4394628A
- Status: Granted
- Kind: A
- Application number: 04/172,054
- Filed: 1962-02-02
- Granted: 1983-07-19
- Earliest claimed: 1962-02-02
- Assignees: Raytheon Company
- Inventors: Donald S. Banks
- Web page: https://patentgrep.com/patent/US4394628A

## CPC

- H03C 3/00: Angle modulation (H03C5/00, H03C7/00 take precedence)
- H03C: MODULATION (masers or lasers H01S; coding, decoding or code conversion H03M)

## Abstract

1. Apparatus for deviating the frequency of a carrier signal in accordance with the frequency deviations of an intermediate frequency signal comprising: modulator means for varying the frequency of said carrier signal in accordance with a modulating signal; first mixer means for providing sum and difference frequency signals of the product of the modulated carrier signal and the frequency deviating intermediate frequency signal; filter means coupled to said mixer means and resonant at a predetermined one of said sum and difference frequency signals for providing a carrier control signal having a phase error component proportional to the deviation of said predetermined one of said sum and difference signals from its predetermined value; second mixer means for mixing said carrier control signal with said modulated carrier signal to produce an intermediate frequency control signal having a phase error component proportional to the deviation of said predetermined one of said sum and difference signals from its predetermined value; and means for comparing said intermediate frequency control signal with said frequency deviating intermediate frequency signal to provide said modulating signal.

## Claims

### Claim 1

Apparatus for deviating the frequency of a carrier signal in accordance with the frequency deviations of an intermediate frequency signal comprising:
modulator means for varying the frequency of said carrier signal is accordance with a modulating signal;
first mixer means for providing sum and difference frequency signals of the product of the modulated carrier signal and the frequency deviating intermediate frequency signal;
filter means coupled to said mixer means and resonant at a predetermined one of said sum and difference frequency signals for providing a carrier control signal having a phase error component proportional to the deviation of said predetermined one of said sum and difference signals from its predetermined value;
second mixer means for mixing said carrier control signal with said modulated carrier signal to produce an intermediate frequency control signal having a phase error component proportional to the deviation of said predetermined one of said sum and difference signals from its predetermined value; and
means for comparing said intermediate frequency control signal with said frequency deviating intermediate frequency signal to provide said modulating signal.

### Claim 2

In combination:
a first frequency source for producing a carrier signal;
a second frequency source for producing a frequency deviating intermediate frequency signal; and
apparatus for deviating the frequency of said carrier signal in accordance with the deviations of said intermediate frequency signal comprising:
modulator means for varying the frequency of said carrier signal in accordance with a modulating signal;
first mixer means for providing sum and difference frequency signals of the product of the modulated carrier signal and the frequency deviating intermediate frequency signal;
filter means coupled to said mixer means and resonant at a predetermined one of said sum and difference frequency signals for providing a carrier control signal having a phase error component proportional to the deviation of said predetermined one of said sum and difference signals from its predetermined value;
second mixer means for mixing said carrier control signal with said modulated carrier signal to produce an intermediate frequency control signal having a phase error component proportional to the deviation of said predetermined one of said sum and difference signals from its predetermined value; and
means for comparing said intermediate frequency control signal with said frequency deviating intermediate frequency signal to provide said modulating signal.

### Claim 3 (depends on 1)

The apparatus of claim 1 including means for 90.degree. phase rotating one of the signals to be mixed in said second mixer.

### Claim 4 (depends on 3)

The apparatus of claim 3 in which the filter means comprises a resonant cavity.

### Claim 5

Apparatus for deviating the frequency of a carrier signal in accordance with the deviations of an intermediate frequency signal comprising:
modulator means for varying the frequency of said carrier signal in accordance with a modulating signal;
first mixer means for providing sum and difference frequency signals of the product of the modulated carrier signal and the frequency deviating intermediate frequency signal;
filter means coupled to said mixer means and resonant at a predetermined one of said sum and difference frequency signals for providing a carrier control signal having a phase error component proportional to the deviation of said predetermined one of said sum and difference signals from its predetermined value;
second mixer means for mixing said carrier control signal with said modulated carrier signal to produce an intermediate frequency control signal having a phase error component proportional to the deviation of said predetermined one of said sum and difference signals from its predetermined value;
means for comparing said intermediate frequency control signal with said frequency deviating intermediate frequency signal to provide said modulating signal; and
means for varying the resonant point of said filter means in accordance with the direct current component of said modulating signal.