FREQUENCY CONTROL SYSTEM FOR RECEIVER WITH HETERODYNE PRESELECTOR

• US 3,584,305 A
• Filed: 09/19/1968
• Issued: 06/08/1971
• Est. Priority Date: 09/20/1967
• Status: Expired due to Term

• Current Assignee: Babany Lucien, Bastide Paul, Leostic Joseph
• Original Assignee: Babany Lucien, Bastide Paul, Leostic Joseph
• Inventors: LEOSTIC JOSEPH, BABANY LUCIEN, BASTIDE PAUL
• Application Number:
  US04/760,854
• Time in Patent Office: 992 Days
• US Class Current: 455/316
• CPC Class Codes: H03B 21/02 by plural beating, i.e. for frequency synthesis ; Beating in combination with multiplication or division of frequency digital frequency synthesis using a ROM G06F1/02; digital frequency synthesis in general H03K; indirect frequency synthesis using a PLL H03L7/16
• CPC Class Codes: H03B 2201/0208 the means being an element with a variable capacitance, e.g. capacitance diode
• CPC Class Codes: H03B 2202/027 the noise being essentially proportional to the inverse of the frequency, i.e. the so-called 1/f noise
• CPC Class Codes: H03D 7/163 the local oscillations of at least two of the frequency changers being derived from a single oscillator

Abstract

Receiver with a heterodyne preselector fed by a first local oscillator, oscillator, and a frequency converter having a manually controllable second local oscillator. In order to maintain the desired relation between the frequencies of the two local oscillators, the output signals therefrom are intermodulated and the frequency of the resulting signal maintained in a corresponding desired range of frequency by means of a circuit which, according to the value of the frequency of the resulting signal, (i) initiates a frequency sweep of the first local oscillator (ii) causes this frequency to be increased by a predetermined amount or (iii) causes this frequency to be decreased by a predetermined amount.

Claims

1. A radio receiver having a heterodyne preselector fed by a voltage variable first local oscillator, which preselector feeds a frequency converter having a manually controllable second local oscillator providing stable frequencies but susceptible to scintillation effects, the output frequency of the first local oscillator being controlled to maintain a predetermined relationship between its frequency and the output frequency of the second oscillator by a control circuit comprising modulating means connected to said first and second local oscillators for modulating the output signals therefrom, voltage generator means for providing a control signal to said first local oscillator to maintain the predetermined relationship between the output frequencies of the local oscillators, said control signal being provided in the form of a sweep voltage in response to a first actuation of said voltage generator means, in the form of a step voltage of first polarity in response to a second actuation of said voltage generator means, and in the form of a step voltage of second polarity in response to a third actuation of said voltage generator means, and logic control means connected between said modulating means and said voltage generator means for effecting first actuation of said voltage generator means in response to detection of variation of the output of said modulating means outside of a prescribed range and for effecting second and third actuation of said voltage generator means in response to detection of variation of the output of said modulating means to one and the other extremes of said prescribed range, respectively

2. A receiver as defined in claim 1 wherein said modulating means includes a modulator having respective inputs connected to said first and second local oscillators and an output connected to a band-pass filter capable of passing a band of frequencies forming said prescribed range and defining the maximum permissible variation of the combined outputs of said local oscillators.

3. A receiver as defined in claim 2 wherein said logic control means includes a detector connected to the output of said filter and a first logic circuit Connected between said detector and said voltage generator means for effecting a first actuation of said generator means in absence of an output from said detector.

4. A receiver as defined in claim 1 wherein said logic control means includes a frequency discriminator connected to the output of said modulating means and a second logic circuit connected between said frequency discriminator and said voltage generator means for effecting a second or third actuation of said generator means in response to the output of said discriminator.

5. A receiver as defined in claim 4 wherein said second logic circuit includes positive and negative threshold devices to detect the polarity and a limit variation of the output of said discriminator and provide said second or third actuation, respectively, in response thereto.

6. A receiver as defined in claim 5 wherein said modulating means includes a modulator having respective inputs connected to said first and second local oscillators and an output connected to a band-pass filter capable of passing a band of frequencies forming said prescribed range and defining the maximum permissible variation of the combined outputs of said local oscillators.

7. A receiver as defined in claim 6 wherein said logic control means includes a detector connected to the output of said filter and a first logic circuit connected between said detector and said voltage generator means for effecting a first actuation of said generator means in absence of an output from said detector. 8 A receiver as defined in claim 7 wherein an amplifier is connected to the output of said filter and said detector and phase discriminator are connected in parallel to the output of said amplifier.

9. A radio receiver comprising:

a heterodyne preselector and a frequency converter serially connected, said preselector and said converter being respectively fed by a first and a second local oscillator, said second local oscillator being manually controlled and said first oscillator comprising frequency-varying means for varying the frequency thereof by means of a control signal;

first means, including a modulator, for deriving from the output signals of said two oscillators a further signal;

second means for controlling the frequency of said first oscillator through providing to said frequency-varying means a first control signal initiating a frequency sweep of said first oscillator, in response to a first actuation of said second means, a second control signal causing a frequency increase, of predetermined amount, of said first oscillator, in response to a second actuation of said second means and a third control signal causing a frequency decrease, of predetermined amount, of said first oscillator in response to a third actuation of said second means; and

third means connected between said first and second means for effecting first actuation of said second means in response to detection of variation of the frequency of said further signal outside of a prescribed range and for effecting second and third actuation of said second means in response to detection of variation of the output frequency of said further signal to one and the other extremes of said prescribed range, respectively.