Double superheterodyne receiver with independent frequency calibration of two local oscillators

• US 5,361,407 A
• Filed: 11/23/1992
• Issued: 11/01/1994
• Est. Priority Date: 12/02/1991
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Sakai, Tadashi, Sawada, Takeshi
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): WISLER, MARK
• Application Number:
  US07/980,549
• Time in Patent Office: 708 Days
• Field of Search: 455/315, 455/316, 455/317, 455/318, 455/319, 455/314, 455/258, 455/260, 455/207, 455/208, 455/209
• US Class Current: 455/209
• CPC Class Codes: H03B 2201/0291 and being controlled by a processing device, e.g. a microprocessor
• CPC Class Codes: H03D 1/24 for demodulation of signals wherein one sideband or the carrier has been wholly or partially suppressed receiver circuits H04B1/302
• CPC Class Codes: H03D 7/161 all the frequency changers being connected in cascade
• CPC Class Codes: H03J 7/065 the counter or frequency divider being used in a phase locked loop
• CPC Class Codes: H04B 1/26 for superheterodyne receivers multiple frequency-changing H03D7/16

Abstract

A superheterodyne receiver comprises a variable frequency oscillator of PLL (phase-locked loop) type for implementing a first local oscillator and a variable frequency oscillator not of PLL type for implementing a second local oscillator. At least the frequency of a first locally generated signal is varied at reception to vary a received frequency, the frequency of the first locally generated signal is set at frequency calibration to a level equal to the frequency of a first intermediate-frequency signal, the second intermediate-frequency signal is frequency-converted by a BFO signal to a signal having a frequency of voice band, and the frequency of a second locally generated signal is calibrated to set the frequency of the frequency-converted signal to a specified level.

Claims

1. A superheterodyne receiver performing a plurality of frequency converting operations and having at least a first mixer connected to receive a signal having a desired frequency and to a first local oscillator to produce a first intermediate-frequency signal, and a second mixer connected to an output of the first mixer and to a second local oscillator to produce a second intermediate-frequency signal, said receiver comprising:

a phase-locked loop for implementing said first local oscillator; and

means excluding a phase-locked loop and including a variable frequency oscillator for implementing said second local oscillator;

control means connected to control said first and said second local oscillators;

wherein said received signal is supplied to said first mixer the output of which is varied by varying at least a frequency generated by said first local oscillator in response to a control signal from said control means, a frequency of said first oscillator is frequency calibrated by said control means to a frequency of the first intermediate-frequency signal, the second intermediate-frequency signal supplied by said second mixer is frequency-converted by a beat-frequency oscillator signal to a signal having a frequency of voice band, and a frequency of said second local oscillator is frequency calibrated independently of said first local oscillator by said control means, whereby a signal resulting from the frequency conversion in said second mixer is set to a specified frequency.

2. A superheterodyne receiver according to claim 1, wherein said control means comprises:

a microcomputer whereby powering on said superheterodyne receiver or a user'"'"'s providing an input to said microcomputer executes a routine for frequency calibration.