Intermediate frequency FM receiver using analog oversampling to increase signal bandwidth

• US 5,483,695 A
• Filed: 04/13/1994
• Issued: 01/09/1996
• Est. Priority Date: 05/12/1993
• Status: Expired due to Term

• Current Assignee: CSEM Centre Suisse D'Electronique et de Microtechnique SA
• Original Assignee: CSEM Centre Suisse D'Electronique et de Microtechnique SA
• Inventors: Pardoen, Matthijs D.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): BANKS HAROLD, MARSHA DENISE
• Application Number:
  US08/226,856
• Time in Patent Office: 636 Days
• Field of Search: 455/205, 455/207, 455/208, 455/209, 455/276.1, 455/303, 455/304, 455/314, 455/324, 375/322, 375/334
• US Class Current: 455/314
• CPC Class Codes: H03D 2200/006 Signal sampling
• CPC Class Codes: H03D 3/007 by converting the oscillations into two quadrature related signals H03D3/245 takes precedence
• CPC Class Codes: H04B 1/28 the receiver comprising at least one semiconductor device having three or more electrodes
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22

Abstract

An FM receiver comprising a local oscillator (23), a heterodyning stage (24) and a demodulator stage (33). The heterodyning stage has a signal producing arrangement and a multiplier arrangement. The signal producing arrangement (25,26,27,29,30,31,32) produces n signals a₁ . . . a_n wherein each signal consists of a message signal modulated at the intermediate frequency of the receiver, and these signals a₁ . . . a_n are related by the expression

a.sub.i =cos [ω.sub.IF t+k.sub.f ∫.sup.t

A(t)*dt+Ω+π*(ⁱ /n)]

where ω_IF, k_f and Ω are constants, n is a positive integer greater than or equal to 2 and i takes the values of all positive integers up to and including n. The multiplier arrangement (28) multiplies the n signals together and thus produces an output signal from the heterodyning stage, wherein the message signal is modulated at a frequency of n times the intermediate frequency.

Claims

1. A radio receiver for receiving a selected FM signal in which a message signal A(t) modulates the frequency of a carrier signal, said radio receiver comprising:

a local oscillator for producing a local oscillator signal;

a heterodyning stage for heterodyning said selected FM signal with said local oscillator signal so as to reduce the frequency which is modulated by said message signal to an intermediate frequency; and

,

a demodulator stage for accepting an output signal from said heterodyning stage and extracting said message signal therefrom;

wherein said heterodyning stage comprises;

signal producing means for producing n signals a₁ . . . a_n wherein each of said n signals consists of said message signal A(t) modulated at said intermediate frequency, and said n signals a₁ . . . a_n are related by the expression

space="preserve" listing-type="equation">a.sub.i =cos {ω

.sub.IF t+k.sub.f ∫

.sup.t A(t)*dt+Ω

+π

*(.sup.i /n)}

where ω

_IF, k_f and Ω

are constants, n is a positive integer greater than or equal to 2 and i takes the values of all positive integers up to and including n, and

multiplier means for multiplying said n signals together and thus producing said heterodyning stage output signal wherein said message signal A(t) is modulated at a frequency of n times said intermediate frequency.

2. A radio receiver according to claim 1, wherein said signal producing means includes:

one or more phase shifters each for shifting the phase of said local oscillator signal so as to produce a phase-shifted signal, and

two or more mixers each for multiplying said selected FM signal with a different one of said phase-shifted signals and said local oscillator signal so as to produce one or more of said n signals.

3. A radio receiver according to claim 2, wherein said signal producing means further includes one or more phase shifters each for shifting the phase of one of said n signals so as to produce another one of said n signals.

4. A radio receiver according to claim 3, wherein said signal producing means further includes:

one or more RF phase shifters each for shifting the phase of said selected FM signal so as to produce a phase-shifted selected FM signal, and

two or more further mixers each for multiplying said local oscillator signal with a different one of said phase-shifted selected FM signal and said selected FM signal so as to produce one or more of said n signals.

5. A radio receiver according to claim 4, wherein said demodulator stage is tuned to a frequency of n times said intermediate frequency.

6. A radio receiver according to claim 5, wherein said heterodyning stage further comprises n limiters for removing any amplitude modulation from said n signals prior to their multiplication by said multiplier means.

7. A radio receiver according to claim 6, wherein said heterodyning stage further comprises one or more filters through each of which one of said n signals is passed.

8. A radio receiver according to claim 7, wherein each of said filters is tuned to said intermediate frequency.

9. A radio receiver according to claim 8, wherein said FM signal is a commercial broadcast FM radio signal.

10. A radio receiver according to claim 1, wherein said signal producing means includes one or more phase shifters each for shifting the phase of one of said n signals so as to produce another one of said n signals.

11. A radio receiver according to claim 1, wherein said signal producing means includes:

one or more RF phase shifters each for shifting the phase of said selected FM signal so as to produce a phase-shifted selected FM signal, and

two or more further mixers each for multiplying said local oscillator signal with a different one of said phase-shifted selected FM signal and said selected FM signal so as to produce one or more of said n signals.

12. A radio receiver according to claim 1, wherein said demodulator stage is tuned to a frequency of n times said intermediate frequency.

13. A radio receiver according to claim 1, wherein said heterodyning stage further comprises n limiters for removing any amplitude modulation from said n signals prior to their multiplication by said multiplier means.

14. A radio receiver according to claim 1, wherein said heterodyning stage further comprises one or more filters through each of which one of said n signals is passed.

15. A radio receiver according to claim 14, wherein each of said filters is tuned to said intermediate frequency.

16. A radio receiver according to claim 1, wherein said FM signal is a commercial broadcast FM radio signal.

17. A radio receiver according to claim 2, wherein said signal producing means further includes:

one or more RF phase shifters each for shifting the phase of said selected FM signal so as to produce a phase-shifted selected FM signal, and

two or more further mixers each for multiplying said local oscillator signal with a different one of said phase-shifted selected FM signal and said selected FM signal so as to produce one or more of said n signals.

18. A radio receiver according to claim 2, wherein said demodulator stage is tuned to a frequency of n times said intermediate frequency.

19. A radio receiver according to claim 2, wherein said heterodyning stage further comprises n limiters for removing any amplitude modulation from said n signals prior to their multiplication by said multiplier means.

20. A radio receiver according to claim 2, wherein said heterodyning stage further comprises one or more filters through each of which one of said n signals is passed.