Heterodyne radio receiver with plural variable frequency local oscillator signals

• US 5,606,736 A
• Filed: 11/09/1994
• Issued: 02/25/1997
• Est. Priority Date: 07/16/1991
• Status: Expired due to Fees

• Current Assignee: Parthus Limited
• Original Assignee: Symmetricom Incorporated (Microchip Technology Incorporated)
• Inventors: Hasler, Raymond J., Leisten, Oliver P.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): SOBUTKA, PHILIP
• Application Number:
  US08/336,794
• Time in Patent Office: 839 Days
• Field of Search: 455/314, 455/315, 455/318, 455/319, 455/334, 455/22, 455/207, 455/196.1, 455/197.2, 455/258, 455/259, 455/260, 455/76, 342/357
• US Class Current: 455/314
• CPC Class Codes: G01S 19/32 Multimode operation in a single same satellite system, e.g. GPS L1/L2
• CPC Class Codes: G01S 19/33 Multimode operation in different systems which transmit time stamped messages, e.g. GPS/GLONASS
• CPC Class Codes: G01S 19/36 relating to the receiver frond end
• CPC Class Codes: H03B 19/00 Generation of oscillations by non-regenerative frequency multiplication or division of a signal from a separate source transference of modulation from one carrier to another H03D7/00
• 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: H03D 7/163 the local oscillations of at least two of the frequency changers being derived from a single oscillator
• CPC Class Codes: H04B 1/26 for superheterodyne receivers multiple frequency-changing H03D7/16

Abstract

A satellite navigation receiver uses common dual-conversion superheterodyne and frequency synthesizer circuitry for receiving signals from both the GPS and the GLONASS satellite navigation systems. Successive first and second frequency down-converters in the receiver chain are fed by first and second local oscillator signals which are both variable in frequency such that the frequency of the first local oscillator signal is an integral multiple (preferably 8) of the second local oscillator signal. This relationship is provided by a binary divider (32) at least a portion of which may form part of a digital frequency synthesizer loop.

Claims

1. A superheterodyne radio receiver comprising at least two successive frequency down-converters arranged to be fed by respective first and second local oscillator signal sources, and further comprising a frequency synthesizer providing signal sources and a reference oscillator coupled to said synthesizer, said reference oscillator operable at a reference oscillator frequency, wherein, for tuning the receiver to a plurality of different receiving frequencies separated by the predetermined equal frequency spacing of a series of transmission channels, the frequencies of the said sources are variable and related by the expression f_L01 =X₁ f_L02, where f_L01 and f_L02 are the frequencies of said first and said second of the said sources, respectively, and x is a fixed integer in at least one mode of operation of the receiver, and means for varying the frequency f_L02 of said second source in a series of frequency increments Δ

f_L02 associated with said equal frequency increments and equal to a factor common to said equal frequency spacing and said reference oscillator frequency, having only two frequency down-converters, wherein said frequency synthesizer is arranged such that the frequencies of said local oscillator signal sources are variable in respective increments Δ

f_L01 and Δ

f_L02 such that the sum (Δ

_fL01 +Δ

_fL02) is equal to the predetermined frequency spacing, and wherein the integer X is equal to 8.

2. A receiver according to claim 1 wherein said reference oscillator frequency is a multiple r of 10 MHz, where r=1, 2, 3, etc.

3. A superheterodyne radio receiver comprising at least two successive frequency down-converters arranged to be fed by respective first and second local oscillator signal sources, and further comprising a frequency Synthesizer providing signal sources and a reference oscillator coupled to said synthesizer, said reference oscillator operable at a reference oscillator frequency, wherein, for tuning the receiver to a plurality of different receiving frequencies separated by the predetermined equal frequency spacing of a series of transmission channels, the frequencies of the said sources are variable and related by the expression f_L01 =X₁ f_L02, where f_L01 and f_L02 are the frequencies of said first and said second of the said sources, respectively, and x is a fixed integer in at least one mode of operation of the receiver, and means for varying the frequency f_L02 of said second source in a series of frequency increments Δ

f_L02 associated with said equal frequency increments and equal to a factor common to said equal frequency spacing and said reference oscillator frequency, wherein said first and second local oscillator sources are constituted by said frequency synthesizer, said synthesizer having a digital frequency divider, which has an input associated with the first said source and an output forming the second said source, wherein said digital frequency divider comprises first and second binary divider portions connected in series and having division ratios of 2^p and 2^q respectively, where p and q are integers and p+q=3 in at least one mode of operation of the receiver, and wherein said frequency synthesizer further comprises a variable divider having an input coupled to the output of said first divider portion, a phase comparator having one input couple to an output of said variable divider and another input coupled to said reference oscillator, and a variable frequency oscillator coupled to an output of said comparator.

4. A receiver according to claim 3, wherein said reference oscillator comprises a reference frequency divider, the receiver further comprising mode switching means associated with said reference frequency divider and said variable divider for allowing configuration of the receiver in one mode of operation as a fixed frequency receiver with a fixed synthesizer loop division ratio and with first reference and comparison frequencies and, in another mode of operation, as a variable frequency receiver with a variable synthesizer loop division ratio and with second reference and comparison frequencies.

5. A superheterodyne radio receiver comprising at least two successive frequency down-converters arranged to be fed by first and second respective local oscillator signal sources, and further comprising a frequency synthesizer providing the said first and second signal sources, and a reference oscillator coupled to said synthesizer, said reference oscillator operable at a reference oscillator frequency, wherein, for tuning the receiver to a plurality of different receiving frequencies separated by predetermined equal frequency spacing of a series of transmission channels:

the frequencies of the said first and second sources are variable in a respective series of frequency increments associated with said different receiving frequencies;

the frequency of said first source being a constant integer multiple of the frequency of said second source; and

said predetermined frequency spacing being integer divisible by the frequency increment of said second source,

having two frequency down-converters, wherein said frequency synthesizer is arranged such that the frequency increments Δ

f_L01 and Δ

f_L02 of said first and second local oscillator signal sources feeding the two down-converters are related by the expressions;

space="preserve" listing-type="equation">Δ

f.sub.L01 +Δ

f.sub.L02 =Δ

f

where Δ

f is the said predetermined frequency spacing, and

space="preserve" listing-type="equation">X=(Δ

f/Δ

f.sub.L02)-1

where x is the ratio between the variable local oscillator frequencies.

6. A receiver according to claim 5, wherein the ratio X is equal to 8.