Receiving circuit

• US 6,600,795 B1
• Filed: 02/26/1999
• Issued: 07/29/2003
• Est. Priority Date: 11/30/1994
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Inogai, Kazunori, Ohta, Gen-ichiro, Sasaki, Fujio
• Primary Examiner(s): VO, DON NGUYEN
• Application Number:
  US09/258,418
• Time in Patent Office: 1,614 Days
• Field of Search: 375/316, 375/340, 375/343, 375/342, 375/349, 375/346, 375/355, 375/347, 375/267, 375/344, 375/328, 329/300, 329/304
• US Class Current: 375/343
• CPC Class Codes: H03D 1/2245 using two quadrature channels H03D1/2209 takes precedence
• CPC Class Codes: H03D 2200/0047 Offset of DC voltage or frequency
• CPC Class Codes: H03D 2200/005 Analog to digital conversion
• CPC Class Codes: H03D 2200/0082 Quadrature arrangements
• CPC Class Codes: H03D 7/165 at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature combined with amplitude demodulation H03D1/2245, combined with angle demodulation H03D3/007; N-path filters H03H19/002
• CPC Class Codes: H03F 2200/537 A transformer being used as coupling element between two amplifying stages
• CPC Class Codes: H03F 3/45475 using IC blocks as the active amplifying circuit
• CPC Class Codes: H03F 3/50 Amplifiers in which input is applied to, or output is derived from, an impedance common to input and output circuits of the amplifying element, e.g. cathode follower
• CPC Class Codes: H04B 1/0003 Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain digital baseband systems H04L25/00; digital modulation/demodulation H04L27/00; CDMA H04B1/707; TDMA H04B7/2643; image transmission H04N5/00
• CPC Class Codes: H04B 1/0032 with analogue quadrature frequency conversion to and from the baseband quadrature modulators and demodulators per se H03D3/007, H03C3/40
• CPC Class Codes: H04B 1/123 using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H
• CPC Class Codes: H04B 1/26 for superheterodyne receivers multiple frequency-changing H03D7/16
• CPC Class Codes: H04B 5/266 One coil at each side, e.g. with primary and secondary coils
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A receiving circuit mainly available in a digital modulation type communication system having a plurality of channels, which is capable of reducing power in a receiving system, simplifying the circuit and reducing the power consumption. Upside and downside frequencies corresponding to a central value between channels are separately supplied from a local frequency signal generating circuit 4 to first and second frequency converting circuits 2, 3 so that two output signals are developed with respect to one of a desired wave, upside channel and downside channel. The desired wave present in common in the fist and second frequency converting circuits 2, 3 is extracted in a common wave extracting circuit 5, and a frequency offset of ωo existing in the output of the common wave extracting circuit 5 is removed a frequency offset circuit 6 and further an unnecessary frequency component is filtered by a filter 8. In addition, the common wave extracting circuit 5 has transformers and, using its inductances, raises the difference between the common wave and the non-common wave within the circuit to more than two times that of a prior art.

Claims

1. A receiving circuit comprising:

first and second frequency converting circuits for accepting a received signal obtained through an antenna;

a local frequency signal generating circuit coupled to said first and second frequency converting circuits for generating middle frequencies between a radio carrier frequency of said received signal and radio carrier frequencies of adjacent upside and downside channels and further for outputting the upside frequency of the upside and downside two wave frequencies as a conversion frequency input to said first frequency converting circuit and for outputting the downside frequency thereof as a conversion frequency input to said second frequency converting circuit;

a common wave extracting circuit coupled to said first and second frequency converting circuits for extracting a component present in common in both outputs of said first and second frequency converting circuits;

a frequency offset circuit coupled to said common wave extracting circuit for removing a frequency offset remaining in an output of said common wave extracting circuit; and

a filter coupled to said frequency offset circuit for removing an unnecessary frequency component remaining in an output of said frequency offset circuit.

2. A receiving circuit as set forth in claim 1, wherein only said first frequency converting circuit is used for accepting said received signal, and after a frequency conversion by said first frequency converting circuit, a frequency-converted output of a side where no frequency conversion is effected by said first frequency converting circuit is obtained by another frequency converting circuit to attain two frequency-converted outputs necessary for the common wave extraction.

3. A receiving circuit as set forth in claim 1, further comprising local frequency generating means coupled to said frequency offset circuit, said local frequency generating means including:

a first frequency signal source for generating a signal with a frequency equal to a carrier frequency of a desired receiving signal;

first means for accepting a signal from said first frequency signal source to phase-shift the accepted signal by a phase amount of π

/2 with respect to a frequency of the accepted signal;

a second frequency signal source for generating a signal with a frequency equal to ½

of a frequency channel spacing;

second means for accepting a signal from said second frequency signal source to phase-shift a frequency of the accepted signal by a phase amount of π

/2;

a first quadrature modulator comprising a multiplier for receiving the two signals from said first and second frequency signal sources and a multiplier for receiving two signals from said first and second phase-shifting means; and

a second quadrature modulator comprising two multipliers for receiving one of the two signals from said first and second frequency signal sources through said phase-shifting means.

4. A receiving circuit as set forth in claim 1, further comprising local frequency generating means coupled to said frequency offset circuit, said local frequency generating means including:

a first frequency signal source for generating a frequency signal equal to a carrier frequency of a desired receiving signal;

first means for accepting a signal from said first frequency signal source to phase-shift the accepted signal by a phase amount of π

/2 with respect to a frequency of the accepted signal;

a second frequency signal source for generating a frequency signal equal to ½

of a frequency channel spacing;

second means for accepting a signal from said second frequency signal source to phase-shift a frequency of the accepted signal by a phase amount of π

/2;

multipliers for receiving the two signals from said first and second frequency signal sources; and

means for inverting the polarity of an output of one of said multipliers to add the polarity-inverted output to an output of the other multiplier.

5. A receiving circuit as set forth in claim 1, further comprising local frequency generating means coupled to said frequency offset circuit, said local frequency generating means including:

a frequency signal source for generating a frequency signal equal to a carrier frequency of a desired receiving signal;

means for accepting a signal from said frequency signal source to phase-shift the accepted signal by a phase amount of π

/2 with respect to a frequency of the accepted signal;

a quadrature modulator comprising two multipliers for accepting a frequency signal from said frequency signal source through said phase shifting means; and

means for inverting the polarity of an output of one of said two multipliers and for adding the plurality-inverted output to an output of the other multiplier.

6. A receiving circuit as set forth in claim 1, comprising:

means for analog-to-digital-converting first and second received signals obtained through one of said frequency converting circuits and said quadrature demodulating circuits;

first and second Fourier transformers for accepting digital outputs of said analog-to-digital converting means, respectively;

a correlator for accepting outputs of said first and second Fourier transformers at every frequency component;

a weighting function device for accepting an output of said correlator;

a weighting value multiplier for accepting an output of said weighting function device;

an adder for accepting said outputs of said first and second Fourier transformers;

means for inputting an addition result of said adder to said multiplier; and

an inverse Fourier transformer for accepting an output of said weighting value multiplier,

wherein an inverse Fourier transformed output of said inverse Fourier transformer is used as a desired wave extraction result.

7. A receiving circuit comprising:

first and second frequency converting circuits for accepting a received signal obtained through an antenna;

a local frequency signal generating circuit coupled to said first and second frequency converting circuits for generating middle frequencies between a radio carrier frequency of said received signal and radio carrier frequencies of adjacent upside and downside channels and further for outputting the upside frequency of the upside and downside two wave frequencies as a conversion frequency input to said first frequency converting circuit and for outputting the downside frequency thereof as a conversion frequency input to said second frequency converting circuit;

a first frequency offset circuit for removing a frequency offset contained in an output of said first frequency converting circuit;

a second frequency offset circuit for removing a frequency offset contained in an output of said second frequency converting circuit;

a common wave extracting circuit for extracting a component present in common in both outputs of said first and second frequency offset circuits; and

a filter for removing an unnecessary frequency component left in an output of said common wave extracting circuit.

8. A receiving circuit comprising:

first and second frequency converting circuits for accepting a received signal obtained through an antenna;

a local frequency signal generating circuit coupled to said first and second frequency converting circuits for generating middle frequencies between a radio carrier frequency of said received signal and radio carrier frequencies of adjacent upside and downside channels and further for outputting the upside frequency of the upside and downside two wave frequencies as a conversion frequency input to said first frequency converting circuit and for outputting the downside frequency thereof as a conversion frequency input to said second frequency converting circuit;

first quantizing means for quantizing an output fo said first frequency converting circuit;

second quantizing means for quantizing an output of said second frequency converting circuit;

a common wave extracting circuit for extracting a component present in common in both outputs of said first and second quantizing means;

a frequency offset circuit for removing a frequency offset remaining in an output of said common wave extracting circuit; and

a filter for removing an unnecessary frequency component left in an output of said frequency offset circuit.

9. A receiving circuit as set forth in claim 8, further comprising a digital frequency converting circuit, and wherein only said first frequency converting circuit is used for accepting said received signal and only one of said first and second quantizing means is used for quantization, and after the quantization by only one of said first and second quantizing means, a frequency-converted output of a side where no frequency conversion is performed by said first frequency converting circuit is obtained by said digital frequency converting circuit to obtain two frequency-converted digital outputs necessary for the common wave extraction.

10. A receiving circuit comprising:

first and second frequency converting circuits for accepting a received signal obtained through an antenna;

a local frequency signal generating circuit coupled to said first and second frequency converting circuits for generating middle frequencies between a radio carrier frequency of said received signal and radio carrier frequencies of adjacent upside and downside channels and further for outputting the upside frequency of the upside and downside two wave frequencies as a conversion frequency input to said first frequency converting circuit and for outputting the downside frequency thereof as a conversion frequency input to said second frequency converting circuit;

first quantizing means for quantizing an output of said first frequency converting circuit;

second quantizing means for quantizing an output of said second frequency converting circuit;

a first frequency offset circuit for removing a frequency offset contained in an output of said first quantizing means;

a second frequency offset circuit for removing a frequency offset contained in an output of said second quantizing means;

a common wave extracting circuit for extracting a component present in common in both outputs of said first and second frequency offset circuits; and

a filter for removing an unnecessary frequency component left in an output of said common wave extracting circuit.

11. A receiving circuit comprising:

first and second quadrature demodulating circuits for receiving a received signal obtained through an antenna;

a local frequency signal generating circuit coupled to said first and second quadrature demodulating circuits for generating middle frequencies between a radio carrier frequency of said received signal and radio carrier frequencies of adjacent upside and downside channels and further for outputting the upside frequency of the upside and downside two wave frequencies as a conversion frequency input to said first quadrature demodulating circuit and for outputting the downside frequency as a conversion frequency input to said second quadrature demodulating circuit;

a first common wave extracting circuit coupled to said first and second quadrature demodulating circuits for extracting a component present in common in both I outputs of said first and second quadrature demodulating circuits;

a second common wave extracting circuit coupled to said first and second quadrature demodulating circuits for extracting a component present in common in both a Q output of said first quadrature demodulating circuit and a Q output of said second quadrature demodulating circuit reversed in polarity;

a first frequency offset circuit for removing a frequency offset remaining in said I output extracted through said first common wave extracting circuit;

a second frequency offset circuit for removing a frequency offset remaining in said Q output extracted through said second common wave extracting circuit;

a first filter for removing an unnecessary frequency component remaining in an output of said first frequency offset circuit; and

a second filter for removing an unnecessary frequency component remaining in an output of said second frequency offset circuit.

12. A receiving circuit as set forth in claim 11, further comprising a frequency converting circuit, and wherein only one of said first and second quadrature demodulating circuits is used for accepting said received signal, and two outputs of said quadrature demodulating circuit are frequency-converted by said frequency converting circuit to obtain a frequency-converted output of a side where no quadrature demodulation is made, to obtain two quadrature-demodulated outputs necessary for the common wave extraction.

13. A receiving circuit comprising:

first and second quadrature demodulating circuits for receiving a received signal obtained through an antenna;

a local frequency signal generating circuit coupled to said first and second quadrature demodulating circuits for generating middle frequencies between a radio carrier frequency of said received signal and radio carrier frequencies of adjacent upside and downside channels and further for outputting the upside frequency of the upside and downside two wave frequencies as a conversion frequency input to said first quadrature demodulating circuit and for outputting the downside frequency as a conversion frequency input to said second quadrature demodulating circuit;

first and second frequency offset circuits for removing a frequency offset contained in common in I outputs and Q outputs of said first and second quadrature demodulating circuits;

a first common wave extracting circuit for extracting a component present in common in both said I outputs of said first and second frequency offset circuits;

a second common wave extracting circuit for extracting a component present in common in both said Q output of said first frequency offset circuit and said Q output of said second frequency offset circuit 6I reversed in polarity; and

first and second filters for removing unnecessary frequency components remaining in outputs of said first and second common wave extracting circuits.

14. A receiving circuit comprising:

first and second quadrature demodulating circuits for receiving a received signal obtained through an antenna;

a local frequency signal generating circuit coupled to said first and second quadrature demodulating circuits for generating middle frequencies between a radio carrier frequency of said received signal and radio carrier frequencies of adjacent upside and downside channels and further for outputting the upside frequency of the upside and downside two wave frequencies as a conversion frequency input to said first quadrature demodulating circuit and for outputting the downside frequency as a conversion frequency input to said second quadrature demodulating circuit;

first and second quantizing means for quantizing an I output and a Q output of said first quadrature demodulating circuit, respectively;

third and fourth quantizing means for quantizing an I output and a Q output of said second quadrature demodulating circuit, respectively;

a first common wave extracting circuit for extracting a component present in common in said I outputs of said first and third quantizing means;

a second common wave extracting circuit for extracting a component present in common in said Q output of said second quantizing means and said Q output of said fourth quantizing means reversed in polarity;

a first frequency offset circuit for removing a frequency offset remaining in said I output extracted through said first common wave extracting circuit;

a second frequency offset circuit for removing a frequency offset remaining in said Q output extracted through said second common wave extracting circuit;

a first filter for removing an unnecessary frequency component left in an output of said first frequency offset circuit; and

a second filter for removing an unnecessary frequency component left in an output of said second frequency offset circuit.

15. A receiving circuit as set forth in claim 14, further comprising a digital frequency converting circuit, and wherein only one of said first and second quadrature demodulating circuits is used for accepting said received signal and only said second and third quantizing means are used, and after the quantization by said quantizing means, two outputs of said quantizing means are frequency-converted by said digital frequency converting circuit to obtain a frequency-converted output of a side no quadrature demodulation is effected, to obtain two quadrature-modulated outputs necessary for the common wave extraction.

16. A receiving circuit comprising:

first and second quadrature demodulating circuits for receiving a received signal obtained through an antenna;

a local frequency signal generating circuit coupled to said first and second quadrature demodulating circuits for generating middle frequencies between a radio carrier frequency of said received signal and radio carrier frequencies of adjacent upside and downside channels and further for outputting the upside frequency of the upside and downside two wave frequencies as a conversion frequency input to said first quadrature demodulating circuit and for outputting the downside frequency as a conversion frequency input to said second quadrature demodulating circuit;

first and second quantizing means for quantizing an I output and a Q output of said first quadrature demodulating circuit, respectively;

third and fourth quantizing means for quantizing an I output and a Q output of said second quadrature demodulating circuit, respectively;

a frequency offset circuit for removing frequency offsets remaining in said I outputs and said Q outputs of said first to fourth quantizing means;

a first common wave extracting circuit for extracting a component present in common in the I outputs of said frequency offset circuit;

a second common wave extracting circuit for extracting a component present in common in the Q output and a polarity-reversed Q output of said frequency offset circuit;

a first filter for removing an unnecessary frequency component left in said I output extracted through said first common wave extracting circuit; and

a second filter for removing an unnecessary frequency component left in said Q output of said second common wave extracting circuit.

17. A receiving circuit comprising:

first and second frequency converting circuits for accepting a received signal obtained through an antenna;

a local frequency signal generating circuit coupled to said first and second frequency converting circuits for generating middle frequencies between a radio carrier frequencies of said received signal and radio carrier frequencies of adjacent upside and downside channels and further for outputting the upside frequency of the upside and downside two wave frequencies as a conversion frequency input to said first frequency converting circuit and for outputting the downside frequency thereof as a conversion frequency input to said second frequency converting circuit;

first quantizing means for quantizing an output of said first frequency converting circuit;

second quantizing means for quantizing an output of said second frequency converting circuit;

a correlator coupled to outputs of the first and second quantizing means for calculating a mutual correlation, and to a frequency offset circuit for removing a frequency offset remaining in an output of said correlator; and

a filter for removing an unnecessary frequency component left in an output of said frequency offset signal.