EP0992108A2 - Recepteur a frequence intermediaire - Google Patents

Recepteur a frequence intermediaire

Info

Publication number
EP0992108A2
EP0992108A2 EP99911996A EP99911996A EP0992108A2 EP 0992108 A2 EP0992108 A2 EP 0992108A2 EP 99911996 A EP99911996 A EP 99911996A EP 99911996 A EP99911996 A EP 99911996A EP 0992108 A2 EP0992108 A2 EP 0992108A2
Authority
EP
European Patent Office
Prior art keywords
signal
correction device
receiver
correction
signals
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP99911996A
Other languages
German (de)
English (en)
Inventor
Hermana W. H. De Groot
Marc V. Arends
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips Electronics NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics NV filed Critical Koninklijke Philips Electronics NV
Priority to EP99911996A priority Critical patent/EP0992108A2/fr
Publication of EP0992108A2 publication Critical patent/EP0992108A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D1/00—Demodulation of amplitude-modulated oscillations
    • H03D1/22—Homodyne or synchrodyne circuits
    • H03D1/2245—Homodyne or synchrodyne circuits using two quadrature channels

Definitions

  • the invention relates to an IF -receiver as described in the preamble of Claim 1.
  • the invention further relates to a correction device to be used in such an IF receiver.
  • an IF receiver and correction system which uses special test signals to determine correction factors. During a certain time these correction factors are assumed to be constant. After some time new test signals are applied to the IF tuner to determine new correction factors. For example to be cast by temperature changes, power supply changes, changes in the magnitude and form of the input signal and aging of the components.
  • One of the disadvantages of the known IF receiver is that such a IF receiver needs test signals or reference signals (for example a carrier tone) that has to be known beforehand, otherwise correction becomes much less accurate or even impossible.
  • a further disadvantage of the known IF receiver is that the known IF receiver cannot cope with frequency dependency without introducing enormous arithmetic complexity in the algorithm.
  • a first aspect of the invention provides an IF receiver as defined in Claim 1.
  • a second aspect of the invention provides a correction device as defined in Claim 4.
  • Analog quadrature receivers are used to get rid of the necessary image filtering before mixing down to an IF frequency. This is done by having an in-phase path, called I, and a quadrature path called Q.
  • the I and Q paths are supposed to have the same amplitude, but 90° degrees phase difference. With analog mixers there always will be a mis-match in amplitude and an error in-phase difference. In a practical analog front end, the maximum error is about ldB in amplitude and two degrees in phase between the I and Q path.
  • the amplitude in the I signal is 10% larger than the Q signal and the phase difference between them is 89 degrees in stead of 90 degrees.
  • This error will lead to a so-called frequency cross talk component, that is an attenuated version of the original signal, merit and complex communicated around 0 Hz.
  • the frequency can still has a component that falls back into the wanted signal bound, comes from the wanted signal itself. Because it is attenuated by 25- 35 dB, depending on the amount of phase and amplitude error, this usually does not give any problems.
  • the frequency cross talk component that falls back into the wanted signal band comes from one (or more) of the adjacent channels.
  • This signals in these adjacent channels might be stronger (up to 65 dB, depending on the system) than the wanted signal is. This gives rise to frequency cross talk component within the wanted signal band, that can be up to 35 dB stronger than the wanted signal itself. In these case correction of the phase and amplitude error is necessary.
  • a correction device comprising for example the Hilbert transform correction is able to correct amplitude and phase errors without any test or reference signals. It is independent of the corrector of the modulated signal.
  • Figure 1 a block schematic example of an IF receiver with correction device.
  • Figure 2 a block schematic example of the correction device in more detail.
  • Figure 3 the idea transfer of complex filters, whereby Figure A shows the pass filter for positive frequencies and Figure B the path filter for negative frequencies.
  • Figure 4 an example of the frequency spectra at different points in the correction device.
  • Figure 1 shows an IF tuner IFT of the low IF type.
  • the IF tuner receives an input signal comprising the wanted signal together with a lot of adjacent signals and so-called blocked signals from an (not shown) antenna.
  • the total signal is mixed down in respectively mixer MIX1 and mixer MIX2.
  • the mixer MIX1 supplies an in phase signal Ii to an A/D converter ADl the output of the A D converter ADl is supplied to an input of the correction device CD.
  • the other mixer MIX2 supplies a signal Iq to a second A/D converter AD2.
  • the A D converter AD2 supplies a digital signal to the second input of the correction device CD.
  • the signals Ii, and Iq can be supplied each via filters to the correction device.
  • the output of the correction device is coupled to an output O of the IF tuner.
  • the correction device corrects the phase and amplitude error.
  • Figure 2 shows an example of a correction device CD2 having a first input 121 for receiving a signal 112 and a second input 122 for receiving a signal IQ2. Both inputs are coupled to adaptive amplitude correction means AAC for correcting the amplitude.
  • the output of the adaptive amplitude correction means is mixed to the signal I with the mixer MIXCD1.
  • the output of the mixer is supplied to a first path filter FI for passing positive frequencies with imaginary coefficients and a second filter F2 for passing negative frequencies with imaginary coefficients
  • the input 122 is coupled to a third filter F3 for passing positive frequencies with imaginary coefficients and is further coupled to a fourth filter F4 for passing negative frequencies with real coefficients.
  • the output of the first and third filter FI, F3 are subtracted in a subtracter.
  • the output of the second and fourth filter F2 and F4 are coupled to an adder ADD1.
  • the output of the subtracter SUB1 and the output of the adder ADD1 are supplied to phase correction means FC.
  • the output of the phase correction FC is supplied to a mixer MIXCD2 which mixer receives at the other input the output signal of the adder ADD1.
  • the output of the subtracter SUB1 and the output of the mixer MIXCD2 are supplied to a subtracter SUB2 for supplying at its output the difference.
  • the output of the subtracter SUB2 is coupled with the output with the correction device CD2.
  • Figure 3 shows the ideal transfer of the complex filters, whereby in Figure 3 a the filter for positive frequencies is shown and Figure 3b the filter for negative frequencies is shown.
  • Figure 4 shows examples of the frequency spectra on different stages of the correction device between brackets the number of the stage is given (see Figure 2).
  • the continuous lines give the wanted frequency spectrum and the dashed lines give the unwanted frequency spectra.
  • Figure 4b shows an example of a frequency spectrum after the positive path filter FI. All positive signal components of the original spectrum ( Figure 4a) are maintained and are also merit to negative side of the spectrum.
  • Figure 4 only an overdue of the absolute magnitude of the frequency component is given.
  • Figure 4c an example of a frequency spectrum after the. negative filter F4 is given.
  • the unwanted signal is much bigger than the wanted signal if the signal magnitude on point 4 is much bigger than the signal magnitude on point 3.
  • This magnitude determination can for example be done by using a RMS value determination or power determination.
  • the correction vector can be calculated by division of the two signal magnitudes as a good estimation of the actual frequency cross talk.
  • the Q branch on point 4 in Figure 2 which contains the unwanted signal can be weakened in such a way that the weakened version corresponds with the unwanted frequency cross-talk components in the I-branch point 3 in Figure 2 after filtering. These weakening factor is called Z.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Noise Elimination (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Circuits Of Receivers In General (AREA)
  • Superheterodyne Receivers (AREA)

Abstract

Les récepteurs F.I. connus de la technique reçoivent un signal d'antenne et fournissent généralement un signal F.I.. Il se peut qu'un problème survienne et entraîne une erreur de phase et/ou de fréquence imputable, par exemple, à un canal adjacent. Pour surmonter ce problème, l'invention concerne un dispositif de correction capable de corriger l'erreur de phase et/ou de fréquence dans les signaux I et/ou Q.
EP99911996A 1998-04-23 1999-04-20 Recepteur a frequence intermediaire Withdrawn EP0992108A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP99911996A EP0992108A2 (fr) 1998-04-23 1999-04-20 Recepteur a frequence intermediaire

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP98201304 1998-04-23
EP98201304 1998-04-23
PCT/IB1999/000699 WO1999056388A2 (fr) 1998-04-23 1999-04-20 Recepteur a frequence intermediaire
EP99911996A EP0992108A2 (fr) 1998-04-23 1999-04-20 Recepteur a frequence intermediaire

Publications (1)

Publication Number Publication Date
EP0992108A2 true EP0992108A2 (fr) 2000-04-12

Family

ID=8233633

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99911996A Withdrawn EP0992108A2 (fr) 1998-04-23 1999-04-20 Recepteur a frequence intermediaire

Country Status (3)

Country Link
EP (1) EP0992108A2 (fr)
JP (1) JP2002519997A (fr)
WO (1) WO1999056388A2 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6785529B2 (en) * 2002-01-24 2004-08-31 Qualcomm Incorporated System and method for I-Q mismatch compensation in a low IF or zero IF receiver

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2215544B (en) * 1988-03-10 1992-02-19 Plessey Co Plc Apparatus for the correction of frequency independent errors in quadrature zero i.f. radio architectures
EP0343273B1 (fr) * 1988-05-27 1994-04-27 Deutsche ITT Industries GmbH Circuit de correction pour une paire de signaux numériques en quadrature
FR2639497B1 (fr) * 1988-11-21 1991-02-15 France Etat Demodulateur pour transmission numerique comportant un dispositif de correction automatique des defauts
IE64560B1 (en) * 1988-11-30 1995-08-23 Motorola Inc Digital automatic gain control
GB2249442A (en) * 1990-11-01 1992-05-06 Stc Plc Correction of quadrature phase error

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9956388A3 *

Also Published As

Publication number Publication date
WO1999056388A3 (fr) 1999-12-29
JP2002519997A (ja) 2002-07-02
WO1999056388A2 (fr) 1999-11-04

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