WO1999056388A2 - If-receiver - Google Patents
If-receiver Download PDFInfo
- Publication number
- WO1999056388A2 WO1999056388A2 PCT/IB1999/000699 IB9900699W WO9956388A2 WO 1999056388 A2 WO1999056388 A2 WO 1999056388A2 IB 9900699 W IB9900699 W IB 9900699W WO 9956388 A2 WO9956388 A2 WO 9956388A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- signal
- correction device
- receiver
- correction
- signals
- Prior art date
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)
- Circuits Of Receivers In General (AREA)
- Superheterodyne Receivers (AREA)
- Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP99911996A EP0992108A2 (en) | 1998-04-23 | 1999-04-20 | If-receiver |
JP55388299A JP2002519997A (en) | 1998-04-23 | 1999-04-20 | IF receiver |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP98201304 | 1998-04-23 | ||
EP98201304.7 | 1998-04-23 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO1999056388A2 true WO1999056388A2 (en) | 1999-11-04 |
WO1999056388A3 WO1999056388A3 (en) | 1999-12-29 |
Family
ID=8233633
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB1999/000699 WO1999056388A2 (en) | 1998-04-23 | 1999-04-20 | If-receiver |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0992108A2 (en) |
JP (1) | JP2002519997A (en) |
WO (1) | WO1999056388A2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN100459413C (en) * | 2002-01-24 | 2009-02-04 | 高通股份有限公司 | System and method for i-q mismatch compensation in a low if or zero if receiver |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2215544A (en) * | 1988-03-10 | 1989-09-20 | Plessey Co Plc | Apparatus for the correction of frequency independent errors in quadrature zero I.F. radio architectures |
US4926443A (en) * | 1988-05-27 | 1990-05-15 | Deutsche Itt Industries Gmbh | Correction circuit for a digital quadrature-signal pair |
EP0371700A2 (en) * | 1988-11-30 | 1990-06-06 | Motorola, Inc. | Digital automatic gain control |
US4959619A (en) * | 1988-11-21 | 1990-09-25 | ETAT FRANCAIS, repreesente par la Ministre des Postes, Telecommunications et de 1'Espace (Centre National d'Etudes des Telecommunications) | Digital transmission demodulator including an automatic fault corrector |
GB2249442A (en) * | 1990-11-01 | 1992-05-06 | Stc Plc | Correction of quadrature phase error |
-
1999
- 1999-04-20 WO PCT/IB1999/000699 patent/WO1999056388A2/en not_active Application Discontinuation
- 1999-04-20 EP EP99911996A patent/EP0992108A2/en not_active Withdrawn
- 1999-04-20 JP JP55388299A patent/JP2002519997A/en active Pending
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2215544A (en) * | 1988-03-10 | 1989-09-20 | Plessey Co Plc | Apparatus for the correction of frequency independent errors in quadrature zero I.F. radio architectures |
US4926443A (en) * | 1988-05-27 | 1990-05-15 | Deutsche Itt Industries Gmbh | Correction circuit for a digital quadrature-signal pair |
US4959619A (en) * | 1988-11-21 | 1990-09-25 | ETAT FRANCAIS, repreesente par la Ministre des Postes, Telecommunications et de 1'Espace (Centre National d'Etudes des Telecommunications) | Digital transmission demodulator including an automatic fault corrector |
EP0371700A2 (en) * | 1988-11-30 | 1990-06-06 | Motorola, Inc. | Digital automatic gain control |
GB2249442A (en) * | 1990-11-01 | 1992-05-06 | Stc Plc | Correction of quadrature phase error |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN100459413C (en) * | 2002-01-24 | 2009-02-04 | 高通股份有限公司 | System and method for i-q mismatch compensation in a low if or zero if receiver |
Also Published As
Publication number | Publication date |
---|---|
JP2002519997A (en) | 2002-07-02 |
WO1999056388A3 (en) | 1999-12-29 |
EP0992108A2 (en) | 2000-04-12 |
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