CN1454408A - Reducing the DC offset of a homodyne receiver - Google Patents
Reducing the DC offset of a homodyne receiver Download PDFInfo
- Publication number
- CN1454408A CN1454408A CN00819885.3A CN00819885A CN1454408A CN 1454408 A CN1454408 A CN 1454408A CN 00819885 A CN00819885 A CN 00819885A CN 1454408 A CN1454408 A CN 1454408A
- Authority
- CN
- China
- Prior art keywords
- signal
- local oscillator
- homodyne receiver
- receiver
- extended code
- 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.)
- Pending
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
Abstract
The invention relates to a homodyne receiver comprising a mixer to which the signal to be demodulated as well as another signal from a local oscillator are fed. The homodyne receiver is advantageously provided with a modulator for spreading the local oscillator signal by using a spreading code and with a demodulator for despreading the output signal of the mixer. The spread signal of the local oscillator inserted into the receive branch of the homodyne receiver can thereby be suppressed and does not lead to an unwanted DC offset.
Description
The present invention relates to be used for the signal of modulating is carried out the method and the homodyne receiver of demodulation on carrier frequency.The invention particularly relates to minimizing is offset according to the DC that principle produced in homodyne receiver.
Modern receiver is because of the former of cost and position thereby undertaken integrated by highland more and more.A kind of structure of height integrated receiver is so-called homodyne receiver, and wherein the signal that need receive need not to adopt intermediate frequency and directly is mixed to base band.This principle is known already; But when realizing, also can cause having the difficulty of so-called DC skew so far.
Set forth this problem significantly by Fig. 2.(be noted that at this, only consider a branch road of homodyne receiver for simplification.)
The signal 1 that needs to receive is given to frequency mixer 3 through amplifier 2.Equally, the signal of local oscillator 4 is given to this frequency mixer through desirable path 6, and local oscillator 4 is to be operated on the frequency of the need received signal 1 that is used to be mixed into base band (Fig. 2) at this.In the process of mixing, also can produce other frequency naturally, but it be lost interest in herein, and for example can get up to suppress them by suitable filtering.Therefore produce one in demodulator 9 by the d. c. voltage signal of demodulation.
But described local oscillator 4 has only a kind of limited isolation with respect to its surrounding environment, so the signal of local oscillator 4 can be coupled in the receiving branch of receiver by unfavorable path 7.This unfavorable coupling is to produce because of the electric capacity with phase shift φ.
Equally, as the signal 1 that need receive, this moment local oscillator 4 also be given to frequency mixer 3 by the signal of phase shift, and also be mixed to zero with the signals that local oscillator 4 was coupled into through desirable path 6 originally.Produce an additional direct current signal thus, promptly so-called DC skew, it and required signal superpose.
This skew has damaged analyzing and processing to received signal, thereby and causes the reduction of performance (sensitivity).
In the prior art, the compensation that at present DC is offset is to realize with extremely complicated mode.Having only some special systems is insensitive to this skew, because need the signal of transmission not have flip-flop, described DC is offset thereby can be eliminated by low-pass filtering.
Therefore task of the present invention is to provide a kind of method and a kind of homodyne receiver, wherein can reduce or eliminate described DC skew with simple mode.
According to the present invention, this task is solved by the described homodyne receiver of claim 1, and it has a frequency mixer, needs the signal of demodulation and another signal of local oscillator to this frequency mixer input.Described homodyne receiver also has one in addition and is used for modulator and a demodulator that is used for the output signal of frequency mixer is carried out de-spread of local oscillator signals being expanded by extended code.
The present invention also relates to a kind of mobile radio receiver with this type of homodyne receiver in addition, such as the base station of wireless communication system or travelling carriage.
The present invention also provides a kind of method that is used for the signal of modulating is carried out demodulation on carrier frequency, the wherein modulated signal and the signal of local oscillator carry out mixing, and to the demodulation once more of consequent output signal, wherein utilize an extended code to modulate the signal of local oscillator, and to carrying out de-spread by the output signal that described mixing produced.
Described extended code preferably has a kind of periodic square-wave curve.
Now also set forth other advantage of the present invention, feature and performance with reference to the accompanying drawings by embodiment.
Fig. 1 shows a kind of homodyne receiver with local oscillator signals of expansion briefly as solution of the present invention, and
Fig. 2 shows the homodyne receiver that prior art has undesirable coupling mechanism briefly.
Drawn the simply branch road important of homodyne receiver of Fig. 1 to the present invention.Opposite with prior art, the signal of local oscillator 4 is expanded with an extended code by modulator this moment, and is given to frequency mixer 3 through desirable path 6.The effect of this expansion this moment has two kinds: on the one hand, the modulation signal 1 that is given to the need reception of frequency mixer 3 through amplifier 2 utilizes the signal of local oscillator 4 to be mixed to zero, also is expanded by this oscillator on the other hand.The expansion of modulation signal is not that we want, and therefore must reverse once more by Solution Expander 5 before demodulation.This is easily, because extended code is known, and himself produces in receiver.This will realize according to the sampling of baseband signal.
On the other hand, unfavorable coupling mechanism described in the prior art can cause the spread signal of local oscillator 4 is coupled in the receiving branch.As indicated above, this signal will experience a phase shift φ with respect to ideal path 6.In this frequency mixer 3, will mix that two of described local oscillator are expanded this moment but signal that phase shift is arranged.The result of this mixing is a noise signal, and this also can show on mathematics: unequal two spread signals of phase place will be mixed into a uncorrelated signal, also be a noise signal.This noise can be eliminated by suitable filters.
Therefore, the signal of described local oscillator 4 of coming in through 7 couplings of undesirable coupling path is changed into noise, the DC skew can't causing resembling in the local oscillator signals of not expansion.Thereby the signal that the coupling by phase shift and expansion of described local oscillator 4 is come in is not influence to received signal, or has only less influence.
Inhibition to the phase shift signal of local oscillator 4 will be carried out according to spreading factor that is used to the signal of local oscillator 4 is expanded and amount of phase shift phi, because described phase shift reason is measuring of decorrelation.
Described extended code can be a kind of periodic square-wave curve or other various suitable forms for example.
The reference symbol table
1 modulated input signal
2 amplifiers
3 frequency mixers
4 local oscillators
5 Solution Expanders and demodulator
6 desirable paths
7 desirable paths
The spread signal of 8 local oscillators
9 demodulators
Claims (5)
1. homodyne receiver has a frequency mixer (3), needs the signal (1) of demodulation and another signal of local oscillator (4) to this frequency mixer input, it is characterized in that:
A kind of modulator and a kind of demodulator that is used for the output signal of frequency mixer (3) is carried out de-spread of local oscillator signals being expanded by extended code of being used for.
2. the homodyne receiver of claim 1 is characterized in that:
Described extended code is a kind of periodic square-wave curve.
3. mobile radio receiver has the described homodyne receiver of one of aforesaid right requirement.
4. be used for the signal of modulating is carried out the method for demodulation on carrier frequency, have following steps:
The signal of modulated signal with local oscillator (4) mixed, and
Output signal to described blend step is carried out demodulation,
It is characterized in that following steps:
Utilize an extended code that the signal of described local oscillator (4) is modulated,
Output signal to described blend step is carried out de-spread.
5. the method for claim 4 is characterized in that:
Described extended code is a kind of periodic square-wave curve.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/DE2000/003174 WO2002023712A1 (en) | 2000-09-12 | 2000-09-12 | Reducing the dc offset of a homodyne receiver |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN1454408A true CN1454408A (en) | 2003-11-05 |
Family
ID=5647922
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN00819885.3A Pending CN1454408A (en) | 2000-09-12 | 2000-09-12 | Reducing the DC offset of a homodyne receiver |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP1329018A1 (en) |
| JP (1) | JP2004509496A (en) |
| CN (1) | CN1454408A (en) |
| WO (1) | WO2002023712A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004049582A1 (en) * | 2002-11-27 | 2004-06-10 | Koninklijke Philips Electronics N.V. | Receiver for processing a received signal |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU2909795A (en) * | 1994-06-29 | 1996-01-25 | Honeywell Inc. | Spurious response rejecting mixer using spread spectrum techniques |
| US5548244A (en) * | 1994-11-14 | 1996-08-20 | Hughes Aircraft Company | Method and apparatus for eliminating DC offset for digital I/Q demodulators |
| JP2780692B2 (en) * | 1995-12-06 | 1998-07-30 | 日本電気株式会社 | CDMA receiver |
| JP2800796B2 (en) * | 1996-08-12 | 1998-09-21 | 日本電気株式会社 | CDMA synchronization acquisition circuit |
| US6516187B1 (en) * | 1998-03-13 | 2003-02-04 | Maxim Integrated Products, Inc. | DC offset correction for direct conversion tuner IC |
-
2000
- 2000-09-12 JP JP2002527042A patent/JP2004509496A/en not_active Withdrawn
- 2000-09-12 EP EP00963981A patent/EP1329018A1/en not_active Withdrawn
- 2000-09-12 WO PCT/DE2000/003174 patent/WO2002023712A1/en not_active Application Discontinuation
- 2000-09-12 CN CN00819885.3A patent/CN1454408A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP1329018A1 (en) | 2003-07-23 |
| WO2002023712A1 (en) | 2002-03-21 |
| JP2004509496A (en) | 2004-03-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C02 | Deemed withdrawal of patent application after publication (patent law 2001) | ||
| WD01 | Invention patent application deemed withdrawn after publication |