WO2006097033A1 - Systeme et procede de pre-traitement de demodulation d'un signal dans la bande de base - Google Patents

Systeme et procede de pre-traitement de demodulation d'un signal dans la bande de base Download PDF

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Publication number
WO2006097033A1
WO2006097033A1 PCT/CN2006/000348 CN2006000348W WO2006097033A1 WO 2006097033 A1 WO2006097033 A1 WO 2006097033A1 CN 2006000348 W CN2006000348 W CN 2006000348W WO 2006097033 A1 WO2006097033 A1 WO 2006097033A1
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WIPO (PCT)
Prior art keywords
signal
analog
amplifier
mixer
analog signal
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PCT/CN2006/000348
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English (en)
Chinese (zh)
Inventor
Ling Yue
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Huawei Technologies Co., Ltd.
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Application filed by Huawei Technologies Co., Ltd. filed Critical Huawei Technologies Co., Ltd.
Publication of WO2006097033A1 publication Critical patent/WO2006097033A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/16—Circuits
    • H04B1/26—Circuits for superheterodyne receivers

Definitions

  • the present invention relates to a baseband signal processing technique in a communication system, and more particularly to a demodulation preprocessing system and method for a baseband intermediate frequency signal.
  • the so-called baseband intermediate frequency signal demodulation preprocessing includes: converting a radio frequency signal into an intermediate frequency signal for providing to a demodulation unit, and performing anti-interference processing before demodulation.
  • how to improve the anti-interference performance, and thus improve the signal quality sent to the demodulation unit is a key point.
  • interference is an important factor affecting the normal operation of a base station.
  • One of the factors that cause interference is: Due to limited frequency resources, the frequencies used by different communication systems are close to each other, resulting in interference, such as: PHS forward channel and Wideband Code Division Multiple Access (WCDMA) and Interference between the reverse channels of the CDMA (1900 MHz band) due to the closeness of the frequency; mutual interference between the forward channel of the CDMA (800 MHz band) and the reverse channel of the GSM (Global System for Mobile Communications) due to the close frequency, and Other similar situations.
  • WCDMA Wideband Code Division Multiple Access
  • GSM Global System for Mobile Communications
  • Frequency planning refers to the reasonable allocation of frequency resources occupied by a system in space and time, so that the frequency used by the system and the frequency of other communication systems are as little as possible to generate mutual interference. In some cases, this method cannot reduce interference between systems.
  • CDMA450 uses a frequency band of 450 MHz, and there are also interference sources such as trunking communication systems and broadcasting stations in the frequency range. Among them, the frequency band used by the trunking communication system is 450MHz; the frequency used by the broadcasting station is concentrated in the 90MHz range. Due to the large transmission power, the 5th harmonic of the broadcast signal (the frequency range is 450MHz) will cause significant interference to the CDMA450 system.
  • Another method of the prior art is to add a filter in the baseband signal demodulation preprocessing system, but the above problem cannot be solved by using a general analog filter, because the interference source frequency is the same as the communication system frequency, and is in-band. In the case of interference, a typical analog bandpass filter cannot filter out noise in the same frequency band. Based on the above reasons, the more common methods are: The system obtains the digital intermediate frequency signal, and adopts the adaptive filtering technology (digital filter) to filter out the in-band interference. The principle is shown in the figure. minus 2-
  • the input signal (which is an analog signal) is amplified by the low noise amplifier 11 and input to the mixer 12 for mixing to obtain an intermediate frequency signal, and an analog/digital converter (A/D) 13 is used for mixing.
  • the IF analog signal is converted into a digital signal and sent to the adaptive filter 14 to filter out the noise.
  • the denoised signal can be further processed, such as being sent to the demodulator for demodulation.
  • the adaptive filter is a digital filter, and the essence is that the digital domain is filtered by a certain software algorithm. Therefore, the adaptive filter cannot be applied to the filtering of the intermediate frequency noise of the analog system.
  • electronic components need to work in a certain level range (that is, have a certain dynamic range).
  • the level of the interference signal is strong, in the digital filtering system, the simulation cannot be performed due to the dynamic limitation of the analog-to-digital converter.
  • the interference signal is converted into a digital signal without distortion, and then filtered by an adaptive filter; the filtering principle of the adaptive filter is to dynamically find the interference frequency and filter out the signal of the interference frequency. Therefore, the adaptive filter also filters out the wanted signal at that frequency.
  • the input signal clip carries the interference signal. After the adaptive filter is output, although the interference signal is filtered out, the useful signal also has a spectral loss in the interference frequency range.
  • the problem to be solved by the present invention is to provide a baseband signal demodulation preprocessing system and method, which can perform anti-interference processing in an analog domain or a digital domain; moreover, when the system itself performs anti-interference processing, It does not cause a loss of spectrum in the useful signal.
  • the technical problem further solved by the present invention is to provide a baseband signal demodulation preprocessing system and method, which can meet the requirements of the dynamic range of the system when anti-jamming.
  • the baseband signal demodulation preprocessing system of the present invention includes an amplifier, a mixer and a limiting circuit; the amplifier will receive the radio frequency simulation The signal is preamplified; the mixer obtains an intermediate frequency analog signal by nonlinearly transforming the RF analog signal amplified by the amplifier and the local oscillator signal; the limiting circuit is connected in series with the amplifier and the mixer, and is high The amplitude is limited by the level of the interfering signal at the useful signal level.
  • an analog/digital converter and an adaptive filter are also included.
  • the analog/digital converter is configured to convert the clipped intermediate frequency analog signal into an intermediate frequency digital signal; the adaptive filter receives the intermediate frequency digital signal output by the analog/digital converter, and performs digital filtering processing.
  • the limiting circuit can be connected in series with the amplifier to receive the radio frequency analog signal, and after the limiting process, send the radio frequency analog signal to the amplifier; or, the limiting The circuit is connected between the amplifier and the mixer, receives the RF analog signal amplified by the amplifier, and sends the RF analog signal to the mixer after limiting processing; or, the limiting circuit is serially connected to the mixer After the frequency converter, the intermediate frequency analog signal output by the mixer is received and subjected to limiting processing.
  • the limiting circuit is implemented by an antistatic diode, or the limiting circuit is implemented by a PIN limiting diode.
  • the baseband signal demodulation preprocessing method of the present invention comprises: preamplifying a received radio frequency analog signal; and obtaining an intermediate frequency analog signal by nonlinearly transforming the radio frequency analog signal and the local oscillator signal amplified by the amplifier; It also includes: Amplitude limiting of the level of the interfering signal above the useful signal level.
  • the amplitude limitation is performed by a radio frequency analog signal before the preamplification; or the amplitude limitation is performed on the preamplified radio frequency analog signal; or the amplitude limitation is a needle intermediate frequency simulation. Signal implementation.
  • the method further includes: converting the clipped-processed intermediate frequency analog signal into an intermediate frequency digital signal; and performing digital filtering processing on the intermediate frequency digital signal.
  • the limiter circuit is used in the present invention to limit the interference level and reduce the energy of the noise in the signal. Therefore, the purpose of anti-interference is achieved, and the signal-to-noise ratio of the signal in the system is improved. Also, since the limiter circuit only limits the level of in-band interference, rather than filtering out all signals (including useful signals) in the corresponding frequency range. Therefore, no loss of the useful signal in the spectrum is generated.
  • the limiter circuit since the limiter circuit operates in the analog domain instead of the digital domain, it implements anti-interference processing at the intermediate frequency stage of the system analog signal, and thus the present invention can be applied to the analog system.
  • Baseband signal demodulation preprocessing Similarly, the analog signal after the interference suppression circuit is processed by the analog-to-digital conversion can also be provided to the digital system.
  • the system of the present invention can be An analog demodulation system or digital demodulation system provides anti-interference pre-processing.
  • an adaptive filtering technique is added to the system of the present invention (i.e., after the system is subjected to clipping processing, the signal is converted into a digital signal, and then filtered by an adaptive filter), the The anti-interference performance of the pre-processing system; and, because the strong interference signal is first subjected to clipping processing (in the analog domain), the interference signal level satisfies the dynamic range of the analog-to-digital converter, and thus can be converted by analog-to-digital conversion.
  • the converter transforms into a digital signal and is filtered out in the adaptive filter. In fact, due to the presence of the limiter circuit, the anti-interference dynamics of the adaptive filter are improved.
  • the system can be used for the baseband signal demodulation preprocessing of the analog system.
  • the limiter circuit suppresses the level of the level, the level of the demodulated signal satisfies the dynamic range of the quadrature demodulation circuit, so that the circuit is not saturated, that is, the demodulation dynamics of the quadrature demodulation circuit is improved.
  • an antistatic diode or a PIN limiting diode is used to implement the limiting circuit required in the preprocessing system. Since the limiting circuit implemented by the diode is low in cost, the system cost of the preprocessing system of the present invention is reduced.
  • FIG. 1 is a prior art pre-processing system including an adaptive filtering technique
  • FIG. 2 is a schematic diagram of a limiting characteristic of a diode
  • FIG. 3 is a diagram of a limiting circuit
  • FIG. 4 is a diagram of a pre-processing system for demodulating a baseband signal according to the present invention.
  • FIG. 5 is a block diagram of a second embodiment of a baseband signal demodulation preprocessing system according to the present invention
  • FIG. 6 is a block diagram of a third embodiment of a baseband signal demodulation preprocessing system according to the present invention
  • 7 is a block diagram of a fourth embodiment of a baseband signal demodulation preprocessing system according to the present invention;
  • FIG. 5 is a block diagram of a second embodiment of a baseband signal demodulation preprocessing system according to the present invention
  • FIG. 6 is a block diagram of a third embodiment of a baseband signal demodulation preprocessing system according to the present invention
  • FIG. 8 is a block diagram of a fifth embodiment of a baseband signal demodulation preprocessing system according to the present invention.
  • DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The core idea of the present invention is: use a limiting technique to solve the interference problem in communication, and suppress the interference higher than the useful signal to achieve the purpose of anti-interference; at the same time, ensure that the demodulation circuit does not Saturated, that is: In the digital intermediate frequency circuit, the analog-to-digital converter is guaranteed to be unsaturated. In the analog circuit, the quadrature demodulation circuit is guaranteed to be unsaturated.
  • the baseband signal demodulation preprocessing system of the present invention mainly comprises a low noise amplifier, a limiting circuit and a mixer.
  • Low Noise Amplifier (LNA) in the circuit is mainly to amplify the RF signal received by the antenna to meet the amplitude requirements of the mixer in the preprocessing system.
  • the low noise amplifier is the first stage amplification circuit of the receiver, located behind the antenna unit.
  • a low noise amplifier can be used to improve the overall noise figure of the receiver.
  • a limiter circuit as known to those skilled in the art, the function of the limiter circuit is to limit the amplitude of the output signal within a certain range, that is, when the input voltage exceeds a certain threshold voltage value, the output voltage will be It is limited to a certain level (called the clipping level) and does not change with the input voltage.
  • the limiting circuit in the present invention can be divided into an upper limit amplitude circuit, a lower limit amplitude circuit and a bidirectional limiter circuit according to the limiting characteristics, and the specific implementation manner is as follows. In the present invention, a diode limiting circuit is recommended.
  • the diode used in the limiting circuit is recommended to use an antistatic diode (such as BAV99, etc.) and a PI limiting diode.
  • the limiting characteristics are shown in Fig. 2. Since the diode has better switching characteristics and lower cost, the system cost is reduced while ensuring the beneficial effects of the present invention.
  • the limiter circuit of Fig. 3 when there is no signal input at the input terminal, since the diode 31 is connected in reverse, the output voltage is zero.
  • the diode When the signal is input, if the input signal voltage is greater than the voltage E of the power supply 32, the diode is turned on, so that the maximum value of the output pulse of the circuit is the power supply voltage E and the forward voltage drop of the diode (such as 0.6V), that is, E+0.6. Is the threshold voltage of this limiter circuit.
  • the limiting circuit is an upper limit circuit. If the diodes are connected in reverse, the lower limit circuit is formed. Similarly, the diode can be connected in series with the input and output terminals, and the limiting circuit can also be realized.
  • the upper limit amplitude circuit or the lower limit amplitude circuit can also be realized by using the characteristics of the diode forward conduction reverse cutoff. By combining the upper limit amplitude circuit and the lower limit amplitude circuit, a bidirectional limiter circuit can be formed.
  • the limiting circuit can also be formed by the cut-off and saturation characteristics of the triode. This type of circuit also has the function of amplification. If it is required to meet higher technical requirements, it can also be constructed with an integrated operational amplifier. Limiting circuit. According to the amplification and limiting function of the triode, it can be One 6—
  • the low noise amplifier referred to in the present invention is combined with a limiter circuit to simultaneously achieve low noise amplification and amplitude limiting of the level of the interference signal above the useful signal level by the triode circuit.
  • a mixer or a mixer circuit (MIXER) that combines a radio frequency signal with a local frequency of a local oscillator signal to obtain a difference frequency or a sum frequency (the difference frequency or the sum frequency is fixed), Obtaining an IF signal, this change is also known as spectrum shifting.
  • MIXER mixer
  • MIXER mixer circuit
  • mixers are implemented in many ways, such as: double balanced ring switch mixers and 6FET ring mixers.
  • the baseband signal demodulation preprocessing system is constructed by connecting the low noise amplifier, the mixer and the limiter circuit in series. Since the output signal of the system is an analog signal, the output signal of the system can be directly input into the analog demodulation system. Since the limiting circuit limits the level of the interference signal and reduces the energy of the interference signal, the anti-interference effect is achieved. , the system is implemented to pre-process the anti-interference processing before the analog demodulation system. Similarly, the analog signal output by this system can be input to a digital demodulation system through an analog-to-digital converter.
  • the present invention also achieves pre-processing including anti-interference processing in the digital demodulation system.
  • the pre-processing system implements anti-interference processing before the analog demodulation system and the digital demodulation system; from another perspective, the system can replace the adaptation in the prior art before digital demodulation.
  • the filtering system implements anti-interference processing.
  • the mixer is connected in series with the low noise amplifier to receive a high frequency signal amplified by the low noise amplifier.
  • the limiter circuit can be connected in series between the low noise amplifier front end, the low noise amplifier and the mixer, or after the mixer.
  • the position where the limiter circuit is connected in series is determined by the slice level of the limiter circuit and the interference level in the actual signal; if the analog demodulation system is connected after the preprocessing system, the specific position of the limiter circuit in the system It is also necessary to determine the maximum linear input level of the analog quadrature demodulator. If the pre-processing system is connected to a digital demodulation system, the analog signal output by the system needs to be converted into a digital signal by an analog-to-digital converter.
  • FIG. 4 shows an embodiment of the present invention.
  • the mixer 42 is serially connected to the low noise amplifier 41, and the limiting circuit 43 is connected in series with the mixer 42 to limit the anti-interference processing.
  • the resulting output signal can be sent directly to the quadrature demodulation system 44 for analog demodulation, or after passing through the analog to digital converter 45, the resulting digital signal is sent to a digital demodulation system 46 for digital demodulation.
  • FIG. 5 and FIG. 6 are two other embodiments of the present invention.
  • the limiting circuit is connected in series between the low chirp amplifier and the mixer;
  • the limiter circuit is connected in series before the low noise amplifier.
  • digital filtering technology can be added, that is, the analog/digital converter receives the analog intermediate frequency signal subjected to the limiting anti-interference processing, and after analog-to-digital conversion, the obtained digital intermediate frequency signal is sent to the adaptive filtering.
  • the adaptive filter filters out signals in the frequency range of the interference signal to filter out the interference signal.
  • FIG. 7, FIG. 8 and FIG. 9 are respectively schematic diagrams showing an embodiment of adding an adaptive filtering technique to a preprocessing system.
  • the general system structure is as follows: The preprocessing system first performs limiting and anti-interference processing on the input signal, and the obtained intermediate frequency analog signal is converted into a digital intermediate frequency signal by an analog/digital converter, and sent to the adaptive filter. Digital filtering is performed.
  • the low noise amplifier in the system is connected in series before the mixer; meanwhile, as shown in FIG. 7, the limiting circuit is connected in series after the mixer; as shown in FIG. 8, the limiting circuit is serially connected to Between the low noise amplifier and the mixer; as shown in Figure 9, the limiter circuit is connected in series with the low noise amplifier.
  • the position where the limiter circuit is connected in series is determined by the slice level of the limiter circuit and the interference level in the actual signal, and since the analog intermediate frequency signal is also converted into a digital intermediate frequency signal for digital filtering processing in the system, The specific position of the limiter circuit in the system also needs to be determined in conjunction with the maximum linear input level of the analog-to-digital converter before the adaptive filter.
  • the lower the limiting level of the limiting circuit the closer the limiting circuit should be to the input of the preprocessing system.
  • the six specific implementation methods of the present invention are provided herein, which correspond to FIG. 4 to FIG. 9 respectively, and the implementation methods of the six pre-processing systems may be used alone or in combination with each other.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Noise Elimination (AREA)

Abstract

La présente invention décrit un système et un procédé de pré-traitement de démodulation d'un signal dans la bande de base. Ledit système de pré-traitement comprend un amplificateur, un système de mixage et un circuit limiteur. Ledit amplificateur pré-amplifie le signal analogique de fréquence radio reçu (HF). Ledit système de mixage mixe le signal analogique HF amplifié et le signal d'oscillation local par une transformation non linéaire afin d'obtenir un signal analogique de fréquence intermédiaire (IF). Ledit circuit limiteur est relié à l'amplificateur et au système de mixage en série et limite l'amplitude du niveau du signal d'interférence qui est supérieur au niveau du signal utile. Le système de prétraitement de démodulation du signal dans la bande de base de la présente invention est capable de fournir un pré-traitement anti-interférences pour un système de démodulation analogique et un système de démodulation numérique ou de fournir un pré-traitement anti-interférences lorsqu'il est associé à une technique de filtrage numérique. En vertu de l'utilisation du circuit limiteur, la plage dynamique du système est améliorée.
PCT/CN2006/000348 2005-03-14 2006-03-08 Systeme et procede de pre-traitement de demodulation d'un signal dans la bande de base WO2006097033A1 (fr)

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CN200510055505.9 2005-03-14
CN2005100555059A CN1835488B (zh) 2005-03-14 2005-03-14 一种基带解调预处理系统

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112838843A (zh) * 2020-12-30 2021-05-25 北京千方科技股份有限公司 信号调理装置及信号调理方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108134754B (zh) * 2018-01-09 2019-02-01 西安科技大学 一种吉比特连续可变速率的中频差分解调器
CN110336547B (zh) * 2019-06-21 2020-11-24 华中科技大学 一种大量程抗饱和数字式信号幅度解调方法及解调器
CN111162808A (zh) * 2019-12-31 2020-05-15 京信通信系统（中国）有限公司 射频接收电路、接收机和基站

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CN1047707C (zh) * 1992-05-06 1999-12-22 日本电气株式会社 移频键控接收机
CN1087120C (zh) * 1994-11-10 2002-07-03 松下电器产业株式会社 直接变频接收机

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JPH08162983A (ja) * 1994-12-05 1996-06-21 Hitachi Ltd 無線受信機

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CN1047707C (zh) * 1992-05-06 1999-12-22 日本电气株式会社 移频键控接收机
CN1087120C (zh) * 1994-11-10 2002-07-03 松下电器产业株式会社 直接变频接收机

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112838843A (zh) * 2020-12-30 2021-05-25 北京千方科技股份有限公司 信号调理装置及信号调理方法
CN112838843B (zh) * 2020-12-30 2024-02-27 北京千方科技股份有限公司 信号调理装置及信号调理方法

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CN1835488A (zh) 2006-09-20

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