WO2013044481A1 - Procédé et appareil permettant d'étendre la plage dynamique de réception d'un émetteur-récepteur radiofréquence dans un système de duplexage par répartition dans le temps (tdd) - Google Patents

Procédé et appareil permettant d'étendre la plage dynamique de réception d'un émetteur-récepteur radiofréquence dans un système de duplexage par répartition dans le temps (tdd) Download PDF

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Publication number
WO2013044481A1
WO2013044481A1 PCT/CN2011/080370 CN2011080370W WO2013044481A1 WO 2013044481 A1 WO2013044481 A1 WO 2013044481A1 CN 2011080370 W CN2011080370 W CN 2011080370W WO 2013044481 A1 WO2013044481 A1 WO 2013044481A1
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WIPO (PCT)
Prior art keywords
signal
switch
mode
receiving
rssi
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PCT/CN2011/080370
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English (en)
Inventor
Xiangkun Ma
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Thomson Licensing
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Publication date
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Priority to PCT/CN2011/080370 priority Critical patent/WO2013044481A1/fr
Publication of WO2013044481A1 publication Critical patent/WO2013044481A1/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
    • H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
    • H04B1/40—Circuits
    • H04B1/44—Transmit/receive switching
    • H04B1/48—Transmit/receive switching in circuits for connecting transmitter and receiver to a common transmission path, e.g. by energy of transmitter

Definitions

  • the present invention generally relates to TDD (Time Division Duplexing) system, and in particular, to method and apparatus for extending the receiving (Rx) dynamic range of RF (Radio Frequency) transceiver in TDD system.
  • TDD Time Division Duplexing
  • RF Radio Frequency
  • a Rx dynamic range of a RF transceiver is essentially the range of signal levels over which it can operate. The low end of the range is governed by its sensitivity whilst at the high end it is governed by its overload or strong signal handling performance. A RF transceiver might be blocked or damaged by an input signal with a power level higher than the high end of the Rx dynamic range of the transceiver. Therefore, the Rx dynamic range of a transceiver is an important factor that will influence the performance of a TDD communication system, especially for the system with CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) mechanism at MAC (Media Access Control) layer.
  • CSMA/CA Carrier Sense Multiple Access/Collision Avoidance
  • FIG. 1 is an exemplary block diagram showing a transceiver with a conventional solution for extending the Rx dynamic range of RF transceiver in TDD system.
  • the transceiver comprises a baseband processing part for processing baseband signals, including but not limited to demodulation and decoding of the signals.
  • the transceiver also comprises a transmitting link Tx for amplifying, filtering and up-converting signals outputted by the baseband processing part.
  • a power amplifier PA is also included for amplifying the signal from the transmitting link Tx into a desired power level.
  • the transceiver also comprises a RF switch for transmitting or receiving signals respectively in a transmitting (Tx) mode and a receiving (Rx) mode under the control of the baseband processing part via a control line.
  • the transceiver comprises a variable gain amplifier/LNA (Low Noise Amplifier) for extension of the dynamic range of the RF transceiver.
  • the LNA is used for reducing the NF (noise figure) of the transmitting link Tx.
  • the variable gain amplifier varies its gain according to the signal strength in order to extend the Rx dynamic range of RF transceiver.
  • the variable gain amplifier cannot change its gain by itself. So it has to be controlled by the baseband processing part via a control line.
  • the transceiver further comprises a receiving link Rx for transforming a signal from the variable gain amplifier into a baseband signal which is fed to the baseband processing part for baseband processing described above.
  • the baseband processing part in the transmission will generate a baseband signal which is then transformed into a RF signal by the Tx link.
  • the RF signal will be amplified by the power amplifier PA into a desired power level and then be transmitted by the RF switch which is under the control of the baseband processing part to be in a transmitting state (Tx mode).
  • the RF switch is under the control of the baseband processing part to be in a receiving state (Rx mode).
  • a received signal is fed to the variable gain amplifier via the RF switch and then amplified by the variable gain amplifier.
  • the amplified signal is transformed into a baseband signal which is fed to the baseband processing part for baseband processing.
  • the variable gain amplifier is controlled by the baseband processing part as a function of the power level of the input signal. That is, the gain of variable gain amplifier will be increased if the power level of the input signal is low and decreased (even to an inverse gain) if the power level of the input signal is high.
  • variable gain amplifier used in the conventional solution is expensive.
  • variable gain amplifier Since the state of the variable gain amplifier will be controlled by the baseband processing as described above, more signal exchanges are needed to control the variable gain amplifier.
  • the time delay might be an issue, especially for the control to the power of the variable gain amplifier. That is, when controlling the power of the amplifier, it will take a charging/discharging time to change the status of the power since normally the circuit has relatively large RC, which might lead to a loss of data head/tail or an oscillation.
  • a large signal directly inputted to the amplifier may damage the amplifier, especially the LNA.
  • a RF transceiver comprising: a RF switch having a receiving mode for receiving a signal and a transmitting mode for transmitting a signal; a low noise amplifier for amplifying the signal from the RF switch; a receiving link for transforming a signal from the low noise amplifier into a baseband signal; and a baseband processing part for processing signal from the receiving link, wherein when receiving a signal, the baseband processing part switches the RF switch between the receiving mode and the transmitting mode as a function of the power level of the signal compared to a threshold.
  • a method for controlling a RF transceiver having a RF switch comprising: (a) determining the power level of a signal received by the RF switch; (b) determining whether the RF switch operates in the receiving mode or the transmitting mode; (c) switching the RF switch between the receiving mode and the transmitting mode as a function of the results in (a) and (b).
  • Figure 1 is an exemplary block diagram showing a transceiver with a conventional solution for extending the Rx dynamic range of RF transceiver in TDD system;
  • Figure 2 is an exemplary block diagram showing a transceiver with a circuit for extending the Rx dynamic range of RF transceiver in TDD system according to an embodiment of the present invention
  • Figure 3(a) and 3(b) are exemplary diagrams showing the operation of the RF switch in the circuit for extending the Rx dynamic range of RF transceiver in TDD system according to an embodiment of the present invention
  • Figure 4 is an exemplary block diagram showing a circuit for extending the Rx dynamic range of RF transceiver in TDD system using RSSI as an indicator of power level of input signal according to an embodiment of the present invention
  • Figure 5 is a flow chart showing the work flow of a method for extending Rx dynamic range of the RF transceiver according to an embodiment of the present invention
  • Figure 6 is an exemplary diagram showing the structure of a RF transceiver designed according to the embodiment of the invention for testing purpose.
  • FIG. 2 is an exemplary block diagram showing a transceiver with a circuit for extending the Rx dynamic range of RF transceiver in TDD system according to an embodiment of the present invention.
  • the circuit according to an embodiment of the present invention as shown in Figure 2 does not need to use a variable gain amplifier for the receiving process to extend the Rx dynamic range of the transceiver.
  • the extension of the Rx dynamic range of the transceiver is achieved by a RF switch under the control of a baseband processing part. Since no variable gain amplifier is used, there is no necessity for a control thereon from the baseband processing part.
  • Figure 3(a) and 3(b) are exemplary diagrams showing the operation of the RF switch in the circuit for extending the Rx dynamic range of RF transceiver in TDD system according to an embodiment of the present invention.
  • the RF switch will operate in the Rx mode or Tx mode according to the power level of an input signal.
  • the RF switch When an input signal with small power level is received, the RF switch operates by default in the Rx mode as normal.
  • the RF switch When an input signal with large power level is received, the RF switch will operate in the Tx mode, by which the strong input signal is attenuated. Therefore, an expensive variable gain amplifier is not needed for extension of the Rx dynamic range of the transceiver.
  • a RF switch operating in the Tx mode will have a relatively large attenuation from its input port to its output port to the LNA for an input signal since there is no connection between the input port and the output port to the LNA (the input port is directly connected to the output port to the PA in this case) and only a small part of the energy of the input signal can be coupled to the output port to the LNA. Therefore, the input signal can be attenuated by the RF switch to a value that allows the LNA receiving signals from the RF switch to operate normally. It could be appreciated that the Rx link cannot operate normally for a strong input signal if the RF switch operates in the Rx mode.
  • Figure 3 shows the procedure of the RF switch switching from the Rx mode to the Tx mode when a strong signal is received. It can be appreciated that in the above case the RF switch will switch back to the Rx mode if a next signal received has a power level smaller than a threshold, which procedure will be described below in detail with reference to Figure 4.
  • the power level of the input signal can be evaluated by detecting a RSSI (Received Signal Strength Indicator) of the input signal.
  • RSSI Receiveived Signal Strength Indicator
  • a RF transceiver comprises a baseband processing part for processing baseband signals; a transmitting link Tx for amplifying, filtering and up- converting signals outputted by the baseband processing part; and a power amplifier PA for amplifying the signal from the transmitting link Tx into a desired power level; a RF switch for transmitting or receiving signals respectively in a Tx mode and a Rx mode, wherein when receiving signals the RF switch is being switched between the Rx and the Tx mode according to the RSSI value of the input signal under the control of the baseband processing part via a control line; a low noise amplifier (LNA) for amplifying the signal from the RF switch; and a receiving link Rx for transforming a signal from the LNA into a baseband signal which is fed to the baseband processing part for baseband processing.
  • LNA low noise amplifier
  • the baseband processing part comprises a RSSI detecting unit, a comparator; a logic mapping unit, and a RSSI compensating unit. It is appreciated that the baseband processing part will also comprise other units for baseband processing functions.
  • the RSSI detecting unit detects the RSSI value of the input signal.
  • physically the RSSI detecting unit is connected after the Rx link. Therefore, the RSSI value is detected after the Rx link, which is feasible for the purpose of RSSI detection since signal strength after the Rx link is in proportion to that before the RF switch. As described above, in this case the RF switch will be operating by default in the Rx mode initially.
  • the comparator receives the detected RSSI value and compares it with a first RSSI threshold which can be preset and stored in a memory, for example, a FLASH memory.
  • a first RSSI threshold can be set to be a middle value of the overlap of a RSSI range of the RF switch in the Rx mode and that in the Tx mode. Normally for the purpose of a stable operation of a RF switch, there will be a sufficient overlap of the above two RSSI ranges.
  • the first RSSI threshold can be simply set to be the middle value of the overlap.
  • the first RSSI threshold can be set to be a middle value of the overlap, that is, 60 in this case. It can be appreciated by a person skilled in the art that the RSSI threshold can be also set in the other methods in view of the specific application context and requirements of the RF transceiver.
  • the logic mapping unit receives the comparison result, based on which to control the operation mode of the RF switch. Specifically, if the detected RSSI value is equal to or greater than the first RSSI threshold, the logic mapping unit will send a message to the RF switch through the control line to trigger a switch of the operation mode of the RF switch from the Rx mode to the Tx mode. It can be appreciated that, if the detected RSSI value is smaller than the first RSSI threshold, the logic mapping unit will not trigger a switch of the operation mode of the RF switch which will keep operating in the Rx mode.
  • the operation mode of the RF switch can be stored in the FLASH memory so that the information will not be lost if the RF switch is power off. That is, when the RF switch is power on, the logic mapping unit can read the information on the previous operation mode of the RF switch from the FLASH memory.
  • the RSSI detecting unit When the RF switch operates in the Tx mode, the RSSI detecting unit will also detect the RSSI value of the input signal. In this case, the current RSSI value of the input signal will be calculated based on the detected RSSI and a RSSI compensation value in view of the attenuation of the RF switch operating in the Tx mode.
  • the baseband processing part comprises a RSSI compensating unit for providing the RSSI compensation value when the RF switch operates in the Tx mode.
  • the RSSI compensation value can be simply set to correspond to the gain difference of the RF switch between it is operating in the Tx mode and the Rx mode.
  • the RSSI compensation value is a fixed value which can be preset and stored in the FLASH memory for the compensation of the RSSI value of an input signal with any power levels.
  • a more accurate RSSI compensation value can be obtained if the power level of an input signal is also considered.
  • an operation load will be increased greatly at this stage since the RSSI compensation value needs to be calculated first and then the current RSSI value.
  • a more practical way is to use the RSSI compensation value of the last input signal for calculating the RSSI value of the current input signal on the assumption that in practice consecutive input signals will not have an abrupt change in the power level.
  • the RSSI compensation value of the current input signal can be used to calculate the RSSI value of the next input signal.
  • the current RSSI value can be calculated, for example, by an energy integral of the input signal in time domain added with the RSSI compensation value described above, which is a common technology in the art and will not be described in detail.
  • the comparator receives the calculated RSSI value of the input signal and compares it with a second RSSI threshold which can be preset and stored in the memory.
  • the logic mapping unit receives the comparison result, based on which to control the operation mode of the RF switch. Specifically, if the calculated RSSI value is equal to or smaller than the second RSSI threshold, the logic mapping unit will send a message to the RF switch through the control line to trigger a switch of the operation mode of the RF switch from the Tx mode to the Rx mode. It can be appreciated that, if the calculated RSSI value is larger than the second RSSI threshold, the logic mapping unit will not trigger a switch of the operation mode of the RF switch which will keep operating in the Tx mode.
  • the first and second RSSI thresholds can be set to be a same value or different values according to specific requirement of the RF transceiver, for example, design simplicity and circuit stability.
  • Figure 5 is a flow chart showing the work flow of the above process of the RF transceiver according to an embodiment of the present invention.
  • the RF switch in the transceiver is operating for receiving an input signal.
  • the RSSI value of the input signal is detected. Then the process goes to the step S505 wherein a determination is made on whether the RF switch is operating at the Rx mode or the Tx mode.
  • step S505 If it is determined in the step S505 that the RF switch is operating at a Rx mode, the process goes to the step S507 wherein a determination is made on whether the RSSI value is equal to or greater than a preset first threshold.
  • step S509 the RF switch is switched from the Rx mode into the Tx mode.
  • step S505 If it is determined in the step S505 that the RF switch is operating at a Rx mode, the process goes to the step S51 1 wherein a RSSI value is calculated based on the detected RSSI value of the input signal and a RSSI compensation value. Then at the next step S513, a determination is made on whether the calculated RSSI value is equal to or smaller than a preset second threshold.
  • step S513 If the determination result of the step S513 is "Yes", then at the next step S515, the RF switch is switched from the Tx mode into the Rx mode.
  • a conventional LNA instead of a variable gain amplifier, is used as a first stage amplifier in a RF transceiver, which will result in a reduction of cost.
  • the RF transceiver of the invention there is no necessity for the RF transceiver of the invention to have a control on the amplifier. Therefore, the design of the RF transceiver is simplified and a lower signal crosstalk can be achieved.
  • the RF switch in the RF transceiver of the present invention needs to be controlled by the baseband processing unit.
  • the RF switch is a kind of passive device, controls applied thereon will not result in a current variation.
  • the duration of charging or discharging is also not a concern for a passive device. Therefore, the RF transceiver of the invention has a shorter response time and a stable current.
  • FIG. 6 is an exemplary diagram showing the structure of a RF transceiver designed according to the embodiment of the invention for testing purpose.
  • the Rx signal is firstly fed into a duplexer, which could be part of the RF switch, for filtering the Rx signal as well as multiplexing a desired signal and other signals.
  • the signal is amplified by a LNA so that the Rx link has the good noise figure.
  • ATT in Figure 6 is the attenuator in the Rx link, which is used to match the impedance between the LNA and a BPF which denotes a band pass filter to be used to reject the noise and interference out of band.
  • a mixer change the frequency to the frequency at which the main chip can receive. And another BPF after the mixer rejects the interference involved by the mixer.
  • a balun is a transformer between the single port and difference port.
  • a baseband in Figure 6 carries out baseband processing of the signal.
  • Table 1 shows main parameters of each device of Rx link of the RF transceiver operating in the Rx mode: Table 1
  • the following table 2 shows main parameters of each device of Rx link of the RF transceiver operating in the Tx mode:
  • the RF switch operating in the Rx mode has an NF of 5.7dB and a Gain of 7dB, of which status is for small signals.
  • the noise power spectral density under a temperature of 25 °C is a constant, which is -174dBm/Hz.
  • the channel bandwidth is 20MHz
  • the overall noise power level -174+10lg ( 20 * 10 6 ) dBm « - 101 dBm.
  • the power level of an input signal is -70dBm
  • the power level of signal input to the baseband is -63dBm
  • the SNR of the signal to baseband is 25.3dB, in which range the system can work normally.
  • the Rx dynamic range of the RF transceiver is from -70 to -25dBm when the RF switch is in the Rx mode and the Rx dynamic range is from -35 to OdBm when the RF switch is in the Tx mode.
  • the RF switch will switch from Rx mode into Tx mode. It can be appreciated that with the conditions of the experiments, the Rx dynamic range is extended from - 70 ⁇ -25dBm into -70 ⁇ 0dBm at 54Mbps with this invention.

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

Abstract

La présente invention se rapporte à un procédé et à un appareil permettant d'étendre la plage dynamique de réception (Rx) d'un émetteur-récepteur radiofréquence (RF pour Radio Frequency) dans un système de duplexage par répartition dans le temps (TDD pour Time Division Duplex). L'appareil comprend : un commutateur RF qui comprend un mode de réception destiné à recevoir un signal, ainsi qu'un mode de transmission destiné à transmettre un signal ; un amplificateur à faible bruit destiné à amplifier le signal provenant du commutateur RF ; une liaison de réception destinée à transformer un signal provenant de l'amplificateur à faible bruit en un signal dans la bande de base ; et une partie de traitement en bande de base destinée à traiter le signal provenant de la liaison de réception. Lors de la réception d'un signal, la partie de traitement en bande de base commute le commutateur RF entre le mode de réception et le mode de transmission en fonction du niveau de puissance du signal par comparaison à un seuil.
PCT/CN2011/080370 2011-09-29 2011-09-29 Procédé et appareil permettant d'étendre la plage dynamique de réception d'un émetteur-récepteur radiofréquence dans un système de duplexage par répartition dans le temps (tdd) WO2013044481A1 (fr)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2513909A (en) * 2013-05-10 2014-11-12 Bae Systems Plc Duplexer
WO2016101096A1 (fr) * 2014-12-22 2016-06-30 Telefonaktiebolaget Lm Ericsson (Publ) Procédé de supervision de réception et unité radio
US9692583B2 (en) 2013-05-10 2017-06-27 Bae Systems Plc Duplexer

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1204900A (zh) * 1997-07-08 1999-01-13 冲电气工业株式会社 控制接收信号电平的方法
US20040063412A1 (en) * 2002-09-26 2004-04-01 Kim Hea Joung Attenuation of a received radio frequency signal
CN1489830A (zh) * 2001-01-29 2004-04-14 日本电气株式会社 时分多址收发机及其接收自动增益控制方法
CN2757434Y (zh) * 2004-07-01 2006-02-08 天宇通信集团有限公司 具有电源控制电路的收发器

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1204900A (zh) * 1997-07-08 1999-01-13 冲电气工业株式会社 控制接收信号电平的方法
CN1489830A (zh) * 2001-01-29 2004-04-14 日本电气株式会社 时分多址收发机及其接收自动增益控制方法
US20040063412A1 (en) * 2002-09-26 2004-04-01 Kim Hea Joung Attenuation of a received radio frequency signal
CN2757434Y (zh) * 2004-07-01 2006-02-08 天宇通信集团有限公司 具有电源控制电路的收发器

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2513909A (en) * 2013-05-10 2014-11-12 Bae Systems Plc Duplexer
US9692583B2 (en) 2013-05-10 2017-06-27 Bae Systems Plc Duplexer
WO2016101096A1 (fr) * 2014-12-22 2016-06-30 Telefonaktiebolaget Lm Ericsson (Publ) Procédé de supervision de réception et unité radio
US10298349B2 (en) 2014-12-22 2019-05-21 Telefonaktiebolaget Lm Ericsson (Publ) Receive supervision method and radio unit

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