JP2011188268A - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problems of a receiver which performs intermittent reception and uses amplitude modulation: high-speed AGC is required in an initial stage immediately after start-up, and low-speed AGC is required in a steady state, however, large CPU load and power consumption are required for achieving the high-speed AGC only by digital processing. <P>SOLUTION: In the high-speed AGC that tracks a transient received electric field level in the stage immediately after start-up, the receiver performs automatic gain control using an analogue RSSI obtained by envelope detection in analogue processing. In the low-speed AGC performs stable gain control in the steady state even under a fading environment, the receiver performs automatic gain control using digital RSSI (average power, peak power) obtained by the digital processing. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a receiver that automatically controls gain according to a received electric field level during intermittent reception (automatic gain control).

  A communication device that uses a modulation method that requires linearity of amplitude during demodulation, when receiving, automatic gain control (AGC) that autonomously changes the gain according to the reception level in order to secure a dynamic range of the reception electric field level. )It is carried out. Under a wireless communication environment, the level of a signal received by the receiving apparatus varies depending on propagation path characteristics. The receiver performs automatic gain control so that the signal level input to the demodulator is kept constant even if the input signal level of the propagation path varies. In automatic gain control, received signal strength indicator RSSI signals obtained by logarithmically amplifying an incoming received signal and detecting envelopes are used to change the gain and attenuation rate of the variable amplifier. Adjust the level.

  For the purpose of reducing power consumption, the receiving apparatus performs intermittent reception. Immediately after the start of reception and immediately after the rise of the signal waveform, automatic gain control needs to be performed instantaneously in order to follow the transient received electric field level. In the following description, automatic gain control executed in a short processing time is referred to as “high-speed AGC”. In a steady state where the signal waveform has risen, automatic gain control is performed in order to stably perform gain control even under a fading environment. The automatic gain control at this time is not required to be as responsive as the “high-speed AGC”. In the following description, the automatic gain control in this state is described as “low speed AGC”. In order to realize high-speed AGC, it is conceivable to use digital RSSI that obtains the received electric field strength by digital processing that responds at high speed, or use AGC that performs control according to the voltage detected by the analog circuit only by analog processing. ing.

  In Patent Document 1, a high-speed power calculation circuit that calculates power of an input signal in a short cycle, a normal power calculation circuit that calculates power in a normal cycle, and a power calculation result of the high-speed power calculation circuit or the normal power calculation circuit are input. A receiving device that switches between a high-speed power calculation circuit and a normal power calculation circuit according to a value of a difference between a power calculation result of the high-speed power calculation circuit and a predetermined target reception power by a circuit that calculates a feedback amplifier is disclosed. Yes.

  In Patent Document 2, as a detection method at the time of reception signal level rise where high-speed AGC needs to be performed, an instantaneous value of an RSSI signal and a difference signal of a long section are compared with a threshold value, and reception is performed when the difference signal exceeds the threshold value. It is determined that the signal level has risen, and AGC control is pulled in at high speed. The rising edge of the received signal is detected by a digital RSSI value obtained by digital processing.

JP 2002-135346 A

JP 2006-197654 A

  For example, when transmission diversity is performed even in phase shift keying such as amplitude modulation, QPSK (Quadrature Phase-Shift Keying), and π / 4 QPSK, linearity of amplitude is required at the time of demodulation. A receiving apparatus that performs intermittent reception and requires linearity of amplitude at the time of demodulation needs to perform high-speed AGC at an initial stage immediately after rising and low-speed AGC in a steady state. However, in order to realize high-speed AGC only by digital processing, high-speed digital processing is indispensable because digital RSSI is calculated in a very short time. This is one of the major problems in a receiving apparatus in which reduction of power consumption is important. Further, in communication with a low symbol rate, an increase in the number of oversamples requires high-speed sampling processing, which also causes an increase in power consumption. The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a receiving apparatus capable of performing automatic gain control at high speed while reducing the load on the CPU and reducing power consumption. .

  A receiving apparatus according to the present invention converts a received analog signal including a data frame transmitted from a base station at a predetermined time interval into a digital signal and demodulates it, and measures a received electric field strength to obtain a digital received electric field strength signal. Output receiver, envelope detection of received analog signal, measurement of received field strength and output of analog received field strength signal, and gain of received analog signal based on external gain control signal In addition, the automatic gain control unit that changes the attenuation factor and the power supply to the receiving unit start a predetermined time before receiving the desired data frame, and the gain is based on the analog received electric field strength signal output from the analog detection unit. When the control signal is generated, the data frame is received, and the received electric field strength is stable, it is output from the receiver. Based on the digital reception electric field intensity signal is provided with a control unit for generating a gain control signal.

  A receiving apparatus according to the present invention converts a received analog signal including a data frame transmitted from a base station at a predetermined time interval into a digital signal and demodulates it, and measures a received electric field strength to obtain a digital received electric field strength signal. Output receiver, envelope detection of received analog signal, measurement of received field strength and output of analog received field strength signal, and gain of received analog signal based on external gain control signal In addition, the automatic gain control unit that changes the attenuation factor and the power supply to the receiving unit start a predetermined time before receiving the desired data frame, and the gain is based on the analog received electric field strength signal output from the analog detection unit. When the control signal is generated, the data frame is received, and the received electric field strength is stable, it is output from the receiver. Since there is provided a control unit for generating a gain control signal based on the digital received signal strength signal, while reducing the load reduction and low power consumption of the CPU, it is possible to perform automatic gain control at a high speed.

It is a block diagram which shows the structure of the receiver which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the receiver which concerns on Embodiment 2 of this invention. It is explanatory drawing which shows the mode of the synchronous mode of intermittent reception.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 1 of the present invention. The configuration of the present invention assumes a digital portable communication device (superheterodyne receiver) in wireless communication, and includes an antenna unit 1, an RF (Radio Frequency) unit 2, a mixer 3 for performing frequency conversion, a local signal generating unit 4, An IF (Intermediate Frequency) unit 5, a demodulation A / D (analog / digital) converter 6, an A / D converter 7 for high-speed RSSI measurement, and a digital processing unit 8. The digital processing unit 8 mainly includes a DEM (DEModulator) 9 that performs demodulation processing and a CPU (Central Processing Unit) 10 that performs radio control such as automatic gain control (AGC). When the required dynamic range of the receiving device is restricted by the dynamic range of the A / D converter 6 in the system, the RF unit 2 performs preamplifier ON / OFF control and ATT (Attenuator) ON / OFF control. Such automatic gain control (AGC) is required.

  The operation in the case of implementing high-speed AGC for tracking the received electric field level in the transition period in the initial stage immediately after the rising will be described. The receiving apparatus according to the present invention operates in the following two modes to reduce power consumption. “Out-of-service mode” is an operation mode of the receiving apparatus when a sufficient electric field is not obtained, and “synchronous mode” indicates an operation mode of the receiving apparatus when a sufficient electric field is obtained. In the “out-of-service mode”, the receiving device repeatedly turns on / off the receiving power at a cycle of several seconds, and after turning on the receiving power, executes high-speed AGC according to the level of analog RSSI. In the “synchronous mode”, the receiving device knows the timing of the frame to be received with respect to the data frame transmitted at a known time interval. Thereafter, high-speed AGC is executed in accordance with the level of analog RSSI.

  An operation in a case where low-speed AGC that stably performs gain control in a steady state even under a fading environment will be described. The steady state indicates a state in which the receiving apparatus is in the synchronous mode described above, the receiving power is turned on, and a frame is received. When the receiving apparatus detects a reception interrupt from the LSI to the CPU after the high-speed AGC is performed (the LSI enters the CPU in units of received frames), the receiving apparatus performs the low-speed AGC.

  FIG. 3 is an explanatory diagram showing a state of the intermittent reception synchronous mode. The target receiving apparatus receives data continuously transmitted from the base station. The data consists of 16 frames each having a frame length of 40 ms, forming a super frame having a length of 640 ms. The base station periodically transmits a super frame. Each frame includes a sync word for establishing synchronization, an error correction code, general-purpose data, and the like. The receiving apparatus receives one or more frames among 0 to 15 frames shown in FIG. FIG. 3 shows a state in which only frame number 1 is received. In this case, it is necessary to receive data indicated by reference numerals 1 to 4 in the figure. Data of code 1 indicates reception for high-speed AGC, code 2 indicates a preamble, code 3 indicates a frame to be received, and code 4 indicates a preamble. The receiving apparatus performs high-speed AGC in the section denoted by reference numeral 1, and the CPU 10 generates an automatic gain control signal using analog RSSI obtained by envelope detection by analog processing, and outputs it to the RF unit 2 to automatically Gain control is performed. Then, in the section of reference numeral 2, an automatic gain control signal is generated using an average RSSI value and a peak RSSI value that can be detected by digital processing of the DEM unit 9, and is output to the RF unit 2 to perform automatic gain control. The CPU 10 receives a reception interrupt signal from the DEM 9 when transitioning from the reference numeral 1 to the reference numeral 2. In response to this reception interrupt signal, the CPU 10 transitions from high-speed AGC to low-speed AGC.

  In high-speed AGC, it is common to use a single detection IC to perform analog envelope detection, but it is also possible to configure a detection circuit using a diode. On the other hand, in low speed AGC, automatic gain control using digital RSSI (average power, peak power) obtained by digital processing is performed. That is, average power and maximum power averaged in frame units are calculated from the amplitudes of the I and Q signals that are baseband signals, and each obtained power is converted into decibel units using a conversion table. The detection of the analog RSSI used for the high-speed AGC depends only on the propagation delay by the RF unit 2, enables automatic gain control on the order of μsec, and complete control in units of bursts.

  On the other hand, the digital RSSI used for the low-speed AGC may be detected by digital processing in units of frames. By reducing the access frequency between the DEM unit 9 and the CPU 10, the load on the CPU 10 and the power consumption can be reduced. The feature is that it can.

  As described above, the receiving apparatus according to the present invention is an automatic processor that uses analog RSSI obtained by envelope detection by analog processing in high-speed AGC that follows a transient received electric field level in an initial stage immediately after rising. In low-speed AGC that performs gain control and stably performs gain control in a steady state even under a fading environment, automatic gain control using digital RSSI (average power, peak power) obtained by digital processing is performed.

  Therefore, according to the present invention, in wireless communication that performs intermittent reception, it is possible to realize a high-speed AGC that can follow at a high speed on the order of μsec immediately after the start-up, regardless of the bit rate of communication, and reduce digital processing. Is possible. In a steady state, by performing low-speed AGC using digital RSSI (average power, peak power), it is possible to realize stable wireless communication even in a portable device that performs intermittent reception. Also, automatic gain control according to received power can be performed independently for each burst. Automatic gain control can be performed at high speed while reducing CPU load reduction and low power consumption.

  Although the above description has been given of a superheterodyne receiver, it can also be applied to a double superheterodyne receiver.

Embodiment 2. FIG.
FIG. 2 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 2 of the present invention. The configuration of the present invention assumes a digital portable device (superheterodyne receiver) in wireless communication. In FIG. 2, the components include an antenna unit 1, an RF (Radio Frequency) unit 2, a mixer 3 that performs frequency conversion, a local signal generation unit 4, an IF (Intermediate Frequency) unit 5, and an A / D (analog) for demodulation. / Digital) converter 6, high-speed RSSI A / D (analog / digital) converter 7, and digital processing unit 8. The digital processing unit 8 mainly includes a DEM (DEModulator) 9 that performs demodulation processing and a CPU (Central Processing Unit) 10 that performs radio control such as automatic gain control (AGC).

  When the required dynamic range of the receiving apparatus is restricted by the dynamic range due to the bit width in digital processing, automatic gain control (AGC) by bit optimization that performs bit shift is required. In automatic gain control (AGC), gain control is normally performed based on an RSSI value detected within the receiving apparatus. In the present invention, the CPU 10 optimizes the bit of the DEM unit 9 using the analog RSSI obtained by the envelope detection by the analog processing of the IF unit 5 and the average RSSI value and the peak RSSI value detectable by the digital processing of the DEM unit 9. To realize digital automatic gain control (AGC). At this time, in high-speed AGC that follows the transient received electric field level in the initial stage immediately after the rising, automatic gain control using analog RSSI obtained by envelope detection by analog processing is performed, and in a steady state under fading environment However, in low-speed AGC that stably performs gain control, automatic gain control using digital RSSI (average power, peak power) obtained by digital processing is performed.

  The detection of the analog RSSI used for the high-speed AGC enables automatic gain control on the order of μsec only by the propagation delay by the RF unit 2, and complete control can be performed in burst units. On the other hand, the digital RSSI used for the low-speed AGC may be detected by digital processing in units of frames. By reducing the access frequency between the DEM unit 9 and the CPU 10, the load on the CPU 10 and the power consumption can be reduced. Is a feature.

  In the first embodiment, the reception device uses the analog RSSI obtained by envelope detection by analog processing of the IF unit 5 and the average RSSI value and the peak RSSI value that can be detected by digital processing of the DEM unit 9, and the CPU 10 performs RF Although the gain control of the unit 2 is performed, in the second embodiment, the analog RSSI obtained by the envelope detection by the analog processing of the IF unit 5, the average RSSI value and the peak RSSI that can be detected by the digital processing of the DEM unit 9 The CPU 10 performs gain control by performing bit optimization of the DEM unit 9 using the values. Both of them can realize stable wireless communication even in wireless communication that performs intermittent reception, and have an effect that automatic gain control according to received power can be performed independently for each burst.

1: antenna unit, 2: RF unit, 3: mixer, 4: local signal generation unit, 5: IF unit,
6: A / D (analog / digital) converter (for demodulation),
7: A / D (analog / digital) converter (for high-speed RSSI),
8: Digital processing unit, 9: DEM unit, 10: CPU

Claims (2)

A receiving unit that converts a received analog signal including a data frame transmitted from a base station at a predetermined time interval into a digital signal and demodulates it, measures a received electric field strength, and outputs a digital received electric field strength signal;
Envelope detection of the received analog signal, an analog detector for measuring the received electric field strength and outputting an analog received electric field strength signal;
An automatic gain control unit that changes the amplification factor or attenuation factor of the received analog signal based on an external gain control signal;
The power supply to the receiving unit is started a predetermined time before receiving a desired data frame, and the gain control signal is generated based on the analog received electric field strength signal output from the analog detecting unit, and the data frame And a control unit that generates the gain control signal based on the digital reception field strength signal output from the reception unit when the reception field strength is stable. A receiving device. A receiving unit that converts a received analog signal including a data frame transmitted from a base station at a predetermined time interval into a digital signal and demodulates it, measures a received electric field strength, and outputs a digital received electric field strength signal;
Envelope detection of the received analog signal, an analog detector for measuring the received electric field strength and outputting an analog received electric field strength signal;
The power supply to the receiving unit is started a predetermined time before receiving a desired data frame, and the gain control signal is generated based on the analog received electric field strength signal output from the analog detecting unit, and the data frame And the gain control signal is generated based on the digital received field strength signal output from the receiver when the received field strength is stable and With
The receiving device corrects a bit string of a previous digital signal according to the gain control signal output from the control unit.

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