JP5985931B2 - Receiving apparatus and control method thereof - Google Patents

Description

  The present invention relates to a receiving apparatus including an AGC amplifier that controls an amplitude of a received signal to approach a target amplitude, and a control method thereof.

  A receiving device, for example, a receiving device in a mobile radio communication terminal such as a PHS (Personal Handy-phone System) or a mobile phone is provided with an AGC (Automatic Gain Control) amplifier in an intermediate frequency amplification circuit of a received signal (for example, Patent Document 1). The AGC amplifier amplifies the received signal with a gain (amplification factor) such that the received signal approaches the target amplitude. The target amplitude is set in order to suitably AD convert the synchronization preamble signal in the received signal. In mobile communication, the reception power on the reception side fluctuates due to movement of the transmission side or the reception side device, and so-called fading (amplitude of received signal amplitude) may occur. In such a case, the AGC amplifier increases the gain when the amplitude of the received signal is smaller than the target amplitude, and decreases the gain when the amplitude is larger than the target amplitude, thereby obtaining a preamble signal having the target amplitude.

  However, in the PHS frame format, for example, a preamble signal modulated by a QPSK (Quadrature Phase Shift Keying) method is followed by a 16 QAM (16-Quadrature Amplitude Modulation) method or the like. The transmitted data signal is transmitted. Then, when the data signal is amplified with the gain obtained by amplifying the preamble signal, if the maximum amplitude of the data signal is not sufficiently large, the amplitude of the data signal is saturated within the amplitude range in which AD conversion is possible, and information on the amplitude component May be lost. Then, the signal at the time of AD conversion is distorted and the reception characteristics are deteriorated.

  Therefore, conventionally, for example, a method has been proposed in which the amplitude of the data signal is not saturated by setting the target amplitude smaller by a certain margin from the maximum amplitude of the data signal.

Japanese Patent Laid-Open No. 11-312938

  However, even if the target amplitude is set to be smaller than the margin, when the fading speed is high, that is, when the time change rate of the amplitude of the received signal is large, the change rate of the control amount also becomes large. When the amplitude changes suddenly in the reverse direction, control is diverged. Then, there is a problem that the gain control cannot follow the amplitude fluctuation of the received signal and it is difficult to converge the output of the AGC amplifier to the target amplitude. However, if the target amplitude is further reduced and the control amount required for the convergence of the output of the AGC amplifier is reduced to facilitate the control, the signal component is easily buried in the floor noise, and the received signal is AD converted. There is a problem that the signal resolution (resolution) at the time is generally lowered.

  Accordingly, an object of the present invention made in view of the above problems is to provide a receiving apparatus capable of easily converging the output of the AGC amplifier to a target amplitude even when the fading speed is high, and a control method thereof. There is to do.

In order to solve the above-described problem, a receiving apparatus according to one aspect of the present invention includes an AGC amplifier that amplifies the amplitude of an input received signal with a gain that approaches a target amplitude, and a fading speed obtained from the data of the received signal. the calculated, and a control unit that sets the target amplitude in accordance with the fading speed obtained, the control unit sets the first target amplitude at the first fading rate, the first A second target amplitude smaller than the first target amplitude is set at a second fading speed faster than the first fading speed .

The control unit sets a predetermined target amplitude when the determined fading speed is equal to or lower than a reference speed, and sets a target amplitude smaller than the predetermined target amplitude when the determined fading speed exceeds the reference speed . It is characterized by that.

The receiving apparatus according to the above aspect includes a memory in which a data table in which target amplitudes corresponding to the fading speeds are predetermined is stored, and the control unit sets the fading speed to the calculated fading speed based on the data table. A corresponding target amplitude is set .

  As described above, the solution of the present invention has been described as an apparatus. However, the present invention can be realized as a method, a program, and a storage medium storing the program, which are substantially equivalent thereto, and the scope of the present invention. It should be understood that these are also included. Note that each step of the method or program uses an arithmetic processing unit such as a CPU or a DSP as necessary in data processing, and the input data, processed / generated data, etc. are stored in an HDD, memory, etc. Is stored in the storage device.

For example, a control method for a receiving apparatus that implements the present invention as a method includes a step of amplifying the received signal by an AGC amplifier with a gain such that the amplitude of the input received signal approaches a target amplitude, and data of the received signal And determining the fading speed obtained from the step , setting the target amplitude according to the determined fading speed, and setting the first target amplitude at the first fading speed, from the first fading speed And a control step of setting a second target amplitude smaller than the first target amplitude at a high second fading speed .

  According to the embodiments described below, the output of the AGC amplifier can be easily converged to a suitable target amplitude even when the fading speed is high.

It is a block diagram of the receiver in this embodiment. It is a figure which shows the relationship between the amplitude of a received signal, and target amplitude. It is a figure for demonstrating the change of a target amplitude. It is a figure explaining the relationship between a fading speed and a target amplitude. It is a flowchart figure which shows the setting procedure of the target amplitude by a receiver.

  Embodiments of the present invention will be described below.

  FIG. 1 is a block diagram of a receiving apparatus according to this embodiment. This receiving apparatus is provided in a mobile communication terminal such as a PHS or a mobile phone, or in a base station that communicates with the mobile communication terminal. The receiving apparatus 10 includes an antenna 12, an RF (Radio Frequency) unit 14, an AGC amplifier 16, an AGC control unit 18, an A / D converter 20, a quadrature detection unit 22, a fading speed detection unit 23, and a demodulation unit 24.

  The antenna 12 receives a radio signal and outputs the received radio signal to the RF unit 14.

  The RF unit 14 includes a low noise amplifier, a frequency converter, a band pass filter, a received power detection unit, and the like. The RF unit 14 amplifies a radio signal input from the antenna 12 with a low noise amplifier, and further outputs a signal down-converted to an intermediate frequency signal to the AGC amplifier 16 as a reception signal. Further, the RF unit 14 detects the power of the radio signal input from the antenna 12 by the reception power detection unit, and outputs the detected power value to the AGC control unit 18 as a reception power value (amplitude of the reception signal).

  The AGC amplifier 16 amplifies the received signal with a gain such that the amplitude of the received signal input from the RF unit 14 approaches the target amplitude. Then, the AGC amplifier 16 outputs the amplified received signal to the A / D converter 20. Specifically, the synchronization preamble signal included in the received signal is amplified and output with a gain that approaches a predetermined target amplitude. Then, the data signal following the preamble signal is amplified with the same gain as the preamble signal and output.

  The A / D converter 20 converts the analog reception signal input from the AGC amplifier 16 into a digital signal, and outputs the digital signal to the quadrature detection unit 22.

  The quadrature detection unit 22 performs quadrature detection on the data signal following the synchronization preamble signal included in the digital signal input from the A / D converter 20, and separates the I signal (in-phase signal) and Q signal (quadrature). Signal) is output to the demodulator 24 and the fading speed detector 23.

  The demodulator 24 determines the level of the I signal and Q signal input from the quadrature detector 22 and restores the serial data based on the determination result. The restored serial data is output to a subsequent circuit (not shown) as demodulated data.

  On the other hand, the fading speed detector 23 calculates the modulation accuracy (for example, EVM: Error Vector Magnitude) of the IQ signal. Fading occurs when the mobile communication terminal of the communication partner moves and the amplitude of the received signal received by the receiving device 10 increases or decreases. Here, the time change rate of the modulation accuracy of the IQ signal indicates the fading speed. The fading speed detector 23 calculates a time change rate of the modulation accuracy and outputs data indicating the calculation result to the AGC controller 18. Here, the data indicating the time change rate of the modulation accuracy corresponds to “data indicating the fading speed” in the present embodiment. The fading speed detection unit 23 is, for example, a DSP (Digital Signal Processor) or a microcomputer including a memory that stores a control program and a processor that executes the control program.

  The AGC control unit 18 receives a reception signal from the RF unit 14, and receives data indicating a time change rate of modulation accuracy from the fading speed detection unit 23. The AGC control unit 18 sets the target amplitude of the AGC amplifier 16 according to data indicating the time change rate of the modulation accuracy, that is, data indicating the fading speed. Then, the AGC control unit 18 sets a gain such that the received signal approaches the target amplitude for each target amplitude in the AGC amplifier 16. For example, the AGC control unit 18 has table data TBL in which a gain is associated with the amplitude of the received signal for each target amplitude. The AGC control unit 18 is, for example, a DSP (Digital Signal Processor) or a microcomputer that includes a memory that stores table data TBL and a control program, and a processor that executes the control program. Here, the control operation of the AGC control unit 18 will be described with reference to FIGS.

  FIG. 2 is a diagram showing the amplitude of the received signal for each fading speed. 2A and 2B, the horizontal axis indicates the elapsed time, and the vertical axis indicates the amplitude of the received signal. FIG. 2A shows a change 210 in the amplitude of the received signal with respect to the elapsed time when the fading speed is relatively low. FIG. 2B shows a change 220 in the amplitude of the received signal with respect to the elapsed time when the fading speed is relatively fast.

  As shown in FIGS. 2A and 2B, the amount of change in amplitude per unit time is greater when the fading speed is faster than when the fading speed is slower. In other words, the amplitude change 220 of the received signal has a shorter period than the amplitude change 210.

  When the fading speed is low, as shown in FIG. 2A, the AGC amplifier 16 controls the amplitude of the received signal to approach the target amplitude A21, so that the amplitude of the received signal does not exceed the saturation level A2. It converges to the target amplitude A21. For example, when the amplitude of the received signal exceeds the target amplitude A21, the AGC amplifier 16 decreases the gain and decreases the amplitude of the received signal. On the other hand, when the amplitude of the received signal falls below the target amplitude A21, the AGC amplifier 16 increases the gain and increases the amplitude of the received signal. Such control is repeated, and the amplitude of the received signal converges to the target amplitude A21.

  However, if the fading speed is high, the control may not follow the change in amplitude even if the control is performed so as to approach the target amplitude A21. For example, as shown in FIG. 2B, when the amplitude of the received signal exceeds the target amplitude A21, even if the AGC amplifier 16 decreases the gain to reduce the amplitude of the received signal to the target amplitude A21. The control does not follow the amplitude change 220 of the received signal, and the amplitude of the received signal may exceed the saturation level A2 (240). Then, it leads to deterioration of reception characteristics.

  Therefore, in the present embodiment, the AGC control unit 18 changes the target amplitude of the AGC amplifier 16 according to the fading speed.

  FIG. 3 is a diagram for explaining the change of the target amplitude. 3A and 3B, the horizontal axis represents elapsed time, and the vertical axis represents received signal amplitude. 3A and 3B correspond to the cases of FIGS. 2A and 2B, that is, the case where the fading speed is relatively slow and the case where it is relatively fast, respectively. 3A and 3B show changes 31 and 32 in the amplitude of the received signal in each case.

  As shown in FIGS. 3A and 3B, the AGC control unit 18 sets the target amplitude to A31 when the fading speed is slow, and sets the target amplitude to A32 smaller than A31 when the fading speed is fast. . When the fading speed is slow, even if the target amplitude is set to a larger value (A31), the control can follow the change 31 of the amplitude of the received signal, and amplification can be performed without the amplitude exceeding the saturation level A2. Further, the received power can be increased, and the signal resolution after A / D conversion is improved. On the other hand, when the fading speed is high, the target amplitude is set to a smaller value (A32), so that the amplitude does not exceed the saturation level A2 even if control follow-up is delayed with respect to the amplitude change 32 of the received signal. Can be amplified. Therefore, it is possible to prevent deterioration of reception characteristics.

  FIG. 4 is a diagram for explaining the relationship between the fading speed and the target amplitude. In FIG. 4, the horizontal axis indicates the fading speed, and the vertical axis indicates the degree of influence of the fading speed on the reception characteristics and the target amplitude. Specifically, the influence level indicates the possibility that the amplitude of the received signal is saturated, and the reception characteristics deteriorate as the influence level increases. Here, the degree of influence 42 on the fading speed increases as the fading speed increases. That is, as the fading speed increases, the possibility that the control of the AGC 16 cannot follow and the amplitude of the received signal is saturated increases. Therefore, in the present embodiment, the target amplitude 44 is set relatively large when the fading speed is relatively slow, and the target amplitude 44 is set relatively small when the fading speed is relatively fast. By doing so, the reception power can be amplified to a suitable level while avoiding saturation of the reception signal.

  For the target amplitude, for example, the reference speed Th is set in advance based on experiments and simulations, and when the fading speed exceeds the reference speed Th, the target amplitude A32 shown in FIG. When the speed is equal to or less than Th, the target amplitude can be set by switching to the target amplitude A31 shown in FIG. Alternatively, a plurality of reference speeds may be provided, and the target amplitude may be switched stepwise. For example, a reference speed Th and Th ′ (not shown) larger than Th are set, and when the fading speed is equal to or less than Th, the first target amplitude is set. When the fading speed is greater than Th and equal to or less than Th ′, the first target amplitude is set. It is possible to perform switching such as a small second target amplitude and a third target amplitude smaller than the second target amplitude when larger than Th ′. For example, the AGC control unit 18 stores map data in which a reference speed and a target amplitude are associated with each other in advance in an internal memory. Then, the data is read from the memory by the processor, and the corresponding target amplitude is determined based on the comparison between the fading speed and the reference speed. Then, for each determined target amplitude, a data table in which the amplitude and gain of the received signal are associated is switched, and a gain corresponding to the received signal is determined and set in the AGC amplifier 16.

  FIG. 4 shows an example in which the fading speed, its degree of influence 42, and the target amplitude 44 for each fading speed are indicated by straight lines, and Th is set at the intersection. However, the fading speed and its influence do not necessarily change linearly. Further, since the target amplitude 44 is switched stepwise as described above, FIG. 4 should be understood as an example conceptually showing that a smaller target amplitude is set as the fading speed becomes faster.

  FIG. 5 is a flowchart showing a target amplitude setting procedure of the receiving apparatus 10 according to the present embodiment. This procedure is executed by the AGC control unit 18 periodically with a period of, for example, several microseconds to several tens of microseconds.

  When the reception signal is input from the RF unit 14 (S500), the AGC control unit 18 determines whether the fading speed is faster than the reference speed based on the data indicating the fading speed input from the fading speed detection unit 23. Judgment is made (S501). Here, the process when the reference speed is one (for example, Th shown in FIG. 4) is shown.

  When the fading speed is faster than the reference speed (Yes in S501), the AGC control unit 18 sets a small target amplitude (S502). On the other hand, when the fading speed is equal to or lower than the reference speed (No in S501), the AGC control unit 18 sets a large target amplitude (S504).

  The AGC control unit 18 repeats the above processing until the input of the received signal is completed (No in S506), and when the input of the received signal is completed (Yes in S506), this control cycle ends.

  Then, after the control cycle of FIG. 5, the AGC control unit 18 uses the table data TBL corresponding to the target amplitude to determine a gain that brings the received signal close to the target amplitude and sets the gain in the AGC amplifier 16.

  As described above, according to the receiving apparatus and the control method thereof in the present embodiment, even when the fading speed is high, the output of the AGC amplifier can be easily converged to the target amplitude, and a suitable receiving characteristic can be obtained. it can.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each means, each step, etc. can be rearranged so that there is no logical contradiction, and a plurality of means, steps, etc. can be combined or divided into one. .

10 Receiver
12 Antenna
14 RF section
16 AGC amplifier 18 AGC controller
20 A / D converter
22 Quadrature detector,
23 Fading speed detector
24 Demodulator

Claims (4)

An AGC amplifier that amplifies the amplitude of the input received signal with a gain that approaches the target amplitude;
A fading speed obtained from the data of the received signal, and a controller configured to set the target amplitude according to the obtained fading speed ,
The control unit sets a first target amplitude at a first fading speed, and a second target smaller than the first target amplitude at a second fading speed faster than the first fading speed. Set the amplitude ,
Receiver device. In claim 1,
The control unit sets a predetermined target amplitude when the determined fading speed is equal to or lower than a reference speed, and sets a target amplitude smaller than the predetermined target amplitude when the determined fading speed exceeds the reference speed .
Receiver device. In claim 1,
A memory storing a data table in which a target amplitude corresponding to each of the fading speeds is predetermined;
The control unit sets a target amplitude corresponding to the obtained fading speed based on the data table .
Receiver device. Amplifying the received signal with an AGC amplifier with a gain such that the amplitude of the input received signal approaches the target amplitude;
Obtaining a fading speed obtained from the data of the received signal, and setting the target amplitude according to the obtained fading speed ;
Control for setting a first target amplitude at a first fading speed and setting a second target amplitude smaller than the first target amplitude at a second fading speed faster than the first fading speed Process,
A control method for a receiving apparatus.

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