JP2009089061A - Receiver and frequency hopping synchronization method - Google Patents

Abstract

A receiver and a synchronization method for performing frequency hopping synchronization and AGC control at high speed are provided.
When receiving an OFDM symbol transmitted by a frequency hopping method from a plurality of frequency bands, the OFDM symbol is fixed to one frequency band and the gain of an AGC amplifier is set to a predetermined value to wait for reception of the OFDM symbol. A synchronization detector that outputs a synchronization timing signal at a timing at which the correlation between the frequency hopping synchronization information of the received OFDM symbol and the known frequency hopping synchronization information is maximized on the output side of the A / D converter, and an AGC amplifier Before receiving the gain adjustment completion notification of each, a hopping control unit that generates a reception frequency switching timing signal based on the synchronization timing signal output from the synchronization detection unit and switches the reception frequency to the frequency of each frequency band, and Based on the power value of OFDM symbol received from frequency band It includes a power calculation unit for adjusting the gain of the GC amplifier.
[Selection] Figure 1

Description

  The present invention relates to a frequency hopping wireless transmission system that transmits OFDM symbols using a plurality of frequency bands by switching frequencies, and more particularly, configured to receive OFDM symbols after being synchronized with the frequency hopping timing. And a frequency hopping synchronization method thereof.

  Conventionally, OFDM (Orthogonal Frequency Division Multiplexing) is known as a transmission signal modulation method in a wireless transmission system. The OFDM modulation scheme is a type of multicarrier scheme, and is a type in which data is divided into a plurality of orthogonal subcarriers on the frequency axis and multiplexed to be transmitted. Among these, the OFDM modulation method called MultiBand-OFDM (abbreviated as MB-OFDM) modulation method, which is being standardized for WPAN (Wireless Personal Network) use, divides the bandwidth of 528 MHz into three frequency bands, and 3 transmission signals. This is a system (so-called frequency hopping system) in which transmission is performed by selectively placing each OFDM symbol in one of the frequency bands.

  In the above-described frequency hopping wireless transmission system, the transmitter packetizes the digital data sequence by adding preamble data or the like, performs PSK modulation or ASK modulation as the primary modulation, and outputs the I component and Q component of this output. Based on this, IFFT (Inverse Fast Fourier Transform) is performed as secondary modulation, the time waveform signal of this output is up-converted to a high-frequency signal, and the high-frequency signal is transmitted from the antenna.

  On the other hand, the receiver receives a high-frequency signal with an antenna, amplifies the high-frequency signal with a low-noise amplifier (LNA), town-converts the amplified signal into a low-frequency signal with a mixer (MIX), and passes through a low-pass filter to a reception frequency band. OFDM symbols are extracted, amplified by an AGC (Automatic Gain Control) amplifier, A / D converted, and a digital data sequence is demodulated by a digital signal processing unit.

  In the packet system, a preamble signal indicating a signal pattern or the like is added to the head of data on the transmitter side. This preamble signal is transmitted one after another at different frequencies in the transmitter as a plurality of repeated OFDM symbols. Therefore, the receiver can perform initial processing such as AGC control and hopping timing synchronization within the signal section of the preamble signal.

In the receiver of the known literature, the reception frequency is switched as follows so that the OFDM symbol of each arriving frequency band can be received. That is, first, the reception frequency is fixed to band 1 and the arrival of an OFDM symbol is awaited. When the band 1 OFDM symbol is received, the signal power of the input signal for a certain period is measured, and the gain level of the AGC amplifier is adjusted so that the power of the OFDM symbol within the appropriate power range with respect to the A / D input . Further, synchronization timing information is detected by passing the synchronization pattern information included in the preamble signal of the OFDM symbol through a correlator to obtain cross-correlation with known synchronization pattern information. A control signal for a switch for switching the reception frequency is generated from the synchronization timing thus obtained, and the reception frequency is switched at the synchronization timing. And AGC control using the OFDM symbol of each received band (band 1, band 2, band 3) is performed. (For example, refer to JP 2007-19985 A).
JP 2007-19985 A

  In the packet system, it is generally necessary to finish the frequency hopping synchronization and AGC control within the signal section of the preamble signal arranged at the head of the received packet. In the case of the above-described MB-OFDM system, the signal interval is 18 OFDM symbols in which a preamble signal is inserted.

  However, when frequency hopping synchronization and AGC control according to the conventional method are performed in such a case, AGC control is performed using only the OFDM signal of one frequency band among the 18 OFDM symbols into which the preamble signal is inserted. become. Therefore, since it is not possible to use OFDM signals in other frequency bands, there is a problem that AGC control takes time.

  In addition, after frequency hopping synchronization is established, AGC control is performed for all frequency bands using the signal sections of all 18 OFDM symbols, and fine adjustment with the timing of frequency hopping is performed during that time. Therefore, when fine adjustment is performed in a state where the power of the OFDM symbol is not fixed, there is a problem that an error from the timing of frequency hopping increases.

  Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a receiver that performs frequency hopping synchronization and AGC control at high speed, and a frequency hopping synchronization method thereof.

In order to solve the above problems, the present invention is configured as follows.
One of the aspects of the receiver of the present invention is that when receiving an OFDM symbol transmitted by frequency hopping from a plurality of frequency bands, the reception frequency is fixed to one of the plurality of frequency bands. In addition, the gain of an AGC amplifier connected to the input side of the A / D converter is set to a predetermined value and the reception of the OFDM symbol is awaited, and the reception is performed on the output side of the A / D converter. Before receiving a notification of completion of adjustment of the gain of the AGC amplifier, a synchronization detector that outputs a synchronization timing signal at a timing at which the correlation between the frequency hopping synchronization information of the OFDM symbol and the known frequency hopping synchronization information is maximized, A reception frequency switching timing signal is generated based on the synchronization timing signal output from the synchronization detection unit. A hopping control unit that switches the reception frequency to a frequency of each frequency band; and a power calculation unit that adjusts the gain of the AGC amplifier based on the power value of the OFDM symbol received from each frequency band. .

With this configuration, the switching of the reception frequency can be roughly adjusted to the frequency hopping timing of the OFDM symbol. Since the OFDM signal can be received from each frequency band after the coarse adjustment, the gain of the AGC amplifier using the OFDM signal in each frequency band can be determined early.
The synchronization detection unit further outputs a correlation peak value between the frequency hopping synchronization information and the known frequency hopping synchronization information, and the hopping control unit receives a notification of completion of gain adjustment of the AGC amplifier, Finely adjust the switching timing to the frequency hopping timing of the OFDM symbol so that the difference between the correlation peak values before and after the correlation peak value output from the synchronization detection unit approaches 0 while shifting the switching timing. It is preferable to configure.

Alternatively, the hopping control unit accumulates information indicating a correlation between the frequency hopping synchronization information of the received OFDM symbol and the known frequency hopping synchronization information at a symbol interval upon receiving a notice of completion of gain adjustment of the AGC amplifier. Then, after the accumulated information level exceeds the threshold, the switching timing is finely adjusted to the frequency hopping timing of the OFDM symbol by switching the reception frequency to the frequency of each frequency band at the timing when the threshold is exceeded. It is preferable to configure as described above.

  With the configuration as described above, it is possible to finely adjust the switching of the reception frequency to the frequency hopping timing of the OFDM symbol after determining the gain of the AGC amplifier.

  One aspect of the frequency hopping synchronization method of the present invention is a frequency hopping with an OFDM symbol transmitted in a plurality of frequency bands by a frequency hopping method in a receiver having an AGC amplifier connected to the input side of an A / D converter. The OFDM signal is received from one frequency band of the plurality of frequencies by fixing the reception frequency, and the reception is performed based on the received OFDM symbol of the one frequency band. The frequency is switched to the frequency of each frequency band in a predetermined order (coarse adjustment processing), OFDM symbols are received from each frequency band, and the gain of the AGC amplifier is adjusted based on the power value of the OFDM symbol received from each frequency band. And switch the reception frequency after adjusting the gain. The timing based on OFDM symbols received from the respective frequency bands to fine tune the timing of frequency hopping of the OFDM symbol (fine adjustment process), so as to.

According to the present invention, the number of symbols that can be used for AGC control can be increased, and the AGC control time can be shortened.
Further, since fine adjustment of frequency hopping synchronization is performed after AGC control is determined, synchronization with frequency hopping timing can be established in this fine adjustment section so as to reduce the error.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram of a receiver according to an embodiment of the present invention.

  The receiver shown in FIG. 1 includes an antenna 1, a low noise amplifier (LNA) 2, a mixer (MIX) 3, a local oscillator 4, a low pass filter (LPF) 5, an automatic gain control amplifier (AGC amplifier) 6, and an A / D conversion. And a digital signal processor (DSP) 8 and the like.

  An antenna 1, a low noise amplifier (LNA) 2, a mixer 3, a local oscillator 4, a low-pass filter (LPF) 5, an automatic gain control amplifier (AGC amplifier) 6, and an A / D converter 7 have a predetermined reception frequency. This is a low-IF type down-conversion circuit that digitally outputs an I component and a Q component of a baseband signal from a high-frequency signal.

The digital signal processing unit 8 is a data demodulation circuit including an FFT operation unit 80 for demodulating data of a received OFDM symbol, a data determination circuit (not shown), and the like.
Here, in particular, the local oscillator 4 of the down-conversion circuit is configured to output local signals having different frequencies by switching. For example, a plurality of multiplying type PLL circuits or frequency dividing type PLL circuits that generate local signals for each frequency band from a single frequency signal of a crystal oscillator are incorporated, and the local signal output of any one circuit is controlled by a control signal. Configure the switch to select. Furthermore, the digital signal processing device 8 includes a synchronization detection unit 81, a hopping control unit 82, and a power calculation unit 83 as shown in FIG. With this configuration, this receiver can receive packet data transmitted by the frequency hopping method.

  In the following, assuming that the signal section of the preamble signal added to the head of the received packet data is 18 OFDM symbols, the operation and reception procedure of each part when receiving packet data transmitted by the frequency hopping method in this receiver Indicates.

  First, as a preparation before reception, the gain level of the ACG amplifier 6 is set to a predetermined value. Preferably, in order to perform the following reception processing even for a low-level signal input, a no-signal input state is set. , The gain level of the ACG amplifier 6 is set to the maximum. In addition, in order to receive the divided data (OFDM symbols) of packet data divided into a plurality of frequency bands in a predetermined order by the frequency hopping method from one frequency band, the reception frequency is set to one of the plurality of frequency bands. Match to the frequency band. The selection of the reception frequency is performed, for example, by connecting the output of the PLL circuit corresponding to the predetermined frequency band to the output of the local oscillator 4 by switching the switch according to the control signal from the hopping control unit 82.

  Thus, only the OFDM symbol corresponding to the fixed reception frequency is down-converted and output from the A / D converter 7, and then packet data is received for each OFDM symbol as follows. .

  First, the OFDM symbol in the preamble signal section output from the A / D converter 7, that is, the OFDM symbol of one frequency band down-converted at the fixed reception frequency at this stage, is input to the synchronization detection unit 81, Synchronization timing from the synchronization detection unit 81 to the hopping synchronization unit 82 is a timing at which the correlation between the known frequency hopping synchronization information of the synchronization detection unit 81 and the frequency hopping synchronization information of the OFDM symbol in the preamble signal section is maximized. Output a signal. When there are a plurality of frequency switching patterns (frequency hopping patterns) of the OFDM signal in the transmitter, a correlator for each pattern is prepared in the synchronization detecting unit 81, and the correlation value among them is maximized. Is selected as the frequency hopping pattern, and the synchronization timing signal is output at the time when the frequency becomes the maximum.

  Next, the hopping control unit 82 generates a frequency hopping timing signal based on the synchronization timing signal. The frequency hopping timing signal is generated at a predetermined time interval or by using a time interval of a frequency hopping pattern received in the past. Subsequently, the hopping control unit 82 sends the frequency hopping timing signal together with the control signal to the local oscillator 4, and controls switching of the local oscillator 4 at the switching timing according to a predetermined or selected frequency hopping pattern, that is, the frequency. Roughly adjust the hopping timing. However, at this time, the input timing of the control signal is adjusted so that the frequency band of the OFDM signal input to the mixer 3 corresponds to the local oscillation frequency selected by the switch. As a result, the OFDM symbols of all frequency bands are thereafter down-converted in the order of transmission and output from the A / D converter 7.

Next, the power calculation unit 83 calculates the power value of an OFDM symbol in any frequency band that is continuously output from the A / D converter 7 (also in this case, the OFDM symbol in the preamble signal section). In the power calculation unit 83, an OFDM symbol of one frequency band is input even before the frequency hopping switching timing is roughly adjusted. The power calculation unit 83 compares the signal power after A / D conversion with the electrolytic strength in the AGC amplifier 6 for a certain period including the OFDM symbol and the OFDM symbol of each frequency band after coarse adjustment, and then gain The level adjustment signal is sent to the AGC amplifier 6, and the AGC amplifier 6 is adjusted to a gain level at which the output signal of the A / D converter 7 does not become a saturated signal. When the adjustment of the gain level for the AGC amplifier 6 is completed, the power calculation unit 83 notifies the hopping control unit 82 of an end signal.

  Next, the hopping control unit 82 finely adjusts the coarsely adjusted switching timing to a more accurate timing. This is because the frequency hopping timing signal output from the hopping control unit 82 is shifted, for example, and the switching timing is adjusted so that the correlation value is maximized while monitoring the maximum correlation value output from the synchronization detection unit 81. Do as you do.

The above processing is performed during the preamble signal period, and thereafter, the OFDM symbol data is demodulated through the FFT operation unit 80 or the like according to the setting.
In the above procedure, AGC control can be performed using OFDM symbols of each frequency band. For this reason, the gain of the AGC amplifier 6 can be determined at high speed.

  Further, the frequency hopping switching timing can be adjusted with the gain of the AGC amplifier 6 determined. For this reason, the switching timing can be finely adjusted without increasing the error, and the data can be accurately demodulated.

Next, a configuration example of each unit of the digital signal processing device 8 that receives packet data in the above procedure will be described. However, for ease of explanation, it is assumed here that there is one type of frequency hopping pattern.
(Example 1)
FIG. 2 is a block diagram of the synchronization detection unit 81 according to the first embodiment.

The synchronization detection unit 81 according to the first embodiment includes a correlation calculation unit 800, a preamble pattern storage unit 801, and a maximum value detection unit 802.
The preamble pattern storage unit 801 is a register that stores in advance a data sequence of a frequency hopping pattern included in a preamble signal of packet data.

  Correlation calculation section 800 receives the OFDM symbol data string output from A / D converter 7, calculates the correlation with the data string stored in preamble pattern storage section 801, and calculates the calculation results at each timing. It is configured to continuously output to the maximum value detection unit 802.

  The maximum value detection unit 802 is configured to output a synchronization timing signal (pulse signal) and its maximum value (correlation peak value) when the correlation value output from the correlation calculation unit 800 becomes maximum.

FIG. 3 is a block diagram of the hopping control unit 82 according to the first embodiment.
The hopping control unit 82 according to the first embodiment includes a frequency switching instruction unit 820, a comparator 821, and a 1 symbol delay unit 822.

  Frequency switching instruction unit 820 outputs a synchronization timing signal from maximum value detection unit 802, an AGC end notification signal described later from power calculation unit 83, and an output signal from comparator 821, and a hopping control signal. Output section.

When the frequency switching instruction unit 820 receives a pulse signal as a synchronization timing signal, the frequency switching instruction unit 820 generates a continuous pulse signal at a predetermined time interval based on the pulse signal, generates a frequency hopping timing signal, and outputs it as a hopping control signal. . The switching control of the local oscillator 4 is performed at a predetermined timing at the frequency hopping timing triggered by, for example, outputting a switching instruction signal from the frequency switching instruction unit 820 to another switch through another control line. The frequency is switched in order. When the AGC end notification signal is received, the input is switched to the output side of the comparator 821, and the output timing of the frequency hopping timing signal at that time is advanced or delayed later and output. Further, it repeatedly performs shifting the timing back and forth in a direction in which a later-described difference signal that is an input signal from the comparator 821 approaches 0, and finally the difference signal is set to 0 or substantially 0. By doing so, the frequency switching timing of the local oscillator 4 can be finely adjusted to the exact timing of frequency hopping.

  The correlation peak value of maximum value detection section 802 is input to 1 symbol delay section 822 and comparator 821. The correlation peak value of the 1-symbol delay unit 822 is input to the comparator 821 after being delayed by 1 symbol.

  Comparator 821 gives a frequency switching instruction to the comparison result (difference between before and after correlation peak values) between the correlation peak value input from maximum value detection section 802 and the correlation peak value one symbol before input from one symbol delay section 822. It is configured to output to the unit 820.

FIG. 4 is a block diagram of the power calculation unit 83 in the first embodiment.
The power calculation unit 83 according to the first embodiment includes an integrator 830 and a symbol power determination unit 831.

The symbol power determination unit 831 calculates the power value of the OFDM symbol for a certain period based on the output of the integrator 830 that calculates the integral value of I ² + Q ² from the complex signal of the digital received signal after A / D conversion. When the power value is an appropriate power value for reception as compared with the RSSI (received electrolytic strength signal) calculated by the analog circuit unit of the AGC amplifier 6, an AGC end notification signal is output to the hopping control unit 82, If the value is different from the appropriate value, the gain is adjusted by notifying the AGC amplifier 6 of a gain adjustment amount that falls within the appropriate range.

FIG. 5 is a timing chart of the receiver in the first embodiment.
Here, an example is shown in which packet data is divided into three frequency bands (“band1”, “band2”, “band3”) and transmitted in the order of “band1”, “band2”, “band3”. ing.

In the example shown in the figure, the horizontal axis is assigned to the time axis, and 18 OFDM symbols in the preamble signal section of the packet data are represented as “PS”.
First, this is an example in which the reception frequency of the receiver is fixed to “band1”, so the first “PS” of “band1” is received by the receiver.

  Since this receiver outputs the synchronization timing at the position where the correlation with the preamble pattern of “PS” is the maximum (the position where the correlation output is the maximum in the figure), the frequency hopping timing for each frequency band at this timing Is roughly adjusted. Therefore, as shown in the figure, “PS” of “band2” and “band3” are continuously received after receiving “PS” of “band1”.

  In this receiver, “PS” of these three frequency bands are received continuously in the first place. Therefore, as shown in the figure, AGC control can be completed within this period.

When AGC control is completed using “PS” of these three frequency bands, A /
The output signal of the D converter 7 is output without being saturated. For this reason, since the maximum value of the correlation output converges to a certain value, the frequency switching of the local oscillator 4 can be accurately finely adjusted to the frequency hopping timing within the remaining hopping fine adjustment interval.

As described above, since the AGC control can be performed using the OFDM symbol of each frequency band, the gain of the AGC amplifier 6 can be determined at high speed.
Further, the frequency hopping switching timing can be adjusted with the gain of the AGC amplifier 6 determined. For this reason, it becomes possible to finely adjust the switching timing within the preamble signal interval without increasing the error, and thereafter, the data can be accurately demodulated.
(Example 2)
In the second embodiment, a modification of the synchronization detection unit 81 and the hopping control unit 82 according to the first embodiment will be described.

FIG. 6 is a block diagram of the synchronization detection unit 81 in the second embodiment.
The synchronization detection unit 81 according to the second embodiment includes a correlation calculation unit 815, a preamble pattern storage unit 816, a maximum value detection unit 817, a symbol delay unit 818, and a threshold determination unit 819.

The preamble pattern storage unit 816 is a register that stores in advance a data sequence of a frequency hopping pattern included in a preamble signal of packet data.
The correlation calculation unit 815 receives the OFDM symbol data string output from the A / D converter 7, calculates the correlation with the data string stored in the preamble pattern storage unit 816, and calculates the calculation result at each timing. It is configured to continuously output to a maximum value detection unit 817 and a threshold value determination unit 819.

The maximum value detection unit 817 is configured to output a synchronization timing signal (pulse signal) when the correlation value output from the correlation calculation unit 815 becomes maximum.
The threshold determination unit 819 repeatedly determines whether the output level exceeds a predetermined threshold from the sum of the calculation result of the correlation calculation unit 815 and the cumulative calculation result up to one symbol delayed by the one symbol delay unit 818. When a predetermined threshold is exceeded, a synchronous timing signal (pulse signal) at that timing is output. Here, 1-symbol delay unit 818 is configured to reset data by an AGC end notification signal from power operation unit 83, and threshold determination unit 819 accumulates correlation values for symbols after the end of AGC control. A threshold is determined based on the calculation result.

FIG. 7 is a block diagram of the hopping control unit 82 according to the second embodiment.
The hopping control unit 82 according to the second embodiment includes a frequency switching instruction unit 825.
The frequency switching instruction unit 825 includes an input unit that inputs the synchronization timing signal (coarse adjustment synchronization timing signal) from the maximum value detection unit 817 and the synchronization timing signal (fine adjustment synchronization timing signal) from the threshold determination unit 819, and hopping control. And an output unit for outputting a signal.

  When the frequency switching instruction unit 825 receives the synchronization timing signal (pulse signal) from the maximum value detection unit 817, the frequency switching instruction unit 825 generates a continuous pulse signal at a predetermined time interval based on the pulse signal to generate a frequency hopping timing signal. And output as a hopping control signal. The switching control of the local oscillator 4 is the same as in the first embodiment. Subsequently, when a fine tuning synchronization timing signal (pulse signal) is received from the threshold value determination unit 819, a continuous pulse signal is generated at predetermined time intervals instead of the coarse tuning synchronization timing signal. To generate a frequency hopping timing signal and output it as a hopping control signal.

By doing so, the frequency switching timing of the local oscillator 4 can be finely adjusted to the exact timing of frequency hopping.
FIG. 8 is a timing chart of the receiver in the second embodiment.

  Compared with the timing chart of FIG. 5 of the receiver in the first embodiment, in the receiver of the second embodiment, the fine adjustment of the switching timing immediately after performing the AGC control is finished when the level exceeds the threshold value due to the correlation accumulation. That is, it is possible to finish the process early.

As described above, also in the second embodiment, since the AGC control can be performed using the OFDM symbols of the respective frequency bands, the gain of the AGC amplifier 6 can be determined at high speed.
Further, the frequency hopping switching timing can be adjusted with the gain of the AGC amplifier 6 determined. For this reason, it becomes possible to finely adjust the switching timing within the preamble signal interval without increasing the error, and thereafter, the data can be accurately demodulated.

  Further, fine adjustment of the switching timing can be performed at high speed.

It is a block diagram of the receiver in embodiment of this invention. 6 is a block diagram of a synchronization detection unit 81 in Embodiment 1. FIG. 3 is a block diagram of a hopping control unit 82 in Embodiment 1. FIG. 4 is a block diagram of a power calculation unit 83 in Embodiment 1. FIG. 3 is a timing chart of the receiver in the first embodiment. 6 is a block diagram of a synchronization detection unit 81 in Embodiment 2. FIG. 6 is a block diagram of a hopping control unit 82 in Embodiment 2. FIG. 6 is a timing chart of a receiver in the second embodiment.

Explanation of symbols

1 Antenna 2 Low noise amplifier (LNA)
3 Mixer 4 Local oscillator 5 Low-pass filter (LPF)
6 Automatic gain control amplifier (AGC amplifier)
7 A / D converter 8 Digital signal processor (DSP)
81 synchronization detection unit 82 hopping control unit 83 power calculation unit

Claims (4)

When receiving OFDM symbols transmitted by frequency hopping from multiple frequency bands, the reception frequency is fixed to one of the multiple frequency bands and connected to the input side of the A / D converter A receiver which waits for reception of the OFDM symbol with a predetermined gain of the AGC amplifier,
On the output side of the A / D converter,
A synchronization detector that outputs a synchronization timing signal at a timing at which the correlation between the frequency hopping synchronization information of the received OFDM symbol and the known frequency hopping synchronization information is maximized;
Before receiving a notice of completion of gain adjustment of the AGC amplifier, hopping for generating a reception frequency switching timing signal based on the synchronization timing signal output from the synchronization detector and switching the reception frequency to a frequency of each frequency band A control unit;
A power calculator that adjusts the gain of the AGC amplifier based on the power value of the OFDM symbol received from each frequency band;
Receiver with. The synchronization detection unit further outputs a correlation peak value between the frequency hopping synchronization information and the known frequency hopping synchronization information,
When the hopping control unit receives a notice of completion of gain adjustment of the AGC amplifier, the difference between the correlation peak values before and after the correlation peak value output from the synchronization detection unit is made close to 0 while shifting the switching timing. Finely adjusting the switching timing to the frequency hopping timing of the OFDM symbol,
The receiver according to claim 1. The hopping control unit, upon receiving a notice of completion of gain adjustment of the AGC amplifier, accumulates information indicating the correlation between the frequency hopping synchronization information of the received OFDM symbol and the known frequency hopping synchronization information at a symbol interval, Finely adjusting the switching timing to the frequency hopping timing of the OFDM symbol by switching the reception frequency to the frequency of each frequency band when the accumulated information level exceeds the threshold,
The receiver according to claim 1. In a receiver in which an AGC amplifier is connected to the input side of an A / D converter, a method of synchronizing frequency hopping timing with OFDM symbols transmitted to a plurality of frequency bands by a frequency hopping method,
Receiving an OFDM symbol from one frequency band of the plurality of frequencies by fixing a reception frequency;
Based on the received OFDM symbol of the one frequency band, the received frequency is switched to the frequency of each frequency band in a predetermined order,
Receiving an OFDM symbol from each frequency band;
Adjusting the gain of the AGC amplifier based on the power value of the OFDM symbol received from each frequency band;
After finishing the gain adjustment, finely adjust the timing of switching the reception frequency to the frequency hopping timing of the OFDM symbol based on the OFDM symbol received from each frequency band,
And a frequency hopping synchronization method.

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