JP2003229833A - Diversity adapter, ofdm receiver for receiving signal from diversity adapter, and diversity receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diversity circuit 30 which can obtain an information code with little code errors by decoding a code from an RF signal received by the best antenna at the point of that time all the time and does not increase code errors in switching an RF signal to be selected. <P>SOLUTION: This diversity circuit 30 includes a circuit 35 for calculating an FFT common window period being a signal fetching period to an FFT which is common to an OFDM signal included in at least two or more antenna signals among antenna signals inputted from a plurality of antenna signal input terminals and whose inter-symbol interference noise level becomes minimum, outputting the FFT common window period, and a circuit 36 for calculating and outputting an antenna signal switching control signal for switching a plurality of antenna signals within a period other than the FFT common window period or an antenna signal switching symbol signal that represents the symbol position of the OFDM signal at a time for further switching the plurality of antenna signals. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an orthogonal frequency division multiplex modulation system (Ort) for transmitting an information code by a plurality of carriers (carrier waves) orthogonal to each other as a transmission system.
hogonal Frequency Division
(Multiplexing: hereinafter referred to as an OFDM system) A diversity adapter having a diversity circuit for receiving an OFDM signal or the like which is a transmission signal of the OFDM system, and an OFD for inputting a signal from the diversity adapter
The present invention relates to an M receiver and a diversity receiver.

[0002]

2. Description of the Related Art In recent years, in the field of wireless devices, the OFDM system has been the focus of attention as a modulation system that is strong against multipath fading, and is used in next-generation television broadcasting, FPU, wireless LAN, etc. in countries such as Europe and Japan. A lot of applied research is underway in Japan. Among them, the development trend and system of terrestrial digital broadcasting in the UHF band are described in Journal of Image Information Media 1998 Vol. 52, No. See 11 for details.

In the OFDM system, as schematically shown in FIG. 2, a plurality of carriers (carriers), for example, about 1400, which are orthogonal to each other are provided within a certain transmission band width, and a designated carrier is 64 QAM by an information code. This is a method of transmitting after being modulated by a modulation method such as. The time waveform is shown in FIG.
As schematically shown in FIG. 3, there is a guard interval configured by copying a part b of the signal in the effective symbol period Ts to the head part b ′. Due to this signal structure, OF
In the DM method, a strong characteristic in multipath can be obtained.

However, even the OFDM system is not universal and further improvement is desired. Generally, a diversity reception system is used to improve the reception characteristics in a mobile radio environment such as a mobile phone and a car phone under a multiplex radio wave propagation environment and a mobile reception environment, and the application to the OFDM system is also under study.

As the first method, for example, a method of comparing signals of carriers corresponding to each other in OFDM signals received by two antennas, and selecting and decoding a signal of a carrier with higher reliability However, Japanese Patent Laid-Open No. 2001-156
No. 738 is proposed.

However, in this method, it is necessary to demodulate the RF signal received by each antenna almost completely, and a circuit for two receivers is substantially required. Therefore, although the effect is large, there is a drawback that the device is large and expensive.

On the contrary, as a second method having the smallest circuit scale, a method of adding the signals received and amplified by the respective antennas as they are and averaging the signal levels of the respective carriers is proposed in Japanese Patent Laid-Open No. 2000-278243. Has been done.

However, in this method, a large number of waves received by the respective antennas are further added, and as a result, a waveform with a Rayleigh distribution, that is, a waveform in which the level fluctuates drastically, is obtained, so that a very large effect is obtained. Absent.

As a third method having an intermediate circuit scale, a method of selecting and demodulating a signal having the highest level among signals received by a plurality of antennas is disclosed in Japanese Patent Laid-Open No. 11-2052.
No. 90 publication.

This method will be described in more detail below. FIG. 4 is a circuit configuration diagram of a conventional OFDM diversity receiver. The RF signal a, which is the signal received by the antenna 1a, is down-converted to the baseband signal a by the receiving circuit 2a, and then input to the delay circuit 3a and the correlation calculating circuit 4a. The signal delayed by one effective symbol period Ts by the delay circuit 3a is branched into two, one of which is directly input to the OFDM signal selection circuit 5. Also,
The other is input to the correlation calculation circuit 4a.

The correlation calculation circuit 4a is composed of the baseband signal a directly input from the reception circuit 2a and the delay circuit 3a.
It is a circuit for calculating a correlation value between baseband signals a ′ delayed by an effective symbol period. More specifically, the baseband signal a of FIG. 5 (a) directly input from the receiving circuit 2a and FIG. 5 (b) delayed by one effective symbol period.
5 (c) obtained by performing complex multiplication s (t) × s (t−Ts) ^* of signals at the same timing between the baseband signal a ′ of The value Σ {s (t) × s (t−Ts) ^* } added in the range schematically shown in FIG. 5D, which is the period width, is sequentially calculated.
Here, s ^* represents a conjugate complex signal of the complex signal s.

The calculated value is output as a correlation signal from the correlation calculation circuit 4a and input to the OFDM signal selection circuit 5. The waveform of the correlation signal calculated in this way is shown in FIG.
It shows in (e). The waveform of this correlation signal has a peak at the boundary between the effective symbol period of the symbol of interest and the guard interval of the following symbol, and the peak value is the value of the OFDM signal component included in the input RF signal a. It has a characteristic that increases with the level.

RF received by the other antennas 1b and 1c
The same signal processing is performed on the signals b and c, and the baseband signals b ′ and c ′ output from the delay circuits 3b and 3c and the correlation signal b calculated by the correlation calculation circuits 4b and 4c are output. c is also input to the OFDM signal selection circuit 5.

FIG. 6 shows the circuit configuration of the OFDM signal selection circuit 5. The maximum value comparison circuit 6 detects the peak values of the input correlation signals a to c, compares the peak values, and selects and outputs the number of the correlation signal having the maximum peak value. In the selector circuit 7, a baseband signal having the same number as the selected correlation signal number, for example, the baseband signal a ′ when the correlation signal a is selected from the plurality of input baseband signals. And output. The baseband signal selected and output by the OFDM signal selection circuit 5 is demodulated by the OFDM signal demodulation circuit 8 in FIG. 4, and the decoded information code is output.

In the diversity receiver of FIG. 4, OF
The DM demodulation circuit 8 only needs to be provided in one set, and the circuit scale is about half or less as compared with the first method of the diversity receiving apparatus. Further, since the baseband signal calculated from the RF signal received by the antenna that seems to have the highest reception level is selected and demodulated, a large number of waves are added to cancel the effect as in the second method. Of course, a relatively large effect can be obtained. Therefore, it is possible to obtain a diversity receiving device having a well-balanced circuit scale and effect.

[0016]

However, when this diversity receiver is applied to, for example, a microwave band FPU, the following problems occur.

The first problem is that the correlation calculation circuits 4a to 4c.
It is a point that the peak value of the correlation signal calculated in step 1 does not necessarily represent the level of the OFDM signal included in the RF signal received by the antenna. In the case of FPU, the high frequency RF signal received by the antenna is amplified and IF of intermediate frequency is used.
An AGC circuit is incorporated in the circuit unit that down-converts the signal, and the IF signal level converted is controlled to be substantially constant. In other words, the received O
Control is performed so that the level of the added signal obtained by adding the FDM signal and the noise component generated in the RF circuit unit becomes constant.

When the received OFDM signal is only one main wave, if the level of the OFDM signal received by the antenna falls below a level at which the noise level generated in the RF circuit section cannot be ignored, the signal is included in the IF signal. The level of the OFDM signal component that is also reduced. At this time, since the level of the IF signal is kept constant, the level of the noise component increases instead.

On the other hand, the noise component has no correlation with the noise delayed for a certain time, and the average value of the correlation signal of the noise component becomes almost zero. Therefore, the peak value of the correlation signal is IF
It represents the level of the OFDM signal included in the signal. Therefore, by comparing the peak values of the correlation signals, the O received by the antenna is expected, as expected in the conventional example.
The levels of the FDM signals can be compared.

For example, when the OFDM reception level received by the antenna is sufficiently high, a correlation signal having a large peak value can be obtained as indicated by the broken line in FIG. 7 (a). FIG. 7 shows the relationship between the OFDM signal contained in the IF signal and the noise component level at this time.
(B) is schematically shown in the upper and lower rows. On the other hand, as in the case of the correlation signal of the solid line, the peak value is 1/2 of the peak value of the broken line.
When the signal level decreases to 1, it indicates that the level of the OFDM signal included in the IF signal has decreased to half. The power of the OFDM signal level lowered at this time is compensated by the increase of the noise component shown in the lower part of FIG. 7C, and the IF signal level is kept constant. Therefore, C / of the OFDM signal obtained at this time
The N value is about 0 dB, and it can be determined that an OFDM signal of a modulation method having a high multivalued value such as 64QAM cannot be demodulated.

However, if a large delay wave of the same level as the main wave is mixed in the received OFDM signal, the situation changes greatly. The correlation waveform obtained at this time becomes the waveform shown by the solid line in FIG. 8A in which the correlation signal of the main wave and the correlation signal of the delayed wave are added, and the peak value level is the peak value of the correlation signal shown by the broken line. To about 1/2 the level. However, in this case, since the decrease in the level of the main wave is compensated for by the level of the delayed wave shown in the middle part of FIG. 8B, the IF signal is almost free from noise as shown in the lower part of FIG. 8B. Not included. On the other hand, since the OFDM signal has a guard interval, even if a delayed wave is mixed as shown in FIG. 8B, it can be sufficiently decoded if the noise level is low.

A baseband signal a for which the solid line correlation signal of FIG. 7A is obtained and a baseband signal b for which the solid line correlation signal of FIG. 8A is obtained are compared and selected by a conventional method. In this case, if the peak value is high even if only a little, the result is as shown in FIG.
The baseband signal a for which the solid line correlation signal is obtained is selected. However, when the baseband signal is switched according to this selection, the C / N value is almost 0 dB from the baseband signal b which has been decoded without any problem until then.
In this case, the signal is switched to the baseband signal a, which is difficult to decode, which causes a problem that the diversity control malfunctions.

The second problem is that since the timing of switching the baseband signal is set to an arbitrary timing, the signal of one symbol for switching the baseband signal cannot be demodulated at all and a large code error occurs. It is a point.

In the OFDM demodulation circuit 8 of FIG.
As schematically shown in (a), the signal portion of one effective period Ts is extracted from within the same symbol of the input OFDM signal, and FFT is performed to demodulate each carrier signal. At this time, if the baseband signal is switched during the signal period taken in the FFT, a large distortion occurs in the demodulated carrier signal, which causes a problem that the code of this symbol cannot be decoded.

In this case, a method is conceivable in which switching is performed during the period excluding the signal portion to be taken into the FFT, for example, at the head portion of the guard interval indicated by the thick dashed arrow.
In the case of signals, the problem is more complicated. That is, normally
The main wave of the OFDM signal received by the antennas 1a and 1b changes not only in its level but also in the delay time, as shown in FIG. 9 (b). Therefore, for example, when the baseband signal a is selected, if the baseband signal b is simply switched at the beginning of the guard interval, the OFDM signal included in the newly selected baseband signal b is detected. Will extract the signal spanning the adjacent symbol and perform FFT. Therefore, the inter-symbol interference noise increases until the symbol synchronization is pulled into the OFDM signal received by the antenna 1b, which causes a problem that the code error increases for a certain period.

The third problem is that the third method of the diversity receiving apparatus requires only about half the circuit scale as compared with the first method, but a dedicated apparatus for diversity receiving is required, and the user needs it. The point is that expensive expenses are still required.

An object of the present invention is to solve the above-mentioned problem by selecting in consideration of the presence of a delayed wave, and always decode the code from the RF signal received by the best antenna at that time to eliminate the code error. A diversity circuit having a diversity circuit that can obtain a small number of information codes and that does not increase code errors when switching the RF signal to be selected.
An object of the present invention is to provide an OFDM receiving apparatus and a diversity receiving apparatus for inputting signals from an adapter and a diversity adapter.

Another object of the present invention is to provide an FP for normal reception.
If U owns, it is to provide a diversity adapter that enables diversity reception easily.

[0029]

According to the present invention, an OFDM signal, which is an orthogonal frequency division multiplex modulation system transmission signal for transmitting an information code by a plurality of carriers (carrier waves) orthogonal to each other, is received, and OFDM is connected to a subsequent stage. A diversity adapter having a diversity circuit for outputting to a receiving device, wherein the diversity circuit inputs a plurality of antenna signals which are signals received by an antenna, and the plurality of antenna signal input terminals. An FFT common window period, which is a signal acquisition period into an FFT that is common to the OFDM signals included in at least two or more antenna signals among the antenna signals input from the antenna signal input terminal and has the smallest inter-symbol interference noise level, Calculate,
An FFT common window period calculation circuit that outputs an FFT common window period signal that represents the calculated FFT common window period and an FFT common window period signal that is output from the FFT common window period calculation circuit are input, and the FFT common window period signal is input. An antenna signal switching control signal for switching the plurality of antenna signals within a period other than or an antenna signal switching symbol signal representing the symbol position of the OFDM signal at the time of switching the plurality of antenna signals is calculated and output. A switching control circuit, an antenna signal switching circuit that switches the plurality of input antenna signals by the antenna signal switching control signal or the antenna signal switching symbol signal, and outputs a selection antenna signal, and outputs the selection antenna signal. Output terminal and output for outputting the FFT common window period signal Child, or a diversity adapter, characterized in that the diversity circuit and an output terminal further outputting the antenna signal switching symbol signal.

The present invention is a diversity receiving apparatus having a diversity circuit for receiving an OFDM signal which is an orthogonal frequency division multiplexing modulation type transmission signal for transmitting an information code by a plurality of carriers (carrier waves) which are orthogonal to each other. The diversity circuit includes a plurality of antenna signal input terminals for inputting a plurality of antenna signals, which are signals received by the antenna, and at least two or more antenna signals of the antenna signals input from the plurality of antenna signal input terminals. FFT common window period, which is a signal acquisition period into the FFT that is common to the OFDM signal and has a minimum inter-symbol interference noise level, and outputs an FFT common window period signal representing the calculated FFT common window period.
The common window period calculation circuit and the FFT common window period signal output from the FFT common window period calculation circuit are input, and the FFT
An antenna signal switching control signal for switching the plurality of antenna signals within a period other than the common window period or an antenna signal switching symbol signal representing the symbol position of the OFDM signal at the time when the plurality of antenna signals are switched is calculated and output. A diversity circuit including an antenna signal switching control circuit, and an antenna signal switching circuit for switching the plurality of input antenna signals according to the antenna signal switching control signal or the antenna signal switching symbol signal and outputting a selection antenna signal. In addition, the OFDM receiver demodulates the selected antenna signal by using the FFT common window period signal or the antenna signal switching symbol signal.

The present invention receives an OFDM signal, which is an orthogonal frequency division multiplexing modulation type transmission signal for transmitting an information code by a plurality of carriers (carrier waves) that are orthogonal to each other, and outputs it to an OFDM receiving apparatus connected in a subsequent stage. A diversity adapter having a diversity circuit for performing the diversity circuit, wherein the diversity circuit inputs a plurality of antenna signal input terminals for inputting a plurality of antenna signals which are signals received by the antenna, and the plurality of input antenna signals. By comparison, the antenna signal having the highest level of the transmission signal component contained in each antenna signal or its C / N value is selected, or the antenna having the highest level of the main wave contained in each antenna signal or its highest C / N value Select the signal or change the level of the transmission signal component other than the main wave included in each antenna signal. Select the smallest antenna signal to the level of the wave, and the input circuit section for outputting the number of the selected antenna signal as a selection antenna signal number, the plurality of antenna signals with the selected antenna signal number,
An FFT window period, which is a signal acquisition period into the FFT optimum for the antenna signal of the selected number, is calculated, a new FFT window period signal representing the calculated FFT window period, and an optimum FFT for the already selected antenna signal. A new FFT window period calculation circuit that outputs a current FFT window period signal that represents a window period, a current FFT window period signal and the new FFT window period signal that are input, and a period that the new FFT window period signal specifies and the current FFT window period signal. An antenna signal switching control signal for switching between an already selected antenna signal and a newly selected antenna signal within a period other than the period designated by the FFT window period signal, and the current FF at the same time as switching the antenna signal.
Antenna for calculating and outputting a selected FFT window period signal obtained by switching from the T window period signal to the new FFT window period signal, or an antenna signal switching symbol signal representing the symbol position of the OFDM signal at the time when the antenna signal is switched A signal switching control circuit, and an antenna signal switching circuit for switching the plurality of input antenna signals according to the antenna signal switching control signal and the selected FFT window period signal or the antenna signal switching symbol signal and outputting a selected antenna signal. A diversity circuit having an output terminal for outputting the selected antenna signal, an output terminal for outputting the selected FFT window period signal, or an output terminal for further outputting the antenna signal switching symbol signal. It is a diversity adapter.

The present invention is a diversity receiver having a diversity circuit for receiving an OFDM signal which is an orthogonal frequency division multiplexing modulation type transmission signal for transmitting an information code by a plurality of carriers (carrier waves) orthogonal to each other. The diversity circuit compares a plurality of antenna signal input terminals for inputting a plurality of antenna signals, which are signals received by the antenna, with the plurality of input antenna signals, and compares the levels of the transmission signal components included in each antenna signal or Select the antenna signal with the highest C / N value, or select the level of the main wave included in each antenna signal or the antenna signal with the highest C / N value, or select a signal other than the main wave included in each antenna signal. Select the antenna signal whose level of the transmission signal component of A circuit portion for outputting a number of the antenna signal as a selection antenna signal number, enter the selection antenna signal number of the plurality of antenna signals and,
An FFT window period, which is a signal acquisition period into the FFT optimum for the antenna signal of the selected number, is calculated, a new FFT window period signal representing the calculated FFT window period, and an optimum FFT for the already selected antenna signal. A new FFT window period calculation circuit that outputs a current FFT window period signal that represents a window period, a current FFT window period signal and the new FFT window period signal that are input, and a period that the new FFT window period signal specifies and the current FFT window period signal. An antenna signal switching control signal for switching between an already selected antenna signal and a newly selected antenna signal within a period other than the period designated by the FFT window period signal, and the current FF at the same time as switching the antenna signal.
Antenna for calculating and outputting a selected FFT window period signal obtained by switching from the T window period signal to the new FFT window period signal, or an antenna signal switching symbol signal representing the symbol position of the OFDM signal at the time when the antenna signal is switched A signal switching control circuit, and an antenna signal switching circuit for switching the plurality of input antenna signals according to the antenna signal switching control signal and the selected FFT window period signal or the antenna signal switching symbol signal and outputting a selected antenna signal. A diversity circuit including: and the OFDM receiver demodulates the selected antenna signal by using the FFT common window period signal or further the antenna signal switching symbol signal. It is a device.

According to the present invention, an input terminal for inputting the selected antenna signal output from the diversity adapter, and an input terminal for inputting the FFT common window period signal,
Alternatively, further, an input terminal for inputting the antenna signal switching symbol signal and the FFT for the selected antenna signal
An OFDM receiving apparatus comprising: a common window period signal or further means for demodulating using the antenna signal switching symbol signal.

The present invention is a diversity adapter having a diversity circuit for receiving a transmission signal and outputting it to a receiving device connected to a subsequent stage, wherein the diversity circuit is a signal received by an antenna. The antenna signal input terminals for inputting the antenna signals are compared with the input antenna signals, and the antenna signal having the highest level or C / N value of the transmission signal component included in each antenna signal is selected. Or the level of the main wave included in each antenna signal or its C
/ N selecting the antenna signal having the highest value, or selecting the antenna signal in which the level of the transmission signal component other than the main wave included in each antenna signal is the smallest with respect to the level of the main wave, and the selection antenna The diversity adapter is a diversity circuit having an output terminal for outputting a signal.

In the present invention, the diversity circuit is a diversity adapter characterized in that it outputs a selected antenna signal of the same form as the antenna signal of the first form inputted to the diversity adapter.

In the present invention, the FFT common window period calculation circuit included in the diversity circuit is received first among the OFDM signals included in all antenna signals input from the plurality of antenna signal input terminals. O
A diversity adapter or a diversity receiver, which is an FFT common window period calculation circuit that calculates and outputs an optimum period as an FFT common window period for capturing a reception signal having an FDM signal at the head as an FFT. .

In the present invention, the FFT common window period calculating circuit included in the diversity circuit receives the earliest OFD of the OFDM signals included in the newly selected antenna signal and the already selected antenna signal.
F which is calculated and output as the FFT common window period, which is the optimum period for fetching the received signal having the M signal as the head into the FFT
It is a diversity adapter or diversity receiving device characterized by being an FT common window period calculation circuit.

In the present invention, the FFT common window period calculation circuit included in the diversity circuit minimizes the inter-symbol interference noise level of the OFDM signal included in all the antenna signals input from the plurality of antenna signal input terminals. It is a diversity adapter or a diversity receiving device, which is an FFT common window period calculation circuit that calculates and outputs a period as an FFT common window period.

In the present invention, the FFT common window period calculation circuit included in the diversity circuit is a period in which the inter-symbol interference noise level of the OFDM signal included in the newly selected antenna signal and the already selected antenna signal becomes the smallest. Is an FFT common window period calculation circuit that calculates and outputs as the FFT common window period, and is a diversity adapter or diversity receiver.

In the present invention, the diversity circuit inputs the individual antenna signals, separates the transmission signal components contained in the antenna signals into components of a constant delay time width, and maximizes the maximum power level among them. And a second value that increases with a total power level of components in a predetermined delay time range, and then a multiplication value of the first value and the second value, A plurality of antenna signal evaluation circuit that outputs as an antenna signal evaluation signal, and input the plurality of antenna signal evaluation signals,
A diversity adapter or a diversity receiver, which is a diversity circuit including an antenna signal selection circuit that selects the antenna signal number having the highest evaluation value and outputs the selected antenna signal number.

In the present invention, the antenna signal evaluation circuit calculates a correlation value between signal portions having the same temporal waveform included in the OFDM signal included in the input antenna signal and outputs it as a correlation signal. A G correlation calculation circuit, a correlation peak value calculation circuit that inputs the correlation signal output from the G correlation calculation circuit, calculates a peak value of the correlation signal, and outputs the correlation signal, and a correlation signal output from the G correlation calculation circuit OFD for inputting and outputting the integrated value of the correlation signal for a predetermined period as the power value of the OFDM signal
The M signal power calculation circuit, the peak value of the correlation signal output from the correlation peak value calculation circuit, and the power value of the OFDM signal output from the OFDM signal power calculation circuit are input, and the peak value and the power value are input. A diversity adapter or a diversity receiving device, which is an antenna signal evaluation circuit including an evaluation value calculation circuit that outputs a multiplication value of 1 as an antenna signal evaluation signal.

In the present invention, the diversity circuit is a diversity circuit having a delay circuit for delaying a part of antenna signals more than other antenna signals, which is a diversity adapter or a diversity receiving apparatus.

In the present invention, the antenna signal input terminal has a structure in which a cap having a terminating resistor can be attached when an antenna signal is not input, or has a switch connected to the terminating resistor when not in use. It is a diversity adapter or diversity receiver.

In the present invention, the antenna selection frequency signal is constructed by calculating the frequency with which the number of each antenna signal is selected from the selected antenna signal number output from the antenna signal selection circuit and the antenna selection frequency signal. Antenna selection frequency signal output terminal to output the
Alternatively, there is provided a diversity adapter or diversity receiving device having a display unit for displaying the antenna selection frequency signal.

In the present invention, a plurality of delay profiles obtained by separating the level of the transmission signal component or the OFDM signal component contained in each antenna signal for each component having a constant delay time width, or included in each antenna signal. OFD
A plurality of correlation signal waveforms calculated from the M signal are output as signals having the same positional relationship with respect to a reference signal and can be observed simultaneously or individually. A display unit capable of observing the waveforms of the plurality of correlation signals simultaneously or individually as waveforms having the same positional relationship with the reference signal;
Alternatively, the delay profile or the waveform of the correlation signal may be output simultaneously with an output terminal that outputs a signal that can also observe the FFT common window period, or a display unit that can also observe the FFT common window period. The output profile that outputs the signal that clearly shows the waveform of the correlation profile or the delay profile calculated from the selected antenna signal, or the waveform of the correlation profile or the delay profile calculated from the selected antenna signal It is a diversity adapter or a diversity receiving device characterized by having a display section clearly indicated by a line of a different type such as a thickness line.

[0046]

FIG. 1 shows a circuit configuration of a diversity receiving system according to a first embodiment of the present invention.
This diversity receiving system includes an antenna 10a,
10b, the diversity adapter 20 and the OFDM receiver 60 are combined, and the antennas 10a, 10
The diversity adapter 20 is inserted between the RF circuit part indicated by b and the OFDM receiver 60 to form a diversity receiver system for connecting the two.

This diversity receiving system has a structure in which the IF signal in the intermediate frequency band converted and output by the RF circuit section which is a high frequency circuit section connected to the antennas 10a and 10b is input to the diversity adapter 20. There is. However, in the diversity adapter R
The system may be configured such that the F circuit section is provided and the RF signal, which is the signal received by the antenna, is directly input to the diversity adapter. In addition, the RF signal is converted to the above IF.
The system may be configured to input an IF signal in a frequency band different from the frequency band of the signal or a signal obtained by converting the signal into a baseband signal.

In this embodiment, an example of inputting an IF signal will be described, but this embodiment can be applied to any system configuration. To facilitate this application,
These types of signals input to the diversity adapter will be collectively referred to as “first type antenna signals” or simply “antenna signals”. Further, the number of antennas may be arbitrary, but in order to avoid complication of the drawing, description will be made below using the case of two antennas.

In FIG. 1, the IF signal (antenna signal of the first embodiment) output from the RF circuit section connected to the antennas 10a and 10b is an antenna signal input terminal 21a.
And 21b to the diversity adapter 20, and further to the diversity circuit 30 therein.

Next, the internal circuit configuration of the diversity circuit 30 will be described in detail. The IF signal a (antenna signal a in the first form) output from the RF circuit unit of the antenna 10a is input to the antenna signal delay circuit 31a and the down converter 32a. The IF signal a (antenna signal a) input to the down converter 32a is down-converted to the baseband signal a and then input to the antenna signal evaluation circuit 33a. If the antenna signal of the first form is a baseband signal, this circuit is unnecessary.

The antenna signal evaluation circuit 33a is a circuit for evaluating the quality of the received OFDM signal from the level of the OFDM signal included in the baseband signal a and the like, and outputs the evaluation result as the antenna signal evaluation signal a. This evaluation method will be described later. Antenna signal delay circuit 31
Reference numeral a is a delay circuit whose main purpose is to adjust the time delay for this evaluation.

The IF signal b (antenna signal b) output from the RF circuit section of the antenna 10b is processed in the same manner, converted down by the down converter 32b, and the antenna signal evaluation circuit 33b evaluates the antenna signal. The signal b is output.

The antenna signal evaluation signal a and the antenna signal evaluation signal b output from the antenna signal evaluation circuits 33a and 33b are input to the antenna signal selection circuit 34, and the number of the antenna signal having the highest evaluation value is calculated. And
The selected antenna signal number representing the calculated number is output.

On the other hand, the FFT common window period calculation circuit 35
It is a circuit that calculates a signal acquisition period into an optimum FFT that is common to OFDM signals included in a plurality of input antenna signals. This period is calculated by the down converter 3
The output signals of 2a and 32b may be directly input and calculated. However, the antenna signal evaluation circuit 33 of the present embodiment
Then, in the process of calculation, the correlation signal described in FIG. 4 is calculated. Therefore, the correlation signal is used to calculate the signal fetch period into the FFT. Therefore, FFT
The common window period calculation circuit 35 includes the antenna signal evaluation circuit 3
The correlation signals a and b output from 3a and 33b are connected so as to be input. The method of calculating the optimum extraction period will be described later, as with the evaluation method.

From the FFT common window period calculation circuit 35, the FFT representing the calculated optimum signal fetch period into the FFT.
The common window period signal and the symbol synchronization signal calculated at the same time are output. The FFT common window period signal is input to the antenna signal switching control circuit 36 and, at the same time, output to the outside of the diversity adapter 20 through the output terminal 24.

Further, the symbol synchronization signal is input to the antenna signal switching control circuit 36, and at the same time, is input to the antenna signal evaluation circuits 33a and 33b and the clock pulse generation circuit 37. Antenna signal evaluation circuits 33a and 33
In b, the timing of the signal to be evaluated is determined using this symbol synchronization signal. Further, the clock pulse generating circuit 37 calculates and controls a control signal for controlling the clock pulse frequency used in the digital circuit by using the symbol synchronizing signal. Since the FFT common window period signal also becomes a signal having a symbol period as a cycle, this signal may be used as it is as a symbol synchronization signal.

The antenna signal switching control circuit 36 determines the number of the antenna signal to be connected using the input FFT common window period signal, the symbol synchronization signal and the selected antenna signal number, and switches the antenna signal to be actually connected. This is a circuit for calculating and outputting an antenna signal switching control signal for controlling the signal switching circuit 38.

There are many possible methods for determining the antenna signal to be selected. Here, one example thereof will be taken up and described below. That is, for example, the number b that occurs most frequently in the input selected antenna signal number is detected. Then, the antenna signal a already selected
When the frequency of occurrence of the number b is higher than the frequency of occurrence of the number a of a certain level, the period other than the period designated by the FFT common window period signal, for example, the FF of FIG.
Immediately after the period designated by the T common window period signal has ended, the antenna signal switching control signal in FIG. 10B may be changed.

At this time, at the same time, an antenna signal switching symbol signal representing the symbol for switching the antenna signal, for example, the signal shown in FIG. 10C is generated and output from the antenna signal switching control circuit 36, and further through the output terminal 23. Output to outside the diversity adapter 20.

In the antenna signal switching circuit 38, according to the antenna signal switching control signal output from the antenna signal switching control circuit 36, the antenna signal newly selected from the antenna signals connected until then, for example, the antenna signal a, for example, the antenna signal a. The signal is switched to the antenna signal b and output to the outside of the diversity adapter 20 through the output terminal 22.

Next, the details of the signal processing executed by the antenna signal evaluation circuit 33 will be described in more detail. FIG. 11 is a diagram showing a circuit configuration of the antenna signal evaluation circuit 33 in the diversity receiving system according to the exemplary embodiment of the present invention. The G (guard interval) correlation calculation circuit 41
This circuit is composed of the same circuits as the delay circuit 3a and the correlation calculation circuit 4a in FIG. This circuit is a circuit for calculating and outputting a correlation value between temporally identical signal portions included in the OFDM signal, and the correlation signal illustrated by the thick solid line in FIG. 12 is output. The calculated correlation signal is not only input to the correlation peak value calculation circuit 42 and the OFDM signal power calculation circuit 43, but also output from the antenna signal evaluation circuit 33 for use in the FFT common window period calculation circuit 35 (FIG. 1). Keep it.

The correlation peak value calculation circuit 42 is a circuit for calculating the maximum value of the waveform shown by the thick solid line in FIG. Further, the OFDM signal power calculation circuit 43 is a circuit for calculating the power value of the OFDM signal, and is a summation (area of the signals in the shaded area in FIG. 12 of the correlation signal for a predetermined period, for example, three times the guard interval). ) Is calculated to calculate this power value.

The reason why the value proportional to the power value of the OFDM signal can be calculated by this calculation is as follows. That is, FIG. 5C obtained by performing complex multiplication in the correlation calculation circuit 4.
The level of the rectangular waveform part is the square value of the amplitude of the guard interval signal at each time. On the other hand, the power of the OFDM signal is a value obtained by averaging the squared values of the amplitude values over a sufficiently long time. Therefore, the peak value of FIG. 5 (e) obtained by adding the values of this rectangular portion is approximately OFDM.
The value is proportional to the power value of the signal.

The waveform of the correlation signal output from the G correlation calculating circuit 41 becomes a triangular waveform as shown in FIG. 13A even when only one wave is received. However, since the length of its base becomes a constant value that is twice the guard interval, its area becomes a value proportional to the peak value of the correlation signal, and thus the power value of the OFDM signal.

When a plurality of delayed waves are mixed in the received signal, for example, when two OFDM signals are simultaneously received, the waveform of the correlation signal is as shown in FIG. 13 (b). 13 (c) is configured as the sum of two triangular waveforms. Therefore, by calculating the area of the shaded area in FIG. 12, that is, the sum of the signals of the shaded area, the received OFD
A value proportional to the power of the M signal can be calculated.

The correlation signal peak value calculated by the correlation peak value calculation circuit 42 and the OFDM signal power value output from the OFDM signal power calculation circuit 43 are multiplied by the multiplication circuit 44.
And then output as an antenna signal evaluation signal.

The multiplication by the multiplication circuit 44 is carried out to solve the following problems. That is, in order to solve the first problem described with reference to FIG. 8, the power value of the OFDM signal calculated by the OFDM signal power calculation circuit 43 may be used as the antenna signal evaluation signal. However, in this case, another problem occurs. That is, the OFDM calculated from the correlation signal of the broken line when only one main wave is received
O calculated from the correlation signal indicated by the solid line when a signal composed of two waves having substantially the same level as the power value of the signal is received.
The power values of the FDM signal are almost the same.

However, in the case of a received signal composed of two waves, carriers are generated whose phases are inverted to each other and whose level is greatly reduced. Therefore, even with the same power, 2
A code having a lower code error rate can be decoded in the case of one wave than in the case of wave.

The power value of the OFDM signal is multiplied by the peak value in order to express the difference between the two waves and the one wave. Therefore, the value to be multiplied is the square root of the peak value, etc.
Any value can be used as long as the value increases with the power level of the main wave.

By selecting an antenna signal using this antenna signal evaluation signal, the antenna signal having the highest C / N value of the received OFDM signal can be selected, and O
When the powers of the FDM signals are the same, it becomes possible to select an antenna signal having a high main wave level. Then, it becomes possible to always realize diversity reception in which the optimum antenna signal for OFDM signal demodulation can be selected.

In the above description, the antenna signal evaluation circuit has been described only in the case where the correlation signal is used for evaluation. However, the antenna signal evaluation circuit can be calculated using a signal capable of detecting the distribution and level of the delayed wave component of the OFDM signal included in the antenna signal. Obviously, that's fine. For example, a delay profile calculated by a method such as frequency analysis of a pilot signal inserted in the OFDM signal may be used. In this case, the peak value of the delay profile is used instead of the peak value of the correlation signal, and when the amplitude value of the delay profile is proportional to the power value of each OFDM signal component, the total sum (area) of the waveforms of the correlation signal
Instead of, the sum of the waveforms of the delay profile (area) may be used to perform the same calculation.

Next, the contents of the signal processing executed by the FFT common window period calculation circuit 35 will be described in more detail. 14
FIG. 3 is a circuit configuration example of an FFT common window period calculation circuit 35 in the diversity reception system according to the first embodiment of the present invention. The correlation signal a calculated by the antenna signal evaluation circuit 33a of FIG. 1 and the correlation signal b calculated by the antenna signal evaluation circuit 33b are input to the FFT window period calculation circuit 51a and the FFT window period calculation circuit 51b of FIG. 14, respectively. It

The FFT window period calculation circuit 51a calculates the OFDM contained in the antenna signal a from the input correlation signal a.
It is a circuit that calculates the optimum period for fetching the signal into the FFT for the signal and outputs the calculated period as the FFT window position signal.

The simplest circuit is the time when the peak value of FIG. 12 is obtained or the time which is a fixed clock time before this time, and the effective symbol period T before this is set to the end.
It is a circuit for calculating s as an optimum period for fetching a signal into the FFT. However, this circuit has a drawback that inter-symbol interference noise is generated due to the preceding wave when the preceding wave has a small level.

As a circuit for reducing this drawback, for example, a threshold value that is a constant fraction of the peak value is set, the earliest time when the threshold value is exceeded is detected, and the time at the end of the preceding wave is detected from this time point. A circuit is conceivable that calculates and at the same time calculates the effective symbol period before the calculated last time as the optimum period to be taken into the FFT.

However, in the present invention, any circuit may be used as long as it is a circuit that calculates the optimum FFT window position for the OFDM signal included in the corresponding antenna signal. Therefore, in the following description, the former circuit is used.

In FIG. 14, when the OFDM signal contained in the antenna signal a has the waveform of the timing shown in FIG. 15A, the FFT window period calculation circuit 51a to the F signal shown in FIG.
The FT window position signal a is output. Also, the antenna signal b
When the OFDM signal included in the signal has the waveform of the timing shown in FIG. 15C, the FFT window period calculation circuit 51b outputs the waveform shown in FIG.
The FFT window position signal b in (d) is output.

The FFT window position signal a and the FFT window position signal b are input to the earliest period calculation circuit 52 of FIG. The earliest period calculation circuit 52 selects the most advanced FFT window position signal and outputs it as the FFT common window period signal shown in FIG.

By the way, if the OFDM signal is a signal within the same symbol period, the signal of which period is extracted and F
Correct demodulation is possible even with FT. However, when signals of adjacent symbols are mixed in the extracted signals, inter-symbol interference noise occurs, which causes a problem that the quality of the decoded code is significantly deteriorated.

However, if the delay time of the received OFDM signal is equal to or less than the length of the guard interval, a plurality of periods of the FFT common window period signal calculated by the FFT common window period calculation circuit 35 as described above are used. Are within the same symbol period of all OFDM signals received at the antennas.
Therefore, by always extracting the signal in the period designated by the FFT common window period signal and performing FFT, it is possible to always decode a good code without intersymbol interference noise regardless of which antenna signal is switched. Become.

If the antenna signal is switched in a period other than the period designated by the FFT common window period signal,
The effect of switching antenna signals can be almost ignored. Therefore, even if the antenna signal is frequently switched, the code error does not increase, and the best antenna signal can always be selected and used.

As the FFT window period calculation circuit, FF
When the position of the period of width Ts for fetching a signal to T is moved,
The position of the period in which the generated inter-symbol interference noise is minimized is calculated using, for example, the delay profile described above,
The same effect can be obtained by using a circuit that outputs the FFT window position signal. At this time, the period during which the inter-symbol interference noise level is minimized is calculated for each antenna signal, and the FFT common window period signal is calculated by the same procedure as above using the calculated plurality of FFT window position signals. Is also good.

Alternatively, from delay profiles obtained by adding delay profiles of all antenna signals,
The period in which the inter-symbol interference noise level is minimum for all antenna signals may be calculated and output as the FFT common window period signal. Alternatively, the inter-symbol interference noise level is minimized for these two antenna signals by using the delay profile obtained by adding the delay profiles of the already selected antenna signal and the newly selected antenna signal. The period may be calculated and output as the FFT common window period signal. In addition, a correlation signal may be used instead of the above delay profile.

Returning to FIG. 1, the diversity adapter 2
The selected antenna signal (IF signal) selected from 0 and output from the output terminal 22, the antenna signal switching symbol signal output from the output terminal 24, and the FFT common window signal output from the output terminal 23 are respectively the OFDM receiving apparatus. OFDM through 60 input terminals 62, 63, 64
The selected antenna signal input into the receiving device 60 is OFD.
M demodulated.

FIG. 16 is a diagram showing an internal configuration of the OFDM receiver 60 in the diversity receiving system according to the first embodiment of the present invention. By the way, normal O
The circuit configuration of the FDM receiver performs the same processing as in FIG. 5 in the symbol synchronization circuit 68, and uses the calculated peak position of the correlation signal to establish symbol synchronization of the OFDM signal included in the input IF signal. It is configured. Also,
The position of the signal taking-in period into the FFT is calculated based on the peak position of this correlation signal, and the calculated FFT window period signal is input to the FFT signal extracting circuit 66 to obtain the input IF.
The signal extracted from the baseband signal converted down by the down converter 65 is FFT demodulated.

However, the FFT window period newly calculated by the OFDM receiver 60 is equal to the diversity adapter 2
Immediately after switching the antenna signal at 0, the signal shifts from the optimum FFT acquisition period as shown in FIG. 9B for a certain period, and signals of adjacent symbols are extracted and FFT is performed. Therefore, inter-symbol interference noise increases and the quality of the decoded code deteriorates significantly.

Therefore, in this embodiment, the FFT common window period signal and the antenna signal switching symbol signal output from the diversity circuit 30 of the diversity adapter 20 are input to the OFDM receiver 60. Then, the FFT signal extraction circuit 66 of FIG. 16 extracts the signal to be input to the FFT using the input FFT common window period signal.

In this way, if the signal in the period designated by the FFT common window period signal is extracted, as described above, the signal acquisition period in the FFT is always the same symbol of the switched OFDM signal. Within the period, signals of adjacent symbols are not mixed. for that reason,
Regardless of which antenna signal is switched, it is possible to always decode a good code without intersymbol interference noise.

On the other hand, the antenna signal switching symbol signals input at the same time are signals for informing the OFDM receiving apparatus 60 of the switching timing of the antenna signals.
This signal can be used in various signal processing processes.

For example, in the Lo synchronization circuit 69 for reproducing the local oscillation frequency, the signal of the current symbol and the signal of the previous symbol are compared to detect and control the frequency shift. for that reason,
A large error occurs in the amount of frequency deviation detected in the symbol immediately after switching the antenna signal, which causes a problem that a malfunction occurs in the control of the local oscillation frequency.

However, by using this antenna signal switching symbol signal and controlling so as to ignore the frequency shift amount detected in the symbol period in which the antenna signal is switched, a malfunction caused by the control of the local oscillation frequency is prevented. can do.

As described above, from the diversity adapter,
The case where the IF signal which is the antenna signal of the same form as the input IF signal which is the antenna signal of the first form is output has been described. However, before or after the antenna signal switching circuit 38, an antenna signal of a form different from the input antenna signal of the first form, for example, an IF signal or base in an intermediate frequency band different from the antenna signal of the first form is input. It is also possible to output the antenna signal of the second form obtained by performing the second reception processing such as down-converting to the band signal.

However, in this case, the OFDM receiver 60
Must be changed to a receiving apparatus that processes the antenna signal of the second form. For example, when the antenna signal of the second form is a baseband signal, it is necessary to use a receiver having a circuit configuration in which the down converter 65 in the circuit of FIG. 16 is removed. As another example, the RF signal is directly input from the antenna as the antenna signal of the first form, converted into the IF signal which is the antenna signal of the second form inside the diversity adapter, and is output. May be. In any case, the same effect as this embodiment can be obtained.

As a form against the present embodiment, there is a form in which the diversity adapter and the OFDM receiver are integrated. However, in this form, it is necessary to prepare an expensive diversity-dedicated OFDM receiver for diversity reception that is relatively infrequently used, which is a heavy burden on the user. Further, the diversity dedicated OFDM receiver has a problem that the circuit size increases and the receiver becomes large in size, as is apparent from the increase of the input terminals of the antenna signal. In addition, in order to increase the number of diversity antennas, a problem arises in that it is necessary to purchase a diversity-only OFDM receiver that is large and expensive in advance.

On the other hand, in the system configuration of FIG.
The FDM receiver 60 includes a down converter 65 shown in FIG.
And the symbol synchronization circuit 68 are built in, there is a disadvantage that the down converters 32a and 32b built in the diversity adapter 20 and the G correlation calculation circuit 41 (FIG. 11) are wasteful, but the diversity is generated. Since the adapter 20 does not require an expensive circuit such as the FFT circuit in the OFDM signal demodulation circuit 67 of FIG. 16, it can be manufactured relatively inexpensively. Therefore, the diversity receiving system as a whole has an effect that the system can be configured at a low cost as compared with the case where the diversity adapter and the OFDM receiving device are integrated.

Moreover, if both the form of the antenna signal input to the diversity adapter and the form of the antenna signal selected and output by the diversity adapter are the same IF signal as the input signal of the ordinary receiver, diversity reception is performed. A user who wants to purchase can purchase an ordinary OFDM receiver having an input terminal for the FFT common window period signal for diversity and an antenna signal switching symbol signal in advance, and only need to purchase a relatively inexpensive diversity adapter. The effect of enabling diversity reception is obtained.

At this time, normal OFDM purchased in advance
Since only one IF signal needs to be input to the receiver, the device is small and can be used as a normal OFDM receiver without any trouble. Further, when it is desired to increase the number of antennas for diversity reception, it suffices to replace a relatively inexpensive diversity adapter with the effect that the burden on the user can be greatly reduced.

As described above, when the diversity adapter and the OFDM receiver according to the present embodiment are used, the antenna signal having the high power of the received OFDM signal and the high C / N value of the included OFDM signal is correctly selected. In addition, if the power is the same, the antenna signal with a high main wave level will be selected, so
The effect of achieving diversity reception in which the optimum antenna signal for demodulating a DM signal can be selected is obtained.

Further, by extracting the signal in the period designated by the FFT common window period signal and performing the FFT, it is possible to always demodulate a good code without intersymbol interference noise regardless of which antenna signal is switched. Like Therefore, even if the antenna signal is frequently switched, the code error does not increase, and the best antenna signal can always be selected and used.

[0100] Further, compared to the dedicated diversity receiver, diversity reception can be performed by only purchasing a relatively inexpensive diversity adapter.
The burden on the user can be greatly reduced.

Further, since the ordinary OFDM receiver used at the same time needs to input only one IF signal, the size of the apparatus becomes small, and the effect that the ordinary OFDM receiver can be used without any trouble can be obtained.

Next, FIG. 17 shows the circuit configuration of the diversity receiving system according to the second embodiment of the present invention.
In this embodiment, the configuration of the diversity receiving system according to the first embodiment is further developed to
This is a configuration of a diversity receiving system applicable to transmission signals other than FDM signals.

This diversity receiving system includes the antennas 10a and 10b and the diversity adapter 2
0'and the receiving device 60 'are combined, and the antenna 1
A diversity receiving system is constructed by inserting a diversity adapter 20 'between the RF circuit section marked with 0a and 10b and the receiving device 60' to connect the two.

In FIG. 17, antennas 10a and 10b are provided.
IF signal output from the RF circuit unit connected to the
Signal of the form) is the antenna signal input terminal 21
It is input to the diversity adapter 20 'from a'and 21b', and further to the diversity circuit 30 'therein. The diversity circuit 30 'receives the two IF signals as inputs, selects a good antenna signal of them as a selected antenna signal, and outputs the selected antenna signal to the output terminal 22'. Then, the receiving device 60 ′ demodulates the selected antenna signal.

As a concrete example of the above selection by the diversity circuit 30 ', a plurality of input antenna signals are compared and the antenna signal having the highest level of the transmission signal component contained in each antenna signal or the C / N value thereof is selected. The level of the main wave included in each antenna signal or the antenna signal having the highest C / N value is selected, or the level of the transmission signal component other than the main wave included in each antenna signal is the level of the main wave. Select the smallest antenna signal for.

In this way, if the diversity circuit connected to the preceding stage of the receiving device is separated from the receiving device to form the diversity adapter, a user who wants to perform diversity reception only needs to purchase a relatively inexpensive diversity adapter. The effect of enabling diversity reception is obtained. At this time, since only one IF signal needs to be input to the normal receiver purchased in advance, the device becomes small in size and can be used as a normal receiver without any trouble. Further, when it is desired to increase the number of antennas for diversity reception, it suffices to replace a relatively inexpensive diversity adapter with the effect that the burden on the user can be greatly reduced.

As described above, when the diversity adapter according to the present embodiment is used, the diversity reception can be performed only by additionally purchasing the relatively inexpensive diversity adapter, so that the burden on the user can be greatly reduced.

Further, since the ordinary receiver used at the same time needs to input only one IF signal, the device becomes small in size, and the effect that the ordinary receiver can be used without any trouble is obtained.

Next, FIG. 18 shows a circuit configuration of a diversity receiving system according to the third embodiment of the present invention.
This system is based on the diversity adapter and O
This is an integrated FDM receiver. The basic idea is the first except that the redundant circuit that is wasted by the integration is deleted, and that the signal passing from the diversity circuit to the FFT signal extraction circuit is changed to the baseband signal. It is the same as the embodiment.

RF connected to antennas 10a and 10b
The IF signal (antenna signal of the first form) output from the circuit unit is input to the diversity dedicated OFDM receiver 70, and further input to the diversity circuit 30 therein.

FIG. 19 is a diagram showing the internal structure of the diversity circuit 30. IF signal a output from the RF circuit unit of the antenna 10a (antenna signal a of the first form)
Is down-converted into a baseband signal a by a down converter 32a, and then an antenna signal delay circuit 31'a
Is input to the antenna signal evaluation circuit 33a. Similarly, the IF signal b output from the RF circuit unit of the antenna 10b is also down-converted to the baseband signal b, and then the antenna signal delay circuit 31'b and the antenna signal evaluation circuit 33 are provided.
Input to b.

From the antenna signal evaluation circuit 33a and the antenna signal evaluation circuit 33b to the antenna signal switching control circuit 3
Since the processing up to 6 is the same as that of the first embodiment, the description is omitted.

The antenna signal switching circuit 38 'inputs the baseband signal a (second form antenna signal a) output from the down converter 32a instead of the IF signal (first form antenna signal a). It is a circuit having the same function as the antenna signal switching circuit 38 of FIG. That is, the baseband signal a and the baseband signal b (antenna signal a and antenna signal b) output from the antenna signal delay circuit 31′a and the antenna signal delay circuit 31′b are output from the antenna signal switching control circuit 36. It is a circuit that selects and outputs according to the antenna signal switching control signal.

The baseband signal (antenna signal) selected by the antenna signal switching circuit 38 'and the FFT common window period signal calculated by the FFT common window period calculation circuit 35 are
It is input to the FFT signal extraction circuit 66 of FIG.
Then, the signal portion of the period designated by the FFT common window period signal is extracted from the selected baseband signal, and O
The signal is input to the FFT circuit in the FDM signal demodulation circuit 67 and demodulated.

Antenna signal switching control circuit 36 of FIG.
The antenna signal switching symbol signal output from the Lo synchronization circuit 69 (FIG. 1) is a synchronization circuit of the local oscillation frequency.
8), the control is performed so that the control of the local oscillation frequency is stopped during the fixed symbol period in which the baseband signal (antenna signal) is switched.

In the diversity dedicated receiver of the present embodiment, since the diversity circuit is integrated, the receiver becomes large and expensive, and if an attempt is made to increase the number of antennas for diversity, the expensive dedicated diversity receiver is anew. Although it has the drawback of having to repurchase, it is possible to obtain the same antenna signal selection performance and code error rate reduction effect as in the first embodiment, and it is easy to digitize the antenna signal delay circuit. Thus, the effect of reducing the scale of the diversity circuit can be obtained.

As described above, when the diversity-dedicated OFDM receiver according to this embodiment is used, not only the same effect as in the case of using the diversity adapter but also the effect of reducing the scale of the diversity circuit can be obtained.

Next, the circuit configuration of the diversity receiving system according to the fourth embodiment of the present invention will be described. This embodiment relates to the internal circuit configuration of the diversity circuit 30, and the signal input to the antenna signal delay circuit and the antenna signal switching circuit is the antenna signal of the first form or the antenna signal of the second form. The same applies to the circuits of FIG. 1 and FIG. 19 except for some points.

Next, FIG. 20 shows a circuit configuration of the diversity circuit 30 in the diversity receiving system according to the fifth embodiment of the present invention. The difference from the circuit of FIG. 19 is only that a new delay circuit 39a is inserted between the down converter 32a connected to one antenna, for example, the antenna a and the antenna signal delay circuit 31'a. Therefore, the concept of the signal processing method of the diversity circuit 30 of FIG. 20 will be described below.

The diversity receiving system according to the present embodiment is effective in the following propagation path environment. That is, as illustrated in FIG. 21, a tall building blocks the space between the transmitter and the receiver so that no waves directly reach the antenna a, but a wave reflected by a distant mountain or a tall building is reflected by the antenna b.
It is the case that can be received by.

In this case, a time difference exceeding the guard interval may occur between the OFDM signals included in the two antenna signals, as shown in FIGS. 22 (a) and 22 (c). In this case, the optimum FFT window period signal calculated for each antenna signal is as shown in FIGS. 22 (b) and 22 (d), which is the preceding period of the two periods shown in FIG. Even if the period of b) is calculated as a common period, the signal of the horizontal line part which is a part of the signal of the adjacent symbol of the antenna signal b of FIG.
Since it is input to, there arises a problem that inter-symbol interference noise occurs.

However, if the preceding antenna signal a is delayed in advance as shown in FIG. 22 (e), the optimum fetch period into the FFT will be as shown in FIG. 22 (f), and even if the antenna signal is switched. No inter-symbol interference noise occurs in FIG.
It becomes possible to calculate the signal acquisition period into the common FFT shown in (g).

The delay circuit 39a newly inserted in FIG.
Is inserted to delay the preceding antenna signal a for a certain period. Therefore, in practice, it may be inserted anywhere between the antenna 10a and the antenna signal delay circuit 31'a. Also, the antenna signal delay circuit 3
The delay time of 1'a may be lengthened. However, in this case, the FFT window position signal a calculated by the FFT window period calculation circuit 51a of FIG. It is necessary to change so as to calculate the FFT common window period signal. Further, a delay circuit 39a, a delay circuit 39b (not shown), etc. are provided for each antenna signal so that the delay time of each delay circuit can be controlled by the delay time of the main wave of the OFDM signal included in the antenna signal. It goes without saying that it is preferable to keep it.

The signal processing of the other circuits may be carried out in the same manner as in the first and second embodiments. Therefore, in this embodiment, not only the same effects as in the first and second embodiments are obtained, but even if there is an antenna that receives an OFDM signal delayed beyond the guard interval, inter-symbol interference noise is generated. It is possible to obtain a new effect that good diversity reception can be achieved in which no occurrence occurs.

As described above, when the system is configured using the diversity circuit according to the present embodiment, not only the same effects as those of the first and second embodiments are obtained, but also the OFDM delayed beyond the guard interval is obtained. Even if there is an antenna for receiving a signal, it is possible to obtain the effect of realizing good diversity reception in which inter-symbol interference noise does not occur.

Next, FIG. 23 shows the internal structure of the FFT common window period calculation circuit 35 in the diversity receiving system according to the fifth embodiment of the present invention. 23, unlike the circuit of FIG. 14, the correlation signal a calculated by the G correlation calculation circuit 41 of the antenna signal evaluation circuit 33a of FIG.
And the correlation signal b calculated by the G correlation calculation circuit 41 of the antenna signal evaluation circuit 33b are added by the addition circuit 53, and then 1
It is input to one FFT window period calculation circuit 51. Then, the optimum FFT for the added signal of the correlation signal a and the correlation signal b
A period for fetching a signal into the FFT common window period is calculated and output as an FFT common window period signal.

In this circuit, the optimum signal acquisition period for the FFT, which is common to all antenna signals, is automatically calculated, so that not only the same effect as that of the circuit of FIG. It is possible to obtain a new effect that can reduce the.

FIG. 24 shows the internal structure of the diversity circuit in the diversity receiving system according to the fifth embodiment of the present invention. Similar to the fourth embodiment, it can be applied to the circuits of FIGS. 1 and 19. In the present embodiment, description will be given on the premise of the system configuration of FIG.

FIG. 25 shows the internal structure of the new-current FFT window period calculation circuit 40 in the present embodiment. The first feature of the present embodiment is that the optimum FF common to a plurality of antenna signals is used.
Instead of the FFT common window period signal indicating the signal fetch period into T, the selected FFT window period signal indicating the optimum signal fetch period into the FFT for the selected antenna signal is calculated and output. It is a point. Therefore, the FFT common window period calculation circuit 35 of FIG.
It was replaced with the T window period calculation circuit 40.

The second feature is that the timing for switching the antenna signal is changed in accordance with the change according to the first feature. Therefore, the content of the processing performed by the antenna signal switching control circuit 36 of FIG. 1 is changed.

Circuits other than these two circuits may be operated in the same manner as in the first embodiment, and therefore description thereof will be omitted. Hereinafter, signals of the new current FFT window period calculation circuit 40 and the antenna signal switching control circuit 36 'will be described. Only the processing method will be described.

FIG. 25 shows a configuration example of the internal circuit of the new-current FFT window period calculation circuit 40. Antenna signal evaluation circuit 33a
And the correlation signals a and b input from 33b are FFs, respectively.
It is input to the T window period calculation circuits 51a and 51b, and the optimum FFT window period signals a and b for each antenna signal are calculated. The calculated FFT window period signals a and b are input to the current FFT window period calculation circuit 71 and the new FFT window period calculation circuit 72.

Among them, the current FFT window period calculation circuit 71 is simultaneously input with the antenna signal switching control signal of FIG. 10B output from the antenna signal switching control circuit 36 '(FIG. 24). Then, the FFT window period signal of the currently selected antenna signal number, for example, the FFT window period signal a, is selected and output from the current FFT window period calculation circuit 71 as the current FFT window period signal.

On the other hand, in the new FFT window period calculation circuit 72,
The selected antenna signal number output from the antenna signal selection circuit 34 (FIG. 24) is simultaneously input. Then, the FFT window period signal of the antenna signal of the number indicated by the selected antenna signal number, for example, the FFT window period signal b is selected, and the new F
The new FFT window period signal is output from the FT window period calculation circuit 72.

The current FFT window period signal and the new FFT window period signal output from the new current FFT window period calculation circuit 40 of FIG. 24 are the antenna signal switching control circuit together with the selected antenna signal number output from the antenna signal selection circuit 34. 36 '
Entered in.

In the antenna signal switching control circuit 36 ',
Similar to the first embodiment, for example, the antenna signal number b which frequently occurs in the selected antenna signal number is selected. The current FFT window period signal of FIG.
26 (c) obtained by the OR logic of the new FFT window period signal of FIG. 6 (b), for example, the time-delayed F of the current FFT window period signal and the new FFT window period signal except the OR period of FIG. 26 (c).
Immediately after the period of the FT window period signal has ended, FIG.
The code a of the antenna signal previously selected by the antenna signal switching control signal is changed to the code b of the newly selected antenna signal.

At the same time, the antenna signal switching symbol signal illustrated in FIG. 26 (e), which represents the symbol whose antenna signal has been switched, and the FFT window period signal a, which has been selected so far, are replaced with the FFT window period signal of the new antenna signal. The selected FFT window period signal of FIG. 26 (f) changed to b is output from the antenna signal switching control circuit 36 '.

Output from the diversity circuit 30 of FIG. 1 replaced by the diversity circuit 30 of FIG.
Further, the antenna signal switching symbol signal and the selected FFT window period signal output from the diversity adapter 20 are input to the OFDM receiver 60. At this time, the selected FFT window period signal is input to the receiving device 60 instead of the FFT common window period signal.

The FFT signal extraction circuit 66 of the circuit of FIG. 16 showing the internal circuit of the OFDM receiver 60 extracts the signal in accordance with the selected FFT window period signal, and outputs the OFD signal.
FFT is performed in the M signal demodulation circuit 67. Therefore, even if the symbol position suddenly changes as shown in FIG. 27C when the antenna signal is switched, the selected FFT window period signal as shown in FIG. The optimum period is extracted and FFT is performed, and signals of adjacent symbols are not mixed. Therefore, as in the first embodiment, it is possible to always decode a good code without intersymbol interference noise.

In particular, when a circuit for calculating the period during which the inter-symbol interference noise level is minimized is used as the FFT window period calculation circuit, the period position where the inter-symbol interference noise level is minimized for all antenna signals and the individual The position of the period when the inter-symbol interference noise level is minimum as an antenna signal does not necessarily match. Therefore, the inter-symbol interference noise level included in the signal extracted using the FFT common window period signal calculated by this method is higher than the inter-symbol interference noise level included in the signal extracted with the FFT window period signal of each antenna signal. There was a drawback of getting bigger.

However, if this embodiment is applied, no matter which antenna signal is selected, the signal is extracted from the period position where the inter-symbol interference noise level is the minimum, and the FFT is performed. Therefore, the first embodiment It is possible to decode a good code that is less affected by intersymbol interference noise than in the case of.

As described above, when the system is configured using the diversity circuit according to this embodiment, better diversity reception can be realized as compared with the first and second embodiments.

In the above-mentioned diversity circuit, the case where the antenna signal delay circuit 31 or the antenna signal delay circuit 31 'for correcting the time delay due to the evaluation calculation of the reception state is provided has been described.

However, even when diversity reception is carried out, the antenna signals are not switched so frequently. Normally, the switching frequency is once every several hundreds of symbols, and at most once every several tens of symbols.

Therefore, even if the data acquisition time for evaluation and the time at which the antenna signal is actually switched deviate by about one symbol period, there is little effect. Therefore, the antenna signal delay circuit 31 or the antenna signal delay circuit 31 'is not always necessary. In addition, the antenna signal delay circuit 31
Alternatively, if the antenna signal delay circuit 31 'is not provided,
On the contrary, the effect of reducing the circuit scale can be obtained.

Further, when the antenna signal switching circuit 38 'is configured by a circuit for inputting a baseband signal as shown in FIG. 19, the delay which the G correlation calculating circuit 41 (FIG. 11) in the antenna signal evaluation circuit 33 has is delayed. The circuit 3 may be shared as the antenna signal delay circuit 31 ', and the signal output from the delay circuit 3 may be input to the antenna signal switching circuit 38'.

Further, in the above description, the performance of the AGC circuit included in the RF circuit section is high, and the level of the IF signal input to the diversity circuit is sufficiently constant. However, when the performance of this AGC circuit is low and the input IF signal has a level fluctuation, it is desirable to correct the level fluctuation with a digital circuit or the like before inputting it to the antenna signal evaluation circuit.

Further, when the antenna signal evaluation circuit evaluates the antenna signal, it is desirable to make it difficult to select an antenna signal having a large fluctuation by a method of multiplying a weight value by the frequency of fluctuation of the evaluation value. .

Further, as shown in FIG. 28, the antenna signal input terminals 21a, 21b, ... Have a structure in which a cap 82 having a terminating resistor 81 can be mounted, and are left empty to reduce the number of antennas for diversity. It is desirable to attach a cap having a terminating resistor to the existing antenna signal input terminal.

Alternatively, as shown in FIG. 29, terminating resistors 83a, 83b, ... Are provided between the antenna signal input terminals 21a, 21b, ... And the antenna signal delay circuits 31a, 31 ,. Switch 8
It is desirable to provide 4a, 84b, ... And terminate unused antenna signal input terminals with a terminating resistor of the switch. In FIG. 29, the input terminals 21a, 2
Although 1b and the switches 84a and 84b are separated, they are integrated and are terminated by a terminating resistor when the antenna is not attached to the input terminal, and the terminating resistor is released when the antenna is attached to the input terminal to perform signal connection. You may do it.

As a result, it is possible to prevent the selection of the antenna signal from being disturbed by the noise generated in the unconnected input terminal, and to realize stable diversity reception.

Further, instead of inputting the antenna signal evaluation signal calculated by multiplying the peak value of the correlation signal and the power value of the OFDM signal to the antenna signal selection circuit 34, the peak value of the correlation signal and the power of the OFDM signal are input. Be sure to enter the values individually. Then, the power value of the OFDM signal is selected by comparing the power values of the OFDM signals and selecting the antenna signal having a certain level or more, and then selecting the antenna signal having the maximum peak value of the correlation signal of the selected antenna signal. It is also possible to use a peak value of the correlation signal and to provide a two-dimensional fine determination criterion for selection.

Further, the case of using two antennas has been described above. However, when the number of antennas is three or more, it is desirable that the FFT common window period signal calculated by the FFT common window period calculation circuit is the optimum signal acquisition period for the FFT common to all antenna signals. An FFT common to only two antenna signals, the selected antenna signal and the antenna signal newly selected by the OFDM signal selection circuit.
It is also possible to calculate the optimum signal acquisition period for the signal. In this way, when the number of target antenna signals is reduced, it is sufficient to calculate a period common only between antenna signals that are directly affected by antenna switching, so that a better period can be selected. Is obtained.

Further, as shown in FIG. 1, a frequency counter circuit 91 is provided to calculate an antenna selection frequency signal indicating the frequency with which each antenna signal is selected from the selected antenna signal number and the like, and to select the antenna that outputs this signal. A frequency signal output terminal 26 is provided, and the signal output from this output terminal 26 is displayed on a display device such as an oscilloscope, for example, as shown in FIG.
Alternatively, by making it possible to visually observe as shown in FIG. 30 (b), it is possible to realize a diversity receiving device with good usability, which enables actual operation such as grasping an infrequently used antenna and readjusting its direction. Obtainable. In this case, it is desirable that the diversity receiver itself has a built-in display device for easy observation.

The effect of the display indicating the frequency with which each antenna signal is selected is not limited to the OFDM transmission apparatus, but can be applied to a diversity reception apparatus that receives a normal transmission signal with one carrier. , A similar effect can be obtained.

Further, the plurality of delay profiles or the waveforms of the correlation signals are sequentially switched for each sympole period by providing the switch 92 as shown in FIG. 1, and the waveforms having the same positional relationship with the reference signal are simultaneously generated. Alternatively, the output terminal 25 is a signal that can be individually observed and outputs this observable signal.
By providing a signal output from the output terminal 25 with a display device such as an oscilloscope and visually observing the performance of the selected antenna signal while visually observing the signal as shown in FIG. It is possible to obtain a diversity receiving device which can be actually used while confirming the effect and which is easy to use. In this case, it is desirable that the diversity receiver itself has a built-in display device for easy observation. In this case, it is preferable that the FFT common window period can be simultaneously observed as shown in FIG. Alternatively, it is preferable that the delay profile or the correlation signal of the currently selected antenna signal is clearly indicated by a line of a different type such as a line having a color or a thickness different from the others.

As described above, according to the embodiment of the present invention, when the diversity adapter and the OFDM receiver are used,
The effect that diversity reception can always be realized in which the optimum antenna signal for OFDM signal demodulation can be selected is obtained.

Further, regardless of which antenna signal is switched, it is possible to obtain the effect of always realizing diversity reception for demodulating a good code without intersymbol interference noise.

Further, even if the antenna signals are frequently switched, the code error does not increase, and the best antenna signal can always be selected and used.

Compared with the receiver dedicated to diversity,
Diversity reception is possible simply by purchasing a relatively inexpensive diversity adapter, which can significantly reduce the burden on users.

Further, the main body of the receiving device used at the same time becomes small in size, and the effect that it can be used as a normal receiver without any trouble can be obtained.

[0162]

According to the present invention, the above problem is solved by selecting in consideration of the presence of a delayed wave, and the code is always decoded by decoding the RF signal received by the best antenna at that time. It is possible to obtain an information code with few errors,
Moreover, it is possible to obtain a diversity adapter having a diversity circuit in which code errors do not increase even when switching the RF signal to be selected, and an OFDM receiving apparatus and a diversity receiving apparatus for inputting a signal from the diversity adapter. Further, according to the present invention, if a normal reception FPU is owned, it is possible to easily obtain a diversity adapter that enables diversity reception.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration of a diversity receiving system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a carrier structure of an OFDM transmission signal.

FIG. 3 is a diagram showing a structure of an OFDM transmission signal.

FIG. 4 is a diagram showing a circuit configuration of a conventional diversity receiver.

FIG. 5 is a diagram showing a calculation performed by a correlation calculation circuit.

FIG. 6 OFDM in a conventional diversity receiver
It is a figure which shows the circuit structure of a signal selection circuit.

FIG. 7 is a diagram for providing a first description regarding a first problem of the conventional diversity receiver.

FIG. 8 is a diagram for explaining a second problem related to the first problem of the conventional diversity receiver.

FIG. 9 is a diagram for explaining a second problem of the conventional diversity receiver.

FIG. 10 is a diagram for explaining the operation of the diversity circuit in the diversity receiving system according to the first embodiment of the present invention.

FIG. 11 is a diagram showing a circuit configuration of an antenna signal evaluation circuit in the diversity receiving system according to the first embodiment of the present invention.

FIG. 12 is a first antenna signal evaluation circuit in the diversity reception system according to the first embodiment of the present invention.
6 is a diagram for explaining the operation of FIG.

FIG. 13 is a second antenna signal evaluation circuit in the diversity receiving system according to the first embodiment of the present invention.
6 is a diagram for explaining the operation of FIG.

FIG. 14 is a diagram showing a circuit configuration of an FFT common window period calculation circuit in the diversity reception system according to the first embodiment of the present invention.

FIG. 15 is a diagram for explaining the operation of the FFT common window period calculation circuit in the diversity reception system according to the first embodiment of the present invention.

FIG. 16 is a diagram showing an internal configuration of an OFDM receiving apparatus used in the diversity receiving system in the diversity receiving system according to the first embodiment of the present invention.

FIG. 17 is a diagram showing a circuit configuration of a diversity receiving system according to a second embodiment of the present invention.

FIG. 18 is a diagram showing a circuit configuration of a diversity receiving system according to a third embodiment of the present invention.

FIG. 19 is a diagram showing an internal configuration of a diversity circuit in a diversity receiving system according to a fourth embodiment of the present invention.

FIG. 20 is a diagram showing a circuit configuration of a diversity circuit in a diversity receiving system according to a fifth embodiment of the present invention.

FIG. 21 is a diagram illustrating a method of using the diversity receiving system according to the fifth embodiment of the present invention.

FIG. 22 is a diagram for explaining the operation of the diversity circuit in the diversity receiving system according to the fifth embodiment of the present invention.

FIG. 23 is a diagram showing an internal configuration of an FFT common window period calculation circuit in a diversity reception system according to a fifth embodiment of the present invention.

FIG. 24 is a diagram showing an internal configuration of a diversity circuit in a diversity receiving system according to a fifth embodiment of the present invention.

FIG. 25 is a diagram showing a circuit configuration of a new-current FFT window period calculation circuit in the diversity circuit according to the fifth embodiment of the present invention.

FIG. 26 is a diagram for explaining the operation of the antenna signal switching control circuit according to the fifth embodiment of the present invention.

FIG. 27 is a diagram for explaining the operation of the OFDM receiving apparatus in the diversity receiving system according to the fifth embodiment of the present invention.

FIG. 28 is a diagram for explaining the first empty antenna input terminal according to the embodiment of the present invention.

FIG. 29 is a second explanatory diagram of the vacant antenna input terminal in the embodiment of the present invention.

FIG. 30 is a diagram showing a display example of the frequency with which each antenna signal is selected.

FIG. 31 is a diagram showing a display example of a delay profile of each antenna signal or a correlation signal.

[Explanation of symbols]

1a to 1c: antenna, 2a to 2c: receiving circuit, 3, 3
a to 3c: delay circuits, 4, 4a to 4c: correlation calculation circuits,
5: OFDM signal selection circuit, 6: maximum value comparison circuit, 7:
Selector circuit, 8: OFDM signal demodulation circuit, 10a, 1
0b: Antenna, 20, 20 ': Diversity adapter, 21a, 21b, 21'a, 21'b: Input terminal, 22, 22', 23, 24, 25, 26: Output terminal, 30: Diversity circuit, 31a , 31b, 3
1'a, 31'b: Antenna signal delay circuit, 32a, 3
2b: Down converter, 33a, 33b: Antenna signal evaluation circuit, 34: Antenna signal selection circuit, 35: FF
T common window period calculation circuit, 36, 36 ': Antenna signal switching control circuit, 37: Clock pulse generation circuit, 38,
38 ': Antenna signal switching circuit, 39a: Delay circuit,
40: new current FFT window period calculation circuit, 41: G correlation calculation circuit, 42: correlation peak value calculation circuit, 43: OFDM signal power calculation circuit, 44: multiplication circuit, 51, 51a, 51
b: FFT window period calculation circuit, 52: earliest period calculation circuit,
53: adder circuit, 60: OFDM receiver, 60 ': receiver, 62, 63, 64: input terminal, 65: down converter, 66: FFT signal extraction circuit, 67: O
FDM signal demodulation circuit, 68, 68 ': symbol synchronization circuit, 69: Lo synchronization circuit, 70: diversity dedicated O
FDM receiver, 71: Current FFT window period calculation circuit, 7
2: New FFT window period calculation circuit, 81: Terminating resistor, 82:
Caps, 83a, 83b: Terminating resistors, 84a, 84
b: switch, 91: frequency counter circuit, 92: switch.

Claims (17)

[Claims] 1. To receive an OFDM signal, which is an orthogonal frequency division multiplexing modulation method transmission signal for transmitting an information code by a plurality of carriers which are orthogonal to each other, and output it to an OFDM receiving apparatus connected in a subsequent stage. A diversity adapter having a diversity circuit, wherein the diversity circuit inputs a plurality of antenna signal input terminals for inputting a plurality of antenna signals which are signals received by an antenna, and the plurality of antenna signal input terminals. An FFT common window period, which is a signal acquisition period into an FFT that minimizes the inter-symbol interference noise level and is common to OFDM signals included in at least two or more antenna signals among the antenna signals, and calculates the calculated FFT common An FFT common window period calculation circuit for outputting an FFT common window period signal representing a window period; An FFT common window period signal output from the FFT common window period calculation circuit is input, and an antenna signal switching control signal for switching the plurality of antenna signals within a period excluding the FFT common window period or further the plurality of antennas An antenna signal switching control circuit that calculates and outputs an antenna signal switching symbol signal that represents the symbol position of the OFDM signal at the time of switching signals, and the antenna signal switching control signal or further the antenna signal switching symbol signal that is input An antenna signal switching circuit for switching a plurality of antenna signals and outputting a selected antenna signal; an output terminal for outputting the selected antenna signal; and the FFT
A diversity adapter, comprising a diversity circuit having an output terminal for outputting a common window period signal or an output terminal for outputting the antenna signal switching symbol signal. 2. A diversity receiver having a diversity circuit for receiving an OFDM signal which is an orthogonal frequency division multiplexing modulation transmission signal for transmitting an information code by a plurality of carriers orthogonal to each other, the diversity circuit. Is a plurality of antenna signal input terminals for inputting a plurality of antenna signals which are signals received by the antenna, and OFDM included in at least two or more antenna signals among the antenna signals input from the plurality of antenna signal input terminals. An FFT common window for calculating an FFT common window period that is a signal acquisition period into an FFT that is common to signals and has a minimum inter-symbol interference noise level, and outputs an FFT common window period signal representing the calculated FFT common window period. Period calculation circuit and FFT common window period output from the FFT common window period calculation circuit Antenna signal indicating the symbol position of the OFDM signal at the time of switching the plurality of antenna signals, or the antenna signal switching control signal for switching the plurality of antenna signals within a period excluding the FFT common window period. An antenna signal switching control circuit that calculates and outputs a switching symbol signal, and an antenna signal that switches the plurality of input antenna signals according to the antenna signal switching control signal or the antenna signal switching symbol signal and outputs a selection antenna signal A diversity receiver including a switching circuit, wherein the selected antenna signal is demodulated by using the FFT common window period signal or the antenna signal switching symbol signal. 3. To receive an OFDM signal, which is an orthogonal frequency division multiplexing modulation method transmission signal for transmitting an information code by a plurality of carriers (carrier waves) orthogonal to each other, and output it to an OFDM receiving apparatus connected in a subsequent stage. A diversity adapter having a diversity circuit, wherein the diversity circuit compares the input antenna signals with a plurality of antenna signal input terminals for inputting a plurality of antenna signals which are signals received by an antenna. , The level of the transmission signal component included in each antenna signal or its C /
The antenna signal with the highest N value is selected, or the level of the main wave included in each antenna signal or its C / N
Select the antenna signal with the highest value, or select the antenna signal in which the level of the transmission signal component other than the main wave contained in each antenna signal is the smallest with respect to the level of the main wave, and then select the number of the selected antenna signal. A circuit unit that outputs as an antenna signal number, an FF that is optimum for the antenna signal of the selected number, by inputting the plurality of antenna signals and the selected antenna signal number
Calculate the FFT window period, which is the signal acquisition period to T,
A new FFT window period signal representing the calculated FFT window period and a new FFT window period calculation circuit for outputting a current FFT window period signal representing the optimum FFT window period for the antenna signal already selected, and the current FFT window period A signal and the new FFT window period signal are input, and the antenna signal already selected and a new selection are made within a period excluding the period designated by the new FFT window period signal and the period designated by the current FFT window period signal. And a selected FFT window period signal obtained by switching from the current FFT window period signal to the new FFT window period signal at the same time as switching of the antenna signal and an antenna signal switching control signal for switching the antenna signal. Antenna signal that represents the symbol position of the OFDM signal at the time of signal switching Antenna signal switching symbol signal that is calculated and output A signal switching control circuit, an antenna signal switching circuit that switches the plurality of input antenna signals according to the antenna signal switching control signal and the selected FFT window period signal or further the antenna signal switching symbol signal, and outputs a selected antenna signal. An output terminal for outputting the selected antenna signal, and the selection F
A diversity adapter comprising an output terminal for outputting an FT window period signal or an output terminal for further outputting the antenna signal switching symbol signal. 4. A diversity receiver having a diversity circuit for receiving an OFDM signal, which is an orthogonal frequency division multiplex modulation system transmission signal for transmitting an information code by a plurality of carriers orthogonal to each other, the diversity circuit. Compares the input antenna signals with a plurality of antenna signal input terminals for inputting a plurality of antenna signals which are signals received by the antenna, and determines the level of the transmission signal component included in each antenna signal or its C /
The antenna signal with the highest N value is selected, or the level of the main wave included in each antenna signal or its C / N
Select the antenna signal with the highest value, or select the antenna signal in which the level of the transmission signal component other than the main wave contained in each antenna signal is the smallest with respect to the level of the main wave, and then select the number of the selected antenna signal. A circuit unit that outputs as an antenna signal number, an FF that is optimum for the antenna signal of the selected number, by inputting the plurality of antenna signals and the selected antenna signal number
Calculate the FFT window period, which is the signal acquisition period to T,
A new FFT window period signal representing the calculated FFT window period and a new FFT window period calculation circuit for outputting a current FFT window period signal representing the optimum FFT window period for the antenna signal already selected, and the current FFT window period A signal and the new FFT window period signal are input, and the antenna signal already selected and a new selection are made within a period excluding the period designated by the new FFT window period signal and the period designated by the current FFT window period signal. And a selected FFT window period signal obtained by switching from the current FFT window period signal to the new FFT window period signal at the same time as switching of the antenna signal and an antenna signal switching control signal for switching the antenna signal. Antenna signal that represents the symbol position of the OFDM signal at the time of signal switching Antenna signal switching symbol signal that is calculated and output A signal switching control circuit, an antenna signal switching circuit that switches the plurality of input antenna signals according to the antenna signal switching control signal and the selected FFT window period signal or further the antenna signal switching symbol signal, and outputs a selected antenna signal. A diversity receiving apparatus comprising: a demodulation process for demodulating the selected antenna signal using the FFT common window period signal or the antenna signal switching symbol signal. 5. An input terminal for inputting the selected antenna signal output from the diversity adapter according to claim 1, an input terminal for inputting the FFT common window period signal, or the antenna signal switching symbol. An OFDM receiving apparatus comprising: an input terminal for inputting a signal; and means for demodulating the selected antenna signal using the FFT common window period signal or further the antenna signal switching symbol signal. 6. A diversity adapter having a diversity circuit for receiving a transmission signal and outputting it to a receiving device connected to a subsequent stage, wherein the diversity circuit is a plurality of antennas which are signals received by an antenna. A plurality of antenna signal input terminals for inputting signals are compared with the input plurality of antenna signals, and the level of the transmission signal component included in each antenna signal or its C /
The antenna signal with the highest N value is selected, or the level of the main wave included in each antenna signal or its C / N
Selecting the antenna signal having the highest value, or selecting the antenna signal in which the level of the transmission signal component other than the main wave included in each antenna signal is the smallest with respect to the level of the main wave; A diversity adapter, which is a diversity circuit having an output terminal for outputting. 7. The diversity adapter according to claim 1, 3 or 6, wherein the diversity circuit comprises:
A diversity adapter, which outputs a selected antenna signal of the same form as the antenna signal of the first form input to the diversity adapter. 8. The FFT common window period calculation circuit included in the diversity circuit according to claim 1 or 2 is the most advanced among OFDM signals included in all antenna signals input from the plurality of antenna signal input terminals. A diversity adapter characterized by being an FFT common window period calculation circuit for calculating and outputting as a FFT common window period an optimum period for fetching a received signal having an OFDM signal received at the beginning as the FFT. Diversity receiver. 9. The FFT common window period calculation circuit included in the diversity circuit according to claim 1 or 2 is the earliest of the OFDM signals included in the newly selected antenna signal and the already selected antenna signal. Received by O
A diversity adapter or a diversity receiving apparatus, which is an FFT common window period calculation circuit that calculates and outputs an optimum period as an FFT common window period for capturing a reception signal having an FDM signal as its head in an FFT. 10. The inter-symbol interference noise of the OFDM signal included in all the antenna signals input from the plurality of antenna signal input terminals in the FFT common window period calculation circuit included in the diversity circuit according to claim 1. A diversity adapter or a diversity receiving apparatus, which is an FFT common window period calculation circuit that calculates and outputs a period having the smallest level as an FFT common window period. 11. The inter-symbol interference noise level of the OFDM signal included in the newly selected antenna signal and the already selected antenna signal in the FFT common window period calculation circuit included in the diversity circuit according to claim 1 or 2. Is a FFT common window period calculation circuit that calculates and outputs a period that minimizes as an FFT common window period. 12. The diversity circuit according to any one of claims 1 to 4, wherein the individual antenna signals are input, and transmission signal components included in the antenna signals are input for each component having a constant delay time width. After calculating the first value that increases with the maximum power level in the separation and the second power value that increases with the total power level of the components within the predetermined delay time range, the first value is further calculated. A plurality of antenna signal evaluation circuits for calculating a multiplied value of the second value and outputting as an antenna signal evaluation signal and the plurality of antenna signal evaluation signals are input, and the antenna signal number having the highest evaluation value is selected. A diversity adapter or a diversity circuit, which is a diversity circuit including an antenna signal selection circuit for outputting as a selected antenna signal number. Communication apparatus. 13. The antenna signal evaluation circuit according to claim 12, wherein the correlation signal is calculated by calculating a correlation value between signal portions having the same temporal waveform included in the OFDM signal included in the input antenna signal. Output from the G correlation calculation circuit, and a correlation peak value calculation circuit that inputs the correlation signal output from the G correlation calculation circuit, calculates the peak value of the correlation signal, and outputs the peak value of the correlation signal. OFD for inputting the correlation signal of the OFDM signal and outputting the integrated value of the correlation signal for a predetermined period as the power value of the OFDM signal.
The M signal power calculation circuit, the peak value of the correlation signal output from the correlation peak value calculation circuit, and the power value of the OFDM signal output from the OFDM signal power calculation circuit are input, and the peak value and the power value are input. A diversity adapter or a diversity receiving device, which is an antenna signal evaluation circuit including an evaluation value calculation circuit that outputs a product of the above as an antenna signal evaluation signal. 14. A diversity circuit included in the diversity adapter or the diversity receiver according to claim 1, further comprising a delay circuit for delaying some antenna signals more than other antenna signals. A diversity adapter or a diversity receiving device, which is a diversity circuit. 15. The diversity adapter or diversity receiving device according to claim 1, wherein the antenna signal input terminal is equipped with a cap having a terminating resistor when an antenna signal is not input. A diversity adapter or a diversity receiving device, which has a structure capable of connecting to a terminating resistor when not in use. 16. The diversity adapter or diversity receiving apparatus according to claim 12, wherein the frequency of selecting each antenna signal number is calculated from the selected antenna signal number output from the antenna signal selection circuit. A diversity adapter comprising an antenna selection frequency signal and an antenna selection frequency signal output terminal for outputting the antenna selection frequency signal to the outside of the device, or a display section for displaying the antenna selection frequency signal. Or diversity receiver. 17. The diversity adapter or diversity receiving device according to claim 1, wherein the level of a transmission signal component or an OFDM signal component included in each antenna signal has a fixed delay time width. A plurality of delay profiles obtained by separating each component or a plurality of correlation signal waveforms calculated from an OFDM signal included in each antenna signal are simultaneously or simultaneously used as waveforms having the same positional relationship with respect to a reference signal. It has an output terminal that outputs individually observable signals, or the waveforms of the plurality of delay profiles or the plurality of correlation signals can be observed simultaneously or individually as waveforms having the same positional relationship with respect to the reference signal. With a display, or
At the same time as the delay profile or the waveform of the correlation signal, the F
An output terminal that outputs a signal that can be observed during the FT common window period,
Alternatively, it has a display section for observing the FFT common window period, or further, an output terminal for outputting a signal that clearly shows the waveform of the delay profile or the correlation signal calculated from the selected antenna signal, or the selected terminal. A diversity adapter or diversity characterized by having a display section that clearly shows the delay profile calculated from the antenna signal or the waveform of the correlation signal with a line of a different color from the others, such as a line of a different color or thickness. Receiver.