JP2008092487A - Signal generating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small and lightweight signal generating apparatus which is conveniently carried, and to provide a small and lightweight signal generating apparatus which can be used as an OFDM signal generator and is conveniently carried. <P>SOLUTION: The signal generating apparatus 1 is provided with a D/A converter 4 which converts radio signals in a low-frequency zone read out from a hard disk 2 into analog signals, a frequency conversion part 5 which converts the analog signals converted by the D/A converter 4 into high-frequency signals. Radio signals in a low-frequency zone which are obtained by converting OFDM signals in an IF zone or a UHF zone used for terrestrial digital television broadcasting into low-frequency signals (digital OFDM signals whose center frequency is 5 MHz and whose bandwidth is 5.7 MHz, for example) are previously stored in the hard disk 2 in the signal generating apparatus 1. OFDM signals in the IF zone or the UHF zone are output as inspection signals by using the stored radio signals in the low-frequency zone as a signal source. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a signal generator used for measuring / inspecting a broadcast wave repeater in a relay broadcasting station for digital terrestrial television broadcasting.

  Currently, the expansion and construction of digital terrestrial television networks are rapidly progressing toward the end of analog television broadcasting in 2011. In particular, the rush to establish a digital terrestrial television broadcasting station in recent years.

  At digital terrestrial television broadcasting stations, the Ministry of Internal Affairs and Communications inspects whether radio equipment such as broadcast wave relay equipment complies with the Radio Law when it is newly established and in operation. become.

  Some of the measuring instruments used for these inspections can be used at the time of analog television inspection, but a measuring instrument specific to digital terrestrial television broadcasting is also required.

  In particular, the OFDM signal generator is an indispensable measuring instrument for inspection of digital terrestrial television broadcasting, and generates various signals modulated by the OFDM modulation method at frequencies of UHF band and IF band (37.15 MHz). . An OFDM modulator is generally used as the OFDM signal generator.

Also known is a digital broadcast wave signal recording apparatus capable of simultaneously recording and reproducing a plurality of television programs while maintaining the radio wave format (see, for example, Patent Document 1). This signal recording apparatus includes frequency conversion means for frequency-converting a broadcast signal into a low-frequency signal, A / D conversion means for A / D-converting a broadcast signal frequency-converted to a low frequency, and A / D-converted. Data storage means for storing data. When reproducing data stored in a data storage means such as an HDD, the channel and time are designated, and the desired channel and time data are extracted from the recorded data, and the D / A converter is And convert it into a frequency band of a desired channel. Watch this signal on TV.
JP 2006-94078 A

  By the way, the OFDM signal generator used for the measurement and inspection of the broadcast wave repeater in the digital terrestrial television broadcasting station is only the OFDM modulator.

  This OFDM modulator is very expensive, large and heavy. When a terrestrial digital television relay broadcasting station is newly established, broadcast wave signals (radio waves) used for inspection of radio equipment such as a broadcast wave relay device may not yet be output. Even in such a case, the inspection cannot be performed without actually inputting a signal. In that case, it is very difficult to bring a large and heavy OFDM modulator to the broadcast station to be inspected. Even when a radio equipment such as a broadcast wave repeater is regularly inspected during operation, it is very difficult to bring a large and heavy OFDM modulator to each relay broadcast station to be inspected. Therefore, there is a demand for a light and small signal generator that can be used as an OFDM signal generator.

  Further, the signal recording apparatus described in Patent Document 1 stores a television program at the same time in a data storage means such as an HDD while maintaining the radio wave format, and when reproducing the stored data, the channel and time , The desired channel and time data are extracted from the recorded data, output via the D / A converter, and converted into the frequency band of the desired channel. Watch this signal on TV. As described above, this signal recording apparatus is a recording / reproducing apparatus for recording a television program while maintaining the radio wave format and reproducing the recorded data.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a light-weight and small-sized signal generator that is convenient to carry.

  Another object of the present invention is to provide a lightweight and small signal generator that can be used as an OFDM signal generator and is easy to carry.

  In order to solve the above-mentioned problem, the invention according to claim 1 includes a storage unit that stores a low-frequency band radio signal, a signal readout unit that reads the low-frequency band radio signal from the storage unit, D / A conversion means for converting the radio wave signal read from the storage means into an analog signal, and frequency conversion means for converting the analog signal converted by the D / A conversion means into a high-frequency signal, The gist is to output a high-frequency signal converted by the frequency conversion means as a radio wave signal for inspection.

  According to a second aspect of the present invention, in the signal generator according to the first aspect, the low frequency band radio signal stored in the storage means is an IF band OFDM signal or UHF signal used for terrestrial digital television broadcasting. A low-frequency digital OFDM signal obtained by frequency-converting a band OFDM signal into a low-frequency band signal that can be easily stored in the storage means, and the frequency conversion means reads out from the storage means and uses the D / A conversion means. The gist is to convert a low-frequency analog OFDM signal that has been D / A converted into a high-frequency signal, and to output the OFDM signal in the IF band or the OFDM signal in the UHF band as the radio wave signal for inspection.

  Here, the “OFDM signal” is a broadcast wave signal conforming to an ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) system obtained by converting a broadcast TS (Transport Stream) signal obtained by converting video / audio or the like into a digital signal.

  An OFDM (Orthogonal Frequency Division Multiplexing) signal in the IF (Intermediate Frequency) band is generated by an OFDM modulator that performs transmission path coding and OFDM (Orthogonal Frequency Division Multiplexing) modulation on a broadcast TS (Transport Stream) signal. An intermediate frequency signal of 15 MHz. For example, in this OFDM signal, there are a large number of (carrier wave: subcarrier) in a broadcast wave having a bandwidth of 5.7 MHz, and a digital signal is carried on each carrier wave. An OFDM signal in the UHF (Ultra High Frequency) band is a signal of about 470 to 770 MHz generated by frequency-converting an OFDM signal in the IF band generated by the OFDM modulator.

  According to a third aspect of the present invention, in the signal generating device according to the second aspect, the signal reading means includes a central processing unit that controls reading of the radio signal from the storage means and a main memory, and is externally provided. When a signal output command is input, under the control of the central processing unit, the low frequency band radio signal stored in the storage means is read from the storage means to the main memory and the D / A conversion means It is output to

  According to a fourth aspect of the present invention, there is provided the signal generating device according to the third aspect, wherein at least one hard disk is provided as the storage means.

  According to a fifth aspect of the present invention, in the signal generation device according to any one of the second to fourth aspects, the frequency conversion unit includes a local oscillation circuit that generates a desired local oscillation signal, and the storage unit. A mixer that multiplies the low-frequency analog OFDM signal read out and D / A-converted by the D / A conversion means by the local oscillation signal output from the local transmitter, and outputs a difference signal between the frequencies of both signals; And a filter that cuts out noise and extracts only a signal in a necessary band.

  According to a sixth aspect of the present invention, in the signal generation device according to the fifth aspect, the frequency converting means further causes the output signal of the filter to operate a broadcast wave relay device of a relay broadcast station for digital terrestrial television broadcasting. The gist is to provide an amplifying means for amplifying the electric power.

  According to a seventh aspect of the present invention, in the signal generating device according to the second aspect, the signal reading unit includes a central processing unit that controls reading of the radio signal from the storage unit, and a main memory, The gist is that the processing device, the main memory, the storage means, the D / A conversion means, and the frequency conversion means are accommodated in one package.

  The gist of an eighth aspect of the present invention is that in the signal generator according to the seventh aspect, at least one hard disk is provided as the storage means.

(Function)
According to the first aspect of the present invention, the inspection radio signal can be generated and output using the low frequency band radio signal stored in the storage means as a signal source. For this reason, a modulator or the like is not required. In addition, since the configuration is simpler and smaller than such a modulator, a light and small signal generator that is convenient to carry can be obtained.

  According to the second aspect of the present invention, the low frequency digital OFDM signal stored in the storage means can be used as a signal source to generate and output an IF band OFDM signal or a UHF band OFDM signal. It can be used as an OFDM signal generator, and an OFDM modulator that generates and outputs an OFDM signal becomes unnecessary. In addition, since the configuration is simpler and smaller than the OFDM modulator, a lightweight and small signal generator that is convenient to carry can be obtained.

  In addition, it is not necessary to prepare an expensive OFDM modulator when measuring and inspecting a broadcast wave repeater that receives and retransmits a broadcast wave, and carries a large and heavy OFDM modulator to a digital television relay broadcasting station. There is no need.

  According to the invention described in claim 3, when a signal output command is input from the outside, the radio signal in the low frequency band stored in the storage means is read from the storage means to the main memory under the control of the central processing unit. Can be output to the D / A conversion means.

  According to the fourth aspect of the invention, by using at least one hard disk as the storage means, it is possible to store digital data for inspection with a large amount of information in the hard disk.

  According to the fifth aspect of the present invention, it is possible to generate and output a high-quality inspection radio signal without noise. Thereby, highly reliable measurement and inspection can be performed on the broadcast wave relay device.

  According to the sixth aspect of the present invention, since the output signal of the filter is amplified to a power that can be transmitted as a broadcast wave signal for terrestrial digital television broadcasting by the amplifying means, the radio wave signal for inspection output from the filter is It can be used for measurement and inspection of broadcast wave repeater at a relay broadcast station.

  According to the seventh aspect of the present invention, since all functions of the signal generator are provided in one personal computer, it is possible to realize a signal generator that is easier to carry.

  According to the eighth aspect of the invention, a radio signal having a large amount of information can be stored in the hard disk.

An embodiment embodying the present invention will be described with reference to the drawings. In the present embodiment, a signal generator used for measurement and inspection of a broadcast wave relay apparatus in a relay broadcasting station for digital terrestrial television broadcasting will be described.
(One embodiment)
FIG. 1 shows a schematic configuration of a signal generator 1 according to the present embodiment.

  The signal generator 1 includes a hard disk (HDD) 2 as a storage means in which a low-frequency radio signal is stored, and a notebook personal computer (signal reading means for reading out a low-frequency radio signal from the hard disk 2). (Hereinafter referred to as “notebook personal computer”) 3. One or a plurality of hard disks 2 are provided.

  The signal generator 1 is converted by a D / A converter 4 as a D / A converter that converts a low-frequency radio signal read from the hard disk 2 into an analog signal, and the D / A converter 4. And a frequency conversion unit 5 as frequency conversion means for converting an analog signal into a high frequency signal.

  The low-frequency radio signal stored in the hard disk 2 is a low-frequency (several MHz) signal that is easy to store in the hard disk 2 the above-mentioned IF band OFDM signal or UHF band OFDM signal used for terrestrial digital television broadcasting. This is a low-frequency digital OFDM signal that has been frequency-converted to. In this example, the radio signal in the low frequency band is, for example, a digital OFDM signal having a center frequency of 5 MHz and a bandwidth of 5.7 MHz.

  The notebook personal computer 3 is a personal computer including a CPU (Central Processing Unit) 10, a main memory RAM 11, a PCI bus 12, and the like. A hard disk 2 is mounted on the notebook personal computer 3.

  When a signal output command is input from the outside by operating a keyboard (not shown) of the notebook personal computer 3, the signal generator 1 receives a low frequency band radio signal stored in the hard disk 2 under the control of the CPU 10. Are read out from the RAM 11 and transmitted to the D / A converter 4 via the PCI bus 12. The D / A converter 4 is supplied with a 20 MHz reference signal so as to perform D / A conversion at a sampling frequency of 20 MHz.

  The frequency converter 5 converts the low-frequency analog OFDM signal D / A converted by the D / A converter 4 to a signal having the same high frequency as the inspection radio signal used for the inspection of the broadcast wave repeater (IF band or UHF band). OFDM signal).

  The frequency converter 5 includes a local oscillator circuit 20 that generates a desired local signal, a low-frequency analog OFDM signal that is D / A converted by the D / A converter 4, and a local oscillator that is output from the local transmitter 20. And a mixer (DBM) 30 that outputs a difference signal of the frequency of both signals, and a bandpass filter (BPF) that cuts out noise and extracts only a signal in a necessary band. ) 31 and an operational amplifier (OP Amp) 32.

  The mixer 30 includes four diodes. Both signals are obtained by multiplying the low frequency analog OFDM signal read from the hard disk 2 and D / A converted by the D / A converter 4 by the local signal (local output) output from the local transmitter 20. This is a passive mixer that outputs a difference signal between the two frequencies. The mixer 30 is set to output a difference signal with little frequency fluctuation.

  A local oscillation circuit 20 for generating a desired local oscillation signal is composed of a frequency synthesizer circuit using a PLL circuit (Phase Locked Loop) 22 including a voltage controlled oscillator (VCO) 21 and the like, and is controlled from the outside. Based on this, two types of local oscillation signals having different frequencies are generated.

  One local oscillation signal (IF local oscillation signal) is a signal of the first frequency fL1 for generating and outputting an IF band OFDM signal. The first frequency fL1 is a 37.15 MHz signal as a frequency difference signal from the frequency (center frequency) f1 (in this example, f1 = 5 MHz) of the low-frequency analog OFDM signal output from the D / A converter 4. Are set to be output from the mixer 30. At this time, the first frequency fL1 is 42.15 MHz.

  When such a local oscillation signal of the first frequency fL1 (fL1 = 42.15 MHz) is output from the local oscillation circuit 20 to the mixer 30, the output signal of the mixer 30 includes a 37.15 MHz signal, 42.15. A (37.15 + 5) MHz signal and other frequency signals are included.

  The other local oscillation signal (UHF local oscillation signal) is a signal of the second frequency fL2 for generating and outputting an UHF band OFDM signal. The second frequency fL2 is set so that, for example, a signal of 500 MHz is output from the mixer 30 as a frequency difference signal from the frequency f1 (5 MHz) of the low-frequency analog OFDM signal output from the D / A converter 4. Is done. At this time, the second frequency fL2 is 505 MHz.

  When such a local oscillation signal of the first frequency fL2 (fL2 = 505 MHz) is output from the local oscillation circuit 20 to the mixer 30, the output signal of the mixer 30 includes a 500 MHz signal and a 510 (505 + 5) MHz signal. , And other frequency signals.

  Furthermore, in the present embodiment, a changeover switch 23 for outputting a local oscillation signal having the third frequency fL3 to the mixer 30 is provided. When the selector switch 23 is switched from the position indicated by the solid line in FIG. 1 to the position indicated by the alternate long and short dash line, a local oscillation signal having the third frequency fL3 is output to the mixer 30.

  Further, the local oscillation circuit 20 is set to output a local oscillation signal in which ripple and phase noise are suppressed in any of the above two types of local oscillation signals.

  The mixer 30 includes four diodes. Both signals are obtained by multiplying the low frequency analog OFDM signal read from the hard disk 2 and D / A converted by the D / A converter 4 by the local signal (local output) output from the local transmitter 20. This is a passive mixer that outputs a difference signal between the two frequencies. The mixer 30 is configured to output the difference signal with little frequency fluctuation.

  The band pass filter 31 is a filter that cuts out noise from the difference signal output from the mixer 30 and extracts only a signal in a necessary band. The bandpass filter 31 is composed of, for example, a SAW (Surface Acoustic Wave) filter.

  The operational amplifier 32 is for amplifying the output signal of the band-pass filter 31 to the power for operating the radio equipment (such as a broadcast wave repeater) in a relay broadcasting station for digital terrestrial television broadcasting. An IF band or UHF band OFDM signal amplified by the operational amplifier 32 is output from the output terminal 33 as a test signal.

  In the signal generator 1 having the above-described configuration, a low-frequency radio signal (a center frequency is 5 MHz and a bandwidth is reduced) obtained by converting an IF band or UHF band OFDM signal used for digital terrestrial television broadcasting into a low-frequency signal. 5.7 MHz digital OFDM signal) is stored in the hard disk 2 in advance. The stored low frequency band radio signal can be used as a signal source, and an IF band or UHF band OFDM signal can be output as a test signal.

  In the present embodiment, the signal generator 1 provided with the notebook personal computer 3 as the signal reading means has been described. However, the signal generator 1 has a minimum required function of the general notebook personal computer 3, for example, the CPU 10. RAM 11, PCI bus 12, operation switch (not shown) for giving a signal output command to the CPU 10, etc. In this case, the CPU 10, RAM 11, PCI bus 12, CPU 10, the operation switch, the D / A converter 4 and the like are mounted on a mother board (not shown), and the frequency converter 5 and the local oscillator 20 are separately installed. The signal generator 1 is configured by mounting on a substrate and storing them in one package. With such a configuration, it is possible to realize a lightweight and small-sized signal generator 1 that is convenient to carry.

According to this embodiment, the following effects can be obtained.
○ Generate and output an IF band or UHF band OFDM signal using a low-frequency radio signal stored in the hard disk 2 (digital OFDM signal having a center frequency of 5 MHz and a bandwidth of 5.7 MHz) as a signal source Can be used as an OFDM signal generator. This eliminates the need for an OFDM modulator that generates and outputs an OFDM signal.
○ Since the configuration is simple and small compared to the OFDM modulator, a lightweight and small signal generator that is convenient to carry can be obtained.
Since the configuration is simpler than that of an OFDM modulator, it is possible to realize a signal generator that is less expensive than the OFDM modulator.
○ When measuring and inspecting broadcast wave repeaters that receive and retransmit broadcast waves, it is not necessary to prepare expensive OFDM modulators and to carry large and heavy OFDM modulators to digital television relay stations There is no.
○ By operating the operation switch (not shown) and inputting a signal output command to the CPU 10, the low-frequency radio signal stored in the hard disk 2 can be read out to the RAM 11 and output to the D / A converter 4. it can.
Since one or a plurality of hard disks 2 are provided, digital data for inspection with a large amount of information can be stored in the hard disk 2.
The local oscillation circuit 20 generates two types of local oscillation signals having different frequencies based on external control. Thereby, since the low frequency OFDM signal obtained by converting the IF band or UHF band OFDM signal into the low frequency signal is stored in the hard disk 2, when outputting the IF band or OFDM signal as the inspection signal, An IF local oscillation signal is generated. Further, when outputting a UHF band OFDM signal, a UHF band OFDM signal can be generated to output a UHF band OFDM signal as a test signal.
○ The local oscillation circuit 20 is configured to output a local oscillation signal in which ripple and phase noise are suppressed in both cases of the two types of local oscillation signals, so that a high quality inspection signal is generated and output. can do.
○ Using the inspection signal (radio wave), the output level of the signal (radio wave) used to inspect whether the radio equipment of the broadcast relay station complies with the Radio Law, and the inspection of the radio wave quality, etc. is somewhat high It is necessary to amplify it to a level at which the radio equipment of the broadcast relay station is operated. If the output level is not increased to that level, it cannot be used for inspection of broadcast stations. In the present embodiment, the operational amplifier 32 amplifies the output signal of the bandpass filter 31 to the power for operating the radio equipment (such as a broadcast wave relay device) of a relay broadcasting station for digital terrestrial television broadcasting. A band or UHF band OFDM signal can be used effectively as an inspection signal for inspection of a broadcast relay station.
(Measurement and inspection methods for broadcast wave relay equipment)
Next, a method of performing measurement and inspection of a broadcast wave relay device at a relay broadcasting station for digital terrestrial television broadcasting using the signal generator 1 described in the above embodiment will be described with reference to FIG.

  In the broadcast wave repeater 40 shown in FIG. 2, the master station OFDM modulated signal transmitted from the reception antenna is input to the input filter A, and the broadcast signal band of one channel among the terrestrial digital television broadcast channels included in this input signal. Only pass through the input filter A and the unwanted waves are attenuated. The OFDM-modulated signal that has passed through the input filter A is converted into an IF-band OFDM signal by the reception conversion circuit B to which the local-station signal is input from the first local-station G. After being converted by the transmission conversion circuit C to which the local oscillation signal is input from the generation H, the power amplification unit D amplifies the signal to a predetermined power. The amplified OFDM signal has its noise removed by the output filter E, and is output as a broadcast wave signal (radio wave) F to the transmission antenna or pseudo antenna.

When the signal generator 1 described in the above embodiment outputs a UHF band OFDM signal as a test signal, the signal generator 1 measures and inspects the broadcast wave repeater 40 by inputting the OFDM signal to the input filter A. I do. When the signal generator 1 outputs an OFDM signal in the IF band as a test signal, the signal generator 1 inputs the OFDM signal to the transmission conversion circuit C and performs measurement / inspection of the broadcast wave relay device 40.
(OFDM signal recording and playback system)
Next, an OFDM signal recording / reproducing system for recording an IF band or UHF band OFDM signal as a low-frequency radio signal on the hard disk 2 of the signal generator 1 described in the above embodiment will be described with reference to FIG. explain.

  This OFDM signal recording / reproducing system includes the signal generating device (OFDM signal generating circuit) 1 described in the above embodiment and a signal recording unit (master unit) 50 as a signal reproducing unit (slave unit).

  The signal recording unit 50 includes a frequency conversion unit (DOWN.CON) 51, a local transmitter 52, and a stationary personal computer 53.

  The frequency converter 51 selects a required channel from either the UHF band OFDM signal that is a UHF terrestrial digital radio wave or the IF (37.15 MHz) band OFDM signal that is an output signal of the OFDM modulator. Record signal.

  The selected recording signal is converted by the frequency converter 51 into a signal having a frequency of several MHz (low frequency OFDM signal) that can be easily recorded on the hard disk of the stationary personal computer 53. The converted signal is sent to a stationary personal computer 53 having a large-capacity hard disk.

  This input signal is an analog signal of several MHz, and this signal is converted into a digital signal through a high-speed A / D converter (not shown) in the stationary personal computer 53, and this converted digital signal is converted into the stationary personal computer 53. It is to be recorded on the hard disk. Note that a 20 MHz reference signal obtained by converting a 10 MHz reference signal into a double frequency by the binary multiplication circuit 54 is input to the A / D converter (not shown) of the stationary personal computer 53. .

  The digitized OFDM signal recorded on the hard disk of the stationary personal computer 53 is read from the hard disk and output from the signal recording unit 50 to the signal generating device (signal reproducing unit) 1. This digital signal is taken into the hard disk 2 of the notebook computer 3 and recorded.

In addition, this invention can also be changed and embodied as follows.
In the above embodiment, the configuration using at least one hard disk 2 as the storage means has been described. However, as the storage means, DRAM (Dynamic Random Access Memory), EEPROM (Electronically Erasable and Programmable Read Only Memory), SRAM ( Various semiconductor memories such as Static Random Access Memory may be used.
In the above embodiment, the signal output command is input from the outside by operating the keyboard (not shown) of the notebook computer 3, but an operation switch is provided, and the signal is output by operating the operation switch. The present invention is also applicable to a configuration in which a command is input and a low-frequency band radio signal stored in the hard disk 2 is read from the hard disk 2 to the RAM 11 under the control of the CPU 10.
In the above embodiment, a signal generator that can be used as an OFDM signal generator that generates OFDM signals used for inspection of radio wave quality and radio equipment periodically performed at the time of new establishment and operation at a digital terrestrial broadcast station However, the present invention is not limited to this. The present invention is also applicable to the following various signal generators.
As a digital signal modulation method, an orthogonal frequency division multiplexing (OFDM) method is adopted for terrestrial digital broadcasting, a TC8PSK modulation method is used for satellite broadcasting, and a 64QAM modulation method is used for cable television. The present invention can be widely applied to a signal generator that generates a signal obtained by modulating a digital signal using these modulation methods.
Specifically, the present invention is applicable to the following various application examples.
(Application 1)
The signal generator 1 described in the above embodiment can be used as a propagation tester for confirmation of a radio wave service area, confirmation of interference, and the like.

This radio wave testing machine is used to test how strong the radio waves are in that area and what radio waves are emitted in which direction and which service can be provided most efficiently. In such a case, it is best to examine it on the desk at first, but it is best to finally test it by sending out a test radio wave. It can be used for a signal generator that emits radio waves for inspection from a certain point.
(Application example 2)
The signal generator 1 can be used as a test signal source for a new underground shopping center or wireless hearing.
(Application 3)
When building a ubiquitous network of home appliances by comprehensive connection of wireless networks such as IT products, refrigerators, air conditioning equipment, security equipment, etc., which will develop in the future, radio waves from individual wireless terminals of home appliances from different manufacturers It is necessary to confirm whether or not they can be interconnected together. Therefore, it seems that each household needs to be simulated. Therefore, the wireless terminal signal of each manufacturer is stored as a low frequency band radio signal in the storage means of the signal generator 1 described in the above embodiment, for example, a hard disk, and the radio wave for inspection is installed from the installation location of each product. The signal generator 1 can be used as a signal source for transmitting a signal and confirming that it is securely connected to the control terminal.
(Application 4)
Wireless LAN propagation confirmation, wireless LAN also has a radio wave format of OFDM, various frequency transmission speeds, and the signal generator 1 can be used as a propagation test signal generator between rooms and between offices before introduction. .

1 is a block diagram showing a schematic configuration of a signal generator according to an embodiment of the present invention. The block diagram which shows a broadcast wave relay apparatus for the measurement and test | inspection using the signal generator 1 which concerns on one Embodiment. 1 is a block diagram showing a schematic configuration of an OFDM signal recording / reproducing system for recording a low-frequency band radio signal on a hard disk of a signal generator according to an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Signal generation device, 2 ... Hard disk, 3 ... Notebook-type personal computer, 4 ... D / A converter, 5 ... Frequency conversion part, 10 ... CPU (central processing unit), 11 ... RAM (main memory), 12 ... PCI bus, 20 ... Local transmitter, 21 ... Voltage control transmitter, 22 ... PLL circuit, 23 ... Switch, 30 ... Mixer, 31 ... Bandpass filter, 32 ... Operational amplifier, 33 ... Output terminal.

Claims (8)

Storage means for storing low-frequency radio signals;
Signal readout means for reading out the radio signal of the low frequency band from the storage means;
D / A conversion means for converting the radio wave signal read from the storage means into an analog signal;
Frequency conversion means for converting the analog signal converted by the D / A conversion means into a high-frequency signal,
A signal generation apparatus characterized in that a high-frequency signal converted by the frequency conversion means is output as a radio wave signal for inspection. The low frequency band radio signal stored in the storage means is an IF band OFDM signal or UHF band OFDM signal used for digital terrestrial television broadcasting. It is a converted low frequency digital OFDM signal,
The frequency conversion means converts the low-frequency analog OFDM signal read from the storage means and D / A converted by the D / A conversion means into a high-frequency signal, and then converts the IF band OFDM signal or UHF band OFDM signal The signal generator according to claim 1, wherein a signal is output as the radio wave signal for inspection. The signal reading means includes a central processing unit that controls reading of the radio signal from the storage means and a main memory,
When a signal output command is input from the outside, the low frequency band radio signal stored in the storage means is read from the storage means to the main memory under the control of the central processing unit, and the D / A The signal generator according to claim 2, wherein the signal generator is output to the conversion means.   4. The signal generator according to claim 3, wherein at least one hard disk is provided as the storage means. The frequency conversion means includes
A local oscillation circuit for generating a desired local oscillation signal;
The low frequency analog OFDM signal read from the storage means and D / A converted by the D / A conversion means is multiplied by the local oscillation signal output from the local transmitter, and a difference signal between the frequencies of both signals is output. A mixer to
The signal generator according to claim 2, further comprising a filter that cuts out noise and extracts only a signal in a necessary band.   6. The signal according to claim 5, wherein the frequency converting means further comprises an amplifying means for amplifying the output signal of the filter up to power for operating a broadcast wave relay device of a relay broadcasting station for digital terrestrial television broadcasting. Generator. The signal reading means includes a central processing unit that controls reading of the radio signal from the storage means and a main memory,
3. The signal generator according to claim 2, wherein the central processing unit, the main memory, the storage unit, the D / A conversion unit, and the frequency conversion unit are accommodated in one package.   8. The signal generator according to claim 7, wherein at least one hard disk is provided as the storage means.

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