JP5487146B2 - Digital microwave radio transmission apparatus and signal transmission method - Google Patents

Description

  Embodiments described herein relate generally to a digital microwave radio transmission apparatus that employs, for example, a digital multilevel modulation method and a signal transmission method thereof.

  A digital microwave radio communication system is used as one of relay transmission apparatuses that transmit monitoring control information for observing the water level of a dam from a remote location to and from a monitoring center. In this type of relay transmission device, in addition to raw data such as real-time video data and water level observation values that are monitoring control information, and a signal (referred to as a main signal) including remote control data of the observation device, the relay transmission device A signal (referred to as an auxiliary signal) used for applications such as voice meetings related to maintenance operation and remote control is transmitted through the relay radio link. The auxiliary signal is an analog signal in the order of several KHz in the baseband, and is a dedicated channel (Service Channel (Service Channel) provided in a part of, for example, the 6.5 GHz band / 7.5 GHz band (M / N band) of the wireless relay link. : SC)).

  The service channel is multiplexed onto the main signal. The multiplexing system is roughly divided into an encoding multiplexing system in which auxiliary signals are digitally encoded and multiplexed (inserted) into the main signal system, and a carrier wave of the main signal is subjected to FM (Frequency Modulation) modulation shallowly by the auxiliary signal and transmitted. There are two types of FM modulation. Among these, the FM modulation method has an advantage that the auxiliary signal can be transmitted without expanding the bandwidth of the transmission spectrum as compared with the coding multiplexing method.

JP-A-6-53925

In the conventional system that multiplexes the auxiliary signal with the main signal by the FM modulation method, the modulation part in the transmission apparatus is composed of an analog circuit. For this reason, the circuit scale tends to be large. Also, the auxiliary signal is transmitted through a wiring system separate from the digital main signal system from the time when it is input to the transmission device to the time of the FM modulation circuit. For this reason, interface circuits (buffers, etc.) and cables between sections are required across a plurality of systems, and this also increases the circuit scale.
An object of the present invention is to provide a digital microwave radio transmission apparatus and a signal transmission method that are reduced in scale.

  According to the embodiment, the digital microwave radio transmission apparatus includes an interface unit, an analog / digital conversion unit, a multiplexing unit, a transmission unit, a separation unit, an FM modulation unit, a digital modulation unit, a transmission unit, It comprises. The interface unit takes in the digital main signal and the analog auxiliary signal. The analog / digital conversion unit digitizes the auxiliary signal. The multiplexing unit multiplexes the main signal and the auxiliary signal in the digital domain to generate a multiplexed signal. The transmission unit transmits multiple signals. The separation unit separates the main signal and the auxiliary signal from the multiplexed signal transmitted through the transmission unit. The FM modulation unit generates a modulation signal by performing FM (Frequency Modulation) modulation in the digital domain based on the separated auxiliary signal. The digital modulation unit digitally modulates the modulation signal to generate a transmission signal. The transmission unit wirelessly transmits a transmission signal.

1 is a functional block diagram showing a digital microwave radio transmission apparatus according to a first embodiment. The figure which shows the format of the multiple signal frame transmitted via the transmission part 40 shown by FIG. The figure which shows the existing digital transmitter for a comparison. The functional block diagram which shows the digital microwave radio transmission apparatus concerning 2nd Embodiment. The functional block diagram which shows the digital microwave radio | wireless transmitter connected to FIG.

[First Embodiment]
FIG. 1 is a functional block diagram showing a digital microwave radio transmission apparatus according to the first embodiment. In FIG. 1, a digital main signal output from an information processing device or photographing equipment (not shown) is interface-processed by the interface unit 10 and taken into the device and input to a TDM (Time Division Multiplexing) unit 30. An analog auxiliary signal is also taken into the apparatus through interface processing by the interface unit 10, converted into digital data by an analog / digital converter (A / D) 20, and input to the TDM unit 30.

  The TDM unit 30 inserts the auxiliary signal into the main signal in the digital domain, that is, digitally multiplexes the main signal and the auxiliary signal, and baseband (B / B) time division having a multiple signal frame format as shown in FIG. Multiple signals are generated. This time division multiplexed signal is transmitted to the modulation unit 50 via the transmission cable 40 inside the apparatus.

  The time division multiplexed signal is digitally modulated by the modulation unit 50 by a method such as QPSK (Quadrature Phase Shift Keying), and is converted into an IF (Intermediate Frequency) signal in the 140 MHz band by the first local signal L1 from the reference oscillator 60, for example. Up-converted. This IF signal is converted into an analog signal by a digital / analog (D / A) converter 70, and then converted into an RF (Radio Frequency) signal of, for example, 6 GHz band by a second local signal L2 from a reference oscillator 60 by a multiplier 80. Further up-conversion. This RF signal is amplified to transmission power by the power amplifier 90 and then wirelessly transmitted via the antenna 100.

  FIG. 3 is a diagram showing an existing digital transmitter for comparison. In FIG. 3, only the digital main signal is digitally modulated by the main signal modulation unit 150 by, for example, the QPSK method and further up-converted to an IF signal of 140 MHz. This IF digital modulation signal is up-converted by the second local signal from the reference oscillator 60 to the RF frequency of the transmission band by the multiplier 80.

On the other hand, the analog auxiliary signal is converted by the VCO (Voltage Controlled Oscillator) 160 into a signal that transitions in a range of ± 10 KHz, and then input to the FM multiplex modulation unit 170 and multiplied with the RF digital modulation signal. As a result, a transmission signal further subjected to FM modulation is generated. The transmission signal is amplified to the transmission power by the power amplifier 90 and then wirelessly transmitted via the antenna 100.
Such a conventional configuration requires a transmission system for the main signal and a transmission system for the auxiliary signal from the interface unit 10 to the modulation processing system. Therefore, the routing of the cable inside the apparatus becomes complicated, which may cause an increase in noise.

  On the other hand, in the first embodiment, the main signal and the auxiliary signal are digitally multiplexed and transmitted inside the apparatus, so that the space required for routing the wiring can be reduced, and thus the size of the apparatus can be reduced. It becomes possible to promote the conversion. Furthermore, noise resistance can be improved. Therefore, it is possible to provide a digital microwave radio transmission apparatus and a signal transmission method that are reduced in scale.

[Second Embodiment]
4 and 5 are functional block diagrams showing a digital microwave radio transmission apparatus according to the second embodiment. 4, parts common to FIG. 1 are given the same reference numerals, and only different parts will be described here. In FIG. 4, the baseband time division multiplexed signal output from the TDM unit 30 is transmitted to the separation unit 120 via the transmission unit 110. The separation unit 120 again separates the auxiliary signal (denoted as auxiliary signal A) and the main signal (denoted as main signal B) from the time division multiplexed signal.

  FIG. 5 is a functional block diagram showing a digital microwave radio transmission apparatus following the portion shown in FIG. FIG. 5 shows functional blocks after the separation unit 120. In FIG. 5, the auxiliary signal A is input to the I / Q conversion circuit 131, and the main signal B is input to the I / Q conversion circuit 132, which are individually orthogonally modulated. The generated I signal and Q signal are subjected to complex multiplication with each other in the multiplier 140, and a baseband (B / B) FM modulated signal is output.

  This FM modulation signal is modulated by a modulation unit 50 by a method such as QPSK (Quadrature Phase Shift Keying), and is up-converted to an IF (Intermediate Frequency) signal in the 140 MHz band by the first local signal from the reference oscillator 60, for example. Is done. This IF signal is converted into an analog signal by a digital / analog (D / A) converter 70, and then multiplied by a second local signal from a reference oscillator 60 by a multiplier 80, for example, 6 GHz band RF (Radio Frequency) ) The signal is further up-converted. The RF signal is amplified to transmission power by the power amplifier 90 and then transmitted through the antenna 100.

  In the second embodiment, the main signal and the auxiliary signal are digitally multiplexed, transmitted inside the apparatus, separated again, and after being subjected to I / Q conversion, input to an FM modulation circuit (such as the multiplier 140). The FM modulation circuit performs FM modulation with the auxiliary signal on the main signal by digital calculation in the baseband (I, Q). This FM modulation signal is further digitally modulated and transmitted by radio.

  As described above, since the FM modulation processing is performed in the digital domain, most of the circuit can be digitized. For example, integration can be promoted by using an FPGA (Field Programmable Gate Array). . As a result, in addition to the effects of the first embodiment, further downsizing of the transmission device can be promoted.

  In addition, since the main signal and the auxiliary signal multiplexed in the apparatus are separated again and subjected to FM modulation, the bit rate of the signal to be digitally modulated can be reduced, and therefore the first implementation. In addition to the effect of the form, it is possible to suppress the spread of the band of the transmission signal. Therefore, a great merit can be obtained in a situation where the available transmission band is limited in the wireless section.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Interface part, 20 ... Analog / digital converter, 30 ... TDM part, 40 ... Transmission cable, 50 ... Modulation part, 60 ... Reference oscillator, 70 ... Digital / analog converter, 80 ... Multiplier, 90 ... Power amplifier , 100 ... antenna, 110 ... transmission unit, 120 ... separation unit, 131,132 ... I / Q conversion circuit, 140 ... multiplier, 150 ... main signal modulation unit, 160 ... VCO (voltage controlled oscillator), 170 ... FM multiplexing Modulator

Claims (2)

An interface unit for capturing a digital main signal and an analog auxiliary signal;
An analog / digital converter for digitizing the auxiliary signal;
A multiplexing unit that multiplexes the main signal and the digitized auxiliary signal in a digital domain to generate a multiplexed signal;
A transmission unit for transmitting the multiplexed signal;
A separation unit for separating the main signal and the auxiliary signal from the multiplexed signal transmitted through the transmission unit;
An FM modulation unit that generates a modulation signal by performing FM (Frequency Modulation) modulation on the separated main signal in the digital domain based on the separated auxiliary signal;
A digital modulator that digitally modulates the modulated signal to generate a transmission signal;
A digital microwave radio transmission apparatus comprising: a transmission unit that wirelessly transmits the transmission signal. A signal transmission method in a digital microwave radio transmission apparatus, comprising:
Interfacing digital main signal and analog auxiliary signal,
Digitize the auxiliary signal;
Multiplexing the main signal and the digitized auxiliary signal in the digital domain to generate a multiplexed signal;
Transmitting the multiplexed signal inside the digital microwave radio transmitter;
Separating the main signal and the auxiliary signal from the transmitted multiplexed signal;
The separated main signal is subjected to FM (Frequency Modulation) modulation in the digital domain based on the separated auxiliary signal to generate a modulated signal;
Digitally modulating the modulated signal to generate a transmission signal;
A signal transmission method for wirelessly transmitting the transmission signal.

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