JPH05227232A - Transmission burst waveform control system - Google Patents

Abstract

PURPOSE:To easily revise the setting of leading/trailing characteristic of a transmission burst waveform by controlling a reference voltage of a D/A converter converting a ROM output generating the transmission waveform into an analog value. CONSTITUTION:Transmission data 1 synchronized with a burst signal 8 being a transmission start/stop signal are decoded to an address of a transmission waveform generating ROM 4 by an address decoder circuit 2, a transmission waveform passing through a desired filter characteristic from the ROM 4 is outputted as digital data 5. The data 5 are converted into an analog value at a converter 6 and become a transmission burst signal 7. On the other hand, the signal 8 is formed into a waveform with a desired leading/trailing by a specific constant circuit 9 and the result is fed to a reference voltage of the converter 6. Thus, the leading/trailing characteristic of the transmission burst waveform 7 is formed into a desired characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission burst waveform control system for a digital modulator for wireless communication.

[0002]

2. Description of the Related Art Conventionally, in a modulation system of digital mobile communication, a filter having a roll-off characteristic is generally used in order to eliminate intersymbol interference in generating a transmission waveform, and a high frequency component is dropped to limit a band. .. A digital filter is often used for this roll-off filter. Since this digital filter executes signal processing by multiplication and addition, it is necessary to execute arithmetic processing at high speed. Therefore, there is a problem in reducing power consumption.

To solve this problem, a method is used in which the calculation result is stored in advance in the ROM, the input data is input as the ROM address, and the filter circuit is replaced by the ROM to generate the transmission waveform.

In such a transmission waveform generation system, T
When performing burst-like transmission like DMA communication, the rising / falling edge of the transmission burst waveform is prevented for the purpose of preventing the influence of the steep rising / falling portion of the transmitting burst waveform on the adjacent channel and the spread of the spectrum. Need to be loose. The rising / falling control of the transmission burst waveform is performed by setting the address of the ROM to an address storing a desired rising / falling waveform in advance only when transmission is started / stopped.

As a related publicly known technique, there is JP-A-3-159440.

[0006]

(1) The capacity of the ROM for generating the transmission waveform is reduced.

(2) It is possible to easily change the setting of the rising / falling characteristics of the transmission burst waveform in order to comply with the device specifications.

[0008]

[Means for Solving the Problems] Means for solving the problems according to the present invention will be described below with reference to FIGS.

(1) The rising / falling control of the transmission burst waveform 7 which was performed by the address control of the transmission waveform generation ROM 4 is controlled by the reference voltage of the D / A converter 6 for converting the ROM output into an analog value. By doing. As a result, the number of address bits used in the transmission waveform generation ROM 4 can be reduced and the ROM capacity can be reduced.

(2) The reference voltage signal 1 generated by the reference voltage setting ROM 16 is used to control the reference voltage of the D / A converter 6.
0, the rising / falling characteristics of the transmission burst waveform 7 are set to the reference voltage setting ROM 16
This can be easily done by simply changing the contents of.

[0011]

(1) The rising / falling control of the transmission burst waveform is performed by controlling the reference voltage of the D / A converter for converting the ROM output into an analog value,
The ROM capacity is reduced by reducing the number of address bits used in the transmission waveform generation ROM.

(2) The reference voltage of the D / A converter of (1) above is controlled by a newly provided ROM, and the rise / transmission waveform of the transmission burst waveform can be easily changed only by changing the contents of the new ROM. Set the falling characteristics.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Will be explained.

(1) The transmission data 1 synchronized with the burst signal 8 which is the transmission start / stop signal is decoded by the address decoding circuit 2 into the address of the transmission waveform generation ROM 4, and the desired waveform characteristics are obtained from the transmission waveform generation ROM 4. The transmission waveform that has passed through is output as digital data 5. This digital data 5 is converted into an analog value by the D / A converter 6 and becomes a transmission burst waveform 7.

On the other hand, the burst signal 8 is shaped into a desired rising / falling waveform by the time constant circuit 9 and D /
It is supplied as a reference voltage for the A converter 6. Since the output of the D / A converter 6 is the reference voltage × digital data value,
The maximum value of the output waveform has the same rising / falling characteristic as the reference voltage signal 10. As a result, the rising / falling characteristics of the transmission burst waveform 7 can be set to desired characteristics.

(2) In synchronization with the burst signal 8 which is the start / stop signal of the transmission, the timing control unit 11 outputs the count UP at the start of the transmission and the count DOWN signal 12 at the stop of the transmission, and the desired rising / rising. The count enable signal 13 corresponding to the falling time is input to the address counter 14. The address counter 14 controls the address of the reference voltage setting ROM 16 according to the count UP / DOWN signal 12 and the count enable signal 13.

On the other hand, the reference voltage setting ROM 16 stores digital data in which the waveforms shown in FIG. 2 are quantized for the above addresses. Therefore, the quantized data 17 is output from the reference voltage setting ROM 16 in synchronization with the rising / falling of the burst signal 8, and the quantized data 17 is sent to the D / A converter 18 for the reference voltage of the D / A converter 6. Becomes

[0018]

The present invention has the following effects.

(1) The capacity of the transmission waveform generation ROM can be reduced by controlling the rising / falling of the transmission burst waveform of this control method by controlling the reference voltage of the D / A converter.

(2) By controlling the reference voltage of the D / A converter of this control system by the ROM, it is possible to easily change the setting of the rising / falling characteristics of the transmission burst waveform.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a transmission burst waveform rising characteristic diagram.

FIG. 3 is a configuration diagram showing an embodiment of the present invention.

4 is a timing chart in FIG.

[Explanation of symbols]

1 ... Transmission data, 2 ... Address decoding circuit, 3 ... RO
M address, 4 ... Transmission waveform generation ROM, 5 ... Digital data, 6 ... D / A converter, 7 ... Transmission burst waveform, 8
... Burst signal, 9 ... Time constant circuit, 10 ... Reference voltage signal, 11 ... Timing control unit, 12 ... Count UP / D
OWN, 13 ... Count enable, 14 ... Address counter, 15 ... ROM address, 16 ... Reference voltage setting R
OM, 17 ... Quantized data, 18 ... D / A converter.

Claims (2)

[Claims] 1. A transmission waveform generator for inputting a digital signal and outputting a transmission waveform based on the input signal, comprising a D / A converter for converting a ROM output for generating a transmission waveform into an analog value. A transmission burst waveform control method characterized by controlling the rise / fall of a transmission burst waveform by controlling a reference voltage. 2. A transmission burst waveform control system, wherein the reference voltage of the D / A converter according to claim 1 is controlled by a ROM output waveform.