JPH02295257A - Transmitter - Google Patents

Abstract

PURPOSE:To eliminate disturbance to other adjacent communication paths by attenuating a carrier which is inputted from a local oscillator to a frequency converter in the absence of an input and increasing the output level of the local oscillator which is inputted to the frequency converter in the presence of the input. CONSTITUTION:When there is no input to a terminal 1, the attenuation of a variable attenuator(VAR ATT) 9 is increased and the output of the local oscillator 3 is attenuated and inputted to the frequency converter (MIX) 2, so the input level of an amplifier 5 is also lowered. When a signal is inputted to the terminal 1, the attenuation quantity of the VAR ATT9 is decreased gradually and the input level of the carrier from the local oscillator 3 to the MIX2, therefore, increases gradually, so that the input level of the amplifier 5 also increases gradually. Consequently, disturbance to other adjacent communication paths is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmitting device, and particularly to a transmitting device for a digital wireless communication system.

[Conventional technology]

Conventionally, this type of transmitter has a terminal 1 as shown in FIG.
A frequency converter (hereinafter referred to as MIX) 2 converts the intermediate frequency band modulation A3 input from the local oscillator 3 into R
Frequency mixing with F band carrier wave, then band pass
After filter (hereinafter referred to as BPF) passes only the signal to be transmitted and attenuates unnecessary waves (carrier wave and signal output on the opposite side of the carrier wave), the output level is automatically controlled so that the output level is constant. It was amplified to the output level specified in 5.

[Problem to be solved by the invention]

In the conventional transmitter described above, when there is no input to the amplifier 5, the automatic level control function of the amplifier 5 controls the amplifier 5 to the maximum gain state, so the carrier leakage is output more than during normal operation. It has the disadvantage of interfering with other communications.

Also, when a signal is input from terminal 1, the output of amplifier 5 will be higher than the specified level due to the transient response characteristics of the automatic level control function (see Figure 5).
Distortion causes the transmission spectrum to widen, which has the disadvantage of interfering with other adjacent communications.

[Means to solve the problem]

A transmitting device of the present invention includes a frequency converter that converts an intermediate frequency signal input from a modulator into a high frequency band, a local oscillator, and a control signal that controls the level of a carrier wave input from the local oscillator to the frequency converter. a variable attenuator that changes the input signal from the modulator; an automatic level control amplifier that amplifies the required signal in the high frequency band outputted by the frequency converter to a predetermined output level; and a detector that detects the input signal from the modulator. , a comparator for determining whether or not a signal is input from the modulator based on the output of the detector, and a comparator for gradually changing the amount of attenuation of the variable attenuator based on the input voltage from the comparator. and a time constant circuit that outputs a control signal.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an example of the present invention, and FIG. 2(a) to (
f) is a diagram showing changes in voltage or level at points Δ to F in FIG. 1.

When the terminal 1 has no input, the detected voltage of the detector 6 is low, so the comparator (hereinafter referred to as COMP) 7 and the time constant circuit 8
The variable attenuator (hereinafter referred to as MAR AT
The control voltage to VAR ATT
9 increases, the output of the local oscillator 3 is attenuated and input to the MIX 2. Therefore, the input level of the amplifier 5, including the input level of carrier wave leak from the local oscillator 5, is equal to that of the conventional transmitter. As a result, the output level of the amplifier 5 can also be lowered.

When a signal is input to terminal 1 (Fig. 2 (a)), the detection voltage of tester 6 becomes high, and the output voltage of COMP 7 (second
(b)) passes through the time constant circuit 8, the output voltage of the time constant circuit 8, that is, the control voltage to VARATT9 is gradually applied as shown in FIG. 2(C), so VAR AT
The attenuator of T9 is gradually reduced. Along with this, M.I.
The input level of the carrier wave from the local oscillator 3 to X2 gradually increases (FIG. 2(d)), and the input level of the amplifier 5 also gradually increases as shown in FIG. 2(e). Since the time constant of the automatic level control function of the amplifier 5 is faster than the time constant of this increase, the output level of the amplifier 5 reaches a steady state without exceeding the specified output level, as shown in Figure 2 (f). reach Further, the gain of the amplifier 5 changes as shown in FIG.

〔Effect of the invention〕

As explained above, the present invention detects the input of an intermediate frequency signal to the frequency converter using a detector, and when there is no input, attenuates the carrier wave input from the local oscillator to the frequency converter. By suppressing the input level of the oscillator, interference with other communication channels due to carrier wave leakage when no input is present is suppressed, and when a signal is input, the local oscillator output level input to the frequency converter is gradually increased. This has the effect of suppressing the output level of the automatic level control amplifier 2g to the current output level, suppressing the spread of the spectrum due to distortion, and preventing interference with other adjacent communication channels.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2(a)
~(f) are diagrams showing changes in voltage or level at points A to F in Figure 1, Figure 3 is a diagram showing changes in the gain of the amplifier 5 in Figure 1, and Figure 4 is a diagram showing changes in the gain of the amplifier 5 in Figure 1. An example block diagram, FIG. 5, is a diagram showing changes in the output level of the amplifier 5 in FIG. 4. 1... Input terminal, 2... Frequency converter (MIX), 3... Local oscillator, 4...
...Band bus filter (BPF), 5...
...Amplifier, 6...Detector, 7...
Comparator (COMP), time constant circuit, 9.
...Variable attenuator (VAR ATT). Agent Patent Attorney Shinsan Uchihara 2 Miwa 11

Claims (1)

[Claims] A frequency converter that converts an intermediate frequency signal input from a modulator into a high frequency band, a local oscillator, and a variable attenuator that changes the level of a carrier wave input from the local oscillator to the frequency converter under control of a control signal. , an automatic level control amplifier that amplifies the desired signal in the high frequency band outputted by the frequency converter to a predetermined output level, a detector that detects the input signal from the modulator, and an output of the detector. a comparator for determining whether a signal is input from the modulator; and a time constant for outputting the control signal for gradually changing the amount of attenuation of the variable attenuator based on the input voltage from the comparator. A transmitting device characterized by comprising a circuit.