JPH025044B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ALC circuit, and more particularly to an ALC circuit that changes the time constant of an ALC voltage according to the radio wave type of high-frequency transmission power.

[Conventional technology]

Normally, the ALC circuit consists of the transmission final stage 6 shown in Figure 1.
It is installed in the transmitting circuit of wireless communication equipment, etc. to protect the equipment. The transmitting circuit includes a transmitting device 1, a pre-stage transmitting circuit 4,
It is composed of a variable gain amplifier 5, a transmission final stage section 6, and an antenna 7. The transmission signals output from the telephone key 2 (including the automatic transmission device), microphone 3, etc. of the transmitting device 1 are configured so that the high frequency transmission power of the radio wave type corresponding to the operation mode selected with the mode selection dial 13 can be transmitted from the antenna 7. Waveform processing such as amplification, modulation, and band selection is performed in the pre-transmission path 4. A transmission output control circuit such as a variable gain amplifier 5 outputs a transmission signal subjected to waveform processing to a transmission final stage section 6. The transmission final stage unit 6 generates high-frequency transmission power from the input transmission signal and radiates it into the air from the antenna 7 as a radio wave. This radio wave type has attributes related to modulation type (amplitude, phase, pulse, etc.) and transmission type (telegraph, telephone, video, facsimile, etc.). AM, FM, SSB (upper sideband or lower sideband) is used in amateur radio. Frequency shift keying using CW, FSK (SSB, AM, etc.) i.e. audio FSK...
AFSK), etc. In addition, the vacuum tube or semiconductor provided in the transmission final stage 6 has unique operating characteristics, and appropriate measures must be taken to ensure that there is no distortion at the maximum signal level and to increase the information energy transmitted during normal times. be. Furthermore, the probability of the presence of a signal appearing is different between the voice signal (analog waveform) and the telephone key signal (digital waveform), especially in SSB where the carrier wave is not radiated in the radio wave when there is no signal, the carrier wave appears in the transmission final stage 6 by the ALC voltage generation circuit 9. The overlevel detection time, that is, the ALC voltage rise time,
The ALC voltage generated by the ALC voltage generation circuit 9 suppresses the gain of the variable gain amplifier 5, etc., and the time required until the overlevel is released and the original state is restored.
ALC voltage hold time is an important factor in ensuring proper continuous transmission. In addition, the transmission final stage section 6
In order to operate efficiently, controlled circuits such as a variable gain amplifier 5 controlled by the ALC voltage are provided at each stage, and the level distribution in each stage is designed to be appropriate during normal times and at the start of the ALC. Reference numeral 12 in the figure is a drive control volume, and this drive control volume 12
may be provided between the ALC circuit 8 and the transmission final stage section 6. In addition, a microphone gain volume (including an automatic microphone gain control circuit) and the like are provided in order to control the high frequency transmission power of the transmission final stage section 6.

[Problem to be solved by the invention]

At the transmitter, the modulated signal is an analog waveform.
For SSB signals, the design conditions for ALC voltage holding time are more complex than for other radio wave formats. Therefore, the time constant of the conventional ALC circuit 6 is determined to be compatible with SSB. For this reason, AFSK using SSB has drawbacks such as the appearance probability of a signal being different from that of an audio signal and extremely poor responsiveness. Furthermore, FSK using the FM method has the disadvantage that a non-negligible filter ripple occurs due to the difference between the mark frequency and the space frequency (usually 170 Hz to 850 Hz) and the filter loss for each frequency passing through the bandpass filter.

The present invention has been made in view of the above-mentioned points, and is an ALC that can obtain an ALC voltage compatible with radio wave formats.
The purpose is to provide circuits.

[Means to solve the problem]

It has variable gain amplification means, ALC voltage generation means for controlling the variable gain amplification means, and transmission mode selection means. It is set by a time constant circuit including a resistor element, and when the ALC generating means detects an output level exceeding the allowable value in the time constant circuit, an ALC signal is outputted and input to the time constant circuit, and the ALC level and time constant are set. This is a configuration that allows the .

〔Example〕

An embodiment of the ALC circuit of the present invention will be explained based on FIG.

In the figure, 17 is a variable resistance element control dial. The variable resistance element control dial 17 is formed by a rotary switch, and when the mode selection dial 13 is rotated, a new contact P _a and child contacts P ₁ to _{P 5} are activated (for the sake of explanation, the number of child contacts is assumed to be 5). comes into contact. Control voltages _V1 to _V5 generated by the voltage divider 18 are applied to the child contacts _P1 to _P5 , respectively. Also, the parent contact P _a
is connected to the terminal 15c of the ALC circuit 15.

The ALC circuit 15 includes an ALC voltage generation circuit 16, a field effect transistor _Q1 , and a transistor _Q2 . The ALC voltage generation circuit 16 has a comparison voltage for comparing whether or not the detection signal output from the transmission final stage section 6 has exceeded a certain level, and has a comparison voltage that compares whether the detection signal output from the transmission final stage section 6, 12, the detection signal is inputted via the Y'-Y connection and the terminal 15a. When the input detection signal reaches a level higher than the comparison power, an ALC voltage is generated and output to the base of transistor _Q2 .

The field effect transistor _Q1 is a voltage-controlled variable resistance element, and the resistance between the drain and source changes depending on the gate voltage. The gate is connected to the terminal 15c, and the control voltages V ₁ to V ₅ generated by the voltage divider 18 are inputted via the child contacts P ₁ to P ₅ and the parent contact P _a .
The source is a resistor R ₂ whose time constant is determined, and a capacitor C ₁
is connected to the reference potential point via. Also, the connection point between resistor R ₂ and capacitor C ₁ is a transistor
The collector of Q ₂ is connected to the terminal 15b, and a resistor R ₁ is provided between this connection point and the drain. This resistance R ₁ is a field effect transistor Q ₁
It has a much larger resistance value than the series resistance value consisting of the variable resistance value of R2 and the resistor _R2 . In addition, resistance
The drain bias voltage V _B is determined by R ₄ and R ₃ .

Here, child terminals P ₁ to _{P 5} are configured to correspond to SSB (audio), FM (audio, code), AM (audio), SSB (code), and AM (code), and the mode selection dial 13 selects FSK. When you select , the master contact P _a and slave contact P ₂ of the variable resistance element control dial 17 are connected, and the control voltage corresponding to SSB (audio) is applied to the terminal 15 c.
A control voltage V ₂ at a higher level than V ₁ is applied.
Normally, the detection signal outputted from the transmission final stage section 6 to the terminal 15a of the ALC circuit 15 is at a lower level than the comparison voltage of the ALC voltage generation circuit 16, so the transistor _Q2 is inactive. Therefore, the terminal 15b has the same potential as the bias voltage _VB .

When the ALC voltage is generated, transistor Q ₂ becomes active and the charge on capacitor C ₁ is transferred to the transistor
It is discharged through the collector and emitter of _Q2 , and the terminal 15b becomes a reference potential point. When the ALC start level is released and the ALC voltage becomes zero, transistor _Q2 becomes inactive and the emitter and collector are cut off.

For this purpose, the capacitor C ₁ is charged by a series resistor consisting of the drain and source of the field effect transistor Q ₁ and the resistor R ₂ . Since the series resistance at this time depends on the control voltage V ₂ applied to the gate, the base voltage is higher and the series resistance is lower than in the case of the control voltage V ₁ corresponding to SSB (audio). Therefore, the time constant consisting of capacitor C ₁ and low series resistance is smaller than for SSB (audio), and the capacitor
The time it takes for the terminal 5b to rise from the reference potential point to the potential of the base bias _VB after the charging of _C1 is completed is shortened. Therefore, the ALC voltage at the terminal 15b can follow the output voltage at the FSK mark and space, and filter ripples due to filter loss can be removed.

Control voltage V ₁ of variable resistance element control dial 17
The assignment of ~ _V5 is not limited to the above embodiment, and for example, the same control voltage _V2 may be used for FM (voice, code), SSB (code), and AM (code).

Control voltage by variable resistance element control dial 17
Switching between V ₁ and _{V 5} may be performed from the mode control circuit 14 via a semiconductor switch circuit or the like.

The variable resistance element is not limited to a voltage control type such as a field effect transistor, but may be a current control type formed by a normal transistor or the like.

〔Effect of the invention〕

The ALC circuit according to the present invention has a configuration that includes a variable resistance element whose resistance value changes in response to the selection operation by the mode selection means and a variable time constant circuit, so that the time constant can be changed in response to the mode selection operation. have. Therefore, compared to a system in which a plurality of time constant circuits are provided corresponding to the mode selection dials, the number of parts can be reduced.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional ALC circuit, Figure 2 is a block diagram of a conventional ALC circuit.
The figure is a block diagram showing one embodiment of an ALC circuit according to the present invention. 1... Transmitting device, 2... Telephone key, 3... Microphone,
4... Pre-stage transmission circuit, 5... Variable gain amplifier, 6... Transmission final stage section, 7... Antenna, 8, 15... ALC circuit,
9, 16...ALC voltage generation circuit, 10...Time constant circuit, 11...Operation panel, 12...Drive control volume, 13...Mode selection dial, 1
4...Mode control circuit, 17...Variable resistance element control dial, _C1 ...Capacitor, R1 to _R4 ... _Resistor , _Q1 ...
Field effect transistor, _Q2 ...transistor.

Claims (1)

[Claims] 1. Equipped with variable gain amplification means, ALC voltage generation means for outputting an ALC voltage for controlling the gain of the variable gain amplification means, and mode selection means for selecting the radio wave format of high frequency power output from the transmission final stage section. and an ALC circuit related to a transmitting circuit configured to control the gain of the variable gain amplifying means according to the ALC voltage and protect the transmitting final stage section,
comprising: a variable resistance element whose resistance value changes in response to a selection operation by the mode selection means; and a variable time constant circuit whose time constant changes depending on the resistance value of the variable resistance element; An ALC circuit characterized in that it is configured to output an ALC voltage to variable gain amplification means.