JPH0457411A - Transmission output control circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a method (radio wave format I (3E, etc. The present invention relates to a transmission output control circuit for an amplitude modulation transmitter (such as when generating radio waves), and particularly relates to a transmission output control circuit for an amplitude modulation transmitter that can stabilize transmission output.

(Prior Art) A conventional carrier-added amplitude modulation transmitter uses a transmission power control circuit as shown in the block diagram of FIG.

The configuration of a conventional carrier-added amplitude modulation transmitter will be described with reference to FIG.

When a low frequency signal given from a microphone or the like is input to the low frequency amplifier 1, it is amplified to a required level. On the other hand, when a signal that becomes a carrier wave of the transmission output is generated from the carrier wave generator 4 and the signal and the signal amplified by the low frequency amplifier 1 are input to the balanced modulator 2, the balanced modulator 2 suppresses the amplitude of the carrier wave. Generates a modulated wave. In the modulated wave spectrum of the amplitude modulated wave generated as a result of modulation, there are two sidebands (an upper sideband and a lower sideband) above and below the carrier frequency. This amplitude modulated wave is input to the band limiting filter 3 to obtain the required amplitude modulated wave from either the upper sideband or the lower sideband.

The amplitude modulated wave that has passed through the band-limiting filter 3 is input to a modulated wave variable gain amplifier 5, and the carrier wave output from the carrier wave generator 4 is input to a carrier wave variable gain amplifier 9.

The output from the modulated wave variable gain amplifier 5 and the output from the carrier wave variable gain amplifier 9 are combined, and the combined signal is amplified to a predetermined value by the power amplifier 6 and output as a transmission output.

Then, the following output control is performed on the amplitude modulated transmission output by a transmission output control circuit.

That is, an average value detector 7 that detects the average value of the transmission output and a peak detector 8 that detects the peak value of the transmission output are separately provided before being output as the transmission output. Then, the output from the average value detector 7 is transferred to a carrier wave variable gain amplifier 9.
is input to control the output from the carrier variable gain amplifier 9 to maintain the carrier power of the transmission output at a constant value. Further, the output from the peak detector 8 is transmitted to the modulated wave variable gain amplifier 5.
By manually controlling the modulation wave variable gain amplifier 5 for the modulation component and controlling the power of the modulation wave component to a predetermined value or less, the carrier wave speed is 100% in the chevron amplitude modulation.
Measures have been taken to prevent over-modulation when the modulation depth exceeds %. As explained above, the average value detector 7,
The peak detector 8, the modulated wave variable gain amplifier 5, the carrier wave variable gain amplifier 9, and the power amplifier 6 constitute a transmission output control circuit.

(Problems to be Solved by the Invention) However, the transmission output control circuit in the conventional carrier-added amplitude modulation transmitter has the following problems.

The first problem is that in conventional carrier-added amplitude modulation transmitters, since two high-frequency detectors, the average value detector 7 and the peak detector 8, are connected to the transmission output, the impedance of the original transmission output changes, which adversely affects high frequency matching.

The second problem is that, although diodes are generally used in the above-mentioned high-frequency detector, two high-frequency detectors, the average value detector 7 and the peak detector 8, each have separate diodes. , the linearity and gain of the detection output will fluctuate greatly due to variations in diode characteristics, etc.
This means that it is necessary to adjust the balance between the control circuits of the two high-frequency detectors.

The third problem is that the radio wave format H3E single signal 1 is shown in Figure 8.
To explain by showing the transmission output voltage waveform at 00% modulation,
When the peak voltage at 100% modulation is set to 1, the average value of this transmission output voltage waveform is expressed as follows.

2/rr J'■ (Sin X) d

On the other hand, the voltage of the carrier wave is half of the peak voltage, which is 0.
．． It is 5.

The average value detector 7 that detects the carrier voltage detects a voltage equivalent to the average value of the transmitted output voltage waveform, so especially under conditions with a high degree of modulation such as when H3E single signal 100% modulation is performed. , a voltage approximately 26% higher than the carrier wave voltage will be detected, and the carrier wave variable gain amplifier 9 will be controlled by the high voltage to suppress the carrier wave voltage, conversely reducing the transmission output voltage and causing it to fluctuate. It was supposed to happen.

Further, the reason why the average value detector 7 is used in this way is that it is extremely difficult to detect a carrier wave by detecting a high frequency wave.

The present invention has been made in view of the above circumstances, and solves the problem of impedance matching brought about by providing a plurality of detectors in a transmission output circuit, and the problem of balance adjustment of input and output characteristics due to the diode characteristics of the detector. Transmission output control that realizes carrier wave detection, which could not be achieved with a high-frequency detector, and can perform transmission output control by separating and detecting the voltages required for two types of gain control from the output of one high-frequency detector. The purpose is to provide circuits.

(Means for Solving the Problem) The present invention, which is intended to solve the problems of the conventional example described above, performs envelope detection of the transmission output in a transmitting horn control circuit of a carrier-added single sideband modulation transmitter. an envelope detector, a carrier detection circuit that removes a modulation component from the envelope detection output to extract a carrier control voltage, a carrier variable gain amplifier that performs gain control on the carrier component using the carrier control voltage, and the envelope detection circuit. It is characterized by comprising a peak detection circuit that extracts a voltage corresponding to the peak voltage from the output, and a modulated wave variable gain amplifier that performs gain control on a modulation component using the voltage corresponding to the peak voltage.

(Function) According to the present invention, the transmission output control circuit in a carrier-added single sideband modulation transmitter detects the envelope of the transmission output with an envelope detector, and uses the carrier detection circuit from the detected output. The carrier wave control voltage is extracted using the carrier wave control voltage, and the gain control for the carrier wave component is performed using the carrier wave control voltage. Also, the voltage corresponding to the peak voltage is extracted using the peak detection circuit from the detection output of the envelope, and the gain for the modulated wave component is determined using this voltage. Since the control circuit is designed to perform control, only one detector is required, so the effect on the impedance of the transmission output is small, and there is no need for balance adjustment between two conventional detectors, and the envelope curve is By treating the transmitted output as a low-frequency signal in a wave detector, it is possible to separate the carrier wave component into a DC component and the modulated wave component into an AC component.
A faithful carrier wave detection circuit can be realized.

(Example) An example of the present invention will be described with reference to the drawings.

FIG. 1 is a transmission output control circuit diagram of an amplitude modulation transmitter according to an embodiment of the present invention. Regarding the transmission output control circuit of this embodiment, parts having the same configuration as in FIG. 2 are given the same reference numerals.

A low frequency signal given from a microphone or the like is input to a low frequency amplifier 1 and amplified to a required level.

On the other hand, when a signal that becomes a carrier wave of the transmission output is generated from the carrier wave generator 4 and the signal and the signal amplified by the low frequency amplifier 1 are input to the balanced modulator 2, the balanced modulator 2 suppresses the amplitude of the carrier wave. Generates a modulated wave. In the modulated wave spectrum of the amplitude modulated wave generated as a result of modulation, there are two sidebands (an upper sideband and a lower sideband) above and below the carrier frequency.

This amplitude modulated wave is input to the band-limiting filter 3 to obtain the required amplitude modulated wave from either the upper sideband or the lower sideband.

The amplitude modulated wave that has passed through the band-limiting filter 3 is input to the modulated wave variable gain amplifier 5, and the carrier wave output from the carrier wave generator 4 is inputted to the carrier wave variable gain amplifier 9.

The modulated wave variable gain amplifier 5 and the carrier wave variable gain amplifier 9 are
As will be described later, the detected output from the envelope detector 14 is processed by a peak detection circuit 15 and a carrier detection circuit 16, and is controlled by the respective processed output voltages.

The output from the modulated wave variable gain amplifier 5 and the output from the carrier wave variable gain amplifier 9 are combined, and the combined signal is amplified to a predetermined value by the power amplifier 6 and output as a transmission output.

However, as a feature of this embodiment, before the transmission output is output from the power amplifier 6, a general envelope detector 4 is provided for determining the envelope voltage of the high frequency signal of the transmission output. Then, the output from the envelope detector 14 is input to the carrier detection circuit 16, the carrier wave component in the transmission output, that is, only the DC component is extracted by the carrier wave detection circuit 16, and this signal is input to the carrier wave variable gain amplifier 9. Then, the output of the variable carrier gain amplifier 9 is controlled to maintain the carrier power of the transmission output at a constant value.

On the other hand, the output from the envelope detector 14 is similarly input to the pic detection circuit 15 to obtain a voltage corresponding to the peak voltage of the transmission output, and this voltage is input to the modulated wave variable gain amplifier 5 to generate the modulated wave variable gain amplifier 5. By controlling the modulated wave variable gain amplifier 5 for each purpose to control the power of the modulated wave component to a predetermined value or less, overmodulation in carrier wave sending type amplitude modulation is prevented.

Here, the purpose of gain control for the carrier wave is to maintain the carrier wave at a constant value level, and the purpose of gain control for the modulation guideline is to limit the maximum value so that the transmission output does not exceed a predetermined value. It is a purpose. The carrier wave detection circuit 16 and the peak detection circuit 15 for performing these gain controls will be specifically explained below.

FIG. 2 shows a circuit diagram of a specific example of the carrier wave detection circuit 16. The envelope detection output from the envelope detector 14 is a pulsating flow A shown in the diagram showing the envelope detection output in FIG. 3, and includes a carrier component (DC) a and a modulation component (AC) b. It is something.

In the circuit diagram of FIG. 2, when the envelope detection output is input to the carrier wave detection circuit 16, it is divided into a positive phase amplifier 18 and a capacitor 19 inside the carrier wave detection circuit 16, and then input thereto. In the positive phase amplifier 18, as shown in the diagram showing the positive phase amplifier output in Fig. 4, the carrier wave component (DC)
A pulsating flow B containing a modulation component (alternating current) is output.

The capacitor 19 extracts the modulated component (alternating current) signal from which the direct current component (carrier component) has been removed, and inputs it to the negative phase amplifier 20 having the same gain as the positive phase amplifier 18 . The anti-phase amplifier 20 outputs an AC signal C obtained by inverting the extracted modulation component (alternating current), as shown in FIG. 5, which shows the output of the anti-phase amplifier. and,
The output signal (pulsating current B) from the positive phase amplifier 18 and the output signal (AC C) from the negative phase amplifier 20 are combined and output to the carrier variable gain amplifier 9 as a carrier wave control voltage.

Combining the output signal (pulsating current B) from the positive phase amplifier 18 and the output signal (AC C) from the negative phase amplifier 20 means that the modulation component (AC) is canceled out and the carrier wave component in the transmission output is DC voltage (4th voltage) corresponding to the level of (DC component)
The carrier wave control voltage D) in the figure is taken out and output to the carrier wave variable gain amplifier 9.

Conventionally, the average value detector 7 shown in FIG. 7 has controlled the carrier wave output using a pseudo average value of the transmission output for the carrier wave, but according to the carrier wave detection circuit 16 of this embodiment, the carrier wave output can be controlled faithfully. Because it is possible to obtain a voltage proportional to only the carrier wave output,
By controlling the transmission output using the detection output from the carrier wave detection circuit 16, the carrier wave output can be stably maintained at a constant level.

Next, the peak detection circuit 15 of this embodiment will be explained using the circuit diagram of FIG. 6.

When the envelope detection output from the envelope detector 14 is input to the peak detection circuit 15, inside the peak detection circuit 15, the envelope detection output is first input to the positive phase amplifier 21.
A capacitor 23 is charged from the positive phase amplifier 21 through a diode 22. Charging of the capacitor 23 is instantaneously performed by a charging time constant determined by the forward resistance of the diode 22 and the capacitance of the capacitor 23. On the other hand, by making the discharging time constant sufficiently longer than the charging time constant due to the capacitance of the capacitor 23 and the discharging resistor 24, a DC voltage corresponding to the peak voltage of the transmission output can be obtained.

A DC voltage corresponding to the peak voltage of the transmission output is sent as a modulation control signal to the modulation wave variable gain amplifier 5, and the maximum value is limited in the modulation wave variable gain amplifier 5 so that the transmission output does not exceed a predetermined value. Gain control is performed to achieve this.

The conventional transmission output control circuit shown in FIG. 7 has a configuration in which two high-frequency detectors, an average value detector 7 and a peak detector 8, are connected to the transmission output, and the impedances of these two detectors are connected in parallel. Since the impedance of the transmission output is connected to the transmission output impedance, the impedance of the transmission output was supposed to be greatly affected. However, in the transmission output control circuit of this embodiment, only one high frequency detector is connected to the transmission output. Therefore, the impedance connected in parallel to the impedance of the transmission output can be increased, which has the effect of reducing the influence on the impedance of the transmission output.

Furthermore, conventionally, it was necessary to delicately adjust the balance between two high-frequency detectors, but according to the transmission output control circuit of this embodiment, the envelope detector 14 only has one high-frequency detector. , there is an effect that the adjustment as in the conventional method is not necessary.

Although it is not possible to directly separate the transmission output into a carrier wave component and a modulated wave component, as in this embodiment, the envelope detector 1
By treating the transmission output as a low-frequency signal using 4, it is possible to clearly separate the carrier wave component into a DC component and the modulated wave component into an AC component, making it possible to realize a faithful carrier wave detection circuit. can.

Furthermore, according to this embodiment, the high frequency detection circuit of the high frequency detector generally requires a shield case, etc., but one shield case etc. for the envelope detector 14 is sufficient. This has the effect of making it cheaper.

Furthermore, according to the transmission output control circuit of this embodiment, in the conventional transmission output control circuit using average value detection, the transmission output of the carrier wave when not modulated is 40% when modulated at 100%.
%, but the transmission output control circuit of this embodiment can suppress this variation to 4% or less.

(Effects of the Invention) According to the present invention, the transmission output control circuit in a carrier-added single sideband modulation transmitter is configured by detecting the envelope of the transmission output with an envelope detector, and using the detected output to detect the carrier wave detection circuit. The carrier wave control voltage is extracted using the carrier wave control voltage, and the gain control for the carrier wave component is performed using the carrier wave control voltage.The voltage corresponding to the peak voltage is extracted using the peak detection circuit from the detection output of the envelope, and the voltage corresponding to the peak voltage is extracted from the detected output of the envelope. Since the control circuit is designed to perform gain control on the modulated wave component, only one detector is required, which has the effect of reducing the impact on the impedance of the transmission output, and also reduces the effect on the impedance between two conventional detectors. Since no balance adjustment is required, the configuration can be simplified, and by treating the transmission output as a low-frequency signal using an envelope detector, the carrier wave component can be converted into a DC component, and the modulated wave component can be converted into an AC component. It can be separated into components, which has the effect of realizing a faithful carrier wave detection circuit.

[Brief explanation of the drawing]

Fig. 1 is a configuration block diagram of an amplitude modulation transmitter according to an embodiment of the present invention, Fig. 2 is a carrier wave detection circuit diagram, Fig. 3 is a waveform diagram of envelope detection output, and Fig. 4 is a positive phase amplifier output. Figure 5 is a waveform diagram of inverse I[] amplification output, Figure 6 is a peak detection circuit diagram, Figure 7 is a configuration block diagram of a conventional amplitude modulation transmitter, Figure 8 is H3E 100%. FIG. 3 is a waveform diagram of transmission output during modulation. 21... Positive phase amplifier 22... Diode 23... Capacitor 24... Discharge resistor 1... Low frequency amplifier 2... ...Balanced modulator 3 ...Band limit filter 4 ...
...Carrier wave generator 5...Modulated wave variable gain amplifier 6...
......Power amplifier 7...Average value detector 8...Peak detector 9...Carrier variable gain amplifier 14.・・・
... Envelope detector 15 ... Peak detection circuit 16 ... Carrier wave detection circuit 18 ... Positive phase amplifier 19 ... Capacitor 20 ... ...Reverse-phase amplifier applicant: Kokusai Denki Co., Ltd. Agent Kiyotaka Sakamoto, patent attorney Agent: Nobuhiro Funatsu Figure 3 Figure 2 U Figure 4 Output factor 8 of reverse-phase amplifier

Claims (1)

[Claims] A transmission output control circuit for a carrier-added single-sideband modulation transmitter includes an envelope detector that performs envelope detection of the transmission output, and a carrier wave that removes a modulation component from the envelope detection output. a carrier wave detection circuit that extracts a control voltage; a carrier wave variable gain amplifier that performs gain control on a carrier wave component using the carrier wave control voltage; a peak detection circuit that extracts a voltage corresponding to a peak voltage from the envelope detection output; 1. A transmission output control circuit comprising: a modulated wave variable gain amplifier that performs gain control on a modulated component using a corresponding voltage.