JPH04321305A - Amplitude modulation transmitter - Google Patents

Abstract

PURPOSE:To modulate a voice input signal with fidelity by adjusting an output voltage of an equal output voltage amplifier and that of a binary voltage amplifier. CONSTITUTION:An output of a 1st power supply 11 is connected to n-sets of equal output voltage amplifiers 11-1n, a binary voltage amplifier 1A and a voltage detector 17 and the voltage detector 17 is formed to extract a voltage divided by, e.g. resistors R1, R2. Moreover, a 2nd power supply 12 supplies a DC power supply whose voltage is 1/4 of a voltage of the 1st power supply 11 to a binary voltage amplifier 1B outputting a voltage of 1/4 of an output voltage of the equal output voltage amplifier and a binary voltage amplifier IC outputting a voltage of 1/8. Then an output voltage is automatically changed in response to a voltage fluctuation detected by the voltage detector 17 and always kept to a 1/4 of the voltage of the 1st power supply 11. Thus, the output voltage ratio of the equal output voltage amplifiers 11-1n and the binary voltage amplifiers 1A, 1B, 1C is made accurately coincident with a prescribed value to modulate the voice input signal with fidelity.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The present invention relates to an amplitude modulation transmitter,
In particular, amplitude modulation involves converting an analog audio signal into a multi-bit signal, and controlling on/off multiple high-frequency amplifiers placed corresponding to the multi-bit signal to generate an amplitude modulated wave. Regarding the transmitter.

0002

2. Description of the Related Art An example of a conventional amplitude modulation transmitter of this type is shown in FIG. This amplitude modulation transmitter includes n equal output voltage amplifiers 11 to 1n, 1/2, 1/4, 1/8
Each binary voltage amplifier 1A, 1B, 1C with an output voltage of
It has a high frequency power amplifier 1 composed of
, 2C, and output through a filter 10. Audio input is input to each amplifier through an A/D converter 15 and a modulation encoder 16, and a carrier signal is input through a high frequency oscillator 13 and a high frequency distributor 14. Furthermore, 1
1 is a first power supply for the equal output voltage amplifiers 11 to 1n and the 1/2 binary voltage amplifier 1A, and 12 is a second power supply for the other binary voltage amplifiers 1B and 1C.

According to this configuration, an input audio signal is converted into a binary multi-bit digital signal by the A/D converter 15 and transmitted to the modulation encoder 16. Modulation encoder 1
6 is a converter that converts into a signal suitable for switching the power amplifier according to the configuration of the high frequency power amplifier 1, and a decimal signal or a binary signal is used to control the on/off of the equal output voltage amplifiers 11 to 1n. voltage amplifier 1A,
A binary signal is used to control 1B and 1C, and a plurality of power amplifiers constituting the high frequency power amplifier 1 are controlled to be turned on or off according to the amplitude of modulation. The output of the high frequency power amplifier 1 is combined by a voltage combining type combiner 2, passes through a filter 10, removes unnecessary high frequency components, and becomes the output of the transmitter.

FIG. 3 shows the voltage distribution of each power amplifier according to the amplitude of the audio signal when ten equal power amplifiers are used. PA1 to PA5 operate, and at the positive peak of 100% modulation (+100%), equal output voltage amplifier P
On/off control is performed by the modulation encoder 16 so that the voltage amplifiers from A1 to PA10 operate, and conversely, all voltage amplifiers stop at the negative peak (-100%). In practice, more than 1000 stages are required, and Fig. 4
1/2 of the output voltage of the equal output voltage amplifier, 1
A binary voltage amplifier such as /4...1/2n is also used.

[0005] Here, the means for reducing the output voltage of a binary voltage amplifier having the same circuit configuration as the equal output voltage amplifier to 1/2, 1/4, and 1/8 is usually the supply voltage of the binary voltage amplifier as shown in FIG. This is done by varying the voltage and the number of primary turns of the output combining transformer. In this example, the equal output voltage amplifiers 11 to 1n and the 1/2 binary voltage amplifier 1A are both connected to the voltage DC 20 of the first power supply 11.
While operating at 0V, equal output voltage amplifiers 11 to 1n
The output transformers 21 to 2n have a turns ratio of 10:1, and the output transformer 2A of the 1/2 binary voltage amplifier 1A is
By setting the turns ratio to 20:1, the output voltage of the 1/2 binary voltage amplifier 1A is equal to the output voltage of the equal output voltage amplifier 11 ~
It becomes 1/2 of the output voltage of 1n. Also, 1/4 binary voltage amplifier 1B and 1/8 binary voltage amplifier 1C
are both operated with the voltage DC50V of the second power supply 12, while the turns ratio of the output transformers 2B and 2C is 10:1 and 2, respectively.
By setting the ratio to 0:1, the equal output voltage amplifier 11 ~
1n, the output voltage of each amplifier 1B, 1C is 1/
4. Can be set to 1/8.

[0006]

[Problems to be Solved by the Invention] This conventional amplitude modulation transmitter uses first and second power supplies, and this power supply employs a general rectified and smoothed power supply circuit. The rate of voltage fluctuation in both power supplies is different (for example, voltage fluctuation in a transformer or choke coil), making it difficult to accurately match the output voltage ratio of the equal output voltage amplifier and the binary voltage amplifier to a predetermined value. For this reason, voltage adjustment between the equal output voltage amplifier and the binary voltage amplifier becomes inconsistent, and there is a problem that the input audio signal cannot be modulated faithfully and the distortion rate worsens. For example, the example in FIG. 5 shows a case where the voltage of the second power supply is greater than 1/8 of the voltage of the first power supply, and the X portion in the figure is in a state where it protrudes from the predetermined modulation envelope waveform. An object of the present invention is to provide an amplitude modulation transmitter that can faithfully modulate an audio input signal.

[0007]

[Means for Solving the Problems] The amplitude modulation transmitter of the present invention has a configuration of a power supply that supplies power to a high frequency power amplifier composed of an equal output voltage amplifier and a binary voltage amplifier. The configuration is such that the power supply voltage is variably controlled in accordance with voltage fluctuations of the equal output voltage amplifier so that the power supply voltage always has a constant voltage ratio with respect to the power supply voltage of the equal output voltage amplifier.

[0008]

[Operation] According to the present invention, the voltage of the power supply that supplies power to the binary voltage amplifier is set to a constant voltage ratio with respect to the voltage of the power supply that supplies power to the equal output voltage amplifier.
The output voltage also has a constant voltage ratio, which allows unification between both amplifications and prevents distortion in the audio input signal.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram of an amplitude modulation transmitter according to an embodiment of the present invention, and the same parts as in the conventional configuration shown in FIG. 2 are given the same reference numerals. In this embodiment as well, the high frequency power amplifier 1 is configured with n equal output voltage amplifiers 11 to 1n and 1/2, 1/4, and 1/8 binary voltage amplifiers 1A, 1B, and 1C, and the A/D The modulation encoder 16 is configured to switch each amplifier based on the audio input converted into a binary multi-bit digital signal by the converter 15. Further, a carrier wave is input through a high frequency oscillator 13 and a high frequency distributor 14. Furthermore, the output of the high frequency power amplifier 1 is combined by a combiner 2, unnecessary harmonic components are removed by a filter 10, and the output is output from a transmitter.

[0010] The first power supply 11 has equal output voltage amplifiers 11 to
This is a power supply for supplying DC power to the binary voltage amplifier 1A that outputs a voltage that is 1/2 of the output voltage of the equal output voltage amplifier 1n. is connected to the binary voltage amplifier 1A and the voltage detector 17. This voltage detector 17 is configured to extract a voltage divided by resistors R1 and R2. Further, the second power supply 12 has a binary voltage amplifier 1B that outputs a voltage that is 1/4 of the output voltage of the equal output voltage amplifier, and a binary voltage amplifier 1C that outputs a voltage that is 1/8 of the output voltage of the equal output voltage amplifier. This is a power supply for supplying DC power of /4. The second power supply 12 automatically changes the output voltage according to the voltage fluctuation detected by the voltage detector 17, and always changes the output voltage to 1/1/2 of the voltage of the first power supply 11.
4.

Therefore, according to this configuration, the power supply voltage of the binary voltage amplifiers 1B and 1C is always kept at a constant voltage ratio (1/4) with respect to the power supply voltage of the equal output voltage amplifiers 11 to 1n and the binary voltage amplifier 1A. It is possible to maintain the output voltage ratio of the equal output voltage amplifier and the binary voltage amplifier accurately to a predetermined value, and it is possible to faithfully modulate the audio input signal.

0012

[Effects of the Invention] As explained above, the present invention is configured such that the power supply of the binary voltage amplifier is variably controlled in accordance with voltage fluctuations of the equal output voltage amplifier, so that the power supply voltage of the binary voltage amplifier is always constant. This has the effect that the output voltage of each amplifier can be adjusted to a constant voltage ratio by setting a constant voltage ratio to the power supply voltage of the equal output voltage amplifier, and the audio input signal can be modulated extremely faithfully.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of an amplitude modulation transmitter of the present invention.

FIG. 2 is a block diagram of an example of a conventional amplitude modulation transmitter.

FIG. 3 is an operation allocation diagram showing amplitude modulation operation when ten equal output voltage amplifiers are used.

FIG. 4 is an operational division diagram of an equal output voltage amplifier and a binary voltage amplification.

FIG. 5 is an operation allocation diagram when the voltage ratio between the power supply voltages of the equal output voltage amplifier and the binary voltage amplifier is not appropriate.

[Explanation of symbols]

1 High frequency power amplifier 11 ~ 1n Equal output voltage amplifier 1A, 1B, 1C Binary voltage amplifier 21 ~ 2n
, 2A, 2B, 2C Output transformer 11 First power supply 12 Second power supply 13 High frequency oscillator 14 High frequency distributor 15 A/D converter 16 Modulation encoder 17 Voltage detector

Claims (2)

[Claims] Claim 1: Converting an audio signal into a multi-bit digital signal, converting this digital signal into a signal suitable for switching high-frequency power amplifiers using a modulation encoder, and controlling on/off multiple high-frequency amplifiers with the converted signal. In the amplitude modulation transmitter that generates an amplitude modulated wave by It consists of a binary voltage amplifier that outputs a voltage of 1/2n of
A part of the binary voltage amplifier is configured to be operated at a voltage different from a power supply of the equal output voltage amplifier, and the power supply voltage of the binary voltage amplifier is always a constant voltage with respect to the power supply voltage of the equal output voltage amplifier. 1. An amplitude modulation transmitter characterized in that the amplitude modulation transmitter is configured to be variably controlled according to voltage fluctuations of an equal output voltage amplifier so that the ratio is the same. 2. A high-frequency oscillator that generates a carrier signal, a high-frequency distributor that distributes this high-frequency signal to a plurality of high-frequency amplifiers, an A/D converter that converts an audio input signal into a multi-bit digital signal, and A modulation encoder that converts an A/D converter signal into a signal suitable for switching a high frequency amplifier, and a synthesis circuit that voltage synthesizes the output of a high frequency power amplifier consisting of a plurality of equal output voltage amplifiers and a binary voltage amplifier. , a filter that attenuates unnecessary high frequency components of the synthesizer output, a first power supply mainly for the equal output voltage amplifier, a voltage detector connected to the output of the first power supply to detect voltage, and this voltage detector. 2. The amplitude modulation transmitter according to claim 1, further comprising a second power supply for the binary voltage amplifier, the voltage of which is controlled by the output signal of the binary voltage amplifier, and whose voltage is always controlled to be equal to the output voltage fluctuation rate of the first power supply.