JPS61105101A - High efficiency ssb transmitter - Google Patents

Abstract

PURPOSE:To apply a large SSB power to antenna with less power loss by using an amplifier of the conventional class C operation as a power amplifier to be modulated so as to apply amplification of a single side band (SSB) system signal with excellent power efficiency. CONSTITUTION:A voice input signal AF is modulated at a balanced modulator 7 by a local oscillation frequency fS3, only one SSB wave is obtained via a BPF8, a pulse width modulation wave is obtained from a signal F obtained by envelope detection of the SSB wave at a detector D and from a triangle wave from a triangle wave generator 10 at a comparator 9, the modulated wave is amplified by a pulse amplifier 11 and subject to power amplification at a switching power amplifier 12. An LPF13 eliminates the switching frequency and its harmonics and the output is subject to amplitude modulation by the class C operation radio frequency power amplifier 17. A phase modulator 14 uses the AF input to apply phase modulation to a local oscillation frequency fS4, its output PM is converted into a prescribed SSB radio frequency using a local oscillation frequency fS5 at a frequency converter 15, an amplifier 17 is excited by using a signal amplifying the radio frequency at an amplifier 16 to obtain a radio frequency SSB power subject to amplitude modulation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention applies to a 5SB which requires linear power amplification.
(Single sideband) Transmitter improvement.

(Prior Art) Conventional SSB transmitters use class A or class AB amplification to amplify ssB waves. Figure 5 is the conventional SSB
This is a side view of the transmitter configuration, showing the case where a normal linear amplifier is used. In the figure, 1 is a balanced modulator for SSB generation, 2 is a band F-wave filter (BPF), 3 is a frequency converter, 4 is a front-stage linear amplifier, 5 is a final-stage linear amplifier, and 6 is a circuit between the antenna load impedance zo and 5. It is an impedance matching circuit. Note that /s is a locally excavated frequency signal for creating an SBR wave, and 'B2 is a high frequency signal for frequency conversion to obtain a required emitted radio wave. By the way, like the names, 4 and 5
The amplifier is required to have good linearity, and usually uses transistors or vacuum tubes, but in order to have good linearity, the amplifier must operate in class A or AB class. Therefore, even when there is no high-frequency input signal, these amplifiers must flow an idle current of more than a certain value.As a result, the power efficiency of the amplifier drops to around 30 cm, and the power loss is close to 70%. become.

Therefore, especially the cooling device for the amplifier 5 needs to have a large capacity, which poses an economic burden and maintenance problems.

Wireless transmission systems using amplitude modulation include carrier-sending double-sideband system (DSB) and carrier-suppressing double-sideband system (I18
BSO), single sideband system (5EIB) and vestigial sideband system (VSB)4; although it is well known that
It is well known that the SB method requires less transmission power than other methods, and has the advantage of having a narrower occupied bandwidth. In the SSB method, the carrier component and one sideband of the DSB wave are removed, and only the remaining sideband is transmitted. When an SSB wave is modulated by an audio input signal, it is amplitude modulated, but this is accompanied by phase modulation. S.S.
Since the B wave has a waveform completely different from that of the original audio signal, the original audio signal cannot be obtained even if envelope detection is performed as it is. Therefore, on the receiving side, a carrier wave is usually added and modulated to make the envelope the same as the original audio signal, and then envelope detection is performed.

(Specific Object of the Invention) It is well known that an SSB transmitter requires the use of a power amplifier with good linearity, and its power efficiency is poor. An object of the present invention is to provide an SSB transmitter that can perform SSB signal amplification with good power efficiency and supply large SSB power to an antenna with little power loss.

(Structure and operation of the invention) FIG. 1 shows the structure of the SSB transmitter embodying the present invention.
One wave in 100 KHz is used), and only one SSE wave of /85 and upper and lower sidebands is obtained through BPF8. A comparator 9 compares the signal F obtained by envelope detection of this with the triangular wave from the hexagonal wave generator 10, and outputs a pulse with a width proportional to the level of the signal F. Width modulated wave CPWM
wave) is obtained. This is amplified by the pulse amplifier 11,
A switching power amplifier 12 performs power amplification.

13 is an LPF which removes the switching frequency of the switched waveform and its harmonic components, and a signal as shown in FIG. 3 appears in its output. Reference numeral 17 denotes a radio frequency power amplifier of ordinary class C operation, which is an LPF 13 phase modulator, and this phase modulated wave output PM is converted into a predetermined SSB radio frequency by a signal of local oscillation frequency 'BS in the frequency converter 15. The modulated power amplifier 17 is excited by the signal amplified by the amplifier 16, and the amplitude-modulated radio frequency SSB power is matched by the matching circuit 18 to an antenna impedance of 2° and supplied to the antenna.

Next, the operation shown in FIG. 1 will be explained in more detail.

The carrier/s5 component of the audio signal AF is removed by the SSB generation balanced modulator 7, and only one sideband component is extracted by the BPF 8. FIG. 2 shows an example of the output waveform of the BPF 8. When this signal is envelope-detected by a diode D, a signal F having a waveform as shown in FIG. 3 is obtained. Signal F
has a completely different waveform from the audio input signal AP. The detected signal F is compared with a triangular wave from a triangular wave generator 10 in a comparator 9. Figure 4 shows this comparison operation for the part from α to b in Figure 3. When the triangular wave B and the envelope detection output A are compared, if the level of A is low, there is a gain. When the pulse width is narrow and the level of A is high, the pulse width becomes wide, and a PWM signal P subjected to pulse width modulation is generated at the output of the comparator 9. The PWM signal amplified by the next-stage pulse amplifier 11 becomes an excitation signal for the switching power amplifier 12.

The switching power amplifier 12 connects the DC power supply to the PW shown in Figure 4.
Switching is performed by the M signal P, and high-speed switching elements such as vacuum tubes or FETs are used.

The LPF 13 removes the triangular wave frequency component and its harmonic components from the waveform P switched by the amplifier 12, and its output is restored to the waveform shown in FIG.

On the other hand, the phase modulator 14 applies phase modulation to the local oscillation frequency fs4 using the audio signal AF, and its output, the phase modulated signal PM, is converted into a frequency converting frequency/frequency converter 15 including a bandpass circuit. The sum or difference component with s5 is extracted and converted to the desired SSB radio frequency for transmission.

This SSB wave output is amplified by the preamplifier 16 and then excites the modulated power amplifier 17. Note that fB4 is chosen high, for example from 1 to 3 MHz, to facilitate removal of the predetermined upper or lower sidebands of /85.

Now, the modulated power amplifier is a normal anode modulated class C amplifier, and is not an efficient A-type amplifier like the conventional linear amplifier for SSB.
It is highly efficient because it does not need to be a class or AB class amplifier. This modulated power amplifier 17 is amplitude-modulated by the output of the LPF 15, and its output undergoes amplitude modulation as shown in the t-2 diagram, and further becomes a necessary phase-modulated SSB radio frequency signal. This is matched to an antenna impedance of 2° by a matching circuit 18 and then supplied to an antenna 19.

(Effects of the Invention) Since the modulated power amplifier 17 shown in the t-1 diagram operates in a normal class C operation, it has much better power efficiency than the conventional SSB radio frequency linear power amplifiers 4 and 5. Furthermore, since the switching power amplifier 12 is a class D switching operation, its power efficiency is usually about 90chi, so the power efficiency of the entire amplifier 12 and 17 exceeds 70ch. This is 12
and 17 can be easily cooled, and the specified S can be achieved with less power consumption.
SB radio frequency power can be obtained. Further, according to the present invention, a normal amplitude modulated DSB wave can be obtained by inputting an audio signal to which an appropriate bias voltage is applied to the comparator 9 instead of the F signal and cutting off the audio input to the phase modulator 14.
Another great advantage is that the same transmitter can function as both an SSB transmitter and a DSB transmitter.

[Brief explanation of drawings]

Figure 1 is a configuration example of the SSB transmitter according to the present invention, Figure 2 is an example of an SSB wave, Figure 3 is a waveform diagram of envelope detection of the SSB wave in Figure 2, and Figure 4 is a triangular wave. 1, 1-
FIG. 5 is a diagram showing an example of the configuration of a conventional SSB transmitter. 1.7...SSE generated mean* modulator, 2,8...
BPF. 6.15... Frequency converter, 4,5... Linear amplifier, 6.18... Matching circuit, 9... Comparator, 10... Hexagonal wave generator, 11... Pulse amplifier , 16... Pre-stage amplifier, 17... Modulated power amplifier, 19... Antenna load.

Claims (1)

[Claims] A phase modulator that generates an output by phase modulating the first subcarrier based on the audio signal input, and outputting a single sideband radio frequency component for transmission by sum or difference synthesis of the phase modulated wave and the radio frequency input. a frequency converter, a preamplifier and a modulated power amplifier for amplifying the output thereof, a modulator and a bandpass filter for extracting the single sideband wave by the audio signal input and the second subcarrier frequency input;
A detector that detects the envelope of the output, and 3
A comparator that generates a pulse width modulation (PWM) wave proportional to the level of the detection output compared to the triangular wave from the square wave oscillator, an amplifier and a switching amplifier for the pulse output, and a switching frequency and its output. A high-efficiency SSB transmitter comprising: a low-pass filter that modulates the modulated power amplifier with an output excluding harmonic components, so that the modulated power amplifier operates in class C mode.