JPS589438A - Communication system of constant electric power and single side band - Google Patents

Abstract

PURPOSE:To ensure the desired band width of SSB and to facilitate the handling of FM, by securing almost constant level for the total sum of the energy of a carrier and the energy of a side band. CONSTITUTION:In order to control the carrier quantity of reinsertion by an AF signal of a modulating/amplifying circuit, a modulated signal passed through an amplifier 2 from a microphone 1 and the output of a carrier oscillator 3 are applied to a balanced modulator to produce a DSB signal. This DSB signal is converted into an SSB signal through a filter 5, and a front edge part is formed for an SSB signal transmitter which supplies the SSB signal to an IF amplifier 6. On the other hand, a carrier is reinserted to an SSB.IF stage through a circuit 7 to be controlled. The circuit 7 is formed so that the intensity of modulated signal is adversely proportional to the carrier intensity by a control signal obtained by eliminating the audible frequency component of the output of a modulated signal amplifier 8 through a LPF9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a type of SSB (Single 5ide Ban) particularly suitable for mobile communication in the VHF-UHF band.
d) It seeks to provide a communication method that uses radio waves.

SSB is currently used for most HF band telephone communications. The advantages of SSB are that it is power efficient, has a narrow occupied bandwidth, and is less affected by selective fading, but on the other hand, it is difficult to tune the receiver, and the AGC' is fast attack/slow release and has a large holding time constant. Therefore, there is a problem in applications where the signal strength changes rapidly, such as in mobile communications in urban areas.

On the other hand, for mobile communications in the VHF-UHF band, FM waves have been widely used because they are easy to tune and can cope with sudden changes in signal strength. In order to increase the number of channels, the amount of frequency shift is reduced at the expense of communication distance, but the required bandwidth is still considered to be at the limit of l Q kHz. In this respect S
SB is extremely advantageous because it only requires a bandwidth of about 3 kHz.

The purpose of this invention is to obtain a radio wave format that combines the required bandwidth of SSH and the ease of handling of FM. In other words, it basically uses one sideband modulation component and carrier similar to A3J and A3A. An amplitude-modulated wave consisting of The ideal is This can be illustrated in Figure 1 (A
) is a case where the total sideband energy still exceeds the maximum output of the transmitter, and it is desirable that the carrier has a value lower than the maximum output by 940 dB, and in this case it will be the same as A3J. (B) is a case where the sideband is 0 in an unmodulated state, and the carrier has increased to the maximum output. (C) is a modulation state intermediate between (A) and (+'3), and a carrier exists that is the difference between the sum of sideband energy and the maximum output.

However, when actually modulated by voice, the Zuidbandoss overlapping tram is a series of complex waveforms with a mixture of frequency changes and amplitude changes, and if you look at this in terms of changes in the sound level, you can see the periodicity as shown in Figure 2. Since short-cycle amplitude changes are superimposed on long amplitude changes of Since the waveform is an amplitude modulated wave having a waveform opposite to that of the waveform, a problem arises in that side waves accompanying the carrier are mixed. Therefore, in reality, the carrier is configured so that short-cycle (high-frequency) changes do not occur. For example, if the amplitude change has a cycle of 01 seconds or more, the sideband will be 10 Hz or less, which will affect the receiving side. This is not the case at all, and it may be necessary to add a 10 Hz cutoff (actually 20 to 30
One method is to insert an LPF or an integrating circuit (in many cases, even z does not cause any problem).

The advantage of using this type of radio waves is that the conventional S
The so-called Konno-e, which can receive the first part with an SB receiver.
It's a trivial thing. In this case, in a non-modulated or shallowly modulated state, the carrier is at the same frequency as the BFO of the receiver, so the zero-in of SSB tuning can be made very clearly. Furthermore, by slightly modifying the AGC circuit of the receiver, it is possible to expect an AGC operation equivalent to or better than that of an AM receiver with a carrier, and it is also possible to perform AFC by sampling during a period when the carrier level is high.

On the other hand, since the transmitter always operates at maximum output, the power efficiency of the output stage is lower than that of the A3J, and naturally it generates more heat. However, the output power is 10W, which is often used for transportation.
Since power efficiency and heat generation are not problems at all with FM machines of this size, it must be said that this system, which can operate in a much narrower band in place of FM, has sufficient value.

The circuit configuration for generating the signals of this method will be described below. Basically, this can be achieved by controlling the amount of carrier re-input in the A3A or A3H generation circuit using a modulation component, but there are at least the following three methods of detecting a control signal for a modulation component. FIGS. 3 to 5 show block diagrams of examples of signal generating circuits of this system.

Figure 3 shows how to control the amount of carriers re-input from the AF multiplied signal in the modulation amplifier circuit.
The modulated signal passed through the carrier oscillator 3 and the output of the carrier oscillator 3 are added to a balanced modulator to create a DSB signal, which is then passed through a filter 5 to the S
This is the configuration of the front stage of the SSB transmitter that converts the carrier into an SB signal and supplies it to the IF amplifier 6. Separately, the carrier is re-entered into the SSB/IF stage through the controlled circuit 7, but the amount is equal to the output of the modulation signal amplifier 8. (5) The controlled circuit 7 is constructed so that the modulation signal strength and the carrier strength are inversely proportional to each other by a control signal from which the audible frequency component has been removed through the LPF (or integrating circuit) 9.

Figure 4 shows that instead of the modulation signal in the previous example, a 5SB-IF4 signal is applied to the envelope detection circuit 10, and its output is output to the LP.
The amount of carrier input is controlled by a control signal from which the audio frequency component has been removed through the F (or integrating circuit) 9, and is taken out from the output side of the 5SB-IF multiplied signal balance modulator 4. If carrier removal is insufficient, it is preferable to take out the carrier after the SSB filter 5 as shown in FIG.

Next, considering the operation on the receiving side, since the output level of the transmitted wave is always almost constant, the AGC circuit is used to remove ripples due to modulation components.
Since the time constant of the circuit can be made extremely small, the ability of the AGC to follow sudden changes in signal strength is improved. However, since it is necessary to receive the carrier as well as the sideband, the bandwidth of the IF filter needs to be made slightly wider.

Alternatively, the receiving IF may be left as is, and an AGCIF amplifier may be provided separately.

The advantage of sampling the carrier and using AFC to facilitate zero-in of SSH (6) was mentioned earlier, but in addition, the transmission side can take advantage of the fact that the gear amount is inversely proportional to the modulation signal. The ideal converter method can be applied by compressing and modulating the modulated signal, extracting the compression rate information included in the amount of gear change on the receiving side, and performing the opposite expansion. there is a possibility.

As mentioned above, in the invention of , the power efficiency of the transmitter output stage is inferior to that of the AaJ method, but the required bandwidth is much narrower than the FM method, and the communication method is easier to tune than the A3J method. As such, it is extremely effective in resolving the shortage of communication channels for mobile low-power radio equipment, especially in the VHF band.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the energy configuration of the radio wave format of the present invention. Figure 2 is a model diagram of the audio waveform. FIG. 3 shows an example of the configuration of a transmitter that generates the radio wave format of the present invention. FIGS. 4 and 5 show other configuration examples of a transmitter that generates the radio wave format of the present invention. 1...Microphone, 2.8...Microphone amplifier, 3...Carrier oscillator, 4...Balanced modulator, 5...
・Filter, 6... IF amplifier, 7... Carrier controlled circuit, 9... LPF (or integrating circuit), 10
...Envelope detection circuit. b Story A friend Yasu * Yusa Ujimu A・L Sumire i +z 蓼31λ b ri ZIA time head −〉

Claims (1)

[Claims] A wireless transmission system consisting of a carrier and one sideband, characterized in that it is configured such that the sum of the energy held by the carrier and the energy held by the sideband is always approximately constant.