JPH0683126B2 - Burst level adjustment circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to TDMA for performing transponder hopping, for example.
The present invention relates to a burst-corresponding level adjusting circuit used in an earth station receiving system of satellite communication.

(Prior Art) In a time-division multiplex (TDMA) type downlink that changes a frequency channel for each burst signal, that is, frequency hopping (called transponder hopping when switching transponders in satellite communication to change the frequency) , Satellite transponder output, satellite antenna amplitude frequency characteristics, spatial propagation loss frequency characteristics, low noise amplifier amplitude frequency characteristics, receiving frequency converter frequency channel level difference, etc. However, a bit error rate is deteriorated in a demodulator that performs automatic gain control with the peak value of the input signal and uses a soft decision error correction method.

In order to prevent the bit error rate from deteriorating due to the level difference between channels, the level difference between the frequency channels designated for burst signals is compensated for by the channel, and the level of each channel is made the same at the input of the demodulator. However, the burst-corresponding level adjusting circuit is a circuit that achieves such a function.

FIG. 2 is a block diagram of a conventional burst-corresponding level adjusting circuit. In the figure, the burst signal input to the signal input terminal 21 corresponds to the radio frequency input to the earth station device reception system, and has different levels for each frequency channel. The burst signal input from the input terminal 21 is supplied to one of the plurality of level adjusters 25a, 25b, 25c, ..., 25n through the level adjuster selection switch 23, and the level is adjusted. Output terminal 27 via synthesizer 26
It is supposed to be output from. Further, the level adjuster selection switch 23, the plurality of level adjusters according to the frequency selection signal used for selecting the reception frequency of the reception frequency converter supplied to the frequency selection signal input terminal 22 via the switch control circuit 24. Of each burst signal, the level of each burst signal is adjusted by the level adjuster selected corresponding to the frequency channel, and the level between the frequency channels of each input burst signal is adjusted. The difference is adjusted so that it is not at the demodulator input.

(Problems to be Solved by the Invention) The above-described conventional burst-compatible level adjusting circuit requires a level adjuster selection switch, a switch control circuit, a plurality of level adjusters, and the like, which complicates the circuit configuration and is uneconomical. There is a problem of being a target.

The present invention has been made in view of the above, and an object thereof is to provide a burst-corresponding level adjusting circuit which requires only one level adjuster, has a simple circuit configuration, and is economical.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention provides a method for each frequency channel during time-division multiplex communication in which frequency hopping is performed in which frequency channels are changed for each burst for communication. A burst-corresponding level adjusting circuit that adjusts burst signals input at different levels to predetermined levels, a level adjuster that adjusts the level of the input burst signal according to a control input signal, and known frequencies The value of the control input signal is set in correspondence with the burst signal input level difference for each channel by the required number corresponding to the frequency channel to be used, and the control input is provided every time the frequency channel of the input burst signal changes. The control input for switching the signal value and controlling the output level of the level adjuster to a predetermined level. And summarized in that a control circuit for supplying to said level adjuster of Patent.

(Operation) In the burst-corresponding level adjusting circuit of the present invention, with respect to each frequency channel whose level is relatively known in advance, a level adjuster corresponding to each frequency channel is provided so as to eliminate the level difference between all frequency channels. The gain of is determined in advance, and the control input signal corresponding to the frequency channel of the input burst signal is supplied to the level adjuster, which causes the output of the level adjuster to reach a predetermined level. Have control.

(Examples) Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a burst-corresponding level adjusting circuit according to an embodiment of the present invention. The burst-corresponding level adjusting circuit shown in the figure uses one level adjuster 13, and a burst signal is input to this level adjuster 13 via a signal input terminal 11, and the level adjuster 13 sets a predetermined level. The burst signal adjusted to is output through the signal output terminal 15. The level adjuster 13 is composed of, for example, a diode attenuator, a variable gain amplifier, etc., and has a control terminal, but adjusts the gain or the level of the input burst signal according to the control input signal supplied to the control terminal, The output level is adjusted to a predetermined level.

Specifically, the control terminal of the level adjuster 13 is connected to the frequency selection signal input terminal 12 via the level adjuster control circuit 14, and the frequency selection signal input terminal 12 uses the frequency selection signal used for reception frequency selection. A signal is supplied, and the frequency selection signal controls the level adjuster control circuit 14, and as a result, the level adjuster control circuit 14 supplies the level to the level adjuster 13 via the control terminal. The adjuster 13 is controlled to adjust the level of the input burst signal, which is different for each frequency channel, to a predetermined level.

The level adjuster control circuit 14 includes a plurality of dip switches 18a, 18b, 18c, ..., 18n corresponding to a plurality of frequency channels.
, And each level adjustment control value for each frequency channel is set by the dip switches 18a, 18b, 18c, ..., 18n. That is, each DIP switch 18a, 18b, 18c,
・ ・ ・, 18n is a transponder hopping whose output level is fixed for each transbonder (frequency channel)
Taking advantage of the characteristics of the TDMA system, for each frequency channel whose level is relatively known in advance, it is predetermined in advance so as to eliminate the level difference between all frequency channels. , 18n are connected to a selector 17, and the selector 17 is supplied with a frequency selection signal as a selection control signal from a frequency selection signal input terminal 12.
Each of the DIP switches 18a, 18b, 18c, ..., 18n is a group of switches corresponding to the required number of bits of data, and ON / OFF can be set for each bit. Therefore,
Each dip switch 18a, 18b, 18c, ..., 18n sets a switch corresponding to each bit of data according to the level adjustment control value data corresponding to the input signal level of each frequency channel used for communication, One of these digital data values is selected by the selector 17 by the frequency selection signal and input to the D / A converter 16. Further, the D / A converter 16 converts the digital value into an analog value, that is, a signal having a required voltage, and inputs the signal to the level adjuster 13 as a control input signal. Here, the frequency selection signal input to the frequency input terminal 12 is supplied to select the data of the corresponding DIP switch each time the frequency of the input burst signal is changed. Therefore, the level modulator 13 adjusts the level of the burst signal input from the signal input terminal 11 according to the control input signal of the analog voltage signal, and outputs the burst signal as a burst signal of a predetermined level by this. The control is performed so as to eliminate the level difference for each frequency channel.

[Effect of the Invention] As described above, according to the present invention, for each frequency channel whose level is relatively known in advance, each frequency channel is supported so as to eliminate the level difference between all frequency channels. In advance, the gain of the level adjuster is determined, and the control input signal corresponding to the frequency channel of the burst signal to be input is supplied to the level adjuster so that the output level of the level adjuster becomes a predetermined level. Since the level adjuster is controlled, the level of the burst signal can be accurately adjusted to a predetermined level by using only one level adjuster, so that the circuit configuration can be easily made economical.

The present invention also provides a transponder (frequency channel).
Utilizing the features of the transponder hopping TDMA method, in which the output level is fixed for each frequency channel, each frequency channel is supported so that the level difference between all frequency channels can be eliminated for each frequency channel whose level is known in advance. Since the gain of the level adjustment circuit is specified in advance, a level detector is not required. Therefore, a normal level detector is provided and the burst signal level adjustment is performed in real time to detect the burst signal level and perform gain control. The structure is simpler and less expensive than the circuit (AGC).

[Brief description of drawings]

FIG. 1 is a block diagram of a burst corresponding level adjusting circuit according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional burst corresponding level adjusting circuit. 11 …… Signal input terminal 12 …… Frequency selection signal input terminal 13 …… Level adjuster 14 …… Level adjuster control circuit 17 …… Selector 18a, 18b, 18c, ..., 18n …… DIP switch

Front page continuation (72) Inventor Shuzo Kato 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (56) References JP-A-60-152137 (JP, A) JP-A-56- 136055 (JP, A)

Claims (1)

[Claims] 1. A burst-corresponding level adjustment circuit for adjusting a burst signal input at a different level for each frequency channel to a predetermined level during time-division multiplex communication in which frequency hopping is performed in which communication is performed while changing the frequency channel for each burst. The level adjuster for adjusting the level of the input burst signal according to the control input signal, and the value of the control input signal corresponding to the known burst signal input level difference for each frequency channel, The required number is set according to the frequency channel used, and the value of the control input signal is switched every time the frequency channel of the input burst signal changes so that the output level of the level adjuster becomes a predetermined level. A control circuit for supplying the control input signal to the level adjuster for control. Paste corresponding level adjusting circuit.