JPS61161057A - One frequency repeater - Google Patents

Abstract

PURPOSE:To remove easily a transmitting receiving interference by controlling the radio frequency of a variable frequency oscillating device by a carrier phase difference detecting device output and generating a transmitting receiving interference from a transmitting port to a receiving port with the same radio frequency. CONSTITUTION:The carrier phase difference detecting device is provided as independent blocks 94 and 95, and the output T is fed back to the variable frequency oscillating devices 21 and 41 of modulators 2' and 4'. Since the output T of carrier phase difference detecting devices 94 and 95 indicates the carrier phase difference of the first and second digital modulating waves, the frequency of the first and second digital modulating waves can be synchronized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a repeater for digital transmission in the microwave band.

(Prior Art and its Problems) The conventional microwave band relay system employs a two-frequency system in which one round-trip system is composed of two carrier waves. An example is shown in FIG. In the figure, 100.101°102 indicates a repeater, and fl and f2 indicate two carrier frequencies. In this example, if we take the repeater 101 as an example, it transmits at the same frequency f0 in two directions, left and right, and receives f2 at the same frequency from two opposite directions, right and left. Such a method is described in the literature Moriji Kuwahara.
Supervised by ``Digital Microwave Communication'' (Planning Center).

Since the two-frequency system uses different frequencies for transmission and reception, interference between transmission and reception can be reduced. The disadvantage of this method is that it requires twice the frequency band compared to the single frequency method described below.

Figure 3 is a diagram to explain the -frequency system, in which separate antennas are normally prepared for transmission and reception, and are operated by arranging them in a direct product to minimize interference between them. .

FIG. 4 is a diagram for explaining the state of interference between transmitting and receiving in the -frequency system, and is drawn using the repeater 101 in FIG. 3 as an example. In FIG. 4, a signal 203 is relayed as a signal 202 from left to right as an uplink, and a signal 201 is relayed as a signal 202 from right to left as a downlink. Now, if we consider the interference between transmitter and receiver for the received signal 201, the interference signal 2 from the uplink transmit signal 200
03 and an interference signal 204 from the downlink transmission signal 202. 180 in the figure. 181 each goes up,
A regenerative repeater for downlink is shown.

FIG. 5 is a diagram showing an equivalent baseband model of the repeater with interference between transmitting and receiving in FIG. 4. 180' in the figure, 1
81' is a signal identifier (identifies the transmission code) corresponding to the regenerative repeater, and delay circuits 134, 135, 136° 137 correspond to the propagation time from the transmitting antenna to the receiving antenna, It is always attached to interference signals between transmitter and receiver. Also multiplication xxso, 131.132
133 represents the phase rotation of the interference wave signal caused by a slight difference in each carrier frequency, and its rotational angular velocity ΔW is generally Δw-<symbol rate. Adders 140 and 141 indicate that a transmitter-receiver interference signal is added to the received signal. Terminal 1001゜1
003 corresponds to a transmitting antenna, and terminals 1004 and 1005 correspond to receiving antennas.

(Object of the Invention) An object of the present invention is to provide a device that eliminates interference between transmitter and receiver by adaptive control technology and realizes a single frequency system with excellent frequency utilization efficiency.

(Structure of the Invention) The present invention transmits a first digital modulated wave from a transmitting port, and transmits a digital modulated wave having the same frequency as the first digital modulated wave from a receiving boat provided in the same direction as the first transmitting port. In a single frequency repeater that receives a modulated wave, (a) an identification error detector that detects a difference between a value before identification and a value after identification of the second digital modulated wave, (b) the first digital a variable frequency oscillator that outputs a radio frequency of a modulated wave; (C) a carrier phase difference detector that outputs a correlation between the value of the discrimination difference detector and the transmission code of the first digital modulated wave; The radio frequency of the variable frequency oscillator is controlled by the output of the carrier phase difference detector, so that interference between transmission and reception from the transmission boat to the reception port is generated at the same radio frequency, and the interference can be easily removed. be.

(Detailed explanation of the configuration) Figure 5 shows the state of interference between transmitter and receiver.As mentioned earlier, since Δw is a 4 symbol rate, the multiplier 1
0.131.132.133 can be replaced by a complex coefficient multiplier whose coefficients change slowly, and can be considered as a complex constant coefficient multiplier in the short term. Therefore, in order to remove the interference between terminals 1200 and 1201 in the same figure, a filter with the same effect as this is prepared, and a discriminator 1 is added to it.
By applying the output from 80' to create a replica of the interfering signal and subtracting it from the receive antenna signal (terminal 1005), the interfering components will be cancelled. Actually Δ
Since W≠O, the previous filter needs to change its tap coefficient according to the change in ΔW.

FIG. 6 is a diagram showing the configuration of a single-frequency central amplifier during single-polarization operation. In the figure, reference number 200.201.202.20
3.degree. 101 corresponds to the same reference numerals in FIG.

Reference numeral 1.3 indicates a demodulator that converts a digital modulated wave into a baseband signal, and 2 and 4 indicate modulators that modulate the baseband digital signal.

5.6 is a discriminator that identifies the transmitted code from the received digital baseband signal, and is designated by reference number 18 in FIG.
This corresponds to the discriminators 0' and 181'.

7.8 is a transmitting/receiving interference canceling device, whose configuration, taking block 8 as an example, has the same characteristics as the transfer characteristics between the terminals 1200 and 1201 in FIG. Filter 80 and terminal 1202゜1 in Figure 5
It consists of a filter 81 having the same characteristics as those between 203 and an adder (subtracter) 83 that subtracts the filter output from the input signal in order to cancel the interference between the transmitter and the receiver. Here, the delay circuit 82 is for adjusting the relative time between the input signal and the filters 80 and 81.

Block 7 has exactly the same configuration as this, and the first
This is to eliminate interference between transmission and reception to the input signal 203 in the figure.

FIG. 7 shows the details of the configuration of the filter 80 and an example of its peripheral configuration in FIG. 6. 80, 83 in the figure
．． 6 is the same as reference number 80.83.6 in FIG. 80 is a transversal filter, 801.8
02゜803, 804 are delay circuits, 805.806.8
07.808.809 are coefficient taps, and by changing these coefficients, a filter with arbitrary characteristics can be realized.

In FIG. 7, reference numeral 9 indicates an example of a control device that adaptively controls coefficient taps. The transmission/reception interference signal is detected as a discrimination error e by the input/output difference of the discriminator (using the subtracter 91), and since this error has a strong correlation with the transmission code, it is input from the input terminal 1101. A multiplier 93 takes a correlation between the transmission code and e, and a next low-pass filter 92 smoothes the correlation, and the coefficients of each tap are controlled in a direction such that this correlation becomes zero.

Next, consider the case where the 6w4 symbol rate condition is not satisfied. In this case, each tap coefficient of the filter 80 is changed by the action of the control device in block 9 to follow the change in exp (ΔW), but as °ΔW increases, the tracking error increases, and eventually an effective transmission/reception interference signal will no longer be performed. To avoid this situation, Δ
It is necessary to detect W and control the frequency of the transmitted carrier wave, which is a source of interference, to maintain the 6w4 symbol rate.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention. Reference numbers 1.3.5.6 in the figure are the same components as in FIG. The modulators 2' and 4' are composed of a combination of modulators 2 and 4 shown in FIG. 6, using variable frequency oscillators 21 and 41 as carrier generators so that the carrier frequency can be finely adjusted. 18 for the transmitter/receiver interference remover 7 and 8
Considering that the interference between back-to-back antennas at 0° is small,
The interference removal between them was omitted, and the filters 71 and 81 in FIG. 6 were removed accordingly. Furthermore, in order to facilitate the explanation, the filters 80 and 81 are configured with only one tap coefficient.

Next, the newly added components will be explained. Blocks 50 and 60 are identification error detectors that detect the difference between the pre-identification value and the post-identification value of each received digital modulated wave, and the output thereof is mainly interference between transmitter and receiver.

The carrier phase difference detector 94.95 includes a multiplier 96.99 that correlates the value e of the previous identification error detector with the transmission code of the transmission digital modulation wave, and an imaginary part selection circuit for the output of this multiplier. It consists of 97.98. (The imaginary part selection circuit that outputs only the imaginary part of the complex output of the multiplier does not actually exist.) The interference between the transmitter and the receiver due to the transmit code included in e is caused by the delay circuit of the equivalent circuit in Figure 5. 134°135, 13
6.137, e : D-exp(jΔ
The output T of the w character phase detector is T = IWL(e −D≠1 (D* is D(7)
complex first flight) = IWL(D −exp σΔW)・D“
−ノ=+D+2sin (ΔLυ) From this, it can be seen that T represents the carrier phase difference between the first and second digitally modulated waves. Therefore, by feeding back this value to the variable frequency oscillators in the transmission signals 2' and 4', the frequencies of the first and second digitally modulated waves can be synchronized, and ΔW:O can be achieved. The above is an explanation of the principle and embodiments of the present invention.

In the embodiment of FIG. 1, the carrier phase difference detector is provided as an independent block 94, 95, but the imaginary part of the coefficient of the center tap 807 of the filter 80 of FIG. 7 can also be used as the preceding T. In this case, the configuration shown in FIG. 6 can be used as is.

(Effects of the Invention) As described above, according to the present invention, the microwave relay system, which was conventionally operated as a two-frequency system, can be realized as a single-frequency system, and the frequency utilization efficiency is doubled.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing one embodiment of the present invention, and Fig. 2 is a diagram showing an embodiment of the present invention.
Figure 3 is a diagram to explain the frequency relay system, Figure 4 is a diagram to explain the interference between transmitter and receiver in the single frequency relay system, and Figure 5 is a diagram to explain the interference between the transmitter and receiver in the single frequency relay system. FIG. 6 is a diagram showing a baseband equivalent circuit, FIG. 6 is a diagram showing a single frequency repeater during single polarization operation, and FIG. 7 is a diagram showing an example of the configuration of the first and second filters. In the figure, 1.3... Demodulator 2, 4... Modulator 5.6... Discriminator 21.41-...
・Oscillators 71, 80...Filters 50, 60.73.83...Subtractors 96, 99...
... Multiplier 97.98 ... Imaginary part selection circuit. Figure 2 Figure 3 Figure 4 Figure 5 Figure 7

Claims (1)

[Claims] A first digital modulated wave is transmitted from a transmission port, and a first
In a single frequency repeater that receives a digital modulated wave having the same frequency as the first digital modulated wave from a receiving port provided in the same direction as the transmitting port, (a) before identifying the second digital modulated wave; (b) a variable frequency oscillator that outputs the radio frequency of the first digitally modulated wave; (c) the value of the discrimination error detector; a carrier phase difference detector that outputs a correlation between the first digitally modulated wave and the transmission code; the radio frequency of the variable frequency oscillator is controlled by the output of the carrier phase difference detector; A single-frequency repeater characterized by generating interference between transmitting and receiving at a receiving port at the same radio frequency.