JPS6333817B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides spread spectrum
Spectrum; hereinafter referred to as "SS". ) This relates to the improvement of the reception method in the direct communication method.

FIG. 1 is a transmission/reception configuration diagram in the direct method of the SS communication method. Figure 1a is the transmitter side, information 1
A carrier wave is modulated by an information modulator 2, and then the spectrum is spread by a spreading modulator 3 using an output signal from a PN code generator 4 having a band wider than the required bandwidth of the modulated wave, and the signal is transmitted from an antenna 5. FIG. 1b shows the receiving side, where the signal received by the antenna 6 is synchronized by the synchronization circuit 8, and the same PN code used on the transmitting side is supplied to the spreading demodulator 7. The signal received by the antenna 6 is converted into a narrowband information modulated wave by the spreading demodulator 7, restored to the original information 10 by the information demodulator 9, and output. In such a conventional reception system, the effect of removing other station signal components was obtained by spreading and demodulating the received signal and performing band reduction conversion to convert a wideband signal into a narrowband information modulated signal. However, this effect alone has the drawback that the number of simultaneous communication stations cannot be increased sufficiently in the SS communication system.

The present invention generates another station signal by calculating the sum and difference of a received signal and its delayed signal, performs amplitude processing so that the root mean square of the amplitude error of that signal is minimized, and subtracts that signal from the received signal. The purpose of this is to avoid destruction of the SS communication line by increasing the number of simultaneous communication stations in the SS communication system and removing interference signal components.

The structure and operation of the present invention will be explained.

FIG. 2 shows an other station signal generation circuit 21 for generating an interfering other station signal. Delay element 1
5, a sum circuit 16, a difference circuit 17, a switch 18, a buffer amplifier 19, a control signal input terminal 20, etc. In Figure 2, input terminal 11 receives
SS signal is input. Input terminal 12 has m・Δ
(m=0, 1, 2, . . . Δ is the time length of one chip of the PN code) A delayed signal is input. Output terminal 14
In this case, the signal input to the input terminal 12 is delayed by Δ and output. The signals input from each terminal are sent to the sum circuit 1
6 and difference circuit 17 perform a sum-difference operation, and 20
Either one of the calculation results is selected by the switch 18 according to the control signal input from the switch 18. The amplitude of the selected signal is halved by the buffer amplifier 19 and output from the output terminal 13. Here, set the following conditions.

Condition 1: The delay range m is a range in which the information modulation signal can be considered unchanged even if it is delayed.

Condition 2: The product of the center frequency of the signal and Δ is an integer.

Condition 3: Synchronization must be established for the desired signal.

The operation of the apparatus shown in FIG. 2 under these conditions will be explained with reference to FIG. It is assumed that the same signal is input to 11 and 12, and is the received SS signal input to the input terminal 11, and is the output signal delayed by Δ by the delay element 15. is + in the sum circuit 16
is a signal that has been halved after the calculation of , and is a signal that has been halved after the calculation of - in the difference circuit 17 . Figure 3a
The column shows the desired signal waveform, and the b column shows the waveform of the undesired signal. The terminals to which the desired signal is output by these sum-difference calculations can be known in advance because synchronization has been established and the pattern is known. Therefore, if you select a terminal that does not output a signal, you can set the output to zero. The switching between the α terminal and the β terminal in the switch 18 of FIG. 2 is shown as follows in correspondence with the waveform of FIG. 3.

Connect to the β terminal to obtain a signal of 0t<1・Δ 1 Connect to the α terminal to obtain a signal of Δt<2・Δ 2 Connect to the β terminal to obtain a signal of Δt<3・Δ 3・Δt< Connect to the α terminal to obtain a signal of 4.Δ When the switch 18 is controlled as described above, the desired signal output is zero at the output terminal 13 as shown in column a of Fig. 3. . On the other hand, since the undesired signal has a different pattern from the desired signal as shown in column b of FIG. 3, even with such terminal switching, an output signal exists as shown in column b of FIG. 3. However, only one other station signal generation circuit 21 cannot generate the undesired signal over the entire interval, and the undesired signal is obtained in a moth-eaten form.
For this reason, FIG. 4 shows an other station signal generating device 35 constructed by combining a plurality of other station signal generating circuits 21 shown in FIG. 2. The signal output from this device depends on the composite number k of the other station signal generation circuit 21, but the larger k is, the more other station signals can be generated over the entire interval. However, the signal becomes an amplitude-modulated signal with a random amplitude. Unless this amplitude modulation component is removed and made equal to the amplitude of the received undesired signal, it will be difficult to remove the undesired signal cleanly. It is vessel 36. The amplitude equalizer 36 includes a multiplier 29, a squarer 31, and a delay element 3.
3. Integrators 30, 32 and variable gain amplifier 34
Consists of etc. The undesired signal is subjected to amplitude processing using an appropriate gain g in the amplifier 34 and outputted from the output terminal 28. The gain g is set as follows.

Assuming that the desired signal is D(t) and the undesired signal is U(t), the more the band reduction effect of the SS communication method becomes ineffective,
Assume that the power of U(t) is large. Expressed numerically, it is as follows.

E{U ² (t)}≫E{D ² (t)} ...(1) However, E{X} means taking the average of X. If U^(t) is the output signal from the other station signal generator 35, the output signal from the amplitude equalizer 36 is written as gU^(t), and the error ε(t) is expressed as follows. .

ε(t)=U(t)−gU^(t) ...(2) If we differentiate the root mean square error E{ε ² (t)} with respect to g and set it as zero, then g=E{U( t)U^(t)}／E{U^ ² (t)}……(
3) becomes. Assume that g is fixed for Δ, and the averaging is performed for Δ
If the time average is used, the denominator and numerator of equation (3) can be rewritten as follows.

E{U^ ² (t)}=1/Δ∫〓 ₀ U^ ² (t)dt...(4) E{U(t)U^(t)}=1/Δ∫〓 ₀ U(t )U^(
t) dt≒1/Δ∫〓 ₀ {U(t)+D(t)}U^(t)d
t…(5) Approximation of equation (5) is possible based on the assumption of equation (1).

Therefore, an amplitude equalizer 36 shown in FIG. 5 is proposed as a circuit that embodies equations (4) and (5). The signal input from the input terminal 27 is {D(t)
+U(t)}, and the signal input from the input terminal 26 is
When U^(t) is multiplied by the multiplier 29 and integrated by Δ by the integrator 30, equation (5) is obtained. On the other hand, if the input signal from 26 is squared by 31 and integrated by 32, equation (4) is obtained. Signals for controlling the integration of 30 and 32 are obtained through the control signal input terminals of the synchronous circuits 8 to 39, and the gain of the amplifier 34 can be determined from the result of the integration. The configuration of the receiving system including the other station signal generator 35 and the amplitude equalizer 36 is shown in FIG. Since the gain determination in the amplitude equalizer 36 requires a processing time of Δ,
U^(t) and the received signal are delayed by delay elements 33 and 37, respectively, and after their times are matched, a subtraction circuit 38 removes the predicted undesired signal from the received signal.

According to the present invention, signal components of other stations that act as noise in the SS communication system are removed, so noise resistance is improved compared to conventional reception systems, and the number of simultaneous communication stations can be increased by the increased removal effect. . Furthermore, if there is another SS line in the immediate vicinity of a station that has established an SS line with a distant station, and its signal is a very strong source of interference, the SS line communicating with the distant station may is at risk of being destroyed.
Even in that case, the risk can be avoided by removing the interference signal component using this method.

[Brief explanation of drawings]

Figure 1 is a transmission/reception block diagram in the direct spread spectrum communication system, Figure 2 is the other station signal generation circuit,
FIG. 3 is a diagram showing the operation of FIG. 2, FIG. 4 is a diagram showing the other station signal generator, FIG. 5 is an amplitude equalizer, and FIG. 6 is a block diagram of the other station signal removal reception system of the present invention. . 1, 10... Information, 2... Information modulator, 3... Spreading modulator, 4... PN code generator, 5, 6... Antenna,
7... Spreading demodulator, 8... Synchronization circuit, 9... Information demodulator, 11, 12, 23, 26, 27... Input terminal,
20, 39...control signal input terminal, 13, 14, 2
4, 28... Output terminal, 15, 33, 37... Delay element, 16, 22... Sum circuit, 17, 38... Difference circuit,
18...Switch, 19...Buffer amplifier, 21...
Other station signal generation circuit, 25... Switch control signal generation circuit, 29... Multiplier, 30, 32... Integrator, 31
... squarer, 34 ... variable gain amplifier, 35 ... other station signal generator, 36 ... amplitude equalizer.

Claims (1)

[Claims] 1. Prepare a plurality of circuits 21 that select only the output that does not output the local station signal by performing summation and difference calculations between the delayed received signal and the undelayed received signal, and synthesize the outputs. Device 3
A signal from another station is generated from 5, and the signal is processed by an amplitude equalizer 36 which performs amplitude processing so that the root mean square error between the amplitude of the signal and the true amplitude is minimized.
Subtraction circuit 3 from the received signal delayed by the processing time
8. Another station signal removal reception method in a direct spread spectrum communication system, characterized in that other station signals are removed by subtraction in step 8.