JPH01206745A - Spread spectrum receiver - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spread spectrum receiving device, and more particularly to an improvement in a signal processing device for ensuring synchronization of communication between transmitting and receiving devices.

[Conventional technology]

Figure 4 shows, for example, "IEEF, Commu.
n-cations Ma ni azine” Ju
ne 1984 vol, 22+No, 6)
Spread-Spectrum Signal Acquisition;
Methods and Technology 1 (“Sprea”
d-5pect-rum Signal Acquis
ition: Methods and Techniques
2 shows a conventional spread spectrum receiving device shown in 1.

In the figure, ■ is an element antenna for receiving frequency popping signals, 2 is an amplifier, 3 is a mixer for mixing the output signals of the amplifier 2 and the frequency synthesizer 12, and 4 is a mixer for mixing the output signals of the amplifier 2 and the frequency synthesizer 12.
is a band pass filter, 5 is a detector, 6 is an integrator, 7 is a comparator, 8 is a storage device, 9 is a clock generator, 10 is used to reset the integrator 6 for synchronization acquisition, and a code generator 11 11 is a code generator that generates a pseudorandom code as a hopping pattern, and 12 is a frequency synthesizer that generates a frequency signal corresponding to the code. Also 13
is a synchronized acquisition/tracking means composed of the above-mentioned components 6 to 12.

Next, the operation will be explained. The signal x,(t) received by the element antenna 1 is amplified by the amplifier 2, and then mixed with the output signal y(t) of the frequency synthesizer 12 by the mini-synthesizer 3. The mixed signal is band-limited by a bandpass filter 4 and detected by a detector 5. The detected signal is input to the integrator 6, which combines the received signal x(t) from the element antenna 1 and the frequency synthesizer 12.
A correlation value CXy(τ) with the output signal y(1) is calculated.

Cxy (τ) = x (t) ・y (t +
r)/(4 houses/box)...(1) The correlation value cxy(τ) obtained by equation (1) is input to the comparator 7 and compared with the numerical value in the storage device 8 that stores the correlation value. Ru.

A clock generator 9 generates clocks at regular intervals and transfers the clocks to the controllers 1 to 10 and the code generator 11. The controller 10 operates as shown in the flowchart of FIG. 5, for example. That is, when acquiring synchronization, first the code generator 11 generates a code as in step 14, and that code is used for a fixed number of clocks as shown in steps 15 and 16. Thereafter, as shown in step 17, the output of the comparator 7 is checked, and as shown in step 18, the correlation value CXY(τ
) exceeds the correlation value stored in the storage device 8. As shown in FIG. 6, CXY(τ) changes in value depending on the power of signal components other than the output signal y(t) of the frequency synthesizer 12 included in the received signal x(t).

In FIG. 6, the vertical axis is the value of the correlation value CXY(τ), and the horizontal axis is the desired wave that has a strong correlation with the output signal y(t) of the frequency synthesizer 12 included in the received signal x(t), and the is the power ratio of the weak interference wave.

In FIG. 6, A shows an example of a change in correlation value when x(t) includes a desired wave, and B shows an example of a change in correlation value when x(t) does not include a desired wave. From FIG. 6, it can be seen that when the power ratio (J/S) of the interfering wave and the desired wave becomes north of 12 dB, A and B become approximately the same value.

The controller 10 calculates the correlation value CXY (
If τ) does not exceed the correlation value stored in the storage device 8, the integrator 6 is reset as shown in step 19, and the sliding process is performed without counting the clock transferred from the clock generator 9 a certain number of times. I do. after that,
As shown in step 14 again, the above series of processes is repeated from the beginning with the next code. If it is determined in step 18 that the correlation value CXY(τ) of the output of the integrator 6 exceeds the correlation value stored in the storage device W8, then the next clock generator is activated as shown in step 20. The operation of causing the code generator 11 to generate a code is repeated every time a predetermined number of times is counted from the clock transferred from the code generator 9. The code generator 11 generates a code under the control of the controller 10 and transfers the code to the frequency synthesizer 12. The frequency synthesizer generates a sine wave signal of a frequency corresponding to the honopink pattern code transferred from the code generator 11, and transmits it to the mixer 3 described above. The operation described in -1- below performs synchronized acquisition and tracking between transmission and reception of spread spectrum communication.

[Problem to be solved by the invention]

Since the conventional spread spectrum receiver is configured as described above, when the received signal contains unnecessary waves with high power such as interference waves, the correlation value CXY(τ) obtained by equation (1) In order to make the changes shown in FIG. 6, the desired wave is included in the received signal. The value will be the same regardless of whether it is included or not.

For this reason, it becomes impossible to determine whether the received signal has a strong correlation with the output signal of the frequency synthesizer 16, and it becomes impossible to accurately detect the timing at which the code generation patterns of both the transmitter and the receiver match, resulting in failure of synchronization correction. There was a problem with it being put away.

This invention was made in order to solve the problems of the conventional ones as described above.It is an object of this invention to suppress unnecessary waves in the received signal to a level that allows correlation to be determined, and to efficiently perform synchronization acquisition and synchronization tracking. The purpose of this invention is to obtain a spread spectrum receiver that can perform the following functions.

[Failure to solve the problem]

The spread spectrum receiver according to the present invention has a plurality of element antennas, and based on a reference signal from a reference signal generator,
An adaptive filter is provided to remove unnecessary waves having a weak correlation with the reference signal from the received signal.

[Effect]

The adaptive filter of the present invention removes unnecessary waves by lowering the antenna gain in the direction of arrival of unnecessary waves and maintaining a high antenna gain in the direction of arrival of desired waves.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a spread spectrum receiver according to an embodiment of the present invention. In the figure, 30 is an array antenna consisting of N element antennas 1 for receiving frequency hopping signals, and 2 is an array antenna for each element antenna. 3 is an amplifier that mixes the N outputs of the amplifier 2 and the output of the frequency synthesizer 12; 4 is an N mixer that allows only a desired band to pass among the mixer outputs; 22 is an adaptive filter that inputs the outputs of the N bandpass filters 4 and the output signal of the reference signal generator 23 to remove unnecessary waves included in the received signal; 21 is the output of the adaptive filter 22; correlation value calculators 7 to 12 for calculating the correlation value between the output of the reference signal generator 23 and the reference signal generator 23 under the control of the controller 0;
has the same configuration as the conventional device, and the synchronized acquisition and tracking means 13 includes a correlation value calculator 21.

FIG. 2 shows the internal configuration of the adaptive filter 22,
In the filter 22, 33 indicates the outputs x, (n) to xN(n) of the N bandpass filters 4 and the load calculator 24.
25 is an adder for calculating the sum of the outputs of the N mixers 33, and 26 is for calculating the difference between the output of the adder 25 and the output of the reference signal generator 23. The attenuator 24 is a load calculator that calculates N load values from the N outputs of the bandpass filter 4 and the output of the attenuator 26.

Next, the operation will be explained. A frequency hopping signal is
The signal is received by an array antenna 30 consisting of N element antennas 1, and the signal received by each element antenna 1 is mixed with the signal output from the frequency synthesizer 12 by a mixer 3. At this time, if the received signal is synchronized with the receiving device, it will be demodulated into a signal of the desired band, and if not, it will hop to a completely different band. The signals mixed by the N mixers 3 are passed through the N bandpass filters 4, where the signals that have not been demodulated into signals in the desired band are removed, but the power of the signal to be removed is If is large, leakage will occur. The signal that has passed through the N(1M) bandpass filter 4 is input to the adaptive filter 22.

FIG. 2 is a block diagram of the adaptive filter 22, where x,
(n) to x8(n) correspond to the outputs of N band pass filters 4, respectively. Also, wl(n) ~ wN(
n) is the load value for unnecessary wave removal calculated by the load calculator, and x, (n) to Xe (n) are respectively w I (n) =
It is multiplied by w-(n) and mixer 33. The summation y (n) of each multiplied value is determined by an adder 25. y (n) is sent to the synchronization acquisition tracking means 13, and the difference is taken from the output j signal d (n) of the reference signal generator 23 by the attenuator 26, and is sent to the load calculator 24 as the error ε(n). is input. The load calculator 24 calculates x, (n)
~x, (n) and ε(n) are input, and the load value w, (
n) to wlI(n). Load value W1(n) ~ wI
The algorithm for calculating l(n) is, for example, the following 5eq
It is determined by the calculation formula of the mutual regression algorithm.

w,,=Wnl 4−ε” (n) kn=12)
λ fence pn-IX++ 1, =-□ ...(3) ■+λ-・,. ” pn-1x.

p, l−λ−′p,, −+ −λ−′L, lK,” p
,-.

...(4) H: Hermitian matrix *: complex conjugate λ: exponential weight-4ng
factor O〈λ〈1 The load value obtained by equation (2) is
), the effect shown in FIG. 3 can be obtained.

FIG. 3(a) shows the antenna gain before being multiplied by the load value, and the antenna gain in the desired wave direction is not very high, and the antenna gain in the unnecessary wave direction is relatively high. Such a reception state causes the received signal to have weight values WI(n) to wN(n).
By multiplying by , a reception state as shown in FIG. 3(b) is obtained, and the maximum value of the antenna gain is directed toward the desired wave direction, and the zero point of the antenna gain is directed toward the unwanted direction.

The correlation value between the output signal y (n) from which unnecessary waves have been removed by the operation of the adaptive filter 22 and the output signal d (n) of the reference signal generator 23 is determined by the synchronization acquisition tracking means 13
It is determined by the correlation value calculator 21 included in the. The correlation value determined by the calculator 21 is input to the comparator 7 and compared with the numerical value in the storage device 8 that stores the correlation value.

A clock generator 9 generates a clock at regular intervals and transfers the clock to a controller 10 and a code generator 11.

The controller 1o basically operates in the same way as a conventional controller. That is, at the time of synchronization acquisition, first the code generator 11 generates a code, and that code is used for a fixed number of clocks.

Thereafter, the output of the comparator 7 is checked to determine whether the correlation value output from the calculator 21 exceeds the correlation value stored in the storage device 8.

If the correlation value output from the calculator 21 does not exceed the correlation value stored in the storage device 8, the controller 10 resets the calculator 21 and repeats the clock transferred from the clock generator 9 a certain number of times. The sliding process is performed while counting, and then the process returns to the first step of the series of processes described above to restart the process. If the correlation value output from the calculator 21 exceeds the correlation value stored in the storage device 8, a code is generated every time the clock is transferred from the next clock generator 9 a certain number of times. The operation of causing the unit 11 to generate a code is repeated.

The code generator 11 generates a code under the control of the controller 10 and transfers the code to the frequency synthesizer 12.

The frequency synthesizer generates a sine wave signal of a frequency corresponding to the hopping pattern code transferred from the code generator 11, and transmits it to the mixer 3 described above. With the above operation,
Performs synchronized acquisition and tracking between transmission and reception of spread spectrum communications.

According to this embodiment, since the unnecessary waves are removed by providing an adaptive filter, the power of the unnecessary waves included in the correlation value y(n) obtained by the calculator 21 is The relationship between the A and 8 curves shown in FIG. 6 is on the left side of the line where J/S is 12 dB, and takes a value that allows synchronization acquisition timing detection. For this reason, synchronous acquisition and tracking can be performed in the same way as when no unnecessary waves exist.

In the above embodiment, the case where the element antennas 1 are arranged on the X axis is a near array antenna, but in the case of a planar array antenna where the element antennas are arranged in a two-dimensional array on the X and Y axes in a planar array antenna. The same effects as in the above embodiment can also be obtained.

In addition, in the above embodiment, 5e-qu is used in the load value calculator.
Although an example using the initial regression algorithm is shown, an algorithm such as the Widrow algorithm or the probability approximation algorithm may be used, and the same effects as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the spread spectrum transmission device according to the present invention, the period number hopping signal is received, and the period number hopping signal is
] In addition to the acquisition/tracking means, an adaptive filter for removing unnecessary waves is provided, so that the influence of unnecessary waves can be reduced and synchronized acquisition/tracking can be performed efficiently.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a spread spectrum receiver according to an embodiment of the present invention, FIG. 2 is a block diagram of the adaptive filter shown in FIG. 1, and FIG. 3 is a diagram illustrating the operation of the unnecessary wave removal means. , Fig. 4 is a block diagram of a conventional spread spectrum receiver, Fig. 5 is a flowchart showing the operation of the controller in the synchronization acquisition/tracking means, and Fig. 6 shows a change curve of the correlation value shown in the conventional example. FIG. In the figure, 1 is an element antenna, 2 is an amplifier, 3 is a mixer, and 4
21 is a correlation value calculator, 7 is a comparator, 8 is a storage device, 9 is a clock generator, 10 is a controller, 11 is a code generator, ] 2 is a frequency synthesizer, 22 is an adaptive filter , 23 is a reference signal generator, and 30 is an array antenna. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a spread spectrum receiver that receives one or more frequency hopping signals transmitted from each user after being frequency spread using a code, N antennas are used to receive the transmitted frequency hopping signals. an array antenna consisting of an array antenna, N mixers for mixing the respective outputs from the N antenna elements and signals generated by the frequency synthesizer, and N mixers for inputting the output signals of the N mixers. a bandpass filter, a reference signal generator that generates a reference signal, an adaptive filter whose input signals are the signal transferred from the reference signal generator and the output signals of the N bandpass filters, and a controller to be described later. a correlation value calculator that calculates a correlation value between the output signal of the adaptive filter and the output signal of the reference signal generator according to a control signal transferred from the controller; a storage means that stores the correlation value; and an output of the correlation value calculator. a comparator that compares the magnitude of the numerical values stored in the storage means; a controller that controls the correlation value calculator according to the output of the comparator; and a code generator that generates a code using a control signal from the controller. What is claimed is: 1. A spread spectrum receiver comprising a frequency synthesizer that generates a sine wave signal having a frequency corresponding to the code generated by the code generator.