JPS6342445B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a passband optimal ratio combining reception system that has both space diversity combining reception and interference wave removal functions in a wireless communication system used for digital data transmission.

In recent years, especially in defense communications, there has been a demand for reception systems that are resistant to interference. Moreover, due to the need to minimize the number of relay stations in the defense line that is applied,
Non-line-of-sight communication systems are often used, and diversity combining reception technology is also essential.

By the way, the conventional technologies that can be applied as reception methods that are resistant to interference are as follows: (1) SS (Spread)
(2) AIC
(Adaptive Interference Cancellation) technology. Among these, (1) is a method of changing the communication method itself to increase anti-jamming performance.
Although it is excellent in principle, there are many points in which it lacks compatibility with existing methods and existing hardware technology, making it impractical. Method (2) attempts to adaptively remove interference waves by devising a receiving method, and although it has its limitations, it is practically excellent.
In addition, although there are many conventional technologies related to space diversity combining reception, optimal ratio combining (also called maximum ratio combining or square-law combining) is the most superior combining method, and it is also superior to baseband combining. It is said that the method of synthesis in the passband) is advantageous.

Therefore, based on the above considerations, an object of the present invention is to provide a space diversity combining reception function using a passband optimum ratio combining method and an interference wave removal function using an AIC (adaptive interference cancellation) method. Therefore, it is an object of the present invention to provide a highly reliable passband optimum ratio combining reception system that is resistant to interference and suitable for relay lines.

According to the present invention, in the intermediate frequency stage of a space diversity receiver, the first automatic gain control means receives a signal received by one antenna and outputs a first output signal amplified to a constant level; a second automatic gain control means for receiving a received signal and amplifying it to a constant level and outputting a second output signal; and a first switch for switching the first and second automatic gain control means to a common mode or an independent mode. , first and second output signals that control the amplitude and phase of the first and second output signals by first and second control signals, respectively, to generate third and fourth output signals.
a combination means for combining the third and fourth output signals; a third automatic gain control means for amplifying the combined signal to a constant level; A second switch that switches whether or not to pass the third automatic gain control means.
a demodulating means for synchronously detecting the synthesized signal and converting it into a baseband signal; a determining means for determining the baseband signal and emitting a fifth output signal; subtracting means for generating a baseband error signal by subtracting the output signal of 5; modulation means for converting the baseband error signal into a passband error signal; and the first and second output signals and the passband error signal. first and second correlation calculating means for calculating the correlation with the error signal of third and fourth switches for selecting the reference signal or the first correlation output signal and the reference signal or the second correlation output signal as the first and second control signals, respectively; When operating in the composite mode, the first switch is set to the common mode, the second switch is set to the composite signal, and the third and fourth switches are set to the one that does not pass the third automatic gain control means. to select the first and second correlation output signals as the first and second control signals, respectively, and when operating in the interference wave removal mode, the first switch is switched to the independent mode. , the second switch is switched to pass the synthesized signal through the third automatic gain control means, and the third and fourth switches switch one of the switches depending on the interference situation to the reference signal. A passband optimum ratio combining reception system is obtained which has an interference wave removal function in which the signal is switched to the signal selection side and the fifth output signal is used as the data output of the device.

Next, a detailed description will be given with reference to the drawings.

The drawing is a block diagram of the intermediate frequency stage and subsequent stages of a passband optimum ratio combining reception system equipped with an interference wave removal function according to the present invention. The basic configuration and operation of this system will be explained below based on the drawings. In the figure, 10 and 20 are intermediate frequency variable gain amplifiers. And 11 and 21 are AGC amplifiers that can perform common automatic gain control, and their outputs are sent to the switch S ₁ through diodes 11' and 21' when the system operates in optimal ratio combining mode. switch S 1 is coupled (S ₁ is turned to the side) and applied in common to intermediate frequency variable gain amplifiers 10 and 20, and when the system is operated in interference rejection mode, switch S ₁ is open (S ₁ is turned to the side). (tilted to the side) are applied independently to intermediate frequency variable gain amplifiers 10 and 20, respectively. These automatic gain control circuits are used to ensure the dynamic range of the subsequent signal processing circuit against fluctuations in the received input level.

Further, 12 and 22 are delay circuits, 13 and 23
is a complex conjugate circuit, 14 and 24 are multiplication circuits (passband x passband), 15 and 25 are gate circuits or sample-and-hold circuits, 16 and 26 are low frequency generators, 17 and 27 are DC amplifiers, 18
and 28 are reference voltage generators, 19 and 29 are complex four-quadrant multipliers (DC signal including low frequency components x passband), and S ₃ and S ₄ are switches. here,
Delay circuit 12 to complex four-quadrant multiplier 19, switch
S ₃ is connected to diversity path-1 and also to delay circuit 2.
The 2- to 4-quadrant multiplier 29 and switch S ₄ are circuits that have the same functions as those used in diversity path-2, and control the amplitude and phase of the passband signal to perform optimal ratio combining or interference wave removal. This is the main part of the signal processing circuit that makes this possible. The respective output signals of the intermediate frequency variable gain amplifiers 10 and 20 are controlled in amplitude and phase by the control signals of the DC amplifiers 17 and 27 when the switches S ₃ and S ₄ are both turned to the side in the optimum ratio combining mode. is controlled, and in the case of interference rejection mode, the switch S ₃ is on the side and S ₄ is on the side, or S ₃ is on the side and S ₄ is on the side, and the reference voltage generator 18 and the DC amplifier 27 or the DC amplifier 17 are The amplitude and phase are controlled by the control signal of the reference voltage generator 28 and the reference voltage generator 28.

Furthermore, 30 is an adder, 31 is an intermediate frequency variable gain amplifier, 32 is an AGC amplifier, 33 is a synchronous detection demodulator (including a carrier recovery circuit, a clock recovery circuit, a baseband converter, etc.), and 34 is a determiner ( 35 is a subtracter, 36 is a linear modulator (baseband×passband complex four-quadrant multiplier), and _S2 is a switch. The output signals of the complex four-quadrant multipliers 19 and 29 are then combined by an adder 30, and in the case of the optimum ratio combining mode, the output signals of the complex four-quadrant multipliers 19 and 29 are combined by a switch.
S ₂ is turned to the side and applied to the demodulator 33, but in the case of interference wave removal mode, the switch S ₂ is turned to the side and the signal is amplified to a constant output level by the intermediate frequency variable gain amplifier 31 and AGC amplifier 32. The signal is applied to the demodulator 33 and demodulated. The output signal of the demodulator 33 becomes the output signal determined by the determiner 34, and in order to adaptively perform the signal processing, an error signal is generated by the subtracter 35, and regenerated into the passband by the linear modulator 36. modulated and commonly applied to multiplier circuits 14 and 24. Further, the correlation output signals of the multiplier circuits 14 and 24 are sent to gate circuits (or sample-and-hold circuits) 15 and 25, which are operated by gate pulses generated from the clock reproduced by the demodulator 33, and correspond to the center of the transmitted data. sampled (held) at the same timing.

The operation of the optimal ratio combining mode is as follows. At that time, all switches S 1 to S 4 are in a state where they are tilted to the side. The output signals of the intermediate frequency variable gain amplifiers 10 and 20 are X 1 (nT) and X 2 (nT), respectively.
[X 1 (nT)=α 1・A o・e j( 〓 cnT+ 〓 1) X 2 (nT)=α 2・A o・e j( 〓 cnT+ 〓 2) ] …(1) . The signal has sample values of t=nT (n is an integer, T is the transmission data interval) and is expressed as an analytic signal. Also, in equation (1), α 1 is X 1 (nT)
The amplitude of (positive real number) , α 2 is the amplitude of > is normalized to 1, (* indicates complex conjugate, <> indicates average value) ω c is the angular frequency of the carrier wave, θ 1 is the phase of X 1 (nT), and θ 2 is X 2 ( nT). DC amplifier 17
and 27 control signals are respectively C 1 and C 2 ,
Letting the output signals of the complex four-quadrant multipliers 19 and 29 be Y 1 (nT) and Y 2 (nT), respectively, Y 1 (nT) = C 1・X 1 (nT) = C 1・α 1・A o・e j( 〓 cnT+ 〓 1 ) Y 2 (nT)=C 2・X 2 (nT)= C 2・α 2・A o・e j( 〓 cnT+ 〓 2 ) …(2). If the output signal of the adder 30 is Y(nT), then Y(nT) = Y 1 (nT) + Y 2 (nT) = (C 1・α 1・e j 〓 1 +C 2・α 2・e j 〓 2 )・A o・e j 〓 cnT
…(3) becomes. The operation of the demodulator 33 is to convert to baseband by multiplying e -j 〓 cnT , so the demodulator 3
The output of 3 is (C 1 · α 1 · e j 〓 1 + C 2 · α 2 · e j 〓 2 ) · A o ...(4), and the determiner 34 determines this as A^ o . A^ o
is the estimated value of the transmitted data, and when the system converges, A^ o = A o holds true for almost all n. Therefore, the error signal output E of the subtracter 35
(nT) is E(nT) = (C 1・α 1・e j 〓 1 +C 2・α 2・e j 〓 2 )・A^ o
−A o
(A o ) (C 1・α 1・e j 〓 1 +C 2・α 2・e j 〓 2 −1) A o …(5). The operation of the linear modulator 36 is to convert E(nT) into a passband by multiplying e j 〓 cnT , and the output of the linear modulator 36 is E(nT)・e j 〓 cnT = (C 1・α 1・e j 〓 1 +C 2・α 2・e j 〓 2 −1)・A o・e j 〓 cnT …(6). The values of C 1 and C 2 in the steady state are as follows, where the gains of DC amplifiers 17 and 27 are G, C 1 =<G・X 1 * (nT)・E(nT)・e j 〓 cnT > =G・α 1・e -j 〓 1 (C 1・α 1・e j 〓 1 +C 2・α 2・e j 〓 2 −1) …(7) C 2 =<G・X 2 * (nT)・E (nT)・e j 〓 cnT ＞ =G・α 2・e -j 〓 2 (C 1・α 1・e j 〓 1 +C 2・α 2・e j 〓 2
-1)
…(8) Solving the simultaneous equations of equations (7) and (8) for C 1 and C 2 , we get So, if G≫1, then By substituting equation (10) into equation (2), it can be seen that the amplitude and phase necessary for optimal ratio synthesis are controlled.

The operation of the interference wave removal mode is as follows. Switches S ₁ and S ₂ are on the side, switches S ₃ and
In S ₄ , if one side is on the other side, the other side will be pushed to the side. It is assumed that the switches S ₁ to _{S 4} are controlled by control signals from a code error monitoring circuit (not shown in the figure) connected after the determiner 34 in the figure. There are many methods for detecting presence and generating control signals, which are not directly related to the present invention and will therefore be omitted. To ensure interference removal operation, switch S ₃ and S ₄ are set so that the diversity path experiencing strong interference is on the side and the diversity path experiencing weak interference is on the side (which is used as the reference signal). Although necessary, a simple method may be to try switching and select a good state. As an example, an explanation will be given assuming that switch _S3 is tilted to the side and switch _S4 is tilted to the side, that is, input-1 is less susceptible to interference than input-2. First, between the complex four-quadrant multiplier 29 and the adder 30 (point A in the figure)
Considering the state in which is not connected, the output of the intermediate frequency variable gain amplifier 10 is multiplied by (1 + j0) by the complex 4-quadrant multiplier 19, and the amplitude and phase change because the switch _S3 is turned to the side. Since the switch _S2 is turned to the side, the intermediate frequency variable gain amplifier 31,
After being amplified to a certain level by the AGC amplifier 32, it is demodulated by the demodulator 33, determined by the determiner 34, and outputted as data. At this time, the error signal output from the subtracter 35 is 0 if there is no interference wave at input -1, but if there is an interference wave (provided that it does not cause synchronization in the demodulator 33) ) becomes an interference wave component converted to a baseband, which is reconverted to a passband by a linear modulator 36 and becomes an estimated reproduced interference wave. This estimated reproduced interference wave is added to the multiplication circuit 24, which calculates the correlation (complex number) with input-2 (more precisely, the signal amplified to a certain level by the intermediate frequency variable gain amplifier 20 and AGC amplifier 21). , the complex four-quadrant multiplier 29 controls the amplitude and phase of the output signal of the intermediate frequency variable gain amplifier 20 based on the average value. If we restore the connection at point A assumed at the beginning, a negative feedback loop is formed in the direction in which the error signal output of the subtracter 35 becomes 0, that is, the interference wave included in input -1 is removed. In the converged state, control corresponding to the magnitude of the interference wave included in input -1 is performed, so that the above-mentioned assumption of "to the extent that synchronization does not occur in the demodulator 33" is unnecessary. The above is a qualitative explanation of the operation in the interference wave removal mode, but please refer to Japanese Patent Application No. 55-188705 for details of the quantitative explanation.

As explained above, by using the reception method according to the present invention, space diversity combined reception can be performed in a defense line using a non-line-of-sight communication method during normal times when interference waves can be ignored.
Digital data transmission that performs interference wave removal reception when the strength of interference waves can no longer be ignored, dramatically reducing the probability of communication failure compared to reception methods that do not apply this method. becomes possible.
In addition, this method can perform two types of signal processing, optimal ratio combining space diversity reception and interference wave removal reception, by sharing the same circuit by simply switching a switch.
It is also more economical than conventional similar methods.

[Brief explanation of the drawing]

The figure is a block diagram of the intermediate frequency stage and subsequent stages of a passband optimum ratio combining reception system equipped with an interference wave removal function according to the present invention. Symbol explanation: 10 is an intermediate frequency variable gain amplifier;
11 is an AGC amplifier, 11' is a diode, 12 is a delay circuit, 13 is a complex conjugate circuit, 14 is a multiplication circuit, 15 is a gate circuit or sample/hold circuit, 16 is a low frequency wave generator, 17 is a DC amplifier, 1
8 is a reference voltage generator, 19 is a complex four-quadrant multiplier,
20 is an intermediate frequency variable gain amplifier, 21 is an AGC amplifier, 21' is a diode, 22 is a delay circuit, 2
3 is a complex conjugate circuit, 24 is a multiplication circuit, 25 is a gate circuit or sample/hold circuit, 26 is a low frequency generator, 27 is a DC amplifier, 28 is a reference voltage generator, 29 is a complex four-quadrant multiplier, 30 is a adder,
31 is an intermediate frequency variable gain amplifier, 32 is an AGC amplifier, 33 is a demodulator, 34 is a determiner, 35 is a subtracter, 36 is a linear modulator, and S ₁ to S ₄ are switches, respectively.

Claims (1)

[Claims] 1 In the intermediate frequency stage of a space diversity receiver, a first antenna receives a signal received by one antenna and emits a first output signal amplified to a certain level.
a second automatic gain control means for receiving a signal received by the other antenna and amplifying it to a certain level and outputting a second output signal;
and a first switch for switching the second automatic gain control means to a common mode or an independent mode;
and the amplitude and phase of the second output signal respectively
and a third and fourth control signal controlled by a second control signal.
first and second amplitude and phase control means for generating output signals; combining means for combining the third and fourth output signals; and third automatic gain control for amplifying the combined signal to a constant level. a second switch for switching whether or not the combined signal passes through the third automatic gain control means;
demodulating means for synchronously detecting the composite signal and converting it into a baseband signal; determining means for determining the baseband signal and emitting a fifth output signal; and subtracting the fifth output signal from the baseband signal. a subtracting means for generating a baseband error signal; a modulation means for converting the baseband error signal into a passband error signal; and a correlation between the first and second output signals and the passband error signal. first and second correlation calculating means that calculate, integrate and amplify and generate first and second correlation output signals, respectively; reference signal generating means that generates a reference signal; and the first and second controls. and third and fourth switches for selecting the reference signal or the first correlation output signal and the reference signal or the second correlation output signal as signals, respectively, and when operating in the passband optimum ratio combining mode. , said first
switch to the common mode, the second switch to the composite signal that does not pass through the third automatic gain control means, and the third and fourth switches to the first and second control signals. When operating in interference wave removal mode, the first switch is switched to the independent mode, and the second switch is switched to the side that selects the composite signal. the third automatic gain control means, and the third and fourth switches switch one of the switches to select the reference signal depending on the interference situation; A passband optimal ratio combining reception system with an interference wave removal function that uses the output signal of No. 5 as the data output of the device.