JPS6249727A - Adaptive-antenna receiver - Google Patents

Abstract

PURPOSE:To obtain a high-performance mobile communication receiver, by providing two receiving antennas and automatically performing interference suppression of diversity reception or disturbing signals in accordance with signals received by the receiving antennas. CONSTITUTION:Signals S1(t) and S'2(t) outputted from a complex multiplier circuit 1 are inputted to and combined by a signal combining circuit 8 and a signal Z(t) is outputted from the circuit 8. The output signal Z(t) is given to an FM receiving circuit 9 and square-low detecting circuit 10. Part of the output signal Z(t) is fetched to an output terminal 11 as a receiving signal after passing through the FM receiving circuit 9. Moreover, another part of the output signal Z(t) is fetched by the square-low detecting circuit 10 as a detection output signal D(t) and the signal D(t) is divided into two parts and respectively inputted to a low-pass and high-pass filters 12 and 13. When a disturbing wave exists at the output terminal 11 of the FM receiving circuit 9, the disturbing wave is suppressed and only desired waves are outputted. The signals received by two receiving antennas 2 and 3 in relation with the desired waves are in-phase combined.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an adaptive antenna receiver that is most suitable for mobile communication, and in particular suppresses interference waves when they are present.
When there is no interference wave, in-phase synthesis diversity
The present invention relates to an adaptive antenna receiver that performs.

[Prior art and its problems]

In mobile radio communications used in mobile bodies, problems include deterioration of received signals due to fading and interference due to jamming signals. Conventionally, a diversity reception branch '1tti has been developed to deal with the deterioration of a received signal due to fading, and an interference suppression technique has been developed to deal with interference caused by a jamming signal. Both techniques utilize two receiving antennas and automatically perform necessary control by processing signals output from the two receiving antennas. However, in the past, each of the above techniques was applied separately and operated independently;
No method has been proposed that applies two techniques simultaneously. Therefore, if techniques in these two fields can be used in combination based on the same control algorithm, it will be more useful as a receiver in mobile communications, for example.

[Purpose of the invention]

An object of the present invention is to meet the above-mentioned requirements, and includes two receiving antennas, and automatically performs diversity reception or interference suppression of interference signals according to the state of signals received by these receiving antennas. An object of the present invention is to provide an adaptive antenna receiver with improved performance as a mobile communication receiver.

[Structure of the invention]

The present invention includes first and second receiving antennas, and the first and second receiving antennas are connected to at least one of the first and second receiving antennas, and the amplitude and the amplitude between the received signals of the first and second receiving antennas are controlled by a control signal. A complex multiplication circuit that controls the phase relationship and outputs two output signals, a signal synthesis circuit that synthesizes the two output signals of this complex multiplication circuit, and demodulation by inputting a part of the output of this signal synthesis circuit. a square-law detection circuit that inputs a part of the output of the signal synthesis circuit;
A high-pass filter and a low-pass filter each input the output of the square-law detection circuit, and a signal obtained by adding a DC signal to the output signal obtained from the high-pass filter is used as the output signal of the low-pass filter. A division circuit that performs division;
a low frequency signal generation circuit that generates orthogonal first and second low frequency signals; a first correlation circuit that calculates a correlation between the output signal of the division circuit and the first low frequency signal; a second correlation circuit that calculates a correlation between the output signal and the second low frequency signal; and a second correlation circuit that subtracts the first low frequency signal from the output signal of the first correlation circuit, and obtains a signal of 1st order as the control signal. a first subtraction circuit that outputs the signal as the control signal to the complex multiplication circuit; and a signal obtained by subtracting the second low frequency signal from the output signal of the second correlation circuit and outputting it as the control signal to the complex multiplication circuit. It is characterized by comprising a second subtraction circuit.

〔Example〕

The present invention will be described in detail below using the drawings.

FIG. 1 is a block diagram of a receiver according to the present invention. In this figure, 1 is a complex multiplication circuit, and the complex multiplication circuit 1 connects two receiving antennas 2.3 through input terminals 101.102.
Equipped with Receiving antennas 2 and 3 each receive a signal s+(t
), 52(t). Further, control signals α(t) and β(1) are inputted to input terminals 103 and 104 from the subtraction circuit 4.5, respectively. Such a complex multiplication circuit 1 is realized, for example, as shown in FIG. In FIG. 2, 6 is a variable gain amplifier, 7 is a variable phase shifter, the control signal α(1) is input to the variable gain amplifier 6, and the control signal β(1) is input to the variable phase shifter 7. . In the complex multiplication circuit 1 configured in this way, - for example, the input terminal 10
The signal 5l(t) input from 1 is sent to the output terminal 10 as it is.
The signal 52 (
t) is amplified in amplitude by the variable gain amplifier 6, its phase is controlled by the variable phase shifter 7, and outputted to the output terminal 106 as the signal S'2(t).

Therefore, in this case, the amplitude and phase of the signal 52(t) are controlled by the control signals α(t) and β(1), which controls the relationship between the amplitude and phase of the signals S+(t) and 52(t). will be done.

A signal 5l(t) output from the complex multiplication circuit 1.

S'2(t) is input to the signal synthesis circuit 8, where it is synthesized and a signal Z(t) is output. This output signal Z(t
) is given to the FM receiving circuit 9 and the square law detection circuit 10. A part of the signal Z(t) passes through the FM receiving circuit 9 and is then outputted to the output terminal 11 as a received signal. Also, signal 2 (1
) is output by the square law detection circuit 10 as a detection output signal D(
t), and this signal D(t) is then branched into two, a low-pass filter 12 and a high-pass filter 1.
3 is input. The signal L(t) obtained by the low-pass filter 12 is directly input to the division circuit 14. The signal obtained by the high-pass filter 13 passes through the square-law detection circuit 15 and becomes a signal H(t), and then the adder circuit 16
The signal is added to the DC signal of level ε0 provided from input terminal 17 at , and then input to division circuit 14 . The division circuit 14 outputs an output signal C(t).

18 and 19 are correlation circuits, and the correlation circuit 18 has the above C(t
) and the output signal ε cos ωt of the low frequency oscillation circuit 20 are input, and the above C(t) and the output signal ε sin ωt of the 90° phase shift circuit 21 are input to the correlation circuit 19 . The low frequency oscillation circuit 20 and the 90° phase shift circuit 21 are the low frequency signal generation circuit 2.
Configure 00. Specifically, the correlation circuits 18 and 19 include a multiplier 22 and a low-pass filter 2, as shown in FIG.
3 and a loop filter 24.

The multiplier 22 has two input terminals 22a and 22b, and the input terminal 22a receives the signal C(t), and the input terminal 22b receives εcosω or εsinωt, respectively.

Signals α from correlation circuits 18 and 19, respectively. .

β. is output and input to the subtraction circuits 4 and 5.

Furthermore, the above-mentioned εcO5ωt is applied to the subtraction circuit 4.5.

ε sin ωt are respectively input, and as a result, control signals α(t) and β(1) are outputted to the complex multiplication circuit 1 as described above. In this case, α(t) and β(1) are α(t)
=α. −εcoswt β(t)=β. −εsinωt. Here, ω above is the frequency of the low frequency signal, ε
is a small positive number (ε(1)).

Next, the operation of the receiver having the above configuration will be explained while expressing the signals of each part of the circuit using mathematical expressions.

First, the received signals 5I(t) and 52(t> are expressed as follows.

S, (t)=D+(t)+U+(t)...
・(1) 32(t)=D2(t)+tJ2(t)
...(2) Here, Dt(t), D2(t
) are desired wave signals received by the receiving antenna 2.3, and u+(t) and u2(t) are interference wave signals.

Dt(t), D2(t), u,(t).

U2(t) can be further expressed as follows.

Dt(t) = A, exp (j(ωct+θ(1)
+θ, ))...(3) D2(t) = A2eXp(j(ωct+θ(1)+
θ2))...(4) 'J + (t) -B IeXp (J (ω
ct + φ (1) + φ 1) )...(
5) U2(t)−B2exp(J(ω.t+φ(1)+φ2
))...(6) Here, it is assumed that the received signal is an FM modulated wave, and AI, A2. Bl and B2 are amplitudes, ω.

is the carrier wave frequency, θ(t) and φ(1) are the phase signals determined by the modulation signals of the desired wave and the interference wave, respectively, and θ1°θ2.
φ1. φ2 is a phase constant. The above amplitude and phase constants change slowly due to fading.

Next, the signal S whose amplitude and phase are controlled by the complex multiplication circuit 1
'2(t) is expressed by α(t>, β(1)) as follows.

S' 2(t) = α(t) (02(t) +U
2(t) ) exp(jβ(t))...(7) As a result, the output signal 2(1) of the signal synthesis circuit 8 becomes z(
t) =S+(t) +s' 2(t)=[AIe
xp(Jθ1) 1 α (t)A26XI] (j(θ 2 + β
(1n)), )exp(jθ(t)) + CB+exp(Jθυ + α(t)B2exp (j(θ2+β(1))
)]expUφ(t))...(8) Also, the detection output signal D(t) is D(t)
= l 1Ct) + 2 = IA(t)12+ IB(t)12+2 l A(
t) l l B(t) l cos (φ(1)−
θ(1) ten ψ, (t) − ψb(D)...(9), where l A(t) l ''=A, 'ten α2(t) A2 '+
2α(t)A, A2cos (θ2−θ1+β(1)
)...(10) l B(t) l 2=8. '+α2(t)L''+2α
(t) BI32CO9 (θ2-01+β(t))...
・(11) ...(12) ...(13).

Among the detection output signals D(t), if the frequency of the low frequency signal is sufficiently low, l A(t) l
2+l B(t) l 2 becomes the low frequency signal, and the remaining 21 A(t) l l B(t) l cos(φ
(1)-θ(1)+ψ, (1)-ψb(t)) is a signal that extends to the high range due to FM modulation.

Therefore, the output signal L(t) of the low-pass filter 12 can be approximated as follows.

L(U= l A(t) l 2+l B(t) l
2#A0'+Bo" +2α.εA2 C(A2+AlC03(θ2-θ1+
β. )) cosωt−A, sinωt] +2α. ε82 C(82+B, C03(θ2-θ, ten β.))cos ωt-B, sin cut)...(14) Here, Ao2=A, 2+α. 2A2 +2α. A, A2cos(θ2-θ1+β0)...(
15) BO"=BI'10α.2B2'+2α.B,B2cos(θ2-θ1+β.)...(
16). On the other hand, the signal H(t) generated by the high-pass filter 13
is H(t)-l A(t) l 21 B(t) l 2
z A 02 B 02 +2α. εAOB2 C(B2+B+cos(θ2−θ
1+β. )) coscc+t-B, sinωt] +2α. εBOA2 [: (A2+A, cos(θ2
−θ1+β. )) cosωt−A, sinωt] (17) It is approximated as follows.

The output signal C(t) of the division circuit 14 is approximated as follows using L(t) and H(t) obtained as described above.

ζ [A, "+80"Ao"+80' +2α. εAOB2 (B, □cosa+t-B, si
nωt)+2αoEBoA2(A+2C(lsaJt-
A, 5 incut)...(18) Here, Al1 = A2 + A, cos(θ2-θ1+β.)
...(19)B12 =82+B, cos(θ
2-θ1+β. )...(20).

The signal C(t) obtained as above is sent to the correlation circuit 18.
19 and input the low frequency signals jcosω and εsinω
Correlate with t. Correlation signal Cc between signal C(t) and εcosωt, correlation signal Cs between signal C(t) and εsinωt
is given as follows.

...(21) ...(22) In the above, the correlation signals Cc and Cs are α for α(1) and β(1) of the signal C(t), respectively.

and β. It represents the partial differential coefficient in the vicinity, with its sign reversed. Signal c < t > Ha, β. As a function of β, it has a downwardly convex shape as roughly shown in FIG. 4, and gives a minimum value. exists. β
. The sign of the partial differential coefficient differs depending on whether Cs is larger or smaller than β, and by inputting the signal Cs to the loop filter 24, the control signal β0 gradually reaches the optimum value β. approach. Similarly, α.

The value of also approaches the optimal value αi. Predetermined DC signal ε
. If the value of is set to a sufficiently small value, α. and as β0 approaches the optimum value, Ao'Bo' becomes zero, that is, 80 or B. approaches zero. This A. As is clear from definitions (15) and (16), Bo are the square of the amplitude of the desired wave (first term) and the amplitude of the interfering wave (second term) shown in equation (8), respectively. It represents the square of . Therefore, ε. When the value of is sufficiently small, the signal synthesis circuit 8
In the output signal Z(t) of , the interfering wave or the desired wave is canceled. As a result, at the output terminal 11 of the FM receiving circuit 9, when an interference wave exists, this interference wave is suppressed,
Only the desired wave is output. There is no problem if the interfering waves are canceled, but if the desired waves are canceled, a means for forcibly changing the system to another state is required.

For this purpose, as is conventionally known, the phase control amount β is required.

The most effective method is to invert the sign of .

When there is no interference wave, that is, Bl=82-B0=
When 81°=O, equations (21) and (22) become zero except for the third term in parentheses. At this time, the signal Cc,
Cs is A given by equation (15). α of ′.

and β. The sign of the partial differential coefficient at is reversed, and the optimal values α, β6 are A. ′ is maximized.

Maximizing A02 means at least in-phase combining the signals received by the two receiving antennas 2.3 regarding the desired wave expressed by the first term of equation (8). Note that the constant ε. When the interference waves are canceled (A, 'B, "= 0), the third term in equations (21) and (22) also becomes zero, and the control force for in-phase synthesis becomes zero. Therefore, the object of the present invention cannot be achieved.

As described above, the method of determining the correlation by superimposing a sinusoidal minute signal in order to determine the minimum value of the evaluation function is known as the perturbation method. The frequency ω of the perturbation signal is 1001(z to 200)1 for analog audio signals.
It is desirable to set it to z. The fading frequency that normally occurs in mobile communications is several tens of thousands, so this value must be higher than this, and the lower limit of the audio frequency band is 300.
It is determined by the condition that it is lower than seven.

Further, in the above embodiment, it is assumed that the signal component of the frequency ω can be sufficiently attenuated by the high-pass filter 13, but if this is not satisfied, it is desirable to provide a band rejection filter of the frequency ω in addition to the high-pass filter 13. .

〔Effect of the invention〕

As is clear from the above description, according to the present invention, diversity reception technology and interference suppression technology are combined, and when interference waves exist with respect to the desired wave, the interference waves are canceled and only the desired wave is extracted. 2 when there is no interference
Since it is configured to perform in-phase composite diversity reception on desired waves from two receiving antennas, it has the effect of exhibiting extremely high performance when used as a mobile communication receiver.

[Brief explanation of drawings]

1 is a block diagram showing the configuration of a receiver according to the present invention; FIG. 2 is a block diagram showing a specific configuration of a complex multiplication circuit; FIG. 3 is a block diagram showing a specific configuration of a correlation circuit; The figure is a conceptual diagram for explaining the operation. 1- Complex multiplication circuit 2.3 ...... Receiving antenna 4.5
・・・・・・・・・ Subtraction circuit 8 ・・・・・・
・・・ Signal synthesis circuit 9 ・・・・・・・・・
FM receiving circuit 10 Square-law detection circuit 12 ... Low-pass filter 13
...... High pass filter 14
・・・・・・・・・ Division circuit 16 ・・・
・・・・・・Addition circuit 18.19 ・・・・・・
... Correlation circuit 200 ... Low frequency signal generation circuit agent Patent attorney Yoshiyuki Iwasa S+ (t) 52 (t) S'2 (t)' Figure 2 Figure 3

Claims (1)

[Claims] (1) first and second receiving antennas, and the amplitude and phase between the received signals of the first and second receiving antennas connected to at least one of the first and second receiving antennas according to a control signal; A complex multiplication circuit that controls the relationship between a square-law detection circuit that inputs a part of the output of the signal synthesis circuit; a high-pass filter and a low-pass filter that input the outputs of the square-law detection circuit, respectively; and the high-pass filter. a division circuit that divides a signal obtained by adding a DC signal to an output signal obtained by the low-pass filter by the output signal of the low-pass filter; a low-frequency signal generation circuit that generates orthogonal first and second low-frequency signals; a first correlation circuit that determines the correlation between the output signal of the division circuit and the first low frequency signal; a second correlation circuit that determines the correlation between the output signal of the division circuit and the second low frequency signal; a first subtraction circuit that outputs a signal obtained by subtracting the first low frequency signal from the output signal of the first correlation circuit to the complex multiplication circuit as the control signal; and a second subtraction circuit that outputs a signal obtained by subtracting the second low frequency signal from the output signal to the complex multiplication circuit as the control signal.