JPH0435547A - Interference wave eliminating device - Google Patents

Abstract

PURPOSE:To eliminate the multipath distortion without damaging the diversity effect by providing a second adder which synthesizes the output signals of first and second matching filters and a discrimination feedback equalizer which equalizes the output signal of the second adder. CONSTITUTION:This device consists of AGC amplifiers 1, 2, and 8, multipliers 3, 4, 9, and 10, correlators 5, 6, 11, and 12, adders 7 and 17, subtractors 13 and 14, matching filters 15 and 16, and a discrimination feedback equalizer 18. Diversity reception signals are so synthesized that interference waves received through diversity routes have the same phase, and the level of a desired wave is suppressed to extract interference wave components, and inferred interference waves generated form these interference wave components are subtractored from reception signals of respective diversity routes to eliminate a strong wide-wave interference wave. Outputs of matching filters 15 and 16 to improve S/N of respective signals are subjected to diversity synthesis, and the synthesized signal is equalized by a discrimination feedback equalizer 18. Thus, the multipath distortion is eliminated without damaging the diversity effect.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an interference wave canceling device, and in particular to a multipath fading line that requires a diversity method.
The present invention relates to an interference wave removal device that performs broadband interference wave removal and adaptive equalization of waveform distortion due to fading when there is a strong interference wave whose /U (desired wave to interference wave ratio) is negative.

(Conventional technology) Conventionally, PSKJ? ? Interference by FM lines, interference or jamming waves from adjacent channels, etc. may pose problems for digital microwave lines using QAM.

In particular, when digital transmission is high-speed, FM interference waves are considered narrowband interference waves, but other interference waves may be broadband interference waves. In addition, diversity methods and adaptive equalization techniques are essential for strong multipath fading lines, and matched filters (MPs) and decision feedback equalizers (DFEs) are used for lines with long propagation distances such as non-line-of-sight communications.
A receiver using this is required. FIG. 3 shows an example of a conventional interference wave removal device that removes broadband interference waves in a multipath fading environment.

In FIG. 3, 301 and 302 are multipliers, 303 is an adder, 304 is a subtracter, and 305, 308, and 309 are AG
C#! 306 and 307 are correlators, 310 is a switch, and 311 is an adaptive equalizer. This conventional interference wave removal device performs double diversity combining of received signals from two routes, and equalizes the combined signal by passing it through an adaptive receiver using an adaptive equalizer (EQL).

Diversity combining is performed by adder 303, and its combining method is maximum ratio combining. Each diversity input of input 1 and input 2 is AGCtI! Width gauges 308 and 30
9 removes level fluctuations due to flat fading,
Multipliers 301 and 302 respectively multiply the signals by complex tap coefficients so that adder 303 performs maximum ratio combining.

These tap coefficients are the output of AGC amplifier 305 after diversity synthesis by correlators 306 and 307, and A
This is the correlation value between the output of the GC @@ device 308 and the output of the device 0809. When there is no interference wave, the switch 310 switches to AGC.
The output of the amplifier 305 is selected and output, and the adaptive equalizer (E
QL) 311 with the received signal. This adaptive equalizer 3
11, waveform distortion due to multipath fading is removed.

In the conventional interference wave removal device shown in FIG. 3, if there is a strong interference wave in the received signal with a wide band D/U ratio (ratio of interference wave to desired wave) f minus, the switching device 310
selects and outputs the output of the subtracter 304. The subtracter 304 subtracts the output of the multiplier 302 from the output of the multiplier 301, and while the adder 303 performs in-phase synthesis, the subtracter 304 performs anti-phase synthesis to remove interference waves. I do.

FIG. 4 shows the interference wave removal operation. (a> and (d)
respectively indicate input 1.2 of diversity route 1.2. Here, the desired wave for each route is 31. S2, and the interference waves are Jl and J2. When the interference waves are large enough to make D/U negative, the interference waves are controlled to be combined in phase, and as shown in (b) and (e), the interference waves J1 are generated at the outputs of the multipliers 301 and 302. and J
2 have the same amplitude and phase. In this case, the output of the adder 303 shown in (c) represents in-phase combination of interference waves. On the other hand, as shown in (f), in the subtracter 304, the interference waves are combined in reverse phase, and the interference waves are removed.
Only the desired signal wave is extracted. However, for Sl and 82, not only maximum ratio combining but also in-phase combining will not be performed. In particular, the desired signal wave may disappear due to the phase relationship between the desired signal S and the interference wave J. When input 1 and input 2 have the same amplitude and phase relationship with S and J as shown in (g) and (J), the outputs of multipliers 301 and 302 are (h)
and (k>).At this time, the output of the adder 303 shown in <i> is also an in-phase combination of S#JJ, and the output of the subtracter 304 shown in (1) is an anti-phase combination of both S and J. In other words, although the interference wave is removed, the desired signal wave also disappears.

(Problems to be Solved by the Invention) In the conventional interference wave canceling device described above, when attempting to remove interference waves, maximum ratio combining or in-phase combining of diversity is not performed for desired waves, so no diversity effect can be obtained. Optimal reception by adaptive equalization on a multipath fading line and interference wave removal are not compatible, and there is a drawback that the desired signal may be lost in some cases.

Therefore, an object of the present invention is to provide interference wave cancellation that can prevent the disappearance of desired waves due to interference wave cancellation, eliminate strong broadband interference waves, and effectively eliminate multipath distortion without impairing the diversity effect. The goal is to provide equipment.

(Means for Solving the Problems) An interference wave canceling device according to the present invention is a combining diversity type interference wave canceling device that sets two routes and combines the received outputs of the respective routes. A first received signal consisting of a desired signal and a first interference wave, and a second received signal consisting of a second desired signal and a second interference wave, are combined with the first interference wave and the second interference wave. A first adder that combines AGC#! so that they are in phase, and normalizes the output signal of the first adder to obtain a normalized signal.
a first correlator that obtains a first correlation value by correlating the first received signal and the normalized signal; and a correlation between the second received signal and the normalized signal. a second correlator that obtains a second correlation value by multiplying the normalized signal by the first correlation value; and a first multiplier that multiplies the normalized signal by the second correlation value. a second multiplier; a first subtracter that obtains a first difference signal by taking the difference between the first received signal and the output signal of the first multiplier; and a first subtracter that obtains a first difference signal; a second subtracter that obtains a second difference signal by taking the difference from the output signal of the second multiplier; and a S/S/ of the first difference signal.
a first matched filter that improves the S/N ratio, a second matched filter that improves the S/N ratio of the second difference signal, and an output signal of the first matched filter and the second matched filter. It is characterized by comprising a second adder that combines the output signals with the output signal, and a decision feedback type equalizer that equalizes the output signal of the second adder.

(Example) Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the interference wave removal device of the present invention. FIG. 2 is a diagram illustrating the interference wave removal operation of the present invention.

In FIG. 1, 1, 2, and 8 are AGC amplifiers, 3, 4, 9, and 10 are multipliers, 5, 6, 11, and 12 are correlators, 7 and 17 are adders, 13 and 14 are subtracters, 15 and 16 are matched filters (MF 118 is a decision feedback equalizer (DFE)).

In FIG. 1, each diversity input of input 1 and input 2 is normalized to have an amplitude of 1 by AGC amplifiers 1 and 2, respectively, and multipliers 3 and 4 are in-phase combined by an adder 7.
are respectively multiplied by complex tag coefficients. These tag coefficients are the output of the AGC amplifier 8 after diversity synthesis by the correlators 5 and 6, and the AGCt! I@ is the correlation value between the outputs of devices 1 and 2. D/U ratio (ratio of interference wave to desired wave) in the received signal of the embodiment shown in Fig. 1 in a wide band
If there is a strong interference wave that makes
The desired wave and interference wave at input 1 and input 2 are respectively 81. J
l, S2. Let it be assumed that J2 is shown as shown in FIGS. 2(a) and (d). Here, the interference waves Jl and J2 are broadband interference waves having arbitrary levels. There is only one source of t, and this interference wave is J, and the interference wave of route 1 is Jl=A1exp (Jφ1) −J ・
Modeled using (1). Here, AleXp(Jφ1)
is the transfer function of root 1 to J. Similarly, for route 2, the interference wave is J2=A2ex11(jφ2)−J・(2
)far.

At this time, the outputs of multiplier 3 and multiplier 4 are (b), respectively.
As shown in (e), the AGC amplifiers 1 and 2 are controlled to perform in-phase synthesis of the normalized interference wave components. Therefore, as shown in (C) in the output of the adder 7, the interference waves J1+J2 have a dominant level compared to the desired waves, and since the desired waves are not combined in phase, their level does not increase much. The output of AG
It is normalized by the C amplifier 8 and becomes as shown in (f). Here, if the interference wave component of route 1 is used as the reference,
The output of the AGC amplifier 8 is Jr=1・eXll(Jφ1)+a (S1+82)・
...(3) It is shown as follows. Here, α is the level reduction rate with respect to the desired wave due to the AGO applied to the interference wave.

Correlators 11 and 12 each receive this normalized interference wave component J
Correlate r with the received signals of routes 1 and 2. This correlation operation is performed by averaging the products of the complex conjugate of the output of the AGC amplifier 8 and each diversity input. Note that the correlation values of correlators 11 and 12 are Wl, respectively.
If W2 is used, it can be shown as follows.

W1=Eth exp(-j φ1) +α(31°+82°))・(Sl +J1)]=^1
・J+Δ1...(4) W 2 =
E[(eXE)(-j φ1)+α(81° +S
2”))・(32+J2)]=A2−exp(
j (φ2-φ1)) J+Δ2 ・(5) In the above equation, A1 and A2 are the correlation values between the desired wave component included in Jr and the desired wave component at the input, but the desired wave component in equation (3) is small with respect to the interference wave, and their correlation components are extremely small. The zero multipliers 9 and 10 multiply the normalized interference wave component Jr by the complex coefficients W1 and W2 of equations (4) and (5). That is, the outputs of multipliers 9 and 10 are respectively (
It is approximated by Jl and J2 shown in equations 1) and (2). This Jl and J2 are shown in Figure 2 (g) and (J).
By subtracting the estimated values J1 and J2 from the inputs of routes 1 and 2, respectively, by subtractors 13 and 14, (h
) and (k), wideband interference waves can be removed for each diversity route of input 1 and input 2. By the way, as shown in (g) and (J), the outputs of multipliers 9 and 10 have desired components W1α(S1+S2) and W2C(
In addition to the original desired waves S1 and S2, as shown in (h) and (k),
−W2C(S1+82) and −W2C(S1+8
2) is added. These components cause interference, but the level is low, and as shown in (1) and (1), MF15 and 16
The desired wave components delayed and dispersed are combined at the maximum ratio at the reference timing. In other words, the S/N ratio is maximized, and M
The outputs of F15 and F16 are subjected to diversity combining by an adder 17. The output of this adder 17 is the DFE18
to remove code amount interference.

Even if the interference waves fluctuate in subsequent operations, the interference waves are adaptively removed and distortion due to multipath fading is also removed.

(Effects of the Invention) As explained above, the present invention combines diversity reception signals so that the interference waves received on each diversity route are in phase, suppresses the level of the desired wave, and extracts the interference wave component. Then, by subtracting the estimated interference wave generated from this interference wave component from the received signal of each diversity route, strong broadband interference waves are removed, and the S of each signal is
By performing diversity synthesis at the output of a matched filter (MF) that improves the /N ratio and equalizing the combined signal with a decision feedback shaper, multipath distortion can be removed without impairing the diversity effect. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the interference wave removal device of the present invention, FIG. 2 is a diagram explaining the interference wave removal operation of this embodiment, and FIG. 3 is a diagram of the conventional interference wave removal device. FIG. 4, a block diagram showing the configuration, is a diagram illustrating the interference wave removal operation of the conventional interference wave removal device. 1.2, 8, 305, 308, 309. ... AGC amplifier, 3, 4, 9, 10, 301° 302... Multiplier, 5, 6, 11, 12, 306° 307... Correlator,
7,17.303...adder, 13.14,304...
...Subtractor, 15.16...Matched filter (MF),
18...Decision feedback equalizer (DFE), 310...
Switcher, 311...Adaptive equalizer.

Claims (1)

[Claims] In a combining diversity interference wave canceling device that sets two routes and combines the received outputs of the respective routes, a first received signal consisting of a first desired signal and a first interference wave, and a second desired signal are combined. a first adder that combines a signal and a second received signal consisting of a second interference wave such that the first interference wave and the second interference wave are in phase; and the first addition. an AGC amplifier that normalizes an output signal of the amplifier to obtain a normalized signal; a first correlator that obtains a first correlation value by correlating the first received signal and the normalized signal; a second correlator that obtains a second correlation value by correlating the second received signal with the normalized signal; a first multiplier that multiplies the normalized signal by the first correlation value; a second multiplier that multiplies the normalized signal by the second correlation value; and a first multiplier that takes the difference between the first received signal and the output signal of the first multiplier.
a first subtracter for obtaining a difference signal, a second subtractor for obtaining a second difference signal by taking the difference between the second received signal and the output signal of the second multiplier; a first matched filter that improves the S/N ratio of the second difference signal, a second matched filter that improves the S/N ratio of the second difference signal, and an output signal of the first matched filter; An interference wave characterized by comprising: a second adder that combines the output signal of the second matched filter; and a decision feedback equalizer that equalizes the output signal of the second adder. removal device.