JPS60122A - S/n improving circuit - Google Patents

Abstract

PURPOSE:To eliminate undesired signals of a nearby station by modulating the amplitude by the output passed through an LPF for the envelope curve signal of the carrier wave information signal and delivering the difference signal between the output of said amplitude-modulated wave and the output obtained by amplifying the carrier wave information signal by an approximately linear amplifier. CONSTITUTION:A carrier wave information signal X mixed with an interference signal having high resistance to the information signal is passed through an input terminal 1 and supplied to an envelope curve wave detecting circuit 2, a limiter circuit 4 and a linear amplifier 7 respectively. The signal X is limited 4 and turned into a signal C. The higher harmonic component of the signal C is eliminated by a BPF5, and a signal D containing a carrier wave having approximately fixed amplitude is extracted. While the output A subjected to the envelope curve wave detection through the circuit 2 passes through an LPF3, and the amplitude of the signal D is modulated by an amplitude modulating circuit 6 with the output A. In this case, the interference wave is suppressed by the LPF3. Then the amplitude-modulated output E and the output F of the amplifier 7 are applied to a differential amplifier 8, and a difference signal Z is delivered.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an SN ratio improvement circuit for removing unnecessary signals of the other party's power when wireless stations in close proximity to each other interfere with each other.

When attempting to transmit information on a carrier wave, there are often interference signals around the carrier wave frequency. Mutual interference in mobile broadband soda also
Mutual interference occurring between two adjacent stations in spectrum mobile communication systems is an important problem in the use of spread spectrum. Conventionally, as a circuit for removing such interference waves, PLL (PI+ase-Lock-
There are methods using filters (Loo1+) and methods using filters, but interference passing in a relatively narrow band is the only way to remove them. Also, a circuit that combines linear and nonlinear amplifiers has been proposed, but this circuit has the drawback that it is almost ineffective in removing interference waves when the input noise amplitude approaches the Lehre distribution.

The present invention is a species that effectively combines linear and non-linear amplifiers, eliminates the above-mentioned drawbacks, and eliminates manual miscellaneous r1.
SN that can effectively eliminate and suppress interference waves regardless of amplitude distribution
The present invention attempts to provide a ratio improvement circuit.

1. Hereinafter, embodiments of the SN ratio improvement circuit according to the present invention will be described with reference to the drawings.

In the tIS1 diagram, the information signal S(1,)coslωo
10 θs (strong in January) 4-step signal I (t) cos (
ω. The carrier wave information signal X in which E→-θ, (t)l is mixed is passed through the input terminal j'. ) respectively. First, in the limiter circuit 4, the signal X is strongly limited to become the signal C, and the harmonic component of the signal C generated in the limiter circuit 4 has the angular frequency ω of the carrier wave.

A signal containing a carrier wave having a substantially constant amplitude is extracted by a bandpass filter 5 having a center.

In addition, the output A whose envelope was detected by the envelope detection circuit 2 is
Further, the signal passes through a low-pass filter 3, and the output B is used to amplitude-modulate the signal in an amplitude modulation circuit 6 (or multiplier). At this time, the low-pass filter 3 plays an important role in suppressing interference waves. The amplitude modulated output E and the roughly linear output F of the amplifier 7 are added to the difference circuit 8, and the difference signal 2 between both signals is outputted to the output terminal 9.''Theoretically consider the circuit shown in Figure 2, f51. I'll try it. The input X in Figure 1 is: X = 5(L)costω, L+θ5(t)l+I
(t)X cos(ωoL+θ (L)l −(1,)
■ It can be expressed as. At this time, the envelope detection circuit output A is A - No/No L) + 12 (L) + 28 (ilT7 plane. Let's now consider a case where the interference signal is relatively large compared to the information signal. Therefore, S (L) << I
(+,) ...(3) is t&v, tsu. At this time,(
2) The formula is approximately 1, A L, ](t,) +5(L
)cosi θ5(t)−θI(L)1・(4) U′. , the interference signal has an amplitude of 1(1) and a frequency band of 5(L)cosiθS([
) - θI (l) Consider a case where the frequency band is very small compared to the frequency band of
(This is often the case when the signal is subjected to high-speed phase modulation or frequency modulation7. In such a case, the envelope detection signal A is suitable for 1'!
When the signal is passed through a low-pass filter 3, it is possible to almost remove the component of the second term on the right side of (.1). Approximately, the external output B can be expressed as Aiso I (1) ... (5).

On the other hand, the signal χ is strongly limited by the limiter circuit 4, and further reduced to the angular frequency ω by the bandpass filter 5.

The output when extracting only the vicinity of is bar 1'17
Approximately expressed by the main component of the transmitter output, it becomes D −□ × (6). Considering the conditions of equation (3), equation (6) can be approximately expressed as
・-(7). Denozuki) is amplitude-modulated by the signal of Denozuki 3.

Therefore, the output E after modulation is calculated by multiplying equation (5) by equation (7).

x costωot+2θ1(t)−θ5(t)l]
=19) Final output Z obtained at output terminal 9 in Figure 1
is the difference signal between the input signal X and the signal D obtained by passing the input signal X through a substantially linear amplifier. At this point, the output Z becomes approximately linear/(by adjusting the amplification degree of the amplifier 7 so that the interference signal can be removed as much as possible);
13( +5(L)costωot+ 2θ1(1)−θS(+
,)1...(41)). Here, the signal-to-noise ratio (S
Looking at the input 5IR (= 1g i)
n) is I'? in = <S”>/<I2>. However, > indicates the average value. Also, S I R (
= RouL) is Rout from equation (10), = <S
:'>/<s2>=1. Therefore, the degree of improvement in SIR between human power and output is as follows: 1 = Rout/Rin = <12>/<82>, and the smaller the SIR of input, the greater the degree of improvement can be expected.

As explained above, according to the SN ratio improvement circuit of the present invention, effective processing is performed by combining linear and non-linear amplifiers, so , which removes unnecessary signals from nearby stations.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the SN ratio improvement circuit according to the present invention, and FIG. 2 is an explanatory diagram showing the characteristics of an envelope detection signal of an input signal. 1...Input terminal, 2...Envelope detection circuit, 3...
Low-pass filter, 4... Limiter circuit, 5... Band-pass filter, 6... Amplitude modulator, 7... Sublinear amplifier, 8... Difference circuit. Patent applicant Director of Technology Research Headquarters, Defense Agency Yukie Inumori Agent Patent attorney Takashi Kai

Claims (1)

[Claims] (1) Limit carrier wave information signals mixed with interference waves.
The signal obtained by passing through the vine circuit and the harmonic removal filter is amplitude-modulated by the output of the envelope detection signal of the carrier wave information signal passed through a low-pass filter, and this amplitude modulated wave output and the carrier wave information signal are An SN ratio improvement circuit characterized in that it outputs a difference signal between an output amplified by a nearly linear amplifier.