JPS58151755A - Carrier extracting circuit - Google Patents

Abstract

PURPOSE:To obtain a carrier extracting circuit satisfying quick responsiveness and excellent noise eliminating performance, by detecting the phase difference between input and output and adjusting the band of a tuning circuit with the detected voltage automatically. CONSTITUTION:A carrier including noise inputted from an input terminal 1 is led to an output terminal 4 via a tuning circuit 21 the band width of which is changed with a voltae signal from a signal processing circuit 6, and an amplitude limiter 3, and outputted as a carrier having a extracted constant amplitude. A phase detector 5 gives a detection signal of a voltage in response to the phase difference of a signal at input and output terminals to a signal processing circuit 6. Said processing circuit 6 eliminates noise superimposed on the output of the phase detector when noise is superimposed on the input signal and determines the speed of band control of the tuning circuit 21. Thus, a carrier extracting circuit having quick responsiveness just after the burst switching point is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is based on the 51st aspect of the present invention.
The present invention relates to a carrier extraction circuit that extracts x8 wave components.

There is a small device shown in Figure 1 as a device for promoting rice. In Figure 1, (1) is a manual end, (2) is a tuned circuit,
(3) is an amplitude limiter (hereinafter abbreviated as LIMT), and (4) is an output terminal.

Next, the operation will be explained. In Figure 1, the carrier wave containing noise input to the input terminal (1) is transferred to the tuned circuit (2).
Noise components are removed by the out-of-band attenuation characteristic shown in FIG. As the tuned circuit (2), a single tuned circuit is usually used which is advantageous in terms of the transient response characteristics of the tuned circuit described below. What is important here is that the input wave input to this circuit be in the form of a burst. In other words, as shown in Figure 2, the input waves are continuous for a relatively short period of time, and as soon as this ends, the next input wave continues (and so on. In addition, these input waves are emitted from independent signal sources, and their phase relationship is arbitrary.

Next, the response characteristics of the d-sword to this arrogant input wave will be explained. To simplify the explanation, it is assumed that the resonant frequency of the single-tuned circuit and the carrier frequency and number of the first input burst match 2, and that the burst signal was a signal before it was input. Then, the relationship between the amplitude at the input section of the single tuned circuit, the output m and the output section of LIMT (31), and the phase difference between the input (1) of the single tuned circuit and the output (4) of LIMT +31 is as shown in Fig. 8. Next, FIG. 4 shows the relationships when there is a burst whose phase differs by θ degrees immediately before burst b.

As shown in FIG. 8, the manually inputted burst signal is pulled to the output side over time, and it takes a predetermined time to reach a constant amplitude. Also, after the input is cut off, the output is cut off instantly, and the output declines over time. Such characteristics are called transient response characteristics.

When a burst exists alone as shown in Figure 8, the amplitude is kept at one level by the LIMT (31) installed at the next stage of the single-tuned circuit, and no phase difference occurs, so the L
IMT (111 transmission output can be instantaneously obtained when the operation of 31 is within the ideal range.-1 If there is another burst with a true phase immediately before, as shown in Figure 4, First, due to the response characteristics, the two signals are combined at the switching point of the burst, so a phase difference occurs.In other words, immediately after the arrival of the burst) b, the output point is affected by interference due to the residual of the burst) SZ. It takes a certain amount of time for the amplitude to settle to that of b.This means that even if the amplitude is kept constant, an accurate carrier wave cannot be obtained within a certain range due to phase interference. On the other hand, the length of time required for the rise and fall of such a burst is determined by the band of the single-tuned circuit.In other words, if the band is made smaller, the response becomes slower, and if the band is made wider, the response becomes slower. On the other hand, if noise is superimposed on the burst signal, the purpose of this circuit is to remove this noise using the band-limiting characteristics of the single-tuned circuit, so in this respect, a smaller band is better. .

It is natural that this carrier wave extraction circuit is criticized for its fast response (and high noise removal effect).
These two requirements require contradictory conditions for the single tuning circuit, and there is a drawback that it is difficult to simultaneously satisfy the performance of 101g.

This invention was made to eliminate the drawbacks of the conventional ones as described above, and it detects the phase difference between input and output and automatically adjusts the band of the tuning circuit using the detected voltage. The response after the switching point is fast, and in the normal region after that, the noise band ring is made small and the response is fast.
It is an object of the present invention to provide a carrier extraction circuit that can satisfy 10108 of 6 answer performance and excellent noise removal performance.

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

In each of Figure 5, 111, +3+, 14) are the same as the circuits with the same numbers in Figure 's1,
(5) is a phase detector (hereinafter referred to as PSD) that generates a voltage according to the phase difference between input and output, (6+ is PSD
(The output voltage of 51 is full wave! LFF1L, low-pass filtering, level adjustment, etc.)
■ is the tuning circuit (2) in Figure 1.
This is a tuning circuit corresponding to the above, but it is a band-end j-modulation tuning circuit that can change its band depending on the magnitude of the voltage from the signal processing circuit (6).

Next, the operation of the circuit of the present invention will be explained. In FIG. 5, the operations of circuit elements (1) to (4) are similar to those in FIG. It is similar to Phase detection connected to input terminal (1) and output terminal (4)! ! (51 is the signal of the input terminal (1) and the output terminal (
4) Generates a voltage proportional to the phase difference with the signal. That is, in the state shown in FIG. 4, a voltage equivalent to that shown in FIG. 4(d) is generated at its output terminal. This voltage is the signal processing circuit (6)
and full-wave rectification. This is because the voltage of the phase detector (5) may be generated both positive and negative depending on the positive or negative value of θ, so that the absolute value is generated regardless of whether the voltage is positive or negative. The absolute voltage proportional to the phase difference obtained by full wave ** is next (ζ low-pass filtered and processed into a brutal voltage flJi for controlling the tuned circuit (company), and then the same circuit ( The tuning circuit is supplied with a control voltage, and when the voltage is high, the bandwidth is increased, and when it is low, the bandwidth is decreased. The low-pass filter included in the signal processing circuit (6) detects the phase detection R when noise is superimposed on the burst.
! 1 (51), it serves to remove noise components that are similarly superimposed on the phase difference voltage at the output of 51, and to determine the speed of control for changing the band.

As described above, since the band of the tuned circuit is automatically controlled according to the phase difference between input and output, in the circuit shown in Fig. 5, each state in Fig. 4 is indicated by a broken line. The words become easier to understand. In other words, at the burst clean-up point [the bandwidth of the tuning circuit is increased only later, and the response characteristics are accelerated.
1. In a steady state, the bandwidth can be reduced to ensure the noise removal effect.

Next, other embodiments of the present invention will be described. Above,
The present invention can be applied to a carrier extraction circuit in which the center frequencies of each burst are approximately equal and approximately coincide with the central frequency of the tuned circuit. In the following, a case will be described in which the present invention is applied to a circuit in which the center frequencies of each burst are relatively immersed and are vulnerable to being detuned from the same ll1m1 wave number of a tuned circuit. FIG. 6 is a diagram showing a conventional example of a carrier extraction circuit using a tuning circuit in such a case, and FIG. 7 is a diagram showing an example of a circuit to which the present invention is applied to this.

In FIG. 6, (1) to (5) are equivalent to the circuits with the same numbers in FIG. 5, and (71, (
81 is a frequency fuIller (hereinafter abbreviated as MIX), (9
) is a positive/negative peak holding circuit (hereinafter abbreviated as IP-HOLD)
, (1. is a loop filter (hereinafter abbreviated as LF), however, is a voltage controlled oscillator (hereinafter abbreviated as ■CO).

First, referring to FIG. 1, we will discuss a problem that occurs when a signal whose frequency is out of tune with respect to the tuning frequency of a single tuning circuit is input. FIG. 8 shows the input frequency characteristics (f7A(1)) and phase characteristics (FIG. 8(b)) of the unidirectional #j4 circuit (2). That is, the input frequency is the same frequency f of the opening circuit. If m1iai is increased by Δi, then Δf
, =Q, the amplitude is attenuated by Δma, and an input/output phase ljθ is generated. In other words, when applying the noise removal effect to the characteristics shown in FIG. 2(a), a contrast in amplitude and a phase error between input and output occur, making it difficult to accurately extract #& transmission waves. There is a conventional circuit shown in FIG. 6 which eliminates the above-mentioned problem by controlling the input frequency to the tuning circuit so as to always maintain it at the same frequency even when the input frequency changes.

This will be explained next. It is now assumed that the input terminal ψ pot frequency fin(7) signal in FIG. 6 is input. Also, the oscillation frequency of the VCO and song at this time is fL ・Single tuned circuit (2
) is the same frequency as i. Binding, mixer (7), +81
Assuming that sideband waves on both sides) are output, the frequency relationship of each part is ζ as shown in Fig. 46.

That is, the input signal fin is input to the mixer (7) by LL'in
After being changed in frequency to Now, assuming that tL 'in matches the same frequency f0 of the single-tuned circuit (2), the output signal (
The output appearing in 4) is the same as in FIG. 1 when the input frequency matches the same waMil wave number.

Next, a case where fln is reduced to only Δ'' will be explained.

In the case of Jin, the output frequency of the mixer (7) is 'L-('in ten) f), and the output frequency at the output Mizuki (4) is IL-(it, -(fi, +7f))-fthn+
However, in this case, since the input frequency of the single tuned circuit (2) is separated by Δi, the same problem as that which occurred in the circuit shown in FIG. 1 described above occurs. Here, the automatic frequency control JI/''-type (hereinafter abbreviated as AFC) shown in FIG. 6 will be briefly explained.

In Fig. 6, the input signal of the single tuned circuit (2) and the L
I MT (31cD output power soh sott branch g shr P
, S D +53. P.S.
D(5) is a voltage proportional to the phase difference between both input terminals, that is, in the above example, the input frequency is 111i1i1t with respect to the tuning frequency, so the voltage corresponding to Δθ in Fig. 8 is Occur. This voltage is the next IP-HOLD
(91 is held for a certain period of time, and it passes through L P (ll) and is supplied to vcoaJJ.
It is controlled in the direction of 10Δf. i by valve control voltage
If L changes by 4i'', the output frequency of mixer (7) is (fL + Δf') - Cfin + jf) - fL
-fi+f-Δf. Since such control is repeated intentionally, it is finally controlled until it reaches approximately Δf 'mΔi, and the output frequency of the Bunkisa (7) does not become equal to the input frequency, but 'L'in, that is, f . The frequency is maintained at the same frequency.

Therefore, the output trend (4) always provides an output with the defects caused by jlJ removed. The above is a brief explanation of a conventional example of a carrier extraction circuit using a tuned circuit when the input frequency is liquefied. However, this circuit also has a drawback when the weak burst-like signal shown in FIG. 2 is input.

Next, this will be briefly explained. FIG. 9 shows an example of the output voltage of the PSD when several burst signals as shown in FIGS. 1 and 2 are applied to the input terminal. In Figure 9, (λ
) is the input burst, and (b) is, for example, the P S in Fig. 6.
This is an example of the PSD output voltage when the output of D f5+ is disconnected and the AFC effect is eliminated. In Fig. 6, for burst m, the input frequency of the tuning circuit (2) is equal to the tuning frequency. It shows that the value is quite high for burst b, slightly high for burst b, and slightly low for burst C.

C-shaped mtr P 8 D (51) Output IF-)i
oLl) (When 931m is connected, that is, when AFC is applied, the output voltage of PSD (5) is as shown in Fig. 9 (C)
This shows that the AFC is working and each burst is tuned to the tuning frequency on average. This is because in the IP-HOLD circuit (9), the voltages of ■1 and ■maro in FIG.

This is the icing caused by AFC which reduces the temperature to 0■.

An example of the IP-HOLD circuit (9) is shown in FIG.

In the figure, IN is an input end, and OUT is an output end.

The above is a case where AFC acts ideally on burst input. By the way, in Fig. 9 (bJ I (C)), the transient response characteristics of the single-tuned circuit mentioned above are ignored, and when this effect is taken into consideration, the Psp output voltage when the actual AFC is turned off is It is clear that an example is as shown in the figure (d). In the figure (d), the absolute values of the positive peak value v1' of the PSD output and the negative peak values Center voltage V.

becomes Oy, and no control is performed even if AFC is applied. Generally, to eliminate this drawback, the IF-1 phantom LL) circuit (
As shown in Figure 1O, 9) includes a low-pass filter (91), which is used to reduce the pulse-like voltage caused by the transient response.1P-HULL in the case of B) I
S (9b) Ktmf) tli type C$ 10 Figure (
The DAM waveform) looks like the dotted line in FIG. 9(d). In this way, the waveform can be approximated to some extent as shown in (b) of the same figure, or if the burst length is short, the control component will be filtered out by the low-pass filter (9), so the limit There is. FIG. 7 shows a circuit which utilizes the effects of the present invention to eliminate the above-mentioned drawbacks, provides more accurate AFC operation with respect to input burst frequency reversion, and quickly extracts a carrier wave.

Figure 97 shows the signal processing circuit (6) in Figure 6 as PS.
L) Connect to the output terminal of L51 and connect the alarm circuit (2
) is compared to the band tuning circuit (2).

That is, this is an application of the configuration of the present invention described above, and its operation is as already described.

Therefore, in the jI7 diagram, the waveform corresponding to FIG. 9(d) becomes as shown in FIG.
Because the ring becomes narrower, the low-pass filter Is (91) included in IP-)10LD (9) causes the ring in Figure 9 (
It is clear that the waveform b) can be obtained and a more accurate AFC effect can be obtained.

As described above, according to the present invention, when the noise superimposed on a negative burst carrier wave is removed by a tuned circuit (generally a single tuned circuit) and the carrier wave component is extracted, the switching point of the burst is Since it is configured to control the band of the same circuit using the phase difference between the input and output that occurs, it is possible to realize a carrier wave extraction circuit with fast response characteristics (and high noise removal efficiency).

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional carrier wave extraction circuit using a tuning circuit. FIG. 2 is a diagram showing an example of a burst-shaped input signal wave targeted by the present invention. A diagram showing the signal status of each part in the diagram,
Figure 4 shows the 8th burst when two close bursts are input.
Figure 5 is a circuit configuration diagram of a carrier extraction circuit according to an embodiment of the present invention, and Figure 1s6 shows a conventional example of a carrier iRa extraction circuit using a tuning circuit for a burst input whose frequency changes. Figures 7 and 7 show a sixth example to which the present invention is applied.
Figure 8 is a diagram showing an example of the amplitude characteristics and phase characteristics of a single tuned circuit. Figure 9 is a waveform diagram of the P8D output to explain s6 diagram and Figure 7. , FIG. 1O is a diagram showing an example of the IP-)10LD circuit used in FIGS. 6 and 7. In the figure, (1) is an input terminal, (3) is an amplitude limiter,
(4) is the output terminal, (5) is the phase detector, (6) is the signal processing circuit, (2) is the band variable tuning circuit, (7) and (8)
is a frequency replacer, (9) is a positive/negative hold circuit, uI is a loop filter, and East is a voltage controlled oscillator. Note that the same reference numerals in the drawings indicate the same or corresponding parts. Agent Makoto Yomo - □ Figure 1 Figure 2 □ Time &) 3 Figure 4 It's time to open the temple F [Kozue - 9] Figure 8 Figure 6 Figure 7 Commissioner of the Japan Patent Office 1. East r'l-No 1i Shows IQ (1195
7 35398'! 2. Surprising name of carrier wave extraction circuit 3. To Mr. Jin, representative of the Wandering +lt, Mr. Hitoshi Katayama. 5. Detailed explanation of the invention column 2 of the specification to be amended.
, and drawings (Fig. 4(b), Fig. 6, Fig. 7) 6. Contents of amendment (1) “Signal processing circuit (6)” from page 6, line 20 to page 7, line 1 of the specification A low-pass filter is included in the burst filter.
The signal processing circuit (6) includes a low-pass filter, which corrects the burst signal. (2) Page 8, line 7 of the specification, page 10, line 14. Page 12, line 1, lines 5-6, line 9, line 20. “Correct IP-HOLDJ to [±P-HOLDJ” in lines 3 and 4 of page 13, line 20, and line 7 of page 15. (3) Figure 4 (b), Figure 6, and Figure 7 is corrected as shown in the attached sheet. End of Figure 4 P2- Figure 6 Figure 7

Claims (1)

[Claims] +11 A carrier wave extraction circuit that removes the noise component of a burst-like input wave containing noise and extracts a carrier wave, which includes a band p' front tuning circuit to which the burst-like input wave is input, and a band p' front tuning circuit for this band -' hair tuning circuit. IL that limits the amplitude of the output of the circuit
[i limiter, a phase mapper that compares the phase of the output of this amplitude limiter with the phase of the burst-like input wave, and a circuit that processes the output of this phase ai limiter and processes the output of the above-mentioned band iJj table. 1. A carrier wave extraction circuit comprising: a signal processing circuit for inputting a band control signal to the carrier wave extracting circuit;