JPH03145232A - Initial synchronizing signal generator for ss receiver - Google Patents

Abstract

PURPOSE:To attain accurate and sure initial synchronization by outputting an initial synchronizing signal while an output of a main envelope detection circuit exceeds a threshold level signal. CONSTITUTION:A main envelope detection circuit 20A of the same constitution as an envelope detection circuit connects to an output of an amplifier 18, a correlation signal amplified by the amplifier 18 is subject to envelope detection and a main envelope detection signal P is outputted. Moreover, a comparator circuit 22 is connected to the output side of the main envelope detection circuit 20A and a threshold level signal Sc generated from a threshold level signal generating circuit 30 and the main envelope detection signal P are compared. Then while the main envelope detection signal P exceeds the threshold level signal Sc, an initial synchronization pulse (initial synchronizing signal) going to an H level is generated and outputted to a PN code generator of a DLL circuit. Thus, even when fluctuation in the C/N or the level takes place to the input of a correlation device, always accurate initial synchronization is attained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an initial synchronization signal generator for an SS receiver,
In particular, the present invention relates to an initial synchronization signal generation device for an SS receiver that generates an initial synchronization signal using a correlator such as a SAW correlator.

[Conventional technology]

In a 5Siffi signal (spread spectrum communication) receiver, a PN code for de-expansion 11 synchronized with the expanded IFK PN code included in the received SS signal wave is generated by a PN code generator in a DLL circuit, and the SS signal is The nPsK wave is multiplied by the wave and despreaded to form the nPsK wave.

The PN code generator outputs P from the VCO of the DLL circuit.
It advances in accordance with the N clock and then reverse expansion (generates a PN code for 1, but the expansion lit P N code in the received SS signal wave is
In order to synchronize with the code, it is necessary to apply initial synchronization to the PN code generator using a predetermined initial synchronization signal generator.

FIG. 7 shows the configuration of the first 01 synchronization signal generator used in conventional SS receivers.

After the SS signal wave down-converted to a predetermined intermediate frequency is amplified by the amplifier 1O, it is limited to a predetermined bandwidth by the BPF 12.

An AGC amplifier 14 is connected to the output side of the BPF 12, and the output level is kept constant at a predetermined set level regardless of fluctuations in the input level from the BPF 12.

Here, the output of the AGC amplifier 14 contains a noise component and a signal component, but in most cases, the level of the noise component is clearly high in the SS signal wave, so the AGC amplifier 14
In this case, the output noise level is made constant (see the frequency spectrum of the SS signal wave shown in FIG. 8).

On the output side of the AGC amplifier 14, there is an S as an example of a correlator.
The AW correlator 16 is connected, and the preamble part of the SS signal wave is input, and the amplification part 11 of the SS signal wave is input.
When the k PN code and the PN pattern of the SAW correlator 16 match, a correlation signal that reaches a peak is output.

The correlation signal is amplified by an amplifier 18 connected to the output side of the SAW correlator 16.

Here, the SAW correlator 16 not only outputs a normal peak correlation signal when the preamble is input (see A, B, and C in FIG. 9 (1)), but also produces signals that are affected by noise components in the SS signal wave. In some cases, peak noise of a certain level may be output (see FIG. 9 (1) Nori, E, and F).

The correlation signal amplified by the amplifier 18 is envelope-detected by the envelope detection circuit 20 (see FIG. 9 (2)), then inputted to the comparison circuit 22, and generated by the voltage setting potentiometer 24 as a threshold signal generation circuit. The threshold signal SC (Fig. 9 (
2)), and an initial synchronization pulse (initial synchronization signal) that reaches r)(J level is generated only while the envelope detection signal P exceeds the threshold signal Sc), and the PN code generator ( (not shown) ((3) in FIG. 9).

(See (4)).

When the PN code generator receives an initial synchronization pulse, it performs initial synchronization of the despreading PN code.

[Problem to be solved by the invention]

However, in the above-mentioned initial synchronization signal generator, S
If the C/N value of the SS signal wave input to the AW correlator 16 fluctuates, or if the constant output level set in the AGC amplifier 14 fluctuates due to temperature drift, etc., the output level of the SAW correlator 16 will also fluctuate. However, the level of the normal peak correlation signal and the peak noise will fluctuate as shown in FIG. 9 (1), but since the level of the threshold signal Sc created by the voltage setting potentiometer 24 is constant, the threshold signal If the level of Sc is too high, even if a normal peak correlation signal is output from the SAW correlator 16, the comparator circuit 22 may not be able to output a normal pulse during the initial period, or the pulse width may be insufficient (see FIG. 9). 2) 5c
= Sc, see (3)), conversely, if the level of the threshold signal Sc is too low, the comparator circuit 22 may output an incorrect initial synchronization pulse when peak noise is output from the SAW correlator 16, or the pulse The width may become too wide (see 5c=Scz+ (4) in Figure 9 (2)).

If an initial synchronization pulse whose pulse width is insufficient or too wide or an erroneous initial synchronization pulse is input to the PN code generator in this way, an initial synchronization error will occur.

This invention was made in view of the above-mentioned conventional problems.
It is an object of the present invention to provide an initial synchronization signal generating device for an SS receiver that can always perform accurate initial synchronization even if a C/N value or level fluctuation occurs in a correlator input.

[Means to solve the problem]

The initial synchronization signal generating device for the SS receiver of the present invention is based on the SS receiver.
an amplifier that amplifies a signal wave, a correlator provided on the output side of the amplifier, an input level detection circuit that detects an input level of the correlator, and a main envelope detection circuit that performs envelope detection of the output of the correlator; A sub-envelope detection circuit that performs envelope detection on the output of the correlator and has a time constant set larger than that of the main envelope detection circuit, and a threshold signal according to the output of the input level detection circuit and the output of the sub-envelope detection circuit. A comparison circuit that compares the output of the main envelope detection circuit with the threshold signal and outputs an initial synchronization signal while the output of the main envelope detection circuit exceeds the threshold signal. It is a feature.

〔Example〕

Next, one embodiment of the present invention will be described with reference to FIG.

1 is a block diagram of an initial synchronization signal generator for an SS receiver according to the present invention.

Note that the same components as in FIG. 7 are given the same reference numerals.

The SS signal wave down-converted to a predetermined intermediate frequency is input to the amplifier IO and amplified.

A BPF 12 is connected to the output side of the amplifier IO, and only necessary frequency bands are extracted.

The AGC amplifier 14 is connected to the output side of the BPFI2, and the AGC amplifier 14 is connected to the output side of the BPFI2.
The output level of amplifier 14 is made constant.

On the output side of the AGC amplifier 14, there is an S as an example of a correlator.
A W correlator 16 is connected to the SAW correlator 16, which inputs the preamble in the SS signal wave and outputs a correlation signal that reaches a peak when the spread PN code in the SS signal wave matches the PN pattern of the SAW correlator 16. .

The correlation signal is amplified by an amplifier connected to the output side of the SAW correlator 16 (see FIG. 2 (1)).

A main envelope detection circuit 20Δ having the same configuration as the envelope detection circuit 20 in FIG. 7 is connected to the output side of the amplifier 18.
The amplified correlation signal is subjected to envelope detection in the amplifier 18, and a main envelope detection signal P is output (see FIG. 2 (2)).

Here, the time constant due to C+ and R+ of the main envelope detection circuit 20A is set to be relatively small, and the detection efficiency is high.

A comparison circuit 22 is connected to the output side of the main envelope detection circuit 20A, and the threshold signal Sc created by the threshold signal creation circuit 30 and the main envelope detection signal P are compared to produce an upper envelope detection signal. “H” is applied only while P exceeds the threshold signal Sc.
An initial synchronization pulse (initial synchronization signal) having a level of 1 is generated and output to a PN code generator (not shown) of the DLL circuit (see FIG. 2 (6)).

An input level detection circuit 32 is connected to the output side of the AGC amplifier 14 in parallel with the SAW correlator 16.
The level of the signal input to the W correlator 16 is detected.

This input level detection circuit 32 is connected to the output side of the AGC amplifier 14 to amplify the SS signal wave output from the AGC amplifier 14, and the input level detection circuit 32 is connected to an amplifier 34 that amplifies the SS signal wave output from the AGC amplifier 14, and an envelope of the amplified SS signal wave output from the amplifier 34. It consists of an envelope detection circuit 36 which detects the signal and outputs it as an input level detection signal S4 (see FIG. 2 (3)).

Although the AGC amplifier 14 keeps the output level constant, the set output level fluctuates due to temperature drift and the like.

For this reason, the input level of the SAW correlator 16 also fluctuates,
The correlated signal level also varies.

The input level detection circuit 32 has a function of detecting the input level of the SAW correlator 16 which varies due to salinity drift and the like.

The input level detection signal S4 output from the input level detection circuit 32 is sent to the threshold signal generation circuit 30 connected to the output side.
Output to.

On the other hand, the main envelope detection circuit 2OA is connected to the output side of the amplifier 18.
A subchromatic line detection circuit 38 is connected in parallel with the subchromatic line detection circuit 38, and the amplified correlation signal outputted from the amplifier 18 is envelope-detected to produce a subchromatic line detection signal S.

is output.

Here, the time constants C, , R, of the sub-envelope detection circuit 38 are the same as the time constants C, , R, of the main envelope detection circuit 20A.

The time constant is set to be larger than the time constant of (See Figure 2 (4)).

The sub-envelope detection signal S output from the sub-envelope detection circuit 38 is output to the threshold signal generation circuit 30 connected to the output side.

The threshold signal generation circuit 30 generates a threshold signal S according to the input level detection signal S input from the input level detection circuit 32 and the sub-color noise detection signal S input from the sub-envelope detection circuit 38. It is output to the comparison circuit 22.

This IJ4fi signal control circuit is created using a predetermined constant voltage S.
b, a constant voltage Sb generated by the voltage setting potentiometer 40, and an input level detection signal S4.b. The output of the adder circuit 42 is outputted as the threshold signal Sc to the comparator circuit 22 (see FIG. 2 (5)).

Next, the operation of this embodiment will be explained with reference to FIGS. 2 to 6.

First, a case will be described based on FIG. 2 in which the output level of the AGC amplifier 14 is at the normal set level and does not fluctuate due to temperature drift or the like.

The SS signal wave down-converted to an intermediate frequency is amplified by an amplifier 10, and then a necessary band is extracted by a BPF 12.

The SS signal wave whose band is limited by the BPF 12 is outputted to the AGC amplifier 14 after its output level is made constant to a predetermined level.
It is output to the W correlator 16 and the input level detection circuit 32.

The input level detection circuit 32 amplifies the output of the AGC amplifier 14, performs envelope detection, and outputs an input level detection signal S4 indicating the input level of the SAW correlator 16 to the threshold signal generation circuit 30.

Here, since the output level of the AGC amplifier 14 is at the normal setting level, the input level detection signal S1 is also the normal value S. (Figure 2 (3) Reference 1!: j).

The SAW correlator 16 outputs a correlation signal that reaches a peak when the spread PN code in the input SS signal wave and the PN pattern of the SAW correlator 16 match. This is assumed to be a regular peak correlation signal.

Further, the SAW correlator 16 also outputs peak noise in addition to the normal peak correlation signal due to the influence of noise in the SS signal wave.

However, if the C/N value of the SS signal wave input to the SAW correlator 16 fluctuates (this C/N (I!! fluctuation is much steeper than the fluctuation in the output level of the AGC amplifier 14 due to temperature drift, etc.) ), the peak level of the normal peak correlation signal and peak noise output from the SAW correlator 16 changes accordingly (see AI, Bl, CI, DI, El, Fl in FIG. 2 (1)), Moreover, at this time, the level of the noise component in the correlation signal also changes according to the change in the C/N value.

The correlation signal output from the SAW correlator 16 is amplified by the amplifier 18 and then output to the main envelope detection circuit 20A and the sub-envelope detection circuit 38.

The main envelope detection circuit 20A detects the correlation signal with high detection efficiency and outputs the main envelope detection signal P to the comparison circuit 22 (see FIG. 2 (2)).

On the other hand, the subchromatic line detection circuit 38 performs envelope detection on the correlation signal with a large time constant, converts the noise component in the correlation signal into a DC component, and adds a normal peak correlation signal and peak noise to this DC component. A sub-color noise detection signal S on which the envelope is superimposed is formed and outputted to the threshold signal generation circuit 30 (
(See Figure 2 (4)).

While the base level of the main envelope detection signal P is constant at ground potential, in the sub-color envelope detection signal s1, the C/N value of the input signal of the SAW correlator 16 becomes small, resulting in noise components in the correlation signal. As the C/N value increases, the DC component converted from this noise component increases, and conversely, as the C/N value increases and the noise component decreases, the DC component decreases, so the base level changes as the C/N value changes. change (see Figure 2 (2)).

In the threshold signal generation circuit 3o to which the input level detection signal S,=S, and the sub-color line detection chair number S are input, the addition circuit 40 calculates Sb and Sa. , Sl are added to produce a threshold signal Sc
It is output to the comparison circuit 22 as (=3.+S, .+S,).

This threshold signal Sc is as shown in FIG. 2 (5), and Sb and S
,. Since this is constant, the signal changes according to 31.

Therefore, according to the fluctuation of the C/N value of the input signal of the SAW correlator 16, the normal peak envelope detection signal of the main envelope detection signal P (at in FIG. 2 (2)).

Even if the peak levels of the peak noise envelope detection signals (di, el, rl in Fig. 2 (2)) change relatively suddenly, the threshold signal Sc will follow this and change. ,
Since the level of the threshold signal S is always higher than the peak noise envelope detection signal, and the threshold signal Sc changes in height depending on the peak level of the normal peak noise envelope detection signal, the ratio soft circuit 22 The output is as shown in Figure 2 (6), and the output of the initial synchronization pulse caused by the peak 1 raw noise is eliminated, and an accurate initial synchronization pulse corresponding to the normal peak envelope detection signal is output. That will happen. The pulse width of the initial synchronization pulse is also approximately constant regardless of the peak level of the regular peak envelope detection signal.

Therefore, P
An N code generator (not shown) allows for accurate and reliable initial synchronization without malfunctions.

Next, a case in which variation in the output level of the AGC amplifier I4 due to temperature drift or the like is added to variation in the C/N value of the input signal of the SAWA relator 16 will be described.

Here, a case where the output level increases will be described based on FIGS. 3 and 4.

When the output level of the A G CPjJ amplifier 14 (that is, the input level of the SAWA relator 16) varies from a predetermined set level due to temperature drift, etc., the variation occurs relatively sharply.

This fluctuated input level of the SAW relay leak I6 is detected by the input level detection circuit 32 and output as an input level detection signal. Since it is gradual, it can be regarded as constant over a short period of time,
The input level detection signal S4 at this time is set as Sat (see FIG. 3 (3)).

Sl is increased by S from S4°.

On the other hand, since the level of the correlation signal increases in proportion to the increase in the input level of the SAWA relator 16, when the C/N bM of the input signal of the SAWA relator 16 changes as in the case of FIG. 2 (1), The correlation signal and the upper envelope detection signal P are as shown in FIGS. 3(1) and (2).

On the other hand, since the time constant of the sub-envelope detection circuit 38 is set relatively large, in addition to fluctuations in the C/N value of the input signal to the SAWA relator 16, if fluctuations in the input level of the SAWA relator 16 are added. , since the fluctuation in the correlation signal level becomes large, the sub-envelope detection circuit 38 cannot follow it completely, and the sub-envelope detection signal S as shown in FIG. 3 (4) is generated.
, =S, 1 is output.

Here, assuming that the input level detection signal S4 output from the input level detection circuit 32 remains at S4°, the rA value signal S output from the threshold signal generation circuit 30 is S, =S b +S a. 10S1 ・・・・・・(
1), but in this case, the correlation signal, upper envelope detection signal P
, input level detection signal Sa, sub color line detection signal Sa, r
The 11-value signal Sc and the initial synchronization pulse are shown in Fig. 4 (1) to (
6), the pulse width of the initial synchronization pulse becomes wide for the normal peak envelope detection signal in the main envelope detection signal P, which has a relatively high level, and the PN
There is a risk that an initial synchronization error will occur on the code generator side.

In the case of this embodiment, the input level detection signal S, has changed to S□, and the rA output from the threshold signal generation circuit 30
The value multiplied signal Sc, Sc = Sb + 31 (''-3ao + s) 10 Sat and t, (S) increases by S from equation (1) and follows the upper bound of the correlation signal level.

At this time, the correlation signal, the upper envelope detection signal P1, the input level detection signal S4. Subchromatic line detection signal S,.

The threshold (irj signal Sc, initial synchronization pulse is
As shown in (6), it goes without saying that an erroneous initial synchronization pulse due to peak noise is not output, but also that the normal peak 1 raw envelope detection signal in the royal envelope detection signal P is at a comparable level. The pulse width of the initial synchronization pulse issued for the high one is not widened and is kept almost the same as in the case of Figure 2.

Therefore, accurate and reliable initial synchronization can be applied to the PN code generator.

On the other hand, a case where the output level of the AGC amplifier 14 decreases from a predetermined set level due to temperature drift or the like will be explained with reference to FIGS. 5 and 6.

At this time, the input level detection signal S4 outputted from the input level detection circuit 32 becomes S42, which is lower than S4° by S' (see FIG. 5 (3)).

On the other hand, since the level of the correlation signal decreases in proportion to the decrease in the input level of the SAW correlator 16, when the C/N value of the input signal of the SAW correlator 16 changes as in the case of FIG. 2 (1), The correlation signal and main envelope detection signal P are as shown in FIGS. 5(1) and (2).

On the other hand, since the time constant of the sub-envelope detection circuit 38 is set relatively large, in addition to fluctuations in the C/N value of the input signal to the SAW correlator 16, if fluctuations in the input level of the SAW correlator 16 are added. , since the fluctuation in the correlation signal level becomes large, the sub-color line detection circuit 38 cannot follow it completely, and the sub-color line detection signal S as shown in FIG. 5 (4) is generated.
, =S1□ is output.

Here, assuming that the input level detection signal S output from the input level detection circuit 32 remains at S4°, the threshold signal Sc output from the threshold signal generation circuit 30 is 5c=Sb+So+S,ffi... ...(2), but at this time, the correlation signal, the upper envelope detection signal P, the input level detection signal Sa, the sub-color intersection detection signal S1. The threshold signal Sc and the initial synchronization pulse are as shown in Fig. 6 (1) to (6), and are related to a relatively low level one of the regular peak envelope detection signals of the width P of the main color line detection signal. In this case, the pulse width of the initial synchronization pulse becomes narrow, and there is a possibility that an initial synchronization error will occur on the PN code generator side.

In the case of this embodiment, the input level detection signal Sd has changed to S, and the threshold signal S5 output from the threshold signal generation circuit 30 is Sc,=Sb +Saz (=Sao S')
+Sag, and according to equation (1), it decreases by S and follows the decrease in the correlation signal level.

At this time, the correlation signal, the main color line detection signal P, the input level detection signal S1. Subcolor line detection signal S,.

Threshold signal S6. The initial synchronization pulse is shown in Figure 3 (1) to (6).
As a result, not only will an erroneous initial synchronization pulse due to peak noise not be output, but the main color line detection signal P
The pulse width of the initial synchronization pulse issued for the relatively low-level regular peaked envelope detection signal is not narrowed, but is maintained at approximately the same pulse width as in the case of FIG.

Therefore, it is possible to apply an accurate and reliable initial synchronization period to the PN code generator.

In this embodiment, the SAW correlator 16 is connected in parallel to the output side of the AGC amplifier 14.
An input level detection circuit 32 is provided which detects the input level of the amplifier 1 and outputs an input level detection signal S4.
A sub-color line detection circuit 38 is provided in parallel with the main envelope detection circuit 20A on the output side, and the time constant of the sub-color line detection circuit 38 is set to be larger than that of the main envelope detection circuit 20A to eliminate noise in the correlation signal. The component is converted into a DC component, a normal peak correlation signal and an envelope component of peak noise are superimposed on this DC component to form a sub-chromatic noise detection signal S1, and the input level is detected by the threshold signal generation circuit 30. By creating a threshold signal Sc by adding the signal S4 and the sub-color cross detection signal S to a constant voltage S and outputting it to the comparator circuit 22, the output level of the AGC amplifier 14 fluctuates due to temperature drift etc., resulting in SAW. When the input level of the correlator 16 fluctuates or the C/N value of the input signal of the W correlator 16 to S fluctuates, and the level of the correlation signal output from the SAW correlator 16 fluctuates, the correlation signal level changes. Since the threshold signal Sc is varied to follow the fluctuation, an incorrect initial synchronization pulse will not be output due to peak noise, and
In addition, it is possible to output an initial synchronization pulse with a substantially constant pulse width regardless of the peak level of the normal peak correlation signal, making it possible to perform accurate and reliable initial synchronization.

Furthermore, since the threshold signal Sc changes following fluctuations in the output level of the AGC amplifier 14, the temperature compensation of the AGC amplifier 14 does not have to be performed so strictly, which reduces the burden on the circuit configuration.

In the above embodiment, the threshold signal generation circuit adds the input level detection signal (S,) and the sub-color line detection signal (Sl) to the constant spiritual pressure (Sh) generated by the voltage setting potentiometer to generate the threshold signal ( Sc), but the present invention is not limited thereto, and the voltage setting potentiometer may be omitted and the threshold signal may be created simply by adding the input level detection signal and the sub-color line detection signal. Generally, the key point is 1, which corresponds to the input level detection signal and the sub-color line detection signal.
'A value multiplied signal may be created and output to the comparator circuit.

Furthermore, although the case where a SAWA relay relay is used as a correlator has been described, other correlators such as a SAWA revolver or a mated filter may be used, and the preceding stage of the correlator may also be an ordinary amplifier instead of an AGC amplifier. .

〔Effect of the invention〕

According to the initial synchronization signal generator for an SS receiver of the present invention, the input level of the correlator is detected by the input level detection circuit, and the output of the correlator is connected in parallel by the main envelope detection circuit and the sub-color line detection circuit. Perform envelope detection, set the time constant of the sub-color line detection circuit to be larger than the main envelope detection circuit, and create a threshold signal in accordance with the output of the input level detection circuit and the output of the sub-envelope detection circuit using the threshold signal generation circuit. The output of the main envelope detection circuit and 1. 'When compared with the A-value multiplied signal comparison circuit, the output of the initial synchronization signal while the output of the main envelope detection circuit exceeds the threshold signal causes the correlator input level to fluctuate and the correlator input signal to be When the level of the correlation signal output from the correlator changes due to fluctuations in the C/N value of the In addition, it is possible to output an accurate initial synchronization pulse with a nearly constant pulse width regardless of the peak level of the regular peak correlation signal, which is accurate and reliable. Initial synchronization can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an initial synchronization signal generator for an SS receiver according to one embodiment of the present invention, and FIGS. 2 to 6 are time charts explaining the operation of FIG. 1. Fig. 7 is a block diagram of an initial synchronization signal generator of a conventional SS receiver, Fig. 8 is a diagram showing the frequency spectrum of the SS signal wave, and Fig. 9 is a time chart explaining the operation of Fig. 7. . Explanation of main symbols 14: l6: 0A 22: 30: AGC amplifier, SAWA relayator, : main envelope detection circuit, ratio soft circuit, threshold signal generation circuit, 32: input level detection circuit, 38: secondary color line detection Circuit, :Voltage setting potentiometer, :Additional 11 circuit.

Claims (1)

[Claims] An amplifier that amplifies an SS signal wave, a correlator provided on the output side of the amplifier, an input level detection circuit that detects the input level of the correlator, and an envelope detection circuit for the output of the correlator. The main envelope detection circuit, the sub-envelope detection circuit that envelope-detects the output of the correlator and whose time constant is set larger than that of the main envelope detection circuit, and the output of the input level detection circuit and the sub-envelope detection circuit. A threshold signal creation circuit that creates a threshold signal according to the output of An initial synchronization signal generator for an SS receiver, including a comparison circuit for outputting the output.