JPH02241147A - Spread spectrum receiver - Google Patents

Abstract

PURPOSE:To acquire correlation waveform from a prescribed time in a prescribed time and to observe the waveform with magnification by varying a relative phase of a PM signal modulating a received wave to be reassured and a correlation PN signal. CONSTITUTION:The synchronization of 1st and 2nd pulses is detected to start the production of 1st and 2nd PN and correlation PN signals simultaneously with the provision of a reset means 68. Since a series of PN codes are generated again from a same code when codes of the PN signals from 1st and 2nd PN code generators 51, 52 generating the PN signal from the same code are deviated by prescribed its, the phase of a 1st clock pulse is shifted by shift means 53 to move the observation range till the correlation output is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Application Field of the Present Invention The present invention relates to a spread spectrum receiving device that receives a signal spread modulated with a PN signal (pseudo noise signal).

<Prior art> (Figures 6 and 7) For example, when using radio waves to measure the distance difference in the propagation path, it is sufficient to detect the difference between the arrival times of the radio waves and multiply the time difference by the speed of light. .

However, normal transmitting and receiving systems can only measure large distance differences and are easily affected by noise.

For this purpose, a spread spectrum transmission and reception system has been used that can measure even small distance differences without being influenced by other communications or noise.

FIG. 6 is a schematic diagram showing the configuration of a spread spectrum transmitter 1 and a receiver 10 used for this purpose.

The transmitting device 1 spread-modulates a carrier signal of a predetermined frequency f'' with a PN signal output from a PN generator 2 in synchronization with a clock signal of a predetermined frequency f2, and modulates a spread modulation signal output from a modulator 3. It radiates into space from Anj-Su4.

The receiving device 10 frequency-converts the signal received by the antenna 11 using a local oscillation signal of a predetermined frequency f3, and converts the received signal by the frequency converter 12.
The converted signal is split by a phase shifter 13 into two signals IQ having a phase difference of 90 degrees, and each signal is input to two correlation detectors 14 and 15.

On the other hand, a modulated signal obtained by spread-modulating a signal of frequency (fl-f3) with a PN signal outputted from the PN generator 16 in synchronization with a clock signal of frequency (f2-Δf) is sent to the modulator 17.
The signal is input to two correlation detectors 14 and 15.

Note that the code sequences of the PN signal on the transmitting side and the PN signal on the receiving side are the same, and for example, both are 511 bits (. is taken as one frame.

The two correlation detectors 14 and 15 are composed of mixer-type correlation multipliers 14a and 15a and integrators 14b and 15b, and their outputs show power components different by 90 degrees.
8, a signal (root mean square) corresponding to the power intensity is synthesized and output.

This intensity signal is input to an oscilloscope 19.

FIG. 7 is a timing diagram showing the situation when this receiving device @10 receives radio waves from the transmitting device @1 (a,
The horizontal scales b, , c indicate the division of one frame of the PN signal).

PN of the direct wave from transmitter 1 at the start of reception (10 o'clock)
The signal is transmitted to the PN of the receiving device 10 as shown in Figure ff17a.
Assuming that the signal (C in the figure) is advanced by a time Ts, the phases of the two (that is, the time TS) are so different that a correlation cannot be obtained, so a correlation output (d in the figure) cannot be obtained. When the phase difference between the two becomes small after a predetermined period of time has elapsed, the correlation output A for the direct wave becomes thicker over time, and when synchronization occurs (t
The correlation output decreases after 1).

On the other hand, the PN signal of the reflected wave reflected by the reflector R such as a building and received (see figure b) has a phase difference corresponding to the distance difference of its propagation path. Correlation output B
increases later than the correlation output A of the direct wave, and decreases after synchronization (t2).

Note that the maximum values Am and Bm of the correlation outputs are proportional to the power intensities of the direct wave and the reflected wave, and the distance difference of the propagation path can be obtained from the time difference T.

That is, the delay time per 1 bit of the PN signal of the transmitting device 1 is 1/f2, and the time for which the frequency f2 and the frequency f2 - Δf deviate by 1 bit is 1/Δf, so T in 1 second
/<1/8f) - ding. The difference in distance is L= (1/f2> ・T・Δf −C(
m) (where C is the speed of light).

<Problems to be Solved by the Invention> However, since the PN signal on the receiving side is asynchronous with the PN signal on the transmitting side, the position where the correlation output is obtained is determined by the phase difference between the frames of both PN signals at the start of reception ( T in time
s), and in order to display the correlated output on the oscilloscope screen in one sweep, the receiving device 1
The time Tm until the phases of both PN signals are synchronized due to the frequency difference Δf between the 0 P and N signals and the direct wave PN signal (this maximum time is when Ts = 0, 1
Assuming M bits per frame, approximately M/Δf) is required.

Therefore, in order to observe the correlation waveform, the time axis of the oscilloscope must be at least as long as the time Tm.

This has the disadvantage that the observation may be made only at the end of the time Tm, and in this case, the previous observation time is wasted.

In addition, if the time axis of the oscilloscope becomes human as described above, it is possible to separate direct waves and foul waves that are close together, for example direct waves and foul waves that have a phase difference (time difference) of 1 bit, on the screen. The disadvantage was that it was impossible to judge.

For this reason, a method is used to enlarge the time axis of the oscilloscope and observe the part where the correlation output is displayed, but with this method, it is unclear where on the PN code the correlation is being taken, which hinders observation. was there.

It is an object of the present invention to solve this problem and provide a spread spectrum receiving device that can capture a correlation waveform within a predetermined time, such as observation start time J:, and further enlarge it for observation. .

Means for Solving the Problems> In order to solve the above problems, a first spread spectrum receiving device of the present invention transmits a received wave modulated with a PN signal consisting of a code sequence at a predetermined frequency to the In a spread spectrum receiving device that performs correlation detection using a spread modulation signal modulated with a correlated PN signal consisting of the code sequence at a predetermined frequency with a frequency difference, the spread spectrum receiver generates the correlated PN signal and modulates the received wave. The apparatus further includes a correlated PN signal generating section that outputs a variable relative phase of the correlated PN signal with respect to the PN signal, so that the time position at which the received wave and the spread modulation signal are correlated can be varied.

In addition, the second spectrum l-spread type receiving device has a P
The received wave modulated by the N signal is transmitted to a predetermined second frequency (f2-Δf) with a frequency difference (8f) from the first frequency.
In a spread spectrum receiving device that performs correlation detection using a spread modulation signal modulated with a correlated PN signal consisting of the M-bit code sequence, the first clock pulse having the first frequency (f2) and the second frequency (f2-Δf); a shift means for variably shifting the phase of the first clock pulse and outputting the first clock pulse; A PN consisting of the M-bit code sequence from the first clock pulse.
a first code generator that outputs a signal; a second code generator that outputs the correlated PN signal from the second clock pulse; and a code of the PN signal from the first PN code generator is predetermined. a first code detection means that outputs a first detection pulse every time the code matches; M bit)
a second code detecting means that outputs a second detection pulse every time they match a different code; and a second code detection means that detects that the first and second detection pulses are synchronized and outputs the first and second PN signals. and reset means for simultaneously starting the generation of the correlated PN signal, and by shifting the phase of the first clock pulse by the shifting means, the correlation output subjected to correlation detection is shifted from the start to the above. The phase difference between the PN signal and the correlated PN signal is obtained within the time it takes for the phase difference to reach N-pitch 1.

Therefore, the codes of the PN signals from the first and second PN code generators that generate the PN signal from the same predetermined code are shifted by a predetermined bit (N bits) (this period is the observation range). In order to generate a series of PN codes from the same predetermined code again, the observation range can be moved to a point where a correlation output can be obtained by shifting the phase of the first pulse using the shift means.

Embodiments of the present invention> (Figures 1 and 2) Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the main parts of an embodiment, and FIG. 2 is a block diagram showing the main parts of an embodiment, and FIG.
FIG. 2 is a block diagram showing an embodiment of a receiving device that monitors the reception level and reflection status of the received signal.

In FIG. 2, a frequency converter 22 mixes the received signal received by the antenna 21 with a local signal (frequency f3) from the signal generator 23 and performs heterodyne conversion into a predetermined frequency band (for example, 140 MHz band).

The signal generator 23 is a PLL type generator using a rubidium oscillator as a signal reference source, and generates a highly accurate and highly stable signal.

24 is the frequency, and the phase of the output signal from the converter 22 is 90
This is a phase shifter that branches into two signals 1Q with different degrees.

One of the branched received waves is input to the correlation multiplier 26 of the first correlation detector 25 .

This correlation multiplier 26 is, for example, a double balanced multiplier 1
It has already been configured and performs correlation detection between the spread modulation signal inputted from the modulator 27 via the amplifier 28 and the received wave.

The modulator 27 converts a signal of a predetermined frequency II (for example, 1293 MHz>) outputted from the signal generator 23 via the distributor 47 into a correlated PN signal from a correlated PN signal generator 50, which will be described later.
The signal is spread modulated.

29 is a band pass filter (hereinafter referred to as BPF) that passes a signal component in a predetermined intermediate frequency band (for example, 10.7 MHz) among the output from the correlation multiplier.

Note that the frequency f4 of the signal output from the distributor 47 is
It is set equal to the difference between the frequency obtained by subtracting the local oscillator signal frequency "3" from the frequency f1 of the transmission carrier wave and the center frequency of B1) F29.

30 is a logarithmic compressor that logarithmically compresses the level of the passed output of the BPF 29 and outputs the same.

31 is Miki' J-32 and low pass 'noirta' (hereinafter referred to as L
PF) 33, which converts the output from the logarithmic compressor 30 to a predetermined frequency f5 (for example, 10.7 M
The local oscillator signal (1-1z) is frequency converted, the converted output is band-limited, and a correlated waveform is output.

Therefore, the output of the LPF 33 indicates a signal corresponding to the logarithmically compressed power intensity of one vector component of the received wave.

Further, the received wave on the other side is input to the correlation multiplier 36 of the second correlation detector 35.

The second correlation detector 35 has exactly the same configuration as the first correlation detector 25, and is an intermediate product of the received wave and the spread modulation signal input from the modulator 37 via the amplifier 38. The frequency band signal passes through the BP 39, is logarithmically compressed by the logarithmic compressor 40, and is sent to the mixer 42 of the demodulator 41 and the LP
It is demodulated by F43.

45 is a calculator that calculates the root mean square of the detection outputs from the first and second correlation detectors 25.35, and this calculation output is displayed on the Y axis of the oscilloscope 46 as a signal corresponding to the power intensity of the received wave. has been entered.

The correlation P N @M generating section 50 has first and second PN signal code generators 51 and 52 as shown in FIG.
The first clock pulse of frequency f2 is input from the signal generator 23 to the PN code generator 51 of , via the shift circuit 53, and the second clock pulse of frequency f2-8f is input to the second PN code generator 52. A second clock pulse is being input.

The first and second PN code generators 51 and 52 are configured to sequentially output a series of PN codes of the same code series in parallel in synchronization with clock pulses, and when receiving a reset pulse, they output the same series of PN codes in parallel. A series of PN codes are generated from the initial code C<O>.

As shown in FIG. 3, the shift circuit 53 includes a pulse removal circuit 5 that performs pulse removal on the first clock pulse.
4, and a pulse insertion circuit 57 that performs pulse insertion.

The pulse removal circuit 54 inputs the first clock pulse to one input terminal of the AND circuit 55, and when the switch S1 is pressed, the pulse removal circuit 54 outputs "I-1" in synchronization with the first clock pulse.
The pulse is removed by inputting the gate signal from the gate signal output circuit 56, which changes from the "level" to the "L" level, to the other input terminal of the AND circuit 55.

The pulse insertion circuit 57 differentially shapes the output of the AND circuit 55 using a differential shaping circuit 58 and inputs the differentially shaped output to one input terminal of an OR circuit 59 , and inverts the output of the AND circuit 55 using an inverter 60 and inputs the output to the differential shaping circuit 61 . differentially shaped and input to the insertion pulse output circuit 62.

The insertion pulse output circuit 62 outputs one pulse from the differential shaping circuit 61 when the switch S2 is pressed.
9 to perform pulse insertion.

In FIG. 1, 63 indicates that the PN code (parallel output) generated by the first PN code generator 51 has a predetermined initial code C (0
), the first code detector 64 outputs a first coincidence pulse every time the PN code (parallel output) generated by the second PN code generator 52 changes from the initial code C(0) to N This is a second code detector that outputs a second matching pulse every time the second bit overlaps with the PNN code (N).

65 is a reset circuit, which includes an AND circuit 66 that takes the logical product of the first and second coincidence pulses, and an output circuit that overlaps the OR circuit 67 when the output of the AND circuit 66 rises to the H" level. The reset pulse generating circuit 68 sets the output to the "H" level and outputs the output to the "L" level upon receiving the next first coincidence signal, and the first PN code generator 51 and the OR circuit when the power is turned on. Outputs a reset pulse to circuit 67 and J-
It consists of a power-on reset circuit 69.

Note that the serial PN (8
The signal is output to the modulator 27.37 as a correlated PN signal.

Operation of the above-mentioned embodiment> For the spectrum 1 to RAM spread type receiver configured as described above, the carrier wave of frequency f1 is transferred to the carrier wave of frequency f1 as described above.
When a radio wave spread-modulated with a PN signal generated in synchronization with the clock signal of 2 is transmitted, the strong direct wave is received by the antenna 21 and converted by the frequency converter 22 into a local oscillation signal of a predetermined frequency f3. For example, the frequency is converted to a 140 MHz band.

The received waves split into phases 90 degrees different by the phase shifter 24 are input to first and second correlation detectors 25 and 35, respectively.

Here, suppose that the received wave is PN modulated at the timing of the frame shown in FIG.
), the first and second PN code generators 51 star 1-.
．． As shown in Figure 4c and d, the phase of the 52 PN code gradually shifts by the frequency Δf, and at time t1, the frame phase of the PN signal of the direct wave (Figure 4a) and the second PN code are shifted.
Since the phases of the correlated PN signals from the code generator 52 begin to be substantially synchronized, a correlated signal with an intermediate frequency (10.7 MHz>) is output from the BPF 29.39.

The levels of the correlation signals are compressed by logarithmic compressors 30 and 40, and demodulated to DC levels by demodulators 31 and 41, respectively.

The root mean square of the demodulated detection levels in two directions, that is, a signal corresponding to the power intensity of the direct wave is calculated by the arithmetic unit 45, and the oscilloscope 46 is sent to the oscilloscope 46 as shown in 1 in FIG. Therefore, a correlation waveform A of the direct wave that decreases until time t3 is obtained.

On the other hand, it is reflected from buildings etc. and is greatly attenuated (e.g. 60dB)
l,, Weak anti-wave input with a slight delay from the direct wave @
The first wave is also received in the same way as above, but the reflected wave PN signal (b), which is slightly delayed from the direct wave PN signal, and the second PN signal are received.
When the phase with the signal is synchronized from time t4 to time t6, and at time t5 when it is almost completely synchronized, the peak of correlation waveform B of the reflected wave becomes a relatively large peak 1 second later than the correlation waveform A of the direct wave. It will be displayed on the screen.

Therefore, based on the size of these mountains and the time interval between the mountains, the presence or absence of a reflective object on the radio wave propagation path, its attenuation amount, and the distance of the path iii! [Differences (using the above operations) etc. can be observed.

Note that if the PN code of the first PN code generator 51 serving as a reference and the PN code of the second PN code generator 52 are shifted by N bits at time t7, the first and second PN codes of the correlated PN signal generator 50 Since the first and second coincidence pulses from the second code detector 63 and 64 are output simultaneously as shown in FIG. 4 01f,
The OR circuit 67 outputs the reset l~ signal shown in FIG. 9 to the second PN code generator 52, and when the next first coincidence pulse is input, the state returns to the state at 10 o'clock.

Therefore, if the shift circuit 53 is not activated, the correlation waveform shown in the fourth diagram will be obtained on the screen of the oscilloscope 46.

In this case, the time axis of the oscilloscope 46 is repeatedly swept from 10 o'clock to t8 o'clock, and the PN code from the second PN code generator 52 is applied to the reference first PN code at - times of sweep time. N for the PN code from the code generator 51
This means that the correlation is taken in the range of 1-minutes, and the observation range (correlation range) is the range to 1-minutes.

In Fig. 4, the power was turned on at a good timing, and the PN signal of the received wave and the correlated PN signal were within the N-bit observation range from the beginning.
The first and second PN signals are determined from the received wave PN signals (a and b in the same figure).
If the P and N codes of the code generators 51 and 52 die with a slight delay, no correlation can be established within the observation range of N bits until the two PN codes shift by N bits at time t7.

Here, at any time t9 after both PN codes are reset at time t8, if the switch S2 of circuit 53 is pressed a predetermined number of times to insert a predetermined number of pulses between the first clock pulses, the basic The first PN code generator 5 becomes
The frame phase of the PN code from 1 advances by a predetermined time period f.

The first PN whose phase is shifted by Tf due to pulse insertion
Since the code generator 51 receives the first clock pulse in this advanced state thereafter, the code generator 51 receives the PN signal (fifth clock pulse) of the received wave.
For example, a PN code whose phase is slightly advanced with respect to FIGS. a and b) is output.

Therefore, the correlated waveforms A and B of the received waves are obtained on the screen from the time of the next reset 1 (time t10) as shown in the fifth diagram.

Note that if pulse insertion or pulse removal is performed at any time with respect to the first clock pulse, the frame phase of the PN code of the first PN code generator 51 serving as a reference will be changed by the number of pulses inserted or removed. The correlation waveform is also shifted left and right on the screen.

<Other embodiments of the present invention> Note that the present invention is not limited to this embodiment, and can be similarly applied to a receiving device that demodulates a spread-modulated received wave using only one correlation detector. .

In addition, in the above embodiment, the correlation output is converted to an intermediate frequency, the level of which is logarithmically compressed, and then detected into DC, but the present invention also applies to the receiving device with the conventional configuration (FIG. 6). can be applied.

Effects of the Present Invention> Spec 1 of the present invention - As explained above, the Lamb spread type receiving device has a PNN signal correlation that modulates the received wave to be measured.1) The relative phase with the N signal can be varied. Because of this structure, the observation range of any bit can be moved, and it is easy to see where on the PN code the observation range is set, making it easy to perform accurate measurements.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the main parts of an embodiment of the present invention, FIG. 2 is a block diagram showing the overall configuration of the embodiment, and FIG. 3 is a block diagram showing the main parts of FIG. 1. . FIGS. 4 and 5 are timing diagrams for explaining the operation of one embodiment. FIG. 6 is a block diagram showing a transmitting/receiving system including the conventional device, and FIG. 7 is a timing diagram for explaining the operation of the conventional device. 23... Signal generator, 50... Correlation P
N signal generator, 51...first PN code generator, 52...second PN code generator, 53...
... shift circuit, 54 ... pulse removal circuit,
57... Pulse insertion circuit, 63... First code detector, 64... Second code detector,
65...Reset circuit.

Claims (2)

[Claims] (1) A received wave modulated with a PN signal consisting of a code sequence at a predetermined frequency is modulated by a spread modulation signal which is modulated with a correlated PN signal consisting of the code sequence at a predetermined frequency with a frequency difference from the above frequency. In a spread spectrum receiving device that performs correlation detection, the correlation P with respect to the PN signal that generates the correlation PN signal and modulates the received wave.
What is claimed is: 1. A spread spectrum receiving device comprising: a correlated PN signal generating section that outputs a variable relative phase of an N signal; and a time position at which the received wave and the spread modulation signal are correlated is variable. (2) A received wave modulated with a PN signal consisting of an M-bit code sequence at a predetermined first frequency (f2) is transmitted to a predetermined second frequency (f) having a frequency difference (Δf) from the first frequency.
f2−Δf) is the correlation P consisting of the M-bit code sequence.
In a spread spectrum receiver that performs correlation detection using a spread modulation signal modulated with an N signal, a first clock pulse having the first frequency (f2) and a second clock pulse having the second frequency (f2-Δf) are provided. a signal generator that outputs a clock pulse of M; a shift means that variably shifts the phase of the first clock pulse and outputs the first clock pulse; PN consisting of a code sequence of bits
a first PN code generator that outputs a signal; a second PN code generator that outputs the correlated PN signal from the second clock pulse; and a code of the PN signal from the first PN code generator. a first code detection means that outputs a first detection pulse every time the code matches a predetermined code; (M bits) a second code detection means that outputs a second detection pulse every time they match a different code; and detecting that the first and second detection pulses are synchronized, and reset means for simultaneously starting the generation of the PN signal and the correlation PN signal, and by shifting the phase of the first clock pulse by the shift means, the correlation output of the correlation detection is changed from the start to the PN signal. A spread spectrum receiving device characterized in that the phase difference between the signal and the correlated PN signal can be obtained within the time required to reach N bits.