JPH025344B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a multiple wave analysis device that measures the delay time, amplitude, and phase of each component of multiple waves generated by a complex multiple propagation path such as a land mobile propagation path. Conventionally, this type of equipment has an oscillator with a highly stable frequency such as rubidium or cesium, and a frequency synthesizer in both the transmitting signal and receiving section, and the transmitting section generates a correlation code, an IF signal, a transmitting station oscillation signal, etc. The receiving section was configured to independently generate correlation codes, IF signals, shift signals for the correlation codes, and receiving station oscillation signals to create signals necessary for correlation operations (DCCox, IEEE
Tr vol AP−20, No. 5, Sept., '72, DL
Nielson, IEEE Tr.vol VT−27, No. 3, Aug.
'78). These devices have independent oscillators for transmitting and receiving, so in order to measure the delay time between multiplexed waves, it is necessary to match the transmitter and receiver to match the synchronization of the correlated signals before starting the measurement. Moreover, this device had a drawback that the device was expensive because it had a highly stable oscillator and synthesizer in each of the transmitting section and the receiving section. The present invention aims to solve these drawbacks, and utilizes correlation technology to simplify the configuration of the transmitting section and receiving section, keeping them all in a synchronous relationship, and reducing the delay time of multiple waves. , which attempts to accurately and easily measure amplitude and phase.
This will be explained below with reference to the drawings. Figure 1 shows the transmitting section of this device, where 1 is a clock signal oscillator, 2 is a correlation code generator, 3 is an IF signal oscillator,
4 is a modulator, 5 is a transmitting local oscillator, 6 is a mixer, 7 is a bandpass filter, and 8 is a transmitting antenna. This operation is as follows. 2 is driven by the clock signal generated at 1 to generate a correlation code. This correlation code is a code with large autocorrelation characteristics, and for example, M-sequence codes and Gold codes are well known. This code is used for communication that detects correlation by taking advantage of its large autocorrelation characteristic, and is used for spread spectrum communication systems. The properties of this code are explained in the literature ("Spread Spectrum Communication System" by Dickson,
I am familiar with Zyatek Publishing). By that signal, 3
The IF signal generated at 4 is modulated and converted into an RF frequency by mixer 6 together with the transmitting station signal generated at 5. Next, a bandpass filter 7 removes unnecessary frequency components and shapes the spectrum, and the signal is radiated from an antenna 8. After all, the operation of this circuit can be seen as an SS transmitter that uses only spread modulation and no primary information signal. FIG. 2 shows a first embodiment of the present invention, in which 9 is an antenna connected to a receiving section for generating a correlation signal;
0 is an antenna for measuring multiple waves, and an antenna similar to 9 or a directional antenna is used for measuring the direction of arrival of multiple waves. 11 is a common reception local oscillator, 12 is a distributor, 13 and 14 are RF receivers,
15 is the IF signal 1, 16 is the first correlation receiver, 1
Reference numeral 7 indicates IF signals 2, 18, 19, and 20, which are respectively reproduced correlation codes, clock signals, and frame signals. 21 is the IF signal 3. 22 is the second
In the correlation receiver, 23 is a modulator, 24 is a correlation code phase control circuit, 25 is a phase-shifted correlation code, 26 is a sweep signal, 27 is an output IF signal of the receiver 14, and 28 is a correlation code phase control circuit. Output signal, 29
30 is a narrow band filter corresponding to an integrator, 31 is a correlation detection output signal, 32 is an amplitude and phase detection circuit, and 33 and 34 are detected amplitude and phase signals. 35 is an X-Y plotter or oscilloscope. The operation of this device is as follows. Signals received by antennas 9 and 10 are input to RF receivers 13 and 14, respectively. On the other hand 1
The common reception local oscillation signal generated at 1 is divided into two at 12 and supplied to receivers 13 and 14, respectively, and the IF signal 15 with frequency f _I1 is sent to the first correlation receiver 16, and the other one with the same frequency is sent to the first correlation receiver 16. IF signal 2
7 is input to the second correlation receiver 22. in this case
It goes without saying that the IF signals 15 and 27 have the same frequency. As described later in FIG. 3, the first correlation receiver 16 has a built-in AFC circuit, and has a frequency f _I1 .
While generating a signal phase-synchronized with the IF signal 15, the IF signal 17 of frequency f _I2 and the IF signal of frequency f _I3 are generated.
A signal 21 is generated. The operating frequency of the amplitude phase detection circuit 32 and the intermediate frequency (IF) used by the RF receiver 13 do not necessarily match. In order to ensure the flexibility of this device, it is better to consider both frequencies as different. For example, if the operating frequency of the amplitude phase detection circuit 32 is f _I3 and the IF frequency of the RF receiver is f _I1 , then the other signal 2 input to the mixer 29
The frequency of 8 must be f _I1 − f _I3 ,
Since this is equal to the frequency f _I2 of the IF signal output from the correlation receiver 16, it is necessary to establish the relationship f _I1 = f _I2 + f _I3 . The correlation code 18 regenerated by the first correlation receiver is regenerated by a phase control circuit 24 in the second correlation receiver 22 using a clock signal 19 and a frame signal 20, so that the correlation code 18 is regenerated at a fixed period for a fixed number of bits in one frame. At the same time, a sweep signal 26 synchronized with the shift period is generated. Next, the modulator 23 modulates the IF signal 17 with the phase-shifted correlation code 25 in the same manner as in the transmitting section of FIG. 1 to generate a signal 28 for correlation operation. Next, the mixer 29 mixes the received signal 27 and the correlation signal 28.
The mixer 29 and the narrowband filter constitute a so-called correlator. In other words, the mixer 29 is a multiplier for correlating the signals 27 and 28.
By passing this output through a bandpass filter with a band sufficiently narrower than the clock frequency, the signal 27
A signal having a level corresponding to the magnitude of the correlation between the signal 29 and the amplitude of the signal 27 is obtained. The frequency is f _I1 −
f _I2 . When the correlation between both signals is 1, the modulation of the signal 27 is loosened and it becomes an unmodulated wave. Next, this operation will be explained. Now, if the correlation code is S(t) and the carrier frequency is f _c , the transmitted signal is expressed as S ^c (t)=R _e [S(t) e ^j2 〓 ^fct ]. Now, the equivalent baseband impulse response that combines all the filters in the transmitter and receiver is b(t), and that of the multipath propagation path is g(t).
Then, the carrier band characteristics are b ^c (t) = 2R _e
[b(t)e ^j2 〓 ^fct ], g ^c (t)=2R _e [g(t)e ^j2 〓
^fct ] is well known. Here, there is no problem in replacing the carrier frequency f _c with the output frequency f _I1 of the receivers 13 and 15, so the transmitted signal S ^c (t) = R _e [S (t) e ^j2 〓 ^fI1t ]...(1) Filter characteristics b ^c (t)=2R _e [b(t)e ^j2 〓 ^fI1t ]...(2) Multipath propagation path characteristics g ^c (t)=2R _e [g(t)e ^j2 〓 ^fI1t 〕 ...(3) Also, since the correlation signal 28 is modulated with a code synchronized with the transmission clock signal regenerated by the first correlation receiver 16, it differs from the transmission signal only in its center frequency. The correlation signal 28 can be expressed as follows using the transmission code S(t) of the transmitter. S ^l (t)=R _e [S(t)e ^j2 〓 ^fI2t ]...(4) On the other hand, the received signal 27 input to the correlator 22 is
It is given as follows as a convolution of the transmission signal S ^c (t), the filter characteristic b ^c (t), and the multipath propagation path characteristic g ^c (t). z ^c (t)=S ^c *b ^c (t) * g ^c (t) Substituting the relationships (1), (2), and (3) into the above equation, z ^c (t)=R _e [z( t) e ^j2 〓 ^fI1t 〕 ...(5) However, z(t)=S(t)*b(t)*g(t)
...(6) is expressed as the equivalent baseband response. The correlator 22 outputs the received signal z ^c (t) and the correlation signal S ^l
Since the correlation calculation of (t) is performed, if the constant terms are collectively expressed as K, the output R _B (τ) 31 can be expressed as follows from (4) and (5). R _B (τ) = KR _e [∫ ^T ₀ S ^l (t-τ)・z ^c (t)dt] = KR _e [{∫ ^T ₀ S(t-τ)・z(t)dt} e ^j2 〓 ^(fI1-fI2)t 〕 Adding (6) into this, R _B (τ) = KR _e [{R _s (t), *b (t) * g (t)
} e ^j2 〓 ^(fI1-fI2)t 〕 ...(7) However, R _s (τ) is 1/T∫ ^T ₀ S(t-τ)・S(t
) dt is the autocorrelation function of the correlation code S(t). Therefore, the output signal 31R _B (τ) of the correlation detector in this device is an autocorrelation function of the correlation code S(t), and a time waveform having the same shape as R _s (t) is shaped by a filter b(t). It becomes a band signal whose complex envelope is the response of the multipath propagation path g(t) obtained at that time. Since the autocorrelation function R _s (τ) of S(t), which is generally used as a correlation code, uses a pulse-like one as described later, the formula (7)
To correctly detect g(t) from R _s (t)*b
It is necessary that (t) be a sufficiently narrow pulse. A signal received via a multiwave propagation path is a sum of components with different amplitudes and delay times, but since this propagation path is a linear system, the superposition theorem holds true. Therefore, the amplitude of the nth multiwave
a _o and the delay time τ _o , the multiwave propagation path g
Since the correlator output signal 31 as a response to (t) is expressed by the sum of the carrier wave pulses mentioned above, it is as follows. 〓 ⁿ a _o R _sb (t-τ _o ) e ^j2 〓 ^fI3(t- 〓 ⁿ⁾ ……(8) Here, R _sb (t) = R _s (t) * b (t), f _I3 = f _I1 −
Let f _I2 . Now, the delay time τ _o can be expressed as the sum of the absolute value delay time τ ₀ of one arbitrarily selected multiwave component and the relative delay time τ _oo from τ ₀ of the other multiwave component that we are currently focusing on, (8 ) is as follows: a ₀ e ^j2 〓 ^fI3(t- 〓 ₀ ⁾ {R _sb (t-τ ₀ )
＋ 〓 〓 ^{n 1} a _o /a ₀ R _sb (t−τ ₀ −τ _oo )e ^-j2 〓 ^fI2 〓 ⁿⁿ }……(
9) Here, −2πf _I3 τ _oo represents the relative phase of the nth component at the center frequency f _I3 . Therefore, the carrier pulse included in the correlator output 31 in the present invention includes information on the relative amplitude a _o /a ₀ and the relative phase difference -2πf _I3 τ _oo of the multiplexed wave components. This output 31 is then applied to an amplitude-phase detection circuit 32 together with a signal 21 of frequency f _I3 generated in the first correlation receiver. Here, the phase of the signal 21 is a sine wave that is synchronized with one component of the multipath. Therefore, since they are in a synchronous relationship with the correlator output 31 expressed by equation (9) except for the phase difference -2πf _I3 τ _oo , the detection circuit 32 detects all of the multipath components in equation (9). Relative amplitude a _o /a ₀ and phase -2πf _I3 τ _oo can be detected. Here, the amplitude-phase detection circuit can be easily realized using a commonly used multiplication type detector. Further detected detection signal 33 and phase signal 34
is an oscilloscope or X-Y plotter 3
At the same time, the sweep signal 26 is input to the Y axis of 5.
is input to the X axis, and it is possible to detect the relative delay time τ _oo at the peak point of the multipath, the relative amplitude a _o /a ₀ and the relative phase −2πf _I3 τ _oo at its magnitude. That is, the X axis (horizontal axis) indicates the delay time, and the Y axis (vertical axis) indicates the magnitude of the amplitude or phase of each component of the multiplexed wave. FIG. 3 is a configuration diagram of the AFC circuit. 36 is a mixer, 37 is a despread signal, 38 is a narrowband filter with a center frequency f _I3 , and 39 is a center frequency f _I3
40 is the phase comparator, 41 is the frequency f _I3
42 is a phase comparator output signal,
43 is a baseband loop filter, 44 is a voltage controlled oscillator with a center frequency f _I2 , 25 is a modulator, 4
6 is the correlation code regenerated in the first correlation receiver; 4
7 is a modulation signal having a center frequency f _I2 . The operation of this circuit is as follows. A signal 15 having a center frequency f _I1 received by the antenna 9 in FIG. 2 and frequency-converted by the receiver 13 is input to the mixer 36 from one side. Furthermore, the frequency f _I2 generated by the voltage controlled oscillator 44
A signal 17 of f _I2 +δf, which is close to f I2 +δf, is modulated by a regenerative correlation code 46 in a modulator 45 and becomes one input signal 47 of the mixer. Since the mixer output passes through the narrowband filter 38 as a despread signal 37 of two modulated waves, the center frequency of the output 39 becomes f _I1 - (f _I2 + δf) = f _I3 - δf, and the phase comparator 40 is input. Since the signal frequency from the stable oscillator 41 is f _I3 , the phase comparator output 42 containing various frequency components is passed through the narrow band filter 43.
When it passes through, it becomes a DC output corresponding to -δf, and that signal controls the VCO to normalize f _I2 +δf → f _I2 . Therefore, it is easy to set the frequency relationship of the signals 15, 21 and 17 to be f _I1 =f _I2 +f _I3 using well-known circuit technology. FIG. 4 shows the autocorrelation function R _s (τ) when an M-sequence code is used as the correlation code. 48 is the peak value L _p of the correlation function, 49 is the side lobe value L _s of the correlation,
50 is the period T ₁ of the base of the triangular waveform part of the correlation waveform,
51 is the repetition period T ₂ of the autocorrelation function.
For example, if the number of stages of the shift register that generates the M sequence is m, and the frequency of the clock signal is _fCL , then
When L _p = 1, each parameter in Figure 4 becomes L _s = -1/(2 ^m -1) T ₁ = 2/f _CL T ₂ = 1/f _CL (2 ^m -1) . Therefore, the limit for detecting multiple waves of the correlation detector output expressed by equation (7) is 10 log (L _s / L _p ) ² = −20 log (2 ^m −1) ... (10) and the delay between multiple waves The time difference resolution is T ₁ =1/f _CL . Therefore, to lower the detection limit of multiple waves, it is necessary to increase the number of stages of the shift register, and to increase the resolution of delay time, it is necessary to increase the clock frequency _fCL . The multiwave analyzer shown in Table 1 was constructed and tested in Tokyo, and the detection limit was -35 dB compared to the theoretical value of -42 dB, and the resolution of the delay time difference was 0.65 μS, making it suitable for use as a multipath analyzer. It was confirmed that it had good characteristics. In the configuration of the present invention shown in Fig. 2, two receiving antennas and two receivers are used, but depending on the measurement item, one each may be used.
Divide the IF output into two and send one side to the first correlation receiver 16,
It is also possible to adopt an arrangement in which the other one is supplied to the second correlation receiver 22.

[Table] FIG. 5 is another embodiment of the present invention, and 53 is the first embodiment.
is an unmodulated signal with frequency f _I1 generated by the correlation receiver. This corresponds to the case where f _I3 =0 in FIG. 54 is a second correlation receiver, 55 is a signal with a center frequency f _I1 modulated in the same format as the transmitter, 56 is a 90° hybrid, 57 is one branched signal, and 58 is the other signal whose phase has been rotated by 90°. component, 59 is an IF signal splitter that converts the received IF signal to 60
and 61 to 2 minutes. 62 is a mixer, and 63 is a narrow band filter. Similarly, 65 and 66 are a mixer and a filter, respectively. 64 and 67 are correlation detected signals, 68 is 64 and 67
69 is a circuit that calculates tan ^-1 of the ratio of 64 and 67. The operation of this circuit is as follows. The IF signal generated by the first correlation receiver is modulated by the modulator 23 in the same way as the transmitter, and is divided into two components that are 90° hybrid and orthogonal to each other.
2 and 65. Also RF receiver output 27
is divided into two at 59 and input to mixers 62 and 65. Since 62 and 63 and 65 and 66 form a correlator like mixer 29 and narrowband filter 30 in FIG. 2, outputs 64 and 67 are outputs obtained by correlation detection in mutually orthogonal directions of the received signals. Moreover, input signals 57 and 60 of mixers 62 and 65
Since 58 and 61 have the same frequency, the output 6
4 is output in the baseband band. Now, the output signals 64 and 67 are respectively Q=R _e {ae ^j },
If expressed as I=R _e {ae ^{j( +} 〓 ^/2) }, the output 33 of 68
is √ ² + ² = |a|, and the output of 67 is tan ⁻¹ Q/I=, which represents the amplitude and phase of the received signal, respectively.
In this way, the amplitude and phase of multiplexed waves can be detected using the configuration shown in FIG. Also, as in FIG. 2, the delay time can be detected from the amplitude peak point. FIG. 6 shows another embodiment of the present invention, in which 70 is a second correlation receiver, 71 is a synthesizer, and 72 is a second correlation receiver.
is a clock signal, 73 is a correlation code synchronization circuit, 7
4 is an IF signal with frequency f _I2 . The operation of this circuit is as follows. Using the output signal 15 from the RF receiver, the first
The operation of generating the PN signal 18, the clock signal 19, the frame signal 20, and the IF signal 21 having the frequency f _I3 by the correlation receiver 16 is the same as that shown in FIG. Synthesizer 7 in second correlation receiver 70
1 needs to generate a signal with a relatively stable frequency, but it does not need to be an ultra-highly stable oscillator such as a rubidium or cesium oscillator, and it is necessary to generate a signal with a relatively stable frequency. Any oscillator that maintains stability over time is sufficient. In the synchronization circuit of 73 correlation codes,
Generate the same PN signal as the transmitter, establish synchronization between the signal and the PN signal supplied from the first correlation receiver, and generate a PN having the same time reference as the transmitter.
Generate a signal. At the same time, the clock signal 19
Using the frame signal 20, a PN signal 25 is generated which repeats shifts by a constant period and a constant time width, similar to 24 in FIG. Note that the synchronization circuit of the correlation code 73 receives the signal from the first correlation receiver 16.
Once synchronized with the PN signal 18, the operation for establishing synchronization (hunting) is stopped, and the 18
It is assumed that the circuit continues to generate a PN signal independently of the PN signal. The modulator 23 modulates the IF signal 74 with the correlation code 25 in the same format as the transmitter,
The received IF signal 20 is generated by a correlator formed by a mixer 29 and a filter 30.
Correlation detection is performed. Similar to FIG. 2, the correlation detection output signal 31 has the same frequency f _I3 as the non-modulated IF 21, so that the amplitude and phase are detected.
Multiple wave characteristics can be detected. Note that here, the clock signal of 72 is slightly different from 19,
Also, the center frequency of 31 is 2 due to the IF signal of 74.
Although it is possible that the synthesizer is slightly different from 1, even if the synthesizer is not very stable, it will not significantly disturb the measurement results of the multiwave characteristics within the measurement time. The first correlation receiver supplements a relatively strong component among a large number of multiplex components and generates PN, clock and frame signals, as well as an IF signal synchronized therewith. Since the relative strength between multiple waves may fluctuate, in the configuration shown in Figure 2, the time reference may become uncertain due to the code for correlation being interrupted, but in the configuration shown in Figure 6, the time reference is not synchronized at one end. After this is established, the received signal is separated, allowing measurements to be taken while moving.
Note that it is also possible to configure the IF signal 74 and the modulator 23 in FIG. 6 and below like the correlation detector in FIG. 5 to extract a baseband detection signal. In each of the above embodiments, the correlation signal is transmitted from the transmitting side to the receiving side. By operating the correlation encoder in synchronization with frames 19 and 20, the same correlation signal as that on the transmitting side may be generated on the receiving side. As explained above, in the present invention, by applying the property that the SS receiver synchronizes to one component of multipath, it is possible to easily and accurately measure the amplitude, phase, and delay time of all components of multipath. eliminates the need for expensive oscillators and frequency synthesizers,
It has the advantage that the measurement procedure is simple.

[Brief explanation of drawings]

Figure 1 shows the transmitter of this measuring device, and Figure 2 shows part of the present invention.
An embodiment corresponding to the first invention, FIG. 3 is an example of an AFC circuit constituting an SS receiver, FIG. 4 is a diagram explaining an autocorrelation function of an M-sequence code, and FIG. 5 is another embodiment of the first invention. Embodiment FIG. 6 is an embodiment corresponding to the second invention. 1... Clock signal oscillator, 2... Correlation code generator, 3... IF signal oscillator, 4... Modulator, 5
...Transmission local oscillator, 6...Mixer, 7...Band filter, 8...Transmission antenna, 9...Reception antenna 1, 10...Reception antenna, 11...Reception local oscillator, 12...Signal distributor, 13...RF
Receiver, 14...RF receiver, 15...IF signal 1,
16...SS receiver, 17...IF signal 2, 18...
...Reproduction correlation code, 19...Clock signal, 20...
...Frame signal, 21...IF signal 3, 22...
Second correlation receiver, 23... Modulator, 24... Phase control circuit, 25... Correlation code subjected to phase shift, 26... Sweep signal, 27... IF signal,
28...Modulator output signal, 29...Mixer, 3
0... Narrowband filter, 31... Correlation detection output signal, 32... Amplitude and phase detection circuit, 33...
Amplitude signal, 34... Phase signal, 35... Oscilloscope or X-Y plotter, 36... Mixer, 37... Despread signal, 38... Narrow band filter, 39... Filter output signal, 40... Phase comparison 41... Oscillator, 42... Phase comparator output signal, 43... Baseband filter, 44...
Voltage controlled oscillator, 45...Modulator, 46...Regenerated correlation code, 47...Modulation signal, 48...Peak value of autocorrelation function, 49...Side lobe of autocorrelation, 50...Autocorrelation function output triangular wave Base period of 51... Repetition period of autocorrelation function, 53...
...Regenerated unmodulated IF signal, 54... Second correlation receiver, 55... Modulated IF signal, 56... 90° hybrid, 57... IF signal, 58... 90° IF signal, 5
9...IF distributor, 60...IF signal, 61...IF
Signal, 62...Mixer, 63...Baseband filter, 64...Detection output signal, 65...Mixer, 66...Baseband filter, 67...
Detection output, 68...Square root calculation circuit for sum of squares, 6
9... Ratio tan ^-1 calculation circuit, 70... Second correlation receiver, 71... Frequency synthesizer, 72...
Clock signal, 73...Correlation code synchronization circuit, 74
...IF signal.

Claims (1)

[Claims] 1. Means for receiving a radio signal modulated by a correlation code with a first antenna, outputting the correlation code and a clock synchronized therewith, and regenerating and outputting a first intermediate frequency signal. a first correlation signal receiving means including a first correlation signal receiving means, and a receiving means for receiving the radio signal with a second antenna and outputting a second intermediate frequency signal;
a phase control means for shifting the correlation code in 1-bit units based on the clock; a changing means for modulating the first intermediate frequency signal using the shifted correlation code in the same manner as the transmitter; second correlation signal receiving means comprising means for correlating the signal with the second intermediate frequency signal and outputting the amplitude and phase of the radio signal received by the second antenna; and 1. A multiwave analysis device comprising means for displaying the magnitude of the amplitude or phase of the radio signal on a time axis using a sweep signal. 2. A first correlation signal receiving means including means for receiving a radio signal modulated by a correlation code with a first antenna and outputting a correlation code and a clock synchronized therewith; receiving means for receiving and outputting a first intermediate frequency signal;
Correlation code synchronization means that generates a second correlation code that is the same as that of the transmitter and synchronizes with the correlation code; and a correlation code synchronization means that generates a second intermediate frequency signal and uses the second correlation code in the same manner as the transmitter. a second correlated signal receiving means comprising a modulating means for modulating the modulated signal and a means for correlating the modulated signal with the first intermediate frequency signal and outputting the amplitude and phase of the radio signal received by the second antenna; and means for displaying the magnitude of the amplitude or phase of the radio signal on a time axis using the sweep signal output from the correlation code synchronization means.