JPH0738467A - Transmitter-receiver - Google Patents

Abstract

PURPOSE:To make a transmitter-receiver excellent in noise resistant characteristic anti-interference characteristic and privacy corresponding to a narrow spread band width caused by 2-wave transmission of the reference signal transmission system and also easy in data reproduction. CONSTITUTION:As to output signals of 1st and 2nd local oscillators 1, 2 whose frequency difference is d.k+d/2, where d is a data band width and k is a positive integer, the former are modulated by a 1st multiplier 4 and the frequency is spread by a spread code generator 3 and a 2nd multiplier 5, the latter is frequency-spread by a spread code generator 3 and a 2nd multiplier 5 and they are synthesized by an adder 7 to generate a transmission signal. The transmission signal passes through a 1st band pass filter 8 at the receiver side and squared by a square computing element 9 and its output is given to a 2nd band pass filter 10, in which a frequency difference (F2-F1) of two waves is extracted and data are reproduced to attain bands of two waves in existence in duplicate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum transmitter / receiver using a direct spread method which is strong against noise and interference signals in a wireless communication system for wirelessly transmitting voice data and image data.

[0002]

2. Description of the Related Art In recent years, spread spectrum transmitters and receivers using the direct spread method have been widely used because they are excellent in noise resistance, interference resistance, and confidentiality in a wireless communication system for transmitting voice data and image data. It's being used.

In general, a direct sequence transmitter / receiver requires a code synchronization circuit in the receiver, which complicates the receiver and causes a problem in synchronization acquisition time. Therefore, as a means of simplifying the receiving device and shortening the synchronization acquisition time, together with the data modulated wave frequency-spread on the transmitting side,
Simultaneous transmission of spread spectrum waves (reference signals) with different center frequencies spread by exactly the same spreading code, and this 2
A reference signal transmission method is adopted in which a code synchronization circuit is made unnecessary by multiplying waves and despreading.

Hereinafter, a direct sequence transmission / reception apparatus using a conventional reference signal transmission method will be described.

FIG. 6 shows a block connection diagram of a direct spread system transmitter / receiver using a conventional reference signal transmission system.

In FIG. 6, 17 is _a first local oscillator of frequency f _a , 18 is a second local oscillator of frequency f _b , 1
Reference numeral 9 is a spreading code generator, 20 is a first multiplier for multiplying the data signal by the output signal of the first local oscillator 17, and 21 is a first multiplication for spreading the frequency to the bandwidth f _SS with a spreading code. A second multiplier for multiplying the output signal of the spreader 20 by the spread code from the spread code generator 19, and 22 is also the output signal of the second local oscillator 18 for spreading the frequency with the spread code and the spread code generation. Third multiplication with the spreading code from the device 19
2 is a combiner of the output signal of the second multiplier 21 and the output signal of the third multiplier 22, and the above are the constituent elements of the transmitter.

Reference numeral 24 denotes _a first band pass filter (hereinafter abbreviated as BPF) having _a center frequency f _a and a pass band width f _SS ,
25 is a second BP having a center frequency f _b and a pass bandwidth f _SS
F and 26 are multipliers of the output signals of the BPFs 24 and 25, and 27
Is _a third BPF having _a center frequency (fa- _fb ) and a pass bandwidth of the data bandwidth d, 28 is a data demodulator, and the above are components of the receiver.

The operation of the direct sequence transmission / reception apparatus configured as described above will be described below.

The output signal (carrier wave) of the first local oscillator 17 and the data signal are data-modulated by the first multiplier 20. This data modulated wave is phase-modulated with the spreading code output from the spreading code generator 19 using the second multiplier 21, and spread over a wide band. Similarly, the output signal of the second local oscillator 18 is phase-modulated with a spreading code using the third multiplier 22 and spread in a wide band, and this is used as a reference signal. However, in order to prevent the interference of these two spread waves, f _a and f _b are set so that their signal bands do not overlap.

The synthesizer 23 synthesizes the two spread signals and transmits them.

On the reception side, the multiplier 26 multiplies the outputs of the BPFs 24 and 25 having the center frequencies f _a and f _b and the pass band width f _SS . The output signal of the multiplier 26 is set to the third BPF 27.
After filtering with, the data is regenerated by the data demodulator 28.

Next, the manner in which data is demodulated with this configuration will be described while showing the frequency spectrum of the signal in each block of the transceiver.

The output signal of the first local oscillator 17 is represented by A sin (ω _a t + φ ₁ ) where the amplitude is A and the angular frequency is ω _a = 2πf _a . The output signal of the second local oscillator 18 is represented by B sin (ω _b t + φ ₂ ) where the amplitude is B and the angular frequency is ω _b = 2πf _b . The output signal of the first multiplier 20, a data modulation signal θ (t) = ± π, represented by _{A sin (ω a t + θ} (t) + φ 1). The output signal of the second multiplier 21, a spreading code a (t) = ± 1, represented by A · a (t) sin ( ω a t + θ (t) + φ 1). The output signal of the third multiplier 22 is represented by B · a (t) sin (ω _b t + φ ₂ ). The output signal of the combiner 23 (transmission signal) is represented by A · a (t) sin ( ω a t + θ (t) + φ 1) + B · a (t) sin (ω b t + φ 2).

On the other hand, on the receiving side, the output signal of the multiplier 26 is C = A · B / 2, φ ₃ = φ ₂ −φ ₁ , φ ₄ = φ
Putting ₁ + φ ₂ and using a (t) ² = 1

[0015]

[Equation 1]

It is represented by The output signal of the third BPF 27 is represented by C cos {(ω _b −ω _a ) t + θ (t) + φ ₃ }.

By the way, since the spread code has a repeating period, the spread wave has a line spectrum. Therefore, the frequency spectrum of the signal in each block is as shown in FIG. 7A shows the frequency spectrum of the output signal of the first local oscillator 17, FIG. 7B shows the frequency spectrum of the output signal of the second local oscillator 18, and FIG. 7C shows the first multiplier 20. 7 (e) of the output signal (spread signal) of the second multiplier 21 in FIG. 7 (d).
Of the output signal (reference signal) of the third multiplier 22 shown in FIG.
FIG. 7F shows the output signal (transmission signal) of the combiner 23.
7G shows the output signal (despread signal) of the multiplier 26, which is shown in FIG.
(H) shows the respective frequency spectra of the output signal of the third BPF 27.

Since the spreading code has a property of becoming "1" when squared, if the data modulation wave and the reference signal are perfectly synchronized on the receiving side, the spreading component will be canceled by the multiplier 26. , The output frequency component of the multiplier 26 is shown in FIG.
In this way, the data demodulator 28 can reproduce the data.

[0019]

[SUMMARY OF THE INVENTION However, in the configuration of the conventional direct spread system transceiver of said center frequency spacing of the local oscillator 17 and 18 for preventing interference of two waves which are directly spread (f _a ~f _b ) needs to be large,
Therefore, when the bandwidth required for the entire transmission signal shown in FIG. 7 (f) becomes large and the transmission bandwidth is limited, the spread bandwidths of the two waves (FIGS. 7 (d) and 7 (e)) Is greatly limited. Since the interference suppression capability on the receiving side is proportional to [spreading bandwidth / data bandwidth], if the spreading bandwidth is limited, the interference resistance and noise resistance are significantly reduced.
Also, since the code length is shortened due to the limitation of the spreading bandwidth,
Confidentiality is also significantly reduced.

Further, if the difference in center frequency between the two waves is large,
Since the transmission characteristics of the two waves are greatly different, the distortion caused by the transmission paths is not canceled by the multiplier 26, and two BPFs 24 and 25 having different pass bands are required on the receiving side, and the delay characteristics of the two BPFs 24 and 25 are required. Do not completely match, so that a phase difference of two waves occurs after passing through the BPFs 24 and 25. As a result, since the spread code cannot be erased accurately in the multiplier 26, the formula of (Equation 1) is not satisfied, and there is a problem that data reproduction becomes difficult.

The present invention is intended to solve the above-mentioned conventional problems, and is more resistant to noise, interference, and interference than the conventional structure.
A first object is to provide a transmitter / receiver which is excellent in confidentiality and can easily reproduce data, and a second object is to provide a transmitter / receiver capable of frequency multiplexing.

[0022]

In order to achieve the above-mentioned first object, in the first transmitting / receiving apparatus according to the present invention, the difference between the oscillation frequencies is such that d is the data bandwidth, k is 0 or a positive value. The first and second represented by d · k + d / 2 as an integer of
Local oscillating means, a spreading code generating means for generating a spreading code having a repetition period such that a line spectrum interval is equal to or larger than the data bandwidth d, and the first local oscillating means with a data signal. Of the output signal of the first modulation means, second modulation means of modulating the output signal of the first modulation means with the spread code, and output signal of the second local oscillation means of the spread code. Corresponding to a frequency band of a transmission signal, and a transmission device including a third modulation unit that spreads the frequency with a transmission unit, and an addition unit that adds an output signal of the second modulation unit and an output signal of the third modulation unit. A first band pass filter, a squaring means for squaring the output signal of the first band pass filter, and a center frequency band having a difference frequency between the first and second local oscillating means of the transmitter. Band of width d A second band-pass filter having a pass characteristic, is one that is constituted by a receiving apparatus comprising demodulating means for demodulating the data from the output signal of said second band-pass filter.

In order to achieve the second object,
In addition to the configuration of the first transmission / reception device described above, a second transmission / reception device according to the present invention is characterized in that one of the first and second local oscillation means is provided with an oscillation frequency of the first local oscillation means and f _{1 , f 2 ‥‥ f k ‥‥ f} n ( however, f _k is, n a positive integer, k is 0 or a positive integer, f _k = n · d ·
(represented by k + d / 2), the third local oscillating means having n frequency oscillating functions with a frequency difference of (k + d / 2), and the other is changed to the first local oscillating means. The first bandpass filter and the second bandpass filter are changed to a transmission device in which a switch for switching the output and a synchronization circuit for transmitting a switching signal to the switch for each block of the time-division multiplexed data signal are added. The reception device in which the filter is changed to a third bandpass filter corresponding to the frequency band of the transmission signal in the changed transmission device and a fourth bandpass filter having a center frequency f _k and a bandwidth d, respectively. It is configured such that it has n units of frequency multiplexing.

[0024]

According to the first transmission / reception apparatus, the two waves of the transmission signals do not interfere with each other, so that the intervals between the center frequencies of the two waves can be arranged sufficiently narrower than in the conventional case, and the bandwidth of the entire transmission signal can be increased. Since it is smaller than the conventional one, even if the bandwidth is limited, the spread bandwidth of each of the two waves can be made larger than that of the conventional one, and the spread code length can be made larger, resulting in noise resistance and interference resistance. ， It becomes excellent in confidentiality. Further, since the transmission path characteristics of the two waves are substantially the same, the distortion generated on the transmission path is also canceled by the squaring means,
Moreover, the two band pass filters (BPF) that were conventionally required in the first stage of the receiver can be replaced by one band pass filter, and the phase shift of the two waves caused by the difference in the characteristics of the band pass filters does not occur. The spread code is accurately erased by the square calculation means of the stage, and the data reproduction is facilitated.

Further, according to the second transmitting / receiving device, frequency multiplexing can be performed by appropriately selecting the frequency difference f _k (k is a positive integer of 1 to n) between the oscillation frequencies of the two waves.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A transmitting / receiving apparatus according to embodiments of the present invention will be described below with reference to the drawings.

First Embodiment First, a first embodiment of the present invention will be described. FIG. 1 is a block connection diagram of a transmitting / receiving apparatus according to the first embodiment.

Referring first to FIG. 1, the structure of the transmitter will be described. 1 is a first local oscillator of frequency F1, 2 is a second local oscillator of frequency F2, 3 is a spread code generator, 4 is a data signal, and the output signal of the first local oscillator 1 is two-phase phase modulated (BPSK). ) Is a second multiplier for multiplying the spread code from the spread code generator 3 by the output signal of the first multiplier 4 to spread the frequency, and 6 is a spread code and a second A third multiplier that multiplies the output signal of the local oscillator 2 to generate a frequency-spread reference signal, and 7 is an adder that combines the output signal of the second multiplier 5 and the output signal of the third multiplier 6. It is a vessel.

The output signal of the adder 7 is the output signal (transmission signal) of the transmitter. The transmitter is composed of the above blocks.

The operation of the transmitter configured as described above will be described. In the local oscillators 1 and 2, the frequency difference [F2-F1] is F2-F1 = 2 with respect to the bandwidth d of the data signal. Generate carrier waves C1 and C2 having a frequency that satisfies d + d / 2.
The spreading code generator 3 generates a pseudo noise (PN) code sequence having a repetition period T that satisfies d = 2π / T for the bandwidth d of the data signal. This is a spread code (PN code).

The first multiplier 4 and the external data signal
Carrier wave C1 from the local oscillator 1 of 2 phase modulation (BP
SK) That is, the output signal of the first multiplier 4 is a BPSK modulated wave having a center frequency F1 and a bandwidth d. The spread code (PN code) becomes an input signal to the second and third multipliers 5 and 6, the second multiplier 5 spreads the frequency of the BPSK modulated wave, and the third multiplier 6 outputs the second local oscillator. The carrier C2 from 2 is frequency-spread. The two spread waves are combined by the adder 7 and transmitted. Hereinafter, the output signal of the second multiplier 5 will be referred to as a modulated spread wave, and the output signal of the third multiplier 6 will be referred to as a reference signal.

Next, the output waveform of this transmitter will be described with reference to FIG.

Since the spread code (PN code) is a pulse signal having a repetition period T, the spread wave has a line spectrum. Therefore, the waveform of the diffusion wave is as shown in FIG. The horizontal axis of FIG. 2 represents frequency and the vertical axis represents signal strength. Figure 2 (a)
Is the waveform of the modulated spread wave, and FIG. 2B is the waveform of the reference signal. FIG. 2C shows the waveform of the combined signal of the above two waves. In FIG. 2C, the solid line shows the reference signal and the broken line shows the modulated spread wave. As shown in FIG. 2 (c), the two diffused waves have overlapping bands, but do not interfere with each other.

In this embodiment, the frequency difference [F2-F1] between the first and second local oscillators 1 and 2 and the bandwidth d of the data signal satisfy the relationship of F2-F1 = 2.d + d / 2,
Further, since the reference signal has a line spectrum (FIG. 2 (b)), the modulated spread wave and the reference signal have almost the same frequency band, but their signal components are as shown in FIG. 2 (c). Since they do not overlap at all, they do not interfere with each other.

In this embodiment, the frequency difference [F2-F
1] is set to F2-F1 = 2 · d + d / 2, but it may be set to F2-F1 = k · d + d / 2 where k is a positive integer.

Next, the structure of the receiver will be described. In FIG. 1, 8 is a first band pass filter (BPF) whose center frequency is set to the same pass band as the band of the transmission signal, that is, (F1 + F2) / 2, and 9 is the first band pass filter 8
2 is a second band pass filter having a center frequency of [F2-F1] and a pass band width of d, and 11 and 12 are components of data demodulation means. Is a carrier recovery circuit for recovering a carrier of frequency [F2-F1] from the output signal of the second band pass filter 10, and 12 is BPSK by multiplying the output signal of the second band pass filter 10 and the recovered carrier. It is a multiplier that demodulates (two-phase phase demodulation) and reproduces data. In this embodiment, the carrier recovery detection method is used as the data demodulation means. The receiver is composed of the above blocks.

The operation of the receiver configured as described above will be described. The output signal of the first band pass filter 8 is squared by the squaring calculator 9. At this time, 2 of the transmission signal
The transmission line characteristics of the waves are almost the same, and since there is no phase difference between the two waves in the first bandpass filter 8, the spread code (P
The N code) will be exactly canceled. As a result,
The output signal of the square calculator 9 is

[0038]

[Equation 2]

It is represented by Here, it is utilized that a (t) ² = 1 and 2 · θ (t) = ± 2π. Also, ω ₁ = 2π · F1, ω ₂ = 2π · F
^{2, D = A 2/2} , which is E = B ^2/2.

Of the output components, the component of C cos {(ω ₁ −ω ₂ ) t + θ (t) + φ ₃ } is the BPSK modulated wave of the carrier frequency [F2-F1], so this component is 2 band pass filter 10
And the data is reproduced by the carrier wave reproducing circuit 11 and the multiplier 12.

Next, the process of this data reproduction will be described with reference to the waveform diagram of FIG. In FIG. 3, the horizontal axis represents frequency and the vertical axis represents signal strength. FIG. 3A shows the frequency spectrum of the output signal of the first bandpass filter 8, and FIG.
3B shows the square calculator 9, FIG. 3C shows the second band pass filter 10, and FIG. 3D shows the carrier recovery circuit 11.
FIG. 3E shows the frequency spectrum of each output signal of the multiplier 12.

As described above, it has been shown that the structure of the present receiver enables data reproduction.

Second Embodiment Next, a second embodiment of the present invention will be described. FIG. 4 is a block connection diagram of a transmission / reception device in the second embodiment.

Referring to FIG. 4, first, the structure of the transmitter will be described. Reference numeral 13 denotes frequencies different from the oscillation frequency F1 of the first local oscillator 1 in FIG. 1, F1 + f ₁ and F1 +.
_{f 2, F1 + f 3 ‥‥} F1 + f k ‥‥ F1 + f 8 ( although, f _k is represented by _{f k = n · d · k} + d / 2) third local oscillator having eight frequency oscillation source, 1 is shown in FIG.
The second local oscillator 2 is replaced with the first local oscillator 1, and the oscillation frequency of the first local oscillator 1 is F1. Reference numeral 14 is a switch for switching the output signal of the third local oscillator 13, 15 is a clock for timing the output of the data signal, 16 is a counter, 3 is the spreading code generator 3 of FIG. 1, 4 is the first code of FIG. 1 are the second multipliers 5 and 6 of FIG. 1, the third multipliers 6 and 7 of FIG. 1 are the same as the adder 7 of FIG. 1, and these are the same as those of the first embodiment. Works exactly like the transmitter. Reference numerals 1, 3, 4, 5, 6, 7 correspond to those in FIG.

Next, referring to FIG. 5, the local oscillator 13, the switch 14 constituting the synchronous circuit, and the clock 1
5. The operation of the transmitter having the above configuration will be described, centering on the counter 16.

In FIG. 5, the horizontal axis represents time and the vertical axis represents each output signal. FIG. 5A is an output clock of the data signal, and FIG.
(B) is a time division multiplexed data signal with a division number of 8,
d1 to d8 indicate each data block. In this embodiment, each data block is switched every 5 clocks. The signal of the clock 15 is counted by the counter 16,
The carry output signal is output by the counter 16 every 5 clocks. FIG. 5C shows the carry output signal. The switch 14 is switched by the carry output signal. FIG. 5D shows the output signal of the third local oscillator 13 switched by the switch 14. The output signal of the third local oscillator 13 is switched for each data block multiplexed in this way.

The above is the configuration and operation of the transmitter.

Next, the structure of the receiver will be described. Eight receivers are used. Each receiver has the same configuration as that of the first embodiment. 9 is the same as the square calculator 9 of FIG.
1 is the same as the carrier recovery circuit 11 of FIG.
It is the same as the multiplier 12 of.

Then, the first band-pass filter 8 is changed to a third band-pass filter 8'having a center frequency [F1 + f _n / 2] (where n is an integer of 1 to 8). In addition, the second bandpass filter 10 is changed to a fourth bandpass filter 10 'having a center frequency f _n, and n
Third band pass filter 8'having frequency characteristics of 1 to 8
Further, frequency multiplexing is performed by reproducing data for each data block by using eight receivers each provided with the fourth band pass filter 10 '.

Although the frequency multiplexing number is set to 8 in the present configuration, it may be set to any n (n is a positive integer). The order of switching the output signal of the third local oscillator 13 is arbitrary. It may be connected to a specific receiver without switching.

In the first and second embodiments, the data modulation method is BPSK (two-phase phase modulation), but another modulation method (QPSK, FSK, etc.) may be used.

The data demodulating means may be a demodulating means other than the carrier wave reproducing / detecting method.

[0053]

As described above, according to the first transmission / reception apparatus of the present invention, since the spread bandwidth can be widened, the noise resistance, the interference resistance, and the confidentiality are excellent, and
Since the transmission path characteristics of the two waves are almost the same, the data reproduction by the receiving means becomes easy.

Further, according to the second transmitting / receiving apparatus of the present invention, frequency multiplexing can be enabled.

[Brief description of drawings]

FIG. 1 is a block connection diagram of a transmission / reception device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing frequency characteristics of an output signal of a transmitter in the first embodiment.

FIG. 3 is a diagram showing frequency characteristics of an output signal of a receiver in the first embodiment.

FIG. 4 is a block connection diagram of a transmission / reception device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a frequency multiplexing process of transmission data in the second embodiment.

FIG. 6 is a block connection diagram of a conventional transmission / reception device.

FIG. 7 is a diagram showing frequency characteristics of an output signal of a conventional transceiver.

[Explanation of symbols]

 1 ... 1st local oscillator 2 ... 2nd local oscillator 3 ... Spread code generator 4 ... 1st multiplier (1st modulation means) 5 ... 2nd multiplier (2nd Modulation means 6 ... Third multiplier (third modulation means) 7 ... Adder 8 ... First bandpass filter 9 ... Square calculator 10 ... Second bandpass filter 11 ... Carrier wave recovery circuit 12 Multiplier 13 Third local oscillator 14 Switch 15 Clock 16 Counter 8'third bandpass filter 10 'Fourth bandpass filter

Claims (2)

[Claims] 1. A first and a second local oscillation means represented by d · k + d / 2, where d is a data bandwidth, k is 0 or a positive integer, and a line spectrum Spreading code generating means for generating a spreading code having a repetition period whose interval is equal to or larger than the data bandwidth d, and a first modulating the output signal of the first local oscillating means with a data signal. Modulating means, and the first
Second modulating means for modulating the output signal of the modulating means by the spreading code, third modulating means for frequency spreading the output signal of the second local oscillation means by the spreading code, and the second
Of the modulating means and the output signal of the third modulating means, a transmitting device including an adding means, a first band-pass filter corresponding to a frequency band of the transmitting signal, and the first band. Squaring means for squaring the output signal of the pass filter, and the first and second center frequencies of the transmitter.
Of the local oscillating means and a demodulating means for demodulating data from an output signal of the second band-pass filter. A transmitter / receiver characterized by being performed. 2. One of the first and second local oscillating means is provided with an oscillating frequency of the first local oscillating means and f ₁ , f.
₂ ... f _k ... f _n (where f _k is a positive integer,
f _k = n · d · k + d /, where k is 0 or a positive integer
2) is used as the third local oscillating means having n frequency oscillating functions, and the other is changed to the first local oscillating means, and the output of the third local oscillating means is changed. A switch for switching and a transmitter having a synchronous circuit for sending a switching signal to the switch for each block of the time-division multiplexed data signal are changed to a transmitting device, and the first band-pass filter and the second band-pass filter are provided. Respectively
The receiver includes n receivers which are changed to a third bandpass filter corresponding to the frequency band of the transmission signal in the changed transmitter and a fourth bandpass filter having a center frequency f _k and a bandwidth d. A transmitter / receiver characterized in that the transmitter / receiver is frequency-multiplexed.