JPH03265316A - Spread spectrum transmitter and receiver - Google Patents

Abstract

PURPOSE:To realize a spread spectrum communication transmitter with strong disturbance immunity to external noise and external interference by providing an emphasis circuit emphasizing the high frequency region of a signal subject to spread spectrum processing. CONSTITUTION:An emphasis circuit 15 is provided between a multiplier 3 and a balanced modulator 5. The emphasis circuit 15 is an amplifier emphasizing a signal at a high frequency region and amplifies the output signal of the multiplier 3 to a maximum amplitude within a level permitted for a weak radio installation. Moreover, a filer 16 is provided between a balanced modulator 5 and an antenna 6, and the filter 16 amplifies the signal within a prescribed frequency range including a carrier angular frequency omegac at a nearly constant gain and outputs the result. Thus, the spread spectrum transmitter immune to external noise or external interference is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a spread spectrum transmitter and receiver used in weak radio equipment and the like.

“Conventional technology” According to Japan's Radio Law, low-power wireless equipment (approximately 10 N
mW) and weak radio equipment that does not require a license.

Among these, for micro-power wireless equipment, the frequencies used, modulation methods, uses, etc. are institutionalized as technical standards, and the range of use of the equipment is limited.

On the other hand, weak radio equipment has no institutionalized technical standards such as limitations on the range of use of the equipment, so there is a high degree of freedom in its use. As a wireless communication method using such weak radio equipment, a spread spectrum communication method is very advantageous in that the spectrum is spread to make the power weaker and then transmitted.

FIG. 12 is a block diagram showing an example of the configuration of a conventional spread spectrum transmitter. In FIG. 12, ■ is an input terminal into which a data signal to be transmitted is manually input, 2 is a code generator, and if the bit period of the data signal is T, then Tc=T
A spreading code that changes at a period of /N (N is an integer) is generated. As this spreading code, a highly random time series pattern, such as a PN sequence code, is used. 3 is a multiplier that multiplies the spreading code by the data signal.

Further, 4 is an input terminal to which a carrier wave signal cosωct (where ω is a carrier wave angular frequency) is input, and 5 is a carrier wave signal c
A balanced modulator modulates osωct with the output signal of the multiplier 3, and 6 is a transmitting antenna from which the output signal of the balanced modulator 5 is radiated as a radio wave.

FIG. 13 is a block diagram showing an example of the configuration of a conventional spread spectrum communication receiver. In FIG. 13, 7 is a receiving antenna, 8 is a code generator that generates a spreading code with the same pattern as code generator 2 in FIG. 10 is the local oscillation signal c
A balanced modulator modulates os (ω0+ωty) t with a spreading code, and 11 is a multiplier that multiplies the signal received by the receiving antenna 7 and the output signal of the balanced modulator 10 to output an intermediate frequency signal.

Further, 12 is a band pass filter (hereinafter referred to as BPF) that passes an intermediate frequency signal, 13 is a demodulator that demodulates a data signal from the output signal of BPF 12, and 14 is an output terminal from which the data signal is output.

In such a configuration, first, in the transmitter shown in FIG. 12, when a data signal having a power density spectrum shown in FIG. Multiplied. Then, as shown in FIG. 15, the multiplier 3 outputs a signal having a power density spectrum in which the power density spectrum of the data signal is spread N times in the frequency direction and the power density is suppressed to 17H. .

Then, in the balanced modulator 5, the carrier wave signal cosωet is modulated by the output signal of the multiplier 3. As a result, a signal having a power density spectrum shown in FIG. 16 is output from the balanced modulator 5, and this output signal is sent out from the transmitting antenna 6 as a radio wave.

On the other hand, in the receiver of FIG. 13, at balance level #1H1O, the local oscillation signal cos(ω0+ωrr)t is modulated by the spreading code supplied from the code generator 8, and is provided to the multiplier 11.

When a radio wave having a power density spectrum shown in FIG. 16 is received by the receiving antenna 7, the multiplier 11
The received signal is multiplied by the output signal of the balanced modulator IO. As a result, an intermediate frequency signal having a power density spectrum shown in FIG. 17 is output from the multiplier 11.

Then, the intermediate frequency signal passes through the BPF 12 and is demodulated!
113 , the data signal is demodulated by the demodulator 13 and output from the output terminal 14 .

``Problems to be Solved by the Invention'' By the way, the conventional spread spectrum transmitter and receiver described above have a drawback in that they have low resistance to interference with external noise, external interference, and the like.

As a countermeasure for this, for example, conventionally, a ! A BPF with the characteristics shown in Figure 8 was inserted, but for example, Figure 19 (a)
As shown in FIG.
As shown in FIG. 9(b), the narrowband interference wave f@ is input to the multiplier 11 at the same level, causing reception interference.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a spread spectrum quadruple transmitter and a receiver that have high resistance to external noise and interference.

``Means for Solving the Problems'' The invention according to claim 1 provides a spread spectrum transmitter that modulates a carrier wave with a signal that spreads the spectrum of a data signal using a spreading code and transmits the signal. It is characterized by comprising an emphasis circuit that emphasizes the area.

Further, the invention according to claim 2 provides a spread spectrum receiver for receiving radio waves transmitted from the transmitter according to claim 1, in which a high frequency region of a signal subjected to spectrum spreading in the transmitter of the received signal is provided. It is characterized in that it includes a de-emphasis circuit that de-emphasizes a corresponding frequency domain, and demodulates the data signal based on the output of the de-emphasis circuit.

"Operation" According to the present invention, the transmitter emphasizes and transmits the high frequency region of the spread spectrum signal in the emphasis circuit.

Then, in the de-emphasis circuit, the receiver de-emphasizes the frequency region of the received signal that corresponds to the high frequency region of the signal that has been spread spectrum in the transmitter, and then outputs the data signal based on the output of the de-emphasis circuit. Demodulate.

Therefore, even if the radio waves received by the receiver include narrowband jamming waves, the level of the jamming waves is lowered in the de-emphasis circuit, so that the anti-jamming performance is improved.

"Embodiment" Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIGS. 1 and 2 are block diagrams showing the configurations of a spread spectrum transmitter and a receiver according to an embodiment of the present invention, respectively. In these figures, parts corresponding to those in FIGS. 12 and 13 are shown. are given the same reference numerals and their explanations will be omitted.

In FIG. 1, between the multiplier 3 and the balanced modulator 5,
An emphasis circuit 15 is newly provided. The emphasis circuit 15 is, for example, an amplifier that emphasizes signals in a high frequency range, as shown in FIG. amplify.

Additionally, a filter 1 is provided between the balanced modulator 5 and the antenna 6.
6 has been newly established. An example of the pass band characteristics of this filter 16 is shown in FIG. This filter 16 has a carrier wave angular frequency ω. A signal in a predetermined frequency range including , is amplified with a substantially constant gain and output.

Furthermore, in FIG. 2, a de-emphasis circuit (BPF) I7 is newly provided between the antenna 7 and the multiplier 11. This de-emphasis circuit I7 has a carrier wave angular frequency ω, for example, as shown in FIG. It has a gain frequency characteristic in which the transmission gain peaks near the peak and the gain gradually decreases as it moves away from the peak.

In such a configuration, first, in the transmitter of FIG. 1, when a data signal having the power density spectrum shown in FIG. 14 is input from the input terminal 1, the transmitter of FIG. A signal having a power density spectrum shown in FIG. 15 is output from the multiplier 3.

Then, the output signal of the multiplier 3 is transmitted to the emphasis circuit 15.
As a result, the signal is amplified according to the gain frequency characteristic shown in FIG. 3, and is output as a signal having a power density spectrum shown in FIG. 6, in which the high frequency region is emphasized. The balanced modulator 5 modulates the carrier signal cosωct with the output signal of the emphasis circuit 15 and outputs a signal having a power density spectrum shown in FIG.

Then, the output signal of the balanced modulator 5 is band-limited by passing through the filter 16 to become a signal having a power density spectrum shown in FIG. 8, and this signal is radiated from the transmitting antenna 6 as a radio wave.

Note that the power of the side lobe in the power density spectrum shown in FIG. 7 is about 10% of the total power, so even if this side lobe is removed by the filter 16, the signal deterioration caused by it can be ignored. .

Next, in the receiver shown in FIG. 2, when the receiving antenna 7 receives a radio wave having the power density spectrum shown in FIG. oppressed, 9th
A signal having the power density spectrum shown in the figure is output.

On the other hand, a balanced modulator! 0, the local oscillator signal cos(ω.

+ωxF)t is modulated by the spreading code, and the multiplier 11
given to.

Then, the de-emphasis circuit 1
The output signal of 7 is multiplied by the output signal of the balanced modulator 10, and an intermediate frequency signal having a power density spectrum shown in FIG. 10 is output from the multiplier 11.

Then, the intermediate frequency signal passes through the BPF 12 to remove unnecessary bands and is input to the demodulator 13, where the data signal is demodulated from the intermediate frequency signal and output from the output terminal 14. .

As explained above, in the emphasis circuit 15 of the transmitter, the output signal of the multiplier 3 is amplified to the maximum within the range allowed to be output as a weak radio equipment, and the characteristics of the de-emphasis circuit 17 of the receiver are Since the characteristics shown in FIG. 5 are adopted, for example, a radio wave containing a narrowband interference wave fa as shown in FIG.
Even when the signal is received by the de-emphasis circuit 17, the level is sufficiently attenuated, as shown by the symbol f in FIG. 11(b). In this way, the anti-jamming performance is improved.

Furthermore, since the emphasis circuit 15 is provided in the transmitter, it is easy to configure the BPP (de-emphasis circuit 17) provided in the receiver.

In the above embodiment, the filter 16 is inserted between the balanced modulator 5 and the transmitting antenna 6, but it may also be inserted between the emphasis circuit 15 and the balanced modulator 5. .

Further, in the embodiment described above, wireless equipment was described, but the present invention may also be applied to wired equipment.

"Effects of the Invention" As explained above, the present invention has the effect of realizing a spread spectrum transmitter and receiver that are resistant to external noise and interference.

[Brief explanation of drawings]

1 and 2 are block diagrams showing the configurations of a spread spectrum transmitter and a receiver according to an embodiment of the present invention, respectively. FIG. 3 is a diagram showing an example of the gain frequency characteristic of the emphasis circuit 15, and FIG. 5 is a diagram showing an example of the passband characteristics of the filter 16, and FIG.
FIGS. 6 to 8 are diagrams showing examples of the power density spectra of signals output from each part in FIG. 1, and FIG. 91! il and FIG. 10 are diagrams showing examples of power density spectra of signals output from each part in FIG. 2, respectively, and FIGS. 11(a) and (b)
are figures for detailed explanation of this invention, respectively.
13 and 13 are block diagrams showing configuration examples of a conventional spread spectrum transmitter and a receiver, respectively, and FIGS.
16 is a diagram showing an example of the power density spectrum of the signal output from each part of the 12vA, and FIG. 1711 is a diagram showing an example of the power density spectrum of the signal output from the multiplier 11 of FIG. 181! l is a diagram showing an example of the characteristics of BPP provided in a conventional receiver, No. 19m
(a) and (b) are diagrams for explaining the problems of conventional receivers, respectively. 15...Emphasis circuit, 17...
De-emphasis circuit.

Claims (2)

[Claims] (1) A spread spectrum transmitter that modulates a carrier wave with a signal obtained by spreading the spectrum of a data signal using a spreading code and transmitting the signal, characterized by comprising an emphasis circuit that emphasizes a high frequency region of the signal subjected to the spread spectrum. Spread spectrum transmitter. (2) In a spread spectrum receiver that receives radio waves transmitted from the transmitter according to claim 1, among the received signals,
A spread spectrum device comprising: a de-emphasis circuit that de-emphasizes a frequency region corresponding to a high frequency region of a signal subjected to spectrum spread in the transmitter; and a data signal is demodulated based on the output of the de-emphasis circuit. Receiving machine.