JPH03191630A - Spread spectrum radio communication equipment - Google Patents

Abstract

PURPOSE:To simplify the circuit constitution and to obtain the spread spectrum radio equipment which can be expanded to a consumer field by using a multiplying means for reverse spreading a detected spread spectrum signal by a squaring operation. CONSTITUTION:A voice (a) from a microphone M is FM-modulated 42 and becomes a signal (b) of a spectrum, and is supplied to a multiplier 2 through a BPF 11. In such a state, a spreading code from a spreading code generating circuit 44 is multiplied and becomes a spreading signal (c) of a spectrum. This spreaded signal (c) is transmitted from an antenna A through a multiplier 3, a BPF 12 and a DUP 31. A radio wave from the other station received by the antenna A is supplied to a COM filter 9. The spreading signal (c) which passes through this COM filter 9 is subjected to square-law detection and spreaded reverse spreaded thereby, and demodulated by an FM demodulating circuit 48 through a BPF 14. This demodulated sound signal (a) is outputted from a loudspeaker S.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spread spectrum wireless communication device that has achieved significant improvements.

[Technical background]

Spread spectrum:
Spread spectrum modulation (SS modulation) used in wireless communications (hereinafter also referred to as "SSN") is a method that converts information signals (often primary modulated) into broadband noise-like spread code signals (hereinafter simply referred to as "spread code"). ”),
This is a method that spreads over a very wide band. Such spread spectrum wireless communication has extremely high confidentiality, is resistant to external interference, noise, and intentional interference, can coexist with conventional systems, can be managed using address codes, and has low power density, so it can be transmitted using very weak power. Moreover, it has many features such as being able to multiplex within the same frequency band by changing the pseudo-noise code. These features have been re-recognized, and applications are now progressing not only in the field of communication technology but also in various fields, and are beginning to be applied to consumer devices.

[Conventional technology]

The basic principle of a spread spectrum wireless communication device (hereinafter also simply referred to as a "communication device") will be explained with reference to FIGS. 8 and 9. FIG. 8 is a basic configuration diagram of the communication device, and FIGS. 9(A) to (E) are spectral waveform diagrams at each component. In FIG. 8, the spreading code generation circuit 4
4 and 46 generate M-sequence spreading codes based on clock pulses SC(t) having the same number of pulses (frequency), and supply them to a spreading modulation circuit 43 and a despreading circuit 45, respectively. Pseudo-noise codes (especially M-sequence codes) are commonly used as spreading codes, so they are called pseudo-noise codes or PN (P
It is also sometimes called "seudo No.1se) code".

The primary modulation circuit 42 of station A, which is the transmission (modulation) side, first modulates the information signal with a carrier wave (signal Fr in FIG. 9(^)). Wave F
1 is the spreading code (F sa
; see (B) in the same figure), the spread modulation circuit 43 performs secondary modulation (in some cases, after further amplification), and transmits (F ss ) from the antenna A1. The primary modulation is frequency modulation. (FM) and PSK (Phase 5hi
ft Keying) modulation, etc. Note that the spreading code (PN code) needs to be as random noise-like as possible and have a constant period (in order to extract the code on the receiver side).

Next, the configuration, functions, etc. on the receiving (demodulating) side will be explained. At station B, which is the receiving side, a signal F18 obtained from the antenna A2 by a predetermined filter and a high-frequency amplifier is despread in a despreading circuit 45 using a spreading code from a spreading code generation circuit 46.

This spreading code generating circuit 46 is the spreading code generating circuit 4 of station A.
4 is synchronized.

By the way, the radio waves that enter antenna A2 are not limited to only F18, but as shown in FIG. 9(C), radio waves from other SS stations (F28, F38...), There are radio waves (Fn) from Therefore, by performing despreading in the despreading circuit 45, the desired radio wave F'ts as shown in FIG. 47, most of the components other than Fla are removed (see (E) in the same figure), and the demodulation circuit 4
8, the signal is demodulated to the original information signal and output.

In addition, as can be seen in the same figure (E), the filter 47 (
- In addition to F'ts, the interference wave Fn from the inter-shell 41 and a part of the SS waves of other stations remain in the output signal of the low-pass filter (LPF or bandpass filter for boat fishing). There is.

The ratio of the residual power which is the sum of these and the power of the desired signal is DN
(signal power to interference power ratio), and in order to obtain a large DN ratio, it is advantageous to have a spread band as wide as possible.
It is about 000 times larger.

The basic principle of spread spectrum wireless communication has been described above, and next, specific operations in 1st and 2nd order modulation and demodulation when performing spread spectrum wireless communication will be theoretically explained. Spread spectrum signal 5(t) in spread spectrum wireless communication (F 1a l in FIG. 8 is
The information data is d(t)[+1°-11, spreading code F's
When a is p (B 1.-1) and the carrier wave is cosωat, it is expressed by the following equation.

5(t)=d(t)P(t)cosω(Ht--・-・
-・(1) (However, ωc = 2πfc) This spread spectrum signal s (B is a clock signal for a spread code from an incoming spread spectrum signal during reception (demodulation), and a spread spectrum signal during transmission. d(t)CO3ωct) is multiplied (also called correlation or despreading) with the incoming spread spectrum signal 5(t) and converted into a two-phase PSK signal d(t)CO3ωct. Ru. Furthermore, the regenerated carrier COS
ωct (Actually, synchronous detection is performed by multiplication with c hill ct l, and d [i) (CO3ωct) 2 = +
d(t)(1+CO52ωct) is obtained, and the information data d(t) is demodulated by removing the carrier wave component 2ωat with a filter.

Here, let BD be the bandwidth (main lobe of the spectrum) of the signal d(t)CO3ωct in the two-phase ps, and the bandwidth (
If BP is the main lobe of the spectrum, then the process gain GP in spread spectrum wireless communication is as follows: GP=BP/BD ・・・・・・・・・・・・・・・・・・
... It is expressed as (2). The process gain GP is
The normal design value is several hundred to several thousand, and since interference signals, noise, etc. are suppressed according to this value, the wider the frequency band of the spread spectrum signal relative to the information data d(t), the more resistant it is to interference. The effect of improving performance, noise resistance, etc. is enhanced. In other words, the anti-interference performance and the anti-noise performance are determined by the process gain G.
It is almost uniquely determined by P.

[Problem to be solved by the invention]

In such conventional spread spectrum rV11 wireless communication devices, "despreading" is the most important, and it is not easy to generate the spreading code necessary for this, and currently, AFC control loops, delay lock loops, and multipliers are required. Despreading methods using synchronized loops using matched filters and despreading methods using multipliers are commonly used. Despreading using these configurations all have complicated circuit configurations, and there are problems in terms of adjustment and cost, and it is necessary to solve these problems when deploying them to consumer devices.

On the other hand, as other conventional techniques, for example, ROb13rt C
.

``Spread Spectrum Communication System'' by David Oixon (published by Japan Center for Technology and Economics), p. 123-124, includes FM
Demodulation of a spread spectrum signal obtained by directly spreading the signal is 2
It is stated that spread demodulation can be performed by multiplying the Although this conventional method can be realized with a relatively simple configuration, noise that has entered before the return side and other SS signal components other than the desired SS signal are only squared, and noise and other SS signal components are Since the signal suppression effect is low, it has not yet been put into practical use.

[Means to solve the problem]

The spread spectrum wireless communication device of the present invention includes, on the transmitter side, an FM conversion means for modulating a modulated signal such as voice with a carrier wave and outputting an FM modulated signal, and an FM conversion means for outputting an FM modulated signal from a spreading code generation circuit. A spectrum spreading means performs spread modulation using a spreading code and outputs a spread spectrum signal, and performs up-conversion on the obtained spread spectrum signal and outputs the resultant spread spectrum signal.

The receiver side includes a frequency converter with a multi-channel access function, which down-converts the spread spectrum signal received from the antenna, and a frequency converter with a multi-channel access function. detection means for detecting only the frequency spectrum of the frequency-converted spread spectrum signal by supplying the spread spectrum signal to a comb filter tuned to the spread spectrum signal; a multiplication means for despreading a spread spectrum signal by a square operation; a band r-wave means for passing only the despread output signal obtained by the multiplication means;
It is equipped with a demodulation means for FM demodulating the output signal of the wave means, and further includes a carrier sense function to check and process whether or not a desired spread spectrum frequency band is occupied, and a multi-channel demodulation function to perform FM demodulation of the output signal of the wave means. The above-mentioned problems have been solved by providing a control unit with a multi-channel access function that performs transmission and reception by changing the frequency band used by channel access operations.

〔Example〕

The spread spectrum wireless communication device of the present invention introduces a new concept to carrier sense for making MCA (multichannel access) work.
The present invention combines the 3M communication system and the MCA system to provide a simple wireless communication device that does not cause near-far problems. Hereinafter, one embodiment of the apparatus of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a spread spectrum wireless communication device according to the present invention, in which a single communication device includes both a modulation section (transmission side) and a demodulation section (reception side). Further, FIG. 2 shows a communication device (1a) of the present invention.

ib) is used, and is a principle diagram showing actual communication between the two. In these figures, the same components as those of the conventional example shown in FIG. 8 are given the same reference numerals, and detailed explanation thereof will be omitted.

The communication device 1 of the present invention can be roughly divided into three parts: a transmitter (modulator), a receiver (demodulator), and a controller, which are common to both. In the configuration example shown in Figure 1, a microphone (hereinafter simply "
M, microphone amplifier 17. FM modulation circuit 42. Band P-wave filter (BPF) 11.12 and multiplier 2.
3 is a configuration unique to the transmitting section, which includes BPFs 13 and 14; multiplier 5.6; comb filter (comb-shaped filter) 9. FM demodulation circuit 48, amplifier 18. and speaker S have a configuration unique to the receiving section. Therefore, other components work in common for both, including the spreading code generation circuit 44. LP
F37. Multiplier 5. Detection circuit 32° CPU (central processing unit) 331 Frequency synthesizer 34. DUP (duplexer) 31. The communication device 1 of the present invention, which includes an antenna A and an antenna A, is constructed by connecting these components as shown in the first diagram. Among them, a microphone M, a speaker S, an antenna A, etc. are externally attached as shown in FIG. 2, and the microphone M and speaker S are used by switching between transmission and reception.

FIG. 3 is a block diagram showing the most basic configuration example of the comb filter 9, which is composed of a delay circuit 19 and an adder 23. The delay circuit 19 has a delay time T with respect to the input signal C(t).
(also written as "τ"), and the adder 23 is connected to the delay circuit 1
The output Cd(t) of 9 and the input signal C(t) are combined by 1 and output. With this configuration, the comb filter 9
The characteristic is a comb-shaped output characteristic as shown in FIG. 4 (^). The center angular frequency of the adjacent passband in this figure is ω
Assuming that the plate is ω2, the interval is ((2n −1)To
l”.

Here, To is the 1-bit (1 chip) time length of the clock signal 5C(t) supplied to the spreading code generation circuit 44, and To is the M-sequence code used in the spreading code generation circuit 44, during which the sequence code generation circuit is This is the number of stages of shift registers when shift registers are used. Therefore, 1/T o
indicates the clock rate of the spreading code, and Fig. 4(B)
is the center frequency (carrier wave) of the primary modulation signal as 9 (=ωo
/2π) is the output signal spectrum of the comb filter 9.

Further, the distortion characteristic W(s) of the comb filter 9 is as shown in FIG. This figure shows the characteristics when the delay time τ is 4 μs, and the horizontal axis (frequency) is on a logarithmic scale. The comb filter 9 having such basic characteristics can sufficiently reduce unnecessary noise and other signal components. Hereinafter, the specific method of use and operation of the communication device 1 of the present invention will be explained with reference to FIGS. 1 to 6-7 (spectral diagrams).

First, when transmitting, the user speaks into the microphone M after switching the communication device 1 to a transmitting mode using a changeover switch (not shown). Then, the voice a is amplified by the microphone amplifier 17 and then first-order modulated by the FM modulation circuit 42.Human voice has a frequency of several kHz at most, including harmonic components (
(see Figure 6(A)), a much higher frequency fa than this.
By FM modulating with a carrier having (fb),
Signal b (FHI
, FM2), such FM modulated output signal S is BP
After unnecessary frequency band components are removed by F (band filter) 11, the signal is supplied to multiplier 2, where it is spread by being multiplied by a spreading code from PNG (spreading code generation circuit) 44, The spectrum is a spread spectrum signal (SS signal) C (its main lobe is shown by the broken line SSI) as shown in (D) of the same figure. The modulation signal FM in FIG. 3B is shifted to the right in order to align the positions in the horizontal axis direction. Note that the LPF 37 uses the spreading code signal P (
This is a low-frequency r-wave filter for removing side lobes of t) and supplying only the main lobe to the multiplier 2.4.

The expanded P& signal C is sent to the next stage multiplier 3. The signal is transmitted from antenna A via BPFI 2 and DUP 31, and if necessary, the SS modulation frequency is switched by multiplier 3, and multiplier 3 works as an up-conversion receiver. The up-conversion function means that the detection circuit 32 checks whether the desired spread spectrum frequency band is occupied (carrier sense function) and detects whether the desired frequency band (for example, spectrum S+ in FIG. 7(A)) is occupied. If this is not detected, the oscillation frequency of the frequency synthesizer 34 is shifted toward a higher (or lower) channel (up to the maximum shown in the figure (^)) until an empty frequency band is found. This is an operation 1 function of switching the spectrum up to sn (in stages) and supplying it to the multiplier 3 and the multiplier 6 to be described later. That is, the detection circuit 32. CPU33. The frequency synthesizer 34 and the multiplier 3 (6) constitute a control unit that performs multi-channel access operations, which allows transmission (and reception) to be performed by changing the frequency band used. ing. Note that FIG. 7(B) is a waveform diagram showing an enlarged spectrum of the spectrum in FIG. B) spectra a1 and nl
Next, we will explain how to receive (operation on the receiving part side) 4 When the communication device 1 is switched to the receiving mode, the radio waves from the other station caught by the antenna A are transmitted to the multiplier via the DUP 31 and the BPFI 3. 6. BPFI3
functions to remove unnecessary frequency components other than the main lobe of the SS signal. Furthermore, the multiplier 6 is a down (up) conversion mixer that functions complementary to the multiplier 3, and as a result, even if the spread modulation frequency is switched by the multiplier 3 during transmission, the spread spectrum signal is Since the tuned comb filter 9 is always supplied with 5S (No. 3) of the same frequency band suitable for the above-mentioned comb filter characteristics, efficient demodulation can be performed.

The comb filter 9 generates a spread spectrum (S S
This is a filter that detects only the rg) component. The spread signal C that has passed through the comb filter 9 is despread by square-law detection in the multiplier 5 at the next stage, and is then despread by the BPFI-4.
After removing unnecessary frequency components other than the despread output signal, the FM demodulation circuit 48 demodulates the signal to return to the original audio signal a, which is adjusted to an appropriate volume by the amplifier 18 and output from the speaker S. That is why it is output.

Note that the means for generating the carrier sense function in the control X1 section is to multiply the comb filter output before the start of the communication operation and the spreading code from the spreading code generating circuit 44 in the multiplier 4 and converting it into a narrowband noise signal. However, the signal level may be determined by the detection circuit 32 (line (a) in FIG. 1), or the demodulation noise level generated in the FM demodulation output before the start of the communication operation may be determined. (line (0) in the same figure).

In such a communication device 1, the despreading operation in the demodulator is one of the most important operations, and the operations of the comb filter 9 and multiplier 5 will be explained in detail below.

If the modulated signal such as the audio signal a supplied to the FM modulation circuit 42 is 5inpt, and the carrier wave of the FM modulation circuit 42 is ω (=2πfa), then the FM modulation signal is cos(
It is expressed as ωt+f(t)). Note that f(t) is a modulation signal expressed by the following equation.

f(t)=a f 5inpt/f m...
・・・・・・・・・・・・・・・・・・・・・・・・(3)
However, 4f: frequency shift + f m : modulation frequency Furthermore, the SS signal is spread (secondary modulation) in the multiplier 2 using the spreading code P(t) from the spreading code generating circuit 44 and is caught by the antenna A. The SS signal cH is as follows: C(t) = P (t)CO3(ωt+f(t))
It is expressed as (4). Here, if the level (amplitude) of the SS signal is A1, the SS signal C(t) is C(t) = A 1・p (t)co
s (ωt+f(t))・・・・・・・・・・・・(5
) expressed as 0, t, FM3! passed through the delay circuit 19 forming the comb filter 9! ! The extended signal Cd(t) is
If the amplitude is A2, then Cd(t)=A2・P(t)cos(ωt+f
(t−T)−ω■)・・・・・・(6) Therefore, the added FM signal C(t)+Cd which is the output of the adder 23
(t), that is, the output C+(t) of the comb filter 9, where the amplitude fluctuation component is Env(t) and the phase component is φ(1), C+(t)=C(t)+Cd(t)= P (t)Env(t)cos (ωt +f<
t)+φ(t))---(7), where,
If K is the strength ratio (amplitude ratio) of the FM signal C(t) and the FM delayed signal Cd(t), then the amplitude fluctuation component (hereinafter also referred to as "amplitude component") Env(t) is Env(t) = [
1+niri+2 cos(f(t)-f(t-T)+(
1)T)]″・(8), and the phase component φ([) is
-π/2 to π/2.

Next, the output C+ of the comb filter 9 expressed by the above formula
(f) is supplied to the multiplier 5 and despread, P”(t)
= 1, so the output C2(t) of multiplier 5 is C2(j)=
P'(j)E nV'(i)[CO3(ωt+f(
t)+φ t ) ) ]”= 4 E nv'(t)
(1+ cos2 (ωt+f(t)+φ t)
)]1G) As is clear from equation (10), the carrier wave frequency, modulation index m1 (af/Vm), and phase fluctuation are doubled, but the basic properties of FM remain unchanged. Therefore, unnecessary components other than the FM signal are removed by passing the signal through a narrow band r wave filter <BPF) 14 with a center frequency of 2ω, and the signal is demodulated by an FM demodulation circuit 48 at the next stage. Comb filter 9
The amplitude component Env' in the FM signal generated by despreading at
(t) is removed by the limiter built in the FM demodulation circuit 48, so the FM demodulation output e (t) becomes E
, nv'(t) is obtained by differentiating the components except for nv'(t).
As a form in which the distortion component old sB) is added to (t), the following formula %
It can be expressed by the formula % (12). That is, the distortion component Dis(t) is Dis(
t)=(f'(t)-f'(t-T)).

Based on the above calculation results, when we examine the characteristics of distortion components from the FM demodulated output, we find the following.

(2) The distortion component becomes distortion added to f'(t) when K<1, and becomes distortion added to f'(t-T) when K>1, and increases as K=1 approaches.

(2) The distortion component is proportional to the modulation signal f([). That is, f([
) is the modulation frequency fm and modulation index m8df/fm
) represents. As a result, if the modulation frequency fm is high, the distortion component is large, and if m f X f m is large, the distortion becomes complicated.

(2) The distortion component is proportional to the difference between f'(t) and f'(t-T), and approximately proportional to the delay time T.

Here, K=1. That is, when the amplitude ratio A I # A 2 of the FM signal c (B and the FM delay signal Cd (t) is equal, Dis (t) - (f' (t) - f' (t - T
)) 2 <f'←t)-f'(t-T))...
(14), and the distortion component disappears. This is the difference component between the undistorted demodulated output f'(t) and the undistorted delayed demodulated output f'(t-T), and its level is approximately -29 d when the modulation frequency fm = 3.4 KHz in Figure 5.
However, since this value is smaller than the maximum value Ode, it can be ignored, and as a result, e (t) 'v 2 f
'(j), and there is no distortion. (However, this is based on calculations; in reality, there will be a slight level difference, so the distortion will be almost at its maximum.) In this way, the SS conversion FM (comb filter transmission of No. 8 is basically FM Conventionally, it has been generally thought that it cannot be used in the demodulation section of SS communications because it causes the same type of multipath distortion that occurs during broadcast reception, and I have never seen an example of its use.Therefore, in the method of the present invention, By setting some conditions as shown below, the system is established while avoiding the above drawbacks.

(2) Due to the nature of distortion components, the delay time T with respect to the modulation signal f([) is made as small as possible as a condition for suppressing the distortion components.

(2) Make the main power spectrum of the FM signal exist within the passband of the comb filter. That is, the modulation index ml is small,
If the modulation frequency fm is sufficiently low compared to the frequency +1/T due to the delay time T of the delay circuit, as is clear from Fig. 5, the +f'(t)-f'(t-T)l component is becomes very small.

(2) If the spectral interval d of the SS wave (see FIG. 3 (8)) is set to 200 Hz, the delay time T will be 5 μs.

When the highest modulation frequency fmllaX is 364 Hz,
As can be seen from Figure 5 (A), the effect of strain is
When it is set to e, the value is approximately -29 dB. (transfer function W(S
), it is maximum at the anti-phase (180° phase shift) frequency and becomes O at the in-phase frequency. ) ■In the example in Figure 5 (^), the delay time T is twice 10
If it becomes μs, the maximum value will be 50, 112, and 3
．． At the 4KH2 location, the distortion is approximately -23 dB.

Finally, another example of the configuration of the comb filter (9) will be explained with reference to FIGS. 10 and 11.

The circuit shown in FIG. 10 has two stages of recursive filters connected in cascade, and components that perform the same function in each stage are given the same numbers. 20 is a delay circuit that provides a delay time 3T that is three times that of the delay circuit 19; 21 and 2;
2 is a coefficient adder that multiplies Kl by a coefficient of 2 (0≦K I # K 2≦1), and 23 to 25 are adders. As a specific example of the delay time T set in the delay circuit 19, the pass characteristics when T=4 μs are shown in FIG. 11. In this case, −60 dB is the noise level. In this figure, "linear" refers to a characteristic curve when the vertical axis is expressed not on a logarithmic scale [dB] but on an equally spaced scale. As is clear from this characteristic diagram, when the coefficient values K l p K 2 of the coefficient adders 21 and 22 constituting the comb filter are changed, the pass characteristics of the comb filter change slightly, but in any case, This results in a steep narrowband P-wave characteristic having a center frequency at l/T (=250 Hz) (and integral multiples thereof). The transfer function H(ω) of this filter is expressed by the following equation.

t((ω) = ((1+cosω ■Meeting
K, c OS3ω ■ )1+ (2 to sinωT+
sin3ωT )' ) /((t-, c, osωT
-, cos3ω■)7mo (K, sinωT+, ni,5in3ωT)')-(15) As a familiar concrete application example of the SS wireless communication device of the present invention having the above configuration, Examples include wireless devices that use weak radio waves, such as wireless microphones, transceivers, and mobile wireless telephones (cordless telephones).

〔effect〕

Since the spread spectrum wireless communication device of the present invention is configured as described above, it has the following excellent features.

(1) In the conventional device, the demodulation section also includes a spreading code generation circuit for despreading, and a clock recovery circuit.

The circuit configuration was extremely complicated because a spreading code generation circuit, synchronization pull-in circuit, synchronization holding circuit, etc. were essential, but since these are no longer necessary, the circuit configuration can be considerably simplified and the cost can be significantly reduced. This has made it extremely easy to apply it to consumer devices.

■ By eliminating the need for multiple circuits that require advanced technology, such as a synchronization pull-in circuit and a synchronization holding circuit, it is freed from the disadvantages of conventional devices such as the long synchronization pull-in time and problems such as loss of synchronization. It can contribute to stabilizing the operation of spread spectrum wireless communication equipment.

■By setting the frequency spectrum interval of the spread spectrum signal to be at least wider than the frequency bandwidth of the FM modulation signal, it is possible to transmit the SS-modulated FM signal over a com-filter, and unnecessary components other than the SS signal can be sufficiently suppressed. 2
Since despreading by multiplication is possible, demodulation (receiving section)
The side configuration can be greatly simplified.

(4) Does the FM change compared to the reciprocal of the delay time of the delay circuit that makes up the comb filter? By setting the modulation frequency of the A signal sufficiently low and setting its modulation index small,
It is possible to suppress the generated distortion to a sufficiently low level for practical use, to perform stable instantaneous operation, and to realize reliable demodulation operation.

■Since we adopted a novel configuration for the carrier sense to make MCA work, we were able to combine a full-fledged SS communication method and an MCA method to provide a simple wireless communication device that does not have many near-far problems.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram of an embodiment of the spread spectrum wireless communication device of the present invention, FIG. 2 is a principle diagram showing communication using two devices of the present invention, and FIG. 3 and 10 are specific block diagrams of the comb filter that constitutes the demodulation section of the device of the present invention, and FIGS. 4(A), (B), and 11 are the comb filters shown in FIGS. 3 and 10, respectively. Passage characteristics diagram, 5th
The figure is a distortion-frequency characteristic diagram of the comb filter shown in figure 3, and figure 6.
Figures (A) to (0) and Figures 7 (^) and (B) are frequency spectrum diagrams for explaining the operation of the device of the present invention, and Figure 8 is a block diagram showing the basic principle of a conventional spread spectrum wireless communication device. FIG. 9 is a spectral waveform diagram for explaining the operation of each component of the apparatus shown in FIG. 8. 1... Spread spectrum wireless communication device, 2-6... Multiplier, 9... Comb filter, 11-14... BPF
, 17.18...Amplifier, 19.20...Delay circuit, 21.22...Coefficient adder, 23-25...Adder, 31...DUP, 32...Detection circuit, 33...
・CPU, 34... Frequency synthesizer, 37...
LPF, 42...FM modulation circuit, 44...Spreading code generation circuit, 48...FM demodulation circuit, A...Antenna, M...Microphone, S...Speaker, In+,
In2...Input terminal, Prefecture1...Output terminal.

Claims (3)

[Claims] (1) The transmitter side includes an FM modulator that modulates a modulated signal such as voice with a carrier wave and outputs an FM modulated signal;
A spectrum spreading means that spread-modulates a modulated signal with a spreading code from a spreading code generation circuit and outputs a spread spectrum signal, and a frequency converter having a multi-channel access function that up-converts and outputs the spread spectrum signal. The receiver side includes a frequency converter having a multi-channel access function that down-converts the spread spectrum signal received from the antenna, and converts the frequency-converted spread spectrum signal into the spread spectrum signal. A detection means detects only the frequency spectrum of the frequency-converted spread spectrum signal by supplying the signal to a comb-shaped filter tuned to comprising a multiplication means for spreading, a bandpass filtering means for passing only the despread output signal obtained by the multiplication means, and a demodulation means for FM demodulating the output signal of the bandpass filtering means; A carrier sense function that checks and processes whether a spread spectrum frequency band is occupied, and a multichannel access operation that changes the frequency band used for transmission and reception if the frequency band is occupied. What is claimed is: 1. A spread spectrum wireless communication device characterized in that the device is configured to communicate by providing a control section that also has an access function. (2) As a means for generating the carrier sense function in the control section, the output of the comb filter before the start of the communication operation is multiplied by the spreading code from the spreading code generation circuit to convert it into a narrowband noise signal, and the signal is converted into a narrowband noise signal. The spread spectrum wireless communication device according to claim 1, wherein the spread spectrum wireless communication device is configured to perform the level determination. (3) The spread spectrum radio according to claim 1, wherein the means for generating the carrier sense function in the control section is determined by determining the demodulation noise level generated in the FM demodulation output before the start of the communication operation. Communication device.