JPH06232839A - Spread spectrum receiver - Google Patents

Abstract

PURPOSE:To provide a spread spectrum(SS) receiver which is simply constituted and can provide signals with satisfactory C/N. CONSTITUTION:The output of a BPF 22 is impressed to a circuit composed of rectifiers 26 and 27 and bias resistors 28 and 29 for the rectifiers, a positive half wave f1 and a negative half wave f2 are provided, second modulated waves at frequencies 2f1 and 2f2 are provided by synthesizing those half waves at a differential amplifier 30, and those second modulated waves are impressed to a cyclic filter composed of adder circuits 31 and 32, delay lines 33 and 34 and gain control circuits 35 and 36. Those outputs pass respectively through gain control circuits 37 and 38 and limiters 39 and 40 and demodulated by FM demodulators 41 and 42, a difference is provided by a differential amplifier 43 and passes through a shaping circuit 44, and a data output signal 45 is provided. Loop transmission times tau1 and tau2 of respective cyclic filters are set to tau1=1/2f1 and tau2=1/2f2. Loop gains K1 and K2 are enlarged as much as possible although on the condition of K1<1 and K2<1 at the frequencies 2f1 and 2f2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum (hereinafter referred to as SS) receiver using a spread spectrum system.

[0002]

2. Description of the Related Art FIG. 4 shows an SS using FM modulation for the first modulation.
6 is a system diagram of a transmitter, FIG. 5 is an example of an SS receiver using a SAW convolver, and FIG. 6 is an explanatory diagram of a modulation system. In FIG. 4, the data input signal 1 has a binary (1,0) amplitude shown in the waveform diagram of FIG. Then, the data input signal 1 is added to the VOC (voltage controlled oscillator) 2 and
A time series of two frequencies f1 and f2 as shown in (b) is obtained.

PN code (pseudo noise code) generator 4
6 (b) by multiplying the PN code '0' of FIG. 6 (C ") by -1 in the multiplication circuit 3 by the PN signal (PN code: code string shown in FIG. 6 (C")) generated in FIG. The time series of the frequencies f1 and f2 shown in () is the waveform shown in FIG. 6 (c) (the waveform of FIG. 6 (c ') is a partially enlarged view thereof, and the PN code string of FIG. 6 (c'') is used. The polarity is reversed).

The component indicated by numeral 5 in FIG. 4 is a high frequency transmitter, and if the frequency of the local oscillator 5-1 is f0, a frequency converter (multiplier circuit 5-2 and BPF (bandpass filter) 5) is provided. -3) and radiate from the antenna as frequency (f0 + f1) or (f0 + f2).

In FIG. 5, a component indicated by numeral 6 is a high frequency receiving section, which has a frequency suitable for operating the SAW convolver 8 by amplifying the received high frequency and performing frequency conversion. The BPF 7 extracts the signal of the frequency f1 or f2 from the output from the high frequency receiving unit 5.

At the other end (input) of the SAW convolver 8,
Fixed oscillator 9 (frequency (f0 + f1) or (f0 + f
The carrier wave of 2)) is generated by the PN code generator 4 ′ to generate the same PN code as the PN code generator 4 of FIG.
A signal that has been polarity-modulated with and passed through the BPF 11 and the amplifier 12 is added. The SAW convolver 8 amplifies the correlation output between the output of the BPF 7 and the output of the amplifier 12 by the amplifier 13, and outputs the HPF.
(High-pass filter) 14, envelope detector 15, and comparison circuit 16, and then digitally demodulated by digital demodulator 17,
Output data 19 is obtained via the LPF 18.

The SS receiver shown in FIG. 5 is basic, but is more complicated than the structure of the transmitter shown in FIG.
Since the SAW convolver is required as a key device (key device), there is a disadvantage that there is a certain limitation in miniaturizing the device. As a means for solving such inconvenience, there is an SS receiver (FIG. 7) disclosed in Japanese Patent Laid-Open No. 2-69051 (invention title "spread spectrum device").

In FIG. 7, the component indicated by reference numeral 6'is a high frequency receiver, which amplifies the received high frequency, converts it to a difference frequency f1 or f2 by the fixed oscillator 21 and the multiplication circuit 20, and outputs the output. BPF2 in addition to BPF22
The second output the multiplication circuit 23 squared signal cos .omega ₁ t from the signal c
Convert to os2ω ₁ t.

[0009] Figure 8 is an explanatory diagram of a frequency multiplier according to the multiplication circuit 23 in FIG. 7, the signal cos2ω ₁ t is generated from the multiplier circuit 23 the signal cos .omega ₁ t, PN shown in Figure 8 (a)
In the signal, the polarities are inverted at t = t1, t2, t3, but when the polarities are the same as shown in FIG. 8B, the frequency doubles. Next, in the BPF 24, the frequency 2f1 of S2,
2f2 is taken out, and it is shown in FIG.
The data signal is restored as shown in (c). As described above, the SS receiver disclosed in Japanese Patent Laid-Open No. 2-69051 can realize the demodulation of the data signal with a simple configuration.

[0010]

However, the SS receiver disclosed in Japanese Patent Laid-Open No. 2-69051 has a problem that the S / N of the demodulation input cannot be sufficiently obtained although the SS receiver has a simple structure.

An object of the present invention is to provide an SS receiver having a simple structure and capable of obtaining a signal with good S / N.

[0012]

In order to achieve the above object, a spread spectrum receiver according to a first aspect of the present invention receives a transmission signal including a data signal from a spread spectrum transmission means and receives a difference component of the signal. A difference component signal extracting means for obtaining a signal, a frequency component signal extracting means for obtaining a time series signal containing component signals of different frequencies from the difference component signal, and a positive / negative component signal extracting means for obtaining a positive / negative component signal from the time series signal,
From the signal component extraction means for extracting the difference component signal of the positive and negative component signals, the difference component signal of the positive and negative component signals, and the result of gain control by delaying the difference component signal by the transmission delay time related to the different frequency. A recursive filter means for obtaining a combined signal; an amplitude control means for controlling the amplitude of the combined signal;
Demodulation means for demodulating the amplitude-controlled composite signal to obtain a data signal.

In a second aspect of the present invention, in the spread spectrum receiver according to the first aspect of the present invention, the cyclic filter means delays the difference component signal received signal of the positive and negative polarity component signals and the difference component signal for a predetermined time and controls the gain. A synthesizing means for adding a signal to obtain a synthesized signal, and a difference component signal having a frequency 2f1,
It is characterized by comprising delay means for delaying the transmission time of the loop based on 2f2, and gain control means for controlling the gain k to be k <1 to obtain a gain control signal.

[0014]

With the above construction, the spread spectrum receiver according to the first invention receives the transmission signal containing the data signal from the spread spectrum transmission means by the difference component signal extraction means and obtains the difference component signal of the signal. A time-series signal containing component signals of different frequencies is obtained from the difference component signal by the frequency component signal extraction means. Then, the positive and negative component signal extracting means obtains the positive and negative component signals from the time series signals, the signal component extracting means extracts the difference component signal of the positive and negative component signals, and the cyclic filter means extracts the difference component signal of the positive and negative component signals. And a result of gain control by delaying the difference component signal by a transmission delay time related to the different frequency, and performing amplitude adjustment control of the combined signal by the amplitude control means,
A data signal is obtained by demodulating the combined signal whose amplitude is controlled by the demodulation means.

According to a second aspect of the present invention, in the spread spectrum receiver according to the first aspect of the invention, the recursive filter means receives the difference component signal reception signal of the positive and negative component signals by the combining means.
The difference component signal is delayed by a predetermined time and added to the gain-controlled signal to obtain a composite signal, and the delay component delays the difference component signal by the transmission time of the loop based on the frequencies 2f1 and 2f2 of the signal to control the gain. The gain k is controlled by the means so that the gain k becomes k <1.

[0016]

1 is a block diagram showing the configuration of an embodiment of an SS receiver according to the present invention, and FIG. 2 is a block diagram showing the configuration of another embodiment of an SS receiver according to the present invention. 3 is a waveform diagram of an output signal from each component of the SS receiver of FIG.

<Embodiment 1> In FIG. 1, reference numeral 6'denotes a high-frequency receiving section, the construction and operation of which are shown in FIG.
It is the same as the high-frequency receiving unit 6'of the SS receiver disclosed in No. -69051 (and so is 20 to 22). Further, in FIG. 1, 26 and 27 are rectifying elements, and 28 and 2
9 is a rectifying element bias applying resistor, 30 is a differential amplifier circuit,
31 and 32 are adder circuits, 33 and 34 are delay circuits, and 35 to 35.
38 is a gain control circuit, 39 and 40 are limiters which correspond to amplitude control means, 41 and 42 are FM demodulators, 43 is a differential amplifier which corresponds to signal component extraction means, 44 is a shaping circuit and 45 is It is an output signal (data). In addition, BPF
Reference numeral 22 corresponds to a frequency component signal extracting means, which is a multiplication circuit 20.
The fixed oscillator 21 constitutes a difference component signal extracting means, and includes a rectifying element 26, a rectifying element bias applying resistor, and a rectifying element 27.
The rectifying element bias applying resistor 29 constitutes a positive / negative component signal extracting means, and the adder circuit 31, the delay circuit 33, the gain control circuit 35, the adder circuit 32, the delay circuit 34, and the gain control circuit 36 are cyclic filters. Configure and
FM demodulators 41 and 42, differential amplifier 43, and shaping circuit 4
Reference numeral 4 constitutes demodulation means.

In FIG. 1, the received high frequency is amplified, converted to the difference frequency f1 or f2 by the fixed oscillator 21 and the multiplication circuit 20, and output as the output of the BPF 22 at the frequencies f1 and f2 as shown in FIG. 3A. Obtain a sequence signal. In FIG. 3 (a), t
= T1, t3, ... Are times at which the polarity is inverted by the PN code, and at t = t2, the frequency changes from f1 to f2 depending on the data (see FIG. 6B).

When the output of the BPF 22 is applied to the circuit composed of the rectifying elements 26 and 27 and the bias applying resistors 28 and 29 of the rectifying elements, a positive half wave is generated in the rectifying element 26.
Since negative half-waves are obtained, they are combined by the differential amplifier 30 to obtain a signal (rectified signal) having a waveform as shown in FIG. The fundamental wave of FIG. 3 (b) becomes a second modulated wave of frequencies 2f1 and 2f2 as shown in FIG. 3 (d).

The output of the differential amplifier 30 is applied to a cyclic filter composed of an adder circuit 31, a delay line 33 and a gain control circuit 35 and a cyclic filter composed of an adder circuit 32, a delay line 34 and a gain control circuit 36. Here, the transmission time τ1 of the loop of the adder circuit 31, the delay line 33, and the gain control circuit 35.
Is set to τ1 = 1 / 2f1, and the adder circuit 32 and the delay line 3 are set.
4 and the loop transfer time τ2 of the gain control circuit 36 is τ2
= 1 / 2f2. Note that the gain K of the recursive filter is
1 and K2 have frequencies 2f1 and 2f2 and K1 <1 and K2 <1.
However, it is desirable to make it as large as possible (close to 1) to have an integration effect, and to select the attenuation rate K ⁿ due to the loop (loop) to be about 0.5 in data length.

The outputs of the adder circuits 31 and 32 are passed through gain control circuits 37 and 38 and limiters 39 and 40, respectively, and FM.
The demodulators 41 and 42 demodulate, the differential amplifier 43 takes a difference to obtain a difference component signal, and the shaping circuit 44 shapes the waveform to obtain a data output signal 45.

FIG. 3 (e) shows the output waveform of the differential amplifier 30 described above, which is a time-series signal having frequencies 2f1 and 2f2 when the modulating wave is omitted. Further, FIG. 3F shows the output waveform of the adder circuit 31, and the component of the frequency 2f1 is large and the component of the frequency 2f2 is small by the cyclic filter. further,
FIG. 3 (g) shows the output waveform of the adder circuit 32, and the component of frequency 2f1 is small and the component of frequency 2f2 is large due to the cyclic filter.

In this embodiment, there are two systems of the adder circuit 31 to FM demodulator 41 and the adder circuit 32 to FM demodulator 42 in FIG. 1. In FM modulation, the output signals of the gain control circuits 37 and 38 are limiters 39 and 40, respectively. Although the amplitude is made constant and added to the FM demodulators 41 and 42, they may be configured by one system. It should be noted that the S / N ratio of the differential amplifier is improved by using two systems as in this embodiment.

<Embodiment 2> FIG. 7 shows an example in which an envelope detector is used for demodulating the output signals (frequency 2f1, 2f2) from the cyclic filter of FIG. 1, 46 and 47 are envelope detectors, and 48 is differential. An amplifier, 49 is an LPF (low-pass filter), 50 is a shaping circuit, 51 and 52 are buffer amplifiers, 53 is a trap f1, and 54 is a trap f2.

The buffer amplifier 51 and the trap 5
3, the buffer amplifier 52 and the trap 54 respectively constitute amplitude control means, and the envelope detectors 46 and 47,
The differential amplifier 48, the LPF 49 and the shaping circuit 50 constitute demodulation means.

In FIG. 7, the output of the cyclic filter composed of the adder circuit 31, the delay line 33 and the gain control circuit 35 is passed through the buffer amplifier 51 and the trap 53 (2f2 series resonance circuit or 2f1 parallel resonance circuit) to the envelope detector 46. Add to. On the other hand, the output of the cyclic filter including the adder circuit 32, the delay line 34, and the gain control circuit 36 is applied to the envelope detector 47 through the buffer amplifier 52 and the trap 54 (2f1 series resonance circuit or 2f2 parallel resonance circuit).

Since the outputs of the envelope detectors 46 and 47 are the envelopes of FIGS. 3F and 3G, the difference is taken by the differential amplifier 48 and the output waveform signal (difference component signal) of FIG. 3H is obtained. obtain. Then, the LPF 49 further suppresses the noise component (here, the LPF 49 allows the fundamental wave shown in FIG. 6A to pass as it is).

The output of the LPF 49 becomes the output waveform signal shown in FIG. 3 (i).
The output of the waveform (rectangular signal) of (j) is obtained. Further, in FIG. 7, the reason why the recursive filter and thereafter are two systems is to improve the S / N as in the case of the first embodiment.

[0029]

As described above, according to the spread spectrum receiver of the present invention, since the cyclic filter is used in the spread spectrum receiver when the first spread spectrum modulated signal is frequency modulated, a simple structure is obtained. The original signal with S /
N can be demodulated well.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a spread spectrum receiver according to the present invention.

FIG. 2 is a block diagram showing the configuration of another embodiment of the spread spectrum receiver according to the present invention.

FIG. 3 is a waveform diagram of an output signal from each component of the spread spectrum receiver of FIG.

FIG. 4 is a system diagram of a spread spectrum receiver using FM modulation for the first modulation.

FIG. 5 is an example of a spread spectrum receiver using a SAW convolver.

FIG. 6 is a schematic explanatory diagram of a modulation method.

FIG. 7 is an example of a conventional spread spectrum receiver.

8 is an explanatory diagram of frequency multiplication by the multiplication circuit of FIG.

[Explanation of symbols]

20 Multiplier Circuit 21 Fixed Oscillator 22 BPF 22 (Frequency Component Signal Extracting Means) 26, 27 Rectifying Element (Positive / Negative Component Signal Extracting Means) 28, 29 Rectifying Element Biasing Resistance (Positive / Negative Component Signal Extracting Means) 30 Differential Amplifying Circuit (Signal Component) Extraction means) 31,32 Adder circuit (recursive filter means) 33,34 Delay circuit (recursive filter means) 35,36 Gain control circuit (recursive filter means) 39,40 Limiter (amplitude control means) 41,42 FM Demodulator (demodulation means) 43 Differential amplifier circuit (demodulation means) 44 Shaping circuit (demodulation means)

Claims (2)

[Claims] 1. A difference component signal extracting means for receiving a transmission signal containing a data signal from a spread spectrum transmission means to obtain a difference component signal of the signal, and a component signal having a different frequency from the difference component signal. A frequency component signal extracting means for obtaining a sequence signal, a positive / negative component signal extracting means for obtaining a positive / negative component signal from the time series signal, a signal component extracting means for extracting a difference component signal of the positive / negative component signals, the positive / negative electrodes A difference component signal of the component signals, a cyclic filter means for obtaining a combined signal from the result of gain control by delaying the difference component signal by a transmission delay time related to the different frequency, and amplitude control for amplitude adjusting control of the combined signal A spread spectrum receiver comprising: a demodulation means for demodulating the amplitude-controlled combined signal to obtain a data signal. 2. The spread spectrum receiver according to claim 1, wherein the recursive filter means adds a difference component signal reception signal of the positive and negative component signals and a signal whose gain is controlled by delaying the difference component signal for a predetermined time. Combining means for obtaining a combined signal,
From delay means for delaying the difference component signal by the transmission time of the loop based on the frequencies 2f1 and 2f2 of the signal, and gain control means for controlling the gain k so that k <1 to obtain a gain control signal. A spread spectrum receiver characterized in that.