JP3118938B2 - Demodulator for spread spectrum communication - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a demodulator for spread spectrum communication which performs synchronous capture by a sliding correlation method.

[0002]

2. Description of the Related Art In recent years, demodulators for spread spectrum communication have been widely used in the field of personal communication and the like because of their excellent multiple access, confidentiality and interference resistance.

A conventional demodulator for spread spectrum communication will be described below with reference to the drawings.

As shown in FIG. 2, a conventional demodulator for spread spectrum communication receives an incoming pseudo noise signal 1 and outputs a VCO once every one information data period to a multiplier 2, an integrating circuit 3, a sliding correlator 4, and one information data period. Control unit A5 for controlling the
The VCO 6 includes a VCO 6, a pseudo noise signal generator 7, a synchronization tracking unit 8, an acquisition control unit 9, and a data demodulation unit 10.
1 is output.

[0005] A conventional spread spectrum communication demodulator comprising the above components will be described below in relation to each component and operation.

First, an input signal SI _i is input to a sliding correlator 4, multiplied by a pseudo noise signal SL _i output from a pseudo noise signal generator 7 by a multiplier 2, and then integrated by an integration circuit 3. . Data 1 when captured synchronously
The output S of the period integration circuit 3 is obtained by (Equation 1).

[0007]

(Equation 1)

Here, at each sampling point, AI, w _c
× t, θ = constant; for simplicity, AI = 1, w _c
If xt = θ = 0, the output S is (Equation 2).

[0009]

(Equation 2)

Next, since the polarity of S becomes the reproduced data as it is, the allowable limit value Δf _a of Δf when the frequency deviation between transmission and reception is corrected once in one information data period can be obtained from (Equation 3). .

[0011]

(Equation 3)

N is the number of diffusion chips, and N≫1.
Is well known, and taking that into account, from equation (3), Δf
When a is obtained, it is obtained as Δfa = π / T. Therefore, under the condition of Δf <π / T, the sliding correlation unit 4
When the correlation value is input to the data demodulation unit 10 from, the polarity of S is determined and the data 11 is reproduced. After the synchronous acquisition, the acquisition completion signal is sent from the acquisition control unit 9 to the synchronization tracking unit 8, and the synchronization tracking is performed while the period tracking unit 8 controls the pseudo noise signal generation unit 7. 4, the correlation value is input to the VCO control unit A5, the polarity of Δf is determined once in one information data period, and the VCO 6 is controlled so that Δf = 0 to correct the frequency deviation between transmission and reception.

[0013]

However, the above-mentioned conventional configuration has a problem that data cannot be reproduced if the frequency deviation between transmission and reception in one information data period becomes π / T or more.

The present invention solves the above-mentioned conventional problems, and the frequency deviation between transmission and reception in one information data period is π /
It is an object of the present invention to provide a spread spectrum communication demodulator capable of reproducing data if it is not less than T and not more than 2π / T.

[0015]

In order to achieve the above object, a demodulator for spread spectrum communication according to the present invention has a configuration for correcting a frequency deviation between transmission and reception twice in one information data period. I have.

[0016]

According to the present invention, even if the frequency deviation between the transmission and reception of one information data period is π / T or more, the present invention provides 2π / T.
In the following cases, data can be reproduced.

[0017]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 4 is a certain phase difference.
An incoming pseudo-noise signal input during one information data period
Performs a product-sum operation with the pseudo-noise signal on the receiving side and sequentially changes the phase
While performing the same operation and synchronizing with the multiplier 2 and integrating
This is a sliding correlation unit composed of the circuit 3. 9 is sla
Synchronous capture control based on output from idling correlator 4
Is a capturing control unit that performs the following. 7 is a sliding correlation unit 4
This is a pseudo-noise signal generation unit that sends a pseudo-noise signal to the CPU. 6 is
It is a VCO (voltage controlled oscillator) that supplies a clock.
Reference numeral 10 denotes a data based on the output from the sliding correlator 4.
It is a data demodulation unit that performs data demodulation. 5 and 6
One information data based on the output from the riding correlator 4
VCO control that performs VCO control with a half cycle shift
The control unit A and the VCO control unit B. 8 performs synchronous tracking
This is a synchronous tracking unit. Spread spectrum communication of the present embodiment
Demodulation device sends one information data cycle to VCO control unit A5.
VCO control unit B1 that controls VCO with half cycle difference
2 is newly provided.

The demodulator for spread spectrum communication composed of the above components will be described below with reference to FIG. First, the input signal SI _i is input to the sliding correlator 4, multiplied by the pseudo noise signal SL _i output from the pseudo noise signal generator 7 by the multiplier 2, and then integrated by the integration circuit 3. The output S of the integration circuit 3 for one cycle of data when synchronously captured is obtained by (Equation 1) as in the conventional example.

Here, at each sampling point, AI, w
_c × t, θ = constant; for simplicity, AI = 1, w _c
If xt = θ = 0, the output S becomes (Equation 2) as in the conventional example.

Next, since the polarity of S becomes the reproduced data as it is, the frequency deviation between the transmission and reception is corrected twice with a half cycle difference from one information data cycle , ie, two VCs.
O control unit to provide two VCO control units with 1/2 information data
When the operation is performed at the different cycle, the allowable frequency deviation Δf
fb is obtained from (Equation 4).

[0021]

(Equation 4)

N is the number of diffusion chips, and N≫1.
Is well known, and taking that into account (Formula 4), Δf
When b is obtained, it is obtained as Δfb = 2π / T. sand
That is, it is possible to have twice the allowable frequency deviation. Therefore, the correlation value is input from the sliding correlator 4 to the data demodulator 10 under the condition of Δf <2π / T, where the polarity of S is determined and the data 11 is reproduced. After the synchronization is captured, a capture completion signal is sent from the capture control unit 9 to the synchronization tracking unit 8, and the synchronization tracking unit 8 performs synchronization tracking while controlling the pseudo noise signal generation unit 7, and at the same time, performs a sliding correlation unit. 4, the correlation value is input to the VCO control unit A5 and the VCO control unit B12.
Times Δf, the VCO 6 determines that Δf = 0.
To correct the frequency deviation between transmission and reception.

[0023]

As is clear from the above embodiments, according to the present invention, a frequency between transmission and reception twice as large as that of the prior art can be tolerated. It is.

[Brief description of the drawings]

FIG. 1 is a block diagram of a demodulator for spread spectrum communication according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional demodulator for spread spectrum communication.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Incoming pseudo noise signal 2 Multiplier 3 Integrating circuit 4 Sliding correlation part 5 VCO control part A 6 VCO 7 Pseudo noise signal generation part 8 Synchronization tracking part 9 Capture control part 10 Data demodulation part 12 VCO control part B

Claims (1)

(57) [Claims] 1. A sum-of-products operation of an incoming pseudo-noise signal and a receiving-side pseudo-noise signal input during one information data period with a certain phase difference, and the same operation is performed while sequentially changing the phase to perform synchronization compensation. A sliding correlator comprising a multiplier for capturing and an integrating circuit; a capture controller for controlling synchronous capture based on an output from the sliding correlator; and a pseudo noise for transmitting a pseudo noise signal to the sliding correlator. A signal generator, and a source clock required for generating a pseudo-noise signal.
A voltage controlled oscillator to be supplied to the signal generator , a data demodulator for demodulating data based on an output from the sliding correlator, and a half of one information data period based on an output from the sliding correlator. V that controls the voltage-controlled oscillator with a period shift
CO control unit A and VCO control unit B, and the capture control unit
When the capture complete signal comes from the
Compares the phase of the pseudo-noise signal in the
If the phase of the imaging signal is advanced, the pseudo noise
Outputs an instruction signal to delay the output phase of the signal generator
If the phase of the timing signal of the receiver is delayed,
Is an instruction for advancing the output phase of the pseudo-noise signal generator.
A synchronization tracking unit for outputting a signal , wherein the VCO control unit A and the VCO
CO control unit B compensates for frequency deviation between transmission and reception by half cycle difference
A demodulator for spread spectrum communication that performs positive .