JPH1141201A - Carrier wave reproducing circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier wave reproducing circuit which can output noise reduced reproducing carrier wave signals and can reduce power consumption. SOLUTION: In this carrier wave reproducing circuit, this an orthogonality detector 1 detects the orthogonality of a received signal while using the reproducing carrier wave inputted from a VCO 5, a correlative peak value arithmetic part 21 inversely diffuses the orthogonality detected signal and holds a peak value per symbol time as the correlative value of the result, a VCO control signal arithmetic part 22 outputs a VCO control signal corresponding to an error between the signal of a carrier wave on the side of transmission and the phase of the reproducing carrier wave through a loop filter 4 to a VCO 5 and according to the VCO control signal, the VCO 5 controls the phase of the reproducing carrier wave.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier recovery circuit used in a demodulation circuit of spread spectrum communication (Spread Spectrum), and more particularly to a carrier wave capable of recovering a carrier wave with low noise and reducing power consumption. It relates to a reproduction circuit.

[0002]

2. Description of the Related Art In spread spectrum communication, it is necessary to generate a signal (reproduced carrier signal) synchronized with a carrier signal used by a transmitting side on a receiving side. Here, a method shown in FIG. 5 is known as a carrier recovery circuit for recovering a carrier. FIG. 5 is a configuration block diagram illustrating an example of a conventional carrier recovery circuit.

As shown in FIG. 5, a conventional carrier recovery circuit includes a quadrature detector 1 and a matched filter.
er) 2, a multiplier 3, a loop filter 4, a VCO
(Voltage Control Oscillator) 5. The carrier recovery circuit shown in FIG. 5 shows an example in which BPSK (Binary Phase Shift Keying) modulation is employed for both primary modulation and secondary modulation.

[0004] Each part will be described in detail below. The quadrature detector 1 converts an I-phase (in-phase) component of a quadrature baseband signal from a signal (reception spread spectrum signal) received using a reproduced carrier signal input from the VCO 5 described later,
It detects and outputs each component of the Q-phase (quadrature) component.

As shown in FIG. 6, the quadrature detector 1 comprises a distributor 11, a two multiplier 12, and a phase shifter 13 as shown in FIG.
And two low-pass filters (LPFs) 14 provided corresponding to the multipliers 12. FIG. 6 is a configuration block diagram illustrating an example of the quadrature detector 1.

[0006] Here, the distributor 11 branches the input signal into two and outputs it to the multipliers 12a and 12b. The multiplier 12a is provided with a phase shifter 1 described later.
3 is multiplied by a signal input from the distributor 11 and a signal of the reproduced carrier itself (reproduced carrier that is not phase-shifted) input from 3 and output to the low-pass filter 14a.

The multiplier 12b is provided with a phase shifter 13 to be described later.
Is multiplied by a signal obtained by shifting the phase of the reproduced carrier input from the phase shifter by 90 degrees and a signal input from the distributor 11 and output to the low-pass filter 14b.

[0008] The phase shifter 13 receives the input of the reproduced carrier from the outside and outputs it as it is to the multiplier 12a.
Is output to

The low-pass filter 14a removes high-frequency components of the signal input from the multiplier 12a and outputs the same as an I-phase component of the baseband signal to the outside. The low-pass filter 14b removes a high-frequency component of the signal input from the multiplier 12b and outputs the signal to the outside as a Q-phase component of the baseband signal.

The matched filters 2a and 2b receive the input of the I-phase component signal and the input of the Q-phase component, respectively, perform despreading operations to generate narrow band signals, and output the signals to the multiplier 3. It is. The multiplier 3 includes a matched filter 2a,
The multiplication is performed by multiplying each of the narrow-band signals received from 2b and output to the loop filter 4.

Here, the signal output from the multiplier 3 is VC
This is a voltage signal for controlling O, and is hereinafter referred to as a “VCO control signal”.

The loop filter 4 is a band-pass filter, which receives the input of the VCO control signal from the multiplier 3, removes unnecessary components, and outputs the signal to the VCO 5. V
The CO 5 receives a VCO control signal input from the loop filter 4, oscillates and outputs a signal having a phase represented by the VCO control signal, and outputs the signal to the quadrature detector 1 as a reproduced carrier.

In other words, the conventional carrier recovery circuit shown in FIG. 5 basically constitutes a Costas loop circuit, in which BPSK modulation, which is secondary modulation, is demodulated by the matched filter 2. It has become.

Regarding the operation of the Costas loop circuit, Pr
inciples of Communication Systems, Second Edition,
H. Taub, DL Schilling, McGraw-Hill, 1986 43
There is a detailed description on pages 6 to 437, so the description here is omitted.

[0015]

However, in the above-mentioned conventional carrier recovery circuit, the multiplier outputs the signal output from the matched filter even in a so-called uncorrelated portion in which the correlation value output from the matched filter does not output a correlation peak. Since the multiplication is performed and the VCO control signal is output, there is a problem that noise is mixed in the VCO control signal and noise is mixed in the reproduced carrier. In addition, there is a problem that power consumption increases because a portion that calculates a VCO control signal, such as a multiplier, always operates.

The present invention has been made in view of the above circumstances, and has as its object to provide a carrier recovery circuit capable of outputting a reproduced carrier signal with less noise and reducing power consumption.

[0017]

According to a first aspect of the present invention, there is provided a carrier recovery circuit which holds a peak value of a despread signal per symbol length of time in a carrier recovery circuit. Calculates the phase error between the carrier on the transmitting side and the recovered carrier based on the held peak value, adjusts the phase of the carrier to be reproduced according to the result of the calculation, and reproduces the phase of the carrier signal on the transmitting side. The feature is to match the phases of the carrier waves, so that noise is not mixed into the reproduced carrier wave, and the power consumption can be reduced.

According to a second aspect of the present invention, there is provided a carrier recovery circuit, comprising: a quadrature detection section; a correlation peak value calculation section; a VCO control signal calculation section; A quadrature detection unit that outputs a reproduced carrier wave, the quadrature detection unit performs quadrature detection of the received signal using a reproduced carrier wave signal input from the VCO, and outputs an I-phase component signal and a Q-phase component signal. The correlation peak value calculation unit despreads the quadrature-detected I-phase component signal and Q-phase component signal input from the quadrature detection unit, and outputs a 1-symbol-length signal. A correlation peak value calculation unit for detecting and holding and outputting a peak value of the correlation value as a result of the despreading per unit time, wherein the VCO control signal calculation unit includes the I-phase component and the Q-phase component 2 of corresponding to A VCO control signal calculation unit that outputs a VCO control signal that is substantially proportional to an error between the phase of the carrier on the transmitting side and the phase of the recovered carrier based on the peak value of the related value, and the loop filter includes the VCO control signal A loop filter for removing unnecessary components from
The CO is a VCO that receives a VCO control signal through the loop filter, adjusts the phase, and outputs a reproduced carrier signal. Power consumption can be reduced.

According to a third aspect of the present invention, there is provided a carrier recovery circuit according to the second aspect of the present invention, which receives a signal having undergone primary modulation and secondary modulation by BPSK. A carrier recovery circuit for recovering a carrier, wherein the correlation peak value calculator despreads the I-phase component signal and the Q-phase component signal input from the quadrature detector,
A matched filter that outputs the resulting correlation value,
A sample-and-hold circuit provided corresponding to the matched filter, for sampling a correlation value input from the corresponding matched filter for a time of one symbol length, and holding a peak value of the correlation value;
A multiplier for multiplying a peak value corresponding to the signal of the I-phase component and a peak value corresponding to the signal of the Q-phase component by the control signal calculation unit and outputting the VCO control signal as a VCO control signal , And noise is not mixed into the reproduced carrier, so that power consumption can be reduced.

According to a fourth aspect of the present invention, there is provided a carrier recovery circuit for receiving a signal which has undergone primary modulation by QPSK and secondary modulation by BPSK. Then, in the carrier recovery circuit for recovering the carrier, the correlation peak value calculation unit despreads the I-phase component signal and the Q-phase component signal input from the quadrature detection unit, and the result is obtained. A matched filter that outputs a correlation value, and is provided corresponding to the matched filter, and holds a peak value of the correlation value while sampling the correlation value input from the corresponding matched filter for a time of one symbol length. A sample-and-hold circuit, wherein the VCO control signal operation unit outputs “+1” if the sign of the peak value of the correlation value is positive, and outputs “−1” if the sign of the peak value is negative; Two limiters corresponding to each of the Q-phase components, a peak value of the correlation value of the Q-phase component output from the sample-and-hold circuit corresponding to the Q-phase component, and an output of the limiter corresponding to the I-phase component. A first multiplier for multiplying a signal to be output by the sampler and hold circuit, a peak value of a correlation value of the I-phase component output by the sample-and-hold circuit corresponding to the I-phase component, and a signal output by the limiter corresponding to the Q-phase component. The second to multiply
And a subtractor for subtracting a signal output from the second multiplier from a signal output from the first multiplier and outputting the subtracted signal as a VCO control signal. Noise is not mixed into the carrier, and power consumption can be reduced.

According to a fifth aspect of the present invention, there is provided a carrier recovery circuit according to the second aspect of the present invention, wherein a signal subjected to primary modulation and secondary modulation by QPSK is received. A carrier recovery circuit for recovering a carrier, wherein a correlation peak value calculation unit corresponds to an I-phase component signal input from a quadrature detection unit, and sets a first correlation value as a tap coefficient using an I-phase spreading code as a tap coefficient. A first matched filter to be output and a second matched filter corresponding to the I-phase component signal and outputting a second correlation value using a Q-phase spreading code as a tap coefficient and a Q-phase component signal Then, a third matched filter that outputs a third correlation value using the I-phase spreading code as a tap coefficient, and a fourth correlation filter that corresponds to the Q-phase component signal and uses the Q-phase spreading code as a tap coefficient. The fourth matched field that outputs the value A first correlation value calculating subtractor for subtracting the fourth correlation value from the first correlation value; and a second correlation for subtracting the second correlation value from the third correlation value. A signal input from the corresponding correlation value calculation subtractor, corresponding to the first correlation value calculation subtractor and the second correlation value calculation subtractor. Two sample-and-hold circuits that perform sampling for a long time and output while holding the peak value of the signal, and the VCO control signal calculation unit performs “+1” if the sign of the peak value of the correlation value is positive. And two limiters corresponding to each of the I-phase component and the Q-phase component, which outputs “−1” if negative, and the Q-phase component output from the sample-hold circuit corresponding to the Q-phase component. A peak value of the correlation value and a signal output by the limiter corresponding to the I-phase component Multiplying the peak value of the correlation value of the I-phase component output from the sample-and-hold circuit corresponding to the I-phase component by the signal output from the limiter corresponding to the Q-phase component Second
And a subtractor for subtracting a signal output from the second multiplier from a signal output from the first multiplier and outputting the subtracted signal as a VCO control signal. Noise is not mixed into the carrier, and power consumption can be reduced.

[0022]

Embodiments of the present invention will be described with reference to the drawings. The carrier recovery circuit (this circuit) according to the embodiment of the present invention is provided with a sample and hold circuit that holds a peak value of a correlation value as a result of despreading,
In addition to holding the peak value of the correlation value and reproducing the carrier based on the peak value, the so-called uncorrelated signal does not affect the reproduced carrier and the VCO
It is sufficient to operate the control signal only once after the peak value is held after the control signal is output, and it is not necessary to always operate it.Therefore, it is possible to reproduce a stable reproduced carrier while reducing power consumption. Output.

As shown in FIG. 1, the present circuit is basically composed of a quadrature detector 1, a correlation peak value calculator 21, a VCO control signal calculator 22, a loop filter 4, and a VCO 5. I have. FIG. 1 is a configuration block diagram of the present circuit.

Hereinafter, each part will be described in detail. However, since the quadrature detector 1, the loop filter 4, and the VCO 5 are the same as the conventional one, the description is omitted.

The correlation peak value calculation section 21 is provided with the quadrature detector 1
Is calculated as a result of despreading the signal input from the, and the peak value of the correlation value is calculated as the time Ts of one symbol length.
And holds the peak value and outputs the peak value to the VCO control signal calculation unit 22.

The VCO control signal calculation section 22 is based on the peak value output from the correlation peak value calculation section 21 and generates a VCO control signal which is substantially proportional to the phase error Δθ between the carrier signal on the transmitting side and the reproduced carrier signal reproduced on the receiving side. The control signal is calculated and output.

In other words, the present circuit samples the peak value of the correlation value, which is the result of despreading the signal orthogonally detected by the quadrature detector 1 by the correlation peak value calculation unit 21 over one symbol time, and obtains the peak value. The VCO control signal calculation unit 22 calculates the VCO control signal based on the peak value, outputs the VCO control signal to the VCO 5 via the loop filter 4,
The CO5 matches the phase of the reproduced carrier signal on the transmitting side with the phase of the reproduced carrier signal reproduced on the receiving side.

Further, the present circuit has a first case where both the primary modulation and the secondary modulation are BPSK modulation, a case where the primary modulation is QPSK (Quadrature Phase Shift Keying) modulation, and a case where the secondary modulation is BPSK modulation. The second case, and the third case where both the primary modulation and the secondary modulation are both QPSK modulations.
Since the circuit corresponding to the above case is conceivable, the present circuit corresponding to each case will be described in detail below.

First, this circuit (first circuit) corresponding to the first case in which both the primary modulation and the secondary modulation are both BPSK modulations
As shown in FIG. 2, the present circuit includes a quadrature detector 1, two matched filters 2 corresponding to the I-phase component and the Q-phase component output from the quadrature detector 1, and a matched filter 2 Sample and hold circuits 6 provided corresponding to
, A multiplier 3 ′, a loop filter 4, and a VCO 5. FIG. 2 is a configuration block diagram illustrating an example of the first main circuit.

That is, in the first main circuit, the correlation peak value calculator 21 is realized by the matched filter 2 and the sample hold circuit 6, and the VCO control signal calculator 22 is realized by the multiplier 3 '. It has become.

In the following description, the phase error between a carrier signal on the transmitting side and a reproduced carrier signal on the receiving side is Δθ, and both primary modulation and secondary modulation are BP.
The received spread signal R (t) in the first case of SK modulation is
The modulated signal is represented by A, the spreading code is represented by C, and the angular frequency of the carrier signal on the transmitting side is represented by ωc, which is generally represented by the following [Equation 1].

[0032]

(Equation 1)

Hereinafter, each component will be described in detail. The quadrature detector 1, the matched filter 2, and the loop filter 4
And the VCO 5 are substantially the same as those of the related art, and thus the description thereof is omitted.

The sample-and-hold circuits 6a and 6b sample the correlation values output from the corresponding matched filters 2a and 2b by one symbol length Ts, hold the peak value of the correlation value, and supply the sampled data to the multiplier 3 '. Output.

The multiplier 3 'includes a sample hold circuit 6
a and 6b multiply the respective peak values of the correlation values output and output to the loop filter 4. Also, since the multiplier 3 'only needs to multiply the peak values held by the sample hold circuits 6a and 6b, the multiplier 3' operates only once within the time of one symbol length Ts, for example. .

Next, the operation of the first main circuit will be described. The quadrature detector 1 performs quadrature detection on the received spread signal R (t) and outputs an I-phase component Iout (1) and a Q-phase component Qout (2) expressed by the following [Equation 2].

[0037]

(Equation 2)

Here, <> represents smoothing performed by the low-pass filter 14 of the quadrature detector 1.

Then, the matched filters 2a and 2b
Receiving the input of Iout and Qout of [Equation 2], respectively, performs despreading, and the corresponding sample and hold circuit 6
a and 6b. Then, the sample hold circuit 6
a and 6b respectively sample and hold the peak values of the correlation values input from the matched filters 2a and 2b, and output to the outside.

The peak values I and Q are equal to the inner product of Iout, Qout and the spreading code over one symbol length Ts as shown in the following [Equation 3].

[0041]

(Equation 3)

Here, since the reproduced carrier does not change during one symbol length Ts, the phase error Δθ between the carrier signal on the transmitting side and the reproduced carrier signal on the receiving side does not change during one symbol length Ts; Note that the spreading code has the following property of [Equation 4].

[0043]

(Equation 4)

Then, [Equation 3] can be transformed into the following [Equation 5]. As a result, the peak values of the correlation values output by the sample and hold circuits 6a and 6b are respectively shown by the following [Equation 5]. It looks like I, Q.

[0045]

(Equation 5)

Then, the multiplier 3 'multiplies I and Q of [Equation 5] to calculate a VCO control signal, and the loop filter 4 shapes the waveform of the VCO control signal. Is obtained.

[0047]

(Equation 6)

Here, if Δθ is sufficiently smaller than “1”, the fact that sin2Δθ can be approximated by Δθ is used. Therefore, the signal V output from the multiplier 3 ′ is Δ
It is almost proportional to θ.

As described above, since the VCO 5 is controlled by the voltage V substantially proportional to Δθ, Δθ gradually becomes “0”.
, So that the recovered carrier is in phase with the carrier on the transmitting side.

The main circuit (second main circuit) corresponding to the second case where the primary modulation is QPSK modulation and the secondary modulation is BPSK modulation is, as shown in FIG. Two matched filters 2 corresponding to the I-phase component and the Q-phase component output by the quadrature detector 1, two sample-and-hold circuits 6 provided corresponding to the matched filter 2, and a sample-and-hold circuit 6, two multipliers 3 "provided corresponding to the sample and hold circuit 6, a subtractor 8, a loop filter 4, and a VCO 5. FIG. 3 is an explanatory diagram illustrating an example of the second main circuit.

That is, in the second main circuit, the correlation peak value calculation section 21 is realized by the matched filter 2 and the sample hold circuit 6, and the VCO control signal calculation section 22 includes the limiter 7 and the multiplier 3 "And the subtractor 8.

Each component will be specifically described below. The quadrature detector 1, the matched filter 2, the sample and hold circuit 6, the loop filter 4, and the VCO 5 are the same as those of the first main circuit already described. Therefore, the description is omitted.

The limiter 7 outputs "1" if the peak value of the correlation value output by the corresponding sample hold circuit 6 is positive, and outputs "-1" if the peak value is negative. The multiplier 3 ″ is 1 in the same manner as the multiplier 3 ′ in the first main circuit.
It operates only once per symbol time Ts.

The first multiplier 3a ″ includes a signal output from the first limiter 7a corresponding to the I-phase component and a second sample-hold circuit 6b corresponding to the Q-phase component. The second multiplier 3 multiplies the output signal by
b ″ multiplies the signal output from the second limiter 7b corresponding to the Q-phase component by the signal output from the first sample-and-hold circuit 6a corresponding to the I-phase component.

The subtractor 8 subtracts the signal output from the second multiplier 3b "from the signal output from the first multiplier 3a" and outputs the signal to the loop filter 4. That is, in the second main circuit, the signal output from the subtractor 8 is the VCO control signal.

Next, the operation of the second main circuit will be described. In the following description, the phase error between the carrier signal on the transmitting side and the reproduced carrier signal on the receiving side is Δθ, the received spread signal R in the second case where the primary modulation is QPSK modulation and the secondary modulation is BPSK modulation. In (t), the I-phase modulated signal is A, the Q-phase modulated signal is B, the spreading code is C, and the angular frequency of the carrier, which is a transmitter local signal, is ωc. I will.

[0057]

(Equation 7)

The signal output from the quadrature detector 1 is
An I-phase component Iout (1) and a Q-phase component Qout (2) expressed by the following [Equation 8] are obtained.

[0059]

(Equation 8)

Here, <> represents smoothing performed by the low-pass filter 14 of the quadrature detector 1.

Then, matched filters 2a and 2b corresponding to the respective components despread Iout and Qout, respectively, output correlation values, and output sample-and-hold circuits 6a and 6a.
6b samples and holds the peak value of the correlation value output from the corresponding matched filter 2a, 2b over one symbol length Ts, and outputs it to the corresponding limiter 7a, 7b.

Here, the correlation peak I output from the sample-and-hold circuit 6a and the correlation peak Q output from the sample-and-hold circuit 6b are each the inner product of Iout or Qout over one symbol length Ts and the spreading code. Then, in the same manner as [Equation 3] and [Equation 4], each becomes as shown in the following [Equation 9].

[0063]

(Equation 9)

The limiters 7a and 7b take "1" if the peak values input from the corresponding sample hold circuits 6a and 6b are positive, and take "-1" if they are negative.
And Qlim are calculated. That is, the signals Ilim and Qlim respectively output from the limiters 7a and 7b are expressed by the following [Equation 1].
0].

[0065]

(Equation 10)

Here, sgn () is a function as shown in the following [Equation 11].

[0067]

[Equation 11]

Then, the first multiplier 3a ″ and the second multiplier 3b ″ perform the operations of Ilim Q and Qlim I, respectively, and the subtractor 8 outputs the output of the first multiplier 3a ″. I
Qlim I output from the second multiplier 3b ″ is subtracted from limQ, the waveform is shaped by the loop filter 4, and the VCO control signal V is calculated as in the following [Equation 12].

[0069]

(Equation 12)

Where sin (Δθ) is Δθ is π / 4
Under the condition that the phase error is sufficiently smaller than Δθ, the phase error Δθ gradually converges to “0” as in the first main circuit, and the VCO 5 reproduces in synchronization with the carrier signal on the transmission side. It outputs a carrier signal.

Also, both primary modulation and secondary modulation are QP
As shown in FIG. 4, the main circuit (third main circuit) corresponding to the third case of SK modulation includes a quadrature detector 1, a matched filter 2 ', and an adder 9 for calculating a correlation value. , A subtractor 10 for calculating a correlation value, and two sample-and-hold circuits 6
, Two limiters 7 provided corresponding to the sample and hold circuit 6, two multipliers 3 ″ provided corresponding to the sample and hold circuit 6, a subtractor 8, and a loop filter 4.
And VCO5. FIG. 4 is a configuration block diagram illustrating an example of the third main circuit.

That is, in the third circuit, the correlation peak value calculator 21 includes the matched filter 2 ′, the adder 9 for calculating the correlation value, the subtractor 10 for calculating the correlation value, and the sample and hold circuit 6. The VCO control signal operation unit 22 is realized by the limiter 7, the multiplier 3 ″, and the subtractor 8.

Hereinafter, each part will be described in detail. Since the quadrature detector 1, the sample and hold circuit 6, the loop filter 4, and the VCO 5 are the same as those of the second main circuit already described. The description is omitted.

The first matched filter 2 ′ a is set with the I-phase code Ci as a tap coefficient, and calculates the correlation value between the I-phase component signal output from the quadrature detector 1 and the I-phase code Ci. By performing the calculation, it is output as a despread signal. Hereinafter, the first matched filter 2'a
Is referred to as a “first correlation value”.

The second matched filter 2'b is set with the Q-phase code Cq as a tap coefficient, and calculates the correlation value between the I-phase component signal output from the quadrature detector 1 and the Q-phase code Cq. By performing the calculation, it is output as a despread signal. Hereinafter, the second matched filter 2'b
Is referred to as a “second correlation value”.

Similarly, the third matched filter 2 '
c and the fourth matched filter 2′d are respectively C
i and Cq are set as tap coefficients, and a correlation value between the Q-phase component signal output from the quadrature detector 1 and Ci or Cq is calculated and output as a despread signal. Hereinafter, the signal output from the third matched filter 2′c is referred to as “third correlation value”, and the signal output from the fourth matched filter 2′d is referred to as “fourth correlation value”. .

The adder 9 for calculating the correlation value adds the fourth correlation value to the first correlation value and outputs the result to the corresponding sample and hold circuit 6a as the I-phase correlation value. The subtractor 10 for calculating the correlation value subtracts the third correlation value from the second correlation value and outputs the result to the corresponding sample-and-hold circuit 6b as a Q-phase correlation value.

Next, the operation of the third circuit will be described. In the following description, the phase error between the carrier signal on the transmitting side and the reproduced carrier signal on the receiving side is Δθ, and the received spread signal R (t) in the third case where both the primary modulation and the secondary modulation are QPSK modulation. Is A for the I-phase modulated signal, B for the Q-phase modulated signal, Ci for the I-phase spread code, and Cq for the Q-phase spread code.
, The angular frequency of the carrier, which is the transmitter local signal, is
Is generally represented as the following [Equation 13].

[0079]

(Equation 13)

The signal output from the quadrature detector 1 is
The I-phase component Iout (1) expressed by the following [Equation 14] and Q
It becomes a phase component Qout (2).

[0081]

[Equation 14]

Here, <> represents smoothing performed by the low-pass filter 14 of the quadrature detector 1.

The first matched filter 2'a and the second matched filter 2'b corresponding to the I-phase component use the I-phase spreading code Ci and the Q-phase spreading code Cq to generate Iout. Is despread and a correlation value is output.

Further, the third matched filter 2'c and the fourth matched filter 2'd corresponding to the Q-phase component use the I-phase spreading code Ci and the Q-phase spreading code Cq, respectively. Qout is despread to output a correlation value.

Then, the adder 9 adds the second correlation value output from the fourth matched filter 2′d to the first correlation value output from the first matched filter 2′a.
The sample and hold circuit 6a corresponding to (1) samples and holds the peak value of the addition result over one symbol length Ts, and outputs the peak value to the corresponding limiter 7a.

Similarly, the subtracter 10 subtracts the second correlation value output from the second matched filter 2'b from the third correlation value output from the third matched filter 2'c,
The sample and hold circuit 6b corresponding to the subtractor 10 samples and holds the peak value of the result of the subtraction over one symbol length Ts, and outputs it to the corresponding limiter 7b.

Here, the sample and hold circuits 6a and 6b
Output the correlation peaks I and Q of one symbol length Ts
And the inner product of Iout or Qout over the spreading code and the spreading code, as shown in the following [Equation 15].

[0088]

(Equation 15)

Here, it is used that the I-phase and Q-phase spreading codes each have the property shown in the following [Equation 16], similar to [Equation 4].

[0090]

(Equation 16)

Then, the limiter 7 calculates Ilim and Qlim, which are "1" if the peak value input from the corresponding sample hold circuit 6 is positive, and "-1" if the peak value is negative. That is, the signals Ilim and Qlim output from the limiter 7 are as shown in the following [Equation 17].

[0092]

[Equation 17]

Here, sgn () is a function shown in [Equation 11]. Under the condition that Δθ is sufficiently smaller than π / 4, the absolute value of sin (Δθ) is smaller than “1”. Is also small enough to be neglected and cos
The property that (Δθ) is positive is used.

Then, the first multiplier 3a "and the second multiplier 3b" perform the operations of Ilim Q and Qlim I, respectively, and the subtractor 8 outputs the output of the first multiplier 3a ". I
Qlim I output from the second multiplier 3b ″ is subtracted from limQ, the waveform is shaped by the loop filter 4, and the VCO control signal V is calculated as in the following [Equation 18].

[0095]

(Equation 18)

Here, sin (Δθ) is given by Δθ = π / 4
Under the condition that the phase error is sufficiently smaller than Δθ, the phase error Δθ gradually converges to “0” as in the first main circuit, and the VCO 5 reproduces in synchronization with the carrier signal on the transmission side. It outputs a carrier signal.

According to the first to third circuits, the correlation peak value calculation section samples and holds the peak value of the correlation value, which is the result of the despreading, for one symbol time length, and uses the peak value. Since the carrier is reproduced, the carrier is not reproduced based on the signal of the so-called uncorrelated part, so that no noise is mixed into the VCO control signal,
Further, it is sufficient that the VCO control signal operation section operates only once after the peak value is held, and it is not necessary to operate the VCO control signal operation section all the time. Therefore, it is possible to output a stable reproduced carrier wave while reducing power consumption. There is.

[0098]

According to the present invention, the peak value of the despread signal per one symbol length of time is held, and the phase of the reproduced carrier is adjusted based on the held peak value. Since the carrier recovery circuit matches the phase of the recovered carrier to the phase of the carrier signal on the transmission side, the phase of the carrier is adjusted without being affected by so-called uncorrelated portions, which are portions other than the peak value, as noise. And the operation is performed intermittently,
This has the effect of reducing power consumption.

According to the second, third, fourth or fifth aspect of the present invention, the quadrature detection section performs quadrature detection on the signal of the reproduced carrier wave output from the VCO, and the correlation peak value calculation section performs quadrature detection. The signal of the phase component and the signal of the Q phase component are respectively despread, the respective correlation values are calculated, the peak values of the correlation value per one symbol length of time are held, and the VCO control signal calculation unit calculates The VCO control signal, which is substantially proportional to the error between the phase of the carrier on the transmitting side and the phase of the recovered carrier, is supplied to the VC
O, the VCO adjusts the phase in accordance with the VCO control signal, and the carrier recovery circuit outputs the recovered carrier. Therefore, the correlation peak value calculation unit holds the peak value of the correlation value, and the VCO control signal calculation unit By outputting the VCO control signal intermittently, there is an effect that power consumption can be reduced without being affected by a correlation value other than the peak value as noise.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of the present circuit.

FIG. 2 is a configuration block diagram illustrating an example of a first main circuit.

FIG. 3 is an explanatory diagram illustrating an example of a second main circuit.

FIG. 4 is a configuration block diagram illustrating an example of a third main circuit.

FIG. 5 is a configuration block diagram illustrating an example of a conventional carrier recovery circuit.

FIG. 6 is a configuration block diagram illustrating an example of a quadrature detector 1;

[Explanation of symbols]

1 ... quadrature detector 2, 2 '... matched filter,
3, 3 ′, 3 ″ multiplier, 4 loop filter, 5
... VCO, 6 ... Sample hold circuit, 7 ... Limiter, 8 ... Subtractor, 9 ... Adder, 10 ... Subtractor,
11: distributor, 12: multiplier, 13: phase shifter, 1
4 low-pass filter 21 correlation peak value calculation unit 22
... VCO control signal calculator

Claims (5)

[Claims] 1. A peak value of a despread signal per time of one symbol length is held, and a phase error between a carrier on the transmitting side and a reproduced carrier is calculated based on the held peak value. A carrier recovery circuit that adjusts the phase of a carrier to be recovered according to the result, and matches the phase of the recovered carrier with the phase of the carrier signal on the transmission side. 2. A quadrature detector, a correlation peak value calculator,
A VCO control signal calculation unit, a loop filter, and a VCO that outputs a reproduced carrier; and the quadrature detection unit performs quadrature detection on a received signal using a signal of the reproduced carrier input from the VCO. A quadrature detector that outputs a signal of a phase component and a signal of a Q phase component, wherein the correlation peak value calculator is a quadrature detected I-phase component signal and a Q-phase component signal input from the quadrature detector; Are respectively despread, and a peak value of a correlation value as a result of the despreading per time of one symbol length is detected, held, and output, and a correlation peak value calculation unit for outputting the VCO control signal calculation unit Is a VCO that outputs a VCO control signal that is substantially proportional to the error between the phase of the carrier on the transmitting side and the phase of the recovered carrier based on the peak value of the two correlation values corresponding to the I-phase component and the Q-phase component. Control signal calculation The loop filter is a loop filter for removing unnecessary components from the VCO control signal. The VCO receives an input of the VCO control signal via the loop filter, adjusts a phase, and reproduces. A carrier recovery circuit, which is a VCO that outputs a carrier signal. 3. A carrier recovery circuit for receiving a signal subjected to primary modulation and secondary modulation by BPSK and recovering a carrier wave, wherein a correlation peak value calculation unit includes an I-input signal input from a quadrature detection unit. A matched filter that despreads the signal of the phase component and the signal of the Q phase component, respectively, and outputs a resultant correlation value; and a correlation filter provided corresponding to the matched filter and input from the corresponding matched filter. A sample-and-hold circuit for holding the peak value of the correlation value while sampling the value for the time of one symbol length, wherein the VCO control signal operation unit receives an input of the I-phase component signal from the sample-and-hold circuit. And the peak value corresponding to
Multiplying the signal of the Q-phase component by the peak value corresponding to the VCO
3. The carrier recovery circuit according to claim 2, further comprising a multiplier that outputs the control signal. 4. A carrier recovery circuit for receiving a signal that has undergone primary modulation by QPSK and secondary modulation by BPSK and recovering a carrier, wherein a correlation peak value calculation unit is input from a quadrature detection unit. A matched filter that despreads the I-phase component signal and the Q-phase component signal and outputs the resulting correlation value, and a matched filter that is provided corresponding to the matched filter and is input from the corresponding matched filter. And a sample-and-hold circuit for holding the peak value of the correlation value while sampling the correlation value for one symbol length of time, and the VCO control signal operation unit determines that the sign of the peak value of the correlation value is positive. "+1" is output if negative, "-1" is output,
Two limiters corresponding to each of the I- and Q-phase components;
A first multiplier for multiplying a peak value of a correlation value of the Q-phase component output from the sample and hold circuit corresponding to the Q-phase component by a signal output from the limiter corresponding to the I-phase component; A second multiplier for multiplying the peak value of the correlation value of the I-phase component output by the sample and hold circuit corresponding to the component and the signal output by the limiter corresponding to the Q-phase component; 3. The carrier recovery circuit according to claim 2, further comprising: a subtractor for subtracting a signal output from the second multiplier from a signal output from the multiplier and outputting the subtracted signal as a VCO control signal. 5. A carrier recovery circuit for receiving a signal subjected to primary modulation and secondary modulation by QPSK and recovering a carrier wave, wherein a correlation peak value calculation unit includes an I-phase input from a quadrature detection unit. A first matched filter that outputs a first correlation value with an I-phase spreading code as a tap coefficient corresponding to the component signal and a Q-phase spreading code as a tap coefficient corresponding to the I-phase component signal , A second matched filter that outputs a second correlation value, a third matched filter that outputs a third correlation value corresponding to the signal of the Q-phase component and uses the I-phase spreading code as a tap coefficient, A fourth correlation value corresponding to the signal of the Q-phase component and outputting a fourth correlation value using the spreading code of the Q-phase as a tap coefficient.
, A correlation value calculation adder for adding the first correlation value and the fourth correlation value, and a correlation value calculation subtraction for subtracting the second correlation value from the third correlation value Corresponding to the adder for correlation value calculation and the subtractor for correlation value calculation, sample the signal input from the corresponding adder or subtracter for correlation value calculation for a time of one symbol length, And a sample-and-hold circuit that outputs the signal while holding the peak value of the signal. The VCO control signal operation unit outputs “+1” when the sign of the peak value of the correlation value is positive, and “ -1 "
Two limiters corresponding to each of the I- and Q-phase components;
A first multiplier for multiplying a peak value of a correlation value of the Q-phase component output from the sample and hold circuit corresponding to the Q-phase component by a signal output from the limiter corresponding to the I-phase component; A second multiplier for multiplying the peak value of the correlation value of the I-phase component output by the sample and hold circuit corresponding to the component and the signal output by the limiter corresponding to the Q-phase component; 3. The carrier recovery circuit according to claim 2, further comprising: a subtractor for subtracting a signal output from the second multiplier from a signal output from the multiplier and outputting the subtracted signal as a VCO control signal.