JP3184270B2 - Communication device having reference signal frequency calibration function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device using a heterodyne reception system, for example, a communication device having a frequency calibration function of a reference signal applicable to a digital automatic telephone or the like.

[0002]

2. Description of the Related Art A conventional technique for improving the accuracy of transmission and reception frequencies of an automobile telephone is disclosed in Japanese Patent Laid-Open No. 63-20020.
As disclosed in Japanese Patent Application Laid-Open Publication No. H10-209, after converting the frequency of a stable reception signal transmitted from a base station into a second intermediate signal frequency signal, the frequency is counted by a counting means, and the count value of the counting means is set in advance. The difference from the obtained second intermediate frequency reference value is obtained, and the transmission frequency adjustment control signal is set to VC-
TCXO (Voltage Controlled Crystal Oscillator)
And an arithmetic control unit for automatically outputting the frequency error within a predetermined range.

In the above automatic frequency control, the estimation accuracy of the frequency error based on the count value and the counting time have an opposite relationship. If the accuracy of the oscillator used as the time base of the frequency counting means is sufficiently high, an error of 10 Hz can be estimated in principle with a counting time of 100 ms.

On the other hand, microwave digital communication by time division multiplex communication has been put to practical use in digital car telephone systems. As a conventional technique related to a demodulation apparatus adapted for time division multiplex communication, a demodulation apparatus including a quasi-synchronous demodulation means for performing quadrature detection on a continuous phase modulated wave of constant amplitude using a fixed reference carrier to obtain a quasi-synchronous demodulation signal It has been known. For example, this is disclosed in JP-A-2-46044. In the conventional demodulator described above,
A relative deviation between the base station oscillation frequency and the fixed reference carrier and a phase rotation component due to carrier drift due to fading are extracted, and the fixed method is calculated by performing a first-order approximation to the accumulated phase rotation. The frequency error of the reference carrier is estimated. Since the above estimation processing is performed collectively on the burst data, the processing is completed at high speed within the time required for the arithmetic processing from the reception of the burst data.

[0005]

In mobile communication, it is essential to improve transmission frequency accuracy, for example, by narrowing the band even more in response to tight frequency. Therefore, the VC-TCXO controlled based on the reception frequency is provided, and the accuracy is improved by automatic frequency control in which the transmission frequency is set based on the VC-TCXO.

In time-division communication, it is necessary to operate in a burst mode, and an automatic frequency control device to be applied is required to have high speed. On the other hand, the counting of the frequency by the counting means takes a relatively long time, which is not desirable. Therefore, in the demodulation device including the quasi-synchronous demodulation means and the calculation means for estimating the frequency error, automatic frequency control for feeding back the estimation result to the VC-TCXO is considered. However, since the frequency error estimation is performed on the quasi-synchronous demodulated output, in a mobile communication device employing the double superheterodyne method, VC-TCX
VC-TC is estimated from the accumulated value of not only the deviation of O but also the frequency fluctuation of the second local oscillator and the fixed reference carrier generator, and also the carrier drift caused by fast fading.
It is difficult to correctly obtain only the XO deviation. In particular,
In a car telephone, since a relatively inexpensive oscillator is used as the second local oscillator, when the estimation result estimated from the accumulated value is directly fed back, the relative accuracy of the transmission frequency to the base station deteriorates. For example, if the first intermediate frequency is 90 MHz and the stability of the second local oscillator is 10 ppm in a 900 MHz-band mobile telephone device, a frequency error of 900 Hz results. If the transmission frequency is 900 MHz, the error becomes 1 ppm. Considering recent high accuracy,
This deterioration is a value that cannot be ignored and is a problem.

In order to improve the accuracy of the transmission frequency, for example, it is necessary to provide a high-precision oscillator in the second local oscillator. This is undesirable in terms of miniaturization and cost.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a communication apparatus capable of accurately obtaining a VC-TCXO (reference frequency oscillator) error and allowing the reference frequency oscillator to follow a base station with high accuracy.

[0009]

In order to achieve the above object, the present invention provides a first frequency conversion means for mixing a received signal with a first local oscillation signal and converting the signal into a first intermediate frequency signal. in the communication device and a second frequency converting means for converting the first intermediate frequency signal by mixing the second local oscillation signal to a second intermediate frequency signal, said first local onset
Reference frequency generating means for generating a reference signal serving as a reference for setting a transmission frequency of a communication signal; calibration signal generating means for outputting a calibration signal of a first intermediate frequency based on the reference signal;
Frequency estimation correction means for detecting a frequency error of the reference frequency generation means and outputting an oscillation frequency correction adjustment signal to the reference frequency generation means based on the frequency error, wherein the reference frequency generation means comprises an oscillation frequency correction adjustment The frequency of the reference signal can be changed by the signal, and the frequency estimation correction means detects and accumulates a frequency error A between the calibration signal converted to the second intermediate frequency and a preset reference intermediate frequency, further, when the frequency error B between the received signal and the reference intermediate frequency is converted into a second intermediate frequency, before
The error obtained by removing the frequency error A from the frequency error B
A corresponding frequency error C is detected, and an oscillation frequency correction adjustment signal is output based on the frequency error C.

The frequency estimating / correcting means includes a first frequency estimator for detecting and outputting a frequency error A between a calibration signal converted into a second intermediate frequency and a reference intermediate frequency; A phase compensator for correcting the phase of the received signal converted to the second intermediate frequency based on the frequency error A from the transmitter, and a frequency error between the received signal corrected by the phase compensator and the reference intermediate frequency. A second frequency estimator that detects C and outputs a frequency error signal; and a frequency correction unit that outputs an oscillation frequency correction adjustment signal to a reference frequency generation unit based on the frequency error signal from the second frequency estimator. Means.

The frequency estimating / correcting means includes a first frequency estimator for detecting and outputting a frequency error A between a calibration signal converted to a second intermediate frequency and a reference intermediate frequency, and at least a second frequency estimator. A second frequency estimator having a function of detecting a frequency error B between the received signal converted to the intermediate frequency and the reference intermediate frequency and outputting a frequency error signal;
Said frequency error based on the frequency error A from the first frequency estimator and frequency error B from the second frequency estimator
A frequency correction unit having a function of detecting a frequency error C corresponding to a difference obtained by subtracting the frequency error A from B and outputting an oscillation frequency correction adjustment signal to a reference frequency generation unit can be provided.

A phase compensator for correcting a phase of a received signal converted into a second intermediate frequency based on a frequency error A from the first frequency estimator;
The frequency estimator further has a function of detecting a frequency error C between the received signal converted to the second intermediate frequency and the reference intermediate frequency and outputting a frequency error signal. Based on the detection of the signal, an oscillation frequency correction adjustment signal is output to the reference frequency generation means.

The phase compensator can switch between a mode for correcting the phase of the received signal converted to the second intermediate frequency and a mode for outputting the received signal without correction. , position in response to the above mode
When performing phase correction, it is possible to detect the frequency error C and output an oscillation frequency correction adjustment signal to the reference frequency generation means.

The frequency estimating and correcting means includes a frequency estimator for detecting a frequency error A between the calibration signal converted to the second intermediate frequency and the reference intermediate frequency, a frequency memory for storing the frequency error A, And a frequency correcting means for outputting an oscillation frequency correcting adjustment signal to the reference frequency generating means, wherein the frequency estimator is configured to output a frequency error B between at least the received signal converted to the second intermediate frequency and the reference intermediate frequency. Has the function of detecting the
The frequency correction unit outputs a signal before output from the frequency estimator.
From the frequency error B, output from the frequency memory
A frequency error C corresponding to a difference obtained by subtracting the frequency error A
The adjustment signal for oscillation frequency correction can be output based on the

A phase compensator for correcting the phase of the received signal converted to the second intermediate frequency based on the frequency error A from the frequency memory, wherein the second frequency estimator is 2. A frequency error C between the received signal converted to the intermediate frequency 2 and the reference intermediate frequency is detected to output a frequency error signal, and the frequency correction unit sends the oscillation frequency to the reference frequency generation unit based on the frequency error signal. Outputs a correction signal for correction.

The phase compensator can switch between a mode for correcting the phase of the received signal converted to the second intermediate frequency and a mode for outputting the received signal without correction. , position in response to the above mode
When the phase is corrected, the frequency error C is detected, and the oscillation frequency correction adjustment signal is output to the reference frequency generating means.

Further, by providing the second phase compensator, the received signal can be corrected.

Further, the apparatus may further include a control unit for instructing the calibration signal generating means to generate a calibration signal.

[0019]

According to the present invention, prior to communication with a base station,
A calibration signal is output from the calibration signal generation unit, the calibration signal is converted to a second intermediate frequency signal by a second frequency conversion unit, and the frequency estimation correction unit determines in advance the calibration signal converted to the second intermediate frequency and It is possible to detect and accumulate a frequency error A (that is, an error in the oscillation frequency of the second station oscillator) generated by the second frequency conversion means, which is an error from the set reference intermediate frequency. Further, at the time of reception of the received signal, the received signal is converted into a second intermediate frequency signal by the second frequency conversion means, and the frequency estimation correction means converts the received signal converted into the second intermediate frequency and the reference intermediate frequency. The frequency error B is detected. Further, the frequency estimation correction means detects the frequency error C by removing the frequency error A from the frequency error B, and outputs an oscillation frequency correction adjustment signal based on the frequency error C.

In the case where a phase compensator is provided, the received signal converted to the second intermediate frequency and the reference intermediate frequency are used to correct the received signal for the frequency error A. The error C can be detected.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a communication apparatus showing a first embodiment of the present invention. The communication device shown in FIG. 1 is, for example, a mobile communication device, and can control the reference oscillator so as to follow the frequency of the base station when communicating with the base station. In FIG. 1, reference numeral 1 denotes a shared antenna for transmission and reception;
Is a duplexer, which separates a transmission signal and a reception signal.
3, 5, and 7 are amplifiers for amplifying the received signal.
Reference numeral 4 denotes a first frequency conversion means, which outputs the output of the amplifier 3 to the first frequency conversion means.
It is a first frequency converter for converting to an intermediate frequency signal. 6
Is a second frequency converter, which is a second frequency converter that converts the first intermediate frequency signal amplified by the amplifier 5 into a second intermediate frequency signal. Reference numeral 8 denotes a quasi-synchronous detector, which performs quadrature detection on the second intermediate frequency signal amplified by the amplifier 7 using a fixed reference carrier set to the same frequency as the second intermediate frequency, and outputs a quasi-synchronous demodulated signal. 9 is a counter, the second
The frequency of the intermediate frequency signal is counted. Reference numeral 10 denotes a first phase compensator, which outputs a count value output from the counter 9 and a preset ideal second intermediate frequency value (hereinafter, referred to as a second frequency reference value) to a frequency error estimator. Then, a frequency error of the second intermediate frequency signal is obtained from the result and accumulated, and the phase rotation given to the received signal due to the frequency error is compensated.

The first frequency estimator has a counter 9 and a frequency error estimator in the phase compensator 10. 11
Is a second frequency estimator, which extracts a phase rotation component caused by a residual frequency error by removing a modulation component from an output of the phase compensator 10, and performs a first-order approximation of the accumulation of the phase rotation component to obtain the frequency rotation component. Estimate the error. Reference numeral 12 denotes a second phase compensator, which performs phase compensation on the output of the phase compensator 10 based on the frequency error output from the frequency estimator 11.
A decoder 13 converts the output of the phase compensator 12 into binary data. Reference numeral 14 denotes a frequency correction circuit, which is a frequency correction unit that outputs an oscillation frequency adjustment control signal corresponding to the frequency error output from the frequency estimator 11. The frequency estimation correction means includes a frequency estimator of the counter 9, a phase compensator 10, a frequency estimator 11, and a frequency correction circuit 14.
And Reference numeral 15 denotes a reference oscillator whose oscillation frequency is controlled by the frequency correction circuit 14. Reference numeral 16 denotes a first local oscillator, the oscillation frequency of which is set based on the reference oscillator 15. Reference numeral 17 denotes a calibration signal generator, which is a calibration signal generator that generates a calibration signal having the same frequency as the first intermediate frequency based on the reference oscillator 15. A coupling capacitor 18 inputs a calibration signal to the amplifier 5. The calibration signal generation means includes a coupling capacitor 18 and a calibration signal generator 17.
Can be provided. Further, the calibration signal generator 17
When oscillating at the same frequency as that of the received signal, the calibration signal generation means can include a coupling capacitor 18, a calibration signal generator 17, a first local oscillator, and a first frequency conversion means 4. 19 is a second local oscillator, 20 is a control unit, and the amplifier 3, the counter 9, the first local oscillator 1
6. Control the operation of the calibration signal generator 17 and the like. A modulator 21 generates a complex baseband signal digitally modulated by a binary data sequence. A transmitter 22 converts the complex baseband signal into a transmission frequency.

Next, the operation will be described.

First, the process of estimating the frequency error of the second local oscillator 19 will be described. First, when the power of the communication device is turned on, the control unit 20 controls the calibration signal generator 17 so as to correct the frequency error of the second local oscillator 19.
And the counter 9. Further, the control unit 20 may be configured to periodically instruct, for example, when the temperature is not received, or to provide an instruction when the temperature becomes equal to or higher than a predetermined temperature by having a temperature sensor. Upon receiving an instruction, the calibration signal generator 17 generates a first intermediate frequency signal as a calibration signal based on the oscillation frequency of the reference oscillator 15. The signal generated here is input to the second frequency converter 6 via the coupling capacitor 18 and the amplifier 5. At this time, the operation of the amplifier 3 and the first local oscillator 16 is stopped by an instruction of the control unit 20 so that unnecessary signals are not mixed into the first intermediate frequency signal. In the second frequency converter 6, the signal from the second local oscillator 19 and the first
The signal is mixed with the intermediate frequency signal and converted to a second intermediate frequency signal. This second intermediate frequency signal is counted by the counter 9.

The frequency error of the second local oscillator 19 is determined from the frequency difference between the count value of the counter 9 and the second intermediate frequency reference value. For example, when the count value is higher than the second intermediate frequency reference value, the second local oscillator oscillates below the reference value of the frequency difference and the ideal oscillation frequency. This is because frequency mixing in frequency converter 6
Because the difference component between the two input frequencies is extracted, the frequency error of the second local oscillator 19 is directly transmitted to the second intermediate frequency signal. The estimation of the frequency error is executed inside the phase compensator 10. That is, the phase compensator 10 stores the second intermediate frequency reference value, detects a frequency error by comparing the count value of the second intermediate frequency with the reference value, and stores the frequency error. deep. The frequency error contained in this second intermediate frequency signal, ie,
The frequency error of the second local oscillator is called frequency error A. During reception, the phase compensator 10 removes the frequency error from the second intermediate frequency of the received signal. This will be described in the next operation.

As described above, when instructed by the control unit 20, a calibration signal is generated from the calibration signal generator 17 and converted into the second intermediate frequency signal by the second frequency converter 6, and
The intermediate frequency signal is counted by the counter 9. Further, in the phase compensator 10, when a count value is input from the counter 9, a frequency error can be estimated and the frequency error can be accumulated. The frequency error includes the frequency error of the second local oscillator 19 and the calibration signal generator 17, ie, the reference oscillator 1
5, the reference oscillator 15 has a frequency error of
Since the accuracy is higher than that of the second local oscillator 19, most of the frequency errors are caused by the second local oscillator 19.

Next, an operation in which the oscillation frequency of the reference oscillator 15 is controlled by the received signal will be described. The received signal received by the transmission / reception shared antenna 1 and separated by the duplexer 2 is
The signal is input to the first frequency converter 4 via the amplifier 3. The first frequency converter 4 mixes the output signal of the first local oscillator 16 and the received signal set with the reference oscillator 15 as a reference, and converts the mixed signal into a first intermediate frequency signal. After that, the first intermediate frequency signal is converted into a second intermediate frequency signal via the amplifier 5, the second frequency converter 6, and the amplifier 7, and is input to the quasi-synchronous detector 8. The quasi-synchronous detector 8 performs quadrature detection using a fixed reference carrier set to the second intermediate frequency to obtain a quasi-synchronous demodulated signal as a two-dimensional complex baseband signal. Therefore, the quasi-synchronous demodulated signal includes a frequency rotation between the first local oscillator 16, the second local oscillator 19, and the fixed reference carrier, and includes a phase rotation due to the frequency error. This will be described later.

The quasi-synchronous demodulated signal is supplied to the phase compensator 1
Based on the above-described estimation result of the frequency error of the second local oscillator 19, which is input to 0 and accumulated in the phase compensation unit 10, a considerable amount of phase compensation is performed. At this time, since the phase compensator 10 compensates for the frequency error A, the error estimated by the frequency estimator 11 is to estimate the frequency error of the reference oscillator 15. The frequency error of only the reference oscillator 15 is called a frequency error. That is, the frequency error when the received signal is modulated and the phase of the second local oscillator is estimated without phase compensation of the error of the second local oscillator is represented by the frequency error B (that is, the frequency error B includes the error of the second local oscillator and the error of the second local oscillator). , Including the frequency error of the reference oscillator 15), the error obtained by removing the frequency error A from the frequency error B is
A frequency error C results. The frequency estimator 11 removes a modulation component from the output of the phase compensator 10, estimates a frequency error C from the remaining phase rotation component, and outputs a frequency error signal. The frequency error signal of the frequency estimator 11 is input to the frequency correction unit 14 and the second phase compensation unit 12. The frequency correction unit 14 outputs an oscillation frequency adjustment control signal for controlling the oscillation frequency of the reference oscillator 15 in a direction in which the frequency error signal of the frequency estimator 11 is minimized. Second
The error component of the local oscillator 19 is compensated as described above, and the oscillation frequency adjustment control signal output from the frequency estimator 11 is most affected by the frequency error of the first local oscillator 16 set by the reference oscillator 15. ing. The frequency correction unit 14 corrects the reference oscillator 15 based on the oscillation frequency adjustment control signal, so that the reference oscillator 15
Will accurately follow the transmission frequency of the base station.

The output of the synchronization compensator 10 is also input to the phase compensator 12 to perform phase compensation corresponding to the frequency error estimated by the frequency estimator 11 to establish synchronization. The synchronized demodulated signal is output to the decoder 13 and converted into binary data.

For transmission, since the transmission frequency is set based on the reference oscillator 15, the base station is followed by the oscillation frequency control of the frequency correction unit 14.

Next, the details of the main part will be described.

FIG. 2 is a configuration diagram of the quasi-synchronous detector 8. In FIG. 2, reference numeral 801 denotes a fixed reference carrier oscillator. 8
Reference numerals 02 and 804 denote mixers that detect signals using the in-phase and quadrature components of the oscillation frequency of the fixed reference carrier oscillator 801 set to the second intermediate frequency. 803 is π / 2
A phase shifter for generating the quadrature component; A / D converters 805 and 806 sample the detection output. S (t) is a second intermediate frequency signal,
I (t) and Q (t) are an in-phase component and a quadrature component of a complex baseband signal subjected to quadrature phase detection. In and Q
Let n denote the sampled digital signal. If the complex baseband signals I (t) and Q (t) are I and Q, respectively, when there is no frequency error, and the accumulated frequency error is fe,

[0034]

(Equation 1)

Can be represented by Further, if the sampling period of the A / D converter is Ts,

[0036]

(Equation 2)

Therefore, the quasi-synchronous demodulated signal is

[0038]

(Equation 3)

Can be expressed as follows. The first phase compensation is performed on the quasi-synchronous demodulated signal by the phase compensation unit 10. The details will be described below.

FIG. 3 is a configuration diagram of the phase compensator 10. In FIG. 3, reference numeral 101 denotes a frequency error estimator which stores a second frequency reference value in a memory, and calculates a frequency count value of the second intermediate frequency signal from the counter 9 and the second frequency reference value. In comparison, the frequency error A is estimated, accumulated, and output. 102 is a digital VCO (Voltage Controlled)
Oscillator) 103 is a complex multiplier. The estimated output frequency of the frequency error estimator 101 is f2, the phase compensation signal output from the digital VCO is Cn, and the compensated quasi-synchronous demodulation signals are represented by In 'and Qn'.

The count value of the counter 9 is calculated by the frequency error estimator 1
01 is input. The frequency error estimator 101 compares the count value with the second frequency reference value, detects the frequency error A of the second local oscillator 19 from the difference, accumulates and outputs the frequency error A. Estimated output frequency f of estimated frequency error A
2 is input to the digital VCO. Digital VCO
Outputs a digital signal for phase compensation represented by the following equation.

[0042]

(Equation 4)

In the complex multiplier 103, the phase compensation signal Cn
Is complex-multiplied with In and Qn, respectively. As a result, the output of the phase compensator 10 is

[0044]

(Equation 5)

Will be obtained.

In ′ and Qn ′ are input to the frequency estimator 11, where the remaining frequency error C (fe−f
2) and output a frequency error signal. As an estimation method, for example, Junji Namiki, “Batch accumulation demodulation method for short wireless packets” IEICE Transactions Vol.J67 / B No.1 pp54-6
1,1984. Basically, a complex quasi-synchronous demodulated signal is converted into angle information for calculation. For example,
In the case of an M-phase PSK signal, the modulation component is removed by multiplying by M. Then, a phase rotation amount for each modulation symbol is extracted, a first-order approximation is performed on the accumulation of the phase rotation, and a frequency error is calculated from the slope of the approximate straight line. However, in order to obtain a result correctly by one estimation, it is necessary to suppress the phase rotation amount within 2π / M in one symbol section which is the reciprocal of the modulation speed. This is because the absolute amount of the frequency error input to the frequency estimator 11 can be reduced by arranging the first phase compensator in the preceding stage of the frequency estimator 11, so that the phase rotation is caused by 2π / M or more and the frequency is increased. The probability of erroneous estimation can be reduced.

FIG. 4 is a block diagram of the second phase compensator 12. 121 is a digital VCO, 122 is a complex multiplier, and the digital VCO 121 is given (fe−
f2) is used to generate an estimated output frequency f ₁₂₁ shown in the following equation.

[0048]

(Equation 6)

Then, the complex multiplier 122 removes the phase rotation, and gives a synchronous demodulated signal of I + jQ which does not include a frequency error as In "+ jQn".

The frequency corrector 14 is provided for adjusting the oscillation frequency of the reference oscillator 15 in the direction of minimizing the frequency error signal of the frequency estimator 11 based on the frequency error signal from the frequency estimator 11. Outputs control signal.

The control signal for adjusting the oscillation frequency is determined by the following calculation procedure.

First, the frequency estimator 11 estimates the frequency difference between the count value and the second intermediate frequency reference value, and outputs a frequency error signal. Next, the frequency correction unit 14
If [count value]> [second intermediate frequency reference value], the oscillation frequency adjustment control signal value is adjusted so that the oscillation frequency of the reference oscillator 15 becomes higher. Since the reference oscillator 15 is adjusted by this adjustment operation, the first local oscillation frequency is also increased, and the difference from the received signal frequency is reduced. As a result,
The frequency of the second intermediate frequency signal decreases, and the count value also decreases.

On the contrary, if [count value] <[second intermediate frequency reference value] in the frequency estimator 11, the frequency correction unit 14 controls the oscillation frequency adjustment so that the oscillation frequency of the reference oscillator 15 becomes lower. Adjust the signal value. This adjustment operation also lowers the first local oscillation frequency and increases the difference from the received signal frequency. As a result, the frequency of the second intermediate frequency signal increases, and the count value increases.

In this embodiment, the degree of adjustment of the oscillation frequency adjustment control signal value is changed by a correction coefficient according to the frequency difference. For example, when the frequency difference is large, the adjustment width is increased. This speeds up the convergence of the operation.

With the above operation, the oscillation frequency of the reference oscillator 15 is adjusted so that the frequency of the second intermediate frequency signal approaches the second intermediate reference frequency.

Next, the operation will be further described with reference to a specific example.

As an operation example of the embodiment shown in FIG. 1, the reception frequency is 1090 MHz, the oscillation frequency of the first local oscillator 16 is 1000 MHz, the first intermediate frequency is 90 MHz, and the second
The intermediate frequency is 455 kHz, the frequency error of the reference oscillator 15 is 3 ppm, and the frequency error of the second local oscillator is about 100
Assume that the oscillation frequency of the second local oscillator is 89.536 MHz with a shift of 9 kHz in ppm.

The setting of the first local oscillator 16 is set to 1000 MH
Assuming that z, the frequency error of the reference oscillator 15 is actually 3 ppm, so that the oscillation frequency of the first local oscillator 16 includes an error and outputs, for example, 1000.003 MHz. Therefore, 1
The 090 MHz signal is output to the first frequency converter 4 at 1
090MHz minus 1000.003MHz minus 8
The frequency is converted to 9.997 MHz, and further, 89.536 MHz is subtracted by the second frequency converter 6 to be converted to 461 kHz, which is output as a second intermediate frequency signal.

If the error of the second intermediate frequency is estimated only by the frequency estimator 11 using only one phase compensating unit as in the prior art, the second intermediate frequency signal becomes the first local oscillator and the second local oscillator. Includes 2 local oscillator errors, 455k
The error from Hz is 6 kHz. In this case 1000MH
Since it is determined as an error of −6 ppm with respect to z, the reference oscillator is controlled to be 3 + 6 = 9 ppm, and conversely, the frequency accuracy is deteriorated.

In this embodiment, as shown in FIG.
Since the frequency error of the second local oscillator 19 and the reference oscillator 15 is obtained in advance using the calibration signal, the phase compensator 10 removes the frequency error of the second local oscillator 19 from the second intermediate frequency signal of the received signal. . Further, the frequency estimator 11 estimates the error of the reference oscillator 15 and
The error of the estimated reference oscillator 15 is removed, and the frequency correction circuit 14 controls the reference oscillator 15 with high accuracy.

That is, the calibration signal generator 17 generates the first intermediate frequency 90 MHz based on the reference oscillator 15. Now, since the stability of the reference oscillator 15 is set to 3 ppm, the calibration signal becomes about 90.0003 MHz, 89.536 MHz is subtracted by the second frequency converter 6, and 464.3 kHz is output as the second intermediate frequency signal. This is counted by the counter 9 and the difference 8.7 kHz from 455 kHz is estimated by the frequency error estimator 101 of the phase compensator 10 and stored.

The 461 kHz second intermediate frequency signal of the received signal is corrected by the first frequency corrector 10 to 8.7 kHz corresponding to the estimated value.
61-8.7 = 452.3 kHz will be input. Therefore, the frequency estimator 11 calculates 452.3-455 =
-2.7 kHz, which is determined as +2.7 ppm for 1000 MHz, so that the reference oscillator is 3 kHz.
It is controlled so that -2.7 = 0.3 ppm. As a result, the frequency accuracy of the reference oscillator 15 is set to an absolute accuracy of 3 ppm.
Then, the base station tracking accuracy can be controlled to 0.3 ppm, and the frequency error can be suppressed to 1/10.

The timing of the above operation will be described with reference to the timing charts shown in FIGS. FIG.
5 is an explanatory diagram of an initial operation of frequency control. FIG. 16 is an explanatory diagram of the operation in the standby state. 15 and 16
, S1, S2, and S3 are assigned slots in time-division communication, and exemplify a case where there are three frequency channels. In this case, the S1 channel is received.

In FIG. 15, when the power of the mobile communication device is turned on, first, in order to obtain an error of the second local oscillator 19, the control unit 20 operates the calibration signal generator 17 to indicate a period 1A. During the period, the counter 9 counts the second intermediate frequency signal, and the phase compensator 10 estimates and accumulates the frequency error of the second local oscillator 19. Next, when the transmission data is received for one slot period (section 1B), the frequency estimator 11 is received by the received signal in a period indicated by section 1C.
Estimates the error component of the reference oscillator 15, and the frequency correction unit 14 corrects the reference oscillator 15 based on the frequency error signal. In the period of the section 1A, a time sufficient for obtaining necessary frequency accuracy is provided before starting reception. For example, in the above specific example, when the first intermediate frequency signal is 90 MHz and the frequency error of the reference oscillator 15 is 3 ppm, ± 270 Hz
37 ms (1/270)
The above counting time may be provided. The period of section 1C is S
Processing can be sufficiently performed until the next time slot of one channel comes. Alternatively, the base station may transmit a transmission signal for correcting the reference oscillator 15 separately from normal data.

Next, an example in which the mobile communication apparatus establishes slot synchronization with the base station and is in a transmission / reception standby state will be described with reference to FIG. In FIG. 16, it is assumed that the mobile communication device is synchronized with slot ST # 1 (S1). The mobile communication device receives data of its own assigned slot ST # 1 indicated by sections (n-1) B and nB, and monitors a call from the base station. At this time, the second
When re-estimating the frequency error of the local oscillator, the calibration signal is oscillated by using the empty slot period, and the counter 9 counts the second intermediate frequency signal and the phase compensator 10 as described above. Estimates the frequency error of the second local oscillator 19. In FIG. 16, sections (n-1) A and n
An example in which counting is performed during the period of ST # 3 (S3) indicated by A is shown. If one slot time is not sufficient, the frequency error may be estimated using a value obtained by accumulating a plurality of counts. In this case, since the reference oscillator 15 is controlled to follow the base station and the accuracy is improved, the error of the second local oscillator 19 can be accurately estimated.

As described above, in the first embodiment, the frequency error of the second local oscillator 19 is counted in advance by using the calibration signal.
After suppressing the error of the local oscillator, frequency estimation is performed by the frequency estimation 11, so that high-speed and high-accuracy automatic frequency control can be achieved. Further, since the counter 9 only needs to be able to count the second intermediate frequency and the frequency to be counted is low, there is an effect that the counter 9 can be easily formed into a CMOS-LSI.

Further, since the phase compensator is arranged at the preceding stage of the frequency estimator 11, the absolute amount of the frequency error input to the frequency estimator 11 can be reduced. This is the first local oscillator 16
When the error between the second local oscillator 17 and the second local oscillator 17 is large, the phase rotation of one symbol interval due to the frequency error in the output of the quasi-synchronous demodulated signal is caused by the phase modulation component, in other words, the minimum transition amount between modulation symbols (for example, / 2 [r
ad]) As described above, there is an effect that the probability of causing phase rotation and erroneous frequency estimation can be reduced.

In this regard, since the frequency estimation of the second local oscillator is performed using the counter 9, the estimation error when the absolute amount of the modulation frequency error is large can be eliminated.

Next, a second embodiment of the present invention will be described. FIG. 5 is a configuration diagram of a mobile communication device according to the second embodiment, in which parts equivalent to those in FIG. 1 are denoted by the same reference numerals. In FIG. 5, reference numeral 14A denotes a frequency correction unit which controls the reference oscillator 15 with a value obtained by correcting the frequency error of the second local oscillator estimated from the count output of the frequency error signal of the frequency estimator 11.

The difference between the second embodiment shown in FIG. 5 and the first embodiment described above is that the phase compensator 10 is removed.
The quasi-synchronous demodulation output of the quasi-synchronous detector 8 is directly used as the frequency estimator 1
1 and the input to the phase compensator 12 and the count output of the counter 9 to the frequency corrector 14A. The frequency corrector 14A is estimated from the count output of the frequency error signal of the frequency estimator 11. The configuration is such that the reference oscillator 15 is controlled with a value obtained by correcting the frequency error of the second local oscillator. That is, when estimating the frequency error of the reference oscillator 15 without directly correcting the frequency error of the second local oscillator with respect to the received signal, the frequency correcting unit 14A first sets the frequency error of the second local oscillator. The error is corrected, the frequency error of the reference oscillator 15 is estimated, and the oscillation frequency of the reference oscillator 15 is controlled. In this case, the frequency estimation correction means includes a counter 9 as a first frequency estimator and a frequency estimator 1 as a second frequency estimator.
1 and a frequency correction unit 12.

The operation will be described in a specific example similarly to the first embodiment. The reception frequency is 1090 MHz, the oscillation frequency of the first local oscillator 16 is 1000 MHz, the first intermediate frequency is 90 MHz, the second intermediate frequency is 455 kHz, and The frequency error of the reference oscillator 15 is 3 ppm, and the second local oscillator 1
6 is about 10 ppm, and the oscillation frequency is 89.546 MHz with a shift of 1 kHz.

The calibration signal indicates that the stability of the reference oscillator 15 is 3
ppm, it becomes 90.0003 MHz, and the second
When converted to the second intermediate frequency by the frequency converter 6,
454.3 kHz is obtained as an intermediate frequency signal. The second intermediate frequency signal is counted by the counter 9. The frequency correction unit 14A calculates the difference between 455 kHz and 454.3 kHz.
+ 0.7pp from 0.7kHz to 1000MHz
The correction value of m is obtained and stored.

At the time of communication with the base station, the reception frequency 109
The signal of 0 MHz is 1000.00 in the first frequency converter.
Subtract 3 MHz and convert to 89.997 MHz.
451 kHz by subtracting 89.546 MHz with a frequency converter
z is obtained as a second intermediate frequency signal. This is directly input to the frequency estimator 11 to estimate a difference of −4 kHz from the reference value of 455 kHz, and output it to the frequency correction unit 14A and the phase compensation unit 12. The frequency correction unit 14A has a frequency of -4 kHz.
From the estimated value of z, it is determined that the error is +4 ppm, and further, using the correction value +0.7 ppm for subtracting the error of the second local oscillator 16 obtained in advance, 4-0.7 =
3.3 ppm is obtained as the frequency error of the reference oscillator 15. As a result, the reference oscillator 15 is controlled by the frequency correction unit 14A so that 3-3.3 = -0.3 ppm.

According to the second embodiment, the second local oscillator 1
6 is high, the frequency correction unit 14A
The oscillation frequency of the reference oscillator 15 can be controlled by removing the error of the local oscillator and estimating the frequency error of the reference oscillator 15.

In the second embodiment, the phase correction unit 10
Is eliminated, the number of complex multiplication processes for phase compensation may be one, and the power consumption can be reduced as compared with the first embodiment.

Next, a third embodiment will be described with reference to FIGS. FIG. 6 is a configuration diagram for explaining the configuration of the third embodiment in the mobile communication device, and the same reference numerals are given to the same components as those in the first embodiment. The omitted circuit portions have the same configuration as that of the first embodiment. In FIG. 6, reference numeral 23 denotes a switch, and the quasi-synchronous outputs In and Qn of the quasi-synchronous detector output 8 and the outputs In ′ and Qn ′ of the phase compensator 10.
A signal of either one of the combinations is selectively output, and input to the frequency estimator 11 and the second phase compensator 12. Reference numeral 20B denotes a control unit, which is a frequency estimator 1
1 to control the automatic frequency control function including the switch 23. A frequency correction unit 14B is connected to the count output of the counting circuit 9, the estimated output of the frequency estimator 11, and the control output of the control unit 20, and controls the oscillation frequency of the reference generator 15.

This embodiment is characterized in that the first and second embodiments described above are used in combination. That is, in the present embodiment, when the power is turned on or the like, the frequency error of the second local oscillator 19 is compensated through the phase compensator 10, and the frequency estimator 11 The error is estimated, and the frequency corrector 14B controls the reference oscillator 15 to increase the accuracy of the reference oscillator 15. Thereafter, the control unit 20B switches the switch 23 so as not to pass through the phase compensation unit 10. The switching instruction of the control unit 20B is switched between the time of reception and the time of non-reception, output after a predetermined time has elapsed, or by monitoring the estimated output of the frequency estimator 11, When the error becomes equal to or less than a predetermined value, a switching instruction is output. Further, by monitoring the estimated output of the frequency estimator 11, if the frequency error increases,
The switch 23 may be switched again so as to pass through the phase compensation unit 10. In this case, the frequency correction unit 14B
Switches the operation due to the frequency error depending on whether the signal passes through the phase compensation unit 10 or not. That is, when the signal passes through the phase compensator 10, an oscillation frequency adjustment control signal is output based on the frequency error from the frequency estimator 11. When not passing through the phase compensating unit 10, the control signal for adjusting the oscillation frequency is output based on the frequency error from the counting circuit 9 and the frequency error from the frequency estimator 11.

FIG. 7 shows an operation flow of the automatic frequency control process having the above configuration. The operation flow in FIG. 7 is based on the assumption that the base station and a plurality of mobile communication devices perform communication by time division multiplexing, and the unit of processing of the frequency estimator 11 is a slot allocated to time division and corresponds to burst reception. An example in which the operation is performed as follows.

First, the calibration signal generator 17 outputs a calibration signal, and the calibration signal is converted into a second signal by the second frequency converter 6.
After being converted into the intermediate frequency signal, the counter 9 counts the second intermediate frequency signal (process 71). The output of the counter 9 is input to the phase compensator 10 and the frequency corrector 14B. Next, the control unit 20B connects the switch 23 to the outputs In ′ and Qn ′ of the phase compensation unit 10 and starts the receiving operation. The phase compensator 10 estimates the frequency error of the second local oscillator 19 on the quasi-synchronous demodulated signal of the quasi-synchronous detector 8 based on the output of the counter 9 counted in advance, and performs considerable phase compensation. Then, the output is output to the frequency estimator 11 via the switch 23, the remaining frequency error is estimated by the frequency estimator 11, and the estimated output is sent to the frequency correction unit 14B (the above processing 72). At this time, the frequency correction unit 14
B is based on the frequency error from the frequency estimator 11,
The reference oscillator 15 is controlled by the oscillation frequency adjustment control signal (step 73). Next, the control unit 20B determines the continuation of the communication (step 74).
3 is connected to the quasi-synchronous demodulated signals In and Qn of the quasi-synchronous detector 8. Then, the frequency estimator 11 estimates the reception frequency error including the frequency error of the second local oscillator 19 (process 75). The frequency correction unit 14B includes the control unit 20
, The oscillation frequency control output provided from the output of the frequency estimator 11 is corrected by the correction value calculated from the count output to control the reference oscillator 15 (processing 76). Next, the control unit 20 determines continuation of communication (process 77). When the next allocation slot is also received continuously, it is determined whether or not the estimated output of the frequency estimator 11 is equal to or more than a specified value preset by the control unit 20B (process 78). If the frequency error increases and exceeds the specified value, the next processing is processing 7
Starting from 2, the process is repeated from step 75 if the value is less than the specified value.

In summary, in the third embodiment, the second local oscillator is connected via the first phase compensator 10 in case the base station deviation of the first local oscillation frequency is large before the automatic frequency control is performed. The frequency error of the quasi-synchronous demodulation signal input to the frequency estimator 11 is suppressed by compensating the frequency error of the frequency estimator 19 to reduce the probability of causing an estimation error. After the automatic frequency control is performed once to reduce the base station deviation of the first local oscillation frequency, the processing of the first phase compensator 10 is omitted to reduce the power consumption, and the error of the second local oscillator 19 is reduced. The component related to the correction is corrected by the frequency correction unit 14B. Further, when the frequency error increases during the communication, the automatic frequency control with the first phase compensator 10 interposed is performed again.

Next, a fourth embodiment of the present invention will be described. FIG. 8 is a configuration diagram of a mobile communication device according to a fourth embodiment. In FIG. 8, reference numeral 10A denotes a phase compensation unit, and 24 denotes a frequency memory, which stores an estimated output of the frequency error of the frequency estimator 11. In addition, the same parts as those in the first embodiment are denoted by the same reference numerals. The phase compensating unit 10A performs phase compensation on the output of the quasi-synchronous demodulation signal of the quasi-synchronous detector 8 based on the output from the frequency memory 24. Its purpose is to provide the second
The purpose is to compensate for the frequency error of the local oscillator 19. In this case, the frequency estimation correction means includes a frequency estimator 11;
It has a frequency memory 24 and a frequency correction unit 14, and can further have a phase compensation unit 10A.

FIG. 9 shows the internal configuration of the phase compensator 10A. A digital VCO 102A generates a phase compensation signal for phase compensation based on the output from the frequency memory 24. A complex multiplier 103A multiplies the quasi-synchronous demodulated signals In and Qn by a complex number of the phase compensation signal from the digital VCO 102A. A switch 104 selects one of the complex multiplier outputs In ′ and Qn ′ and the quasi-synchronous detection outputs In and Qn as an output of the phase compensation unit 10A. The selection control of the switch 104 is performed by the output of the control unit 20 (FIG. 8). The quasi-synchronous demodulation signal In
When Qn and Qn are selected as outputs, complex multiplier 103A and frequency memory 102A stop operating,
It is intended to reduce power consumption. In this embodiment,
By providing the phase compensator 10A having the above configuration, the second
The frequency error of the local oscillator 19 can be estimated by the frequency estimator 11.

FIG. 10 is a time chart showing the relationship between the evaluation of the second local oscillator 19 and the base station following operation. The time chart illustrated in FIG. 10 illustrates an example in which the base station performs time-division communication with three mobile communication devices using one frequency channel. In FIG. 10, S1, S2 and S3 indicate time division time slots. The operation of the frequency control in the present embodiment is shown in the operation flow of FIG. FIG.
The operation of frequency control will be described with reference to FIG.

When the power is turned on, the control unit 20 operates the calibration signal generator 17 to estimate the frequency error of the second local oscillator during the period A, and the calibration signal generator 17 uses the reference oscillator as a reference. The second frequency converter 6 converts the calibration signal into a second intermediate frequency signal, and the quasi-synchronous detector 8 performs quasi-synchronous detection on the second intermediate frequency signal. In the phase compensator 10A, the switch 104 shown in FIG. 9 selectively outputs the quasi-synchronous demodulated signals In and Qn according to an instruction from the controller 20. The frequency estimator 11
The frequency error of the second local oscillator 19 is estimated from the output of the phase compensation unit 10A (1101), and the frequency error is stored in the frequency memory 102A. Thereafter, data from the base station is received for a certain period in the period B, and the reference oscillator 15 is corrected by base station tracking control in the period C (1102). The switch 104 selects the outputs In 'and Qn' of the complex multiplier 103A of FIG. The digital VCO 102A shown in FIG. 9 generates a compensation signal shown in the equation (4) described in the first embodiment based on the value stored in the frequency memory 24. And the complex multiplier 103A
Then, the signals In ′ and Qn ′ that compensate for the phase rotation due to the frequency error of the second local oscillator are input to the frequency estimator 11. The frequency estimator 11 estimates the remaining frequency error, which is output to the frequency correction unit 14, and the reference oscillator 15 controls the oscillation frequency so as to minimize the frequency error. In other words, the frequency error of the reception frequency is estimated by the frequency estimator 11 using the signal phase-compensated by the phase compensation 10A based on the frequency error evaluated in the section A. Subsequently, the control unit 20 determines that communication is to be continued (110
3) If continuing, a calibration signal is output during the idle time of the time slot to re-estimate the frequency error of the second local oscillator 19, and the value stored in the frequency memory 24 is updated (1104). As described above, the estimated value of the frequency error of the second local oscillator can be sequentially corrected in accordance with the operation of the frequency control following the base station. Then, the frequency estimator 11 determines the convergence of the estimated value of the frequency error (1
105). In this case, the convergence of the estimated value means that the estimation of the second intermediate frequency in the frequency estimator 11 becomes closer to the reference value by correcting the reference oscillator. It is determined by deciding. The frequency estimator 11 notifies the control unit 20 of the determination result, and the control unit 20 instructs each unit,
Steps 1002 to 1104 are repeated until the variance of the local oscillator estimation error converges within an allowable range. After the control unit 20 determines the convergence, the control of the reference oscillator that follows the fluctuation of the base station is executed at the timings shown in the sections B ′ and C ′ in FIG. 10 (1106). In other words, when the slot synchronization with the base station is established and the steady time-division communication is being performed, the transmission data of the base station is received in the section B ′ and the section C ′ is received.
, The frequency error is estimated, and the oscillation frequency accuracy of the reference oscillator 15 is corrected. Then, the continuation of the communication is determined (11
07) If continued, further increase in frequency error is determined (1108). If the frequency error exceeds a predetermined value, the process returns to step 1102, and the correction is performed in section A '. The frequency error of the second local oscillator is estimated again using the calibration signal generated based on the reference oscillator thus set. If the value is equal to or less than the specified value, the process is repeated from the process 1106, and is executed at the timings shown in the sections B 'and C' as described above. As shown in FIG. 10, assuming that slot S1 in section B ′ is a time slot allocated by the base station, the processing in sections C ′ and A ′ ends in the empty slot periods of slots S2 and S3, and Communication is continued without interruption.

According to the flow shown in FIG. 11, the re-estimation of the second local oscillator 19 is started as required, and the power consumption can be reduced by omitting it in normal times.

According to the present embodiment, since the estimation of the second local oscillator 19 is also executed by the frequency estimator 11 by the calculating means, there is an effect that the automatic frequency control can be started at high speed.
Further, since the number of the counters 9 can be reduced, the size of the circuit can be reduced.

Next, a fifth embodiment of the present invention will be described. FIG. 12 is a configuration diagram showing the configuration of the fifth embodiment.
In FIG. 12, reference numeral 25 denotes a frequency correction unit, and other parts equivalent to those in the fourth embodiment are denoted by the same reference numerals. In this embodiment, the phase compensator 10A is omitted in the fourth embodiment, and the quasi-synchronous output signal output of the quasi-synchronous detector 8 is directly input to the frequency estimator 11 and the second phase compensator 12. The output of the frequency memory 24 is further output to the frequency correction unit 25. The frequency correction unit 25 receives the output value of the frequency memory 24 and the output signal of the frequency estimator 11 and controls the oscillation frequency of the reference oscillator 15. That is, the result of subtracting the output value of the frequency memory 24 from the output of the frequency estimator 11 is controlled as a relative frequency error with respect to the base station oscillator to the reference oscillator 15 so as to minimize the frequency error. It is assumed that the estimated value of the frequency error of the second local oscillator 19 is stored in the frequency memory in the same procedure as in the fourth embodiment. In the present embodiment, the arithmetic processing in the phase compensator 10A is omitted, and low power consumption is achieved.

Next, as a sixth embodiment of the present invention, the fourth embodiment
9 shows a mobile communication device configured by combining the fifth embodiment and the fifth embodiment. FIG. 13 is a configuration diagram of a mobile communication device according to a sixth embodiment, in which parts equivalent to those in the above-described embodiment are denoted by the same reference numerals. This embodiment includes the phase compensation unit 10A of the fourth embodiment, and further includes the frequency correction unit 14B described in the third embodiment. Frequency memory 24
Is connected to the phase compensation unit 10A and the frequency correction unit 14B. The frequency correction unit 14B directly indicates a frequency error resulting from subtracting the output of the frequency memory 24 from the output of the frequency estimator 11 when instructed by the control unit 20, and is directly indicated by the output of the frequency estimator 11 when there is no instruction. The oscillation frequency of the reference oscillator 15 is controlled so as to minimize the frequency error. The estimation of the frequency error of the second local oscillator stored in the frequency memory 24 and the update of the stored value are performed in the same manner as in the fourth embodiment.

The feature of the present embodiment having the above configuration is that the first mode and the second mode are provided for the base station tracking control by the switch 104 (FIG. 9) inside the phase compensator 10A. is there. The first mode is switch 104
, The output of the complex multiplier 103 ′ (FIG. 9) is selected on the side of In ′ and Qn ′, and the frequency estimator 11 uses the result of compensating for the phase rotation due to the frequency error of the second local oscillator 19 to determine It estimates and controls the reference oscillator 15 so as to directly minimize this estimated output. In the second mode, the quasi-synchronous demodulated signal outputs In and Qn are selected by the switch 104, the frequency estimator 11 estimates the signals In and Qn, and the frequency corrector 14B
Controls the reference oscillator 15 so as to minimize the result of subtracting the output of the frequency memory 24 from the output of the frequency estimator 11.

Next, the state transition between these two operation modes will be described. The operation of the automatic frequency control proceeds in the same manner as the operation flow of FIG. 11, and the operation in the first mode is performed until the convergence of the estimation result of the second local oscillator is determined in the processing 1105 of FIG. . Then, after the processing 1106 in FIG. 11, the automatic frequency control in the second mode is performed. Therefore, the transition from the second mode to the first mode is performed by the control unit 20 detecting an increase in the frequency error.

According to the present embodiment, similarly to the third embodiment, the second local oscillator is connected to the second local oscillator via the phase compensator 10A in case the base station deviation of the first local oscillation frequency is large before the automatic frequency control is performed. The frequency error of the quasi-synchronous demodulation signal input to the frequency estimator 11 is suppressed by compensating for the frequency error of the oscillator 19, and the probability of causing an estimation error is reduced.

Further, once the automatic frequency control is performed, the first
After the base station deviation of the local oscillation frequency is reduced, and after the estimated value of the error of the second local oscillator has converged, the processing of the phase compensator 10A is omitted, and the estimation of the error of the second local oscillator 19 and the frequency memory Updating of the stored value of 24 can be stopped, and power consumption can be reduced.

Further, since the estimation of the second local oscillator is performed by arithmetic processing, the same effects as those of the fourth embodiment can be obtained with respect to speeding up the start of the automatic frequency control and reducing the circuit scale.

Next, a seventh embodiment of the present invention will be described.
FIG. 14 is a configuration diagram showing the configuration of the seventh embodiment. FIG.
In the figure, the same reference numerals are given to parts equivalent to those in the first embodiment. Reference numeral 19A denotes a second local oscillator, which can finely adjust the oscillation frequency from outside. 26 and 27 are frequency estimators 11 at the timing instructed by the controller 20.
Is a frequency correction unit that receives the estimated output of the above and outputs an oscillation frequency adjustment control signal so as to minimize the estimated output. The frequency correction unit 26 controls the second local oscillator 19A, and the frequency correction unit 27 controls the reference oscillator 15.

In this embodiment, the oscillation frequency adjusting control signals output from the frequency
Connected to the local oscillator 19A and the reference oscillator 15;
As in the fifth embodiment, the quasi-synchronous demodulation signal output of the quasi-synchronous detector 8 is directly input to the frequency estimator 11 and the phase compensator 12. The frequency correction unit 26 receives the result of estimating the frequency error of the second local oscillator 19A using the calibration signal, and the frequency correction unit 27 receives the result of the estimation by the frequency estimator 11 at the time of reception from the base station. In addition, the control unit 20 controls the input timing of each estimation result.

According to the present embodiment, first, as in the fifth embodiment, the frequency error of the second local oscillator 19A is estimated, and the oscillation frequency of the second local oscillator 19A is It is corrected with the accuracy of. Next, the transmission signal from the base station is received, the reception frequency error is estimated by the frequency estimator 11, and the frequency correction unit 27 controls the reference oscillator 15 so as to minimize the base station deviation.

After the above operation, the reference oscillator 15 and the second local oscillator 19A at the timing of the sections B ', C' and A 'in the time chart of FIG. 10 described in the fourth embodiment.
If the estimation of the error from the above and the correction of the oscillation frequency are performed, the frequency control is performed following the fluctuation of the base station.

According to the present embodiment, prior to the receiving operation,
Since the frequency error of the second local oscillator 19A is adjusted, the frequency error of the quasi-synchronous demodulated signal input to the frequency estimator 11 at the time of base station reception can be reduced, and the probability of causing an estimation error can be reduced.

In another embodiment (not shown), the phase compensator 10 may be omitted from FIG. 1 and the output of the counter 9 may be input to the frequency estimator 11. At this time, the frequency estimator extracts a phase rotation component for each modulation symbol due to a frequency error from the quasi-synchronous demodulation signal, and performs a phase rotation according to the frequency error obtained from the output of the counter 9 with respect to this extraction amount. The frequency estimation operation is performed based on the corrected amount of extraction. According to this embodiment, the same effects as those of the first embodiment can be obtained.

As described above, according to the present invention, in the communication apparatus, the frequency error of the second local oscillator can be estimated with the accuracy of the reference oscillator as the first stage. Therefore, the base station following accuracy of the reference oscillator can be improved by the oscillation frequency adjustment control signal for calibrating the reference oscillator of the communication device based on the oscillation frequency of the base station. When calibrating the reference oscillator, the received frequency is corrected using the frequency error estimated value of the second local oscillator, the correction is performed when the oscillation frequency adjustment control signal is output, or the second local oscillator is directly calibrated. Alternatively, the reference oscillator can be correctly calibrated by using any means.

Since the accuracy of the reference oscillator is improved by the base station tracking operation, the accuracy of estimating the frequency error of the second local oscillator is sequentially improved.

Further, when the transmission frequency is set using the reference oscillator, there is an effect that the accuracy of the transmission frequency can be improved.

[0103]

As described above, according to the present invention, in the communication apparatus, the frequency error of the second local oscillator is estimated with the accuracy of the reference oscillator as the first stage, and the oscillation frequency of the base station is estimated based on the oscillation frequency of the base station. An error of the oscillator can be correctly obtained, and the base station tracking accuracy of the reference oscillator can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a mobile communication device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a quasi-synchronous detector 8;

FIG. 3 is a configuration diagram of a phase compensation unit 10;

FIG. 4 is a configuration diagram of a phase compensation unit 12.

FIG. 5 is a configuration diagram of a mobile communication device according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram of a mobile communication device according to a third embodiment of the present invention.

FIG. 7 is an operation flowchart of an automatic frequency control process according to a third embodiment of the present invention.

FIG. 8 is a configuration diagram of a mobile communication device according to a fourth embodiment of the present invention.

FIG. 9 is a configuration diagram of a phase compensation unit 10A.

FIG. 10 is a time chart of an automatic frequency control process in the fourth embodiment.

FIG. 11 is an operation flowchart of an automatic frequency control process in the fourth embodiment.

FIG. 12 is a configuration diagram of a mobile communication device according to a fifth embodiment of the present invention.

FIG. 13 is a configuration diagram of a mobile communication device according to a sixth embodiment of the present invention.

FIG. 14 is a configuration diagram of a mobile communication device according to a seventh embodiment of the present invention.

FIG. 15 is a time chart of an automatic frequency control process in the first embodiment.

FIG. 16 is a time chart of an automatic frequency control process in the first embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Common transmission / reception antenna, 2 ... Demultiplexer, 3 / 5.7 ... Amplifier, 4 ... 1st intermediate frequency converter, 6 ... 2nd intermediate frequency converter, 8 ... Semi-synchronous detector, 9 ... Counter, 10.10A
12 phase compensator, 11 frequency estimator, 13 decoder, 14 / 14A / 14B / 25/26/27 frequency corrector, 15 reference oscillator, 16 first local oscillator, 1
7: calibration signal generator, 18: coupling capacitor, 19: second local oscillator, 20: control unit, 21: modulator, 22: transmitter.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-37414 (JP, A) JP-A-63-26037 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 1/16-1/26 H03J 7/00-7/18

Claims (8)

(57) [Claims] 1. A first frequency conversion means for mixing a received signal with a first local oscillation signal to convert the received signal into a first intermediate frequency signal, and mixing a second local oscillation signal with the first intermediate frequency signal. A second frequency conversion means for converting the first local transmission signal into a second intermediate frequency signal; and a reference frequency generation means for generating a reference signal serving as a reference for setting a transmission frequency of the first local transmission signal; A calibration signal generating means for outputting a calibration signal of a first intermediate frequency with reference to the reference signal, detecting a frequency error of the reference frequency generating means, and transmitting an oscillation frequency correcting adjustment signal to the reference frequency generating means based on the frequency error The reference frequency generating means can change the frequency of the reference signal by an oscillation frequency correction adjustment signal, and the frequency estimation correcting means A frequency error A between the calibration signal converted to the intermediate frequency and a preset reference intermediate frequency is detected and accumulated, and further, a frequency error B between the received signal converted to the second intermediate frequency and the reference intermediate frequency is calculated. From the frequency error B, the frequency error A
A communication apparatus, which detects a frequency error C corresponding to an error from which the oscillation frequency is removed, and outputs an oscillation frequency correction adjustment signal based on the frequency error C. 2. A first frequency estimator according to claim 1, wherein said frequency estimating and correcting means detects and outputs a frequency error A between a calibration signal converted into a second intermediate frequency and a reference intermediate frequency. A phase compensator that corrects the phase of the received signal converted to a second intermediate frequency based on the frequency error A from the first frequency estimator; and a received signal corrected by the phase compensator. A second frequency estimator for detecting a frequency error C from the reference intermediate frequency and outputting a frequency error signal; and a reference frequency generating means for oscillating frequency correction based on the frequency error signal from the second frequency estimator. A communication device comprising: a frequency correction unit that outputs an adjustment signal. 3. The first frequency estimator according to claim 1, wherein the frequency estimating / correcting means detects and outputs a frequency error A between a calibration signal converted into a second intermediate frequency and a reference intermediate frequency. A second frequency estimator having a function of detecting a frequency error B between a received signal converted into at least a second intermediate frequency and a reference intermediate frequency and outputting a frequency error signal; and a first frequency estimator. And a frequency error C corresponding to a difference obtained by subtracting the frequency error A from the frequency error B based on the frequency error A from the second frequency estimator and the frequency error B from the second frequency estimator. A communication device comprising: a frequency correction unit having a function of outputting a frequency correction adjustment signal. 4. The apparatus according to claim 3, further comprising a phase compensator for correcting a phase of a received signal converted into a second intermediate frequency based on a frequency error A from the first frequency estimator. The second frequency estimator further calculates a frequency error C between the received signal converted to the second intermediate frequency and the reference intermediate frequency.
And a function to output a frequency error signal by detecting the frequency error signal, and wherein the frequency correction means outputs an oscillation frequency correction adjustment signal to a reference frequency generation means based on the detection of the frequency error signal. . 5. The phase compensation unit according to claim 4,
It is possible to switch between a mode for correcting the phase of the received signal converted to the second intermediate frequency and a mode for outputting the received signal without correction, wherein the frequency correction unit adjusts the phase corresponding to the mode. When performing the correction, the communication device detects the frequency error C and outputs an oscillation frequency correction adjustment signal to a reference frequency generating means. 6. The frequency estimator according to claim 1, wherein the frequency estimator corrects the frequency error A between a calibration signal converted to a second intermediate frequency and a reference intermediate frequency. A frequency memory for accumulating, and a frequency correcting means for outputting an adjustment signal for oscillating frequency correction to a reference frequency generating means, wherein the frequency estimator comprises at least a received signal converted to a second intermediate frequency and a reference intermediate frequency. A frequency error signal output from the frequency estimator from the frequency error B output from the frequency estimator. A communication device for outputting an oscillation frequency correction adjustment signal based on a frequency error C corresponding to a difference obtained by subtracting the following. 7. The frequency estimator according to claim 6, further comprising: a phase compensator for correcting a phase of a received signal converted into a second intermediate frequency based on a frequency error A from the frequency memory. The apparatus further has a function of detecting a frequency error C between the received signal converted into the second intermediate frequency and the reference intermediate frequency and outputting a frequency error signal, wherein the frequency correction unit is configured to output the frequency error signal based on the frequency error signal. And outputting an oscillation frequency correction adjustment signal to a reference frequency generating means. 8. The phase compensation unit according to claim 7, wherein
It is possible to switch between a mode for correcting the phase of the received signal converted to the second intermediate frequency and a mode for outputting the received signal without correction, wherein the frequency correction unit adjusts the phase corresponding to the mode. When performing the correction, the communication device detects the frequency error C and outputs an oscillation frequency correction adjustment signal to a reference frequency generating means.