JPH09326752A - Mobile communication terminal equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize frequency resources by selecting a long term frequency deviation of a temperature compensation crystal oscillator(TCXO) to be 1.0ppm or below so as to facilitate a narrow frequency band of a radio channel. SOLUTION: A 2nd intermediate frequency section obtained by receiving a radio wave sent from a base station and a TCXO frequency signal outputted from a TCXO 6 are frequency-divided by a designated frequency division rate, the frequencies and the phases are compared, and when the frequency oscillated by the TCXO 6 is deviated from a frequency of the frequency signal generated by an oscillation circuit of the base station side, it is detected and a correction signal required to make the frequency oscillated from the TCXO 6 corresponding to the frequency of the frequency signal generated by the oscillation circuit at the base station side is generated and it is fed to the TCXO 6 so as to correct the oscillated frequency from the TCXO 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication terminal device, and more particularly to a mobile communication terminal device provided with an AFC circuit for synchronizing an oscillator output of its own station with a transmission signal from a base station.

[0002]

2. Description of the Related Art In mobile communication systems currently in practical use, in order to effectively use finite frequency resources,
The narrowing of the bandwidth of wireless channels is being promoted. For this reason,
In such a mobile communication system, a temperature-compensated crystal oscillator having high frequency stability (hereinafter, abbreviated as TCXO) is generally used. However, even with such a TCXO, it is 1.0
The frequency deviation is limited to the order of ppm, and if the demand exceeds it, an oven type TCXO is required, and it is difficult to reduce the size. At the same time, it is impossible to reduce the power consumption.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. Even if an oscillator having a simple structure is used for a long period of time, a frequency deviation of, for example, 1.0 p
It is an object of the present invention to provide a mobile communication terminal device provided with an AFC circuit that can be set to pm or less.

[0004]

In order to achieve the above object, a mobile communication system according to the present invention operates a TCXO to generate various frequency signals necessary for transmission and reception, and inputs the frequency signals. An oscillating section for operating the AFC circuit based on the reference frequency signal on the base station side and the frequency signal to adjust the oscillation frequency of the TCXO;
A transmission signal generation unit that generates a carrier signal of a specified channel based on the frequency signal obtained by the oscillating unit and that modulates the carrier signal with an input modulation signal to generate a transmission signal; An antenna unit that converts the transmission signal generated by the signal generation unit into an electric wave and transmits the electric wave, and also receives the electric wave transmitted from the base station side to generate a reception signal, and a frequency signal obtained by the oscillation unit. Based on
A reception signal processing unit that processes the reception signal generated by the antenna unit to generate a demodulation signal obtained by demodulating the reception signal, reproduces a reference frequency signal on the base station side, and inputs this to the oscillating unit. It is characterized by having and. In order to achieve the above-mentioned object, A according to the present invention
The FC circuit takes in a reference frequency signal and a frequency signal to be calibrated, compares the frequencies and phases of these frequency signals, and generates a UP pulse signal and a DOWN pulse signal according to the comparison result. A phase comparator, a sequential loop filter that divides the UP pulse signal and the DOWN pulse signal output from the frequency / phase comparator and low-pass filters them to generate an increment signal and a decrement signal, and this sequential loop filter. And an up-down counter circuit for adjusting the frequency of the frequency signal to be calibrated by performing up-counting operation and down-counting operation to generate correction data based on the increment signal and the decrement signal output from the loop filter. Is characterized by.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail with reference to the embodiments shown in the drawings. FIG. 1 is a block diagram showing an embodiment of a mobile communication terminal device using an AFC circuit according to the present invention. A mobile communication terminal device 1 shown in this figure has an oscillating section 2 for generating various frequency signals necessary for transmission / reception, a frequency signal obtained by the oscillating section 2 and a first local oscillating frequency signal. A transmission signal generation unit 3 that generates a carrier signal of a designated channel based on the modulation signal and that modulates the carrier signal with an input modulation signal to generate a transmission signal, and a signal generated by the transmission signal generation unit 3. And an antenna unit 4 for receiving the radio wave transmitted from the base station side, and a received signal is demodulated based on the first local oscillation frequency signal and the second local oscillation frequency signal obtained by the oscillation unit 2. In addition, the receiver 5 is provided with a part of the demodulated signal to the oscillator 2. Although the basic operation of transmission and reception in this configuration is well known, it is not different from the conventional device, but the characteristic point of this device is that the radio wave of the channel specified by the base station side is transmitted. It has a function of receiving and demodulating, and correcting the oscillation frequency of the oscillator 2 based on the second intermediate frequency signal so as to match the frequency of the frequency signal on the base station side. The oscillating unit 2 uses, for example, a reference frequency signal (TCX) of 12.8 MHz.
TCXO6 for generating an O frequency signal) and 788-81
Of the 5 MHz frequency signal, a PLL synthesizer circuit 7 for generating a first local oscillation frequency signal of a designated channel frequency, a bandpass filter circuit 8 for bandpass filtering, and a frequency synthesizer system 10
A PLL synthesizer circuit 9 for generating a second local oscillation frequency signal having a frequency of 9.9 MHz, a TCXO frequency signal output from the TCXO 6 and a second intermediate frequency signal having a frequency of 50 KHz output from the receiving unit 5. And an AFC circuit (automatic frequency control circuit) 10 for generating an oscillation frequency control signal (correction signal) based on the comparison result and controlling the oscillation frequency of the TCXO 6. The AFC used in this oscillator 2
The circuit 10 will be described in detail later.

Further, the transmission signal generating section 3 includes the oscillating section 2
The frequency of the TCXO frequency signal output from the
A PLL synthesizer circuit 11 that generates a frequency signal of Hz and modulates the frequency signal by an input modulation signal to generate a transmission signal, and a first local oscillation output from the transmission signal and the oscillation unit 2. A mixing circuit 12 for synthesizing a frequency signal to generate a transmission signal of a designated channel frequency, an amplification circuit 13 for amplifying the mixing output signal, and a bandpass filter circuit 14.
And a power amplifier circuit 15. The antenna unit 4 transmits the signal to the antenna 16 and the transmission signal output from the transmission signal generation unit 3 to the antenna 16, and also guides the reception signal of the radio wave received by the antenna 16 to the reception unit 5. The shared device 17 is provided. The receiver 5 includes an amplifier circuit 18 that amplifies a received signal output from the antenna unit 4, a bandpass filter circuit 19 that extracts a received signal of each channel, and the received signal and the oscillator 2 output the received signal. A mixing circuit 20 that synthesizes the first local oscillation frequency signal to generate an intermediate frequency signal of 55 MHz, a bandpass filter circuit 21 that passes only this intermediate frequency signal, and an amplifier circuit 22 that amplifies this intermediate frequency signal. An intermediate frequency signal processing circuit (IF-IC) 23 that generates a demodulated signal and divides the intermediate frequency signal to generate a second intermediate frequency signal having a frequency of 50 KHz.

Next, the above-mentioned AFC circuit 10 will be described in detail with reference to the block diagram shown in FIG. As shown in the figure, the AFC circuit 10 includes an amplifier circuit (RX-AMP) 24 for amplifying the second intermediate frequency signal output from the intermediate frequency signal processing circuit 23, and a second output circuit from the amplifier circuit 24. An RX counter circuit 25 that divides the intermediate frequency signal and a TCXO counter circuit 2 that divides the TCXO frequency signal and converts it into a TCXO frequency signal having a frequency corresponding to the second intermediate frequency signal.
6 and the signal output from the TCXO counter circuit 26, the reference pulse necessary for binarizing (+1: UP, -1: DOWN) the magnitude of the frequency, the delay of the phase, and the advance is generated. Down pulse generation gate circuit 27
And comparing the frequency and phase of the second intermediate frequency signal output from the RX counter circuit 25 with the frequency and phase of the TCXO frequency signal output from the TCXO counter circuit 26 based on this reference pulse. ,
A frequency / phase comparison circuit 28 is provided which determines the magnitude of the frequency, the delay or advance of the phase, binarizes the determination result, and loop-filters to generate an increment signal or a decrement signal.

Further, the AFC circuit 10 is a 6-bit up / down counter circuit which counts up each time an increment signal is output from the frequency / phase comparison circuit 28 and counts down each time a decrement signal is output. 29 and the count result (correction data) output from the up / down counter circuit 29
Based on a 6-bit D / A conversion circuit (digital / analog conversion circuit) 30 for A-converting to generate a correction signal, and an increment signal and a decrement signal output from the frequency / phase comparison circuit 28, the TCXO 6 When the oscillation frequency corresponds to the frequency of the frequency signal generated by the oscillation circuit on the base station side (when in a synchronized state), a lock detection circuit 31 for detecting this is provided.

The intermediate frequency signal processing circuit 23
The second intermediate frequency signal output from the TCXO6
The TCXO frequency signal output from the TCXO6 is divided by a specified frequency division ratio, the frequency and phase of the second intermediate frequency signal are compared with the frequency and phase of the TCXO frequency signal, and the oscillation frequency of the TCXO6 is based on the base frequency. When the frequency is deviated from the frequency of the signal transmitted from the station side, a correction signal necessary for making the oscillation frequency of the TCXO6 correspond to the frequency of the frequency signal generated by the oscillation circuit of the base station side is generated,
Correct the oscillation frequency of TCXO6. Also, the TCX
When the oscillation frequency of O6 matches or corresponds to the signal frequency generated by the oscillation circuit on the base station side, the lock detection signal is generated.

The frequency / phase comparison circuit 28
A phase comparator 32 and a 1 / N counter circuit for generating an increment signal by dividing the UP pulse signal output from the frequency / phase comparator 32 as shown in FIG. 3 by a preset division ratio N. 34, the frequency / phase comparator 3
1 generates a decrement signal by dividing the DOWN pulse signal output from 2 by a preset dividing ratio N
/ N counter circuit 35 and a sequential loop filter 33 configured by a reset circuit 36 that generates a counter reset signal based on the increment signal or the decrement signal output from each of the 1 / N counter circuits 34, 35. There is. And the R
The frequency and phase of the second intermediate frequency signal output from the X counter circuit 25 and the frequency and phase of the TCXO frequency signal output from the TCXO counter circuit 26 are compared to determine the magnitude of the frequency, the phase delay, and the lead. After judging and binarizing this judgment result, the response speed of AFC,
The binarization result is loop-filtered to generate an increment signal or a decrement signal with a filtering characteristic sufficient to compensate for an excessive phase lead and an excessive phase delay, and at the same time, to generate a counter reset signal. The up / down counter circuit 29 is reset.

Further, the increment signal or the decrement signal is supplied to an up / down counter circuit 29 for up-counting or down-counting, and the increment signal or the decrement signal is supplied to a lock detecting circuit 31 for lock detection. To perform. At this time, when N of the UP pulse signal or the DOWN pulse signal is output from the frequency / phase comparator 32, a sequential loop filter is provided to cause the up / down counter circuit 29 to output an increment signal or a decrement signal. The value shown in the following equation is used as the frequency division ratio N of 33. N = 1 / [{ft / M} · {fv / fr}] (1) where ft: variable frequency range [ppm] of TCXO6 M: resolution of D / A conversion circuit 30 [quantization number] fv: A value obtained by dividing the first local oscillation frequency by 10 6 [Hz] fr: Frequency of the second intermediate frequency signal corresponding to the received signal [KHz] Here, using the numerical value shown in the following equation, ft: 16 [ ppm] M: 64 [quantization number] fv: 801 [Hz] fr: 50 [KHz] When the frequency division ratio N of the sequential loop filter 33 represented by the above formula (1) is calculated, N = 1 / {(16 /64).(801/50000)}=250 is obtained.

Therefore, if the frequency division ratio N of the sequential loop filter 33 is set to "250", the TCX is generated based on the frequency signal generated by the oscillator circuit on the base station side.
The oscillation frequency of O6 can be phase-corrected. As a result, in the AFC circuit 10, when the frequency of the TCXO frequency signal output from the TCXO 6 is lower than the frequency of the frequency signal generated by the oscillator circuit on the base station side, the count value of the up / down counter circuit 29 is incremented, In the opposite case, it is decremented and this is converted into a correction signal by the D / A conversion circuit 30 to adjust the oscillation frequency of the TCXO 6. At this time, 3V is applied as a power supply voltage to the D / A conversion circuit 30, and the initial value of the up / down counter circuit 29 is "011111" in binary format.
If "B" is set, the frequency / phase comparison circuit 2
When 16 or more increment signals are continuously output from 8, the count result of the up / down counter circuit 29 becomes “111111B”, and the D / A conversion circuit 30
Output a correction signal of about 3 V from the output of the TCXO6 to the maximum, and when the frequency / phase comparison circuit 28 continuously outputs 15 or more decrement signals, the up / down counter circuit 29 Count result becomes "000000B", and the D / A conversion circuit 2
A correction signal of 0V is output from 9 and the oscillation frequency of the TCXO 6 is adjusted to the minimum.

Further, the lock detection circuit 31 is reset each time a decrement signal is output from the sequential loop filter 33 of the frequency / phase comparison circuit 28 as shown in FIG. 4, and an increment signal is output from the sequential loop filter 33. Every time is output, the N-stage shift register circuit 3 that takes in and shifts
7 and an N-stage shift register circuit 38, which is reset each time an increment signal is output from the sequential loop filter 33 and is reset each time a decrement signal is output from the sequential loop filter 33, and which shifts by fetching the decrement signal. A lock detection signal generation circuit 39 for generating a lock detection signal when the shifted increment signal or decrement signal is not output from each of the shift register circuits 37 and 38.

As when the decrement signal or increment signal is not output from the sequential loop filter 33 of the frequency / phase comparison circuit 28,
The frequency and phase of the frequency signal generated by the oscillator circuit on the base station side and the frequency and phase of the TCXO frequency signal output from the TCXO 6 completely match, and the count result output from the up / down counter circuit 29. When there is no change or the frequency / phase comparison circuit 2
8 when the sequential loop filter 33 does not output N decrement signals in succession, or when the sequential loop filter 33 does not output N increment signals in succession. Frequency and phase of the frequency signal generated by the oscillating circuit, and the TCX output from the TCXO6.
Even when the frequency and phase of the O frequency signal do not completely match, the count result output from the up / down counter circuit 29 increases / decreases alternately, and when in the synchronous acquisition state, the AFC circuit 10 locks. A lock detection signal indicating that there is a lock is generated and output.

As described above, in this embodiment, the AFC circuit 10 is provided on the mobile communication terminal apparatus 1 side to receive the radio wave transmitted from the base station side, and the second intermediate obtained by this receiving operation. The frequency and phase of the frequency signal and the TCXO
When the frequency and phase of the TCXO frequency signal obtained in 6 are compared, and the oscillation frequency of the TCXO 6 deviates from the frequency of the frequency signal generated by the oscillator circuit on the base station side based on the comparison result, When this is detected, the T
A correction signal necessary for making the oscillation frequency of the CXO6 correspond to the frequency of the frequency signal generated by the oscillation circuit on the base station side is supplied to the TCXO6, and the TCXO6 is supplied with the correction signal.
Since the oscillation frequency of the XO6 is corrected, it is possible to reduce the frequency deviation of the TCXO6 over a long period of time, thereby facilitating the narrowing of the radio channel band and promoting the effective use of frequency resources. You can

Further, in this embodiment, the AFC circuit 10 outputs the second intermediate frequency signal output from the intermediate frequency signal processing circuit 23 and the T output from the TCXO 6.
The CXO frequency signal is taken in, these are divided by a specified division ratio, and the frequency and phase of the divided second intermediate frequency signal are compared with the frequency and phase of the divided TCXO frequency signal. When the oscillation frequency of the TCXO6 deviates from the frequency of the frequency signal generated by the oscillation circuit on the base station side, this is detected and the oscillation frequency of the TCXO6 is generated by the oscillation circuit on the base station side. Since the correction signal necessary to correspond to the frequency of the frequency signal is generated and is supplied to the TCXO6 to correct the oscillation frequency of the TCXO6, the TCXO6 is
Even if you don't use a highly accurate TCXO,
The frequency deviation of the TCXO6 can be set to 1.0 ppm or less, for example. Further, in this embodiment, since the entire AFC circuit 10 is configured by a digital circuit, the entire AFC circuit 10 can be easily made into an ASIC (a plurality of semiconductor chips can be made into one chip) and an inexpensive gate array can be obtained. Etc., the circuit can be designed and manufactured, and the cost of the entire mobile communication terminal device 1 can be reduced. Further, in the above-described embodiments, the AFC circuit according to the present invention has been described by taking the mobile communication terminal device 1 as an example. However, in the system other than the mobile communication terminal device 1 described above, the AFC circuit according to the present invention is used. May be applied.

[0017]

As described above, according to the present invention, the frequency deviation of the TCXO can be reduced over a long period of time, thereby facilitating the narrowing of the radio channel band and effectively utilizing the frequency resources. Can be promoted.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an AFC circuit and a mobile communication terminal device according to the present invention.

FIG. 2 is a block diagram showing a detailed circuit configuration example of the AFC circuit shown in FIG.

FIG. 3 is a block diagram showing a detailed circuit configuration example of a sequential loop filter used in the frequency / phase comparison circuit shown in FIG.

4 is a block diagram showing a detailed circuit configuration example of a lock detection circuit used in the frequency / phase comparison circuit shown in FIG.

[Explanation of symbols]

1 mobile communication terminal device, 2 oscillating unit, 3 transmission signal generating unit, 4 antenna unit, 5 receiving unit, 6 T
CXO, 10 AFC circuit, 24 amplifier circuit, 2
5 RX counter circuit, 26 TCXO counter circuit, 27 up-down pulse generation gate circuit, 2
8 frequency / phase comparison circuit, 29 up / down counter circuit, 30 D / A conversion circuit, 31 lock detection circuit, 32 frequency / phase comparator, 33 sequential loop filter

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[Procedure amendment]

[Submission date] September 20, 1996

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

Claims (1)

[Claims] 1. An oscillating unit having an AFC circuit for matching an oscillator output frequency of its own station with a received reference frequency signal on the base station side, and a carrier of a designated channel based on the frequency signal obtained by the oscillating unit. A transmission signal generation unit that generates a signal and that modulates the carrier signal with an input modulation signal to generate a transmission signal, and demodulates a reception signal based on the frequency signal obtained by the oscillation unit, and outputs the signal. In a mobile communication terminal device, comprising: a reception signal processing unit for inputting a part of the signal to the oscillation unit; and the AFC circuit that takes in a reference frequency signal and a calibration target frequency signal, A frequency / phase comparator that compares the frequency and phase of a frequency signal and generates an UP pulse signal and a DOWN pulse signal according to the comparison result, and this frequency / phase comparison The UP pulse signal and the DOWN pulse signal output from each are divided into a sequential loop filter that generates an increment signal and a decrement signal by low-pass filtering, and an increment signal and a decrement signal output from the sequential loop filter. A mobile communication terminal device, comprising: an up-down counter circuit that performs an up-counting operation and a down-counting operation to generate correction data and adjusts the frequency of a frequency signal to be calibrated.