JPH07288445A - Radio equipment of afc system - Google Patents

Abstract

PURPOSE:To improve frequency stability and frequency accuracy, shortening waiting time form the turning ON of a power source to the start of use, by inputting a detected temperature and controlling a reference frequency based on a corresponding control frequency at the time of starting AFC. CONSTITUTION:First of all, a reference frequency oscillator 103 starts operating from a default value. At such a time, when a pilot signal can be properly received and a synchronizing signal is transmitted from a frequency comparator 105 to an AFC controller 106, the controller 106 locks the control frequency corresponding to the oscillator 103. Then, the temperature at that time is inputted from a temperature detection sensor 107 inside the oscillator 103, and the locked control frequency and the detected temperature are recorded in a memory 108. On the other hand, when the signal can not be properly received, the comparator 105 transmits an asynchronizing signal to the controller 106 and starts searching. When the frequency is matched by the search of the controller 106, the signal is properly received and when the comparator 105 transmits the synchronizing signal to the controller 106, the controller 106 immediately stops searching and continues reception.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to radio equipment such as radio receivers and mobile phones, and more particularly to AFC type radio equipment in narrow band communication systems such as TONE IN BAND.

[0002]

2. Description of the Related Art It is important for a radio of a narrow band communication system such as TONE IN BAND that the frequency of transmission and reception is accurate, and the stability of this frequency is sometimes a value required by the Radio Law. In some cases, stability in excess of 10 is desired. For example, in the 220 MHz band in the United States, the Radio Law (FCC) is ± 1.5 ppm (about ±
350Hz) stability is required, but in practice,
As will be described later, good communication cannot be performed unless the frequency is within ± 50 Hz to ± 100 Hz, so that the frequency stability is required to be stricter than specified by the Radio Law.

FIG. 10 shows a range of frequency stability required in the TONE IN BAND system (± 50 Hz to
It is an explanatory view showing ± 100Hz or less). TONE
In the IN BAND method, in order to cope with frequency shift and high-speed fluctuation of amplitude due to Rayleigh fading, these effects are taken by using TONE (hereinafter, referred to as pilot signal) inserted in the center of BAND (band) as a reference signal. Signal processing to remove the signal. That is, since the pilot signal of a constant value inserted in the center of the band is considered to be affected by Rayleigh fading just like voice, the process of restoring the voice signal is performed with this as a reference. .

However, since the narrow band communication is used in the first place, the pilot signal and the voice inserted in the band (narrow band) are separated by only a few hundred Hz. Therefore, the pilot filter that separates the voice and pilot signals is
It becomes a band of about ± 100 Hz. Therefore,
If the frequency deviation is 100 Hz or more, the communication quality may be deteriorated or communication may be disabled due to the fact that the pilot signal cannot be accurately received or the pilot signal contains a voice component. .

For the above reason, TONE IN B
In the AND method, frequency stability within ± 50 Hz to ± 100 Hz is required.

To obtain such frequency stability, OV
This can be realized by adopting an EN-type crystal oscillator or a reference oscillator using the latest digital technology (hereinafter referred to as digital TCXO).

Further, the frequency deviation of the radio wave transmitted from the base station is generally stricter than that of the mobile station, and is ± 0.1 ppm in the 220 MHz band of the United States mentioned above. Therefore, it is a commonly used method to apply AFC using the radio wave transmitted from the base station as a reference frequency.

On the other hand, in mobile communication, a pilot signal is used as a reference signal for demodulation of reception or to reduce fading. In the conventional radio receiver, the level of the pilot signal is measured, the presence or absence of the received signal is determined, and the squelch is opened / closed to output only the necessary audio signal and output unnecessary noise. I try to prevent it.

[0009]

However, according to the radio device using the above-mentioned conventional OVEN type crystal oscillator, since it takes time for the crystal oscillator to stabilize when the power is turned on, it can be actually used after the power is turned on. There was a problem that it took some waiting time.

Further, according to the above-mentioned conventional radio using the digital TCXO, there is a problem that the cost of the apparatus increases because the digital TCXO is expensive.

Further, in the conventional radio, deviation due to initial adjustment error, deviation due to temperature characteristic, deviation due to aging of crystal oscillator, deviation caused due to aging of oscillation circuit parts, direct current for oscillation circuit and AFC circuit Since there are various factors of frequency deviation such as deviation due to temperature characteristics of the stabilized power supply, satisfactory frequency stability and frequency accuracy can be obtained even when using an OVEN crystal oscillator or a digital TCXO. There was a problem that it was not always.

Particularly, the frequency deviation due to the deviation due to the temperature characteristic is remarkable, and even if the digital TCXO which is considered to have the most frequency stability and frequency accuracy in the past is used, it is highly accurate in the range of -30 ° C to + 75 ° C. To get
It was quite difficult.

On the other hand, according to the conventional AFC type wireless device, in narrow band communication such as TONE IN BAND, communication cannot be performed with a slight frequency deviation, so that a countermeasure such as searching for the maximum expected frequency deviation is taken. If I didn't do it, I couldn't get AFC. Further, in the field of view of the service area where the radio wave is very weak, it is more difficult to accurately capture the radio wave from the base station. For this reason, there is a problem in that after the mobile station is powered on, a search is performed to receive radio waves from the base station and AFC is applied. In other words, there is a problem that a certain waiting time is required from when the mobile station is turned on to when it is actually used.

Further, in the conventional radio equipment, since the level of the pilot signal is measured, the presence or absence of the received signal is judged, and the squelch is opened / closed, the pilot of low power is used in the reception of the weak electric field. The problem that it is difficult to accurately distinguish between signal and noise,
There is a problem that squelch malfunction occurs in a place with a high noise floor or in a weak electric field. Furthermore, since variations in sensitivity occur during manufacturing due to differences between radios, the thresholds used when determining squelch must also be set for each radio, which causes a problem of increased cost. there were.

Similarly, in the conventional AFC type wireless device, the level of the pilot signal is measured to determine whether or not it is a pilot signal, but when receiving a weak electric field, the power is low. Since it is difficult to accurately distinguish the pilot signal from the noise, there is a problem that an error occurs in the measurement of the frequency of the pilot signal and a malfunction occurs in the AFC.

The present invention has been made in view of the above, and aims to improve the frequency stability and the frequency accuracy without shortening the waiting time from the power-on to the start of use and increasing the device cost. The purpose is to

Further, the present invention has been made in view of the above, and it is an object of the present invention to absorb frequency deviation due to various factors and perform stable AFC in a short time.

The present invention has been made in view of the above, and an object of the present invention is to accurately distinguish a pilot signal and noise even in a place where a weak electric field and a noise floor are high.

Further, the present invention has been made in view of the above, and has a small malfunction even when receiving a weak electric field.
The purpose is to be able to perform FC.

[0020]

In order to achieve the above object, the present invention provides an AFC type radio according to claim 1,
A local oscillator that oscillates a local frequency for use in generating an IF signal, a reference frequency oscillator that outputs a reference frequency for controlling the local frequency of the local oscillator, and a reception input signal that receives a reception input signal from an antenna A heterodyne type receiver that mixes frequencies from the local oscillator and outputs an IF signal, and detects a pilot signal from the IF signal, and outputs a synchronization signal or an asynchronous signal based on the presence or absence of the pilot signal And a AFC for locking or changing the reference frequency of the reference frequency oscillator based on the output of the frequency comparator.
In an AFC radio with a controller,
A temperature detection sensor for detecting the temperature of the reference frequency oscillator, and a memory for storing the control frequency of the AFC controller and the detection temperature of the temperature detection sensor are provided. When the detected temperature is input from the detection sensor, the corresponding control frequency is read from the memory, the reference frequency of the reference frequency oscillator is controlled based on the control frequency, and the synchronization signal is input from the frequency comparator. , The temperature detected by the temperature detection sensor and A
The control frequency for the reference frequency oscillator of the FC controller is stored in the memory.

In the AFC type wireless device according to a second aspect of the present invention, when the magnitude of the pilot signal detected by the frequency comparator is smaller than a predetermined value, the AFC controller detects the temperature detected by the temperature detection sensor and AF
The control frequency for the reference frequency oscillator of the C controller is not stored in the memory.

Further, in the AFC type radio device according to the third aspect, even if the AFC controller attempts AFC a predetermined number of times at the control frequency, if the synchronization signal is not input from the frequency comparator, The search is started around the control frequency.

In the AFC type wireless device according to claim 4, the AFC controller inputs the detected temperature from the temperature detecting sensor, reads the corresponding control frequency from the memory, and starts AFC. When the corresponding detected temperature is not stored in the memory, the search is started centering on the control frequency of the closest temperature.

Further, in the AFC type wireless device according to a fifth aspect, the frequency comparator inputs a pilot filter which is a rough filter of a pilot signal and a signal which has passed through the pilot filter, and within a predetermined time. A zero-crossing counting circuit for counting the number of zero-crossings and a squelch circuit for controlling open / close of the squelch based on the count value of the zero-crossing counting circuit are provided.

In the AFC type radio according to the present invention, the frequency comparator inputs a pilot filter which is a rough filter of the pilot signal and a signal which has passed through the pilot filter, and the A zero-crossing counting circuit for counting the number of zero-crossings, a judging circuit for judging whether or not the frequency of the pilot signal captured by the pilot filter is correct based on the count value of the zero-crossing counting circuit, and the judging circuit. In the case where the frequency of the pilot signal is determined to be correct, the sub-audio data is decoded, and when it is decoded correctly, a synchronization circuit that outputs a synchronization signal to the AFC controller is provided. is there.

[0026]

The AFC type wireless device (claim 1) of the present invention is
When the AFC controller starts AFC, power is turned on by inputting the detected temperature from the temperature detection sensor, reading the corresponding control frequency from the memory, and controlling the reference frequency of the reference frequency oscillator based on the control frequency. Waiting time from start to use is shortened, and frequency stability and frequency accuracy are improved. Also, when the synchronization signal is input from the frequency comparator, by storing the detected temperature of the temperature detection sensor and the control frequency for the reference frequency oscillator of the AFC controller in the memory,
As the wireless device is used, information necessary for AFC is self-learned by accumulating and updating, and frequency deviation due to various factors is absorbed.

Also, in the AFC type wireless device (claim 2) of the present invention, when the magnitude of the pilot signal detected by the frequency comparator is smaller than a predetermined value, the AFC controller detects the temperature detected by the temperature detecting sensor and By not storing the control frequency for the reference frequency oscillator of the AFC controller in the memory, only reliable information is stored in the memory.

Further, in the AFC type radio device of the present invention (claim 3), even if the AFC controller attempts AFC a predetermined number of times at the control frequency, if the synchronization signal is not input from the frequency comparator, By starting the search centered on the control frequency, A
FC and self-learning are done.

In the AFC type wireless device of the present invention (claim 4), the AFC controller inputs the detected temperature from the temperature detecting sensor, reads the corresponding control frequency from the memory, and starts AFC. When the corresponding detected temperature is not stored in the memory, the search is started centering on the control frequency of the closest temperature, so that the AFC is efficiently performed even at the temperature that is not stored in the memory.

Further, the AFC type wireless device of the present invention (claim 5) inputs the signal passed through the pilot filter, counts the number of zero crossings within a fixed time, and based on the counted value, By controlling the open / close of the squelch, the pilot signal and the noise can be distinguished even when the level of the pilot signal and the noise level are close to each other.

Further, the AFC type radio device of the present invention (claim 6) inputs the signal which has passed through the pilot filter, counts the number of zero crossings within a fixed time, and based on the count value, Determine whether the frequency of the pilot signal captured by the pilot filter is correct, and if it is determined to be correct, further decode the sub audio data, and if it can be decoded correctly, synchronize with the AFC controller. By outputting a signal,
The malfunction of AFC at the time of a weak electric field is reduced.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An AFC type wireless device of the present invention will be described in detail below in the order of [Embodiment 1] and [Second Embodiment] with reference to the drawings.

[Embodiment 1] FIG. 1 is a schematic configuration diagram of an AFC type radio according to a first embodiment. An antenna 101 that receives a radio wave transmitted from a base station (not shown), a local oscillator 102 that oscillates a local frequency used to generate an IF signal, and a reference frequency that controls the local frequency of the local oscillator 102. Reference frequency oscillator 103 for outputting
And a radio wave (hereinafter, referred to as an RF signal) received by the antenna 101, and the local oscillator 102 is input to the received input signal.
Of the heterodyne type that mixes the local frequencies from the IF signal and outputs the IF signal, and frequency comparison that detects the pilot signal from the IF signal and outputs the synchronization signal or the asynchronous signal based on the presence or absence of the pilot signal Bowl 1
05, an AFC controller 106 that locks or changes the reference frequency of the reference frequency oscillator 103 based on the output of the frequency comparator 105, and the reference frequency oscillator 10.
Temperature detection sensor 107 for detecting the temperature of 3 and AFC
A memory 108 for storing the control frequency of the controller 106 and the temperature detected by the temperature detection sensor 107;
And RSSI 109.

In the first embodiment, the reference frequency oscillator 1
It is assumed that TCXO satisfying the Radio Law is used as 03. Further, in the figure, only the receiving unit, which is the main part of the present invention, is shown, but it is assumed that a general transmitting unit is provided.

FIG. 2 shows a specific configuration of the receiver 104 and the frequency comparator 105. Here, the receiver 104
Shows an example of the triple superheterodyne system, in which an RF amplifier 201 for amplifying an RF signal (220 MHz) from the antenna 101 and a local oscillator 102
A first mixer 202 that inputs a local frequency of 75 MHz and mixes it with an RF signal, an amplifier 203 that amplifies a first IF signal (45.455 MHz) output from the first mixer 202, and a local oscillator of 45 MHz from a local oscillator 102. The second that inputs the frequency and mixes it with the amplified first IF signal
The mixer 204, the local frequency of 450 KHz from the local oscillator 102 are input, the third mixer 205 that mixes with the second IF signal output from the second mixer 204, and the third IF signal output from the third mixer 205 are amplified. And an amplifier 206 that operates. Finally, the amplifier 206
The 3rd IF signal output from is 5 KHz.

Further, the frequency comparator 105 is the receiver 10
An A / D converter 207 that inputs a third IF signal (analog signal) from 4 and performs analog / digital conversion,
Channel filter 208 with pass band of ± 2 KHz
And a pilot filter 209 which is a narrow band filter of about ± 100 Hz for extracting the pilot signal.
Based on the pilot power sensor 210 for measuring the power of the pilot signal, the demodulation circuit 211 for demodulating the signal, and the power level (power) of the pilot signal measured by the pilot power sensor 210, the squelch gate 213 described later is opened / opened. A squelch driver amplifier 212 to be closed, a squelch gate 213 for prohibiting the output of an audio signal when the pilot signal becomes extremely weak, or a weak electric field, and an audio filter 214 for extracting the audio signal. A D / A converter 215 for converting an audio signal (here, a digital signal) into an analog signal, a sub audio filter 216 for extracting sub audio data, and a demodulation circuit for demodulating the sub audio data. And 217, and enter the sub-audio data after demodulation, sub audio data and a CPU218 as an encoder and decoder for determining whether correctly received. The CPU 218
Sends a synchronization (lock) signal to the AFC controller 106 when the sub audio data is correctly received.
Output to.

In the above configuration, the general operation of AFC (automatic frequency control), the features of the AFC operation of the present invention,
A specific example of the detected temperature and the number of AFC steps stored in the memory, and the operation of outputting the synchronization signal by the frequency comparator will be described in this order.

General Operation of AFC (Automatic Frequency Control) First, the general operation of AFC will be described. When the frequency comparator 105 cannot receive the pilot signal from the base station, the frequency comparator 105 outputs the asynchronous signal (unlock signal) to the AFC.
Output to the controller 106. AFC controller 1
When inputting the asynchronous signal, 06 starts the search. Here, the search means finely adjusting the reference frequency oscillator 103 in a predetermined step, variable range, and variable speed. Fine tuning the reference frequency oscillator 103, ie, fine tuning the local oscillator 102.

The search step, the variable range, and the variable speed are values that have been appropriately determined in advance, and therefore, the conditions for good reception are provided. In particular, in the present invention, as will be described later, the search is started using the steps (that is, corresponding to the control frequency) stored in the memory 108 by self-learning.

After that, if the frequency comparator 105 captures the pilot signal from the base station and determines that the frequency deviation is within the allowable range, it is determined whether or not the sub audio data is correctly received. If received correctly, the frequency comparator 105 outputs a synchronization signal (lock signal) to the AFC controller 106. If the sub audio data is not correctly received, the captured pilot signal is erroneous, and the search is continued again to capture the correct pilot signal.

On the other hand, when the AFC controller 106 receives the synchronization signal, it immediately stops the search. This enables reception with a good frequency relationship.

After that, when the frequency drifts due to temperature change during use and the frequency deviation exceeds the allowable range, the frequency comparator 105 similarly outputs an asynchronous signal to the AFC controller 106 and the AFC controller 106. Starts searching again. Then, when the frequency comparator 105 confirms that the frequency deviation is within the allowable range and the sub audio data is correctly received, the AFC controller 106 stops the search by transmitting the synchronization signal.

On the other hand, when the radio wave is transmitted from the wireless device, the radio wave is transmitted under the above-mentioned synchronization condition at the time of reception (frequency condition when the synchronization signal is transmitted). Therefore,
When the AFC is not synchronized with the reception, the reference frequency oscillator 103 outputs the reference frequency without control, and the transmission is performed based on this reference frequency, so that the probability of unsuccessful communication increases.

Features of AFC Operation of the Present Invention Next, features of the AFC operation of the present invention will be described. First, when the wireless device of the first embodiment is used for the first time, no information is stored in the memory 108, or the typical value corresponding to the tendency of the temperature characteristic of the reference frequency oscillator 103 composed of TCXO is the default. It is assumed to be stored as a value.

Therefore, in the first used state, the reference frequency oscillator 103 starts operating at the center of the frequency variable range or at the default value.

At this time, when the pilot signal from the base station can be correctly received and the synchronizing signal is sent from the frequency comparator 105 to the AFC controller 106, the AFC controller 106 sets the control frequency for the reference frequency oscillator 103 to the control frequency. Lock in position, reference frequency oscillator 1
The temperature at that time is input from the temperature detection sensor 107 arranged inside the 03, and the locked control frequency (frequency expressed as the number of steps described later) and the detected temperature are stored in the memory 108.

On the other hand, when the pilot signal from the base station cannot be correctly received, the frequency comparator 105 sends an asynchronous signal to the AFC controller 106. When the AFC controller 106 receives the desynchronization signal, it immediately starts the search.

When the frequencies are matched by the search of the AFC controller 106, the pilot signal from the base station is correctly received, and the frequency comparator 105 sends the synchronization signal to the AFC controller 106. The AFC controller 106 immediately stops the search (in a locked state) when the synchronization signal is input, and thereafter, stable reception is continued by the locked frequency.

At the same time, the AFC controller 106
Stores the temperature detected by the temperature detection sensor 107 (the temperature inside the reference frequency oscillator 103) and the number of AFC steps (corresponding to the control frequency) in the memory 108.

By the above operation, the detected temperature and the corresponding number of AFC steps are accumulated in the memory 108 as the radio is used daily. At this time, if the same detected temperature and the number of steps at that time are already stored, the new detected temperature and the corresponding AFC
It shall be rewritten and updated with the number of steps. By storing or updating information in this way, self-learning is carried out.

After that, if the information (the detected temperature and the corresponding number of AFC steps) is stored in the memory 108, the wireless device inputs the detected temperature from the temperature detection sensor 107 at that time after the power is turned on. Since the detected temperature is used as a search key to refer to the number of AFC steps from the information in the memory 108, and the AFC can be started immediately after starting the AFC based on the corresponding number of AFC steps, the lock wait time (wait time for synchronization) ) Is unnecessary.

As described above, in the first embodiment, since the temperature and the condition (the number of steps) of the AFC which can communicate favorably with the base station are self-learned, if the variable width of the AFC is selected to be slightly wide, refer to It is possible to maintain good communication by absorbing the adjustment error of the frequency oscillator 103, the TCXO, and the changes over time and age.

In the first embodiment, the frequency comparator 105 and the RSSI 109 are finally realized by a DSP (digital signal processing device), so that the DSP always recognizes the level of the pilot signal at the time of reception. Yes, you can avoid having to prepare RSSI.

Therefore, the frequency comparator 105 is constructed so that the frequency of the pilot signal is measured by the DSP. Further, in order to further improve reliability, sub audio data which is low speed data (300 BPS) is always transmitted at the same time as voice, and if this can be decoded, it is considered to be synchronized.

Further, although the communication is started based on the information stored in the memory 108 as described above, if a few attempts are not successful, the search is started centering on the number of AFC steps at that time. . As a result, AFC and self-learning that can cope with changes over time are efficiently executed.

Furthermore, in the first embodiment, the AFC controller 106 inputs the detected temperature from the temperature detection sensor 107, reads the corresponding number of steps from the memory 108, and starts AFC.
If not stored in 08, the search is started centering on the step number of the closest temperature. Therefore, the memory 10
It is possible to efficiently perform AFC even at a temperature at which 8 does not accumulate.

Detected temperature and AFC stored in memory
Specific Example of Number of Steps in Step A Next, a specific example of the number of detected temperatures and the number of AFC steps stored in the memory 108 will be described.

For example, various conditions when using the radio are: frequency: 220 MHz frequency deviation (transmission, legal): ± 1.5 ppm maximum frequency deviation that the receiver 104 can operate normally: ± 5
0 Hz legal temperature range: −30 ° C. to + 60 ° C. Further, it is assumed that TCXO of −30 ° C. to + 75 ° C., ± 1.5 ppm is used for the reference frequency oscillator 103, including self temperature rise.

In this case, ± 1.5 ppm at 220 MHz
Is about ± 330 Hz, and the maximum frequency deviation that the receiver 104 can normally receive is ± 50 Hz.
The number of steps N required for N is (330 × 2) ÷ 50 = 13.2≈14, and the midpoint of steps is added to this value to obtain 15 (14+
1) The step is determined. However, this number of steps indicates that at least 15 steps are required,
Of course, it is possible to improve the accuracy of the AFC by increasing the number of steps such as 32 steps and 64 steps.

The temperature information of the reference frequency oscillator 103 may be determined from the characteristics of the TCXO used and the required frequency accuracy. FIG. 3 shows an example of the characteristics of TCXO. In the temperature range of −30 ° C. to + 75 ° C., in the vicinity of −30 ° C. to −25 ° C. where the gradient is the largest, it is approximately 1.1 ppm / 15 ° C.≈0.07333 ppm /
℃.

Further, when the frequency accuracy ± 50 Hz required for normal reception of the radio device equipped with this TCXO is made to correspond to the temperature, ± 50 Hz / 220 MHz≈ ± 0.227 pp
m is 0.227 ppm / 0.07333 ppm / ° C. = 3.1
It becomes ℃. Therefore, the temperature data should be finer than the interval of 3.1 ° C. For example, an interval of 3 ° C is sufficient even if there is some margin in accuracy, and the interval of 3 ° C is used as the temperature measurement pitch. Further, the pitch of the temperature measurement does not necessarily have to be an equal interval in the temperature range of −30 ° C. to + 75 ° C.
In the range of 0 ℃ to -25 ℃, pitch of 1.5 ℃,
In the range of + 25 ° C to + 55 ° C where the change with temperature is small, it is possible to set the pitch of 4 ° C.

If the number of steps of AFC and the pitch of temperature measurement are made fine, the accuracy of AFC is improved, but it becomes necessary to increase the storage capacity of the memory 108 according to the number of pitches of temperature measurement. Taking these into consideration, the proper number of AFC steps and the pitch for temperature measurement are set.

FIG. 4 shows an example of the detected temperature and the number of steps of AFC stored in the memory 108. When the detected temperature when the pilot signal is correctly received is t ₂₀ ,
If the corresponding AFC step number is step 16, it is stored in the memory 108 as indicated by an arrow 401.
Therefore, when the power of the wireless device is turned on, the AFC controller 106 starts the AFC by reading the number of AFC steps of the corresponding detected temperature in the memory 108, using the detected temperature of the temperature detection sensor 107 at the time of turning on as a search key. be able to.

In the first embodiment, the reference frequency oscillator 1
An example of using a temperature-compensated TCXO is shown as 03, but when an oscillator that is not temperature-compensated is used, the radio wave from the base station is used as a reference frequency to operate as if it were a temperature-compensated TCXO. . In other words,
The frequency stability and frequency accuracy can be improved without expensively using the TCXO.

Output Operation of Synchronization Signal by Frequency Comparator Next, the output operation of synchronization signal by the frequency comparator 105 will be described. In the first embodiment, the frequency comparator 105
In, the pilot signal inserted in the center of the communication band is detected, the sub audio data is further decoded to determine whether the sub audio data can be correctly received, and if the sub audio data is received, the pilot signal is received. Is determined to have been correctly received, and a synchronization signal is output.

FIG. 5 shows an example of the arrangement of pilot signals and sub audio data in the TONE IN BAND spectrum. As shown in the figure, the pilot signals are incorporated near the center between the voice signals and transmitted. There is. In addition, sub audio data for controlling the system is always transmitted.

FIG. 6 shows the pilot filter 20.
9 is a filter for capturing a pilot signal in the range of about 350 Hz as shown.

As shown in FIG. 2, the frequency comparator 105
Converts an IF signal (analog signal) input from the receiver 104 into a digital signal by an A / D converter, sends the signal to the pilot filter 209 through the channel filter 208, and the pilot filter 209 (accurately, by the pilot filter 209). A signal which is a candidate for the pilot signal) is captured, and the power level of the pilot signal is measured by the pilot power sensor 210.

When the power level of the pilot signal is input from the pilot power sensor 210, the squelch driver amplifier 212 amplifies and outputs it to the squelch gate 213. The squelch gate 213 closes or opens the squelch according to the signal from the squelch driver amplifier 212. At this time, the squelch driver amplifier 212 reduces the amplification gain so that no signal is output when the input signal does not have a predetermined property. In other words, by operating according to the power level of the pilot signal, the squelch gate 213 can be kept closed when the level is below a predetermined level.

Therefore, when the power level of the pilot signal has reached the predetermined level, the squelch gate 2
13 opens, and sub audio filter 216
The sub audio data shown in FIG. 5 is demodulated through the demodulation circuit 217, and the demodulated sub audio data is decoded by the CPU 218 to determine whether the sub audio data is correctly received. CPU21
When the sub audio data is correctly received, 8 is a synchronization (lock) signal to the AFC controller 10
Output to 6.

In the wireless device of the first embodiment, considering the time for AFC operation, the time for AFC operation is set on the transmitter side (for example, the base station) as shown in FIG. It shall be provided as a pre-time.

As described above, in the first embodiment, the sub audio data is decoded to determine whether or not the sub audio data can be correctly received without determining whether the pilot signal is received correctly or not based on only the power level of the pilot signal. If it is determined that the pilot signal has been correctly received, it is determined that the pilot signal has been correctly received, and the synchronization signal is output to the AFC controller 106. Therefore, malfunction of the AFC can be reduced.

[Embodiment 2] The AFC type wireless device of Embodiment 2 is also provided with a zero-crossing counting circuit for inputting a signal that has passed through a pilot filter and counting the number of zero-crossings within a fixed time. The squelch open / close is controlled based on the count value of the counting circuit. Also, based on the count value of the zero-crossing counter circuit, it is judged whether the frequency of the pilot signal captured by the pilot filter is correct, and if it is judged that it is correct, the sub-audio data can be decoded and decoded correctly. In this case, the synchronization signal is output to the AFC controller.

FIG. 8 shows a concrete configuration diagram of the receiver and the frequency comparator of the second embodiment, in which a zero-crossing counting circuit 801 is added to the configuration diagram of the first embodiment shown in FIG. . Note that the other configurations are common to those of the first embodiment, and description thereof will be omitted.

In the figure, the zero-crossing counting circuit 8
01 inputs the signal from the pilot filter 209, counts the number of zero crossings (the number of times the signal level crosses a value of zero) within a fixed time, and sends the count value to the squelch driver amplifier 212. When the squelch driver amplifier 212 receives the zero-crossing count value from the zero-crossing counter circuit 801, it amplifies and outputs it to the squelch gate 213. The squelch gate 213 closes or opens the squelch according to the signal from the squelch driver amplifier 212.
At this time, the squelch driver amplifier 212 reduces the amplification gain so that no signal is output when the input signal does not have a predetermined property. In other words, the squelch gate 213 can be kept closed by operating with the count value of zero crossings, when the count value of zero crossings is a predetermined number or more.

The operation of the above configuration will be described. The squelch control is generally controlled by the power level of the pilot signal transmitted at a constant level regardless of the modulation. However, since squelch usually identifies very weak signals and is an amplitude modulation type receiver, the threshold level may be affected by the noise level peculiar to the receiver and the external noise level such as urban noise and snow. In the case of a receiver in which the level changes and, particularly, the squelch threshold level is fixed, it is difficult to accurately distinguish noise from a pilot signal having a low power level. In addition, an error may occur in the measurement of the frequency of the pilot signal, causing malfunction in the AFC.

Therefore, in order to avoid the above-mentioned inconvenience, as shown in FIG.
A zero-crossing counting circuit 801 is arranged after this, and squelch open / close is controlled by the number of zero-crossings. That is, although the pilot signal is used in the same manner as in the past, the number of zero crossings by the pilot signal within a certain period of time is counted instead of measuring the power level of the pilot signal. It is determined whether or not the squelch is present and the squelch is opened / closed.

Here, a method of opening / closing the squelch according to the number of zero crossings will be described with reference to FIG. When there is no pilot signal in the signal that has passed through the pilot filter 209 and there is only noise, the number of times the signal level crosses a value of zero increases, as shown in FIG. On the other hand, when the pilot signal and noise are present in the signal that has passed through the pilot filter 209, a signal waveform in which the pilot signal is superimposed on the noise is obtained, so that the signal level is as shown in FIG. Fewer crosses of zero value. Therefore, by counting this number as the number of zero crossings by the zero crossing counting circuit 801, it is possible to determine whether the input signal is noise or a regular signal including a pilot signal.

As described above, in the second embodiment, the open / close of the squelch is controlled by the number of zero crossings, so that the pilot signal and the noise can be accurately distinguished even in the place where the weak electric field and the noise floor are high. It is possible to reduce the squelch malfunction. In addition, squelch operation is possible without being affected by changes in external noise or the noise level peculiar to the receiver.

Further, in the second embodiment, as is clear from FIG. 8, whether the reception of the pilot signal is correct or not is not judged by the power level of the pilot signal, but the existence of the pilot signal is first judged by the number of zero crossings. Check and open the squelch, then decode the sub audio data to determine whether or not the sub audio data could be correctly received. If the sub audio data was correctly received, it is determined that the pilot signal was correctly received. The synchronization signal to A
Since the data is output to the FC controller 106, malfunction of the AFC can be reduced. In particular, even in the reception of a weak electric field, AFC with less malfunction can be performed.

In the second embodiment, a case has been shown in which it is determined whether or not the sub audio data has been correctly received. However, for example, even when the sub audio data is not applied to a radio system, reception of a weak electric field is performed. Needless to say, the malfunction of the AFC is reduced.

[0082]

As described above, in the AFC type wireless device (Claim 1) of the present invention, a local oscillator for oscillating a local frequency for use in generating an IF signal and a local frequency of the local oscillator are set. A reference frequency oscillator that outputs a reference frequency for controlling, a heterodyne type receiver that inputs a reception input signal from an antenna, mixes the reception input signal with the frequency from the local oscillator, and outputs an IF signal,
A frequency comparator that detects a pilot signal from the IF signal and outputs a synchronization signal or an asynchronous signal based on the presence or absence of the pilot signal, and a reference frequency of the reference frequency oscillator based on the output of the frequency comparator AF with AFC controller to lock or change
The C type wireless device includes a temperature detection sensor for detecting the temperature of the reference frequency oscillator, and a memory for storing the control frequency of the AFC controller and the detection temperature of the temperature detection sensor. When starting, the detected temperature is input from the temperature detection sensor, the corresponding control frequency is read from the memory, the reference frequency of the reference frequency oscillator is controlled based on the control frequency, and the frequency comparator is used. When the synchronization signal is input, the temperature detected by the temperature detection sensor and the control frequency for the reference frequency oscillator of the AFC controller are stored in the memory, so that the waiting time from power-on to start of use is shortened, and the device Frequency stability and frequency accuracy without increasing costs It is possible to improve the. Further, it is possible to absorb the frequency deviation due to various factors and perform stable AFC in a short time.

Also, in the AFC type wireless device (claim 2) of the present invention, when the magnitude of the pilot signal detected by the frequency comparator is smaller than a predetermined value, the AFC controller of the temperature detecting sensor Since the detected temperature and the control frequency for the reference frequency oscillator of the AFC controller are not stored in the memory, only reliable data can be stored in the memory, and AFC self-learning can be efficiently performed.

Further, in the AFC type radio device of the present invention (claim 3), even if the AFC controller attempts AFC a predetermined number of times at the control frequency, the synchronization signal is not input from the frequency comparator. Since the search is started centering on the control frequency at that time, AFC can be performed efficiently.

In the AFC type wireless device of the present invention (claim 4), the AFC controller inputs the detected temperature from the temperature detecting sensor, reads the corresponding control frequency from the memory, and starts AFC. However, if the corresponding detected temperature is not stored in the memory, the search starts around the control frequency of the closest temperature,
AFC can be performed efficiently.

Further, in the AFC type wireless device (claim 5) of the present invention, the frequency comparator inputs a pilot filter which is a rough filter of the pilot signal and a signal which has passed through the pilot filter, and the frequency is constant. Since the zero crossing counting circuit for counting the number of zero crossings in the time and the squelch circuit for controlling the open / close of the squelch based on the count value of the zero crossing counting circuit are provided, the weak electric field and the noise floor are high. Even in the place, the pilot signal and the noise can be accurately distinguished.

Further, in the AFC type radio device of the present invention (claim 6), the frequency comparator inputs a pilot filter which is a rough filter of the pilot signal and a signal which has passed through the pilot filter, and keeps constant. A zero-crossing counting circuit for counting the number of zero-crossings in a time period, and a judging circuit for judging whether or not the frequency of the pilot signal captured by the pilot filter is correct based on the count value of the zero-crossing counting circuit,
A synchronization circuit that decodes the sub-audio data when the frequency of the pilot signal is determined to be correct by the determination circuit, and outputs a synchronization signal to the AFC controller when the sub-audio data can be decoded correctly. Therefore, AFC with few malfunctions can be performed even when receiving a weak electric field.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an AFC wireless device according to a first embodiment.

FIG. 2 is a specific configuration diagram of a receiver and a frequency comparator according to the first embodiment.

FIG. 3 is an explanatory diagram showing a characteristic example of TCXO.

FIG. 4 is an explanatory diagram showing an example of the detected temperature and the number of steps of AFC stored in a memory.

FIG. 5 is an explanatory diagram showing an example of arrangement of pilot signals and sub audio data in a TONE IN BAND spectrum.

FIG. 6 is an explanatory diagram showing an example of a pilot filter.

FIG. 7 is an explanatory diagram showing an example in which a time for AFC operation is provided as a pretime on the transmitter side (for example, a base station).

FIG. 8 is a specific configuration diagram of a receiver and a frequency comparator according to the second embodiment.

FIG. 9 is an explanatory diagram showing a method of performing squelch opening / closing depending on the number of zero crossings.

FIG. 10 is a range of frequency stability required in the TONE IN BAND system (± 50 Hz to ± 100 Hz).
FIG.

[Explanation of symbols]

 101 Antenna 102 Local Oscillator 103 Reference Frequency Oscillator 104 Receiver 105 Frequency Comparator 106 AFC Controller 107 Temperature Detection Sensor 108 Memory 109 RSSI 209 Pilot Filter 210 Pilot Power Sensor 212 Squelch Driver Amplifier 213 Squelch Gate 218 CPU 801 Zero Crossing Count Circuit

Claims (6)

[Claims] 1. A local oscillator for oscillating a local frequency for use in generating an IF signal, a reference frequency oscillator for outputting a reference frequency for controlling the local frequency of the local oscillator, and a received input signal from an antenna. Then, a heterodyne type receiver that mixes the received input signal with the frequency from the local oscillator and outputs an IF signal, and a pilot signal from the IF signal is detected, and based on the presence or absence of the pilot signal, a synchronization signal or Based on a frequency comparator that outputs an asynchronous signal and the output of the frequency comparator,
In an AFC type radio having an AFC controller for locking or changing the reference frequency of the reference frequency oscillator, a temperature detection sensor for detecting the temperature of the reference frequency oscillator, a control frequency of the AFC controller and a temperature detection sensor A memory for storing the detected temperature, the AFC controller inputs the detected temperature from the temperature detection sensor when starting AFC, reads the corresponding control frequency from the memory,
The reference frequency of the reference frequency oscillator is controlled based on the control frequency, and when the synchronization signal is input from the frequency comparator, the detected temperature of the temperature detection sensor and the control frequency of the AFC controller for the reference frequency oscillator. Is stored in the memory. An AFC wireless device. 2. The AFC controller, when the magnitude of the pilot signal detected by the frequency comparator is smaller than a predetermined value, the detected temperature of the temperature detection sensor and the control frequency of the AFC controller for the reference frequency oscillator, The AFC type wireless device according to claim 1, wherein the wireless device is not stored in the memory. 3. The AFC controller starts a search centered on the control frequency at that time when the synchronization signal is not input from the frequency comparator even if the AFC is tried a predetermined number of times with the control frequency. Claim 1
AFC type wireless device described. 4. The AFC controller inputs the detected temperature from the temperature detection sensor, reads a corresponding control frequency from the memory, and starts AFC, but the detected temperature is not stored in the memory. If
The AFC type wireless device according to claim 1, wherein the search is started centering on the control frequency of the closest temperature. 5. The frequency comparator comprises: a pilot filter, which is a rough filter of a pilot signal; and a zero-crossing counting circuit, which receives the signal that has passed through the pilot filter and counts the number of zero-crossings within a certain period of time. 2. The AFC radio apparatus according to claim 1, further comprising a squelch circuit that controls open / close of the squelch based on the count value of the zero-crossing counter circuit. 6. The frequency comparator comprises: a pilot filter, which is a rough filter of a pilot signal; and a zero-crossing counting circuit, which receives the signal passed through the pilot filter and counts the number of zero-crossings within a certain period of time. A judgment circuit for judging whether or not the frequency of the pilot signal captured by the pilot filter is correct based on the count value of the zero-crossing counter circuit, and a case where the judgment circuit judges that the frequency of the pilot signal is correct The AFC wireless system according to claim 1, further comprising a synchronization circuit that decodes the sub-audio data and outputs a synchronization signal to the AFC controller when the sub-audio data is decoded correctly. Machine.