JP2944520B2 - Wireless telephone equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio telephone apparatus, and more particularly, to a local oscillator signal generated and received by a PLL frequency synthesizer circuit using a voltage controlled oscillator that changes an output frequency in accordance with a control voltage change as a reference oscillator. A superheterodyne system in which a control voltage corresponding to a deviation from a reference frequency is generated for an intermediate frequency signal obtained by mixing the local oscillation signal with a radio frequency signal and applied to the voltage controlled oscillator to perform automatic frequency control A wireless telephone device.

[0002]

2. Description of the Related Art A conventional super-heterodyne type radio telephone apparatus is constructed as shown in FIG. In the wireless telephone device 200 shown in FIG. 3, the mixer 2 is a circuit for outputting an IF (intermediate frequency) signal based on a radio frequency reception signal fetched from the antenna 1 and a local oscillation signal from the PLL loop B. A PLL frequency synthesizer circuit that generates a local signal and includes a frequency divider 12, a charge pump 13, a voltage controlled oscillator 14, and a frequency divider 15, and a PLL loop A includes a phase comparator 5, a frequency divider 6, and a VCT
A PLL frequency synthesizer circuit composed of a CXO (voltage-controlled temperature-compensated crystal oscillator) 7 and a charge pump 8 for comparing the IF signal with a reference frequency by the VCTCXO 7 and controlling the oscillation frequency of the VCTCXO 7;
A circuit that divides the signal and supplies the divided signal to the phase comparator 5 of the PLL loop A. The divider 11 divides the output of the VCTCXO 7 to perform PLL.
The circuit provided to the phase comparator 12 of the loop B, the demodulation circuit 3, is a circuit for demodulating the IF signal. Dividers 4, 11, PL
An AFC (automatic frequency control) circuit for the IF signal frequency is configured from the L loop A and the PLL loop B.

[0003] Next, the operation of the radio telephone apparatus 200 will be described in the case of UPPER (upper) local where the frequency of the local oscillation signal generated by the PLL loop B is higher than the reception frequency. The received wave input from the antenna 1 is mixed by the mixer 2 with the local signal generated by the PLL loop B, converted into an IF signal, and output. Generally, the frequency of the IF signal is operated by an AFC circuit so as to be a constant frequency.
The case of KHz will be described. The IF signal output from the mixer 2 is frequency-divided by the frequency divider 4 and compared with the reference frequency VCTCXO 7 output frequency divided by the frequency divider 6 by the phase comparator 5. The VCTCXO7 control voltage is output.

Here, as a result of comparing the output of the frequency divider 4 with the output of the frequency divider 6, the output of the charge pump 8 becomes lower when the output of the frequency divider 4 becomes higher. If the output is lower, it will be higher.

When the IF frequency becomes higher than 450 KHz, the output of the frequency divider 4 becomes higher than the output of the frequency divider 6 and the VCTCXO control voltage output to the output of the charge pump 8 becomes lower. If the input control voltage vs. output frequency characteristic of the VCTCXO 7 is a positive characteristic (the frequency increases and decreases in response to the increase and decrease of the control voltage), the output frequency of the VCTCXO 7 also decreases. The output frequency of the VCTCXO 7 is also a reference for the frequency of the local oscillation signal, and the frequency of the local oscillation signal generated by the PLL loop B after being divided by the frequency divider 11 is also reduced. Now the local oscillator signal frequency is UPP
Since it is ER local, the IF frequency will drop, and the AFC will keep the IF frequency constant at 450 KHz.
Operate.

On the other hand, when the IF frequency is lower than 450 KHz, the output of the frequency divider 4 is lower than the output of the frequency divider 6 and the output voltage of the charge pump 8 is higher.
The O7 output frequency increases. Then, the local oscillation signal frequency becomes higher, the IF frequency becomes higher, and the IF frequency becomes 450 kHz.
AFC operation is performed as follows.

Although the input control voltage versus output frequency characteristic of the VCTCXO 7 has been described as a positive characteristic, if the characteristic is a negative characteristic (the frequency decreases or increases in response to an increase or decrease in the control voltage), the IF frequency is 450 KHz. When the voltage becomes higher, the output voltage of the charge pump 8 becomes lower, the output frequency of the VCTCXO 7 rises, the frequency of the local oscillation signal rises, and the IF frequency further rises. IF frequency is 450K
If the frequency is lower than Hz, the output frequency of the VCTCXO7 decreases and the local oscillation signal frequency decreases, so that the IF frequency further decreases and the AFC operation is not performed.

Contrary to the case of the UPPER local described above, in the case of the LOWER (lower) local where the frequency of the local oscillation signal generated by the PLL loop B is lower than the reception frequency, the input control voltage of the VCTCXO 7 is The output frequency characteristic requires a negative characteristic. If the characteristic is negative, the AFC operation is performed in the same manner as described above. Conversely, if the input control voltage versus output frequency characteristic of the VCTCXO 7 is a positive characteristic, the AFC operation will not be performed.

[0009]

In the above-mentioned conventional radio telephone device, the case where the local oscillation signal is UPPER local and the case where L
VCTCXO required for the case of the OWER local
Input voltage vs. output frequency characteristics (positive and negative characteristics)
Are different from each other, the VCTCXO cannot be used in common, and it is assumed that a VCTCXO having a positive characteristic of input control voltage versus an output frequency characteristic is required in a UPPER local radio telephone apparatus. VCTCX of input control voltage vs. output frequency characteristics
O was required. For this reason, there is a drawback that the number of types of VCTCXO increases and causes an increase in cost.
When the local oscillation signal frequency is changed from UPPER to LOWER or from LOWER to UPPER, VC
There is a disadvantage that the design of the TCXO needs to be changed.

An object of the present invention is to make it possible to use one VCTCXO in common by setting an optimum output frequency characteristic of a VCTCXO necessary for each of a local signal and an UPPER local or a LOWER local signal. A wireless telephone device is provided.

[0011]

According to the present invention, a local frequency signal is generated by a PLL frequency synthesizer circuit using a voltage controlled oscillator for changing an output frequency in accordance with a control voltage change as a reference oscillator, and a received radio frequency signal is generated. A super-heterodyne wireless telephone that performs automatic frequency control by generating a control voltage corresponding to a deviation from a reference frequency for an intermediate frequency signal obtained by mixing the local oscillation signal and applying the same to the voltage-controlled oscillator. In the apparatus, at a control voltage input terminal of the voltage-controlled oscillator, a characteristic switching means capable of switching a change characteristic of an output frequency with respect to a change of a control voltage to either an original characteristic of the voltage-controlled oscillator or an inverted characteristic thereof. Depending on whether the local oscillator signal frequency is set to be higher or lower than the received signal frequency. It has a configuration for performing the specified switch controls the selection to be characteristic of the characteristic switching means.

In the above configuration, the voltage-controlled oscillator is a voltage-controlled temperature-compensated crystal oscillator (VCTCXO), or the characteristic switching means increases / decreases an output voltage according to an increase / decrease of an input voltage. Forward buffer means having a positive characteristic to cause the output voltage to decrease / increase according to the increase / decrease of the input voltage; and inverting means having a negative characteristic to select one of the forward buffer means and the inversion buffer means. And a control voltage generated through a designated one of the forward buffer means and the inverting buffer means may be applied to the voltage controlled oscillator.

[0013] Furthermore, both the first frequency band and the second frequency band which are separated from each other as a reception frequency band are provided, and the local oscillation signal frequency is set at an intermediate level between the first frequency band and the second frequency band. It is possible to adopt a configuration in which a characteristic to be selected by the characteristic switching means is specified and switching control is performed in accordance with a reception frequency band to be actually received.

According to the present invention, an optimum voltage controlled oscillator (VCTC) is selected by the characteristic switching circuit and the characteristic specifying circuit according to whether the local oscillation signal is UPPER or LOWER.
XO) output frequency can be set, so UPPER
A single VCTCXO can be commonly used in a local radio telephone device, a lower local radio telephone device, or a radio telephone device having both of them, and the cost of the device can be reduced by using common components. It can be carried out.

[0015]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, and shows only a part related to the present invention in a wireless telephone device. FIG.
Is different from the conventional wireless telephone device 200 shown in FIG.
Output side of charge pump 8 of L loop A and VCTCXO
A characteristic switching circuit 9 capable of switching the characteristic of the control voltage input to the VCTCXO 7 to a positive characteristic or a negative characteristic with respect to a change in the output voltage of the charge pump 8 with the input side of the charge pump 8
And the characteristic switching circuit 9 is provided with a characteristic specifying circuit 10 for specifying whether to select a positive characteristic or a negative characteristic. Other circuit blocks denoted by the same reference numerals as those in FIG. 3 have the same functions and configurations. Also, other circuits necessary for the wireless telephone device, such as voice input means, voice output means, dial means, etc., can be realized by appropriate well-known techniques, and thus illustration and description are omitted.

The characteristic switching circuit 9 of the PLL loop A includes a forward buffer having a positive characteristic (see FIG. 2A) for increasing / decreasing an output voltage according to an increase / decrease of an input voltage, and an increase / decrease of an input voltage. An inverting buffer having a negative characteristic (see FIG. 2B) for decreasing / increasing the output voltage in accordance with the decrease, and one of the forward buffer and the inverting buffer is selected in accordance with a control signal from the characteristic specifying circuit 10. And a switch (both not shown). The output voltage of the charge pump 8 is input as an input voltage of a forward buffer and an inversion buffer, and is converted into a corresponding output voltage. One of these output voltages is selected by a switch and input to the VCTCXO 7 as a control voltage. Therefore, the change characteristic of the oscillation frequency with respect to the change of the control voltage in the VCTCXO 7 has the positive characteristic (the frequency increases or decreases in response to the increase or decrease of the voltage) or the negative characteristic (the frequency decreases in response to the increase or decrease of the voltage). )),
The change characteristic of the oscillation frequency with respect to the change of the output voltage of the charge pump 8 can be arbitrarily changed to a positive characteristic or a negative characteristic. The input / output characteristics of the forward buffer are shown in FIG.
As shown in (A), the minimum value of the input voltage (VImin)
The output voltage also changes from the minimum value (VOmin) to the maximum value (VOmax) with respect to a linear change from the maximum value (VImax) to the maximum value (VImax).
Desirably, it changes linearly. Also, VImin =
If VOmin and VImax = VOmax, the input voltage can be used as it is as the output voltage, and the forward buffer can be omitted to establish a through connection.

Next, the operation of the wireless telephone device 100 of this embodiment will be described. In this embodiment, it is assumed that the IF frequency is 450 KHz as in the example of the prior art, and the output voltage characteristics of the charge pump 8 are the frequency divider 4, the output and the frequency divider 6.
As a result of comparing the outputs, the output becomes lower when the output of the divider 4 becomes higher (IF frequency rise), and becomes higher when the output of the divider 4 becomes lower (IF frequency lower). This will be described below.

The case where the frequency of the local oscillation signal generated by the PLL loop B is higher than the reception frequency (UPPER local) will be described below. In the present embodiment,
In the case where the local oscillation signal is UPPER local, in order to perform the AFC operation so that the IF frequency becomes constant, assuming the output voltage characteristic of the charge pump 8 as described above, the output frequency of the VCTCXO 7 with respect to the output voltage of the charge pump 8 The characteristic must be a positive characteristic, and if the input control voltage versus output frequency characteristic of the VCTCXO 7 is a positive characteristic, the characteristic switching circuit 9 must switch to the positive characteristic. Therefore, the characteristic switching circuit 9 is switched to the positive characteristic by the characteristic specifying circuit 10, that is, by switching the switch to the forward buffer or through connection side having the characteristic of FIG. explain).

The received signal of the radio frequency input from the antenna 1 and the local signal generated by the PLL loop B are mixed by the mixer 2 to output an IF signal. IF
The following operation is performed so that the frequency of the signal becomes constant at 450 KHz by the AFC operation. The IF signal output from the mixer-2 is frequency-divided by the frequency divider 4 and compared with the frequency-divided output frequency of the reference frequency VCTCXO 7 by the frequency divider 6 by the phase comparator 5. Output voltage.

When the IF frequency is higher than 450 KHz, the output of the divider 4 is higher than the output of the divider 6 and the output voltage of the charge pump 8 is lower. Here, the characteristic switching circuit 9 is switched to the positive characteristic, and the VCTCXO7 output frequency characteristic with respect to the output voltage of the charge pump 8 is the positive characteristic, so that the VCTCXO7 output frequency decreases. The output frequency of the VCTCXO 7 is also a reference for the frequency of the local oscillation signal, and the frequency of the local oscillation signal generated by the PLL loop B after being divided by the frequency divider 11 is also reduced. Now, since the local oscillation signal frequency is set to UPPER local, the IF frequency is lowered, and the AFC operation is performed so that the IF frequency becomes constant at 450 KHz.

On the other hand, when the IF frequency becomes lower than 450 KHz, the output of the frequency divider 4 becomes lower than the output of the frequency divider 6 and the output voltage of the charge pump 8 becomes higher.
The O7 output frequency increases. Then, the local oscillation signal frequency becomes higher, the IF frequency becomes higher, and the IF frequency becomes 450 kHz.
AFC operation is performed so as to be constant.

When the frequency of the local oscillation signal generated by the PLL loop B is lower than the reception frequency (LOWER local), the characteristic of the output frequency of the VCTCXO 7 with respect to the output voltage of the charge pump 8 must be negative. , VCTCXO7 have a positive characteristic with respect to the input control voltage versus output frequency characteristic, the characteristic switching circuit 9 needs to switch to a negative characteristic. Therefore, the AFC operation is similarly performed by switching the characteristic switching circuit 9 to the negative characteristic by the characteristic specifying circuit 10, that is, by switching the switch to the inverting buffer side having the characteristic of FIG.

As described above, according to this embodiment, the case where the local oscillation signal is UPPER local and the case where
In both the local case and the local case, the VCT of the local oscillator signal oscillation PLL synthesizer circuit having the AFC function is used.
The CXO can be used in common without any change. Therefore, even when two types of wireless telephone devices, an UPPER local wireless telephone device and a LOWER local wireless telephone device, are required, only one type of VCTCXO needs to be designed and manufactured.
Switching of R / LOWER is performed by designating from the characteristic designating circuit 10 at the time of assembly.

The technique of the present invention can also be applied to a case where one wireless telephone device requires both UPPER local and LOWER local. For example, in the case of a wireless telephone device having both a 400 MHz band and an 800 MHz band as a receiving frequency band, by setting the local oscillation frequency in the middle, the UPPER for the 400 MHz band is set.
Local and LOWER local for the 800 MHz band. Then, the characteristic of the input voltage versus the output voltage of the characteristic switching circuit 9 is switched between the positive characteristic and the negative characteristic via the characteristic specifying circuit 10 according to the reception frequency band actually received.

[0025]

According to the present invention, the local oscillator signal has a function of changing the output frequency in response to a change in the control voltage provided for providing an automatic frequency control function for the intermediate frequency signal.
To the control voltage input terminal of a voltage controlled oscillator such as CTCXO,
Characteristic switching means capable of switching the change characteristic of the output frequency with respect to the control voltage change to either the original characteristic of this voltage controlled oscillator or its inverted characteristic is added, and the local oscillation signal frequency is higher than the reception signal frequency. (UPPER local) or low (LOWER local) is set to specify a characteristic to be selected by the characteristic switching means, and switching control is performed.
A voltage controlled oscillator, especially an expensive V, in a PER local radio telephone and a LOWER local radio telephone
The CTCXO can be used in common, and the local oscillation signal frequency can be changed from UPPER to LOWER or L, such as one radiotelephone device having a plurality of types of reception frequency bands.
Even when changing from OWER to UPPER, there is an advantage that the voltage controlled oscillator (VCTCXO) can be commonly used without having to change the design. This facilitates design and reduces the cost of the device.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

2A and 2B are diagrams illustrating characteristics of an input voltage versus an output voltage of the characteristic switching circuit illustrated in FIG. 1, wherein FIG. 2A shows a positive (forward) characteristic, and FIG. 2B shows a negative (inversion) characteristic; ,

FIG. 3 is a block diagram showing a conventional wireless telephone device.

[Explanation of symbols]

 Reference Signs List 2 mixer 3 demodulation circuit 4, 6, 11, 15 frequency divider 5, 12 phase comparator 7 VCTCXO 8, 13 charge pump 9 characteristic switching circuit 10 characteristic specification circuit 14 voltage controlled oscillator 100 wireless telephone device

Claims (4)

(57) [Claims] 1. A local oscillator signal is generated by a PLL frequency synthesizer circuit using a voltage controlled oscillator that changes an output frequency in accordance with a control voltage change as a reference oscillator, and the local oscillator signal is mixed with a received radio frequency signal. A superheterodyne wireless telephone device that performs automatic frequency control by generating a control voltage corresponding to a deviation from a reference frequency for the obtained intermediate frequency signal and applying the control voltage to the voltage controlled oscillator, To the control voltage input terminal, a characteristic switching means capable of switching the change characteristic of the output frequency with respect to the change of the control voltage to either the original characteristic of this voltage controlled oscillator or its inverted characteristic is added, Selection of the characteristic switching means depending on whether the local oscillation signal frequency is set to be higher or lower. Wireless telephone apparatus and performs switching control to specify the to properties. 2. The wireless telephone device according to claim 1, wherein said voltage controlled oscillator is a voltage controlled temperature compensated crystal oscillator (VCTCXO). 3. The method according to claim 2, wherein the characteristic switching means increases / decreases an input voltage.
Positive characteristic forward buffer means for increasing / decreasing the output voltage as the voltage decreases, inverting buffer means with a negative characteristic for decreasing / increasing the output voltage as the input voltage increases / decreases, and these forward buffer means and inversion buffer A switching means for selecting one of the means, and applying a control voltage generated through a designated one of the forward buffer means and the inverting buffer means to the voltage controlled oscillator. A wireless telephone device as described. 4. A receiving frequency band comprising both a first frequency band and a second frequency band which are separated from each other, and a local oscillation signal frequency is set to an intermediate value between the first frequency band and the second frequency band. 4. The wireless telephone device according to claim 1, wherein a characteristic to be selected by said characteristic switching means is specified and switching control is performed according to a reception frequency band actually received.