JPH06232780A - Communication equipment - Google Patents

Abstract

PURPOSE:To vary a reception frequency at a high speed without use of a special component by selecting an intermediate frequency filter based on an oscillator frequency of a PLL frequency synthesizer. CONSTITUTION:A reception signal from an antenna 1 is mixed with an oscillator frequency of a PLL frequency synthesizer 30 at a mixer 5 via a BPF 3 and a high frequency, amplifier 4 and converted into an intermediate frequency signal. Any of IF filters 7-1-7-M is selected by selectors 6, 8 based on the oscillator frequency from the synthesizer 30 and an IF signal outputted from the mixer 5 passes through the selected IF filter, demodulated at a demodulator 10 and the demodulated signal is outputted to a low frequency stage. Thus, the reception frequency is revised at a high speed. Moreover, the transmission frequency is varied at a high speed by selecting a carrier oscillator based on the oscillator frequency of the PLL frequency synthesizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device, and more particularly to a communication device having a shortened channel switching time.

[0002]

2. Description of the Related Art In a communication device, a communication frequency is generally given in a communication band at a certain interval (channel separation). For example, in the conventional communication device shown in FIG.
In the LL frequency synthesizer 30, the phase comparison frequency of the phase comparator 13 takes the same value as the channel separation, and the frequency division ratio of the frequency divider 15 of the PLL frequency synthesizer is varied to determine the communication frequency in the communication band. Is configured.

[0003]

When the communication frequency is determined by such a method, for example, even if it is desired to perform high-speed scanning of the transmission / reception frequency within the communication band or change the transmission / reception frequency at high speed, the PLL frequency synthesizer can be used. There is a problem that it is difficult to realize it because the response is limited.

In addition, a voltage controlled oscillator (VCO) preset method for changing the frequency at high speed,
Fractional frequency division methods have been proposed, but these methods have problems that the circuit scale becomes large and that special parts are required.

It is an object of the present invention to provide a communication device capable of high-speed variable transmission / reception frequency without using special parts.

[0006]

SUMMARY OF THE INVENTION A communication device of the present invention is a communication device having a PLL frequency synthesizer as a local oscillator, and a plurality of intermediate frequencies having center frequencies set at the same frequency intervals as channel separation in a communication band. It is characterized by comprising a filter and a selection means for selecting the intermediate frequency filter, and varying the reception frequency by selecting the intermediate frequency filter based on the oscillation frequency of the PLL frequency synthesizer.

The communication device of the present invention uses a PL as a local oscillator.
In a communication device including an L frequency synthesizer, a plurality of carrier oscillators whose oscillation frequencies are set at the same frequency intervals as channel separation in a communication band,
Selecting means for selecting a carrier oscillator, P
The transmission frequency is variable by selecting the carrier oscillator based on the oscillation frequency of the LL frequency synthesizer.

In the communication device according to claim 1 of the present invention,
An intermediate frequency amplifier and a demodulator paired with the intermediate frequency filter are provided, and the pair of intermediate frequency filter, intermediate frequency amplifier and demodulator are selected to vary the reception frequency.

[0009]

According to the communication device of the present invention, one intermediate frequency filter among a plurality of intermediate frequency filters whose center frequencies are set at the same frequency intervals as the channel separation in the communication band is based on the oscillation frequency of the PLL frequency synthesizer. And the reception frequency is changed. In this case, the reception frequency for each channel separation can be obtained even if the phase comparison frequency M times the channel separation is used. However, the lockup time when the oscillation frequency of the PLL frequency synthesizer is changed by multiplying the phase comparison frequency by M is shortened to 1 / √M, and the reception frequency can be changed at high speed.

According to the communication device of the present invention, one carrier oscillator is selected from a plurality of carrier oscillators whose oscillation frequencies are set at the same frequency intervals as the channel separation in the communication band based on the oscillation frequency of the PLL frequency synthesizer. Then, the transmission frequency is changed. In this case, the transmission frequency for each channel separation can be obtained even if the phase comparison frequency M times the channel separation is used. However, when the phase comparison frequency is multiplied by M, the lockup time when the oscillation frequency of the PLL frequency synthesizer is changed is shortened to 1 / √M, and the transmission frequency can be changed at high speed.

[0011]

EXAMPLES The present invention will be described below with reference to examples. Figure 1
FIG. 3 is a block diagram showing the configuration of an embodiment of the present invention.

The communication device of this embodiment includes a plurality of M intermediate frequency filters 7-1, ..., 7-M, whose center frequencies are set at the same frequency intervals as the channel separation, and the channel separation. M carrier oscillators whose oscillation frequencies are set at the same frequency intervals 1
7-1, ..., 17-M.

The antenna 1 is connected to an antenna switching device 2, and in the case of reception, the antenna switching device 2 is supplied to a high frequency amplifier 4 through a communication band filter 3 for amplification,
The mixer 5 mixes the frequency with the oscillation frequency from the PLL frequency synthesizer 30 and converts it into an intermediate frequency signal f _IF .

The intermediate frequency signal output from the mixer 5 is
, 7-M among the M intermediate frequency filters 7-1, ..., 7-M are output through an intermediate frequency filter selected by the selector 6 based on the oscillation frequency of the PLL frequency synthesizer 30, and are switched in conjunction with the selector 6. Selector 8
Is supplied to and amplified by the intermediate frequency amplifier 9. The intermediate frequency signal amplified by the intermediate frequency amplifier 9 is demodulated by the demodulator 10 and output to the low frequency stage as a demodulated signal.

The PLL frequency synthesizer 30 is a VCO1.
1, a low pass filter 12, a phase comparator 13, a reference oscillator 14 and a frequency divider 15. The oscillation output of the reference oscillator 14 and the output from the frequency divider 15 are phase-compared in the phase comparator 13, and the low pass filter 12 The oscillation frequency of the VCO 11 is controlled by the passed phase comparison output, which is supplied to the mixer 5 as a local oscillation output, and also divided by the frequency divider 15 to be supplied to the phase comparator 13. Here, when the channel separation is Δf, the phase comparison frequency, that is, the frequency of the output from the frequency divider is M × Δ.
Selected for f.

For transmission, M carrier oscillators 17
, ..., 17-M PLL by selector 18
The carrier wave output from the carrier oscillator selected based on the oscillation frequency of the frequency synthesizer 30 is the modulator 19
Is modulated by the modulation signal at
It is supplied to 0, is frequency-mixed with the oscillation frequency from the PLL frequency synthesizer 30, and is converted into a high frequency signal. The output from the mixer 20 is supplied to a transmission output amplifier 21 for amplification, and then is output from the antenna 1 through the communication band filter 22 and the antenna switch 2.

The control device 16 switches the frequency division ratio switching signal for switching the frequency division ratio of the frequency divider 15 and the intermediate frequency filters 7-1, ..., 7-M according to the caller or the request of the communication protocol. Switching signals of the selectors 6 and 8 and a selector 18 for switching the carrier oscillators 17-1 ..., 17-M
To generate a switching signal for dividing ratios, selectors 6 and 8,
The selector 18 is switched according to the caller or the request of the communication protocol.

The operation of this embodiment constructed as described above will be described below.
Taking M = 2 as an example, the frequency channel separation is Δf = 0.05 MHz and the frequency f ₁ = 1.
10 MHz, f ₂ = 110.5 MHz, transmission / reception frequency =
1000MHz, 1000.05MHz, 1000.1
The case of MHz, ... Will be described. Where f ₁ and f ₂
Indicates the intermediate frequency and the carrier frequency, and the intermediate frequency f
Represent at _IF .

The phase comparison frequency of the PLL frequency synthesizer 30 is from M × Δf to 2 × 0.05 MHz = 0.1M
It becomes Hz. Channel separation is 0.05MH
Since it is z, only 1/2 of the communication channel assigned to the communication band can be received as it is, but it is possible to cover all channels by switching the frequencies f ₁ and f ₂ . This will be described with reference to Table 1.

[0020]

[Table 1]

Table 1 shows the frequency and operation of each part when the channel is changed. When changing the channel number from channel number 1 to channel number 2,
Since the division ratio does not change, the PLL frequency synthesizer 3
The output frequency of 0 does not change. However, selectors 6 and 8
Since and 18 are switched from a to b, the intermediate frequency f _IF is 110.05MHz-110MHz = 0.05M
Hz is changing. Since the communication band filters 3 and 22 do not have frequency selectivity in the communication band, this is nothing but a change in the transmission / reception frequency by 0.05 MHZ.

Next, change the channel number to channel number 2.
→ When changing to channel number 3, the division ratio is 89
00 to 8901, the output frequency of the PLL frequency synthesizer 30 is equal to the phase comparison frequency.
Only 1MHz higher. At this time, since the selectors 6, 8 and 18 are switched from b to a, the intermediate frequency f _IF
Is 0.05 MHz lower. As a result, 0.1 MHz-
The transmission / reception frequency is changed by 0.05 MHz = 0.05 MHz.

From the above, it can be seen that it is possible to obtain the transmission / reception frequency for each channel separation even if the phase comparison frequency of M times the channel separation is used.

Here, considering the frequency response of the PLL frequency synthesizer 30, the natural angular frequency ωn in the loop response of the general PLL frequency synthesizer 30 is
It is given by ωn = k / √N. Here, k is a constant and N is a frequency division ratio. Therefore, when the phase comparison frequency is multiplied by M, N becomes N / M, and as a result, the natural angular frequency ωn
Is increased by √M times. That is, the lockup time when the oscillation frequency of the PLL frequency synthesizer 30 is changed is shortened to 1 / √M. In this example, since M = 2, a reduction of about 30% is performed.

It should be noted that the intermediate frequency filter has a delay time, and therefore a certain finite time is required for switching the intermediate frequency filter, but this time is much shorter than the time handled by the present invention, which causes a problem. do not become.

Next, a modification of the embodiment of the present invention will be described. FIG. 2 is a block diagram showing a modification of the embodiment of the present invention. In this modified example, the intermediate frequency filters 7-1, 7-2, ..., 7-M and the intermediate frequency amplifier 9 corresponding to the number of center frequencies of the intermediate frequency filter are provided.
-1, 9-2, ..., 9-M and demodulators 10-1, 10-
, ..., 10-M, each set corresponds to the center frequency of the intermediate frequency filter, and one of the sets is selected by the selectors 6 and 8. .

The operation of this modified embodiment is the same as that of the above-mentioned embodiment except that the intermediate frequency filter, the intermediate frequency amplifier and the demodulator forming a set are selected together. This modified embodiment is effective when the input frequency of the demodulator has a one-to-one correspondence with the center frequency of the intermediate frequency filter.

[0028]

As described above, according to the communication device of the present invention, there is an effect that the transmission / reception frequency can be changed at high speed without special correspondence to the PLL frequency synthesizer. Further, since the PLL frequency synthesizer itself tends to raise the phase comparison frequency, there is also an effect that deterioration of C / N due to the speedup of the frequency response of the PLL frequency synthesizer does not occur.

Furthermore, according to the communication device of the present invention, there is an effect that it does not require any special parts and can be constituted by conventionally used parts.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration of a modified example of the exemplary embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional communication device.

[Explanation of symbols]

 5 and 20 mixer 6, 8 and 18 selector 7-1, 7-2, 7-M intermediate frequency filter 9, 9-1, 9-2, 9-M intermediate frequency amplifier 10, 10-1, 10-2, 10-M demodulator 11 VCO 12 low-pass filter 13 phase comparator 14 reference oscillator 15 frequency divider 16 controller 17-1, 17-2, 17-M carrier oscillator 19 modulator 30 PLL frequency synthesizer

Claims (3)

[Claims] 1. A communication device equipped with a PLL frequency synthesizer as a local oscillator, for selecting a plurality of intermediate frequency filters having center frequencies set at the same frequency intervals as channel separation in a communication band, and selecting the intermediate frequency filter. A communication device comprising: a selecting unit, wherein the reception frequency is varied by selecting an intermediate frequency filter based on the oscillation frequency of the PLL frequency synthesizer. 2. In a communication device having a PLL frequency synthesizer as a local oscillator, a plurality of carrier oscillators whose oscillation frequencies are set at the same frequency intervals as channel separation in a communication band, and a selection means for selecting the carrier oscillator. And a transmission frequency variable by selecting a carrier oscillator based on an oscillation frequency of a PLL frequency synthesizer. 3. The communication device according to claim 1, further comprising an intermediate frequency amplifier and a demodulator paired with the intermediate frequency filter, and selecting the paired intermediate frequency filter, the intermediate frequency amplifier and the demodulator to select the reception frequency. A communication device that is characterized by varying.