JPH05206891A - Specific small power radio installation - Google Patents

Abstract

PURPOSE:To attain the cost reduction and miniaturization by using a phase locked loop circuit comprising a voltage controlled oscillator (VCO) and a phase comparator or the like in common use for transmission and reception. CONSTITUTION:When a reception circuit 4 inputs a reception high frequency signal to a mixer 4b via an amplifier 4a, the mixer 4b mixes the received high frequency signal with an oscillation signal from a phase locked loop circuit 5 and an intermediate frequency signal being a difference between the signals is outputted via a SAW (Surface Acoustic Wave) filter 4c. Moreover, digital data received by the voltage controlled oscillator (VCXO) 3a of the transmission circuit 3 are modulated by using a prescribed oscillation frequency and the result is fed to the mixer 3b, in which an output signal of the VCXO 3a is mixed with an oscillation signal from the phase locked loop circuit 5. Only a transmission high frequency signal being a difference between mixed frequency signals is extracted from the output of the mixer 3b through the amplifier 3c and fed to a duplexer 2 as an output of the transmission circuit 3 and the signal is sent from an antenna.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to specific low power radio equipment used in cordless phones, data transmission devices and the like.

[0002]

2. Description of the Related Art Specified low power radio equipment (TRX) is a cordless phone for transmitting and receiving voice signals between a base unit (handset) connected to a telephone line and a cordless handset (handset) equipped with a handset. It is used for etc. It is also used for the purpose of wirelessly transmitting data from the printer port on the computer side to the printer when the printer cable cannot be installed due to the distance between the computer and the printer.

The specified low power radio equipment for data transmission has 10 channels of combinations of transmission and reception frequencies. For example, in the first channel, 429.8125 MHz is assigned as the transmission frequency of the master unit and the reception frequency of the slave unit. , 449 as the reception frequency of the master unit and the transmission frequency of the slave unit.
7125 MHz is allocated. Further, frequencies higher by 0.0125 MHz each are sequentially allocated to the second and subsequent channels. Therefore, this specific low power radio equipment is required to switch between two types of frequencies for transmission and reception for each channel.
It was necessary to separately provide a phase locked loop circuit PLL [Phase Locked Loop] including a CO [Voltage Controlled Oscillator] and a phase comparator, a filter, an amplifier, etc. for transmission and reception.

That is, in the transmission / reception circuit of the specific low-power radio equipment for data transmission shown in FIG. 2, assuming that this is the master unit, the transmission frequency of the first channel is 429.8125 MHz and the reception frequency is 449.7125 MHz. Therefore, when transmitting and receiving with the handset using this first channel,
The received high frequency signal of 449.7125 MHz received by the antenna 11 is distributed to the receiving circuit side by the duplexer 12 and sent to the mixer 14 via the amplifier 13. This mixer 1
4 is connected to the output of the phase locked loop circuit 15 including the VCO 15a and the phase comparator circuit 15b.
By mixing the 25 MHz oscillation signal and the received high frequency signal, the intermediate frequency signal of 21.7 MHz which is the difference between these frequencies is output through the band pass filter 16. Then, the frequency of this intermediate frequency signal is further converted to FSK [Freque
ncy Shift Keying] The original digital data can be reproduced by demodulating and converting the waveform into a square wave. When transmitting digital data, VC
Direct oscillation is performed by the phase locked loop circuit 17 including the O1 7a and the circuit 17b such as the phase comparator, and the high frequency transmission signal of 429.8125 MHz is sent out from the antenna 11 via the amplifier 18 and the duplexer 12. The same applies to the case where the transmission / reception circuit is a slave unit except that the specific frequency is different, and the respective frequencies in this case are shown in parentheses in the drawing.

As described above, the specific low-power radio equipment is capable of stably oscillating a frequency different for each channel, so that V
A phase locked loop circuit (PLL) composed of a circuit such as CO and a phase comparator is required, and the local oscillation frequency for converting the received high frequency signal into an intermediate frequency signal and the frequency of the direct oscillation for transmission are different. Had separately provided this phase-locked loop circuit as described above. This is also the case with specific low-power wireless equipment used in devices that transmit and receive analog signals, such as cordless phones.

[0006]

However, a phase locked loop circuit (PL) including a VCO and a circuit such as a phase comparator is used.
L) is relatively expensive and occupies some space in the equipment.

Therefore, in the conventional specific low-power radio equipment, the phase-locked loop circuit including the VCO and the phase comparator circuit separately provided for transmission and reception becomes an obstacle to product cost reduction. There has been a problem of hindering miniaturization of equipment.

[0008]

In order to solve the above problems, the present invention is different for each channel in a specific low power radio equipment in which the frequency difference between the transmission high frequency signal and the reception high frequency signal for each channel is constant. A phase-locked loop circuit that oscillates at a predetermined frequency and that includes a VCO and a circuit such as a phase comparator; a receiving circuit that converts a received high-frequency signal into an intermediate-frequency signal by mixing the oscillation signal of the phase-locked loop circuit; A VCXO that outputs a transmission signal at a predetermined oscillation frequency, and a transmission circuit that converts the output signal of this VCXO with the oscillation signal of the phase-locked loop circuit into a transmission high-frequency signal. There is.

[0009]

With the above construction, the received high frequency signal is mixed with the oscillation signal of the phase locked loop circuit in the receiving circuit and converted into the intermediate frequency signal. Therefore, even if the channel is changed, if the oscillation frequency of the phase locked loop circuit is changed accordingly, the receiving circuit can convert the received high frequency signal into an intermediate frequency signal having the same frequency as before the channel change.

In the transmission circuit, the output signal of the modulation circuit and the oscillation signal of the phase locked loop circuit are mixed and converted into a transmission high frequency signal. Therefore, when the channel is changed and the oscillation frequency of the phase locked loop circuit is changed accordingly, the frequency of the transmission high frequency signal is also shifted by the difference between the reception high frequency signal before and after the channel change. Therefore, as long as the difference between the frequencies of the transmission high-frequency signal and the reception high-frequency signal for each channel is constant, even if the oscillation frequency of the modulation circuit is fixed, the transmission circuit converts the transmission high-frequency signal of the correct frequency for all channels. can do. Moreover, in this way, in the modulation circuit, since the oscillation frequency for modulating the transmission signal may be fixed, VCXO [Vo
ltage Controlled Crystal Oscillator], etc., and an inexpensive and small oscillator can be used.

As a result, according to the specified low power radio equipment of the present invention, the phase locked loop circuit composed of the expensive and complicated VCO and the circuit such as the phase comparator can be used for both transmission and reception. Become.

[0012]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention and is a block diagram of a transmission / reception circuit in a specified low power radio equipment.

This embodiment describes a specific low power radio equipment for data transmission.

In this specific low power radio equipment, transmission / reception is performed between the master unit and the slave unit via the antenna 1. The antenna 1 is connected to a transmission circuit 3 and a reception circuit 4 via a duplexer 2, respectively. The duplexer 2 sends out the received high frequency signal received by the antenna 1 to the receiving circuit 4 without leaking to the transmitting circuit 3 side, and at the same time, transmits the transmitting high frequency signal sent from the transmitting circuit 3 to the receiving circuit 4 side. It is a directional filter that is designed to send to 1.

The receiving circuit 4 includes an amplifier 4a and a mixer 4
b and a SAW filter [Serface Acoustic Wave] 4c. The amplifier 4a is a high frequency amplifier circuit and includes a band pass filter that passes only the received high frequency signal of each channel. The mixer 4b receives the received high frequency signal that has passed through the amplifier 4a from the phase locked loop circuit 5
It is a circuit that mixes with the oscillation signal from. The SAW filter 4c is a bandpass filter that extracts only the intermediate frequency signal component of 21.7 MHz from the signal mixed by the mixer 4b.

The transmission circuit 3 includes a VCXO 3a and a mixer 3b.
And amplifier 3c. VCXO3a
Is an oscillation circuit using a crystal oscillator, and the oscillation frequency can be changed by about several kHz by changing the capacitance of the variable capacitance diode by the voltage applied to the control terminal. And this VCX
Digital data to be transmitted is input to the control terminal of O3a. Therefore, VCXO3a
Will also function as a modulation circuit that outputs a signal obtained by modulating digital data at the oscillation frequency of the crystal oscillator.
Since this VCXO 3a can perform stable oscillation by the crystal oscillator, it is not necessary to intentionally form a phase locked loop. The mixer 3b uses this VCXO3
This is a circuit for mixing the output signal of a with the oscillation signal from the phase locked loop circuit 5. The amplifier 3c is a high frequency amplifier circuit and includes a band pass filter that passes only the transmission high frequency signal of each channel.

The phase locked loop circuit 5 is an oscillating circuit composed of a VCO 5a and a phase comparator circuit 5b. VCO5
Reference numeral a is a voltage controlled oscillator circuit capable of arbitrarily changing the oscillation frequency itself by changing the capacitance of the variable capacitance diode provided in the tuning circuit according to the voltage applied to the control terminal. The phase comparator circuit 5b is
This is a circuit that constitutes a phase locked loop together with this VCO 5a. The oscillation frequency of the VCO 5a is compared with a reference frequency by a phase comparator, and the low frequency component of the error signal is amplified to VC
The oscillation frequency is stabilized by feedback to the control terminal of O5a. The phase comparator circuit 5b adjusts the frequency division ratio of the oscillation frequency of the VCO 5a and the frequency division ratio of the reference frequency by rewriting the internal data to change the oscillation frequency of the phase locked loop circuit 5. You can do it. When changing the channel, the phase comparator circuit 5
By rewriting the data of b, the oscillation frequency of the phase locked loop circuit 5 is changed.

The operation of the transmission / reception circuit having the above configuration will be described.

When the parent device performs transmission and reception using the first channel, the transmission frequency is 429.8125 MHz and the reception frequency is 449.7125 MHz. Further, in this case, the oscillation frequency of the phase locked loop circuit 5 is set to 471.4125 MHz. The oscillation frequency of the VCXO 3a in the transmission circuit 3 is fixed to 41.6 MHz regardless of the channel in both the master unit and the slave unit.

When the master unit uses the first channel as described above, the received high frequency signal of 449.7125 MHz received by the antenna 1 is sent to the receiving circuit 4 via the duplexer 2. In the receiving circuit 4, the received high frequency signal is input to the mixer 4b via the amplifier 4a. Then, the mixer 4b outputs the received high frequency signal from the phase locked loop circuit 5.
SAW filter 4c mixed with 471.4125MHz oscillation signal
The intermediate frequency signal of 21.7 MHz of these differences is output via. Actually, since signals of other frequencies are also received at the same time, the mixer 4b and the SAW filter 4c are used to select only the received high frequency signal of 449.7125 MHz to 21.7 M.
It will be converted to an intermediate frequency signal of Hz. In this way, the intermediate frequency signal output from the receiving circuit 4 is further frequency-converted into a low-frequency signal, FSK demodulated, and converted into a square wave to restore the original digital data.

When transmitting digital data, the digital data is transmitted to the VCX in the transmitting circuit 3.
Input to the control terminal of O3a. Then, this VCXO3
The a modulates the input digital data with an oscillation frequency of 41.6 MHz and sends it to the mixer 3b. The mixer 3b mixes the output signal of the VCXO 3a with the oscillation signal of 471.4125 MHz from the phase locked loop circuit 5. The difference between the output of the mixer 3b and the mixing frequency is 42.
Only the transmission high frequency signal of 9.8125 MHz is taken out through the amplifier 3c, sent to the duplexer 2 as the output of the transmission circuit 3, and transmitted from the antenna 1.

When the slave unit performs transmission / reception using the first channel, the oscillation frequency of the phase-locked loop circuit 5 is set to 408.1125 MHz, and the same operation is performed according to the frequency in the parentheses shown in the figure.

Here, the oscillation frequencies of the phase-locked loop circuit 5 in the transmission / reception circuits of the master unit and the slave unit are set so that the absolute value of the difference between the respective reception frequencies becomes equal to the frequency of the intermediate frequency signal. Is. The oscillation frequency of the VCXO 3a in the transmission circuit 3 is set so that the sum or difference with the oscillation frequency of the phase locked loop circuit 5 becomes equal to each transmission frequency.

That is, in the case of the first channel, the reception frequencies of the master and slave units are 449.7125 MHz and 429.8125 M, respectively.
Since the frequency of the intermediate frequency signal is 21.7 MHz, the oscillation frequency VCO of the phase locked loop circuit 5 of the parent device is
1 and the oscillation frequency VCO2 of the phase locked loop circuit 5 of the slave unit
Is determined based on Equation 1.

[0026]

[Equation 1] However, the oscillation frequencies VCO1 and VCO2 according to this equation 1
There are two solutions of each as shown in the equation 2.

[0027]

[Equation 2] Therefore, in this embodiment, the oscillation frequencies VCO1 and VCO2 are
Substituting the four combinations of the solutions of
Determine the oscillation frequencies X1 and X2 of the VCXO3a,

[0028]

[Equation 3] The oscillation frequency X1 of the master unit matches the oscillation frequency X2 of the slave unit, and the above-mentioned 41.6 MHz, which is three times the frequency of the crystal oscillator of 13.866 MHz, is selected as the oscillation frequency of the VCXO 3a. As the oscillation frequency of the phase locked loop circuit 5, the above 471.4125 MHz and 408.1125 MHz are selected as the combination of the oscillation frequencies VCO1 and VCO2 at this time. However, the specific frequency is not necessarily limited to the frequency selected here. When the transmission frequency or the reception frequency of the specific low power radio equipment is different, an appropriate oscillation frequency is selected according to each.

When the second and subsequent channels are used, the data of the phase comparator circuit 5b in the phase locked loop circuit 5 is rewritten to set the oscillation frequency to 1
It may be increased by 0.0125 MHz for each channel.

As a result, according to the specific low power radio equipment of this embodiment, the transmission circuit 3 and the reception circuit 4 share the phase locked loop circuit 5 including the expensive and complicated VCO 5a and the phase comparator circuit 5b. You will be able to.

[0031]

As is apparent from the above description, according to the present invention, one phase locked loop circuit including an expensive and complicated VCO and a circuit such as a phase comparator can be used for both transmission and reception. Therefore, the cost of the product can be reduced, and the size of the device can be reduced.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and is a block diagram of a transmission / reception circuit in a specific low power radio facility.

FIG. 2 shows a conventional example and is a block diagram of a transmission / reception circuit in a specific low power radio facility.

[Explanation of symbols]

 3 transmitter circuit 3a VCXO 3b mixer 4 receiver circuit 4b mixer 5 phase locked loop circuit 5a VCO 5b phase comparator circuit

Claims (2)

[Claims] 1. A specific low power radio equipment having a constant frequency difference between a transmission high frequency signal and a reception high frequency signal for each channel, and a VC oscillating at a predetermined frequency different for each channel.
A phase locked loop circuit composed of O and a circuit such as a phase comparator, a receiving circuit for converting a received high frequency signal into an intermediate frequency signal by mixing it with an oscillation signal of the phase locked loop circuit, and a fixed predetermined oscillation frequency. A specific low power radio having a VCXO which outputs a transmission signal, and a transmission circuit which converts the output signal of the VCXO with the oscillation signal of the phase locked loop circuit into a transmission high frequency signal. Facility. 2. The specific low power radio equipment according to claim 1, wherein the VCXO also serves as a modulation circuit for outputting a signal modulated at a predetermined oscillation frequency.