JPH06164491A - Digital portable telephone set - Google Patents

Abstract

PURPOSE:To obtain a superior isolation characteristic by providing two systems of a local oscillator and a synthesizer circuit and inverting the phase of the other local oscillation signal by a phase inverter and adding it by an adder when the frequency conversion is performed by eitner of local oscillation signals, CONSTITUTION:For example, in a slot #AT, a 1st local oscillator 27 is locked to the prescribed oscillation frequency in the slot #AT by a synthesizer circuit 34 and sent to an adder 38. In a 2nd local oscillator 28, a synthesizer circuit 35 is operated to apply frequency lock to the prescribed oscillation frequency in a slot #C and the signal of the 2nd local oscillator 28 is sent to the adder 38. In this case, as the signal of the 2nd local oscillator 28 is not required, the unrequired signal is sent to the phase inverter 37 by connecting a switch means 36 to a contact point (b) by a control signal from the control circuit. Thus obtained opposite phase signal is sent to the adder 38. Thus, unnecessary oscillation signals can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital mobile phone such as a car phone, a mobile phone, a cordless phone or the like, which communicates using a plurality of time-divided communication slots.

[0002]

2. Description of the Related Art A digital cordless telephone is one of digital mobile phones that employ a time division multiplexing (TDM) method for multiplexing a transmission signal and a reception signal on a time axis. In this digital cordless telephone, one frame is divided into eight as shown in FIG. 4, which is composed of four transmission (Tx) slots and four reception (Rx) slots. When the transmission slot #AT is used, the reception slot is #. AR is used to transmit and receive four calls at one frequency. (TDMA / TDD) The wireless unit of a telephone handset corresponding to such a transmission method has conventionally been configured as shown in FIG. In FIG. 5, a 1.9 GHz band signal received by the antenna 1 is amplified by the reception amplifier 3 via the antenna switch 2 for switching between transmission and reception, and then generated by the first local oscillator 4. A local oscillation signal of 65 GHz and a first intermediate frequency converter 5 for receiving 250
Converted to IF frequency of MHz. Then, via the first intermediate amplifier 6, the 2 generated by the second local oscillator 7
The local oscillation signal of 40 MHz and the second intermediate frequency converter for reception 8 are frequency-converted, and further, via the second intermediate amplifier 9, the local oscillation signal of 9.6 MHz generated by the third local oscillator 10 and the reception first signal. 3 The frequency is converted by the intermediate frequency converter 11, and down-converted by the demodulator 12 to a frequency at which digital demodulation is possible.

For transmission, a signal digitally modulated by the modulator 13 is converted into a first intermediate frequency converter 1 for transmission.
4. The first intermediate amplifier 15, the second intermediate frequency converter 16 for transmission, and the second intermediate amplifier 17 sequentially up-convert and then generate 1.65 GH generated by the first local oscillator 4.
The local oscillation signal of z is converted into a frequency of 1.9 GHz band by the third intermediate frequency converter for transmission 18, and the transmission amplifier 1
9. Transmitted from the antenna 1 via the antenna switch 2.

The first and second local oscillators 4, 7 have loop filters 20, 22 and P for controlling the oscillation frequency.
It is connected to synthesizer circuits 24 and 25 composed of LL circuits 21 and 23, and detects the phase of the oscillation frequencies of the first and second local oscillators 4 and 7, and locks them at a predetermined oscillation frequency to keep the frequency stable. It operates and selects a predetermined transmission / reception frequency. 26 is a crystal oscillator.

In the case of a digital cordless telephone, the transmission and reception frequencies are the same, so if the first and second local oscillation frequencies are the same for transmission and reception, the first and second local oscillators 4 and 7 are shared for transmission and reception. can do. TDMA
Since each burst time-divided by / TDD does not occur within the same time as reception and transmission, it can be dealt with by turning off the circuit operation on the Rx side and the Tx side. As a method of turning off the circuit operation corresponding to TDMA, the frequency converters 5, 18 and 8, 16 for transmission and reception are used.
It is possible to consider a method of turning on / off the above operation in correspondence with each burst.

However, when a single terminal device is capable of transmitting and receiving a plurality of slots as in the case of a master unit of a digital cordless telephone (when transmitting in four slots),
It is necessary to change the local oscillation frequency in each of the four slots. In this case, as shown in FIG. 4, between each slot,
A predetermined blank period is set, and it is necessary to change the oscillation frequency of the first local oscillator 4 at high speed during this blank period.

However, since the blank period is extremely short and it is difficult to change the frequency in such a short time, the circuit configuration becomes complicated in the configuration of the above-mentioned prior art.

The present applicant has already applied for a digital mobile phone that solves the above problems (Japanese Patent Application No. 4-2).
99954). This conventional technique will be described with reference to FIG.

In the figure, 27 is a first local oscillator and 28 is a local oscillator.
Is a second local oscillator, and each local oscillator 27, 28
Is a loop filter for controlling the oscillation frequency.
2 and the synthesizer circuits 34 and 35 composed of the PLL circuits 31 and 33. Reference numeral 29 selects one of the signals generated by the first local oscillator 27 and the second local oscillator 28, and uses the receiving first intermediate frequency converter 5 for reception and the transmitting third intermediate frequency converter for transmission. A method by means of switching means for delivery to the container 18 is conceivable.

Next, the operation will be described with reference to FIG. First, the first local oscillator 27 is frequency-locked by the synthesizer circuit 34 to a predetermined oscillation frequency in slot #AT, and is sent to the transmitting third intermediate frequency converter 18 by the switching means 29. Since each synthesizer circuit 34, 35 is not a high speed synthesizer circuit, it takes time to lock the frequency of the local oscillation frequency. Therefore, the first local oscillator 27 does not transmit the slot #BT,
The synthesizer circuit 34 operates so that a predetermined oscillation frequency of C is frequency-locked. Synthesizer circuit 34
Operates by using the time of slot #BT to drive it to a predetermined oscillation frequency of slot #CT. The slots #BT and #DT correspond to each other by the second local oscillator 28 and the synthesizer circuit 35, and are sent to the transmitting three intermediate frequency converter 18 by the switching means 29.

Similarly, when receiving #AR to #DR,
The first local oscillator 27 and the second local oscillator 28 are alternately switched, and the switching unit 29 sends a signal of a predetermined frequency to the first intermediate frequency converter for reception. Although the synthesizer circuit to be used operates at a low speed, it needs to have a lock-up time for locking the frequency to a predetermined oscillation frequency within one slot time (0.625 mS). In this way, two local oscillators corresponding to each slot are selected and alternately switched to be used, which corresponds to all slots.

[0012]

However, in such a conventional technique, if the isolation characteristic of the switching means 29 for selecting each local oscillation circuit is insufficient,
There are apparently two local oscillating signals, which become an unwanted radiation component of the terminal device and pose a problem.

[0013]

In order to solve the above problems, a digital mobile phone according to the present invention includes a receiving amplifier for amplifying a received radio wave received from an antenna, and first and second oscillators for oscillating a predetermined local oscillation signal. A second local oscillator circuit, first and second synthesizer circuits that control the oscillation frequencies of the first and second local oscillator circuits, and a signal amplified by the reception amplifier from the local oscillator circuit. An intermediate frequency converter for reception for frequency conversion into an IF signal by means of an intermediate frequency converter for transmission, for frequency conversion of a transmission IF signal by means of a signal from the local oscillation circuit, and for transmitting a frequency-converted transmission signal from an antenna In a digital mobile phone having a transmission amplifier that amplifies the signal in a time division multiplex manner,
And switch means for selecting one of the signals from the second local oscillator circuit, a phase inverter for inverting the phase of the signal selected by the switch means, and the first and second local oscillator circuits. Is added to the signal from the phase inverter.

[0014]

In the present invention, two systems of a local oscillator and a synthesizer circuit are provided, and when frequency conversion is performed by either one of the local oscillation signals, the phase of the other local oscillation signal is inverted by the phase inverter and added by the adder. By doing
Unwanted oscillation signals are removed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a block of a radio section of a digital cordless telephone according to the present invention. The same components as those of the conventional technique are designated by the same reference numerals and the description thereof will be omitted.

In the figure, reference numeral 36 is a switch means having contacts a and b for selecting an unnecessary local oscillation signal,
Reference numeral 37 is a phase inverter that creates an anti-phase signal from an unnecessary local oscillation signal, and 38 is an adder circuit that adds the unnecessary local oscillation signals obtained from the first local oscillator 27, the second local oscillator 28, and the phase inverter 36. The signal obtained by the adder circuit 38 is sent to the first intermediate frequency converter 5 for reception at the time of reception and to the third intermediate frequency converter 18 for transmission at the time of transmission.

Next, the operation of the present invention will be described with reference to FIG. In the slot #AT, the first local oscillator 27 is frequency-locked by the synthesizer circuit 34 to the predetermined oscillation frequency in the slot #AT and is sent to the adder circuit 38. The second local oscillator 28 synthesizes the synthesizer circuit 3 so as to lock the predetermined oscillation frequency of the slot #C.
5 operates, and the signal of the second local oscillator 28 is sent to the adder circuit. Here, since the signal of the second local oscillator 28 becomes an unnecessary signal, the unnecessary signal is sent to the phase inverter 36 by connecting the switch means 36 to the contact b by the control signal from the control circuit (not shown). The anti-phase signal obtained by the phase inverter 37 is sent to the adding circuit 38. The adder circuit 38 causes the first local oscillation signal and the second local oscillation signal
By adding the local oscillation signal and the second local oscillation anti-phase signal, the second local oscillation signal and the second local oscillation anti-phase signal are canceled because the phase is shifted by π at the same frequency and the signal is Only the one local oscillation signal is output, and the first local oscillation signal is sent to the third intermediate frequency converter for transmission 18. In the slot #BT, the second local oscillator 28 is frequency-locked by the synthesizer circuit 35 to the predetermined oscillation frequency in the slot #AT and is sent to the adder circuit 38.
The signal of the first local oscillator 27, which becomes an unnecessary signal, is added by the adding circuit 3
8 and at the same time is selected by the contact a of the switch means 36, an anti-phase signal is obtained by the phase inverter 37 and sent to the adder circuit 38. The first local oscillation signal and the first local oscillation anti-phase signal are canceled by the adding circuit 38 and the second local oscillation signal
The local oscillation signal is sent to the transmitting third intermediate frequency converter 18. In slot #CT, as in slot #AT, the first local oscillator 27 and the synthesizer circuit 34 correspond to each other, and the second local oscillator 28 becomes an unnecessary signal. Therefore, the second local oscillation signal and the second local oscillation anti-phase signal Remove by adding. The slot #DT operates in the same manner as the slot #BT.

Similarly, when receiving #AR to #DR,
The first local oscillator 27 and the second local oscillator 28 are alternately switched to send a signal of a predetermined frequency in each slot to the receiving first intermediate frequency converter. In this way, the unnecessary signal can be removed by adding the opposite-phase signal of the unnecessary signal to the unnecessary signal, and high isolation characteristics can be obtained.

FIG. 3 is a diagram for specifically removing the unnecessary signal by adding the unnecessary signal and the unnecessary antiphase signal. Figure 3 (A)
3B is an unnecessary signal, and FIG. 3B is an unnecessary anti-phase signal having the same frequency as the unnecessary signal and a phase shifted by π. It is (C) of FIG.

[0020]

As described above, in the digital portable telephone according to the present invention, when the local oscillator and the synthesizer circuit of two or more systems are used, the unnecessary signal of the local oscillator is removed by adding the unnecessary signal and the unnecessary antiphase signal. As a result, high isolation characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a wireless unit of a digital mobile phone according to the present invention.

FIG. 2 is a diagram for explaining the operation of the present invention.

FIG. 3 is a diagram showing removal of unnecessary signals for explaining the operation of the present invention.

FIG. 4 is a diagram showing a frame structure of a digital cordless telephone system.

FIG. 5 is a block diagram showing a wireless unit of a digital mobile phone according to a conventional technique.

FIG. 6 is a block diagram showing a wireless unit of a digital mobile phone according to a conventional technique.

FIG. 7 is a diagram showing an operation of a conventional digital mobile phone.

[Explanation of symbols]

 1 Antenna 3 Reception Amplifier 5 Reception Intermediate Frequency Converter 18 Transmission Intermediate Frequency Converter 19 Transmission Amplifier 27 First Local Oscillation Circuit 28 Second Local Oscillation Circuit 29 Switching Means 34 First Synthesizer Circuit 35 Second Synthesizer Circuit 36 Switching Means 37 Phase Inverter 38 Adder Circuit

Claims (1)

[Claims] 1. A receiving amplifier for amplifying a received radio wave received from an antenna, and a first local oscillator for oscillating a predetermined local oscillation signal.
And a second local oscillator circuit, first and second synthesizer circuits for controlling the oscillation frequencies of the first and second local oscillator circuits, and a signal amplified by the receiving amplifier from the local oscillator circuit. An intermediate frequency converter for reception that frequency-converts an IF signal by a signal, an intermediate frequency converter for transmission that frequency-converts a transmission IF signal by a signal from the local oscillation circuit, and a transmission signal that has been frequency-converted is transmitted from an antenna In a digital mobile phone having a transmission amplifier that amplifies in order to make a call by a time division multiplexing system, a switch means for selecting one of the signals from the first and second local oscillation circuits, and the switch means A phase inverter for inverting the phase of the selected signal, the signals from the first and second local oscillator circuits, and the phase Digital mobile phone, characterized in that it comprises an adder circuit for adding signals from the rolling device.