JPH0273728A - Digital mobile radio equipment - Google Patents

Abstract

PURPOSE:To attain a simple and small-sized circuit with economy and low power consumption by using a reference oscillator for frequency synthesizer for a reception station call signal and a transmitter carrier source and a recovered carrier oscillator used for a synchronizing detection circuit for a receiver in common. CONSTITUTION:The frequency synthesizer consists of a voltage controlled crystal oscillator(VCOX) 18, a PLL circuit 7 and a voltage controlled oscillator(VCO) 6. Then the free oscillating frequency of a reference oscillator 18 in the frequency synthesizer is made nearly equal to a receiver nominal intermediate frequency. Thus, a local oscillation signal corresponding to the reception desired channel is fed to a mixer 10 from the frequency synthesizer, the desired channel is received and since the frequency of the reference oscillator 18 is nearly equal to the receiver nominal intermediate frequency, the oscillator is used for the synchronizing detection recovered carrier and the demodulation of the received data is attained. Thus, a small sized device is attained and the cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mobile radio device applied to a car telephone device or the like using a digital modulation method.

(Prior Art) FIG. 2 shows the configuration of a conventional digital mobile radio device. In FIG. 2, 1 is a modulation input terminal, which is connected to a quadrature modulator 2. In FIG. 3 is quadrature modulator 2
4 is an antenna duplexer for sharing one antenna with a transmitter/receiver, 5 is an antenna, and 6 is a voltage controlled oscillator (
7 is a phase locked circuit (PLL circuit), 8 is a reference oscillator, and the VCO 6, PLL circuit 7, and reference oscillator 8 constitute a frequency synthesizer. 9 is AFC
10 is a frequency converter (mixer) of the receiver, 11 is an intermediate frequency amplifier (IFAMP), 12 is a synchronous detection circuit, 13 is a demodulation output terminal, 14 is a carrier wave regeneration circuit such as a Costas circuit or an inverse modulation circuit, 15 is a carrier wave oscillator.

Next, the operation of the above conventional example will be explained. In FIG. 2, the reference oscillator 8 oscillates at a substantially specified frequency, and the VCO
6. PLL circuit 7. Using a frequency synthesizer constituted by a reference oscillator 8, the VCO 6 supplies the mixer 10 with a local oscillation frequency such that a specified channel frequency can be received. Here, when the desired channel frequency is received by the antenna 5, it is mixed with the local oscillation frequency from the vCO 6 by the mixer 10 via the antenna duplexer 4 to obtain an intermediate frequency. After this intermediate frequency signal is amplified by IFAMP II, it is applied to a synchronous detection circuit 12 and a carrier wave regeneration circuit 14, and a carrier wave oscillator 15 generates a reference carrier wave equal to the frequency of the intermediate frequency signal.

In addition, in general, a carrier wave regeneration circuit 14, a carrier wave oscillator 15
The synchronous detection circuit 12 constitutes a Costas circuit or an inverse modulation circuit, but since this is a well-known technique, a detailed explanation thereof will be omitted here. The reference carrier wave generated by the carrier wave oscillator 15 is applied to the synchronous detection circuit 12, and a demodulated digital signal is output from the demodulation terminal 13. Further, the time base signal broadcast from the base station is demodulated by the synchronous detection circuit 12 and then applied to the AFC circuit 9 to accurately control the frequency of the reference oscillator 8 to the nominal frequency.

(Problem to be Solved by the Invention) However, the conventional digital mobile radio device described above requires a carrier wave regeneration circuit 14 and two types of oscillators, the reference oscillator 8 and the carrier wave oscillator 15, and the circuit is complicated.
There were problems in that it was large in size, high in cost, and consumed a lot of gravity.

The present invention solves the above-mentioned conventional problems, and aims to provide an excellent digital mobile radio device that can reduce the size and cost of the device.

(Means for Solving the Problems) In order to achieve the above object, the present invention makes the oscillation frequency of the reference oscillator of the frequency synthesizer match the nominal intermediate frequency of the receiver, and uses it as a regenerated carrier wave for synchronous detection.
AFC is applied to this reference oscillator using the time base signal broadcast from the base station.

The oscillation frequency of the reference oscillator is precisely controlled.

(Function) The present invention has the following effects due to the above configuration. That is, the free oscillation frequency of the reference oscillator in the frequency synthesizer is approximately equal to the nominal intermediate frequency of the receiver, and therefore, the frequency synthesizer supplies the local oscillation frequency signal corresponding to the desired reception channel to the mixer to receive the desired channel. Can be done. Furthermore, since the frequency of the reference oscillator is approximately equal to the receiver intermediate frequency, it can be used as a regenerated carrier wave for coherent detection, and it is possible to demodulate received data. Using the time base signal in this received data, AFC is applied to the base and oscillator.
Since the frequency of the reference oscillator is controlled to be exactly equal to the nominal intermediate frequency of the receiver, it can be used as a signal equivalent to a regenerated carrier wave for coherent detection.

(Embodiment) FIG. 1 shows the configuration of an embodiment of the present invention. In FIG. 1, the same reference numerals as in FIG. 2 have the same functions.

Reference numeral 18 denotes a voltage controlled crystal oscillator (vcXo) for use as a reference oscillator for a frequency synthesizer and a regenerated carrier wave for synchronous detection, the oscillation frequency of which is controlled by an external control potential.

Next, the operation of this embodiment will be explained.

VCX, 018 oscillates at approximately the receiver's nominal intermediate frequency, and this Vcxota, the PLL circuit 7, and the VCO 6 constitute a frequency synthesizer. Vcxota is
It operates as a reference oscillator for this frequency synthesizer.

On the other hand, the PLL circuit 7 controls the VCO 6 so that the oscillation frequency of the VCO 6 oscillates at a local oscillation frequency that approximately corresponds to the reception channel frequency. Therefore, when the antenna 5 receives a radio wave of the desired reception channel, the radio wave passes through the antenna duplexer 4, is mixed with the local signal from the VCO 6 at the mixer 10, and is converted into an intermediate frequency signal. After this intermediate frequency signal is amplified by IFAMPII, the synchronous detection circuit 1
2, the signal of Vcxota whose oscillation frequency is approximately equal to the intermediate frequency is used for detection and demodulation. Here, the AFC circuit 9 uses the time base signal radiated from the reference station.
By controlling the frequency of Vcxo exactly equal to the nominal intermediate frequency of the receiver, AFC of the mobile radio device is established, and the signal of vcxo18 becomes exactly equivalent to the regenerated carrier wave for coherent detection.

In addition, in the process of establishing AFC synchronization, Vcxot
Since the frequency of a is not accurate, the bit error rate deteriorates to some extent, but the degree of this is so slight that the time base signal can be correctly demodulated by using waveform equalization technology or an error correction code.

Incidentally, as shown in FIG. 1, it is of course possible to use the signal of the VCO 6 as a carrier wave source for the transmitter.

(Effects of the Invention) As is clear from the above embodiments, the present invention shares the reference oscillator for the frequency synthesizer of the receiving station oscillation signal and the transmitter carrier wave source, and the regenerated carrier oscillator used for the synchronous detection circuit of the receiver. This has the advantage of simplifying the circuit, making it smaller, making it more economical, and reducing power consumption.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a digital mobile radio device according to the present invention;
FIG. 2 is a block diagram of a conventional digital mobile radio device. 1...Modulation input terminal, 2...Quadrature modulator, 3...
・・Power amplifier, 4 ・・Antenna duplexer, 5・
・・Antenna, 6 ・・Voltage controlled oscillator (VCO)
, 7 ・Phase synchronization (PI, L) circuit, 9 ・・A
FC circuit, 10 mixer, 11... IFAM
P, 12... Synchronous detection circuit, 18... Voltage controlled crystal oscillator (v c x o).

Claims (1)

[Claims] AFC using the time base signal broadcast from the base station
an oscillator whose oscillation frequency is controlled by a means for making the frequency of the oscillator equal to a nominal receiver intermediate frequency and making the oscillator a reference for a frequency synthesizer that is a receiver local oscillator signal source and a transmitter carrier wave source; A digital mobile radio device characterized in that it is used as an oscillator and as a reference carrier wave oscillator for demodulation of a receiver synchronous detection circuit.