JP3114183B2 - Receiving machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a receiver such as a paging receiver used for mobile communication.

[Conventional technology]

As shown in FIG. 2, a conventional receiver of this type includes an antenna 1 built in a case, an RF amplifier 2 for amplifying an RF signal induced by the antenna 1, and an amplifier amplified by the RF amplifier 2. A first filter 3 for filtering the RF signal, a local oscillator 4, a second filter 5 for filtering a local signal from the local oscillator 4, and the first and second filters. A mixer 6 for mixing the RF signals from the filters 3, 5 and the local oscillation signal to obtain an intermediate frequency signal, and a third filter 7 for filtering the intermediate frequency signal
And an intermediate frequency amplifier 8 for amplifying the intermediate frequency signal and limiting the amplitude, and a demodulator 9 for demodulating the intermediate frequency signal into a baseband signal.

[Problems to be Solved by the Invention] Incidentally, in such a receiver, since an antenna is built in, a case cannot be formed of a metal case. For this reason, the receiver may receive RF signals induced by other than the antenna together,
Due to this, there is a problem that complicated characteristics are exhibited and desired reception characteristics cannot be obtained.

As the induced RF signal, for example, since the first and second filters 3, 5 and the mixer 6 are connected through wiring on a printed circuit board, each part has the same There is not an electric potential but an induced voltage generated between them. Therefore, it is difficult to sufficiently exert the original function of the first filter 3 for removing this kind of interference wave, and the reception characteristics are deteriorated.

An object of the present invention is to provide a receiver that suppresses the induction of such an RF signal and prevents deterioration of reception characteristics.

[Means for solving the problem]

A receiver according to the present invention includes, in a case formed of a nonmetallic material, an antenna, an RF amplifier for amplifying an RF signal induced by the antenna, and a first filter for filtering the RF signal amplified by the RF amplifier. A filter, a local oscillator, a second filter for filtering a signal from the local oscillator, and the filtered RF
A mixer for mixing the signal and the signal from the local oscillator, a third filter for filtering an intermediate frequency signal output from the mixer, an intermediate frequency amplifier for amplifying the filtered intermediate frequency signal, A demodulator for demodulating a baseband signal from the amplified intermediate frequency signal is provided, and the first filter, the second filter, and the mixer are covered with one shield case.

[Action]

According to the present invention, the filter case, the mixer and the wiring connecting these are shielded from the external electric field by the shield case, so that the induction of the RF signal in each of these parts is prevented,
Deterioration of reception characteristics is prevented.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.
The same parts as those in the conventional configuration shown in FIG. 2 are denoted by the same reference numerals. That is, in the figure, 1 is an antenna built in a case of a receiver, 2 is an RF amplifier, 3 is a first filter, 4 is a local oscillator, 5 is a second filter, and 6 is a mixing filter. , 7 is a third filter, 8 is an intermediate frequency amplifier, and 9 is a demodulator. Of these, each part except the antenna 1 is usually assembled on a printed circuit board, and then housed together with the antenna 1 in a case formed of resin or the like.

The first filter 3, the second filter 5, and the mixer 6 are disposed at positions close to each other on the printed circuit board. The area including the wiring that interconnects the shield case 10 such as a metal case
Covered by

According to this configuration, the RF signal induced in the antenna 1
The signal is amplified by the RF amplifier 2, enters the first filter 3 in the shield case 10, is filtered, and is input to the mixer 6. On the other hand, the local signal from the local oscillator 4 enters the second filter 5 in the shield case 10, is filtered, and then input to the mixer 6. The RF signal and the local signal are mixed by a mixer 6, converted into an intermediate frequency signal, input to a third filter 7 for filtering the intermediate frequency outside the shield case 10, and after being filtered, the intermediate frequency Input to the amplifier 8. The intermediate frequency amplifier 8 amplifies the intermediate frequency signal, limits the amplitude, and leads the demodulated signal to a demodulator 9 for demodulation. The demodulator 9 demodulates and uses the baseband signal.

Further, here, the first filter 3, the second filter 5, and the mixer 6 are covered with the shield case 10, so that
The inside of the shield case 10 has the same potential, and even when the external electric field affects the receiver, the first and second filters 3, 5 and the mixer 6, and the wiring connecting each of them, are protected from the external electric field. It becomes a shielded state, and the voltage induced in each of these parts becomes extremely small. Therefore, it is possible to prevent reception characteristics from being degraded due to this type of induced voltage, and to obtain a receiver having stable characteristics.

In particular, when SAW (elastic wave) filters are used as the first and second filters 3, 5, it becomes possible to mount the filters 3, 5 and the mixer 6 in a small can case.
The effect is great.

〔The invention's effect〕

As described above, according to the present invention, the first filter, the second filter, and the mixer of the receiver having the antenna built in the case formed of the nonmetallic material are integrated in the case. Since it is covered with two shield cases, the filter, the mixer, and the wiring connecting them are shielded from the external electric field by the shield case, and the RF signal is not induced in these parts to prevent the deterioration of reception characteristics. be able to.

Therefore, in the mobile communication field where the demand for radio waves is increasing more and more in the future, the deterioration of characteristics due to the influence of interference waves and the like becomes apparent.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a receiver according to the present invention.
The figure is a block diagram of a conventional receiver. DESCRIPTION OF SYMBOLS 1 ... Antenna, 2 ... RF amplifier, 3 ... 1st filter, 4 ... Local oscillator, 5 ... 2nd filter, 6 ... Mixer, 7 ... 3rd filter Wave device, 8 ... Intermediate frequency amplifier, 9
... demodulator, 10 ... shield case.

Claims (1)

(57) [Claims] An antenna, an RF amplifier for amplifying an RF signal induced by the antenna, and a first filter for filtering the RF signal amplified by the RF amplifier are provided in a case formed of a non-metallic material. Filter, a local oscillator, a second filter for filtering a signal from the local oscillator, a mixer for mixing the filtered RF signal with a signal from the local oscillator, and an output from the mixer. A third filter for filtering the intermediate frequency signal, an intermediate frequency amplifier for amplifying the filtered intermediate frequency signal, and a demodulator for demodulating a baseband signal from the amplified intermediate frequency signal; A receiver, wherein the first filter, the second filter, and the mixer are covered with one shield case.