JPS6219006Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a circuit configuration of a converter with a high frequency amplifier that is most suitable for use in ultra-compact radios such as radio wristwatches.

In recent years, the miniaturization of electronic devices has been remarkable, and ultra-compact receivers that can be built into wristwatches are being realized. Traditionally, when you try to put a radio into a wristwatch, it becomes too big.

Performance deteriorates.

Battery life will be shortened.

One of these problems arose and hindered its practical application. FIG. 1 shows a conventional example of a converter circuit, and since it is well known, detailed explanation will be omitted. In the case of the conventional example shown in Fig. 1, the performance is satisfactory, but 3
The disadvantage is that the external size becomes large because the continuous variable capacitor 2 is used and a high frequency transformer is required.
Also, in order to make the external size smaller, if high-frequency amplifiers are omitted, the performance will decrease.Furthermore, ultra-compact radios have smaller antennas than pocket radios, etc., and the sensitivity decreases accordingly, making it impossible to maintain practical performance. It was hot. Furthermore, if the radio circuit including the high-frequency amplifier is made into an IC (integrated circuit), it becomes possible to downsize the radio circuit, but on the other hand, the power consumption of the circuit increases. This is because high-frequency amplification transistors must have ultra-low noise and a high cut-off frequency. This is because, with current technology, it is difficult to reduce the current by designing a device that absorbs variations in the IC process and can be produced at a high yield.
On the other hand, the batteries that go into ultra-compact wristwatch-sized radios are small and have low capacity. Using ICs in this way had the disadvantage that power consumption did not decrease and battery life was shortened.

Next, we will discuss the problems in miniaturizing the circuit. Figures 2 and 3 are also conventional examples of converter circuits that can be miniaturized.
This is changed to CR bond. Here, 4 is a local oscillator coil, and 5 is a radio IC that operates with low power. Since the mixed oscillation amplifier circuit of the radio IC 5 has one input, the received high frequency signal and the local oscillation signal are combined in series by the tertiary coil of the local oscillation transformer and input.

As a result, the local transformer 4 has 6 terminals (the standard is 5
The disadvantage is that the terminals are standard) and non-standard parts are required. In addition, in the FM mixed oscillation circuit shown in FIG. 3, the signal is fed back from the local oscillator coil on the output side to the input via a capacitor, and further synthesized in parallel with the received high frequency signal and input. However, when the reception frequency ranges over a wide range such as in the medium wave band, the impedance of the feedback capacitor changes depending on the frequency and the oscillation intensity changes, so there is a drawback that the sensitivity changes or reception becomes impossible depending on the frequency.

In order to eliminate the above-mentioned drawbacks, this invention aims to provide an ultra-compact radio with practical performance by realizing a converter circuit that can be combined with a low-power radio IC that has a simplified circuit. shall be.

A detailed explanation will be given below based on the drawings. Figure 4 shows an embodiment of the present invention, where 1 is a bar antenna and 3 is a 2
5 is a low power consumption radio IC with a simplified circuit, 6 is a local oscillator coil, 7 is an IFT (intermediate frequency transformer), and 8 is a high cut-off frequency, low noise transistor for high frequency amplification. , 9 are transistors for mixed oscillation built into the radio IC 5.

Next, the operation will be explained.

Bar antenna 1 takes out the necessary high frequency signal,
This is amplified by transistor 8. The high frequency signal is synthesized in series with the local frequency by the feedback winding of the local coil 6 and input to the transistor 9. The output of the collector of the transistor 9 passes through the IFT 7 to extract an intermediate frequency component, and the local oscillator coil 6 extracts the local frequency component. Note that the resistor 11 provides bias to the transistor. In this way, a resistance-coupled converter with a high-frequency amplifier is realized. IFT7
Since the local oscillator coil 6 has five terminals or less, a standard ultra-small coil can be used. Furthermore, ultra-miniaturization is possible by using a trackingless double variable capacitor. The intermediate frequency taken out from the IFT 7 is input to the radio IC 5, where intermediate frequency amplification, detection, and low frequency amplification are performed.

According to the present invention, (1) the high frequency amplification section has a high gain (20~
30dB).

(2) It is compatible with radio ICs that perform mixed oscillation using a single amplifier circuit, which is often found in low-power radio ICs, so there are fewer restrictions on IC implementation, and ultra-compact dual variable capacitors and ultra-compact 5 Since terminal IFT and local coils can be used, the radio receiver can be made smaller.

(3) Since the radio IC does not include a transistor for high-frequency amplification with low frequency and low noise, it is possible to reduce the power consumption of the radio IC.

[Brief explanation of the drawing]

1, 2, and 3 are conventional examples of converter circuits, and FIG. 4 is a circuit diagram showing an embodiment of the present invention. 1... Bar antenna, 2... Triple variable capacitor, 3
...Double variable capacitor, 4, 6...Local coil, 5...
...radio IC, 7...IFT, 8, 9...transistor, 10, 11...resistor.

Claims (1)

[Scope of utility model registration request] A high-frequency amplifier with a resistive load, a mixed oscillation circuit that performs local oscillation and mixing in the same amplifier circuit, an antenna tuning coil, an intermediate frequency transformer with 5 or less terminals, and a local oscillator transformer with 5 or less terminals, and a capacitor from the output of the high-frequency amplifier. The signal taken out by the coupling passes through the secondary winding for oscillation feedback of the local oscillation transformer, so that the local oscillation signal and the output of the high frequency amplifier are combined in series, and then connected to the input of the transistor of the mixed oscillation circuit. , On the other hand, the output of the transistor of the mixed oscillation circuit is connected to the tap of the primary side tuning winding of the local oscillation transformer after passing through the intermediate frequency transformer, and is connected to one end of the tuning winding of the local oscillation transformer. An ultra-compact radio converter characterized in that one end of the antenna tuning coil and a ground wire are connected to a power source.