JPS63246020A - Tuner - Google Patents

Abstract

PURPOSE:To eliminate the need for an externally mounted LC circuit by providing a local oscillator circuit outputting a pulsating current frequency appearing at the terminal voltage of an impedance element in series with the power supply of an inverter ring oscillator as a local oscillation frequency. CONSTITUTION:An RF frequency signal from an antenna 1 is mixed with a local oscillation signal from a local oscillator 5 by a mixer circuit 3 via an RF amplifier 2 and used as an IF signal, and outputted via an IF filter 20 and an IF amplifier 4. On the other hand, a converter 6 outputs a voltage Vc according to the frequency data from a memory 7 operated externally. The output current of an inverter ring oscillator 51 of the local oscillator 5 is controlled by the voltage Vc, a pulsating current is extracted by a current control FET as a voltage and fed to the mixer 3 via a BPF 53 and an amplifier 54.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to tuners for televisions, radios, radios, etc.

[Conventional technology]

Traditionally, superheterodyne tuners are
A local oscillator using an LC resonant circuit was used.

[Problem that the invention seeks to solve]

Even today, when electronic devices are becoming smaller and one-chip FM tuners have appeared, only the resonant LC circuit for the local oscillator has to be externally connected, which remained a problem until the end. . Furthermore, if the local oscillator is configured with a simple CMOS inverter in order to achieve a completely monolink system, a sufficiently high frequency cannot be obtained, and there is a problem in that if the frequency is increased, the current consumption increases.

The present invention uses an inverter in a local oscillator, operates its current consumption waveform as a local oscillator signal, and aims to achieve monolithic design and reduce the number of LC components.

[Means for solving problems]

In order to solve such problems, the tuner of the present invention includes an inverter ring oscillator in which an odd number of CMOS inverters are connected in series in a ring shape, and an impedance element connected in series to the power supply of the inverter ring oscillator. This device is characterized by being equipped with a local oscillator that eliminates the need for an external LC circuit by outputting the pulsating current frequency appearing at the terminal as a local oscillation frequency.

〔Example〕

FIG. 1 is a circuit block diagram showing an embodiment of the tool of the present invention. 1 is an antenna, 2 is an RF amplifier, 6 is a mixing circuit, 20 is an IP filter, 4 is an intermediate frequency amplifier, 5 is a local oscillator which is a feature of the present invention, 6 is a D/A converter, and 7 is a memory. RF from antenna 1
The frequency signal is amplified by the RF amplifier 2, further mixed with the local oscillator signal from the local oscillator 5 by the mixing circuit 6 to become an intermediate frequency signal (hereinafter referred to as the IF multiplied signal), passed through the IF filter 20, and finally The signal is then amplified by the intermediate frequency amplifier 4 and output. This IP multiplied signal detection circuit (not shown) converts the signal into a video signal or other signal.

The local frequency is controlled by a tuning voltage Vc from a D/A converter 6, and the D/A converter 6 outputs a voltage Vc according to frequency data from an externally operable memory 7.

The local oscillator 5, which is a feature of the present invention, includes an inverting oscillator 51 and an inverting oscillator 51.
A current control FET 52 is connected in series with the power supply of the inverting oscillator 51 in order to limit the operating current of the VcK, and an unnecessary frequency component is removed from the pulsating voltage appearing at the drain terminal of the current control FE 752 (a band-pass filter is used). 56 and an amplifier 54.

FIG. 2 is a schematic diagram for explaining the mechanism of generating the pulsating voltage. FIG. 2(a) is a configuration diagram of the inverting oscillator 51 in the case of five stages, and the inverter 11 to
15 connected in a ring shape, parasitic capacitances C1 to C5 also exist due to the respective gate capacitances.

Figure 2(b) shows the output voltage of each inverter.
It is a time chart figure when it does. inverter pc
When the so-called through current that momentarily passes through both the h and l'Jch FETs is very small compared to the charging/discharging current of the parasitic capacitances C1 to C5, the operating current of the inverting oscillator 51 is the same as when the Nch FET is turned on. Since it flows at the timing shown in FIG. 2(b), the shape is as shown in FIG. When this current flows through the current control FET 52, the drain terminal voltage also has the same form as Id,
Its frequency is exactly five times the inverting oscillation frequency.

In this case, a frequency adjustment FET was also used to extract the pulsating current as a voltage, but any element that has a relatively high impedance at high frequency will suffice, such as a simple resistor or an IC.
You can also use an inductor with aluminum wire wrapped inside it in a spiral shape.

Note that the parasitic capacitances C1 to C5 may be made very small, or
Alternatively, the through current can be made thicker (if this is done, a frequency exactly 10 times higher can be obtained).

FIG. 3 is a circuit block diagram showing another embodiment of the present invention. The difference from FIG. 1 is the addition of a local oscillator 500 circuit configuration, a variable frequency divider circuit 8, a crystal oscillation circuit 9, and a 7-speed detection circuit 10 for controlling the local oscillation frequency using a PLL method. . The phase detection circuit 1
0 has a general configuration in which the signal from the variable frequency divider circuit 8 and the signal from the crystal oscillation circuit 9 are compared and the output signal Vc is controlled so that the frequencies match. The local oscillator 50 is an inverting oscillator 51
Since it is provided with a waveform shaping circuit 55 that shapes the waveform of the oscillation signal, it is configured to output a frequency that is one-fifth of the local oscillation frequency. As a result, the configuration of the variable frequency divider circuit 8 does not need to be ultra-high speed (it becomes CMOS
A configuration with 70 blips is possible.

〔Effect of the invention〕

As described above, according to the present invention, in addition to being able to obtain high-frequency signals that could not be obtained conventionally with CMO8, there is no need for the conventional external LC resonant circuit, and there is also a prescaler (ultra high-speed fixed Since it also has the function of a frequency divider), it has revolutionary effects such as eliminating the need for local oscillation buffers and prescalers, which conventionally consumed large currents.
Contributes to miniaturization of tuners.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a circuit block diagram showing the configuration of a tuner, FIG. 2(a) is a circuit diagram of an inverting oscillator in the case of five stages, and FIG. FIG. 3 is a time chart diagram when the output voltage of the inverter is set to v1 to v5, and FIG. 3 is a circuit block diagram showing another embodiment. 2...RF amplifier, 6...Mixing circuit, 5.50...Local oscillator,

Claims (1)

[Claims] It has an inverter ring oscillator in which an odd number of CMOS inverters are connected in series in a ring shape, and an impedance element connected in series to the power supply of the inverter ring oscillator, and outputs the pulsating current frequency appearing in the terminal voltage of the impedance element as a local oscillation frequency. A tuner characterized by being equipped with a local oscillator.