JP2006060757A - Tuner system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit system for obtaining the stable operation, satisfactory sensitivity and performance of a high frequency tuner to be used for the receiver of a compact mobile television and a communication unit portable telephone or the like even in a wide band reception frequency, and for realizing miniaturization and small power consumption. <P>SOLUTION: This circuit system is provided to convert a wide band reception frequency into an intermediate frequency signal within the range of a single or narrow frequency by an up-conversion frequency converting circuit, and to demodulate it by a direct conversion system. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

Tuner circuit system used in television receivers and mobile communication receivers

For television broadcasting, the conversion from the conventional analog system to the digital system has been started from the VHF band to the UHF band. Communication devices and mobile phones are also in the direction of wider frequency bandwidth due to increased demand. A mobile device needs a circuit system of a receiver that can cope with further downsizing and has stable and sufficient performance.

JP 2003-143029 A

Nikkei Electronics, 2003.8.18, pages 96 to 101, <Mobile phone reception>

The conventional superheterodyne reception method as shown in FIG. 3 was suitable for a large fixed receiver using an AC power supply, but the mobile device is small in size, stably operates in a wide frequency band, and consumes less power. There is a need to reduce and meet more sophisticated performance requirements.

As one of the conventional improvements

There is an up-conversion method as shown in. Although there is an effect that the physical circuit volume can be reduced by reducing the resonance circuit section 2 as used in FIG. 3, the number of stages, the volume, and the consumption of the other necessary circuit sections of the frequency conversion / intermediate frequency amplifier / demodulator. The power is the same as in the superheterodyne system.

on the other hand,

If only the direct conversion demodulation method is applied to the receiver as in the example of the above, in principle, there is a feature that enables miniaturization and power saving without using a resonance circuit, a frequency conversion circuit, and an intermediate frequency circuit filter. Since the local oscillation frequency is the same as the reception frequency, it is well known that the influence of the interference is a problem.
When used in a UHF television receiver, it is difficult to obtain a stable operation performance over a wide broadcasting frequency band in order to suppress it within a practically unaffected range.

As an improvement measure, when using the low IF direct conversion demodulation method, the reception frequency and the local oscillation frequency are mixed with a slight difference, and the same effect as the direct conversion demodulation method is obtained by digital software processing. However, the disadvantage of this method is that a significantly large digital signal processing software capacity is required. Naturally, the circuit capacity and current consumption increase.

Since both have the above-mentioned problems, they are limited in use. Furthermore, the resonance circuit composed of coils and variable capacitance elements in the input circuit system occupies a volume where physical volume cannot be ignored, so it can be omitted and can be configured as a receiver without using a reception frequency resonance circuit. On the other hand, the absence of a resonator means that the input circuit is a non-tuned circuit and has a wideband frequency characteristic, so it does not have the selectivity to exclude signals other than the reception frequency, so it is vulnerable to interference caused by signals other than the reception frequency. Have the following disadvantages. Similarly to DC, the input resistance is also high, and it is necessary to add a circuit element destruction prevention circuit when high voltage static electricity is applied.

The disadvantages in the above problems are eliminated and advantageous properties are used in combination.
The up-conversion system requires a high frequency first intermediate frequency system and a low frequency second intermediate frequency system. The second intermediate frequency system has a low frequency, and band filters such as an amplifier and SAW filter occupy a large physical volume and current consumption. Therefore, these are replaced with a system capable of a small capacity.

The direct conversion demodulation method using the same local oscillation frequency as the reception frequency has a simple circuit configuration, can reduce physical volume and power consumption, and is economically advantageous. Therefore, it is necessary to reduce interference with the local oscillation frequency signal. Optimizing high-frequency coupling and balance adjustment, such as mixing circuits, over a wide reception frequency band is not easy to manage experimentally or in product production, and it is difficult to design and adjust. In order to avoid this, it is sufficient to use a means for a single frequency or a sufficiently narrow band.

The present invention pays attention to each of the above features, uses an up-conversion system, and after the first intermediate frequency signal output of the conventional normal means, the second frequency conversion circuit, the second local oscillation circuit, the second intermediate frequency filter, The configuration of the amplifier circuit and demodulator is replaced with a simple direct conversion demodulation method. In the direct conversion demodulation method, it is only necessary to deal with the single intermediate frequency, the single frequency, or a frequency range close thereto, so that the problem of dealing with a wide frequency band can be avoided.

The direct conversion demodulation circuit system also requires a second local oscillation circuit. However, since the second local oscillation circuit has a single frequency or a plurality of single frequencies of a narrow frequency, it does not change a wide band.
On the other hand, variable frequency for wideband reception is shared by the first local oscillation circuit by using up-conversion together.

By adding the amplification function of the up-conversion circuit, the input level of the direct conversion circuit increases, so that the performance can be improved and stabilized.

The up-conversion method is characterized in that the resonance circuit for suppressing the image reception frequency can be deleted by setting the image reception frequency not to be generated within the reception band, and the amplifier circuit and the like use a wide band. Thus, the effects of signal suppression and increased distortion on the received frequency signal due to high-level input signals inside and outside the reception band frequency cannot be avoided.

For the purpose of eliminating the influence of the above signal suppression, even if the required level difference of other frequency signals is several decibels than the target reception frequency input, it is effective. That is, since the single conversion circuit system does not require a high image frequency suppression like the image frequency suppression, a variable multi-stage resonance circuit for obtaining a high Q is not necessary, so that the physical volume of the wire ring is large, the inductance fine adjustment process and the space Therefore, a plurality of three-dimensional wire ring structures that are necessary is not necessary.

In the case of the present invention, attention is paid to the fact that a low Q frequency selectivity is effective, and a resonance circuit can be formed by a stripline line on the substrate, so that the physical volume is not excessively increased.
This reception frequency resonance circuit can be controlled by a technique linked to a variable capacitance element variable voltage that controls the first local oscillation.

A system that does not use a complicated software processing circuit configuration such as a low IF system, and uses the same local oscillation frequency type direct conversion demodulation system and enables a receiver with a wideband frequency, enabling a compact and low power consumption configuration. To do.

Even in combination with the up-conversion method, a filter having a high first intermediate frequency, for example, 2 GHz, is physically and electrically small in volume but has a low frequency band, a second intermediate frequency amplifier, and a second intermediate frequency. The band-pass filter can eliminate a problem that a physical volume is large and a current consumption is excessive when a normally used, for example, SAW filter of about 50 MHz is used.

By providing a simple resonant circuit in the input circuit, interference due to high-level input outside the reception frequency, which is a weak point of the wide-band frequency high input resistance circuit in the up-conversion and direct conversion methods, and DC high-voltage discharge input breakdown voltage Can be improved.

FIG. 1 is a circuit diagram according to claim 1 of the present invention.
The signal output of the demodulation block 22, which includes the direct conversion demodulation block 22, the first frequency conversion circuit based on the up-conversion method, and the first intermediate frequency circuit block 21, is connected to the receiver 18.

In the reception frequency and television, the configuration for giving the data signal from the receiver main body to the reception tuner section for controlling the selection of the reception channel is a normal design means. In the present invention, the configuration and circuit are limited. It is not what you do.

The first frequency conversion circuit and the first intermediate frequency circuit 21 are a first intermediate frequency that is higher than the reception frequency and does not affect the image frequency by the first frequency conversion circuit 4 and the first local oscillation VCO 12 that controls the synthesizer 13. It operates as an up-conversion to convert to the frequency set in.
The first intermediate frequency band filter 6 is configured by SAW or a filter circuit.
The presence or absence of the broadband amplifier 3 can be selected according to design specifications, and is not the essence of the present invention.

Conventionally, the direct conversion method is usually used by directly connecting to the input 1. However, in this method, the demodulation circuit 22 uses the first intermediate frequency as a direct conversion input with the first intermediate frequency output as an input. Used as a means for demodulating a signal. The first intermediate frequency amplifier 6 is a narrow-band amplifier having only the first intermediate frequency and does not correspond to a wideband frequency.

The synthesizer circuits 13 and 14 and their clock signal input configurations are possible by ordinary design means, and are not limited to specific circuits.

FIG. 2 is a circuit diagram in which claim 2 of the present invention is added to the circuit according to claim 1.
The main point is to set the resonance circuit 2 to be tuned to the desired reception frequency. In this example, means linked to the synthesizer 13 and the up-conversion frequency conversion local oscillator VCO 12 are used.

The presence or absence of the amplifiers 3 and 6 shown in FIG. 1 can be selected depending on design factors.

1 is a system diagram according to a first embodiment of the present invention. It is a systematic diagram by the 2nd Example of this invention. It is a systematic diagram by a conventional method example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna high frequency signal input terminal 2 Resonance circuit 3 High frequency amplifier circuit 4 1st frequency converter 5 1st frequency filter 6 1st intermediate frequency amplifier 12 1st local oscillation circuit 13 Synthesizer circuit 14 Direct conversion circuit Synthesizer circuit 15 Direct conversion circuit local Oscillation circuit 18 Receiver 19 Frequency control line 21 First intermediate frequency circuit block 22 Direct conversion demodulation blocks 24, 25, 26 and 31, Second intermediate frequency circuit 35 Second local oscillation circuit

Claims (2)

The present invention relates to a tuner unit system that demodulates an input high-frequency signal in a TV receiver that receives digitized TV waves using a UHF band and a VHF band, and a mobile communication apparatus. The first intermediate frequency generated by the first mixer that is input to the first mixer and mixes the first local oscillation frequency is configured as an up-conversion method that sets the frequency higher than the upper limit frequency of the reception frequency, and
The first local oscillator VCO is configured to output a first local oscillation frequency corresponding to a channel number controlled by a PLL synthesizer circuit, that is, a reception frequency, and a means for obtaining a demodulated signal is the same as the first intermediate frequency signal. A reception method comprising a method of applying a so-called direct conversion demodulation circuit that mixes with a local oscillation frequency signal and a second mixer. A resonance circuit consisting of a set of inductance and variable capacitance element on the signal line between the antenna input and the high-frequency amplifier, the capacitance of the variable capacitance element is changed in conjunction with the frequency control of the VCO, and the reception frequency is selected. The inductance to be tuned to the ground is one end of the inductance formed by the stripline conductor formed on the circuit board or between the layers of the board layer, and the signal input terminal is connected to one end of the inductance or a middle part of the inductance, and the signal input A circuit according to claim 1, wherein a circuit for forming a DC ground is added to the line.

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