JPH0711026U - Intermediate frequency amplifier circuit - Google Patents

Abstract

(57) [Abstract] [Objective] In the intermediate frequency amplifier circuit, the tuning transformer is formed by a single-tuning secondary winding type IF transformer, and it is possible to suppress the influence of variations in characteristics caused by using a ceramic filter, and to improve the characteristics. Another object of the present invention is to provide an intermediate frequency amplifier circuit capable of obtaining IF characteristics. A mixer circuit unit that mixes and superposes two input high-frequency signals and outputs the mixed high-frequency signals via a tuning transformer; and an amplifier circuit unit that amplifies and outputs a signal from the mixer circuit unit through a ceramic filter. In the intermediate frequency amplification circuit including, the mixer circuit unit forms the tuning transformer by a single tuning secondary winding type transformer IFT2, and
The amplifier circuit section is configured to amplify and output the signal output from the mixer circuit section through a first ceramic filter CF1 having a wide bandwidth, and the amplified signal output of the amplifier circuit section is predetermined. The second ceramic filter CF2 having the designed bandwidth and the signal output section for outputting to the detection circuit of the next stage after passing the second ceramic filter CF2.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an intermediate frequency (IF) amplifier circuit, and more particularly to an IF amplifier circuit including a ceramic filter used in a receiver or the like for receiving a remote control signal in a wireless communication device or an electric device such as OA or AV.

[0002]

[Prior art]

 As is well known, the wave between the high frequency and the audio frequency (low frequency) is called the intermediate frequency or IF. This is a combination of the received high frequency signal and the high frequency generated by the oscillation circuit, It is made by interlocking and amplifying the oscillation frequency of the oscillation circuit with respect to the received frequency so that the frequency difference is always constant. This intermediate frequency is detected and taken out as a signal to control various devices. Generally, wireless communication devices and electric devices are equipped with a receiver that receives a remote control signal at an intermediate frequency. In recent years, this receiver has been equipped with an IF amplifier circuit equipped with a ceramic filter. It is used a lot. This ceramic filter functions as a ceramic resonator with piezoelectric effect by attaching silver films on both sides of ceramic (porcelain) made by sintering barium titanate etc. and performing polarization treatment. This element functions as a filter equivalent to, for example, an LC resonance circuit, and is often used as a high frequency filter such as 10.7 MHZ for frequency conversion. However, in an IF amplifier circuit using such a ceramic filter, the influence of the characteristics of the ceramic filter itself often causes a problem in the circuit configuration.

FIG. 2 shows a conventional IF amplifier circuit using the above-mentioned ceramic filter. 1 is a power supply terminal (Vcc), 2 is a common terminal (GND), 3 is a signal input terminal (MIX), and 4 is a signal. It is an output terminal (Vo). Q1 and Q2 are NPN transistors, R1 to R10 are resistors, C1 to C6 are capacitors, IFT1 is an intermediate frequency transformer (IF transformer), and CF1 is a ceramic filter (10.7 MHZ). A is a mixer circuit section and B is an amplifier circuit section.

In the mixer circuit section A in FIG. 2, the base of the transistor Q1 is connected to the signal input terminal 3, and the collector thereof is connected to the power supply terminal 1 through the parallel circuit of the IF transformer IFT1 and the capacitor C1. Its emitter is connected to the common terminal 2 through a parallel circuit of a resistor R3 and a capacitor C3. A capacitor C2 is connected between the power supply terminal 1 and the common terminal 2, and bias resistors R1 and R2 are provided between the power supply terminal 1 and the base of the transistor Q1 and between the base and the common terminal 2, respectively. It is connected. On the other hand, the amplifier circuit section B takes in the signal output from the collector of the transistor Q1 to the ceramic filter CF1 via the resistor R4, and the output end thereof is connected to the base of the transistor Q2 via the resistor 6. Its collector is connected to the power supply terminal 1 via the resistor R9, and its emitter is connected to the common terminal 2 via the parallel circuit of the resistor R10 and the capacitor C5. Bias resistors R7 and R8 are connected between the power supply terminal 1 and the base of the transistor Q2 and between the base and the common terminal 2, respectively. A parallel circuit of a capacitor C4 and a resistor R5 is connected between the output terminal of the ceramic filter CF1 and the common terminal 2, and the collector of the transistor Q2 is connected to the signal output terminal 4 via the capacitor C6.

In such an IF amplifier circuit of FIG. 2, two frequencies are superposed and mixed on the signal input terminal 3 in a state where the power supply voltage Vcc is applied between the power supply terminal 1 and the common terminal 2. When a high frequency signal (RF signal) is input, the transistor Q1 is turned on, tuned by the tuning circuit (parallel resonant circuit) of the tuning transformer, that is, the IF transformer IFT1, and sent to the ceramic filter CF1 in the next stage. The selectivity Q of this tuning circuit determines whether the characteristics are good or bad. When the selectivity Q becomes high, only the signal component is amplified and the others are attenuated. Therefore, it is necessary to design so that the value of Q normally becomes high. is there. The ceramic filter CF1 is a high-pass filter that passes a high frequency of 10.7 MHZ or more, and outputs the passed high frequency signal to the amplifying transistor Q2 of the next stage to amplify it, and through the output terminal 4, not shown in the next stage. It is configured to send to the detection circuit.

[0006]

[Problems to be solved by the device]

 However, such a conventional circuit configuration has the following problems. In the IF amplifier circuit in FIG. 2, since the high frequency signal input to the signal input terminal 3 is passed through the mixer circuit section A and then the ceramic filter CF1 is passed through one stage, the characteristics of the ceramic filter CF1 itself are There were drawbacks that the influence of the variations became large, impedance matching could not be obtained, the frequency selectivity became poor, and as a result the characteristics of the IF amplifier circuit became defective. An object of the present invention is to eliminate the above-mentioned conventional problems and provide an IF amplifier circuit having a simple circuit configuration and good impedance matching characteristics.

[0007]

[Means for Solving the Problems]

 To achieve this object, the present invention provides a mixer circuit unit that mixes and superposes two input high-frequency signals and outputs the mixed high-frequency signals through a tuning transformer, and a signal from the mixer circuit unit that passes through a ceramic filter. In the intermediate frequency amplifier circuit including an amplifier circuit section for increasing and outputting, the mixer circuit section forms the tuning transformer by a single tuning secondary winding type transformer, and the amplifier circuit section comprises the mixer circuit. A signal output from the unit is configured to be amplified and output by passing through a first ceramic filter having a wide bandwidth, and the amplified signal output of the amplifier circuit unit having a predetermined design bandwidth. We propose an IF amplifier circuit that is composed of a signal output section that outputs the signal to the next-stage detection circuit after passing through the ceramic filter.

[0008]

【Example】

 Hereinafter, details of an embodiment of the present invention will be described with reference to FIG. 1, the same reference numerals as those in FIG. 2 indicate the same components, C7 to C9 are capacitors, R11 to 13 are resistors, IFT2 is a single tuning (secondary winding) IF transformer, and CF2 is a ceramic filter. . C is a signal output unit. In the mixer circuit unit A in FIG. 1, the base of the transistor Q1 is connected to the signal input terminal 3, and the collector thereof is a parallel circuit of the primary side coil of the IF transformer IFT2 and the capacitor C7 in the single-tuned secondary winding configuration. Is connected to the power supply terminal 1 through the emitter, and its emitter is connected to the common terminal 2 through the parallel circuit of the resistor R3 and the capacitor C3. A capacitor C2 is connected between the power supply terminal 1 and the common terminal 2, and bias resistors R1 and R2 are connected between the power supply terminal 1 and the base of the transistor Q1 and between the base and the common terminal 2, respectively. ing. It should be noted that one end of the IF transformer IFT2 is connected to the common terminal 2.

On the other hand, the amplifier circuit unit B takes in the signal output from the other end of the secondary coil of the IF transformer IFT2 to the ceramic filter CF1 via the resistor R11, and the output end thereof is connected to the base of the transistor Q2 via the capacitor C8. Connected to. Its collector is connected to the power supply terminal 1 via the resistor R9, and its emitter is connected to the common terminal 2 via the parallel circuit of the resistor R10 and the capacitor C5. Bias resistors R7 and R8 are connected between the power supply terminal 1 and the base of the transistor Q2 and between the base and the common terminal 2, respectively. In the signal output circuit C, the signal output from the collector of the transistor Q2 is taken into the ceramic filter CF2, the output end of which is connected to the signal output terminal 4 via the resistor R12, and the capacitor C9 and the capacitor C9 are connected in parallel with the ceramic filter CF2. The resistor R13 is connected.

In the IF amplifier circuit of the illustrated embodiment, in a state where the power supply voltage Vcc is applied between the power supply terminal 1 and the common terminal 2, the high frequency signal (2) where the two frequencies are superposed and mixed on the signal input terminal 3 ( When the RF signal) is input, the transistor Q1 is turned on, and is tuned by the tuning circuit (parallel resonance circuit) of the IF transformer IFT2 having the single tuning secondary winding configuration to match the input impedance of the ceramic filter CF1 in the next stage. input. The selectivity Q of this tuning circuit determines whether the characteristics are good or bad. When the selectivity Q becomes high, only the signal component is amplified and the others are attenuated. Therefore, in the example shown in the figure, the value of Q becomes high. , An IF transformer IFT2 having a single tuning secondary winding configuration is used.

The ceramic filter CF1 is a high-pass filter that passes high frequencies of 10.7 MHZ or higher, and outputs the passed high-frequency signal to the amplifying transistor Q2 in the next stage for amplification and input to the ceramic filter CF2 in the next stage. To do. The resistor R9 is a resistor that adjusts the input impedance, and the resistor R13 is a resistor that adjusts the output impedance. Here, the ceramic filter CF1 has a large (wide) filter bandwidth, and the ceramic filter CF2 has a bandwidth having a target design value. By adjusting the input and output impedances of resistors R9 and R13, impedance matching can be easily performed, and only the target frequency is selected and other frequencies are not passed. Therefore, a ceramic filter is used. It is possible to suppress the influence of variations in the characteristics of the ceramic filters CF1 and CF2 caused by the above. Then, the output signal having a good IF characteristic is sent to the detection circuit (not shown) at the next stage through the signal output terminal 4.

[0012]

[Effect of device]

 As is apparent from the above description, the present invention is configured such that the IF transformer of the mixer circuit unit A is configured to raise Q by using a transformer having a single tuning secondary winding structure, and the bandwidth of the first ceramic filter CF1 is increased. Is widened, the bandwidth of the second ceramic filter CF2 is set to the target bandwidth, and the influence of the characteristic variation caused by using the ceramic filter is configured by adjusting the input / output impedance. Since it is suppressed, there is a practical advantage that good IF characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an IF amplifier circuit showing an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram showing an example of a conventional IF amplifier circuit.

[Explanation of symbols]

 1 power supply terminal (Vcc) 2 common terminal (GND) 3 signal input terminal (MIX) 4 signal output terminal (Vo) A mixer circuit section B amplification circuit section C signal output section Q1 to Q2 NPN transistors R1 to R13 resistance C1 to C9 Capacitor IFT1 IF transformer IFT2 Single tuning secondary winding type IF transformer CF1, CF2 Ceramic filter

Claims (1)

[Scope of utility model registration request] 1. A mixer circuit section for mixing and superposing two input high-frequency signals and outputting the mixed high-frequency signals via a tuning transformer, and an amplifier circuit for amplifying and outputting a signal from the mixer circuit section through a ceramic filter. An intermediate frequency amplifier circuit including a section, the mixer circuit section forms the tuning transformer by a single-tuned secondary winding type transformer, and the amplifier circuit section outputs a signal output from the mixer circuit section in a bandwidth. A wide first ceramic filter is passed through to amplify and output the amplified signal output of the amplification circuit section after passing through a second ceramic filter having a predetermined design bandwidth. An intermediate frequency amplifier circuit comprising a signal output section for outputting to a detection circuit.