JPH0438182B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides IF band VA
The present invention relates to a frequency conversion amplifier having both frequency conversion and amplification functions for ratio (video/audio signal ratio) adjustment and the like.

Conventionally, this type of frequency conversion amplifier device is
For example, the one shown in FIG. 1 is known.

In Figure 1, 1 indicates a television signal, etc.
An input terminal into which an RF signal is input, the input is an RF bandpass filter having a passband for the RF signal, and 4 is an input terminal.
A frequency converter including a mixer 5 and a local oscillator 6 for converting the frequency of an RF signal into an IF signal, 7 is a main amplifier, 8 is an IF bandpass filter having a pass band for the IF signal, 9 is an output terminal, and a frequency converter includes a local oscillator 6. Due to the C/N ratio and distortion in conversion and signal amplification, amplifiers are provided before and after the frequency converter 4, and a large number of amplifiers are required.

On the other hand, 10 is an AGC circuit, and when AGC is applied, if AGC is applied only with preamplifier 3, C/
It is disadvantageous in terms of N ratio, and only main amplifier 7 is required.
If AGC is applied, it is disadvantageous in terms of distortion, so
The preamplifier 3 is connected to the AGC circuit 10 as shown in the figure.
AGC is commonly applied to both the main amplifier 7 and the main amplifier 7, and there is a problem in that the structure of the AGC circuit becomes more complicated as the number of amplifiers increases.

The present invention has been made in view of such conventional problems, and is a frequency conversion amplifier device that has both frequency conversion and amplification functions for IF band VA ratio adjustment etc. The purpose is to simplify the amplifier section and AGC circuit section.

To achieve this objective, the present invention comprises a single amplifier having a band characteristic that includes the frequency bands of each of the input signal and the frequency-converted output signal;
A first filter that passes the first frequency band (RF signal frequency band) and blocks the second frequency band (IF signal frequency band) is connected between the input terminal and the input terminal of the amplifier, and the amplifier and output A second filter that passes a second frequency band and blocks the first frequency band is connected between the amplifier terminal and a filter that passes the first frequency band and blocks the first frequency band.
a third filter that blocks a frequency band of
connecting a series circuit of a frequency converter that converts a signal in a frequency band into a signal in a second frequency band and a fourth filter that passes the second frequency band and blocks the first frequency band; The circuit configuration of the amplifier section and the AGC circuit section are simplified by amplifying signals of different frequencies using a single amplifier.

Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a circuit block diagram showing one embodiment of the present invention. First, to explain the configuration, 1 is an input terminal into which an RF signal such as a television signal is input. Following input terminal 1, the RF signal frequency band (first frequency band) is passed through, and the IF signal frequency An RF filter 11 is provided as a first filter that blocks the frequency band (second frequency band),
The output of RF filter 11 is connected to the input terminal of amplifier 12. As the amplifier 12, the RF signal and
A wideband amplifier having low distortion amplification characteristics in the IF signal, ie, the first and second frequency bands, is used. An IF bandpass filter 13 is provided following the amplifier 12, and this IF bandpass filter 13 constitutes a second filter that blocks the frequency band of the RF signal and passes the frequency band of the IF signal. The output of the bandpass filter 13 is output terminal 9
connected to.

On the other hand, the amplifier 12 and the IF bandpass filter 1
3 and the connection point between the amplifier 12 and the RF bandpass filter 11, an RF bandpass filter 14, a frequency converter 4 including a mixer 5 and a local oscillator 6, and an IF bandpass filter 15 are connected. The RF bandpass filter 14 passes the frequency band of the RF signal, and the IF
The IF bandpass filter 15 constitutes a third filter that blocks the frequency band of the signal, and a fourth filter that passes the frequency band of the IF signal and blocks the frequency band of the RF signal and unnecessary spurious signals generated by frequency conversion. It constitutes a filter.

Furthermore, the output of the IF bandpass filter 13 is
The input of the AGC circuit 10 is connected to the AGC circuit 10.
AGC control voltage is applied to amplifier 12.

Next, the operation of the embodiment shown in FIG. 2 will be explained.
The signal is input to an amplifier 12 with a pass band of an RF bandpass filter 11, and the RF signal is preamplified in the amplifier 12 in a manner similar to conventional preamplification. The RF signal amplified by the amplifier 12 is
The signal passes through the RF bandpass filter 14, is input to the mixer 5 of the frequency converter 4, is frequency-converted by the local oscillation frequency from the local oscillator 6, and is output as an IF signal. The IF signal frequency-converted by the frequency converter 4 passes through the IF bandpass filter 15 and is input to the amplifier 12, where the IF signal is frequency-converted by the same amplifier 12 that amplifies the RF signal.
The signal is amplified, and the IF signal amplified by the amplifier 12 passes through the IF bandpass filter 13 and is applied to the output terminal 9.

Furthermore, the AGC for the amplifier 12 receives the IF signal that has passed through the IF bandpass filter 13 and is output.
The AGC control voltage is input to the AGC circuit 10 to generate the AGC control voltage for the amplifier 12, and the IF signal from the output terminal 9 is input to the amplifier 12 so that the signal level of the IF signal from the output terminal 9 is constant.
Performs automatic gain control of RF amplification and IF amplification.

In the embodiment shown in FIG. 2, since the output of the amplifier 12 is fed back to the input, there may be problems such as oscillation due to positive feedback, but the RF signal amplified and output by the amplifier 12 is 4 converts the frequency into an IF signal and inputs it to the amplifier 12, and the output and input frequency bands are different, so the RF
By setting the amount of out-of-band attenuation in the bandpass filter 14 and the IF bandpass filter 15 to be sufficiently large, problems such as oscillation do not occur.

In this way, in the embodiment shown in FIG. 2, the same amplifier 12 performs amplification of the input RF signal and amplification of the frequency-converted and output IF signal, so only one amplifier is required. Regarding AGC, when applied to the RF amplifier section, it is advantageous in terms of distortion but disadvantageous in terms of C/N ratio, and conversely, when applied to the IF amplifier section, C/N ratio is disadvantageous.
Although it is advantageous in terms of ratio, it is disadvantageous in terms of distortion, so
AGC is applied to both the RF and IF amplification sections to satisfy both C/N and distortion characteristics.

Therefore, according to the present invention, since AGC for both RF and IF signals can be performed by a single circuit, both C/N ratio and distortion characteristics can be easily satisfied. Furthermore, the AGC range of the AGC circuit 10 can also be reduced.

Note that the above embodiment is applicable to RF signals such as television signals.
In this example, a signal is input, frequency-converted to an IF signal, and amplified and output. However, the frequency bands of the input signal and the frequency-converted and amplified signal are not limited to this, and can be any arbitrary frequency band. It can be used as a frequency conversion amplifier device that has both frequency conversion and amplification functions in a frequency band.

Next, to explain the effects of the present invention, the input signal is amplified by an amplifier, then frequency converted, and the frequency converted signal is amplified again by the same amplifier and output. Since the converted signal can be amplified with a single amplifier, the configuration of the amplifier circuit section can be greatly simplified. Also, in a single amplifier
By applying AGC, AGC can be commonly applied to both the input signal and the frequency-converted signal, simplifying the AGC circuit and C/N.
AGC control that satisfies both ratio and distortion characteristics can be performed.

[Brief explanation of drawings]

Figure 1 is a circuit block diagram showing a conventional example, Figure 2 is a circuit block diagram showing a conventional example.
The figure is a circuit block diagram showing one embodiment of the present invention. 1...Input terminal, 4...Frequency converter, 5...
Local oscillator, 10...AGC circuit, 11...RF band pass filter (first filter), 12...
Amplifier, 13...IF bandpass filter (second
filter), 14...RF bandpass filter (third filter), 15...IF bandpass filter (fourth filter).

Claims (1)

[Scope of Claims] 1. A frequency conversion amplification device that amplifies a signal from an input terminal with an amplifier, converts the frequency, and outputs the signal to an output terminal, comprising: a first frequency band passing between the input terminal and the amplifier; a first filter that blocks a second frequency band is connected; a second filter that blocks the first frequency band and passes a second frequency band is connected between the amplifier and the output terminal; between the connection point between the second filter and the amplifier and the connection point between the first filter and the amplifier;
a third filter that passes a first frequency band and blocks a second frequency band; a frequency converter that converts a signal in the first frequency band to a signal in a second frequency band; 1. A frequency conversion amplification device, characterized in that a series circuit is connected with a fourth filter that blocks the frequency band and passes the second frequency band.