JP2001168752A - Multi-band receiving circuit - Google Patents

Abstract

(57) [Problem] To reduce interference of a received wave with another band in a multi-band receiving circuit. The switch switches between reception of a low-band radio wave and reception of a high-band radio wave through a frequency conversion circuit.
Is disposed downstream of the attenuator 22 and the RF amplifier 23 of the low band receiving circuit, and a control circuit 31 for controlling the attenuator 22 and the RF amplifier 23 is provided. At the time of high band reception, the control circuit 31 controls the attenuator 22 and the RF amplifier 23 to attenuate the low band RF input signal level. As a result, the isolation of the switch 24 is improved, and interference due to RF input signals in bands other than the reception wave is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-band receiving circuit, and more particularly to a multi-band receiving circuit for reducing reception interference caused by other bands.

[0002]

2. Description of the Related Art An example of a conventional multiband receiving circuit will be described with reference to the drawings. Figure 2 shows a digital terrestrial wave (DA
B) shows a receiving circuit, in which the upper part is BAND3
(174 MHz to 240 MHz), and the lower part is a high-band L-BAND (1452).
MHz to 1491 MHz) is down-converted from 200 MHz to 240 MHz, and can receive signals by switching between BAND3 and L-BAND.

At the time of reception of BAND3, the radio wave incident on the antenna receives an LPF1, a switch 2, and an attenuator (P
IN diode) 3, RF amplifier 4, BPF5, FET
6. The signal passes through the BPF 7 and is mixed with the oscillation output of the oscillator 8 by the mixer 9 and frequency-converted to an intermediate frequency. AGC
The detector 10 controls the attenuator 3 and the FET 6 to keep the output level of the intermediate frequency constant.

[0004] As shown in the figure, when the switch 2 is switched to the frequency conversion circuit side, the RF input signal becomes H level of the frequency conversion circuit.
The signal passes through the PF 11, the attenuator 12, the RF amplifier 13, the attenuator 14, and the BPF 15, is mixed with the oscillation output of the oscillator 17 by the mixer 16, frequency-converts the L-BAND reception wave into a 200-240 MHz band, and the AGC detector 18 The intermediate frequency output, which is controlled to a constant level by controlling the attenuators 12 and 14,
Input to the attenuator 3 of the AND3 receiving circuit.

[0005]

In a conventional multi-band receiving circuit, when one band is received, the resistance to reception interference by the other band depends on the isolation of the switch, and its value is about 45 dB. In the example of 2, L
-At the time of BAND reception, interference due to RF signals of other bands that fly through LPF1 on the BAND3 reception side cannot be ignored.

Therefore, there arises a technical problem to be solved in order to improve the isolation at the switch portion and to improve the reception interference characteristic, and an object of the present invention is to solve the above problem.

[0007]

SUMMARY OF THE INVENTION The present invention proposes to achieve the above-mentioned object, and a frequency conversion circuit for converting a high-band input radio wave into a frequency suitable for a low-band reception circuit is provided via a switch. Multi-band reception connected to a low-band reception circuit and configured so that the input of the low-band reception circuit can be switched between the antenna input and the output of the frequency conversion circuit by a switch, so that low-band radio waves and high-band radio waves can be selectively received. In the circuit,
The switch is disposed after the attenuator and the RF amplifier of the low-band receiving circuit, and a control device for controlling the attenuation of the attenuator and the gain of the width amplifier is provided. It is an object of the present invention to provide a multi-band receiving circuit, wherein the control circuit is configured to maximize attenuation of an attenuator and minimize gain of an RF amplifier when receiving a radio wave.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. Figure 1 shows digital terrestrial broadcasting (DAB)
In the figure, the upper stage in the figure shows BAND3 (1
74MHz-240MHz) receiving circuit, lower stage is L-BAN
D (1452 MHz to 1491 MHz) is set to 20 of BAND3.
This is a frequency conversion circuit for down-converting to a 0 MHz to 240 MHz band.

The BAND3 receiving circuit includes an LPF 21, an attenuator 22, an RF amplifier 23, a BPF 25, an FET 2
6, BPF 27, mixer 28, oscillator 29 and AGC
The RF amplifier 23 and the BPF
The switch 24 is disposed between the switch 24 and the switch 25. The AGC detector 30 controls the attenuator 22 and the FET 26, and the control circuit 31 controls the attenuator 22, the RF amplifier 23, and the switch 24.

The frequency conversion circuit is the same as the conventional example shown in FIG. 2, and includes an HPF 11, an attenuator 12, an RF amplifier 13, an attenuator 14, a BPF 15, a mixer 16,
It comprises an oscillator 17 and an AGC detector 18.

At the time of BAND3 reception, the control circuit 31 switches the switch 24 to the BAND3 reception side, and does not control the attenuator 22 and the RF amplifier 23.
Is the maximum, and the AGC detector 30 controls the attenuation of the attenuator 22 and the gain of the FET 26 to obtain a constant level intermediate frequency output.

At the time of L-BAND reception, the control circuit 31 switches the switch 24 to the frequency conversion circuit side as shown in FIG. 1 to maximize the attenuation of the attenuator 22 preceding the switch 24 and minimize the gain of the RF amplifier 23. And As a result, the RF that has passed through the LPF 21 on the BAND3 receiving side
Since the input signal is attenuated to the minimum level by the attenuator 22 and the RF amplifier 23, the isolation of the two-input system in the switch 24 is improved, and the measured value is 11
0 dB, so that interference due to other bands during L-BAND reception does not occur, and the reception performance is improved.

As described above, since the control of the attenuator 22 and the RF amplifier 23 is not performed during the reception of the BAND3, the reception sensitivity of the BAND3 is not suppressed.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications are possible within the technical scope of the present invention, and it goes without saying that the present invention extends to those modifications. is there.

[0015]

As described above, the multi-band receiving circuit according to the present invention includes a switch for switching between reception of a low-band radio wave and reception of a high-band radio wave through a frequency conversion circuit, which is provided after the attenuator and the RF amplifier of the low-band reception circuit. And the control circuit controls the attenuator and the RF amplifier during high-band reception to attenuate the low-band RF input, so that the switch isolation is significantly improved and the reception performance is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a multiband receiving circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional multiband receiving circuit.

[Explanation of symbols]

 11 HPF 12 Attenuator 13 RF Amplifier 14 Attenuator 15 BPF 16 Mixer 17 Oscillator 18 AGC Detector 21 LPF 22 Attenuator 23 RF Amplifier 24 Switch 25 BPF 26 FET 27 BPF 28 Mixer 29 Oscillator 30 AGC Detector 31 Control Circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 5J100 JA01 KA05 QA01 QA02 SA02 5J103 AA16 AA17 AA24 BA02 BA06 CA07 CB04 DA03 DA15 DA16 DA41 GB03 5K020 BB08 DD01 DD05 EE18 FF00 HH11 HH12 KK02 LL01 5K062 AA02 AA02 AA02 A04 A02 A04 BC04

Claims (1)

[Claims] A frequency conversion circuit for converting a high-band input radio wave into a frequency suitable for a low-band reception circuit is connected to a low-band reception circuit via a switch, and the input of the low-band reception circuit is connected to the antenna input and the frequency conversion circuit by the switch. In a multi-band receiving circuit configured so as to be able to switch to the output of the low band radio wave and the high band radio wave, the switch is arranged at the subsequent stage of the attenuator and the RF amplifier of the low band receiving circuit, A control device for controlling the attenuation of the attenuator and the gain of the RF amplifier is provided, and when the input of the low-band receiving circuit is switched to the output of the frequency conversion circuit to receive a high-band radio wave, the control circuit maximizes the attenuation of the attenuator. , Wherein the gain of the RF amplifier is minimized. Multi-band receiving circuit.