JP2000269755A - Amplifier and communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transceiver device which is small-sized, light-weight, and of low-cost and copes with plural systems. SOLUTION: In an amplifier in the transceiver device, eight of two amplification circuits 61 and 62 and one of two feedback amplifiying circuits 63 and 64 are driven by a control circuit 65 to constitute a reception circuit, and DC offset is reduced in either amplification circuit by feedback amplifying circuits.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifying device used in a receiving circuit of a communication device and a communication device using the amplifying device.

[0002]

2. Description of the Related Art As radio communication systems, there are various systems such as an analog system and a digital system.
Each system is assigned a frequency band centering on the UHF band.

FIG. 8 shows a configuration of a general mobile communication device (transceiver). 1 is a transmitting unit, 2 is a receiving unit, and a part of them (for example, a demodulator) can be constituted by an IC. The transmission signal output from the transmission unit 1 is sent to the antenna 9 via the duplexer 8. The received signal received by the antenna 9 is input to the receiving unit 2 via the duplexer 8.

[0004] Reference numeral 3 denotes an analog / digital conversion circuit, 4 denotes an audio digital signal processing circuit, and 5 denotes an audio interface circuit which operates as an interface between the microphone 6 and the speaker 7 and the audio digital signal processing circuit 4. The audio information input from the microphone 6 is subjected to digital signal processing in an audio digital signal processing circuit 4 and converted into an analog signal in an analog / digital conversion circuit 3.
It is input to the transmission unit 1.

[0005] The signal input to the transmission section 1 is orthogonally modulated by a quadrature modulator 10 to a signal of a transmission frequency.
The quadrature-modulated signal output from is amplified by a buffer amplifier 11, input to a power amplifier 13 via an RF (bandpass) filter 12, amplified to a desired power, and supplied to a duplexer 8.

The signal input to the receiving section 2 is amplified by a low noise amplifier 14, input to a converter 16 via an RF filter 15, converted into an IF (intermediate frequency) signal, and subjected to a SAW (surface acoustic wave) filter. The signal is input to the IF amplifier 18 via the amplifier 17, amplified, demodulated by the quadrature demodulator 19, and supplied to the analog / digital conversion circuit 3. The signal from the receiving unit 2 input to the analog / digital conversion circuit 3 is converted into a digital signal, subjected to digital signal processing by an audio / digital signal processing circuit 4, and supplied to a speaker 7 via an audio interface circuit 5. .

Reference numeral 20 denotes a crystal oscillator, reference numeral 21 denotes an RF synthesizer, and the RF synthesizer 21 includes a crystal oscillator 2
A signal of a desired frequency is generated from the oscillating signal from 0 and supplied to the offset mixer 22, the converter 16, and the IF oscillator 23 in the transmission unit 1. The offset mixer 22 outputs a quadrature carrier signal to the quadrature modulator 10 based on the signal from the RF synthesizer 21, and the converter 16 converts the RF signal of a desired reception frequency into an IF signal based on the signal from the RF synthesizer 21. After the conversion, the IF transmitter 23 outputs the quadrature phase I based on the signal from the RF synthesizer 21.
The F signal is output to the quadrature demodulator 19.

In the field of such mobile communication devices, in recent years, a type in which one communication device can be used for a plurality of communication systems has been desired. Therefore, a system using a plurality of frequencies has been proposed. That is, two different wireless communication systems (eg, FDD / TD)
The MA communication method) uses a different receiving method, and therefore requires a transceiver device having a configuration that can be used in both of the two wireless communication systems. Such a transceiver device that can be used in a plurality of systems can be configured such that two independent transceiver devices adapted to each wireless communication system are first formed, and they are integrally configured. It can also be shared to reduce the size, weight, and power consumption.

FIGS. 9 and 10 show such a dual (D
ua) shows another aspect of the receiving unit in the system, and FIG. 9 has two independent receiving systems. In FIG. 9, 24 and 25 are antennas, 26 and 2
7 is an RF amplifier, 28 and 29 are first mixers, 30, 31
Is a first oscillator, 32 and 33 are first bandpass filters that pass signals of the first IF frequency from the first mixers 28 and 29, 34 and 35 are second mixers, 36 and 37 are second oscillators, 38 and 39. Is the second I from the second mixers 34 and 35
A second band-pass filter for passing a signal of the F frequency,
40 and 41 are demodulation units.

FIG. 10 has a common IF section. In FIG. 10, 42 and 43 are antennas, and 44 and 4
5 is an RF amplifier, 46 and 47 are first mixers, 48 and 49
Are first oscillators, which are first mixers 46, 4
7 oscillates a signal having a frequency that outputs a signal having a common IF frequency. 50 and 51 are switches, and 52 is a first switch.
A band-pass filter, 53 is a second mixer, 54 is a second oscillator, 55 is a second band-pass filter, 56 is a switch, and 57 and 58 are demodulation units.

FIG. 11 shows a part of FIG. 9 in detail, and FIG.
Shows some details of FIG.

[0012]

In the dual system having the above-described configuration, for example, two demodulation units conventionally configured by two ICs can be configured by one IC.

However, in the configurations shown in FIGS. 9 and 12, the two demodulation sections are independent of each other and the input pins are also independent, so that the mounting area required for configuring the system is large, There is a problem that the number increases. Also, in the configuration shown in FIGS. 10 and 12, although the part before the demodulation unit is shared,
Again, the two demodulation units are independent, and the input pins are also independent. Such a demodulating IC uses a package of about 20 to 30 pins. In this case,
The number of pins increases by 4 pins for each demodulation unit (2 pins for input pins and 2 pins for differential output, for a total of 4 pins. When feedback is applied, the frequency is low. In this case, three input pins are required.) Therefore, if the plurality of demodulation units are integrated into one IC as it is, it does not contribute to the miniaturization of the IC package expected by reducing the number of pads of the IC itself, and the mounting area is still large. There is a problem that the number increases.

As described above, the conventional configuration is not preferable as a method of configuring a portable transceiver device that is strongly required to be reduced in size, weight and power consumption.

SUMMARY OF THE INVENTION It is an object of the present invention to realize a small, lightweight, and low current consumption type communication device for a plurality of communication systems.

[0016]

To achieve the above object, according to the present invention, a first amplifier circuit and a second amplifier circuit for amplifying a signal received from a common input terminal, A first feedback amplifier circuit that feeds back an output signal; and a second feedback amplifier circuit that feeds back an output signal of the second amplifier circuit, wherein the first feedback amplifier circuit is larger than an amplification factor of the first amplifier circuit. It has an attenuation rate, and the second feedback amplification circuit has an attenuation rate larger than the amplification rate of the second amplification circuit.

According to a second aspect of the present invention, in the first aspect, a first control for controlling one of the first amplifier circuit and the first feedback amplifier circuit and any one of the second amplifier circuit and the second feedback amplifier circuit. The circuit further includes a circuit.

Further, the invention according to claim 3 is characterized in that, in claim 1, there is further provided a second control circuit for controlling at least one of the first feedback amplifier circuit and the second feedback amplifier circuit.

According to a fourth aspect of the present invention, in the first aspect, the first feedback amplifier circuit and the second feedback amplifier circuit drive a common load and connect a low-pass filter to an output. It is characterized by having done.

According to a fifth aspect of the present invention, in the third aspect, the second control means adjusts an amplification factor of the first feedback amplifier circuit or the second feedback amplifier circuit to the first amplifier circuit or the second amplifier circuit. The control is performed according to the offset of the output of the circuit.

According to a sixth aspect of the present invention, there is provided a communication device using the amplifying device according to any one of the first to fifth aspects.

[0022]

Embodiments of the present invention will be described below in detail.

(Embodiment 1) The present invention will be described below with reference to Embodiment 1, but the present invention is not limited to this embodiment.

FIG. 1 shows a circuit diagram of this embodiment. The amplifier circuit 61 and the amplifier circuit 62 have a common input and the input is DC cut. The output of each of the amplifier circuits 61 and 62 is returned to the input side by a feedback amplifier 63 and a feedback amplifier 64. Each circuit 61-64
Is turned on / off by the control circuit 65.

The feedback amplifier circuit is constituted by an amplifier circuit, and can have the structure shown in FIG. FIG.
As shown in (1), the load (resistance) 66 for extracting the output of the differential amplifier circuit constituting each feedback amplifier circuit,
67 is common, so that one low-pass filter 68 is connected to the output section (see FIG. 3). The control circuit 65 includes a feedback amplification circuit 63,
By controlling the 64 constant current sources 69 and 70, the circuits 63 and 64 are on / off controlled. Control circuit 65
Is also the same for the amplifier circuits 61 and 62.

The low-pass filter 68 is connected to the amplifier 6
Amplifying circuits 61,
The decay rate is larger than the amplification rate of 62. This makes it possible to feed back only the DC component generated in the amplifier circuits 61 and 62 to the input. The feedback amplifier circuits 63 and 64 allow the amplifier circuits 61 and
62 DC components can be removed. This feedback signal is returned to the input side so that the output signal of the amplifier circuits 61 and 62 has the opposite phase, so that the amplifier circuits 61 and 6
2 works in the direction of removing the DC component generated in the device.

The amplifier circuits 61 and 62 can have a circuit configuration required by each communication system. That is, for example, one can be a limiter circuit and the other can be a demodulation circuit. In the case of this demodulation circuit, a circuit configuration in which a demodulator is provided at the subsequent stage of the amplifier circuit is also possible.

According to the above configuration, by arranging a common circuit or filter at a stage preceding the input unit, the size and weight of the device can be reduced. For example, the output of the filter 55 of FIGS. 10 and 12 can be connected to the input unit without using the switch 56. In addition, since the number of pins of the IC is reduced by adopting the common input structure, the size of the IC itself and the size and weight of the package can be reduced.

Next, the state of operation by the control circuit is shown in FIG.
As shown in FIG. As shown in FIG. 4, when the amplifier circuit 61 and the feedback amplifier circuit 63 are turned on and the amplifier circuit 62 and the feedback amplifier circuit 64 are turned off, the amplifier circuit and the feedback amplifier circuit on the off side are disconnected in the input / output connection. It has been done. On by control circuit
The / off control may be performed by controlling a constant current source as shown in FIG. 2, or may be disconnected by a switch. Next, the amplifier circuit 61 and the feedback amplifier circuit 63 are in the off state,
FIG. 5 shows a state in which the amplifier circuit 62 and the feedback amplifier circuit 64 are turned on.

(Embodiment 2) FIG. 6 shows a configuration in which the gain of the feedback amplifier circuit is made variable. Reference numeral 71 denotes a feedback gain control circuit, which changes the amplification factor by changing the current value of the constant current source of the feedback amplifier circuits 63 and 64 as shown in FIG. By changing the amplification factor, a DC component generated in the output unit can be removed. The control circuit 65 controls on / off of the amplifier circuits 61 and 62.

When the input signal is treated as a differential signal,
in = Vsig + Vdc.

Here, Vsig is an input signal, and Vdc is a voltage applied to the input from the feedback amplifier circuit, and is a DC offset at the output of the amplifier circuit. Assuming that the DC offset signal generated by the amplifier circuit is Voff and the amplification factor of the amplifier circuit is G, G × Voff is generated at the output of the amplifier circuit. By applying this voltage to the input in the opposite phase, V
in = Vsig−Voff. When the amplification factor G inside the amplifier circuit and the internally generated Voff are added, D
The C offset can be removed.

G × Vin = G × (Vsig−Voff +
(Voff) = G × Vsig (Embodiment 3) In an actual circuit, this DC offset occurs not only in the input section of the amplifier circuit, but also the amplifier circuit may be composed of multiple stages. Since the rate is arbitrarily set, the DC offset cannot be completely removed. In the multi-stage amplifier circuits 72 to 75 shown in FIG. 7, when the amplification factor is variable, the value of the DC offset changes according to the amplification factor. For this reason, if the amplification factor of the feedback amplifier circuit 76 can be made variable, large feedback can be applied when the output DC offset is large, and small feedback can be applied when the output DC offset is small.

For example, when the amplifier circuit has two stages, the offset voltage generated in the first stage is Voff1 and the second stage is Voff.
f2, and the respective amplification factors are G1 and G2. Assuming that the offset voltage in the amplifier circuit occurs at the input section, the following equation is solved.

When there is no feedback, the DC offset component of the output section is Voff1 × G1 × G2 + Vo
ff2 × G2. Assuming that the amplification factor of the feedback amplifier 76 is Gf, the potential at the input section can be represented by multiplying the offset of the output section by Gf. Therefore, the offset (Vdc) of the output unit is given by the following equation.

Vdc = -Gf × Vdc × G1 × G2 + V
off1 × G1 × G2 + Voff2 × G2 Therefore, Vdc = (Voff1 × G1 × G2 + Voff
2 × G2) / (1 + Gf × G1 × G2) It suffices to set Gf such that Vdc is reduced.
In the case of a variable amplifier, G1 and G2 may function as an attenuator. When G1 and G2 are made variable by an external control signal, the gain of the feedback circuit can also be set to change according to the external control signal.

[0037]

As described above, according to the present invention, an inexpensive, compact and lightweight communication device can be configured in a communication system compatible with a plurality of systems.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating details of the first embodiment.

FIG. 3 is a block diagram illustrating a low-pass filter according to the first embodiment.

FIG. 4 is a diagram illustrating a connection mode according to the first embodiment.

FIG. 5 is a diagram showing another connection mode of the first embodiment.

FIG. 6 is a block diagram of a second embodiment of the present invention.

FIG. 7 is a block diagram of a third embodiment of the present invention.

FIG. 8 is a block diagram of a general mobile communication device.

FIG. 9 is a block diagram of a conventional receiving system.

FIG. 10 is a block diagram of another conventional receiving system.

11 is a diagram showing some details of the example of FIG. 9;

FIG. 12 is a diagram showing some details of the example of FIG. 10;

[Explanation of symbols]

 61, 62 amplifying circuit 63, 64 feedback amplifying circuit 65 control circuit

 ────────────────────────────────────────────────── ─── Continued on the front page F-term (reference) 5J069 AA01 AA21 AA53 AA54 AC03 CA13 CA92 FA15 FA17 FA18 HA02 HA25 HA29 HA39 HA40 KA02 KA05 KA23 KA32 KA34 KA42 KA44 KA55 KA62 KA64 MA13 SA01 TA01 5J090 AA01 AA21A FA18 HA02 HA25 HA29 HA39 HA40 HN17 KA02 KA05 KA23 KA32 KA34 KA42 KA44 KA55 KA62 KA64 MA13 MN03 NN06 NN13 SA01 TA01 5J100 AA11 AA20 AA23 BA05 BB15 BB21 BC05 EA02 FA02 5K061 AA01 BB14 CC14

Claims (6)

[Claims] A first amplifier circuit and a second amplifier circuit for amplifying a signal received from a common input terminal; a first feedback amplifier circuit for feeding back an output signal of the first amplifier circuit; and a second amplifier circuit. A second feedback amplifier circuit for feeding back an output signal, wherein the first feedback amplifier circuit has an attenuation factor larger than an amplification factor of the first amplifier circuit, and the second feedback amplifier circuit is the second amplifier circuit. An amplifying device having an attenuation factor larger than the amplification factor. 2. The device according to claim 1, further comprising a first control circuit that controls one of the first amplifier circuit and the first feedback amplifier circuit and any one of the second amplifier circuit and the second feedback amplifier circuit. Characteristic amplification device. 3. The amplifying device according to claim 1, further comprising a second control circuit that controls at least one of the first feedback amplifier circuit and the second feedback amplifier circuit. 4. The method according to claim 1, wherein the first feedback amplification circuit and the second feedback amplification circuit
An amplifier device driving a common load and connecting a low-pass filter to an output. 5. The apparatus according to claim 3, wherein the second control means sets an amplification factor of the first feedback amplification circuit or the second feedback amplification circuit to an offset of an output of the first amplification circuit or the second amplification circuit. An amplifying device characterized in that the amplifying device is controlled according to the condition. 6. A communication device using the amplification device according to claim 1.