Matsushita Electric Industrial Co., Ltd.

Panasonic Corporation

Jyunji Itoh

Toshifumi Nakatani

Hideo Nakano

Tadayoshi Nakatsuka

Shinichi Osako

A variable gain amplifying apparatus has an amplifier, one or more first switching elements connected in parallel to the amplifier, and a phase shifter connected in series to the first switching element. The first switching element is enabled if the level of an input signal or an output signal is higher than a predetermined level, and the first switching element is disabled if the level of the input signal or the output signal is equal to or lower than the predetermined level. The amplifier does not operate when the first switching element is enabled, and the amplifier operates when the first switching element is disabled, and the amount of phase shift when the input signal is passed through the amplifier and phase shifter is substantially equal to the amount of phase shift when the input signal is passed through the first switching element.

Variable gain amplifying apparatus and wireless communication apparatus

A low-noise differential bias circuit is provided which obtains excellent noise characteristics while ensuring excellent distortion characteristics. A collector of a transistor Qis connected to a voltage supply point (Vcc) via a resistor R. A base of the transistor Qis connected to a base of a transistor Qvia resistors R, Rconnected in series. A connection point between the resistors R, Ris connected to the collector of the transistor Q. A collector of a transistor Qis connected to the voltage supply point at connection point A via a resistor R. A base of the transistor Qis connected to a base of a transistor Qvia resistors R, Rconnected in series. A connection point between the resistors R, Ris connected to the collector of the transistor Q. By this configuration, a high frequency ground is performed at the connection point A.

Low-noise differential bias circuit and differential signal processing apparatus

An amplifier circuit amplifies a signal inputted from an input terminal. A first feedback circuit is placed across an emitter of a bipolar transistor and an input of the amplifier circuit. A second feedback circuit is placed across the input and an output of the amplifier circuit for feeding the output of the amplifier circuit back to the input of the amplifier circuit. A phase change amount in the feedback circuit is determined by the values of an inductor and a capacitor. The values of these elements are selected so that a phase of a signal in which fundamental waves included in two feedback signals are combined and a phase of a signal in which second harmonics included in the two feedback signals are combined are shifted by approximately 180 degrees from a phase of a fundamental wave of an input signal.

Amplifier and frequency converter

An amplifier circuit amplifies a differential signal supplied by a pair of input terminals. A phase controller circuit is placed between the emitters of two bipolar transistors and the ground. A feedback circuit is placed across the input and the output of the amplifier circuit for feeding the output of the amplifier circuit back to the input thereof. A phase change amount in the amplifier circuit is determined by the values of two inductors, whereas a phase change amount in the feedback circuit is determined by the values of two resistances and capacitors. The values of these devices are selected so that a phase difference between an input signal and a feedback signal is approximately 180 degrees in a range from the frequency of a fundamental wave of the input signal to the frequency of a second harmonic thereof.

A front-end circuit which receives a first input signal and a second input signal, and outputs an output signal having a differential frequency between the first input signal and the second input signal includes: a first amplifier having an input terminal, a power supply terminal and a virtual ground; a second amplifier having an input terminal, a power supply terminal and a ground; and a mixer having a first and a second input terminals, a power supply terminal and a virtual ground. In the front-end circuit, the virtual ground of the mixer is dc-coupled to the power supply terminal of the first amplifier, the virtual ground of the first amplifier is dc-coupled to the power supply terminal of the second amplifier, the power supply terminal of the first amplifier and the second amplifier are ac-coupled to the first and the second input terminals, respectively, and the input terminal of the first amplifier and the input terminal of the second amplifier receive the first and the second input signals, respectively, and a power supply voltage is supplied to the power supply terminal of the mixer and the ground.

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Hirakata, Japan

Jyunji Itoh