Renesas Technology Corp.

Ttpcom Limited

Renesas Electronics Corporation

Hitachi Ulsi Systems Co., Ltd.

Hitachi Device Engineering Co., Ltd.

Hitachi Advanced Digital, Inc.

Koichi Yahagi

Tatsuji Matsuura

Masumi Kasahara

Robert Astle Henshaw

Hiroaki Matsui

Kazuhiko Hikasa

Ryoichi Takano

Toshihito Habuka

Naoto Inokawa

Kiyoharu Ozaki

Satoshi Tanaka

Taizo Yamawaki

Yasuyuki Okuma

Masamichi Tanabe

Ryoji Furuya

Fumiaki Matsuzaki

Masachika Oono

A D.C. offset canceling and gain adjusting techniques permitting completion of correction of D.C. offsets and gain adjustment of amplifiers for amplifying reception signals in a radio communication system are provided. A communication semiconductor integrated circuit has a plurality of low-pass filters and variable gain amplifiers which are alternately connected in multiple stages, and high gain amplifier circuits for amplifying reception signals to a predetermined amplitude level. Offset cancellation values are generated by detecting D.C. offsets of amplifiers for amplifying reception signals according to a set gain, and stored into a memory, and read out of the memory to cancel the D.C. offsets of the amplifiers when starting reception and altering the gain. Gain setting in a high gain amplifying section is accomplished using rough and precise settings.

Communication semiconductor integrated circuit, radio communication system, and adjustment method of gain and offset

A D.C. offset canceling technique and a gain adjusting technique permitting completion of correction of D.C. offsets and gain adjustment of amplifiers for amplifying reception signals in a relatively short period of time in a radio communication system, such as a wireless LAN, are to be provided. A communication semiconductor integrated circuit (high frequency IC) has a plurality each of low-pass filters and variable gain amplifiers which are alternately connected in multiple stages, and high gain amplifier circuits for amplifying reception signals to a predetermined amplitude level while eliminating unnecessary waves. Offset cancellation values are generated by detecting in advance D.C. offsets of amplifiers for amplifying reception signals according to a set gain, and stored into a memory, and read out of the memory to cancel the D.C. offsets of the amplifiers at the time of starting reception and altering the gain. Gain setting in a high gain amplifying section for amplifying reception signals is accomplished in two steps, rough setting and precise setting.

In one embodiment, a PLL circuit is provided with a plurality of pull-in operation modes for pulling a voltage across a filter capacitor (C, C) in a lock-up voltage, and with a register (CRG) for designating one of the plurality of pull-in operation modes. The pull-in operation is performed in accordance with a setting value in the register.

Communication semiconductor integrated circuit device and a wireless communication system

A transmission oscillator of differential output configuration is incorporated into a high frequency IC. Further, an equivalent impedance having an impedance equivalent to the impedance connected with a regular output terminal is provided. Or, a dummy external terminal for outputting transmit signals in opposite phase is provided. One of the differential outputs of the transmission oscillator is inputted to the power amplifier through the regular output terminal. The other of the differential outputs is connected to the equivalent impedance or the dummy external terminal.

High frequency semiconductor integrated circuit device, wireless electric unit and wireless communication system

An orthogonal modulating circuit for modulating signals of two oscillation frequencies differing in phase by 90&#xb0; with transmission data (I and Q) is used in common for a plurality of bands, an LC resonance circuit comprising inductances L and a capacitor C is used as the output load on the orthogonal modulating circuit instead of resistors commonly used according to the prior art, and the values of L or C constituting the resonance circuit are switched over between each other according to the transmission band.

Semiconductor integrated circuit for communication

A wireless communication system, which is provided with a PLL circuit having a plurality of oscillators and is capable of processing two or more transmit and receive signal different in frequency band from one another according to the switching between the oscillators, has a reset means which resets a voltage applied to each of filter capacitors lying within the PLL circuit to a predetermined voltage when the switching between the oscillators is performed.

Wireless communication system

If a transmission oscillator is incorporated into a communication semiconductor integrated circuit, such as high a frequency IC, constituting a wireless communication system, a problem arises. The accuracy of control of the output power of a power amplifier is degraded. This degradation in accuracy is caused by coupling noise between the output pins of the transmission oscillator and an input pin for detection signals (feedback signals) associated with the output level of the power amplifier or crosstalk. To prevent this, a transmission oscillator of differential output configuration is incorporated into a high frequency IC and an impedance equivalent to the impedance connected with a regular output terminal or a dummy external terminal for outputting transmit signals in opposite phase is provided.

A transmitter is provided which includes a transmitting circuit that does not require a high-performance low noise VCO restricting cost reduction thereof and that can reduce the number of parts without requiring an RF filter. A direct conversion that does not require a transmission VCO is applied to the transmitting circuit. In order to achieve noise reduction in a receiving band, low-pass filters are provided a IQ input sections of a modulator that converts IQ signals into RF signals. In comparison with a conventional transmitter using offset PLL, an external VCO required in addition to an RF integrated circuit, a power amplifier, and a front end circuit is reduced. Even in current transistor performance, by using a filter having rapid waveform characteristics such as a SAW more inexpensive than the VCO, or the like, it is possible to provide a GSM/GSM 1800/GSM1900 triple band transmitter.

Growing community of inventors

Takasaki, Japan

Koichi Yahagi