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Wireless communication semiconductor integrated circuit device and wireless communication systemRelated Patent Categories: Telecommunications, Transmitter And Receiver At Same Station (e.g., Transceiver), With Transmitter-receiver Switching Or Interaction PreventionWireless communication semiconductor integrated circuit device and wireless communication system description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070202814, Wireless communication semiconductor integrated circuit device and wireless communication system. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION [0001] The present application is a continuation of application Ser. No. 10/948,183, filed Sep. 24, 2004, which claims priority from Japanese patent application No. 2003-342874 filed on Oct. 01, 2003, the content of which is hereby incorporated by reference. BACKGROUND OF THE INVENTION [0002] The present invention relates to a technique effective if applied to a gain programmable signal amplifier circuit, a received signal amplifier circuit employed in a wireless communication system and a receiving circuit which down-converts a high frequency received signal into a signal lying in an audio frequency band on a direct conversion system basis, and to, for example, a technique effective suitable for application to a high frequency semiconductor integrated circuit device (hereinafter called high frequency IC) incorporating therein programmable gain amplifiers that constitute a wireless communication system, and a wireless communication system with the high frequency semiconductor integrated circuit device built therein. [0003] A high frequency IC having frequency conversion of transmit-receive signals and a modem function has been used for recent cellular phones. A superheterodyne system which temporarily down-converts a received signal to an intermediate frequency signal and down-converts it to a signal lying in an audio frequency band, and a direct conversion system which down-converts a received signal to a signal lying in an audio frequency band are known for the conventional high frequency IC. The high frequency IC of the direct conversion system is configured in such a manner that an LNA (Low Noise Amplifier) amplifies a received signal and thereafter a mixer combines the received signal and a local oscillation signal, followed by being down-converted to a signal lying in an audio frequency band, and a high gain amplifier circuit amplifies the weak received signal to about 1500 times at the maximum and passes it to a baseband LSI which performs its baseband processing. [0004] The high gain amplifier circuit takes a configuration wherein since it amplifies the weak received signal while removing noise and a signal having an unnecessary frequency, low pass filters LPFs and programmable gain amplifiers (hereinafter abbreviated as PGAs) are alternately connected in several stages. Incidentally, since an analog amplifier circuit starting with PGA produces a DC offset due to variations in element, etc., offset cancellation is essential. [0005] As described above, the receiving circuit of the cellular phone using the plurality of PGAs has conventionally been provided with offset correction circuits every PGA in general. The receiving circuit has been configured so as to sequentially carry out offset cancellations in order from the first-stage PGA to the subsequent-stage PGAs. Such offset cancel operations of PGAs have been described in, for example, a patent document 1 (Japanese Unexamined Patent Publication No. 2003-152480). SUMMARY OF THE INVENTION [0006] Incidentally, although not described in the patent document 1, the offset cancel operations of PGAs are carried out in a state in which a pre-stage mixer is turned on and the LNA is turned off. The reason why the mixer is turned on, is that since the mixer also has an offset, the offset of the mixer and the offset of the first-stage PGA can be canceled out simultaneously when the mixer is held on upon the offset cancellation of the first-stage PGA. The reason why the offset cancellations of PGAs are performed in the turned-off state of the LNA, is that when the LNA is held on, a signal that leaks from a local oscillator is round-intruded into input terminals of the LNA via a semiconductor chip and a module substrate with the semiconductor chip mounted thereon, so that the mixer causes self-mixing, thereby generating a DC offset, which in turn is amplified by a high gain PGA section. [0007] Meanwhile, the self-mixing due to the round intrusion of the local oscillation signal into the LNA input terminals can be reduced to some extent by using differential type circuits as the LNA and mixer and inphase noise cancel operations of the differential amplifiers. However, when pairing of the positive-phase and negative-phase sides of both single-differential converters configured of baluns or the like connected between an antenna and the input terminals of the LNA, and a front end module is poor, the inphase noise round-intruded into the input terminals of the LNA cannot be canceled sufficiently. Further, since module substrates each having a high frequency IC mounted thereon are different in structure, size and wiring pattern depending on users, the amount of leakage of the local oscillation signal round-intruded into the input terminals of the LNA varies too. [0008] Therefore, the system for performing the offset cancellation of each PGA while the LNA remains off as described above is accompanied by the problem that when the LNA is turned on after the completion of the offset cancellation, the DC offset produced with self mixing due to the round intrusion of the local oscillation signal is amplified by the PGA. It has been revealed that although a shift in signal level due to such a DC offset has conventionally fallen within an allowable range, the dynamic range of an input to the baseband LSI also becomes narrow when the power supply voltage of the baseband LSI is lowered with a reduction in the voltage of a recent semiconductor integrated circuit, and hence a desired wave exceeds the dynamic range and is clipped even if the DC offset developed with self mixing due to the round intrusion of the local oscillation signal is the same as conventional, thereby causing a fear of degradation of reception sensitivity. [0009] An object of the present invention is to provide a wireless communication semiconductor integrated circuit device (high frequency IC) of a direct conversion system, which is capable of canceling a DC offset developed with self mixing of a mixer due to round intrusion of a local oscillation signal into LNA input terminals and thereby improving reception sensitivity. [0010] Another object of the present invention is to provide a wireless communication semiconductor integrated circuit device (high frequency IC) of a direct conversion system, which causes no degradation of reception sensitivity even if the dynamic range of an input to a circuit supplied with an amplified received signal is narrow. [0011] A further object of the present invention is to provide a wireless communication semiconductor integrated circuit device (high frequency IC) of a direct conversion system, which has stable reception sensitivity without being affected by the characteristic of a mounted substrate. [0012] The above, other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings. [0013] Summaries of representative ones of the inventions disclosed in the present application will be explained in brief as follows: [0014] A first invention of the present application provides a receiving circuit of a direct conversion system, including a low noise amplifier which amplifies a differential received signal, a mixer which combines the amplified received signal and an oscillation signal having a predetermined frequency to thereby perform frequency conversion, and a high gain amplifier circuit in which a plurality of programmable gain amplifiers and a plurality of filters which eliminate noise of the received signal and an unnecessary wave, are connected in a multistage and which is configured such that an amplification factor is varied according to the level of the received signal, wherein the low noise amplifier is brought to a non-operating state to thereby allow execution of an offset cancel operation of the corresponding programmable gain amplifier on the pre-stage side of the high gain amplifier circuit, and thereafter the low noise amplifier is brought to an operating state to thereby allow execution of an offset cancel operation of the final-stage programmable gain amplifier. [0015] According to such means, even if a DC offset occurs with self mixing of the mixer due to round intrusion of a local oscillation signal into LNA input terminals, the low noise amplifier is brought to the operating state to execute the offset cancel operation of the final-stage programmable gain amplifier, whereby offset cancellation can be performed inclusive of the DC offset of the final-stage programmable gain amplifier and the DC offset produced with the self mixing of the mixer. [0016] Here, preferably, a register or control bit is provided which is capable of setting whether such a series of offset cancel operations that the low noise amplifier is brought to the non-operating state to allow the execution of the offset cancel operation of the programmable gain amplifier on the pre-stage side of the high gain amplifier circuit and thereafter the low noise amplifier is brought to the operating state to allow the execution of the offset cancel operation of the programmable gain amplifier of the final stage. Thus, such a system that the low noise amplifier is brought to the operating state to allow the execution of the offset cancel operation of the final-stage programmable gain amplifier, thereby increasing the DC offset on the contrary is capable of avoiding selective execution of such an offset cancel operation by virtue of the setting of the register. [0017] A second invention of the present application provides a receiving circuit of a direct conversion system, including a low noise amplifier which amplifies a differential received signal, a mixer which combines the amplified received signal and an oscillation signal having a predetermined frequency to thereby perform frequency conversion, and a high gain amplifier circuit in which a plurality of programmable gain amplifiers and a plurality of filters which eliminate noise of the received signal and an unnecessary wave, are connected in a multistage and which is configured such that an amplification factor is varied according to the level of the received signal, wherein when the high gain amplifier circuit is operated with high gain, the low noise amplifier is brought to a non-operating state to allow execution of an offset cancel operation of the programmable gain amplifier on the pre-stage side of the high gain amplifier circuit, and thereafter the low noise amplifier is brought to an operating state to allow execution of an offset cancel operation of the final-stage programmable gain amplifier, and wherein when the high gain amplifier circuit is operated with low gain, the low noise amplifier is brought to the operating state to execute in sequence the offset cancel operations of all programmable gain amplifiers of the high gain amplifier circuit from, for example, the first stage to the final stage. [0018] According to the above means, even if a DC offset occurs with self mixing of the mixer due to round intrusion of a local oscillation signal into LNA input terminals, the low noise amplifier is brought to the operating state to execute the offset cancel operation of the final-stage programmable gain amplifier where the high gain amplifier circuit is operated with the high gain, whereby offsets can be canceled inclusive of the DC offset of the final-stage programmable gain amplifier and the DC offset produced with the self mixing of the mixer. Further, when the high gain amplifier circuit is operated with the low gain, the low noise amplifier is brought to the non-operating state to execute in sequence the offset cancel operations of all programmable gain amplifiers of the high gain amplifier circuit from the first stage to the final stage, thereby making it possible to prevent each DC offset from increasing due to an interference wave inputted to the LNA and prevent the offset cancel operations from failing. [0019] Here, preferably, a register is provided which sets gain reaching a threshold value for determining which one of the two offset cancel operations should be executed. Thus, the suitable offset cancel operation can be performed automatically by setting the optimum threshold value according to a system to be applied. [0020] Advantageous effects obtained by representative ones of the inventions disclosed in the present application will be explained in brief as follows: [0021] According to the present invention, a wireless communication semiconductor integrated circuit device (high frequency IC) of a direct conversion system is capable of canceling a DC offset developed with self mixing of a mixer due to round intrusion of a local oscillation signal into LNA input terminals. Therefore, even if the dynamic range of a subsequent-stage circuit is narrow, it is possible to prevent a desired wave from being clipped and thereby improve reception sensitivity. Continue reading about Wireless communication semiconductor integrated circuit device and wireless communication system... 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