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Integrated millimeter-wave quadrature generatorRelated Patent Categories: Telecommunications, Receiver Or Analog Modulated Signal Frequency Converter, Frequency Modifying Or Conversion, With Specified Local Oscillator Structure Or CouplingIntegrated millimeter-wave quadrature generator description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080051054, Integrated millimeter-wave quadrature generator. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention relates generally to on-chip oscillator signals, and, more specifically, to producing quadrature signals on-chip using a differential coupler. BACKGROUND [0002] With recent progress in the semiconductor technology and packaging engineering, more portable personal communication systems are made available, as the dimensions of these circuits become smaller and the transmission lines are being formed with shorter distances from each other. [0003] In frequency conversion systems, such as millimeter-wave radios, for example, discrete semiconductor components with low integration levels are assembled. These systems are often assembled using expensive and bulky waveguides and package-level or board-level microstrip structures to interconnect semiconductors. [0004] Power couplers are used widely in frequency conversion systems such as the millimeter radios to divide power in an input path into two or more paths. In these millimeter radios, the power couplers used may include microstrip branch lines of different lengths to generate on-chip oscillator signals of different phases. For the purpose of shifting the phase by 90.degree., for example, quarter wave-length transmission lines may be used. As the dimension of the power coupler is reduced, the distances between the branch lines are also reduced. A known power coupler is the branch-line directional coupler. [0005] Shown in FIG. 1 is an exemplary branch-line directional coupler 14 with four branch lines 10, 12. As shown in FIG. 1, the branch lines 10, 12 are a quarter-wavelength long at the center design frequency, connected at connecting ports 1-4. Branch lines 10 connecting ports 1 and 2, and ports 3 and 4, have a characteristic impedance of Zo/1.414. Branch lines 12 connecting ports 2 and 3, and ports 1 and 4, have a characteristic impedance of Zo. When port 1 is driven by a signal, the voltage at port 3 lags the voltage at port 2 by 90.degree., and the voltage at port 4 is at a null (i.e. no output). SUMMARY OF THE INVENTION [0006] In accordance with the exemplary aspects of this invention, a frequency conversion system is provided. [0007] In the exemplary aspects of this invention, an off-chip signal is provided to a frequency conversion system. The off-chip signal is then applied to a differential coupler implemented entirely on-chip. The coupler produces differential quadrature signals, which are then buffered and applied to a quadrature mixer. [0008] In the exemplary aspects of this invention, the coupler is a differential branch-line directional coupler implemented entirely on-chip using microstrip transmission lines. [0009] In the exemplary aspects of this invention, the coupler is made up of a plurality of rings and a plurality of underpasses connecting ports of the rings. In these exemplary aspects, each of the plurality of rings is made up of a plurality of branch lines of varying length and characteristic impedance, and an underpass. [0010] In various exemplary aspects of this invention, each of the plurality of rings is made up of four branch , each branch line having an electrical length of one-quarter wavelength at the center design frequency. [0011] In various exemplary aspects of this invention, coupling between the plurality of branch lines of the rings is varied. [0012] In accordance with the exemplary aspects of the present invention, the frequency conversion system is a direct-conversion downconverting receiver. [0013] In accordance with other exemplary aspects of the present invention, the frequency conversion system is a direct-conversion upconverting transmitter. [0014] According to the exemplary aspects of this invention, a completely integrated quadrature generator at millimeter-wave frequencies is achieved, without taking the signals off-chip to a branch-line directional coupler fabricated on a circuit board or ceramic substrate. In these exemplary aspects, the quadrature generation is completed entirely on-chip. Accordingly, advantages such as reduction in cost and less power usage may be accomplished, since sending signals off-chip at high frequencies which typically requires buffer amplifiers to compensate for package and board loss may be avoided. [0015] One exemplary aspect of this invention is to implement a millimeter-wave radio entirely on a silicon integrated circuit, while producing accurate quadrature, that is, 0.degree. and 90.degree. phase shifted, local oscillator signals on-chip, starting with a differential pair of lower-frequency pilot signals. BRIEF DESCRIPTION OF THE DRAWINGS [0016] FIG. 1 shows an exemplary well-known coupler. [0017] FIG. 2 shows an exemplary frequency conversion system embodying the exemplary aspects of the present invention. [0018] FIG. 3 shows an exemplary signal processor embodying the exemplary aspects of the present invention. [0019] FIG. 4 shows an exemplary coupler in accordance with the exemplary aspects of the present invention. [0020] FIG. 5 shows a flowchart for frequency conversion in accordance with one exemplary aspect of the present invention. Continue reading about Integrated millimeter-wave quadrature generator... Full patent description for Integrated millimeter-wave quadrature generator Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Integrated millimeter-wave quadrature generator patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. 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