Jurianto Joe

RF and IF ports matching circuit synthesis for a simultaneous conjugate-matched mixer using quasi-linear analysis

A quasi-linear two-port approach between RF and IF ports to design a simultaneous conjugate-matched mixer is presented in this paper. Conventionally, mixer design is treated as a nonlinear three-port device problem. Nonetheless, with the exception of the large-signal local oscillator (LO) that exists at the LO port, the input RF and output IF signals that exist at the RF and IF ports, respectively, are small signals. Consequently, mixers can be approximated as bilateral quasi-linear two-port circuits with a time-variant transfer function between the RF and IF ports, in which the LO port of the mixer is treated as part of the two-port network. With this approximation, it can be shown mathematically that the optimum source and load matching networks required for attaining simultaneous conjugate match at the RF and IF ports are actually time invariant, thus implying that it is possible to synthesize these optimum impedance values. This proposed mixer design technique, together with the equations derived, are verified with block-diagram simulation and experimental measurements of two 2.4-GHz RF/420-MHz IF double-balanced diode mixers.

A novel 360/spl deg/ analog phase shifter with linear voltage phase relationship

A novel 360/spl deg/ analog phase shifter with linear voltage phase relationship utilizing two parallel reflective networks is described. Conventionally, two 180/spl deg/ reflective networks connected in parallel are required to form a 360/spl deg/ linear phase shifter. Such a requirement does not apply in the phase shifter described in this paper. Each reflective network is composed of either two varactors connected in parallel with properly selected transmission line length or one varactor in parallel with open or short stub to form a parallel resonant circuit. The length of the transmission line in each of the reflective networks is selected such that it has nonlinear voltage-phase shift relations, but when these two reflective branches are connected in parallel, they will produce a linear voltage-phase relationship. Measurement results will be presented.

Large-signal diode modeling-an alternative parameter-extraction technique

An alternative numerical optimization method of large-signal equivalent-circuit diode modeling using dc and small-signal S-parameter measurements is described. In general, there are two ways to extract the equivalent-circuit parameters to model a nonlinear device such as a diode. They are based on numerical optimization or noniterative analytical procedure. The former is usually better in approximating the device response. Nevertheless, it requires arbitrary selection of a voltage-dependent S-parameter set to obtain the voltage-independent parameters. In this alternative numerical optimization method, an arbitrary selection of a voltage-dependent S-parameter set to obtain the voltage-independent parameters is not required. Validation of this parameter-extraction technique is done via modeling a forward-biased tunnel diode and a reverse-biased varactor diode. The models are further verified by implementing them in designing and developing an oscillator and a voltage-controlled oscillator.

ISM band active array with electronically controlled element weighting

A four-element active array with electronically controlled element weighting is presented. This active array consists of variable gain active antennas with gain control accomplished through changing the amplifier biasing. Matching across the transistor bias range is implemented by judiciously incorporating varactor diodes in the matching circuits in order to ensure good input and output match. This active array is capable of forming a desired radiation pattern via tuning the appropriate amplitude and phase control voltages. Examples of measured radiation pattern for this active array, shaped using some of the standard antenna pattern synthesis methods, are also presented. These radiation patterns agreed well with those predicted by simulation within the limits of experimental results.