This paper is devoted to design method of dual-band phase shifters, which can execute the assigned to them functions in operating bands for example of two different telecommunication standards. In the circuit of phase shifter, where the differential phase shift is provided by the switching of channels of passing the signal the parameters of switching elements do not determine this shift unlike the other well-known circuits. However in case of bad matching and isolation of switches the frequency bands are narrowed, the losses and imbalance of amplitudes in two states are grown. The dual-frequency matching and isolation are reached in the SPMT switch by means of impedance transformers which can be located on the input of switch before branching, or in channels after the switching elements before outputs. The methods of calculation of such dual-frequency transformers based on the asymmetrical one-stub circuit and the symmetrical two-stub circuit, and also the methods of calculation of circuits which are needed for realization of reactance with the appropriate values at two operating frequencies is offered. The calculation and simulation of the SPDT switch for use as a part of the phase shifter with operating frequencies of 2,4/5,2 GHz was executed by these methods. For obtaining of arbitrary difference phase shift at two frequencies the replacement of line segments in channels of phase shifter by the dual-frequency equivalent circuits is carried out. The method of calculation of such P-type circuit for replacement of a segment with different values of characteristic impedance and electrical length at operating frequencies is offered. The offered approach was investigated on examples of calculation and simulation of the dual-frequency phase shifters with identical 450/450 and distinct 450/900 differential phase shifts at operating frequencies 2,4/5,2 GHz and with shifts 450/—450 at frequencies 0,95/2,15 GHz.
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