Patent ID: 6573811
Filing Date: 2003-06-03
Classification: H03H

Abstract:
A resistor tuning network for connection in series with a resistor to be tuned, comprising:a first resistor having a fixed resistance, an input for connection to a resistor to be tuned, and an output; and a resistor ladder network connected between the input and output in parallel with the first resistor, the ladder network having an input and first and second output terminals, the first output terminal being connected to said output; the ladder network having a first line comprising a plurality of first arms connected in series with the input and first output terminal and nodes between each pair of arms, each arm having an identical resistor R, a second line connected to said first output terminal, and a third line connected to said second output terminal; a series of shunt arms, each shunt arm having a first end connected to a respective node and a second end, a resistor which has a value which is a multiple of R and a switch in series between the first and second end of each shunt arm, each switch having a first, closed position connecting the shunt arm to the second line and a second, open position connecting the shunt arm to the third line, such that the resistance of the ladder network is varied dependent on the switch positions and is at a maximum value when all switches are closed and a minimum value when all switches are open, whereby a resistance can be tuned by varying the switch positions in the ladder circuit; and wherein said resistor to be tuned is a third resistor R3 connected in series with the parallel connected first resistor and ladder network.