Patent GB-1045409-A (GB)
Title: Phase equalizers
Inventor: LINKE JOSEF MARIA
IPC: H03H7/20
Filed: 1964-06-11
Abstract: 1,045,409. Equalizers. HER MAJESTY'S POSTMASTER GENERAL. June 11, 1965 [June 11, 1964], No. 24338/64. Heading H3U An adjustable phase equalizer comprises a double differential transformer having a primary winding of (n 1  + n 2 ) turns and a secondary winding of (n 3  + n 4 ) turns, a primary winding tapping for connection to a source having an impedance R S , the free end of the primary winding part having n 1  turns connected together with a reference resistor to an adjustable reactance network, the reference resistor having a resistance R 0  such that R 0  = aRs where n 1 /n 2  = a - 1, the free end of the winding having n 2  turns connected by an attenuator to the secondary winding tapping, the free end of the secondary winding part having n 3  turns connected to a balancing resistor and the free end of the secondary winding part having n 4  turns connected to a load, the balance and load resistors having respective resistances R B  and RL such that R B  = bRL where b = n 3 /n 4 , the attenuator having an input impedance of a/a-1. Rs when its output is loaded by an impedance bc/b+1. Rs where c=R L /R S , and in which the transformer has a turns ratio such that Fig. 2 illustrates a phase equalizer circuit employing a single adjustable reactance network 2Z and suitable for use when that network has zero impedance at zero-frequency. The circuit has a double differential transformer T having a primary tapping P dividing the primary winding into a section TP1 having n 1  turns and a section TP2 having n 2  turns. A tapping S1 on the secondary winding divides it into two sections one of which TS1 has n 3  turns and the other TS2 has n 4  turns. The tapping P is connected to a terminal IT for connecting the circuit to a source S 0  having an impedance R S . The free end of the primary winding section TP1 is connected by a reference resistor R 0  to the impedance network 2Z and the free end of the primary winding section TP2 is connected by an attenuator ATT to the secondary tapping S1. In general the attenuator ATT will be asymmetrical. The free ends of the secondary winding sections TS1 and TS2 are grounded by a balancing resistor R B  and a load resistor RL respectively. A suitable form of construction of the adjustable reactance network 2Z is shown in Fig. 3 (not shown) and since the network has zero impedance at zero frequency, the impedance presented at zero frequency to the primary winding section TP1 is R 0 . The turns ratios of the transformer T are so proportioned that the input current from the source S 0  does not magnetize the transformer core if the impedance network 2Z is replaced by a short circuit; thus at zero frequency the core is not magnetized by the input current. At higher frequencies the reactance network 2Z gives rise to reflections which partly return to the source S 0  via the tapping P and partly are transmitted via the magnetic coupling of the transformer to the secondary winding. Under ideal conditions, none of the reflected energy is transmitted via the conductive path, i.e. via the attenuator ATT, to the secondary winding. Fig. 4 (not shown) shows a phase equalizer   employing a single adjustable reactance Z<SP>1</SP>/2   having infinite impedance at zero frequency. The circuit is similar to that of Fig. 2 except   that in Fig. 4 the reactance network Z<SP>1</SP>/2, a form of which is shown in Fig. 5 (not shown), is connected in parallel with the resistor R 0  and the polarity of the secondary winding sections TS1 and TS2 has been reversed.