Patent GB-1412314-A (GB)
Title: Circuit arrangement for matching an aerial load network to a transceiver
IPC: H03H7/40
Filed: 1973-10-26
Abstract: 1412314 RF couplings TELECOMMUNICATIONS RADIOELECTRIQUES ET TELEPHONIQUES 26 Oct 1973 [31 Oct 1972] 49951/73 Heading H4A An arrangement for matching an aerial 1, Fig. 1, connected to a terminal 2 thereof, to a transceiver connected to a terminal 3 thereof, comprises a load adaptor 4 having first and second adjustable reactive elements 5, 6. In a first mode of operation in which the real part of the load network constituted by the aerial is greater than the resistance presented by the transceiver, an input signal P is given to a mode selecting circuit 16 which results in a control signal to a switch 15 to effect closure of a contact R. The element 5 is put in series with the parallel combination of the aerial and the element 6, and the reactance of the element 6 is then adjusted by a first control means until the real part of the impedance presented by the arrangement at the terminal 3 is substantially equal to the resistance of the transceiver. Matching is completed by adjusting the reactance of the element 5 using another control means. In a second mode of operation in which the real part of the admittance of the load network is greater than the conductance presented by the transceiver, the contact T of the switch 15 is closed. The element 6 is put in parallel with the series combination of the aerial and the element 5, and the reactance of the element 5 is then adjusted by a second control means until the real part of the admittance presented by the arrangement at the terminal 3 is substantially equal to the conductance of the transceiver. Matching is completed by adjusting the reactance of the element 6 using another control means. As described, the first control means (used initially in the first mode of operation) is a resistance discriminator 10, the output terminal 13 of which is connected to a control terminal 8 of the element 6 via switches 18, 19, 20 and an amplifier 17, said switches being controlled by signals from the mode selecting circuit 16. The discriminator 10 includes a coil 29 coupled to the line between the adaptor 4 and the terminal 3, and with a paralleling resistor 30. A capacitor 31 is connected on one side to said line and on the other side to one end of the coil 29, a diode 32, and to one input of a difference amplifier 35. A second capacitor 34 is also connected on one side to said line, and is connected on the other side to a second diode 33, and to the other input of difference amplifier 35. By suitably proportioning the component values a positive or a negative output appears at the terminal 13 depending whether the real part of the impedance appearing at the adaptor 4 is larger or smaller than the resistance of the transceiver. The second control means (used initially in the second mode of operation) is a conductance discriminator 9, the output terminal 12 of which is connected through to a control terminal 7 of the element 5 when in use. This discriminator is somewhat similar to the discriminator 10, but instead of the capacitor 34 there is provided a second coil with a paralleling resistor which is coupled to the line between the adaptor 4 and the terminal 3. By suitably proportioning the component values a positive or a negative output appears at the terminal 12 depending whether the real part of the admittance appearing at the adaptor 4 is larger or smaller than the conductance of the transceiver. To complete matching in the first mode of operation, the element 5 may be adjusted using the discriminator 9, and to complete matching in the second mode of operation, the element 6 may be adjusted using the discriminator 10. Alternatively, in either mode, matching may be completed using a phase discriminator 11, which gives an output representative of the difference in phase between the current and the voltage at the terminal 3. The adjustable reactive elements 5, 6 may each comprise a variable reactance in combination with fixed reactances which may be bridged across when not required, thereby providing efficient operation in successive segments of a wide band of frequencies (Fig. 4, not shown).