Automatic antenna tuner for low-cost mobile radio
US5589844A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 6, 1995 |
| Grant date | Dec 31, 1996 |
| Priority date | — |
| Expiry date | Jun 6, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03H7/38
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
An automatic antenna tuner which conjugately matches the impedance of an electrically small antenna to the impedance of a transmit amplifier output stage by using a pi-type impedance matching network with adjustable capacitive circuit components which are preferably implemented using a low cost escapement mechanism. During an initial set up tuning procedure, a resistive Wheatstone bridge detector is disposed between the output of the power amplifier and the input to the pi network, to feedback a measure a degree of match of the pi network to a controller. The capacitive elements in the legs of the pi network are then electromechanically adjusted under the operator of the controller until an optimum setting is found. These initial impedance values are determined for each frequency in an operating range and then stored in a non-volatile memory. As a second step in the tuning procedure, a fine adjustment is made to the stored optimum impedance values just prior to transmission, to accommodate changing environmental conditions and the like.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.