METHODS AND APPARATUS FOR MATCHING AN ANTENNA

• US 20100244978A1
• Filed: 04/17/2008
• Published: 09/30/2010
• Est. Priority Date: 04/19/2007
• Status: Active Grant

• Current Assignee: Cantor Fitzgerald Securities (Cantor Fitzgerald, L.P.)
• Original Assignee: Cantor Fitzgerald Securities (Cantor Fitzgerald, L.P.)
• Inventors: Ramachandran, Prasadh, Annamaa, Petteri, Koskiniemi, Kimmo, Milosavljevic, Zlatoljub
• Granted Patent: US 8,466,756 B2
• Time in Patent Office: Days
• US Class Current: 333/33
• CPC Class Codes: H03H 7/38 Impedance-matching networks
• CPC Class Codes: H04B 1/0458 Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages matching circuits in general H03H

Abstract

A method and an arrangement for matching the antenna of a radio device in transmitting condition. The antenna impedance in the output of the power amplifier of a transmitter is adjusted by means of a π-shaped reactive matching circuit, the component values of which can be selected from a relatively wide array of the alternatives. The component values are selected by means of the multiple-way switches, which only are located in the transverse branches of the matching circuit. The switches are set (706) by the control unit, input variables of which being the SWR value provided by the directional coupler, the operating band used each time and a value of the transmitting power. The matching is based on an adjusting process to be executed at regular intervals, in which process the control unit tries different combinations of the switch states and finally selects (710) the combination, which brings the lowest SWR value. In the beginning of the adjusting process the control unit reduces (705), on grounds of the current values of the input variables, the number of the combinations to be tried. The antenna matching maintains relatively good, although the internal output impedance of the amplifier and the impedance from the output towards the antenna would strive to differ from each other for external reasons, a band changing or a change in the output power.

Claims

1-9. -9. (canceled)

10. A method for matching an antenna of a radio device in which a standing wave ratio (SWR) value of a signal to be transmitted in a transmission path of the antenna is provided and a reactive pi-shaped matching circuit in the transmission path between a power amplifier of a transmitter and the antenna is adjusted to optimize a load impedance of the power amplifier, the matching circuit adjusted by a plurality of multiple-way switching elements located in transverse portions associated with the matching circuit, said method comprising:

reading an information associated with an operating band that is in use;

defining a trial array comprised of a subset of state combinations, said trial array being substantially smaller than a total array of a plurality of state combinations of said multiple-way switching elements, said act of defining utilizing at least a certain value of the transmitting power, said information associated with the operating band that is in use, and the SWR value;

setting the switching elements of the matching circuit to each of the states associated with the subset of state combinations of the trial array;

determining the SWR value of the signal to be transmitted in each state and determining the lowest one of the SWR values determined;

setting the switches of the matching circuit to the state corresponding to the lowest one of the SWR values determined; and

repeating the acts of reading, defining, determining and setting at a regular interval.

11. The method of claim 10, wherein said certain value of the transmitting power comprises a current set value of the transmitting power.

12. The method of claim 10, wherein said trial array is defined according to the method comprising:

addressing a memory by means of at least the information associated with the operating band that is in use, the memory including a plurality of optimal state combinations for different operating bands and at least one transmitting power based on measurements made with the radio device;

setting the states of the switching elements in the matching circuit in accordance with the state combination retrieved from said memory;

reading the SWR value of the signal to be transmitted;

defining based at least in part on the read SWR value and current switching element states a first state combination which is arranged to correct a matching error if it is inductive, and a second state combination, which is arranged to correct the matching error if it is capacitive; and

determining the SWR values of the signal to be transmitted corresponding to the first and second state combinations.

13. The method of claim 12, wherein said trial array comprises the first state combination correcting an inductive matching error, and the second state combination correcting a capacitive matching error.

14. The method of claim 12, wherein the adjustment of the matching circuit is made more accurate by defining at least two state combinations which are arranged to correct inductive or capacitive matching error based on the determination of which type of correction has been found to provide a better SWR value, said at least two state combinations comprising said trial array.

15. An apparatus for matching an antenna of a radio device, wherein a transmitter of the radio device comprises a power amplifier controllable by its output power and a transmission path from the power amplifier to the antenna, the apparatus comprising:

a directional coupler in said transmission path to measure a level of a signal transmitted to the antenna and of a signal reflected from the antenna;

apparatus configured to determine a standing wave ratio (SWR) value of a signal in the transmission path of the antenna based at least in part on the measured signals provided with the directional coupler;

a pi-shaped adjustable reactive matching circuit with a control unit, and farther comprising a longitudinal portion of the matching circuit that has a constant capacitance or inductance, and a plurality of transverse portions comprising at least one multiple-way switch, a common terminal of which is coupled to a separate conductor of said transmission path and wherein each change-over terminal is coupled to a ground conductor of the transmission path through a reactive element, the control unit having a first input adapted for operative coupling to a setting unit of an operating band of the radio device, and the control unit being operatively coupled to said directional coupler from its input side, and to said at least one switch in the matching circuit from its output side so as to permit setting of the switches, the control unit comprising;

apparatus configured to define a trial array of the state combinations of the switches in the matching circuit based at least in part on a certain value of the transmitting power, an information associated with the operating band and the SWR value;

apparatus configured to set the switches of the matching circuit in turn to the states according to each state combination of the trial array to determine the SWR values correspond to these combinations;

apparatus configured to compare the determined SWR values and for finding the lowest one of them; and

apparatus configured to start an adjusting process of the antenna matching at regular intervals.

16. The apparatus of claim 15, characterized in that each transverse portion of the matching circuit comprises two multiple-way switches, and each multiple-way switch comprises four change-over terminals.

17. The apparatus of claim 15, characterized in that the control unit is based on a processor and comprises a central processing unit, a memory, input interfaces, output interfaces and a program in accordance with the adjusting process stored in the memory.

18. The apparatus of claim 15, characterized in that said multiple-way switches are implemented by a pseudomorphic high electron mobility transistor (PHEMT) or a micro electro mechanical system (MEMS) technique.

19. A method for matching an antenna of a radio device, said method comprising:

adjusting an impedance value of a reactive matching circuit coupled to said antenna, said act of adjusting being made based at least on;

(1) an operating band signal indicative of the current operating band of a transmitter associated with the radio device;

(2) a power level signal indicative of the current transmitting power of the transmitter; and

/or (3) one or more impedance signals indicative of an impedance mismatch associated with a transmitted signal.

20. The method of claim 19, wherein said act of adjusting further comprises:

defining a set of reactive matching circuit switching element combinations;

setting said reactive matching circuit to each of said set of switching element combinations;

determining a standing wave ratio (SWR) value for each of said combinations;

choosing a lowest one of said SWR values; and

adjusting said reactive matching circuit based at least in part on said lowest one of said SWR value.

21. The method of claim 20, wherein said act of defining further comprises:

selecting a first set of state combinations based on a defined operating band and a defined transmitting power of the radio device;

setting the reactive matching circuit to each of the set of switching element combinations associated with the first set of state combinations;

obtaining an SWR value for each of the switch combinations of the first set;

defining a first state combination based at least in part on the obtained SWR value and current switching element states to correct a matching error if it is inductive; and

defining a second state combination based at least in part on the obtained SWR value and current switching element states to correct a matching error if it is capacitive.

22. The method of claim 21, wherein said defined set of reactive matching circuit combinations comprises said first state combination and said second state combination.

23. An apparatus for matching an antenna of a radio device, said apparatus comprising:

a power amplifier comprising a power measuring signal output interface;

a directional coupler comprising an impedance measuring signal output interface;

a control unit coupled to said power measuring signal output interface and said impedance measuring signal interface; and

a reactive matching circuit controlled at least in part by said control unit;

wherein said power amplifier, directional coupler and reactive matching circuit are positioned along a transmission path of said radio device.

24. The apparatus of claim 23, wherein the reactive matching circuit comprises a plurality of multi-state switchable elements.

25. The apparatus of claim 24, wherein each of the multi-state switchable elements is coupled to said transmission path of said radio device.

26. The apparatus of claim 25, wherein the transmission path within said reactive matching circuit comprises a plurality of transverse portions, each transverse portion of the matching circuit comprising two multi-state switchable elements with each multi-state element comprising four change-over terminals.

27. The apparatus of claim 25, wherein said control unit comprises:

a central processing unit;

a computer readable apparatus comprising a memory coupled to said central processing unit;

an input interface; and

an output interface;

wherein said computer readable apparatus has at least one computer program stored thereon, the at least one computer program comprising a plurality of computer executable instructions that when executed by the central processing unit;

read a plurality of input signals received via said input interface;

execute an algorithm based at least in part on said plurality of signals; and

output a plurality of output signals via said output interface.

28. The apparatus of claim 27, wherein said plurality of output signals adjust the impedance characteristics associated with said reactive matching circuit.

29. The apparatus of claim 28, wherein said multi-state switchable elements are selected from the group consisting of a pseudomorphic high electron mobility transistor (PHEMT), and a micro electro mechanical system (MEMS) technique.