Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1998-08-17
2001-09-11
Tsang, Fan (Department: 2746)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S090300, C455S575100, C343S702000, C343S701000
Reexamination Certificate
active
06289225
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to radiotelephones, and, more particularly, to retractable antenna systems for use with radiotelephones.
BACKGROUND OF THE INVENTION
Radiotelephones generally refer to communications terminals which provide a wireless communications link to one or more other communications terminals. Radiotelephones may be used in a variety of different applications, including cellular telephone, land-mobile (e.g., police and fire departments), and satellite communications systems.
Many radiotelephones, particularly handheld radiotelephones, employ retractable antennas which may be extended out of, and retracted back into, a radiotelephone housing. Conventionally, retractable antennas are electrically connected to a printed circuit board containing radio frequency circuitry located within a radiotelephone housing. A conventional radiotelephone antenna is typically interconnected with the radio frequency circuitry such that impedance of the antenna and the radio frequency circuitry are substantially matched. Conventionally, an antenna and radio frequency circuitry are matched at about 50 ohms (&OHgr;) impedance.
Impedance matching for retractable antennas may be difficult because antenna impedance may be dependent on the position of an antenna with respect to both a radiotelephone housing and internal radio frequency circuitry. When a retractable antenna is moved between extended and retracted positions, at least two different impedance states, may be exhibited.
Accordingly, with retractable antennas, it is generally desirable to provide an impedance matching system with dual circuits that provide an acceptable impedance match between an antenna and the radio frequency circuitry, both when the antenna is retracted, and when the antenna is extended. Unfortunately, dual impedance matching circuitry can be somewhat complex and can increase the manufacturing costs of radiotelephones.
In addition, separate sets of signal line terminals or contacts are often used with impedance matching circuits to electrically connect a respective matching circuit to an antenna element. Unfortunately, multiple feed contacts may add to the complexity of the design and manufacturing of radiotelephones. Furthermore, multiple feed contacts may require multiple mechanical parts, such as spring contacts, that may become unreliable over time.
Many of the popular hand-held radiotelephones are undergoing miniaturization. Indeed, many of the contemporary models are only 11-12 centimeters in length. Unfortunately, as radiotelephones decrease in size, the amount of internal space therewithin may be reduced correspondingly. A reduced amount of internal space may make it difficult for retractable antennas to achieve the bandwidth and gain requirements necessary for radiotelephone operation because antenna size may be correspondingly reduced. Furthermore, radiotelephone antennas may not function adequately when in close proximity to a user during operation, or when a user is moving during operation of a device. Close proximity to objects or movement of a user during operation of a radiotelephone may result in degraded signal quality or fluctuations in signal strength, known as multipath fading.
It is also becoming desirable for a radiotelephone antenna to be able to resonate over multiple frequency bands. For example, the Japanese Personal Digital Cellular (PDC) system utilizes two “receive” frequency bands and two “transmit” frequency bands. Accordingly, radiotelephone antennas used in the Japanese PDC system should preferably be able to resonate in each of the two receive frequency bands. Unfortunately, the ability to provide retractable antennas with adequate gain over multiple frequency bands may be presently limited because of size limitations imposed by radiotelephone miniaturization.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide simplified impedance matching between retractable radiotelephone antennas and internal radio frequency circuitry.
It is another object of the present invention to provide retractable radiotelephone antennas with impedance matching systems that can have fewer mechanical parts than conventional matching systems.
It is another object of the present invention to provide retractable antennas that can resonate over multiple frequency bands with sufficient gain for use within small personal communication devices such as radiotelephones.
These and other objects of the present invention are provided by a pivotable and retractable antenna that contains all the mechanical and electrical components necessary for connecting to, and matching the impedance of, radio frequency circuitry within an electronic device, such as a radiotelephone. An antenna, according to an embodiment of the present invention, includes a dielectric substrate with one end movably mounted to the housing of a radiotelephone and an opposite free end. The end movably mounted to the housing of a radiotelephone is configured to move into various positions to allow the dielectric substrate to have a first extended position, a second extended position and a retracted position. In a first extended position, the dielectric substrate extends along a longitudinal direction defined by the radiotelephone housing. In a second extended position, the dielectric substrate free end is extended outwardly from the housing and pivoted away from the housing in a direction transverse to the longitudinal direction of the housing. When in a second extended position, the effects of interference caused by a user's body can be reduced.
First and second radiating elements are disposed on the dielectric substrate adjacent the free end and are configured to resonate within respective first and second frequency bands. A first set of contacts are provided on the dielectric substrate and serve as means for electrically connecting the first and second radiating elements to the radiotelephone transceiver via a set of fixed contacts within the radiotelephone when the dielectric substrate is in a retracted position. The set of fixed contacts are in electrical communication with the transceiver.
Third and fourth radiating elements are disposed on the dielectric substrate between the free end and the end movably mounted to the housing and may be configured to resonate within the same first and second frequency bands as the first and second radiating elements, respectively. A second set of contacts are provided on the dielectric substrate and serve as means for electrically connecting the third and fourth radiating elements to the radiotelephone transceiver via the same set of fixed contacts within the radiotelephone when the dielectric substrate is in the second extended position.
The first and second radiating elements may resonate within the respective first and second frequency bands as quarter-wave antennas when the substrate is in the retracted position. The third radiating element may combine with the first radiating element to resonate within the first frequency band as a half-wave antenna when the substrate is in the second extended position. Similarly, the fourth radiating element may combine with the second radiating element to resonate within the second frequency band as a half-wave antenna when the substrate is in the second extended position.
A plurality of contacts may be provided along a side portion of the dielectric substrate that are configured to electrically connect accessory contacts, such as from a car cradle, to the radiotelephone transceiver when the dielectric substrate is in the first extended position. Because a separate set of contacts are utilized to connect an accessory to the transceiver, the first, second, third and fourth radiating elements are electrically disconnected from the transceiver when the dielectric substrate is in the first extended position.
Impedance matching components may be provided on the dielectric substrate to match the impedance of the third and fourth radiating elements when the dielectric substrate is in the secon
Hayes Gerard James
Rudisill Charles Albert
Winstead Russell Evans
Ericsson Inc.
Myers Bigel & Sibley & Sajovec
Smith Sheila
Tsang Fan
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