Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
2001-11-21
2004-06-29
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S109000, C333S136000
Reexamination Certificate
active
06756859
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to the field of radio frequency (R.F.) circuits and more particularly to an R.F. antenna switch.
2. Discussion of the Prior Art
R.F. switches are commonly used in R.F. applications such as R.F. transceivers known from WO 88/00760. WO 88/00760 concerns R.F. transceivers having an R.F. antenna switch for switching an antenna path and an R.F. local oscillator switch for switching a local oscillator signal path.
The R.F. antenna switch is used to route a common antenna path to either a receiver block or a transmitter block of the R.F. transceiver. The antenna switch essentially consists of two PIN diode switching elements and a one-quarter wavelength transmission line. When the two PIN diodes are switched on, a transmitter port is connected to an antenna port through the first PIN diode and a receiver port is connected to ground through the second PIN diode. When the two PIN diodes are switched off, the transmitter port is disconnected from the antenna port and the receiver port is connected to the antenna port through the transmission line.
The R.F. local oscillator switch according to WO 88/00760 is used to route the local oscillator signal to either a mixer of the receiver block or to an exciter of the transmitter block. The local oscillator switch essentially consists of two PIN diode switching elements and an unequal power splitter in the form of a directional coupler.
The directional coupler has a primary line and a coupled line. Due to the small overall insertion loss of the primary line a receiver signal can be coupled from an input port of the primary line to an output port of the primary line with hardly any losses (low-loss path). Due to a relatively low coupling factor, however, the local oscillator signal transmitted from an input port of the coupled line to the output port of the primary line is strongly attenuated (high-loss path).
The input port of the primary line is connected to the output of a receiver front end circuit and the output port of the primary line is connected to the mixer. The input port of the coupled line is connected to both a local oscillator and an input of a first PIN diode. An output of the first PIN diode is coupled to the exciter. An output port of the coupled line is connected to both an output of a second PIN diode and a terminating element allowing termination of the output port of the coupled line with the characteristic impedance of the coupled line.
When the two PIN diodes are switched on, the output port of the coupled line is shorted and the one-quarter wavelength coupled line has an infinite impedance at the input port of the coupled line. Consequently, the local oscillator signal is routed through the second PIN diode to the exciter. When the two PIN diodes are switched off, the output port of the coupled line is terminated in its characteristic impedance. The local oscillator signal can then be routed through the coupled line and a portion of it is thus transmitted to the output port of the primary line.
The R.F. local oscillator switch according to WO 88/00760 consists of two PIN diodes and a plurality of passive components. However, the plurality of PIN diodes and passive components limits the degree to which the R.F. local oscillator switch can be miniaturized and increases the overall cost of the switch.
The R.F. local oscillator switch, which is used in addition to the above described R.F. antenna switch, is part of a mixer stage allowing to combine two signals. The R.F. local oscillator switch is thus not suited as an R.F. antenna switch for routing either one of two antenna signals to a common port or for routing an antenna signal from the common port to either one of a high-loss port and a low-loss port.
A further R.F. antenna switch is known from WO 97/23929. This R.F. antenna switch is configured as a mechanical component and arranged within a housing of a coaxial accessory connector. A standard antenna is mounted in a top port of the coaxial accessory connector. A radial port in the coaxial accessory connector can be coupled to a further antenna which activates the R.F. switch to disengage from the standard antenna contact and to engage a contact in the radial port. In this way, the R.F. signal is conducted to the further antenna, rather than to the standard antenna. When the R.F. switch is not activated by the further antenna, the R.F. signal is carried through the coaxial accessory connector to the standard antenna.
There is a need for an R.F. antenna switch which has a simple construction and which allows a higher degree of integration. There is also a need for a preferred use of such an R.F. antenna switch and for an R.F. device incorporating such an R.F. antenna switch.
SUMMARY OF THE INVENTION
The present invention satisfies these needs by providing an R.F. antenna switch for coupling a common port to either a high-loss port or a low-loss port, the R.F. antenna switch having an unequal power splitter with at least the common port, the high-loss port and the low-loss port. The unequal power splitter further comprises a high-loss path coupled between the common port and the high-loss port and a low-loss path coupled between the common port and the low-loss port. A switching element of the R.F. antenna switch has an input coupled to the low-loss port and an output coupled to a first terminating element. The low-loss port is terminated with the characteristic impedance of the low-loss path when the switching element is switched on.
When the switching element is switched on, the low-loss port has a non-reflecting, i.e., absorbing characteristic. The impedance of the terminating element is, therefore, preferably chosen such that the total impedance of all components coupled to the low-loss port including the impedance of the terminating element equals the characteristic impedance of the low-loss path.
The R.F. antenna switch according to the invention can be realized with only one switching element and few passive components. This not only reduces the cost of the R.F. antenna switch but also allows a higher degree of integration and further miniaturization of the R.F. antenna switch.
Moreover, unequal power splitters comprising e.g. transmission line structures can be realized with ceramic multi-layer technology in an efficient way. Any additional components of the R.F. antenna switch like the switching element or terminating elements can remain discrete components which may be placed on top of the ceramic multi-layer substrate as already practised for state of the art transmitter/receiver-switch modules. Filter structures can advantageously be realized on the same ceramic multi-layer substrate as the R.F. antenna switch. This enables further integration and cost reduction.
The R.F. antenna switch according to the invention can advantageously be used in many technical fields and above all in all kinds of transmitting and receiving applications like positioning system receivers adapted to a standard taken from the group consisting of GPS, GLONASS, BAAS, etc or mobile phones adapted to a standard taken from the group consisting of GSM 900, GSM 1800, GSM 1900, AMPS, PDC, CDMA, WCDMA, DAMPS, etc.
The R.F. antenna switch according to the invention enables to couple either a low-loss port or a high-loss port to a common port. Thus, the R.F. antenna switch allows to couple either a signal applied to the low-loss port or a signal applied to the high-loss port to the common port or to couple a signal applied to the common port either to the low-low port or the high-loss port. Preferably, the R.F. antenna switch is switched by means of changing the impedances at the individual ports of the R.F. antenna switch. Therefore, In order to couple the signal via a specific port, this specific port can be terminated with a characteristic impedance. On the other hand, in order to block a signal from being transmitted via the specific port, the specific port can be terminated with an impedance mismatch. The impedance mismatch is e.g. created by simply switching off an el
Lee Benny
Telefonaktiebolaget LM Ericsson (publ)
LandOfFree
R.F. antenna switch for use with internal and external antennas does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with R.F. antenna switch for use with internal and external antennas, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and R.F. antenna switch for use with internal and external antennas will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3344359