WO2012117390A1

WO2012117390A1 - A transmit/receive switch

Info

Publication number: WO2012117390A1
Application number: PCT/IL2011/000196
Authority: WO
Inventors: Kobi Ben-Atar; Alex Mostov; Yaron Hasson
Original assignee: Dsp Group Ltd.
Priority date: 2011-02-28
Filing date: 2011-02-28
Publication date: 2012-09-07

Abstract

The subject matter discloses a method for reducing an insertion loss of an Rx switch, the method comprising intensifying a transmitted signal; intensifying a received signal; switching to a transmit mode and passing the transmitted signal from a power amplifier to an antenna and blocking the transmitted signal from passing through to a low-noise amplifier; switching to a receive mode and passing the received signal from the antenna to the low-noise amplifier and blocking the received signal from passing through the power amplifier; and operating the Rx switch in an active regime prior to the passing of the received signal from the antenna to the low-noise amplifier and prior to the blocking of the received signal from passing through the power amplifier; thereby reducing the insertion loss of the Rx switch.

Description

A TRANSMIT/RECEIVE SWITCH

BACKGROUND

The present disclosure relates to integrated circuits in general, and to Radio Frequency integrated circuits, in particular.

In electronics, an integrated circuit also known as IC, chip or microchip is a miniaturized electronic circuit consisting mainly of semiconductor devices, as well as passive components that have been manufactured in the surface of a thin substrate of semiconductor material. Integrated circuits are used in almost all-electronic equipments and have revolutionized the world of electronics.

Radio Frequency integrated circuits are integrated circuits, which are used for receiving and transmitting radio frequencies. Such integrated circuits may be used for the cordless telephone industry, for the cellular telephone industry and the like.

Complementary metal-oxide-semiconductor (CMOS) is a technology for constructing integrated circuits. In a fully integrated CMOS transmit/receive (T/R) switch which is typically used for the cellular telephones or for cordless telephones, the transceiver includes a power amplifier (PA) which is used for intensifying the signal that is to be transmitted and a low-noise amplifier (LNA) which is used for intensifying the received signal while minimizing the noise. The PA and the LNA are isolated from each other by the T/R switch. The T/R switch typically comprises a transmitter (Tx) switch and a receiver (Rx) switch both connected to an antenna. The T/R switch can be switched to transmit or to receive mode.

When the T/R switch is switched to receive mode, the Tx switch is disabled and, thus, blocks the received signals from passing through the PA. The Rx Switch is open and operates in the linear regime wherein there is a linear relation between the current and the voltage (V=IR).

When the TR switch is switched to transmit mode, the Rx switch is turned off causing high impedance to the PA. The high impedance is in order not to load the PA and in order not to lower the PA maximum output power. The Tx switch is opened and passes the signal from the PA to the Antenna while the Rx switch blocks the transmitted signal from passing through to the LNA. BRIEF SUMMARY

One exemplary embodiment of the disclosed subject matter is a method for reducing an insertion loss of an Rx switch, the method comprising: intensifying a transmitted signal; intensifying a received signal; switching to a transmit mode and passing the transmitted signal from a power amplifier to an antenna and blocking the transmitted signal from passing through to a low-noise amplifier; switching to a receive mode and passing the received signal from the antenna to the low-noise amplifier and blocking the received signal from passing through the power amplifier; and operating the Rx switch in an active regime prior to the passing of the received signal from the antenna to the low-noise amplifier and prior to the blocking of the received signal from passing through the power amplifier; thereby reducing the insertion loss of the Rx switch. The operating the Rx switch in an active regime further comprises changing a Vds such that Vgs is greater than a Vth and the Vds is greater than a Vgs minus the Vth . In some embodiments, the changing the Vds further comprises changing a voltage in a drain terminal or changing a voltage in the in a source terminal or a combination thereof. In some embodiments, the changing a voltage in a drain terminal or changing a voltage in the in a source terminal further comprising applying a direct current (DC) voltage through a resistor and a transistor respectively. The method' further comprising changing the Vgs. In some embodiments, the method changing the Vgs further comprises changing a voltage in a gate terminal or changing a voltage in the in a source terminal or a combination thereof.

Another exemplary embodiment of the disclosed subject matter is an apparatus for reducing an insertion loss of an Rx switch; the apparatus comprising a power amplifier for intensifying a transmitted signal; a low-noise amplifier (110) for intensifying a received signal; a Tx switch configures to block the received signal from passing through the power amplifier when the apparatus is in receive mode and to pass the transmitted signal from the power amplifier to an antenna when the apparatus is in transmit mode; and an Rx switch configured to block the transmitted signal from passing through to a low-noise amplifier when the apparatus is in the transmit mode and to pass the received signal from the antenna to the low-noise amplifier when the apparatus is in the receive mode; wherein the Rx switch is configured to work in an active regime, thereby reducing the insertion loss of the Rx switch . In some embodiments, the apparatus further comprising a transistor for applying a direct current (DC) bias voltage to a source terminal of the Rx switch. In some embodiments, the apparatus further comprising a inductor being used as an Radio Frequency (RF) chock for providing high resistance at an Radio Frequency (RF) and low resistance at a direct current (DC). 10. In some embodiments, the apparatus further comprising a inductor for applying a direct current (DC) bias voltage to a drain terminal of the Rx switch. In some embodiments, the apparatus further comprising a resistor for applying a direct current (DC) bias voltage to a gate terminal of the Rx switch

THE BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present disclosed subject matter will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which corresponding or like numerals or characters indicate corresponding or like components. Unless indicated otherwise, the drawings provide exemplary embodiments or aspects of the disclosure and do not limit the scope of the disclosure. In the drawings:

Fig. 1 shows a block diagram of a typical known in the art T/R switch;

Fig. 2 shows a block diagram of an active T/R switch, in accordance with some exemplary embodiments of the disclosed subject matter; and

Fig. 3 shows a method for operating the Rx switch 1 18 in active regime, in accordance with some exemplary embodiments of the disclosed subject matter.

DETAILED DESCRIPTION

The disclosed subject matter is described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the subject matter. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer- readable medium produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

[0001] One technical problem dealt with by the disclosed subject matter is to improve the Rx switch performance when using a T/R switch. As the signal passes through the Rx switch it exhibits insertion loss caused by the resistive nature of the Rx switch due to the linear regime. This insertion loss may range from 1.3dB to 3dB and may degrade the receiver performance. Degrading the receiver performance is proportional to the insertion loss value.

One technical solution is a T R switch comprising an Rx switch operated in the active regime. In such a solution the T/R switch is used as a common-gate amplifier with substantially 15dB of gain and 2.3dBb Noise Figure (NF). Referring now to Figure 1 showing a block diagram of a typical known in the art T/R switch. Front-end 100 comprises a transmit front end 120 and a receive front end 130. The transmit front end 120 and a receive front end 130 are connected to an antenna 112. The connection may be done through a matching network 1 1 1. The matching network 111 may be used for converting between impedances in order to avoid signal loss. The antenna is for receiving and for transmitting signals, such as Radio Frequency (RF) signals. The signals to be transmitted are transmitted through a PA 101 to the antenna 112. The received signals are received by the antenna 112 and are passed to an LNA 110.

The transmit front end 120 comprises the PA 101 connected to a resistor 103. The resistor 103 is connected to a Tx switch 102. The Tx switch 102 is connected to a resistor 104. The resistor 104 is connected to a capacitor 105. The capacitor 105 is connected to a matching network 1 1 1, which is connected to an antenna 112.

The PA 101 is for intensifying the signal that is to be transmitted. The resistors 103 and 104 are configured for avoiding leakage to the substrate (not shown) on which the front end 100 is placed and for applying direct current (DC) bias voltage to the Tx switch 102. The substrate may be a silicon substrate. The capacitor 105 is for blocking the Tx switch 102 DC bias from the Antenna 112 and from the Rx front end 130. The Tx switch 102 is configured for enabling the passing of the RF signal to the antenna 112 when the T/R switch 150 mode is switched to transmit mode and for avoiding the leakage of the received signals to the PA 101, when the T/R switch mode is received mode. The Tx switch 102 is typically a transistor.

The receive front end 130 comprises a capacitor 106 connected to a resistor 107. The resistor 107 is connected to an Rx switch 108. The Rx switch 108 is connected to a resistor 109. The resistor 109 is connected to an LNA 110. The receive front end 130 is connected to the antenna 1 12 by connecting the capacitor 106 to the matching network 1 11.

The LNA 110 is for intensifying the received signal while minimizing the noise. The resistors 107 and 109 are for avoiding leakage to the substrate (not shown) on which the front end 100 is placed and for applying DC bias voltage to the Rx switch 108. The capacitor 106 is for blocking the Rx switch 108 DC bias from the Antenna 1 12 and from the Tx front end 120. The Rx switch 108 is for enabling the passing of the received signals from the antenna 1 12 when the front end 100 mode is receive mode and for avoiding the leakage of the received signals to the LNA 1 10, when the T/R switch 150 mode is transmit mode. The Rx switch is typically a transistor.

Fig. 2 shows a block diagram of an active T/R switch, in accordance with some exemplary embodiments of the disclosed subject matter. Active T/R switch 250 comprises the Rx switch 108 operated in the active regime. Such an operation improves the Rx switch performance by reducing the signal noise that is generated as the signal passes through the Rx switch. According to some exemplary embodiments, the Rx switch 108 may be operated in the active regime by changing the voltage of the drain (D) terminal 119 and source (S) terminal 1 17 of the Rx switch 118 transistor. The method of operating the Rx switch 118 in active regime is explained in greater details in figure 3.

Operating the Rx switch 118 in active regime causes the Rx switch 118 to be saturated. When the Rx switch 118 is saturated, the current flowing through the transistor is constant with respect to Voltage between the drain (D) terminal 119 and source (S) terminal 117 and the transistor can be used as a transconductance amplifier. In some exemplary embodiments, the resistors 107 and 109 used in the prior art may be . replaced by a transistor, an inductor or a combination thereof. In the exemplary diagram a transistor 115 and an inductor, 1 16 are used for avoiding leakage to the substrate (not shown) on which the front end 200 is placed. In the exemplary diagram, the transistor 115 is used for applying the DC bias voltage to the source (S) terminal 1 17 of the Rx switch 108 with a minimal effect on the noise performance of the Rx switch 108. The inductor 116 is used as an RF-chock for providing a high resistance in the RF frequency and low resistance at DC frequency. The providing of the high resistance in the RF frequency and low resistance at DC frequency may improve the headroom of the transconductor Rx switch 108. The Rx front end 130 comprises a resistor 140 for changing the voltage in the gate terminal 118. All the other elements of figure 2 are similar to the elements of figure 1.

Figure 3 shows a method for operating the Rx switch 108 in the active regime, in accordance with some exemplary embodiments of the disclosed subject matter. Figure 3 shows the Rx switch transistor 108 having the drain (D) terminal 1 19, the gate (G) terminal 118 and the source (S) terminal 117. Figure 3 shows a Vds 301, which is the voltage between the drain terminal 119 and the source terminal 117 and Vgs 302, which is the voltage between the gate terminal 118 and the source terminal 117. The transistor 108 may operate in three main operating regimes. The operating regimes are defined by the voltages Vds and Vgs applied to the transistor 108. The voltage Vds 301 is the voltage between the drain terminal 1 19 and the source terminal 1 17 (Vd-Vs). The voltage Vgs 302 is the voltage between the gate terminal 1 18 and the source terminal 117(V g-Vs).

The first regime is a cutoff regime in which the transistor is disabled and, thus, no current flows from drain to source. Such a regime is generated when Vgs is less then Vth (Vgs<Vth). The Vth is derived from the technology and from the size of the transistor. When using silicon technology the Vth may be 0.5 volt.

The second regime is the linear regime in which the transistor acts like a resistor and thus the current flowing through the transistor from drain to source develops a voltage across the transistor terminals (Vds) with a direct proportion to its resistance. Such a regime is generated when Vgs is greater than Vth and Vds is less than Vgs minus Vth. (Vgs>Vth and Vds<Vgs-Vth). A typical Rx switch known in the art is configured to operate in the second regime.

The third regime is the active regime in which the transistor is saturated and the current flowing through the transistor is constant with respect to Vds. In such a regime, the transistor can be used as an transconductance amplifier. Such a regime is generated when Vgs is greater than Vth and Vds is greater than Vgs minus Vth (Vgs>Vth and Vds>Vgs-Vth).

The method for operating the Rx switch 118 in active regime comprises changing the Vds 301. Changing the Vds 301 may be done by changing the voltage in the drain terminal 119 or changing the voltage in the in the source terminal 117 or a combination thereof. Changing the voltage in the drain terminal 1 19 or changing the voltage in the source terminal 117 may be done by applying a DC voltage through the inductor 116 and the transistor 115 respectively.

In some exemplary embodiments, operating the Rx switch 108 in the active regime may comprise changing the Vgs 302 in addition to changing the Vds 301. Such a change may effect the transconductance or gain of the Rx switch 108. Changing the Vgs may be done by changing the voltage in the gate terminal 118 or changing the voltage in the source terminal 1 17 or a combination thereof. Changing the voltage in the gate terminal 118 and in the source terminal 117 may be done by applying a DC voltage through resistor 140 of figure 2 and transistor 115 of figure 2 respectively. The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of program code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

As will be appreciated by one skilled in the art, the disclosed subject matter may be embodied as a system, method or computer program product. Accordingly, the disclosed subject matter may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit," "module" or "system." Furthermore, the present invention may take the form of a computer program product embodied in any tangible medium of expression having computer-usable program code embodied in the medium.

Any combination of one or more computer usable or computer readable medium(s) may be utilized. The computer-usable or computer-readable medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CDROM), an optical storage device, a transmission media such as those supporting the Internet or an intranet, or a magnetic storage device. Note that the computer-usable or computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory. In the context of this document, a computer-usable or computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer- usable medium may include a propagated data signal with the computer-usable program code embodied therewith, either in baseband or as part of a carrier wave. The computer usable program code may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, and the like.

Computer program code for carrying out operations of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.

Claims

CLAIMS claimed is:

1. A method for reducing an insertion loss of an Rx switch, the method

comprising:

intensifying a transmitted signal;

intensifying a received signal;

switching to a transmit mode and passing the transmitted signal from a power amplifier to an antenna and blocking the transmitted signal from passing through to a low-noise amplifier;

switching to a receive mode and passing the received signal from the antenna to the low-noise amplifier and blocking the received signal from passing through the power amplifier; and

operating the Rx switch in an active regime prior to the passing of the received signal from the antenna to the low-noise amplifier and prior to the blocking of the received signal from passing through the power amplifier; thereby reducing the insertion loss of the Rx switch.

2. The method of claim 1 , wherein the operating the Rx switch in an active

regime further comprises changing a Vds such that Vgs is greater than a Vth and the Vds is greater than a Vgs minus the Vth .

3. The method of claim 2, wherein changing the Vds further comprises

changing a voltage in a drain terminal or changing a voltage in the in a source terminal or a combination thereof.

4. The method of claim 3, wherein changing a voltage in a drain terminal or changing a voltage in the in a source terminal further comprising applying a direct current (DC) voltage through a resistor and a transistor respectively.

5. The method of claim 2, further comprising changing the Vgs.

6. The method of claim 5, wherein changing the Vgs further comprises

changing a voltage in a gate terminal or changing a voltage in the in a source terminal or a combination thereof.

7. An apparatus for reducing an insertion loss of an Rx switch; the apparatus comprising:

a power amplifier (101) for intensifying a transmitted signal;

a low-noise amplifier (110) for intensifying a received signal; a Tx switch (102) configures to block the received signal from passing through the power amplifier when the apparatus is in receive mode and to pass the transmitted signal from the power amplifier to an antenna when the apparatus is in transmit mode; and

an Rx switch (108) configured to block the transmitted signal from passing through to a low-noise amplifier when the apparatus is in the transmit mode and to pass the received signal from the antenna to the low-noise amplifier when the apparatus is in the receive mode; wherein the Rx switch is configured to work in an active regime, thereby reducing the insertion loss of the Rx switch .

8. The apparatus of claim 7, further comprising a transistor (1 15) for applying a direct current (DC) bias voltage to a source terminal of the Rx switch.

9. The apparatus of claim 7, further comprising a inductor (116) being used as an Radio Frequency (RF) chock for providing high resistance at an Radio Frequency (RF) and low resistance at a direct current (DC).

10. The apparatus of claim 7, further comprising a inductor (1 16) for applying a direct current (DC) bias voltage to a drain terminal of the Rx switch

11. The apparatus of claim 7, further comprising a resistor (140) for applying a direct current (DC) bias voltage to a gate terminal of the Rx switch