Search

EP-3451530-B1 - TRANSFORMER OR INDUCTOR SHARING IN A RADIO FREQUENCY AMPLIFIER AND METHOD THEREFOR

EP3451530B1EP 3451530 B1EP3451530 B1EP 3451530B1EP-3451530-B1

Inventors

  • SUN, CHIH-HAO
  • HSIAO, PO-YUN
  • CHAO, CHIN-YEN
  • LEE, YI-BIN

Dates

Publication Date
20260513
Application Date
20180727

Claims (7)

  1. A radio frequency integrated circuit, RFIC, (308) comprising: a plurality of parallel radio frequency, RF, signal paths, wherein a first RF signal path of the plurality of parallel RF signal paths comprises at least one first RF amplifier (330, 430) and a second RF signal path of the plurality of parallel RF signal paths comprises at least one second RF amplifier (340, 440); and a shared inductor (315) or shared RF transformer (310) located between the first RF signal path and the second signal path; wherein the at least one first RF amplifier (330, 430) is coupled to a voltage supply (305) via a first switch (320) and the at least one second RF amplifier (340, 440) is coupled to the voltage supply (305) via a second switch (322), and wherein a signal applied to the first switch (320) and second switch (322) from a controller configures the second switch (322) as an open circuit and first switch (320) as a closed circuit such that the supply voltage is connected to the at least one second RF amplifier (340, 440) via the shared inductor (315) or shared RF transformer (310) and a high impedance is created at an output of the at least one second RF amplifier (340, 440) that isolates the output from an output of the at least one first RF amplifier (330, 430); wherein the at least one first RF amplifier (330, 430) and at least one second RF amplifier (340, 440) comprise multiple selectable RF amplifiers or multiple sets of selectable RF amplifiers located on either side of the shared inductor (315) or shared RF transformer (310) to support different frequency bands.
  2. The RFIC (308) of Claim 1 wherein the at least one first RF amplifier (330, 430) exhibits a first output parasitic capacitance and the at least one second RF amplifier (340, 440) exhibits a second output parasitic capacitance connected via the shared inductor (315) or shared RF transformer (310) and a closed first switch (320) causes the shared inductor (315) or shared RF transformer (310) to create a high impedance at the output of the at least one second RF amplifier (340, 440) and reduce an effect of the exhibited second output parasitic capacitance at an output of the at least one first RF amplifier (330, 430).
  3. The RFIC (308) of Claim 2 wherein a first selectable RF amplifier or set of selectable RF amplifiers from the multiple selectable RF amplifiers or multiple sets of selectable RF amplifiers is selectively connected to an internal portion of the shared inductor (315) or shared RF transformer (310), thereby adjusting an inductance value of the shared inductor (315) or shared RF transformer (310).
  4. The RFIC (308) of any preceding Claim wherein the at least one first RF amplifier (330, 430) and at least one second RF amplifier (340, 440) comprise at least one from a group of: low noise amplifiers in a receiver path of the RFIC (308), programmable gain amplifiers in a transmitter path of the RFIC, comprise multiple RF amplifiers.
  5. The RFIC (308) of Claim 4 wherein the at least one first RF amplifier (330, 430) and at least one second RF amplifier (340, 440) comprise multiple RF amplifiers that are located on slices, wherein sets of slices are separated by the shared inductor (315) or shared RF transformer (310).
  6. A communication unit (200) comprising the RFIC, the voltage supply (305); and the controller (214) of Claim 1.
  7. A method (600) for sharing an inductor or transformer by multiple RF amplifiers in a communication unit, the method comprising: locating (602) a shared inductor (315) or shared RF transformer (310) between a first RF signal path of a plurality of parallel RF signal paths, wherein the first RF signal path comprises at least one first RF amplifier (330, 430), and a second RF signal path comprising at least one second RF amplifier (340, 440); closing (604, 608) a first switch (320) to connect a supply voltage to the at least one first RF amplifier (330, 430) via the shared inductor (315) or shared RF transformer (310) creating a high impedance at an output of the at least one second RF amplifier (340, 440) that isolates the output from an output of the at least one first RF amplifier (330, 430); and opening (604, 608) a second switch (322) connecting the supply voltage to the at least one second RF amplifier (340, 440); wherein the at least one first RF amplifier (330, 430) and at least one second RF amplifier (340, 440) comprise multiple selectable RF amplifiers or multiple sets of selectable RF amplifiers located on either side of the shared inductor (315) or shared RF transformer (310) to support different frequency bands.

Description

Field of the Invention The field of this invention relates to a communication unit and an integrated circuit having a radio frequency circuit and a method for transformer or inductor sharing. In particular, the field of this invention relates to transformer or inductor sharing in a design of a high frequency and broadband low noise amplifier (LNA) or programmable-gain amplifier (PGA) where multiple parallel amplifiers are used that share the transformer or inductor. Background of the Invention A primary focus and application of the present invention is in the field of radio frequency (RF) amplifiers for transmitters and/or receivers capable of use in wireless telecommunication units. The third generation partnership project (3GPP™) is a mobile (wireless) communications collaboration between groups of telecommunications standards associations. One of the currently developed standards is the long term evolved (LTE™) standard. LTE™ is a standard for high-speed wireless communication for mobile devices and data terminals, based on the global system for mobile (GSM™) communications or Enhanced Data GSM Environment (EDGE) and universal mobile telecommunications standards (UMTS)/High Speed packet access (HSPA) technologies. These technologies increase the capacity and speed using different radio interfaces together with providing core network improvements. Continuing pressure on the limited spectrum available for radio communication systems is forcing the development of spectrally-efficient linear modulation schemes and mechanisms that can better utilise limited available communications bandwidths. Carrier aggregation is used in LTE-Advanced in order to increase the bandwidth, and thereby increase the communication bit-rate, where a maximum of five component carriers (of up to 20 MHz each) can be aggregated, hence providing a maximum aggregated bandwidth of 100 MHz. The easiest way to arrange aggregation is to use contiguous component carriers within the same operating frequency band (as defined for LTE™), so called intra-band contiguous carrier aggregation (ICA). For non-contiguous carrier aggregation (NCCA) cases, the bands are separated by one, or more, frequency gap(s). Inter-band non-contiguous carrier aggregation is a form of carrier aggregation that uses different frequency bands. It is particularly useful where there is fragmentation of frequency bands, some of which may be, say, only 10 MHz wide. For a subscriber unit (sometimes referred to as a mobile station or a user equipment (UE) in GSM or LTE™ terminology), a use of multiple transceivers within the single device is often required, with the usual impact on cost, performance and power. In addition to this there are also additional design complexities resulting from the need to reduce intermodulation and cross modulation from multiple (e.g. two) transceivers. In particular, in radio frequency designs that support wide operational bandwidth, or that support carrier aggregation across multiple supported carrier frequencies, multiple low noise amplifiers (LNAs) and/or programmable-gain amplifier (PGAs) may be used in parallel. As these LNAs or PGAs operate at high or very high radio frequencies, the signal paths from multiple amplifiers are typically combined using inductors or transformers. LNAs and PGAs are found in radio communication systems, as well as medical instruments and electronic equipment. A typical LNA or PGA may supply a power gain of 100 (i.e. 20 decibels (dB)), whilst decreasing a signal-to-noise ratio by less than a factor of two (i.e. exhibiting a 3 dB noise figure (NF)). Although LNAs are primarily concerned with weak signals that are just above the noise floor, they must also be designed to consider the presence of larger signals that may cause intermodulation distortion. Referring to FIG. 1, a known radio frequency (RF) amplifier circuit 100 is illustrated, where multiple RF amplifiers 130, 140 are connected in parallel. The outputs of each of the respective multiple RF amplifiers 130, 140 exhibits a parasitic capacitance 135, 145. The exhibited parasitic capacitances can result from overlapped area between gate and source/drain ports, as well as result from the diode (effect) between the ports. The output of each of the respective multiple RF amplifiers 130, 140 is connected to a shared inductor (L1) 115. In some instances, the shared inductor (L1) 115 may be a transformer input inductance of a RF transformer 110. The RF transformer is provided by a voltage supply 105 and includes a transformer output inductance 112. In some applications, for example lower frequency applications of, say, less than 1GHz, the parasitic capacitances 135, 145 have little or no effect on the performance of the RF amplifier circuit 100. Thus, this illustrated architecture is the simplest way for inductor or transformer sharing of multiple RF amplifiers 130, 140 that are connected in parallel. However, in some instances, for example at frequencies higher t