Patent Application
20150044979
This disclosure relates to transmitters. This disclosure also relates to transmitters with a reduced counter-intermodulation component.
A transmitter or radio transmitter in electronics and telecommunications is an electronic device which with an antenna produces radio waves. The transmitter can generate a radio frequency alternating current, which can be applied to the antenna. When excited by the alternating current the antenna can radiate radio waves. The transmitter can be used in equipment that generates radio waves for communication purposes and radiolocation, such as radar and navigational transmitters.
The innovation may be better understood with reference to the falling drawings and description. In the figures, like reference numerals designate corresponding parts throughout the different views.
Radio transmitters can minimize undesired out-of-band transmission to avoid interfering with other radio equipment. Standards, such as the 3rd Generation Partnership Project Long Term Evolution (3GPP-LTE) standards, present increasingly strict requirements to minimize undesired out-of-band transmissions. One example of undesired out-of-band transmissions is the transmitting of unwanted signals in channels or bands neighboring the channel/band being used to transmit the intended signal. Transmissions in such neighboring channels may be caused by intermodulation in elements within the transmitting chain. Intermodulation can occur when nonlinearities in a given circuit element cause two input signals of different frequencies to be undesirably combined. Intermodulation can create additional signals at frequencies which are at the sum and/or difference of integer multiples of the input frequencies.
In accordance with the circuits and methods described herein, lower power consumption can be achieved by eliminating extra power needed to reduce a third-order counter intermodulation C-IM3 and/or by enabling a power amplifier (PA) to be biased into class-B.
User equipment 100 may be virtually any device that transmits and receives information, including as additional examples a driver assistance module in a vehicle, an emergency transponder, a pager, a satellite television receiver, a networked stereo receiver, a computer system, music player, or virtually any other device. The techniques discussed below may also be implemented in a base station or other network controller that communicates with the user equipment (UE).
The user equipment 100 can include among other things system components 112, system logic 114 and a user interface 118. System logic 114 can be part of the implementation of desired functionality in the UE 100. In that regard, the system logic 114 may include logic that facilitates, as examples, running applications; accepting user inputs; saving and retrieving application data; establishing, maintaining, and terminating cellular phone calls or data connections for, as one example, Internet connectivity; establishing, maintaining, and terminating wireless network connections, Bluetooth connections, or other connections; and displaying relevant information on the user interface 118. The user interface 118 may include a graphical user interface (GUI), touch sensitive display, voice, facial and gesture recognition inputs, buttons, switches, speakers and other user interface elements.
The system logic 114 can include memory 120, control instructions 122, control parameters 124 and operating parameters 130. The system components 112 may be implemented, for example, in a system on a chip (SoC), application specific integrated circuit (ASIC), or other circuitry. In the system components 112 a communication interface can include Radio Frequency (RF) transmit (Tx) and receive (Rx) circuitry 130 to handle transmission and reception of signals through one or more antennas 132.
As implementation examples, the system components 112 may include BCM4345, BCM4349 or BCM4343 wireless local area network (WLAN) chips or combo chips. These devices or other similar system solutions may be extended to provide the additional functionality described below. These integrated circuits, as well as other hardware and software implementation options for the user equipment 100, are available from Broadcom Corporation of Irvine Calif.
The transmitted and received signals may adhere to any of a diverse array of formats, protocols, modulations (e.g., QPSK, 16-QAM, 64-QAM, or 256-QAM), frequency channels, bit rates, and encodings. As one example, the system components 112 may support transmission and reception under multiple protocols. For example, WLAN, ANT, Bluetooth, and Bluetooth Low Energy (BLE) standards. Corresponding protocol stacks may be included in the memory 120. The techniques described below, however, are applicable to other communications technologies.
To combat counter-intermodulation with a reduced circuit area and/or increased efficiency over other solutions, an inductor/capacitor (LC) or other notch filter incorporated into transformer 250, e.g., balun, can be added at the output of the mixer 210 before the mixer output is sent to the PA 220, or other non-linear block of circuitry. When the upconverted 3rf 330 signal is inputted to a non-linear block, it can create distortion which degrades a quality of the rf signal 320. Therefore, the notch filter located in transformer 250 can be used to filter the third harmonic up-converted component 3rf 330 to reduce the distortion to the rf signal 320. Additionally or alternatively, other filters can be implemented, e.g. to filter 5rf 340, etc. The notch filter can be integrated inside an already existing mixer balun, e.g., any passive structure in the RF domain, to not consume any additional circuit area. By placing the notch filter inside the mixer balun, an integrated design can offer not only area savings but also accurate design modeling and capture of circuit performance factors.
As described in more detail below, in addition to the notch filter in transformer 250, a differential capacitor at the source of mixer cascode devices can filter out 3rf in the current domain. The additional area can be a single metal capacitor which is negligible compared to the rest of the circuit area. With these, the PA 220 can be biased in class-B and achieve a low C-IM3 and high efficiency.
A capacitor 460 shunts the cascode transistors 450, 452 and acts as a Gm/C filter to initially filter the 3rf signal 330, or other signal depending on a tuning of the filter. The size of the capacitor 460 is determined to be not large enough to filter the rf signal 330 but large enough to filter at least some of the 3lo signal 320. The outputs of the cascode transistors 450, 452 connect with a coupler 470, e.g., balun transformer 250. The coupler 470 can include inductors and a capacitor to couple the rf signal 320 with a differential output 475. A capacitor 480 and inductor 482 are integrated with the coupler 470 and the capacitor 480 and inductor 482 are connected in series between output lines 490, 492 of the differential output 475 of the coupler 470. The capacitor 480 and the inductor 482 can connect in parallel with the coupler 470, e.g., connect with the differential outputs of the balun transformer 250. The series capacitor 480 and inductor 482 are tuned to filter 3rf or other unwanted frequency. The series capacitor 480 and inductor 482 can create a short circuit at 310 between the differential output lines 490, 492, and an open circuit at the rf frequency. The output lines 490, 492 can connect with the PA 220.
The methods, devices, and logic described above may be implemented in many different ways in many different combinations of hardware, software or both hardware and software. For example, all or parts of the system may include circuitry in a controller, a microprocessor, or an application specific integrated circuit (ASIC), or may be implemented with discrete logic or components, or a combination of other types of analog or digital circuitry, combined on a single integrated circuit or distributed among multiple integrated circuits. All or part of the logic described above may be implemented as instructions for execution by a processor, controller, or other processing device and may be stored in a tangible or non-transitory machine-readable or computer-readable medium such as flash memory, random access memory (RAM) or read only memory (ROM), erasable programmable read only memory (EPROM) or other machine-readable medium such as a compact disc read only memory (CDROM), or magnetic or optical disk. Thus, a product, such as a computer program product, may include a storage medium and computer readable instructions stored on the medium, which when executed in an endpoint, computer system, or other device, cause the device to perform operations according to any of the description above.
The processing capability of the system may be distributed among multiple system components, such as among multiple processors and memories, optionally including multiple distributed processing systems. Parameters, databases, and other data structures may be separately stored and managed, may be incorporated into a single memory or database, may be logically and physically organized in many different ways, and may implemented in many ways, including data structures such as linked lists, hash tables, or implicit storage mechanisms. Programs may be parts (e.g., subroutines) of a single program, separate programs, distributed across several memories and processors, or implemented in many different ways, such as in a library, such as a shared library (e.g., a dynamic link library (DLL)). The DLL, for example, may store code that performs any of the system processing described above.
While various embodiments have been described, it can be apparent that many more embodiments and implementations are possible. Accordingly, the embodiments are not to be restricted.
This application claims priority to U.S. Provisional Application Ser. No. 61/864,163 , filed Aug. 9, 2013, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61864163 | Aug 2013 | US |
