Increasing market penetration of wireless-communication or, simply, “wireless” devices, such as cellular telephones, radios, global-navigation-satellite-system (GNSS) receivers and the like, is generally premised on reducing costs associated with deployment of such devices while maintaining or improving performance and/or adding features thereto. One way to accomplish this task is to continually improve upon the components that perform electronic functions for wireless communications. For example, through continuous improvement of such components, newer generations of such wireless devices are routinely deployed in smaller packages with more processing power and lower power consumption, yet cost less than their earlier counterparts.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of ordinary skill in the art through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.
The present invention is directed to ultra low power, low noise switched capacitor radio frequency mixers, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims.
These and other advantages, aspects and novel features of the present invention, as well as details of illustrative aspects thereof, will be more fully understood from the following description and drawings.
Described herein below are embodiments and other examples of a method and apparatus for frequency mixing of a radio-frequency (RF) signal, such as a satellite or cellular signal, to obtain two or more signals having phases in synchronism with respective phases of the RF signal (e.g., in-phase and quadrature components of the RF signal). These embodiments and other examples may be particularly useful for deployment in a receiver that is usable in a Global-Navigation-Satellite System (GNSS).
Those skilled in the art will appreciate that the method and apparatus may be used with various other types of mobile or wireless systems and devices. In addition, these wireless devices may be “location-enabled,” and may be embodied as cellular telephones, pagers, laptop computers, personal digital assistants (PDAs), and like type wireless devices known in the art. Generally, location enabling the mobile devices may be facilitated by including within the devices a′capability of processing satellite signals of the GNSS (“GNSS satellite signals”).
In addition, the details of the method and apparatus provided herein allow one skilled in the art to recognize that, as compared to conventional methods and apparatuses, one or more embodiments and other examples of the apparatus and/or devices that implement the method provide improved gain without having to increase power for consumption or current input to the apparatus or devices; and provide increased signal-to-noise ratios (SNRs) of signals output from the apparatus and/or the devices.
Referring now to
The RF module 102 and the baseband module 104 are supported by support circuits 106 comprising oscillators, power supplies, clock circuits and the like. The CPU 108 performs control and computation functions by executing control software 112 that is stored in memory 110.
The GNSS receiver 100 may be implemented as a stand-alone receiver or as a component within a system or device. In one embodiment, the GNSS receiver 100 may be a component within a cellular telephone. In such an embodiment, the CPU 108, memory 110 and some support circuits 106 may be part of the cellular telephone. This configuration is known as a host-based configuration. Although the GNSS receiver 100 is described herein as one form of receiver that may benefit from the present invention, those skilled in the art will realize that other forms of receivers may likewise benefit from the present invention.
Referring now to
The GNSS portion comprises a GNSS band pass filter 205 and a GNSS Low Noise Amplifier 210. The Bluetooth portion comprises a Bluetooth Band Pass Filter 235 and Bluetooth Low Noise Amplifier 240. A capacitor switch mixer 215 mixes the outputs of a selectable one of the GNSS Low Noise Amplifier 210 and the Bluetooth Low Noise Amplifier 240 with a local oscillator generator 260
The IQ quadrature combiner 220 receives the outputs of the mixer 215 and provides a selection to a band pass filter 104. Alternatively, in certain embodiments, the I and Q channels could be carried all the way through the AD converter and then combined in the digital baseband section. The analog to digital converter (ADC) 240 digitizes the output of the band pass filter 104. The local oscillator generator 260 receives an output from a phase lock loop. The phase lock loop comprises an oscillator 245, a low pass filter 250, a phase detector 255, and a divider 265.
The mixer 215 mixes the incoming radio signal with a frequency signal having the desired frequency. A square wave signal of the desired frequency with a 50% duty cycle has the following equation:
The equation, in addition to frequency f, also includes frequency components 3f, 5f, 7f . . . . The additional frequency components 3f, 5f, 7f, comprise approximately 15% of the total energy of the signal.
Referring now to
The divider 310 divides the signal by three for GNSS applications, resulting in a 1600 MHz signal, or divides the signal by two for Bluetooth applications, resulting in a 2400 MHz signal. The divider 310 provides an in-phase (I) 1600/2400 MHz square wave signal with a 50% duty cycle. The divider 310 also provides the output to a digital delay 315. The digital delay also phase delays the output signal with a 30-degree offset, thereby resulting in an 90-degree out-of-phase signal (Q).
The I LO signal controls switch 420, establishing connection between a first node and a second node. Each node is connected to second switches 430. The second switches are controlled by the Q LO signal. As a result, the output of the switched capacitor mixer 215 is controlled by the combination of values of the I LO signal and the Q LO signals resulting in one of four different output states.
The four different states comprise the in-phase positive, I+, out-of-phase positive Q+, in-phase negative I−, and out-of-phase Q−. When both I LO and Q LO are high, the switch 420 outputs the in-phase portion I+ of the radio signal at the desired frequency. When the I LO is high and Q LO is low, the switch 420 outputs the out-of-phase portion Q+ of the radio signal at the desired frequency. When the I LO is low and Q LO is high, the switch 420 outputs the inverse of the in-phase component I− of the radio signal at the desired frequency. When both I LO and Q LO are low, the switch 420 outputs the inverse out-of-phase portion Q− of the radio signal at the desired frequency.
The capacitor mixer comprises two columns of four switches. The signals ILOp, QLOp, ILOn, and QLOn each control one of the switches in the column. The output of the switches controlled by ILOp and QLOp is I+ output. The output of the switches controlled by QLOn and ILOp is Q+ output. The output of the switches controlled by ILOn and QLOn is I− output. The output of the switches controlled by QLOp and ILOn is Q− output.
Connecting the switches in this configuration allows for a conventional LO to be used. The conventional LO is simple to realize, thus lowering the overall system power. By connecting one of the outputs of the differential LNA to the capacitor and the other to the mixer, the mixer can act as a balun. The mixer then has only one input, reducing the number of switches required and increasing the gain
Referring now to
Digital delay 315 can be used to substantially improve the equivalent waveforms. Also while the waveforms in
Referring now to
At 605, the CPU 108 provides a selection of one of Bluetooth or GNSS signal to receive. If the selection is GNSS, the local oscillator generator 260 divides by three (610), and the switch capacitor mixer 215 selects (615) the GNSS signal from the switch capacitor mixer 215. If the selection is Bluetooth, the local oscillator generator 260 divides by two (620) and the switch capacitor mixer 215 selects (625) the Bluetooth signal from the switch capacitor mixer 215.
At 630, the local oscillator 260 divides a 4800 MHz signal and provides an in-phase I LO and out-of-phase Q LO (635) to the switch capacitor mixer 215. Based on whether the in-phase I LO signal is high or low (640), the mixer 215 selects (645) the in-phase signal (I LO=high) of the radio I at the desired frequency or the out-of-phase signal Q of the radio at the desired frequency (I LO=low) (650).
Based on whether the out-of-phase Q LO signal is high or low, the mixer 215 provides (655) the signal selected at 645 or 650, or inverts the signal selected at 645 or 650 (655). At 660, the band pass filter 104 filters the signal provided at 655. The ADC 240 digitizes the output of the band pass filter 104 at 665.
The embodiments described herein may be implemented as a board level product, as a single chip, application specific integrated circuit (ASIC), or with varying levels of the system integrated with other portions of the system as separate components. Alternatively, certain aspects of the present invention are implemented as firmware. The degree of integration may primarily be determined by the speed and cost considerations.
While the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present invention.
Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the appended claims and equivalents thereof.
This application is a continuation in part of “Method and Apparatus for Frequency Mixing of Radio Frequency Signals”, U.S. application for patent Ser. No. 11/927,253 by Rodal, et al., filed Oct. 29, 2007, published as U.S. Pat. Pub. 2009/0111386, which is incorporated herein by reference.
Number | Name | Date | Kind |
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20040063416 | Kuenen et al. | Apr 2004 | A1 |
20070042744 | Ali et al. | Feb 2007 | A1 |
Number | Date | Country | |
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20120142301 A1 | Jun 2012 | US |
Number | Date | Country | |
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Parent | 11927253 | Oct 2007 | US |
Child | 13030209 | US |