Source: https://patents.google.com/patent/US8190116B2/en
Timestamp: 2019-07-24 10:23:15
Document Index: 529842376

Matched Legal Cases: ['art 1201', 'art 1201', 'art 1201', 'arts 1207', 'art 1207', 'art 1213', 'art 1219', 'art 1401', 'art 1407', 'art 1413', 'art 1419', 'art 4601', 'art 4607', 'art 4613', 'art 4619', 'art 1407', 'art 1407', 'art 1401', 'art 1407', 'art 1701', 'art 1407', 'art 1407', 'art 1407', 'art 1407', 'art 1407', 'art 1407']

US8190116B2 - Methods and systems for down-converting a signal using a complementary transistor structure - Google Patents
Methods and systems for down-converting a signal using a complementary transistor structure Download PDF
US8190116B2
US8190116B2 US13/040,570 US201113040570A US8190116B2 US 8190116 B2 US8190116 B2 US 8190116B2 US 201113040570 A US201113040570 A US 201113040570A US 8190116 B2 US8190116 B2 US 8190116B2
US13/040,570
US20110151821A1 (en
1999-04-16 Priority to US09/293,095 priority patent/US6580902B1/en
2002-12-30 Priority to US10/330,219 priority patent/US6836650B2/en
2004-12-27 Priority to US11/020,547 priority patent/US7194246B2/en
2006-02-16 Priority to US11/355,167 priority patent/US7376410B2/en
2008-03-31 Priority to US12/059,333 priority patent/US7937059B2/en
2011-03-04 Priority to US13/040,570 priority patent/US8190116B2/en
2011-03-04 Assigned to PARKERVISION, INC. reassignment PARKERVISION, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BULTMAN, MICHAEL J., COOK, ROBERT W., LOOKE, RICHARD C., MOSES, JR., CHARLEY D., SORRELLS, DAVID F.
2011-03-04 Application filed by ParkerVision Inc filed Critical ParkerVision Inc
2011-06-23 Publication of US20110151821A1 publication Critical patent/US20110151821A1/en
2011-07-20 First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=22642661&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=US8190116(B2) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
2012-05-29 Publication of US8190116B2 publication Critical patent/US8190116B2/en
2014-05-02 US case 6:14-cv-00687 filed litigation https://portal.unifiedpatents.com/litigation/Florida%20Middle%20District%20Court/case/6%3A14-cv-00687 Source: District Court Jurisdiction: Florida Middle District Court "Unified Patents Litigation Data" by Unified Patents is licensed under a Creative Commons Attribution 4.0 International License.
2015-07-31 Priority claimed from US14/815,133 external-priority patent/US9325556B2/en
This patent application is a continuation of U.S. application “Methods and Systems for Down-Converting a Signal Using a Complementary Transistor Structure,” Ser. No. 12/059,333, filed Mar. 31, 2008 now U.S. Pat. No. 7,937,059, now allowed, which is a continuation application of U.S. application “Methods and Systems for Down-Converting a Signal Using a Complementary Transistor Structure,” Ser. No. 11/355,167, filed Feb. 16, 2006, (now U.S. Pat. No. 7,376,410), which is a divisional of U.S. application “Methods and Systems for Down-Converting Electromagnetic Signals, and Applications Thereof,” Ser. No. 11/020,547, filed Dec. 27, 2004 (now U.S. Pat. No. 7,194,246), which is a continuation of U.S. application “Methods and Systems for Down-Converting Electromagnetic Signals, and Applications Thereof,” Ser. No. 10/330,219, filed Dec. 30, 2002 (now U.S. Pat. No. 6,836,650), which is a continuation of U.S. application “Frequency Translation Using Optimized Switch Structures,” Ser. No. 09/293,095, filed Apr. 16, 1999 (now U.S. Pat. No. 6,580,902), which is a continuation-in-part application of U.S. application “Method and System for Down-Converting Electromagnetic Signals,” Ser. No. 09/176,022, filed Oct. 21, 1998 (now U.S. Pat. No. 6,061,551), each of which is herein incorporated by reference in its entirety.
“Method and System for Frequency Up-Conversion,” Ser. No. 09/176,154, filed Oct. 21, 1998 (now U.S. Pat. No. 6,091,940).
“Method and System for Ensuring Reception of a Communications Signal,” Ser. No. 09/176,415, filed Oct. 21, 1998 (now U.S. Pat. No. 6,061,555).
U.S. application “Integrated Frequency Translation and Selectivity,” Ser. No. 09/175,966, filed Oct. 21, 1998 (now U.S. Pat. No. 6,049,706).
“Universal Frequency Translation, and Applications of Same,” Ser. No. 09/176,027, filed Oct. 21, 1998 (now abandoned).
“Method and System for Frequency Up-Conversion Having Optimized Switch Structures,” Ser. No. 09/293,097, filed Apr. 16, 1999.
Briefly stated, the present invention is directed to methods, systems, and apparatuses for down-converting an electromagnetic (EM) signal by aliasing the EM signal, and applications thereof. Generally, the invention operates by receiving an EM signal. The invention also receives an aliasing signal having an aliasing rate. The invention aliases the EM signal according to the aliasing signal to down-convert the EM signal. The term aliasing, as used herein and as covered by the invention, refers to both down-converting an EM signal by under-sampling the EM signal at an aliasing rate, and down-converting an EM signal by transferring energy from the EM signal at the aliasing rate.
FIG. 31 illustrates a structural block diagram of an under-sampling signal optimizer according to embodiments of the present invention;
FIG. 42 illustrates a structural block diagram of an inverted sample and hold module according to an embodiment of the present invention;
FIGS. 43A and 43B illustrate example waveforms present in the circuit of FIG. 31;
FIG. 71 illustrates an example pulse generator;
FIGS. 72A and 72B illustrate example waveforms related to the pulse generator of FIG. 71;
FIG. 92 shows a schematic of the circuit in FIG. 86 connected to an FSK source that alternates between 913 and 917 M at a baud rate of 500 Kbaud according to an embodiment of the present invention;
FIG. 98F illustrates a timing diagram of an example energy transfer module including pulses having apertures that are controlled in real time, according to an embodiment of the invention;
FIGS. 132A-132D illustrate example signal diagrams associated with the amplitude and pulse width modulated transmitter according to embodiments of the present invention;
FIG. 133 illustrates an example diagram associated with the amplitude and pulse width modulated transmitter according to embodiments of the present invention;
FIG. 134 illustrates and example diagram associated with the amplitude and pulse width modulated transmitter according to embodiments of the present invention;
FIGS. 136A-136G illustrate example signal diagrams associated with a waveform generator according to embodiments of the present invention;
FIGS. 144 and 145 illustrate differential receivers in accord with embodiments of the present invention; and
FIGS. 146 and 147 illustrate time and frequency domains for a narrow bandwidth/constant carrier signal in accord with an embodiment of the present invention.
2.2.1 Down-Converting to an Intermediate Frequency
(IF) Signal
2.3.1 Down-Converting to an Intermediate Frequency
3. Benefits of the Invention Using an Example Conventional
Receiver for Comparison
1. Down-Converting an EM Carrier Signal to an EM Intermediate
Signal by Under-Sampling the EM Carrier Signal at the Aliasing
1.2.1 First Example Embodiment: Amplitude
1.2.2 Second Example Embodiment: Frequency
2. Directly Down-Converting an EM Signal to a Baseband Signal
(Direct-to-Data)
2.2.1 First Example Embodiment: Amplitude
3.2.1 First Example Embodiment: Down-Converting an
FM Signal to a PM Signal
3.2.2 Second Example Embodiment: Down-Converting
an FM Signal to an AM Signal
4.1 The Under-Sampling System as a Sample and Hold
4.1.1 The Sample and Hold System as a Switch Module
and a Holding Module
4.1.2 The Sample and Hold System as Break-Before-
4.2 The Under-Sampling System as an Inverted Sample and
5.1 Doubling the Aliasing Rate (FAR) of the Under-Sampling
III. Down-Converting by Transferring Energy
1. Energy Transfer Compared to Under-Sampling
1.1 Review of Under-Sampling
1.1.1 Effects of Lowering the Impedance of the Load
1.1.2 Effects of Increasing the Value of the Holding
1.2 Introduction to Energy Transfer
2. Down-Converting an EM Signal to an IF EM Signal by
Transferring Energy from the EM Signal at an Aliasing Rate
2.2.2 Second Example Embodiment: Frequency
2.2.2.1.1 Analog FM Carrier Signal
2.2.2.1.2 Digital FM Carrier Signal
2.2.3 Third Example Embodiment: Phase Modulation
2.2.3.1 Operational Description
2.2.3.1.1 Analog PM Carrier Signal
2.2.3.1.2 Digital PM Carrier Signal
2.2.3.2 Structural Description
2.2.4 Other Embodiments
3. Directly Down-Converting an EM Signal to an Demodulated
Baseband Signal by Transferring Energy from the EM Signal
3.2.1 First Example Embodiment: Amplitude
3.2.1.1.1 Analog AM Carrier Signal
3.2.1.1.2 Digital AM Carrier Signal
3.2.2 Second Example Embodiment: Phase Modulation
3.2.2.1.1 Analog PM Carrier Signal
3.2.2.1.2 Digital PM Carrier Signal
3.2.3 Other Embodiments
4. Modulation Conversion
4.1 High Level Description
4.1.1 Operational Description
4.1.2 Structural Description
4.2 Example Embodiments
4.2.1 First Example Embodiment: Down-Converting an
4.2.1.1 Operational Description
4.2.1.2 Structural Description
4.2.2 Second Example Embodiment: Down-Converting
4.2.2.1 Operational Description
4.2.2.2 Structural Description
4.2.3 Other Example Embodiments
4.3 Implementation Examples
5.1 The Energy Transfer System as a Gated Transfer System
5.1.1 The Gated Transfer System as a Switch Module
and a Storage Module
5.1.2 The Gated Transfer System as Break-Before-Make
5.1.3 Example Implementations of the Switch Module
5.1.4 Example Implementations of the Storage Module
5.1.5 Optional Energy Transfer Signal Module
5.2 The Energy Transfer System as an Inverted Gated
5.2.1 The Inverted Gated Transfer System as a Switch
Module and a Storage Module
5.3 Rail to Rail Operation for Improved Dynamic Range
5.3.2 Complementary UFT Structure for Improved
5.3.3 Biased Configurations
5.3.4 Simulation Examples
5.4 Optimized Switch Structures
5.4.1 Splitter in CMOS
5.4.2 I/Q Circuit
5.5 Example I and Q Implementations
5.5.1 Switches of Different Sizes
5.5.2 Reducing Overall Switch Area
5.5.3 Charge Injection Cancellation
5.5.4 Overlapped Capacitance
5.6 Other Implementations
6. Optional Optimizations of Energy Transfer at an Aliasing Rate
6.1 Doubling the Aliasing Rate (FAR) of the Energy Transfer
6.2 Differential Implementations
6.2.1 An Example Illustrating Energy Transfer
6.2.1.1 Differential Input-to-Differential Output
6.2.1.2 Single Input-to-Differential Output
6.2.1.3 Differential Input-to-Single Output
6.2.2 Specific Alternative Embodiments
6.2.3 Specific Examples of Optimizations and
Configurations for Inverted and Non-Inverted
Differential Designs
6.3 Smoothing the Down-Converted Signal
6.4 Impedance Matching
6.5 Tanks and Resonant Structures
6.6 Charge and Power Transfer Concepts
6.7 Optimizing and Adjusting the Non-Negligible Aperture
6.7.1 Varying Input and Output Impedances
6.7.2 Real Time Aperture Control
6.8 Adding a Bypass Network
6.9 Modifying the Energy Transfer Signal Utilizing Feedback
6.10 Other Implementations
7. Example Energy Transfer Downconverters
For illustrative purposes, the operation of the invention is often represented by flowcharts, such as flowchart 1201 in FIG. 12A. It should be understood, however, that the use of flowcharts is for illustrative purposes only, and is not limiting. For example, the invention is not limited to the operational embodiment(s) represented by the flowcharts. Instead, alternative operational embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein. Also, the use of flowcharts should not be interpreted as limiting the invention to discrete or digital operation. In practice, as will be appreciated by persons skilled in the relevant art(s) based on the herein discussion, the invention can be achieved via discrete or continuous operation, or a combination thereof. Further, the flow of control represented by the flowcharts is provided for illustrative purposes only. As will be appreciated by persons skilled in the relevant art(s), other operational control flows are within the scope and spirit of the present invention. Also, the ordering of steps may differ in various embodiments.
Various terms used in this application are generally described in this section. The description in this section is provided for illustrative and convenience purposes only, and is not limiting. The meaning of these terms will be apparent to persons skilled in the relevant art(s) based on the entirety of the teachings provided herein. These terms may be discussed throughout the specification with additional detail.
The term modulated carrier signal, when used herein, refers to a carrier signal that is modulated by a baseband signal.
The term unmodulated carrier signal, when used herein, refers to a signal having an amplitude that oscillates at a substantially uniform frequency and phase.
The term baseband signal, when used herein, refers to an information signal including, but not limited to, analog information signals, digital information signals and direct current (DC) information signals.
The term carrier signal, when used herein, and unless otherwise specified when used herein, refers to modulated carrier signals and unmodulated carrier signals.
The term electromagnetic (EM) signal, when used herein, refers to a signal in the EM spectrum. EM spectrum includes all frequencies greater than zero hertz. EM signals generally include waves characterized by variations in electric and magnetic fields. Such waves may be propagated in any medium, both natural and manmade, including but not limited to air, space, wire, cable, liquid, waveguide, micro-strip, strip-line, optical fiber, etc. Unless stated otherwise, all signals discussed herein are EM signals, even when not explicitly designated as such.
The term intermediate frequency (IF) signal, when used herein, refers to an EM signal that is substantially similar to another EM signal except that the IF signal has a lower frequency than the other signal. An IF signal frequency can be any frequency above zero HZ. Unless otherwise stated, the terms lower frequency, intermediate frequency, intermediate and IF are used interchangeably herein.
The term analog signal, when used herein, refers to a signal that is constant or continuously variable, as contrasted to a signal that changes between discrete states.
The term baseband, when used herein, refers to a frequency band occupied by any generic information signal desired for transmission and/or reception.
The term baseband signal, when used herein, refers to any generic information signal desired for transmission and/or reception.
The term carrier frequency, when used herein, refers to the frequency of a carrier signal. Typically, it is the center frequency of a transmission signal that is generally modulated.
The term carrier signal, when used herein, refers to an EM wave having at least one characteristic that may be varied by modulation, that is capable of carrying information via modulation.
The term demodulated baseband signal, when used herein, refers to a signal that results from processing a modulated signal. In some cases, for example, the demodulated baseband signal results from demodulating an intermediate frequency (IF) modulated signal, which results from down converting a modulated carrier signal. In another case, a signal that results from a combined downconversion and demodulation step.
The term digital signal, when used herein, refers to a signal that changes between discrete states, as contrasted to a signal that is continuous. For example, the voltage of a digital signal may shift between discrete levels.
The term electromagnetic (EM) spectrum, when used herein, refers to a spectrum comprising waves characterized by variations in electric and magnetic fields. Such waves may be propagated in any communication medium, both natural and manmade, including but not limited to air, space, wire, cable, liquid, waveguide, microstrip, stripline, optical fiber, etc. The EM spectrum includes all frequencies greater than zero hertz.
The term electromagnetic (EM) signal, when used herein, refers to a signal in the EM spectrum. Also generally called an EM wave. Unless stated otherwise, all signals discussed herein are EM signals, even when not explicitly designated as such.
The term modulating baseband signal, when used herein, refers to any generic information signal that is used to modulate an oscillating signal, or carrier signal.
It is often beneficial to propagate electromagnetic (EM) signals at higher frequencies. This includes baseband signals, such as digital data information signals and analog information signals. A baseband signal can be up-converted to a higher frequency EM signal by using the baseband signal to modulate a higher frequency carrier signal, FC. When used in this manner, such a baseband signal is herein called a modulating baseband signal FMB.
Modulation imparts changes to the carrier signal FC that represent information in the modulating baseband signal FMB. The changes can be in the form of amplitude changes, frequency changes, phase changes, etc., or any combination thereof. The resultant signal is referred to herein as a modulated carrier signal FMC. The modulated carrier signal FMC includes the carrier signal FC modulated by the modulating baseband signal, FMB, as in:
FMB combined with FC→FMC
The modulated carrier signal FMC oscillates at, or near the frequency of the carrier signal FC and can thus be efficiently propagated.
FIG. 1 illustrates an example modulator 110, wherein the carrier signal FC is modulated by the modulating baseband signal FMB, thereby generating the modulated carrier signal FMC.
Modulating baseband signal FMB can be an analog baseband signal, a digital baseband signal, or a combination thereof.
FIG. 2 illustrates the modulating baseband signal FMB as an exemplary analog modulating baseband signal 210. The exemplary analog modulating baseband signal 210 can represent any type of analog information including, but not limited to, voice/speech data, music data, video data, etc. The amplitude of analog modulating baseband signal 210 varies in time.
Digital information includes a plurality of discrete states. For ease of explanation, digital information signals are discussed below as having two discrete states. But the invention is not limited to this embodiment.
FIG. 3 illustrates the modulating baseband signal FMB as an exemplary digital modulating baseband signal 310. The digital modulating baseband signal 310 can represent any type of digital data including, but not limited to, digital computer information and digitized analog information. The digital modulating baseband signal 310 includes a first state 312 and a second state 314. In an embodiment, first state 312 represents binary state 0 and second state 314 represents binary state 1. Alternatively, first state 312 represents binary state 1 and second state 314 represents binary state 0. Throughout the remainder of this disclosure, the former convention is followed, whereby first state 312 represents binary state zero and second state 314 represents binary state one. But the invention is not limited to this embodiment. First state 312 is thus referred to herein as a low state and second state 314 is referred to herein as a high state.
Digital modulating baseband signal 310 can change between first state 312 and second state 314 at a data rate, or baud rate, measured as bits per second.
Carrier signal FC is modulated by the modulating baseband signal FMB by any modulation technique, including, but not limited to, amplitude modulation (AM), frequency modulation (FM), phase modulation (PM), etc., or any combination thereof. Examples are provided below for amplitude modulating, frequency modulating, and phase modulating the analog modulating baseband signal 210 and the digital modulating baseband signal 310, on the carrier signal FC. The examples are used to assist in the description of the invention. The invention is not limited to, or by, the examples.
FIG. 4 illustrates the carrier signal FC as a carrier signal 410. In the example of FIG. 4, the carrier signal 410 is illustrated as a 900 MHZ carrier signal. Alternatively, the carrier signal 410 can be any other frequency. Example modulation schemes are provided below, using the examples signals from FIGS. 2, 3 and 4.
In amplitude modulation (AM), the amplitude of the modulated carrier signal FMC is a function of the amplitude of the modulating baseband signal FMB. FIGS. 5A-5C illustrate example timing diagrams for amplitude modulating the carrier signal 410 with the analog modulating baseband signal 210. FIGS. 6A-6C illustrate example timing diagrams for amplitude modulating the carrier signal 410 with the digital modulating baseband signal 310.
FIG. 5A illustrates the analog modulating baseband signal 210. FIG. 5B illustrates the carrier signal 410. FIG. 5C illustrates an analog AM carrier signal 516, which is generated when the carrier signal 410 is amplitude modulated using the analog modulating baseband signal 210. As used herein, the term “analog AM carrier signal” is used to indicate that the modulating baseband signal is an analog signal.
The analog AM carrier signal 516 oscillates at the frequency of carrier signal 410. The amplitude of the analog AM carrier signal 516 tracks the amplitude of analog modulating baseband signal 210, illustrating that the information contained in the analog modulating baseband signal 210 is retained in the analog AM carrier signal 516.
FIG. 6A illustrates the digital modulating baseband signal 310. FIG. 6B illustrates the carrier signal 410. FIG. 6C illustrates a digital AM carrier signal 616, which is generated when the carrier signal 410 is amplitude modulated using the digital modulating baseband signal 310. As used herein, the term “digital AM carrier signal” is used to indicate that the modulating baseband signal is a digital signal.
The digital AM carrier signal 616 oscillates at the frequency of carrier signal 410. The amplitude of the digital AM carrier signal 616 tracks the amplitude of digital modulating baseband signal 310, illustrating that the information contained in the digital modulating baseband signal 310 is retained in the digital AM signal 616. As the digital modulating baseband signal 310 changes states, the digital AM signal 616 shifts amplitudes. Digital amplitude modulation is often referred to as amplitude shift keying (ASK), and the two terms are used interchangeably throughout the specification.
In frequency modulation (FM), the frequency of the modulated carrier signal FMC varies as a function of the amplitude of the modulating baseband signal FMB. FIGS. 7A-7C illustrate example timing diagrams for frequency modulating the carrier signal 410 with the analog modulating baseband signal 210. FIGS. 8A-8C illustrate example timing diagrams for frequency modulating the carrier signal 410 with the digital modulating baseband signal 310.
FIG. 7A illustrates the analog modulating baseband signal 210. FIG. 7B illustrates the carrier signal 410. FIG. 7C illustrates an analog FM carrier signal 716, which is generated when the carrier signal 410 is frequency modulated using the analog modulating baseband signal 210. As used herein, the term “analog FM carrier signal” is used to indicate that the modulating baseband signal is an analog signal.
The frequency of the analog FM carrier signal 716 varies as a function of amplitude changes on the analog baseband signal 210. In the illustrated example, the frequency of the analog FM carrier signal 716 varies in proportion to the amplitude of the analog modulating baseband signal 210. Thus, at time t1, the amplitude of the analog baseband signal 210 and the frequency of the analog FM carrier signal 716 are at maximums. At time t3, the amplitude of the analog baseband signal 210 and the frequency of the analog FM carrier signal 716 are at minimums.
The frequency of the analog FM carrier signal 716 is typically centered around the frequency of the carrier signal 410. Thus, at time t2, for example, when the amplitude of the analog baseband signal 210 is at a mid-point, illustrated here as zero volts, the frequency of the analog FM carrier signal 716 is substantially the same as the frequency of the carrier signal 410.
FIG. 8A illustrates the digital modulating baseband signal 310. FIG. 8B illustrates the carrier signal 410. FIG. 8C illustrates a digital FM carrier signal 816, which is generated when the carrier signal 410 is frequency modulated using the digital baseband signal 310. As used herein, the term “digital FM carrier signal” is used to indicate that the modulating baseband signal is a digital signal.
The frequency of the digital FM carrier signal 816 varies as a function of amplitude changes on the digital modulating baseband signal 310. In the illustrated example, the frequency of the digital FM carrier signal 816 varies in proportion to the amplitude of the digital modulating baseband signal 310. Thus, between times t0 and t1, and between times t2 and t4, when the amplitude of the digital baseband signal 310 is at the higher amplitude second state, the frequency of the digital FM carrier signal 816 is at a maximum. Between times t1 and t2, when the amplitude of the digital baseband signal 310 is at the lower amplitude first state, the frequency of the digital FM carrier signal 816 is at a minimum. Digital frequency modulation is often referred to as frequency shift keying (FSK), and the terms are used interchangeably throughout the specification.
Typically, the frequency of the digital FM carrier signal 816 is centered about the frequency of the carrier signal 410, and the maximum and minimum frequencies are equally offset from the center frequency. Other variations can be employed but, for ease of illustration, this convention will be followed herein.
In phase modulation (PM), the phase of the modulated carrier signal FMC varies as a function of the amplitude of the modulating baseband signal FMB. FIGS. 9A-9C illustrate example timing diagrams for phase modulating the carrier signal 410 with the analog modulating baseband signal 210. FIGS. 10A-10C illustrate example timing diagrams for phase modulating the carrier signal 410 with the digital modulating baseband signal 310.
FIG. 9A illustrates the analog modulating baseband signal 210. FIG. 9B illustrates the carrier signal 410. FIG. 9C illustrates an analog PM carrier signal 916, which is generated by phase modulating the carrier signal 410 with the analog baseband signal 210. As used herein, the term “analog PM carrier signal” is used to indicate that the modulating baseband signal is an analog signal.
Generally, the frequency of the analog PM carrier signal 916 is substantially the same as the frequency of carrier signal 410. But the phase of the analog PM carrier signal 916 varies with amplitude changes on the analog modulating baseband signal 210. For relative comparison, the carrier signal 410 is illustrated in FIG. 9C by a dashed line.
The phase of the analog PM carrier signal 916 varies as a function of amplitude changes of the analog baseband signal 210. In the illustrated example, the phase of the analog PM signal 916 lags by a varying amount as determined by the amplitude of the baseband signal 210. For example, at time t1, when the amplitude of the analog baseband signal 210 is at a maximum, the analog PM carrier signal 916 is in phase with the carrier signal 410. Between times t1 and t3, when the amplitude of the analog baseband signal 210 decreases to a minimum amplitude, the phase of the analog PM carrier signal 916 lags the phase of the carrier signal 410, until it reaches a maximum out of phase value at time t3. In the illustrated example, the phase change is illustrated as approximately 180 degrees. Any suitable amount of phase change, varied in any manner that is a function of the baseband signal, can be utilized.
FIG. 10A illustrates the digital modulating baseband signal 310. FIG. 10B illustrates the carrier signal 410. FIG. 10C illustrates a digital PM carrier signal 1016, which is generated by phase modulating the carrier signal 410 with the digital baseband signal 310. As used herein, the term “digital PM carrier signal” is used to indicate that the modulating baseband signal is a digital signal.
The frequency of the digital PM carrier signal 1016 is substantially the same as the frequency of carrier signal 410. The phase of the digital PM carrier signal 1016 varies as a function of amplitude changes on the digital baseband signal 310. In the illustrated example, when the digital baseband signal 310 is at the first state 312, the digital PM carrier signal 1016 is out of phase with the carrier signal 410. When the digital baseband signal 310 is at the second state 314, the digital PM carrier signal 1016 is in-phase with the carrier signal 410. Thus, between times t1 and t2, when the amplitude of the digital baseband signal 310 is at the first state 312, the digital PM carrier signal 1016 is out of phase with the carrier signal 410. Between times t0 and t1, and between times t2 and t4, when the amplitude of the digital baseband signal 310 is at the second state 314, the digital PM carrier signal 1016 is in phase with the carrier signal 410.
In the illustrated example, the out of phase value between times t1 and t3 is illustrated as approximately 180 degrees out of phase. Any suitable amount of phase change, varied in any manner that is a function of the baseband signal, can be utilized. Digital phase modulation is often referred to as phase shift keying (PSK), and the terms are used interchangeably throughout the specification.
When the modulated carrier signal FMC is received, it can be demodulated to extract the modulating baseband signal FMB. Because of the typically high frequency of modulated carrier signal FMC, however, it is generally impractical to demodulate the baseband signal FM directly from the modulated carrier signal FMC. Instead, the modulated carrier signal FMC must be down-converted to a lower frequency signal that contains the original modulating baseband signal.
When a modulated carrier signal is down-converted to a lower frequency signal, the lower frequency signal is referred to herein as an intermediate frequency (IF) signal FIF. The IF signal FIF oscillates at any frequency, or frequency band, below the frequency of the modulated carrier frequency FMC. Down-conversion of FMC to FIF is illustrated as:
FMC→FIF
After FMC is down-converted to the IF modulated carrier signal FIF. FIF can be demodulated to a baseband signal FDMB, as illustrated by:
FIF→FDMB
FDMB is intended to be substantially similar to the modulating baseband signal FMB, illustrating that the modulating baseband signal FMB can be substantially recovered.
It will be emphasized throughout the disclosure that the present invention can be implemented with any type of EM signal, including, but not limited to, modulated carrier signals and unmodulated carrier signals. The above examples of modulated carrier signals are provided for illustrative purposes only. Many variations to the examples are possible. For example, a carrier signal can be modulated with a plurality of the modulation types described above. A carrier signal can also be modulated with a plurality of baseband signals, including analog baseband signals, digital baseband signals, and combinations of both analog and digital baseband signals.
Conventional signal processing techniques follow the Nyquist sampling theorem, which states that, in order to faithfully reproduce a sampled signal, the signal must be sampled at a rate that is greater than twice the frequency of the signal being sampled. When a signal is sampled at less than or equal to twice the frequency of the signal, the signal is said to be under-sampled, or aliased. Conventional signal processing thus teaches away from under-sampling and aliasing, in order to faithfully reproduce a sampled signal.
Contrary to conventional wisdom, the present invention is a method and system for down-converting an electromagnetic (EM) signal by aliasing the EM signal. Aliasing is represented generally in FIG. 45A as 4502.
By taking a carrier and aliasing it at an aliasing rate, the invention can down-convert that carrier to lower frequencies. One aspect that can be exploited by this invention is realizing that the carrier is not the item of interest, the lower baseband signal is of interest to reproduce sufficiently. This baseband signal's frequency content, even though its carrier may be aliased, does satisfy the Nyquist criteria and as a result, the baseband information can be sufficiently reproduced.
FIG. 12A depicts a flowchart 1201 that illustrates a method for aliasing an EM signal to generate a down-converted signal. The process begins at step 1202, which includes receiving the EM signal. Step 1204 includes receiving an aliasing signal having an aliasing rate. Step 1206 includes aliasing the EM signal to down-convert the EM signal. The term aliasing, as used herein, refers to both down-converting an EM signal by under-sampling the EM signal at an aliasing rate and to down-converting an EM signal by transferring energy from the EM signal at the aliasing rate. These concepts are described below.
FIG. 13 illustrates a block diagram of a generic aliasing system 1302, which includes an aliasing module 1306. In an embodiment, the aliasing system 1302 operates in accordance with the flowchart 1201. For example, in step 1202, the aliasing module 1306 receives an EM signal 1304. In step 1204, the aliasing module 1306 receives an aliasing signal 1310. In step 1206, the aliasing module 1306 down-converts the EM signal 1304 to a down-converted signal 1308. The generic aliasing system 1302 can also be used to implement any of the flowcharts 1207, 1213 and 1219.
In an embodiment, the invention down-converts the EM signal to an intermediate frequency (IF) signal. FIG. 12B depicts a flowchart 1207 that illustrates a method for under-sampling the EM signal at an aliasing rate to down-convert the EM signal to an IF signal. The process begins at step 1208, which includes receiving an EM signal. Step 1210 includes receiving an aliasing signal having an aliasing rate FAR. Step 1212 includes under-sampling the EM signal at the aliasing rate to down-convert the EM signal to an IF signal.
In another embodiment, the invention down-converts the EM signal to a demodulated baseband information signal. FIG. 12C depicts a flowchart 1213 that illustrates a method for down-converting the EM signal to a demodulated baseband signal. The process begins at step 1214, which includes receiving an EM signal. Step 1216 includes receiving an aliasing signal having an aliasing rate FAR. Step 1218 includes down-converting the EM signal to a demodulated baseband signal. The demodulated baseband signal can be processed without further down-conversion or demodulation.
In another embodiment, the EM signal is a frequency modulated (FM) signal, which is down-converted to a non-FM signal, such as a phase modulated (PM) signal or an amplitude modulated (AM) signal. FIG. 12D depicts a flowchart 1219 that illustrates a method for down-converting the FM signal to a non-FM signal. The process begins at step 1220, which includes receiving an EM signal. Step 1222 includes receiving an aliasing signal having an aliasing rate. Step 1224 includes down-converting the FM signal to a non-FM signal.
The invention down-converts any type of EM signal, including, but not limited to, modulated carrier signals and unmodulated carrier signals. For ease of discussion, the invention is further described herein using modulated carrier signals for examples. Upon reading the disclosure and examples therein, one skilled in the relevant art(s) will understand that the invention can be implemented to down-convert signals other than carrier signals as well. The invention is not limited to the example embodiments described above.
In an embodiment, down-conversion is accomplished by under-sampling an EM signal. This is described generally in Section I.2.2. below and in detail in Section II and its sub-sections. In another embodiment, down-conversion is achieved by transferring non-negligible amounts of energy from an EM signal. This is described generally in Section I.2.3. below and in detail in Section III.
The term aliasing, as used herein, refers both to down-converting an EM signal by under-sampling the EM signal at an aliasing rate and to down-converting an EM signal by transferring energy from the EM signal at the aliasing rate. Methods for under-sampling an EM signal to down-convert the EM signal are now described at an overview level. FIG. 14A depicts a flowchart 1401 that illustrates a method for under-sampling the EM signal at an aliasing rate to down-convert the EM signal. The process begins at step 1402, which includes receiving an EM signal. Step 1404 includes receiving an under-sampling signal having an aliasing rate. Step 1406 includes under-sampling the EM signal at the aliasing rate to down-convert the EM signal.
Down-converting by under-sampling is illustrated by 4504 in FIG. 45A and is described in greater detail in Section II.
2.2.1 Down-Converting to an Intermediate Frequency (IF) Signal
In an embodiment, an EM signal is under-sampled at an aliasing rate to down-convert the EM signal to a lower, or intermediate frequency (IP) signal. The EM signal can be a modulated carrier signal or an unmodulated carrier signal. In an exemplary example, a modulated carrier signal FMC is down-converted to an IF signal FIF.
FIG. 14B depicts a flowchart 1407 that illustrates a method for under-sampling the EM signal at an aliasing rate to down-convert the EM signal to an IF signal. The process begins at step 1408, which includes receiving an EM signal. Step 1410 includes receiving an under-sampling signal having an aliasing rate. Step 1412 includes under-sampling the EM signal at the aliasing rate to down-convert the EM signal to an IF signal.
This embodiment is illustrated generally by 4508 in FIG. 45B and is described in Section II.1.
In another embodiment, an EM signal is directly down-converted to a demodulated baseband signal (direct-to-data down-conversion), by under-sampling the EM signal at an aliasing rate. The EM signal can be a modulated EM signal or an unmodulated EM signal. In an exemplary embodiment, the EM signal is the modulated carrier signal FMC, and is directly down-converted to a demodulated baseband signal FDMB.
FMC→FDMB
FIG. 14C depicts a flowchart 1413 that illustrates a method for under-sampling the EM signal at an aliasing rate to directly down-convert the EM signal to a demodulated baseband signal. The process begins at step 1414, which includes receiving an EM signal. Step 1416 includes receiving an under-sampling signal having an aliasing rate. Step 1418 includes under-sampling the EM signal at the aliasing rate to directly down-convert the EM signal to a baseband information signal.
This embodiment is illustrated generally by 4510 in FIG. 45B and is described in Section II.2
In another embodiment, a frequency modulated (FM) carrier signal FMC is converted to a non-FM signal F(NON-FM), by under-sampling the FM carrier signal FFMC.
FFMC→F(NON-FM)
FIG. 14D depicts a flowchart 1419 that illustrates a method for under-sampling an FM signal to convert it to a non-FM signal. The process begins at step 1420, which includes receiving the FM signal. Step 1422 includes receiving an under-sampling signal having an aliasing rate. Step 1424 includes under-sampling the FM signal at the aliasing rate to convert the FM signal to a non-FM signal. For example, the FM signal can be under-sampled to convert it to a PM signal or an AM signal.
This embodiment is illustrated generally by 4512 in FIG. 45B, and described in Section II.3
The term aliasing, as used herein, refers both to down-converting an EM signal by under-sampling the EM signal at an aliasing rate and to down-converting an EM signal by transferring non-negligible amounts energy from the EM signal at the aliasing rate. Methods for transferring energy from an EM signal to down-convert the EM signal are now described at an overview level. More detailed descriptions are provided in Section III.
FIG. 46A depicts a flowchart 4601 that illustrates a method for transferring energy from the EM signal at an aliasing rate to down-convert the EM signal. The process begins at step 4602, which includes receiving an EM signal. Step 4604 includes receiving an energy transfer signal having an aliasing rate. Step 4606 includes transferring energy from the EM signal at the aliasing rate to down-convert the EM signal.
Down-converting by transferring energy is illustrated by 4506 in FIG. 45A and is described in greater detail in Section III.
2.3.1 Down-Converting to an Intermediate Frequency (IF) Signal
In an embodiment, EM signal is down-converted to a lower, or intermediate frequency (IF) signal, by transferring energy from the EM signal at an aliasing rate. The EM signal can be a modulated carrier signal or an unmodulated carrier signal. In an exemplary example, a modulated carrier signal FMC is down-converted to an IF signal FIF.
FIG. 46B depicts a flowchart 4607 that illustrates a method for transferring energy from the EM signal at an aliasing rate to down-convert the EM signal to an IF signal. The process begins at step 4608, which includes receiving an EM signal. Step 4610 includes receiving an energy transfer signal having an aliasing rate. Step 4612 includes transferring energy from the EM signal at the aliasing rate to down-convert the EM signal to an IF signal.
This embodiment is illustrated generally by 4514 in FIG. 45B and is described in Section III.1.
In another embodiment, an EM signal is down-converted to a demodulated baseband signal by transferring energy from the EM signal at an aliasing rate. This embodiment is referred to herein as direct-to-data down-conversion. The EM signal can be a modulated EM signal or an unmodulated EM signal. In an exemplary embodiment, the EM signal is the modulated carrier signal FMC, and is directly down-converted to a demodulated baseband signal FDMB.
FIG. 46C depicts a flowchart 4613 that illustrates a method for transferring energy from the EM signal at an aliasing rate to directly down-convert the EM signal to a demodulated baseband signal. The process begins at step 4614, which includes receiving an EM signal. Step 4616 includes receiving an energy transfer signal having an aliasing rate. Step 4618 includes transferring energy from the EM signal at the aliasing rate to directly down-convert the EM signal to a baseband signal.
This embodiment is illustrated generally by 4516 in FIG. 45B and is described in Section III.2
In another embodiment, a frequency modulated (FM) carrier signal FFMC is converted to a non-FM signal F(NON-FM), by transferring energy from the FM carrier signal FFMC at an aliasing rate.
The FM carrier signal FFMC can be converted to, for example, a phase modulated (PM) signal or an amplitude modulated (AM) signal. FIG. 46D depicts a flowchart 4619 that illustrates a method for transferring energy from an FM signal to convert it to a non-FM signal. Step 4620 includes receiving the FM signal. Step 4622 includes receiving an energy transfer signal having an aliasing rate. In FIG. 46D, step 4612 includes transferring energy from the FM signal to convert it to a non-FM signal. For example, energy can be transferred from an FSK signal to convert it to a PSK signal or an ASK signal.
This embodiment is illustrated generally by 4518 in FIG. 45B, and described in Section III.3
In accordance with the definition of aliasing, the aliasing rate is equal to, or less than, twice the frequency of the EM carrier signal. Preferably, the aliasing rate is much less than the frequency of the carrier signal. The aliasing rate is preferably more than twice the highest frequency component of the modulating baseband signal FMB that is to be reproduced. The above requirements are illustrated in EQ. (1).
2·F MC ≧F AR>2·(Highest Freq. Component of F MB) EQ. (1)
In other words, by taking a carrier and aliasing it at an aliasing rate, the invention can down-convert that carrier to lower frequencies. One aspect that can be exploited by this invention is that the carrier is not the item of interest; instead the lower baseband signal is of interest to be reproduced sufficiently. The baseband signal's frequency content, even though its carrier may be aliased, satisfies the Nyquist criteria and as a result, the baseband information can be sufficiently reproduced, either as the intermediate modulating carrier signal FIF or as the demodulated direct-to-data baseband signal FDMB.
In accordance with the invention, relationships between the frequency of an EM carrier signal, the aliasing rate, and the intermediate frequency of the down-converted signal, are illustrated in EQ. (2).
F C =n·F AR ±F IF EQ. (2)
FC is the frequency of the EM carrier signal that is to be aliased;
FAR is the aliasing rate;
n identifies a harmonic or sub-harmonic of the aliasing rate (generally, n=0.5, 1, 2, 3, 4, . . . ); and
FIF is the intermediate frequency of the down-converted signal.
Note that as (n·FAR) approaches FC, FIF approaches zero. This is a special case where an EM signal is directly down-converted to a demodulated baseband signal. This special case is referred to herein as Direct-to-Data down-conversion. Direct-to-Data down-conversion is described in later sections.
High level descriptions, exemplary embodiments and exemplary implementations of the above and other embodiments of the invention are provided in sections below.
3. Benefits of the Invention Using an Example Conventional Receiver for Comparison
FIG. 11 illustrates an example conventional receiver system 1102. The conventional system 1102 is provided both to help the reader to understand the functional differences between conventional systems and the present invention, and to help the reader to understand the benefits of the present invention.
The example conventional receiver system 1102 receives an electromagnetic (EM) signal 1104 via an antenna 1106. The EM signal 1104 can include a plurality of EM signals such as modulated carrier signals. For example, the EM signal 1104 includes one or more radio frequency (RF) EM signals, such as a 900 MHZ modulated carrier signal. Higher frequency RF signals, such as 900 MHZ signals, generally cannot be directly processed by conventional signal processors. Instead, higher frequency RF signals are typically down-converted to lower intermediate frequencies (IF) for processing. The receiver system 1102 down-converts the EM signal 1104 to an intermediate frequency (IF) signal 1108 n, which can be provided to a signal processor 1110. When the EM signal 1104 includes a modulated carrier signal, the signal processor 1110 usually includes a demodulator that demodulates the IF signal 1108 n to a baseband information signal (demodulated baseband signal).
Receiver system 1102 includes an RF stage 1112 and one or more IF stages 1114. The RF stage 1112 receives the EM signal 1104. The RF stage 1112 includes the antenna 1106 that receives the EM signal 1104.
The one or more IF stages 1114 a-1114 n down-convert the EM signal 1104 to consecutively lower intermediate frequencies. Each of the one or more IF sections 1114 a-1114 n includes a mixer 1118 a-1118 n that down-converts an input EM signal 1116 to a lower frequency IF signal 1108. By cascading the one or more mixers 1118 a-1118 n, the EM signal 1104 is incrementally down-converted to a desired IF signal 1108 n.
In operation, each of the one or more mixers 1118 mixes an input EM signal 1116 with a local oscillator (LO) signal 1119, which is generated by a local oscillator (LO) 1120. Mixing generates sum and difference signals from the input EM signal 1116 and the LO signal 1119. For example, mixing an input EM signal 1116 a, having a frequency of 900 MHZ, with a LO signal 1119 a, having a frequency of 830 MHZ, results in a sum signal, having a frequency of 900 MHZ+830 MHZ=1.73 GHZ, and a difference signal, having a frequency of 900 MHZ−830 MHZ=70 MHZ.
Specifically, in the example of FIG. 11, the one or more mixers 1118 generate a sum and difference signals for all signal components in the input EM signal 1116. For example, when the EM signal 1116 a includes a second EM signal, having a frequency of 760 MHZ, the mixer 1118 a generates a second sum signal, having a frequency of 760 MHZ+830 MHZ=1.59 GHZ, and a second difference signal, having a frequency of 830 MHZ−760 MHZ=70 MHZ. In this example, therefore, mixing two input EM signals, having frequencies of 900 MHZ and 760 MHZ, respectively, with an LO signal having a frequency of 830 MHZ, results in two IF signals at 70 MHZ.
Generally, it is very difficult, if not impossible, to separate the two 70 MHZ signals. Instead, one or more filters 1122 and 1123 are provided upstream from each mixer 1118 to filter the unwanted frequencies, also known as image frequencies. The filters 1122 and 1123 can include various filter topologies and arrangements such as bandpass filters, one or more high pass filters, one or more low pass filters, combinations thereof, etc.
Typically, the one or more mixers 1118 and the one or more filters 1122 and 1123 attenuate or reduce the strength of the EM signal 1104. For example, a typical mixer reduces the EM signal strength by 8 to 12 dB. A typical filter reduces the EM signal strength by 3 to 6 dB.
As a result, one or more low noise amplifiers (LNAs) 1121 and 1124 a-1124 n are provided upstream of the one or more filters 1123 and 1122 a-1122 n. The LNAs and filters can be in reversed order. The LNAs compensate for losses in the mixers 1118, the filters 1122 and 1123, and other components by increasing the EM signal strength prior to filtering and mixing. Typically, for example, each LNA contributes 15 to 20 dB of amplification.
However, LNAs require substantial power to operate. Higher frequency LNAs require more power than lower frequency LNAs. When the receiver system 1102 is intended to be portable, such as a cellular telephone receiver, for example, the LNAs require a substantial portion of the total power.
At higher frequencies, impedance mismatches between the various stages further reduce the strength of the EM signal 1104. In order to optimize power transferred through the receiver system 1102, each component should be impedance matched with adjacent components. Since no two components have the exact same impedance characteristics, even for components that were manufactured with high tolerances, impedance matching must often be individually fine tuned for each receiver system 1102. As a result, impedance matching in conventional receivers tends to be labor intensive and more art than science. Impedance matching requires a significant amount of added time and expense to both the design and manufacture of conventional receivers. Since many of the components, such as LNA, filters, and impedance matching circuits, are highly frequency dependent, a receiver designed for one application is generally not suitable for other applications. Instead, a new receiver must be designed, which requires new impedance matching circuits between many of the components.
Conventional receiver components are typically positioned over multiple IC substrates instead of on a single IC substrate. This is partly because there is no single substrate that is optimal for both RF, IF, and baseband frequencies. Other factors may include the sheer number of components, their various sizes and different inherent impedance characteristics, etc. Additional signal amplification is often required when going from chip to chip. Implementation over multiple substrates thus involves many costs in addition to the cost of the ICs themselves.
Conventional receivers thus require many components, are difficult and time consuming to design and manufacture, and require substantial external power to maintain sufficient signal levels. Conventional receivers are thus expensive to design, build, and use.
In an embodiment, the present invention is implemented to replace many, if not all, of the components between the antenna 1106 and the signal processor 1110, with an aliasing module that includes a universal frequency translator (UFT) module. The UFT is able to down-convert a wide range of EM signal frequencies using very few components. The UFT is easy to design and build, and requires very little external power. The UFT design can be easily tailored for different frequencies or frequency ranges. For example, UFT design can be easily impedance matched with relatively little tuning. In a direct-to-data embodiment of the invention, where an EM signal is directly down-converted to a demodulated baseband signal, the invention also eliminates the need for a demodulator in the signal processor 1110.
When the invention is implemented in a receiver system, such as the receiver system 1102, power consumption is significantly reduced and signal to noise ratio is significantly increased.
In an embodiment, the invention can be implemented and tailored for specific applications with easy to calculate and easy to implement impedance matching circuits. As a result, when the invention is implemented as a receiver, such as the receiver 1102, specialized impedance matching experience is not required.
In conventional receivers, components in the IF sections comprise roughly eighty to ninety percent of the total components of the receivers. The UFT design eliminates the IF section(s) and thus eliminates the roughly eighty to ninety percent of the total components of conventional receivers.
Other advantages of the invention include, but are not limited to:
The invention can be implemented as a receiver with only a single local oscillator;
The invention can be implemented as a receiver with only a single, lower frequency, local oscillator;
The invention can be implemented as a receiver using few filters;
The invention can be implemented as a receiver using unit delay filters;
The invention can be implemented as a receiver that can change frequencies and receive different modulation formats with no hardware changes;
The invention can be also be implemented as frequency up-converter in an EM signal transmitter;
The invention can be also be implemented as a combination up-converter (transmitter) and down-converter (receiver), referred to herein as a transceiver;
The invention can be implemented as a method and system for ensuring reception of a communications signal, as disclosed in U.S. patent application Ser. No. 09/176,415, filed Oct. 21, 1998, incorporated herein by reference in its entirety;
The invention can be implemented in a differential configuration, whereby signal to noise ratios are increased;
A receiver designed in accordance with the invention can be implemented on a single IC substrate, such as a silicon-based IC substrate;
A receiver designed in accordance with the invention and implemented on a single IC substrate, such as a silicon-based IC substrate, can down-convert EM signals from frequencies in the giga Hertz range;
A receiver built in accordance with the invention has a relatively flat response over a wide range of frequencies. For example, in an embodiment, a receiver built in accordance with the invention to operate around 800 MHZ has a substantially flat response (i.e., plus or minus a few dB of power) from 100 MHZ to 1 GHZ. This is referred to herein as a wide-band receiver; and
A receiver built in accordance with the invention can include multiple, user-selectable, Impedance match modules, each designed for a different wide-band of frequencies, which can be used to scan an ultra-wide-band of frequencies.
II. DOWN-CONVERTING BY UNDER-SAMPLING
1. Down-Converting an EM Carrier Signal to an EM Intermediate Signal by Under-Sampling the EM Carrier Signal at the Aliasing Rate
In an embodiment, the invention down-converts an EM signal to an IF signal by under-sampling the EM signal. This embodiment is illustrated by 4508 in FIG. 45B.
This embodiment can be implemented with modulated and unmodulated EM signals. This embodiment is described herein using the modulated carrier signal FMC in FIG. 1, as an example. In the example, the modulated carrier signal FMC is down-converted to an IF signal FIF. The IF signal FIF can then be demodulated, with any conventional demodulation technique to obtain a demodulated baseband signal FDMB. Upon reading the disclosure and examples therein, one skilled in the relevant art(s) will understand that the invention can be implemented to down-convert any EM signal, including but not limited to, modulated carrier signals and unmodulated carrier signals.
The following sections describe example methods for down-converting the modulated carrier signal FMC to the IF signal FIF, according to embodiments of the invention. Exemplary structural embodiments for implementing the methods are also described. It should be understood that the invention is not limited to the particular embodiments described below. Equivalents, extensions, variations, deviations, etc., of the following will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such equivalents, extensions, variations, deviations, etc., are within the scope and spirit of the present invention.
The following sections include a high level discussion, example embodiments, and implementation examples.
This section (including its subsections) provides a high-level description of down-converting an EM signal to an IF signal FIF according to the invention. In particular, an operational process of under-sampling a modulated carrier signal FMC to down-convert it to the IF signal FIF, is described at a high-level. Also, a structural implementation for implementing this process is described at a high-level. This structural implementation is described herein for illustrative purposes, and is not limiting. In particular, the process described in this section can be achieved using any number of structural implementations, one of which is described in this section. The details of such structural implementations will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.
FIG. 14B depicts a flowchart 1407 that illustrates an exemplary method for under-sampling an EM signal to down-convert the EM signal to an intermediate signal FIF. The exemplary method illustrated in the flowchart 1407 is an embodiment of the flowchart 1401 in FIG. 14A.
Any and all combinations of modulation techniques are valid for this invention. For ease of discussion, the digital AM carrier signal 616 is used to illustrate a high level operational description of the invention. Subsequent sections provide detailed flowcharts and descriptions for AM, FM and PM example embodiments. Upon reading the disclosure and examples therein, one skilled in the relevant art(s) will understand that the invention can be implemented to down-convert any type of EM signal, including any form of modulated carrier signal and unmodulated carrier signals.
The method illustrated in the flowchart 1407 is now described at a high level using the digital AM carrier signal 616 of FIG. 6C. The digital AM carrier signal 616 is re-illustrated in FIG. 15A for convenience. FIG. 15E illustrates a portion 1510 of the AM carrier signal 616, between time t1 and t2, on an expanded time scale.
The process begins at step 1408, which includes receiving an EM signal. Step 1408 is represented by the digital AM carrier signal 616.
Step 1410 includes receiving an under-sampling signal having an aliasing rate FAR. FIG. 15B illustrates an example under-sampling signal 1502, which includes a train of pulses 1504 having negligible apertures that tend toward zero time in duration. The pulses 1504 repeat at the aliasing rate, OF pulse repetition rate. Aliasing rates are discussed below.
Step 1412 includes under-sampling the EM signal at the aliasing rate to down-convert the EM signal to the intermediate signal FIF. When down-converting an EM signal to an IF signal, the frequency or aliasing rate of the pulses 1504 sets the IF.
FIG. 15C illustrates a stair step AM intermediate signal 1506, which is generated by the down-conversion process. The AM intermediate signal 1506 is similar to the AM carrier signal 616 except that the AM intermediate signal 1506 has a lower frequency than the AM carrier signal 616. The AM carrier signal 616 has thus been down-converted to the AM intermediate signal 1506. The AM intermediate signal 1506 can be generated at any frequency below the frequency of the AM carrier signal 616 by adjusting the aliasing rate.
FIG. 15D depicts the AM intermediate signal 1506 as a filtered output signal 1508. In an alternative embodiment, the invention outputs a stair step, non-filtered or partially filtered output signal. The choice between filtered, partially filtered and non-filtered output signals is generally a design choice that depends upon the application of the invention.
The intermediate frequency of the down-converted signal FIF, which in this example is the AM intermediate signal 1506, can be determined from EQ. (2), which is reproduced below for convenience.
A suitable aliasing rate FAR can be determined in a variety of ways. An example method for determining the aliasing rate FAR, is provided below. After reading the description herein, one skilled in the relevant art(s) will understand how to determine appropriate aliasing rates for EM signals, including ones in addition to the modulated carrier signals specifically illustrated herein.
In FIG. 17, a flowchart 1701 illustrates an example process for determining an aliasing rate FAR. But a designer may choose, or an application may dictate, that the values be determined in an order that is different than the illustrated order. The process begins at step 1702, which includes determining, or selecting, the frequency of the EM signal. The frequency of the FM carrier signal 616 can be, for example, 901 MHZ.
Step 1704 includes determining, or selecting, the intermediate frequency. This is the frequency to which the EM signal will be down-converted. The intermediate frequency can be determined, or selected, to match a frequency requirement of a down-stream demodulator. The intermediate frequency can be, for example, 1 MHZ.
Step 1706 includes determining the aliasing rate or rates that will down-convert the EM signal to the IF specified in step 1704.
EQ. (2) can be rewritten as EQ. (3):
n·Far=F C ±F IF EQ. (3)
Which can be rewritten as EQ. (4):
n = F C ± F IF F AR EQ . ⁢ ( 4 )
or as EQ. (5):
F AR = F C ± F IF n EQ . ⁢ ( 5 )
(FC±FIF) can be defined as a difference value FDIFF, as illustrated in EQ. (6):
(F C ±F IF)=F DIFF EQ. (6)
EQ. (4) can be rewritten as EQ. (7):
n = F DIFF F AR EQ . ⁢ ( 7 )
From EQ. (7), it can be seen that, for a given n and a constant FAR, FDIFF is constant. For the case of FDIFF=FC−FIF, and for a constant FDIFF, as FC increases, FIF necessarily increases. For the case of FDIFF=FC+FIF, and for a constant FDIFF, as FC increases, FIF necessarily decreases. In the latter case of FDIFF=FC+FIF, any phase or frequency changes on FC correspond to reversed or inverted phase or frequency changes on FIF. This is mentioned to teach the reader that if FDIFF=FC+FIF is used, the above effect will affect the phase and frequency response of the modulated intermediate signal FIF.
EQs. (2) through (7) can be solved for any valid n. A suitable n can be determined for any given difference frequency FDIFF and for any desired aliasing rate FAR(Desired). EQs. (2) through (7) can be utilized to identify a specific harmonic closest to a desired aliasing rate FAR(Desired) that will generate the desired intermediate signal FIF.
An example is now provided for determining a suitable n for a given difference frequency FDIFF and for a desired aliasing rate FAR(Desired). For ease of illustration, only the case of (FC−FIF) is illustrated in the example below.
n = F C - F IF F AR ( Desired ) = F DIFF F AR ( Desired )
The desired aliasing rate FAR(Desired) can be, for example, 140 MHZ. Using the previous examples, where the carrier frequency is 901 MHZ and the IF is 1 MHZ, an initial value of n is determined as:
n = 901 ⁢ ⁢ MHZ - 1 ⁢ ⁢ MHZ 140 ⁢ ⁢ MHZ = 900 140 = 6.4
The initial value 6.4 can be rounded up or down to the valid nearest n, which was defined above as including (0.5, 1, 2, 3, . . . ). In this example, 6.4 is rounded down to 6.0, which is inserted into EQ. (5) for the case of (FC−FIF)=FDIFF:
F AR = F c - F IF n F AR = 901 ⁢ ⁢ MHZ - 1 ⁢ ⁢ MHZ 6 - 900 ⁢ ⁢ MHZ 6 = 150 ⁢ ⁢ MHZ
In other words, under-sampling a 901 MHZ EM carrier signal at 150 MHZ generates an intermediate signal at 1 MHZ. When the under-sampled EM carrier signal is a modulated carrier signal, the intermediate signal will also substantially include the modulation. The modulated intermediate signal can be demodulated through any conventional demodulation technique.
Alternatively, instead of starting from a desired aliasing rate, a list of suitable aliasing rates can be determined from the modified form of EQ. (5), by solving for various values of n. Example solutions are listed below.
F AR = ( F C - F IF ) n = F DIFF n = 901 ⁢ ⁢ MHZ - 1 ⁢ ⁢ MHZ n = 900 ⁢ ⁢ MHZ n
Solving for n=0.5, 1, 2, 3, 4, 5 and 6:
900 MHZ/0.5=1.8 GHZ (i.e., second harmonic, illustrated in FIG. 25A as 2502);
900 MHZ/1=900 MHZ (i.e., fundamental frequency, illustrated in FIG. 25B as 2504);
900 MHZ/2=450 MHZ (i.e., second sub-harmonic, illustrated in FIG. 25C as 2506);
900 MHZ/3=300 MHZ (i.e., third sub-harmonic, illustrated in FIG. 25D as 2508);
900 MHZ/4=225 MHZ (i.e., fourth sub-harmonic, illustrated in FIG. 25E as 2510);
900 MHZ/15=180 MHZ (i.e., fifth sub-harmonic, illustrated in FIG. 25F as 2512); and
900 MHZ/6=150 MHZ (i.e., sixth sub-harmonic, illustrated in FIG. 25G as 2514).
The steps described above can be performed for the case of (FC+FIF) in a similar fashion. The results can be compared to the results obtained from the case of (FC−FIF) to determine which provides better result for an application.
In an embodiment, the invention down-converts an EM signal to a relatively standard IF in the range of, for example, 100 KHZ to 200 MHZ. In another embodiment, referred to herein as a small off-set implementation, the invention down-converts an EM signal to a relatively low frequency of, for example, less than 100 KHZ. In another embodiment, referred to herein as a large off-set implementation, the invention down-converts an EM signal to a relatively higher IF signal, such as, for example, above 200 MHZ.
The various off-set implementations provide selectivity for different applications. Generally, lower data rate applications can operate at lower intermediate frequencies. But higher intermediate frequencies can allow more information to be supported for a given modulation technique.
In accordance with the invention, a designer picks an optimum information bandwidth for an application and an optimum intermediate frequency to support the baseband signal. The intermediate frequency should be high enough to support the bandwidth of the modulating baseband signal FMB.
Generally, as the aliasing rate approaches a harmonic or sub-harmonic frequency of the EM signal, the frequency of the down-converted IF signal decreases. Similarly, as the aliasing rate moves away from a harmonic or sub-harmonic frequency of the EM signal, the IF increases.
Aliased frequencies occur above and below every harmonic of the aliasing frequency. In order to avoid mapping other aliasing frequencies in the band of the aliasing frequency (IF) of interest, the IF of interest is preferably not near one half the aliasing rate.
As described in example implementations below, an aliasing module, including a universal frequency translator (UFT) module built in accordance with the invention, provides a wide range of flexibility in frequency selection and can thus be implemented in a wide range of applications. Conventional systems cannot easily offer, or do not allow, this level of flexibility in frequency selection.
FIG. 16 illustrates a block diagram of an under-sampling system 1602 according to an embodiment of the invention. The under-sampling system 1602 is an example embodiment of the generic aliasing system 1302 in FIG. 13. The under-sampling system 1602 includes an under-sampling module 1606. The under-sampling module 1606 receives the EM signal 1304 and an under-sampling signal 1604, which includes under-sampling pulses having negligible apertures that tend towards zero time, occurring at a frequency equal to the aliasing rate FAR. The under-sampling signal 1604 is an example embodiment of the aliasing signal 1310. The under-sampling module 1606 under-samples the EM signal 1304 at the aliasing rate FAR Of the under-sampling signal 1604. The under-sampling system 1602 outputs a down-converted signal 1308A.
Preferably, the under-sampling module 1606 under-samples the EM signal 1304 to down-convert it to the intermediate signal FIF in the manner shown in the operational flowchart 1407 of FIG. 14B. But it should be understood that the scope and spirit of the invention includes other structural embodiments for performing the steps of the flowchart 1407. The specifics of the other structural embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein. In an embodiment, the aliasing rate FAR of the under-sampling signal 1604 is chosen in the manner discussed in Section II.1.1.1 so that the under-sampling module 1606 under-samples the EM carrier signal 1304 generating the intermediate frequency FIF.
The operation of the under-sampling system 1602 is now described with reference to the flowchart 1407 and to the timing diagrams in FIGS. 15A-D. In step 1408, the under-sampling module 1606 receives the AM signal 616 (FIG. 15A). In step 1410, the under-sampling module 1606 receives the under-sampling signal 1502 (FIG. 15B). In step 1412, the under-sampling module 1606 under-samples the AM carrier signal 616 at the aliasing rate of the under-sampling signal 1502, or a multiple thereof, to down-convert the AM carrier signal 616 to the intermediate signal 1506 (FIG. 15D).
Example implementations of the under-sampling module 1606 are provided in Sections 4 and 5 below.
1.1 Example Embodiments
Various embodiments related to the method(s) and structure(s) described above are presented in this section (and its subsections). These embodiments are described herein for purposes of illustration, and not limitation. The invention is not limited to these embodiments. Alternate embodiments (including equivalents, extensions, variations, deviations, etc., of the embodiments described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. The invention is intended and adapted to include such alternate embodiments.
The method for down-converting the EM signal 1304 to the intermediate signal FIF, illustrated in the flowchart 1407 of FIG. 14B, can be implemented with any type of EM signal, including unmodulated EM carrier signals and modulated carrier signals including, but not limited to, AM, FM, PM, etc., or any combination thereof. Operation of the flowchart 1407 of FIG. 14B is described below for AM, FM and PM carrier signals. The exemplary descriptions below are intended to facilitate an understanding of the present invention. The present invention is not limited to or by the exemplary embodiments below.
Operation of the exemplary process of the flowchart 1407 in FIG. 14B