Source: http://www.google.com/patents/US6591091?dq=5987118
Timestamp: 2015-11-25 03:27:27
Document Index: 586459880

Matched Legal Cases: ['in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'in fine']

Patent US6591091 - System and method for coarse/fine PLL adjustment - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsAn integrated receiver with channel selection and image rejection substantially implemented on a single CMOS integrated circuit is described. A receiver front end provides programable attenuation and a programable gain low noise amplifier. Frequency conversion circuitry advantageously uses LC filters...http://www.google.com/patents/US6591091?utm_source=gb-gplus-sharePatent US6591091 - System and method for coarse/fine PLL adjustmentAdvanced Patent SearchPublication numberUS6591091 B1Publication typeGrantApplication numberUS 09/438,688Publication dateJul 8, 2003Filing dateNov 12, 1999Priority dateNov 12, 1998Fee statusLapsedAlso published asDE69920273D1, DE69920273T2, EP1145430A2, EP1145430B1, US6285865, US6377315, US6504420, US6549766, US6865381, US6879816, US7092043, US7109781, US7199664, US7236212, US7366486, US7423699, US7515895, US7729676, US7821581, US8045066, US8111095, US8195117, US20010007151, US20010008430, US20010011013, US20020140869, US20030022646, US20030107427, US20030162521, US20030194978, US20050107055, US20050153677, US20070013433, US20070077908, US20070120605, US20080284919, US20100237884, US20110067083, WO2000028664A2, WO2000028664A3, WO2000028664A8Publication number09438688, 438688, US 6591091 B1, US 6591091B1, US-B1-6591091, US6591091 B1, US6591091B1InventorsPieter Vorenkamp, Klaas Bult, Frank CarrOriginal AssigneeBroadcom CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (28), Non-Patent Citations (5), Referenced by (69), Classifications (108), Legal Events (11) External Links: USPTO, USPTO Assignment, EspacenetSystem and method for coarse/fine PLL adjustment
US 6591091 B1Abstract
What is claimed is: 1. A method of tuning a receiver that maintains a signal output from the receiver during the tuning process comprising:
selecting a channel to be tuned; tuning the channel to approximately a desired first intermediate frequency by a first frequency source that is adjustable in coarse steps and having a wide bandwidth; filtering the channel at the desired first intermediate frequency in a bandpass filter having passband that is sufficiently wide to pass the channel and a portion of another channel; and tuning the channel at the first intermediate frequency to a second intermediate frequency by a second frequency source that is adjustable in fine steps and having a narrow bandwidth relative to the wide bandwidth of the first frequency source; wherein the tuning steps are performed in accordance with the following equation:
FLO1−FSIG−(5/4*FLO2)=Fif, where
FLO1 is the frequency of the first frequency source, FLO2 is the frequency of the second frequency source, Fif is the second intermediate frequency, and FSIG is the frequency of the channel to be tuned. 2. The method of tuning a receiver that maintains a signal output from the receiver during the tuning process of claim 1 wherein the coarse step is 10 MHz.
3. The method of tuning a receiver that maintains a signal output from the receiver during the tuning process of claim 1 wherein the fine step is 100 KHz.
4. The method of tuning a receiver that maintains a signal output from the receiver during the tuning process of claim 1, wherein the portion of another channel is sufficiently wide to accommodate a frequency error in the channel caused by the coarse steps.
5. The method of tuning a receiver that maintains a signal output from the receiver during the tuning process of claim 4, wherein the portion of another channel is approximately 4 MHz.
6. A method of tuning a receiver that maintains a signal output from the receiver during the tuning process comprising:
selecting a channel to be tuned; tuning the channel to approximately a desired first intermediate frequency by a frequency source that is adjustable in coarse steps; bandpass filtering the channel at the desired first intermediate frequency so as to pass the channel and a portion of another channel; tuning the channel at the first intermediate frequency to a second intermediate frequency by a frequency source that is adjustable in fine steps; and tuning the channel at the second intermediate frequency to a third intermediate frequency by a direct synthesis frequency source having a divider circuit to produce an output frequency that is in a fixed relationship to the frequency source adjustable in fine steps. 7. The method of tuning a receiver that maintains a signal output from the receiver during the tuning process of claim 6, wherein the fixed relationship to the second frequency source adjustable in fine steps is a ratio of one-fourth.
8. The method of tuning a receiver that maintains a signal output from the receiver during the tuning process of claim 6, wherein the portion of another channel is sufficiently wide to accommodate a frequency error in the channel caused by the coarse steps.
9. The method of tuning a receiver that maintains a signal output from the receiver during the tuning process of claim 8, wherein the portion of another channel is approximately 4 MHz.
10. A method of tuning a receiver, comprising:
selecting a desired channel to be tuned; tuning the desired channel to approximately a desired first intermediate frequency by using a first phase lock loop that is adjustable in coarse frequency steps and having a wide bandwidth; filtering the desired channel at the desired first intermediate frequency in a bandpass filter having passband, the passband being wide enough to accommodate any frequency error of the desired channel relative to the desired first intermediate frequency that is caused by the coarse frequency steps; and tuning the desired channel at the first intermediate frequency to a second intermediate frequency by a second phase lock loop that is adjustable in fine frequency steps and having a narrow bandwidth relative to the wide bandwidth of the first phase lock loop; wherein the tuning steps are performed in accordance with the following equation:
FLO1 is the frequency of the first phase lock loop, FLO2 is the frequency of the second phase lock loop, Fif is the second intermediate frequency, and FSIG is the frequency of the desired channel to be tuned. 11. The method of claim 10, wherein the coarse frequency steps are approximately 10 MHz.
12. The method of claim 10, wherein the fine frequency steps are approximately 100 kHz.
13. The method of claim 10, wherein the passband is sufficiently wide to accommodate up to 10 MHz of frequency error caused by the coarse frequency steps.
This application claims the benefit of U.S. Provisional Patent Application Nos. 60/108,459, 60/108,209, 60/108,210 filed Nov. 12, 1998; U.S. Provisional Application No. 60/117,609 filed Jan. 28, 1999; U.S. Provisional Application Nos. 60/136,115 and 60/136,116 filed May 26, 1999; U.S. Provisional Application No. 60/136,654 filed May 27, 1999; and U.S. Provisional Application No. 60/159,726 filed Oct. 15, 1999; the contents of which are hereby incorporated by reference.
There is therefore provided in a present embodiment of the invention a method of tuning a receiver that maintains a signal output from the receiver during the tuning process. The process comprises selecting a channel to be tuned, tuning that channel to approximately a desired first intermediate frequency by a frequency source that is adjustable in coarse steps. And tuning the channel at the first intermediate frequency to a second intermediate frequency by a frequency source that is adjustable in fine steps.
Many of the attendant features of this invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description considered in connection with the accompanying drawings, in which like reference symbols designate like parts throughout.
FIG. 24a is a block diagram of a tuning process,
FIG. 24b is a flow diagram of the tuning process, and
Third order products 308 occur at (f1−Δf) and at (f2+Δf), where Δf=f2−f1. These unwanted signals may be generated in a transmitter and transmitted along with desired signal or are created in a receiver. Circuitry in the receiver is required to block these signals. These unwanted spurious responses arise from nonlinearities in the circuitry that makes up the receiver.
While unwanted distortion such as harmonic distortion, can be filtered out because the harmonics most often fall outside of the frequency band received, other distortion such as intermodulation distortion is more problematic. This distortion falls within a received signal band and cannot be easily filtered out without blocking other desired signals. Thus, frequency planning is often used to control the location of distortion signals that degrade selectivity.
Selectivity is a measure of a radio receiver's ability to reject signals outside of the band being tuned by a radio receiver. A way to increase selectivity is to provide a resonant circuit after an antenna and before the receiver's frequency conversion circuitry in a “front end.” For example, a parallel resonant circuit after an antenna and before a first mixer that can be tuned to the band desired will-produce a high impedance to ground at the center of the band. The high impedance will allow the antenna signal to develop a voltage across this impedance. Signals out of band will not develop the high voltage and are thus attenuated.
The out of band signal rejection is determined by a quality factor or “Q” of components used in the resonant circuit. The higher the Q of a circuit in the pre-selector, the steeper the slope of the impedance curve that is characteristic of the pre-selector will be. A steep curve will develop a higher voltage at resonance for signals in band compared to signals out of band. For a resonant circuit with low Q a voltage developed across the resonant circuit at a tuned frequency band will be closer in value to the voltage developed across the resonant circuit out of band. Thus, an out of band signals would be closer in amplitude to an in band signals than if a high Q circuit were constructed.
This type of resonant circuit used as a pre-selector will increase frequency selectivity of a receiver that has been designed with this stage at its input. If an active pre-selector circuit is used between an antenna and frequency conversion stages, the sensitivity of the receiver will be increased as well as improving selectivity. If a signal is weak its level will be close to a background noise level that is present on an antenna in addition to a signal. If this signal cannot be separated from the noise, the radio signal will not be able to be converted to a signal usable by the receiver. Within the receiver's signal processing chain, the signal's amplitude is decreased by losses at every stage of the processing. To make up for this loss the signal can be amplified initially before it is processed. Thus, it can be seen why it is desirable to provide a circuit in the receiver that provides frequency selectivity and gain early in the signal processing chain.
In addition to the noise that is present on an antenna or a cable input to a receiver, noise is generated inside the radio receiver. At a UHF frequency range this internal noise predominates over the noise received with the signal of interest. Thus, for the higher frequencies the weakest signal that can be detected is determined by the noise level in the receiver. To increase the sensitivity of the receiver a “pre-