UIllted States Patent
`
`[19]
`
`HflflMMHMNHMHMHMHWHMHMMHMWHWWHH
`U3005530929A
`[11] Patent Number:
`
`5 530 929
`9
`9
`
`Lindqvist et al.
`[45] Date of Patent:
`Jun. 25, 1996
`
`
`[54] HOMODYNE RECEIVER M1NHVIIZING
`,
`OSCILLATOR LEAKAGE
`
`[75]
`
`Inventors: Bjfirn Lindqvist, Bjiirred; Martin
`Isberg, Lund, both of Sweden
`
`2/1993 Petty ....................................... 455/260
`5,187,722
`8/1993 Dent .
`5,241,702
`........................... 455/324
`4/1993 Manjo et al.
`5,263,197
`11/1994 Watanabe et a1.
`...................... 455/317
`5,361,408
`FOREIGN PATENT DOCUMENTS
`
`[73] Assignee: Ericsson GE Mobile Communications
`Inc., Research Triangle Park, NC.
`
`3240565
`2170368
`WO92/01337
`
`5/1984 Germany .
`7/1986 United Kingdom .
`1/1992 WIPO .
`
`[21] Appl. No.: 303,183
`[22]
`Filed'
`Sep 8 1994
`‘
`'
`’
`[30]
`Foreign Application Priority Data
`
`Sweden .................................. 9302934
`[SE]
`Sep. 9, 1993
`[51]
`Int. C1.6 ....................................................... H043 1/26
`[52] US. Cl.
`........................ 455/324; 455/310; 455/318
`[58] Field of Search ..................................... 455/300 310
`455/301 313’ 314 317 318 323, 324’
`255 258 260 315 296‘ 331/51 53’
`’
`’
`’
`’
`’
`’
`References Cited
`
`[56]
`
`4 063 173
`4:783:843
`5,029,237
`5,146,186
`
`U-S- PATENT DOCUMENTS
`12/1977 Nelson et al.
`.......................... 455/315
`11/1988 Leif et a1.
`.....
`455/315
`
`
`7/1991 Ragan ......................... 455/255
`9/1992 Vella ....................................... 455/260
`
`Primary Examiner—Andrew I. Faile
`Attorney, Agent, or Finn—Burns, Doane, Swecker & Mathis
`57
`ABSTRACT
`[
`]
`A method and a device in a homodyne receiver including a
`local oscillator generating an oscillator signal at a frequency
`of fLo, a mixer, and a reception device for receiving an input
`signal having a frequency of fRF, the oscillator signal and the
`ihpm Signal being supplied ‘0 the mixer- The eseihater
`signal is supplied 1.0 a first processing 111111.120 produce a first
`output signal having a frequency of M*fL0, where M is an
`integer value. The first output signal is supplied to a second
`processing unit to produce a second output signal having a
`frequency of M*fL0/N=fL0, where N is an integer number
`and MiN, and the mixer and the second processing unit are
`integrated to minimize leakage 0f Signals being “91’1in 1°
`the mixer from the second PreeeSSihg “hit-
`
`5 Claims, 1 Drawing Sheet
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`SONY EXHIBIT 1011 - 0001
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`SONY EXHIBIT 1011 - 0001
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`

`

`US. Patent
`
`Jun. 25, 1996
`
`5,530,929
`
`F/ G.
`
`/
`
`PRIOR A f? 7'
`
`12
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`SONY EXHIBIT 1011 - 0002
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`SONY EXHIBIT 1011 - 0002
`
`

`

`1
`HOMODYNE RECEIVER NflNINIIZING
`OSCILLATOR LEAKAGE
`
`5,530,929
`
`2
`
`BACKGROUND
`
`The invention relates to a method and a device in a
`homodyne receiver to be used in radio,
`tele, and data
`communication systems such as portable cellular phones,
`cordless phones, pagers, carrier frequency systems, TV
`cable systems, etc. Receivers in this technical field should
`preferably be small, lightweight and inexpensive.
`The first generation of cellular systems relied on analogue
`frequency modulation for speech transmission, and several
`standards have been developed, such as NMT450, NMT900,
`AMPS, and ETACS.
`
`The second generation of cellular systems follows three
`different standards: in Europe and some countries in Asia
`and Australia—Global System For Mobile Communications
`(GSM),
`in north America—American Digital Cellular
`(ADC), and in Japan—Pacific Digital Cellular (PDC). These
`systems all employ digital voice transmission and some
`digital services such as facsimile transmission and short
`messages.
`
`To make the portables smaller and less expensive much
`research has been done to increase the level of integration of
`different parts in the phone.
`Prior art receivers that have been used in this technical
`
`field were of the conventional heterodyne type. For appli-
`cations in small low cost mobile communication systems
`these receivers suffer from high production costs caused by
`expensive and non—integrable RF and IF components such as
`band pass filters. To overcome such drawbacks alternative
`receivers have been developed. These receivers are based on
`the direct conversion principle. The local oscillator fre-
`quency is equal
`to the received carrier frequency and,
`consequently, the received signal is converted to the base
`band in one single step. This concept was first introduced for
`SSE-receivers but can be used in many different types of
`modulation, particularly for digital quadrature modulation
`schemes.
`
`In a homodyne receiver or a zero-IF-receiver the received
`signal and the local oscillator operate at exactly the same
`frequency. Since there are no intermediate frequencies (IF)
`many filters can be omitted or simplified. The operation of
`the homodyne receiver can be described as follows. The RF
`signal of center frequency f: and bandwith Beris amplified
`with a low noise amplifier to improve the total noise figure
`of the receiver. The signal is then split and down converted
`to DC by mixers in both channels. The down converted
`
`spectrum is folded over itself and spans from DC to 1/2 BW,f.
`The low frequency signals I and Q provided by the mixers
`are then filtered to remove any adjacent channel and ampli-
`fied to set
`the noise floor. The I and Q signals or the
`quadrature signals will allow basically any type of modu-
`lation when an appropriate signal processing is utilized.
`A major drawback of direct conversion receivers is spu-
`rious emission. The main source of spurious emission in a
`direct conversion receiver is local oscillator leakage. In an
`ordinary super heterodyne receiver the local oscillator leak—
`age to the antenna is attenuated by the first receiver bandpass
`filter. In a direct conversion receiver this is not the case since
`the local oscillator frequency lies within the passband of this
`bandpass filter. At least two types of leakage are present in
`a direct conversion receiver. The first type is wire bound»
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`leakage, and a second type is radiated leakage caused by
`parasitic coupling between leads and/or bonding wires.
`Different methods have been suggested to overcome the
`problems with spurious emissions. W092/Ol337 discloses a
`direct conversion receiver comprising an antenna, a RF-
`filter, an amplifier and a mixer. A local oscillator, operating
`at a subharrnonic of the received frequency, provides a
`signal to the mixer. A standard type mixer is used and a
`normal drawback of such a mixer, is that harmonics will be
`generated in the mixer when a signal of a frequency lower
`than the received signal is fed to the mixer from the L0 is
`utilized to obtain the wanted signal
`in the mixer. Even
`though the local oscillator operates at a subharmonic of the
`received signal also harmonics will be generated. Some of
`these harmonics will
`in fact correspond to the received
`signal, and spurious emission will occur at some level.
`In DE 3240565 another type of homodyne receiver is
`disclosed. The L0 of this receiver is a controllable oscillator
`
`that generates a signal with a frequency forming a multiple
`of the receiver frequency. The generated signal is then phase
`shifted 180° and divided to the frequency of the RF-signal.
`A major drawback in a receiver having a LO operating at a
`multiple of the received frequency is the difficulties to obtain
`the required characteristics of the LO. For instance the
`power consumption of such an oscillator will be diflicult to
`match to the demands of a low total power consumption of
`the receiver.
`
`SUMMARY
`
`invention the problems and
`According to the present
`drawbacks of direct conversion receivers mentioned above
`are overcome by the use of a local oscillator, the frequency
`output thereof being processed in two steps before it is fed
`to the mixer. Preferably the frequency is both multiplied and
`divided before being supplied to the mixer. The final pro-
`cessing of the oscillator frequency to obtain the frequency of
`the received signal is not made until immediately before the
`mixer, preferably on the same chip as the mixer.
`
`BRIEF DESCRIPTION OF DRAWINGS
`
`Further features, advantages and details of the invention
`are set forth in the following description, drawings and
`claims.
`
`FIG. 1 is a functional block diagram of a prior art
`homodyne receiver, and
`
`FIG. 2 is a block diagram of a preferred embodiment of
`a homodyne receiver according to the invention.
`
`DETAILED DESCRIPTION
`
`In FIG. 1 a prior art homodyne received is shown. In the
`receiver of FIG. 1 quadrature modulation is utilized. An
`antenna 12 receives electromagnetic energy transmitted
`from a transmitter not shown in the drawings. The received
`signal is fed to a first band pass filter 15, which is provided
`to select the correct communication band to improve the
`blocking characteristics of the receiver. Strong signals out-
`side of the received band are attenuated and therefore do not
`degrade the receiver performance.
`An output of said bandpass filter 15 is connected to a low
`noise amplifier 16 which improves the sensitivity of the
`receiver. The amplifier gain of said low noise amplifier 16 is
`selected in view of actual requirements. A high gain results
`in good sensitivity, and low gain is desirable to achieve a
`good dynamic range and proper intermodulation character-
`
`SONY EXHIBIT 1011 - 0003
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`SONY EXHIBIT 1011 - 0003
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`

`

`3
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`4
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`5,530,929
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`istics. An output of said low noise amplifier 16 is divided
`into two different parts, namely an I-channel and a Q-chan-
`nel.
`
`Each of the I-channel and Q-channel is connected to a
`mixer 11, 11'. The mixer forms an essential part of the direct
`conversion receiver. It converts the high frequency input
`signal to base band where it is easier to amplify and filter the
`signal with low-pass filters 17, 17' and amplifiers 18, 18'.
`The mixer, 11, 11' can be passive or active, and the choice
`between the two depends mostly on the intended applica-
`tion. Passive mixers have good large signal performance and
`a high third order intercept point but suffer from high
`conversion losses and the need of a strong local oscillator
`signal. Therefore, such mixers are avoided in battery pow-
`ered equipment. An active mixer has a high conversion gain,
`can be driven by a low power local oscillator but instead has
`a lower third order intercept point and a slightly poorer noise
`figure than the passive mixer. In a preferred embodiment an
`active mixer is used because of the demands for lower power
`consumption.
`As mentioned above a quadrature modulation scheme is
`preferred according to the present invention. To achieve a
`quadrature signal mainly two different ways to do it are
`available. The first is to simply shift the phase of one or both
`of the I and Q oscillator signals, that is to shift one signal 90°
`or one +45° and the other —45°. The second method is to use
`
`that is two
`an oscillator that outputs a balanced signal,
`signals one of which is 180° shifted in phase from the other.
`These signals are then divided by two in the chain between
`the local oscillator and the mixers. A half wave length at
`twice the frequency equals a quarter of a wave length or 90°
`at the desired frequency, and thus the quadrature signal is
`generated automatically. According to the present invention
`the local oscillator operates at a frequency different from the
`wanted signal or the received signal. Referring to FIG. 2, the
`L0 is connected to a first processing unit 13 which multi-
`plies the frequency of the local oscillator by a factor M. M
`should be an integer, and preferably is M23. An output of
`said first processing unit 13 is operatively connected to a
`second processing unit 14 in which an input signal is divided
`by a factor N. M and N are both integer numbers, and
`furthermore M¢N. Preferably is N22. FIG. 2 shows that two
`mixers 11 and 11' are provided, and a phase shift network 19
`is operatively connected to said mixers. A first mixer 11
`receives the input signal amplified in said amplifier 16 and
`the output signal of said second processing unit 14, and
`produces a signal I. The second mixer 11' receives also the
`output signal of said amplifier 16 and the output signal from
`said second processing unit 14 phase shifted 90°, and
`produces a signal Q. However, when N=2 it could be more
`appropriate to phase shift
`the output signal within said
`second processing unit 14.
`Output signals I and Q from mixers 11 and 11' are
`supplied to low pass filters 17, 17' of conventional type and
`then further amplified in conventional amplifiers 18 and 18'.
`According to the invention it is not necessary to utilize
`quadrature signals or the quadrature modulation scheme. In
`such embodiments the phase shift network 19 is omitted and
`so are all units denoted by a prime sign.
`A main feature of the invention is that signals having a
`frequency that could cause spurious emissions are not fed
`through wires such as bonding wires, microstrip, strip lines,
`coax lines, etc. Therefore, at least said second processing
`unit 14 should be integrated with said mixers 11, 11'. The
`integration can be made as an integration in one chip
`(indicated by the dotted lines in FIG. 2) but also other types
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`of integration having the same characteristics of low emis-
`sion of electromagnetic signals can be used. In some appli-
`cations it would be appropriate to integrate also said first
`processing unit 13 together with said mixers 11, 11‘ and said
`first processing unit 14.
`Different combinations of M and N are possible. Prefer-
`ably, N and M are chosen so as to keep the operating
`frequency of said L0 as low as possible to avoid unneces-
`sary power losses. As stated above N is preferably 2, and M
`is preferably 3 but also the opposite could be an appropriate
`choice.
`
`The receiver according to the invention obviously can be
`used also in wired systems and is not restricted to radio
`communication systems. In a wired system the antenna 12 is
`replaced by an input circuit or other reception means appli—
`cable in such a system.
`What is claimed is:
`
`1. A method in a homodyne receiver including a local
`oscillator generating an oscillator signal at a frequency of
`fLo, a mixer, and reception means for receiving an input
`signal having a frequency of fRF, the oscillator signal and the
`input signal being supplied to the mixer, comprising the
`steps of:
`(a) supplying the oscillator signal to a first processing unit
`to produce a first output signal having a frequency of
`M*f,_0, where M is an integer value,
`(b) supplying the first output signal to a second processing
`unit to produce a second output signal having a fre-
`quency of M*fL0/N=fRF, where N is an integer number
`and M¢N, and
`
`(c) integrating the mixer and the second processing unit to
`minimize leakage of signals being supplied to the mixer
`from the second processing unit.
`2. The method of claim 1, wherein the oscillator signal is
`a balanced output signal, including a first oscillator signal
`and a second oscillator signal, the second oscillator signal
`being shifted 180° from the first oscillator signal.
`3. The method of claim 1, further comprising the steps of:
`phase shifting the second output signal by substantially
`90° to produce a phase shifted signal, and
`supplying the second output signal to the mixer and the
`phase shifted signal to a second mixer to obtain quadra-
`ture signals.
`4. A device in a homodyne receiver including a local
`oscillator for generating an oscillator signal at a frequency of
`fLo, a mixer, and reception means for receiving an input
`signal having a frequency of fRF,
`the oscillator and the
`reception means being operatively connected to the mixer,
`comprising:
`a first processing unit operatively connected to the local
`oscillator for producing a first output signal having a
`frequency of M*fw, where M is an integer value, and
`a second processing unit operatively connected to the first
`processing unit for producing a second output signal
`having a frequency of M*f,_0/N=fRF, where N is an
`integer number and M¢N,
`wherein the mixer and the second processing unit are
`integrated to minimize leakage of signals supplied to
`the mixer from the second processing unit.
`5. The device of claim 4, wherein the first processing unit
`is a multiplier and the second processing unit is a divider
`circuit.
`
`SONY EXHIBIT 1011 - 0004
`
`SONY EXHIBIT 1011 - 0004
`
`