Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
  • H03L7/00—Automatic control of frequency or phase; Synchronisation
  • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
  • H03L7/16—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop
  • H03L7/22—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using more than one loop
  • H03L7/23—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using more than one loop with pulse counters or frequency dividers
  • H03L7/235—Nested phase locked loops
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
  • H03L7/00—Automatic control of frequency or phase; Synchronisation
  • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
  • H03L7/00—Automatic control of frequency or phase; Synchronisation
  • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
  • H03L7/16—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop
  • H03L7/18—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop
  • H03L7/183—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop a time difference being used for locking the loop, the counter counting between fixed numbers or the frequency divider dividing by a fixed number
  • H03L7/193—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop a time difference being used for locking the loop, the counter counting between fixed numbers or the frequency divider dividing by a fixed number the frequency divider/counter comprising a commutable pre-divider, e.g. a two modulus divider

Definitions

• Multichannel radio device a radio communication system, and a fractional division frequency synthesizer
• the present invention relates to a multichannel radio device.
• a multichannel radio device can be a radio communication device such as a cellular or a cordless telephone, a pager, or any other suitable multichannel radio device.
• the present invention further relates to a radio communication system and a fractional division frequency synthesizer.
• RF (Radio Frequency) frequency synthesizers are used in multichannel radio devices used in radio communication systems, for instance.
• multichannel receivers or transceivers including rf frequency synthesizers, are used which can tune to a multiple of frequency channels.
• Such a tuning should be fast because the radio device should be able to switch quickly from one radio channel to another.
• the radio devices should cause as little adjacent channel interference as possible.
• high demands should be posed upon the frequency synthesizer used in such radio device as to spectrum purity of its output signal and as to its settling time.
• Frequency synthesizers are known having a structure of a frequency multiplier such as described in the handbook "The Art of Electronics", P. Horowitz et al.
• an output signal from a VCO Voltage Controlled Oscillator
• a integer division ratio divider divides the output signal and an output of the divider is fed back to a phase detector to which also the reference signal is fed.
• a loop filter filters the output of the phase detector and the low pass filtered signal controls the VCO.
• Such a loop is basically a PLL with an integer divider in the feedback path.
• the reference frequency is chosen equal to the channel spacing.
• a pulse remover removes pulses fed back from the VCO to the frequency divider at regular intervals when the output of the phase detector has reached a given value.
• division by N is alternated with division by N+ l.
• Such an alternate division causes undesired sidebands in the output signal of the synthesizer.
• a signal is generated which is subtracted from the output signal of the phase detector it is tried to cancel the undesired sidebands.
• the undesired phase noise is still considerably higher than with ordinary integer division frequency synthesizers. Furthermore, usually external adjustments are needed so as to compensate for residual effects. Because high-speed circuits are required in both types of fractional-N synthesizers, power consumption is considerable, notably in the digital circuits such as the digital-to-analog converter and the Sigma-Delta modulator. Such a relatively high power consumption is particularly undesired in portable phones where it is desired to have as long as possible standby and call times before the battery is exhausted. High complexity also leads to a larger chip area which is undesired from a cost point of view and the desire to have a high degree of integration. It is an object of the present invention to provide a radio communication device including a fractional division frequency synthesizer having a high performance without the drawbacks of the known fractional-N frequency synthesizer while having a simple structure.
• a fractional division frequency synthesizer particularly when included in a multichannel radio device, which synthesizer has an output signal at an output of the synthesizer having a frequency being a fractional multiple of a reference frequency generated by a reference frequency generator, which synthesizer comprises a forward path between the reference and said output including a cascade of a first phase detector, a first loop filter and a first voltage controlled oscillator, whereby a first input of the first phase detector is coupled to the reference, which synthesizer further composes a feedback path between said output and a second input of the first phase detector including a cascade of a first frequency divider, a second phase detector, a second loop filter and a second voltage controlled oscillator, whereby an output of second voltage controlled oscillator is coupled to the second input of the first phase detector and an output of the first frequency divider is coupled to a first input of the second phase detector, and which synthesizer comp ⁇ ses a second frequency divider of which an input is coupled to the
• the present mvenuon is based upon the insight that despite applying an extremely simple structure still solely integer dividers could be used to obtain a fractional-N synthesizer.
• Such a surprisingly totally different concept of a fractional-N frequency synthesizer has the advantage that the phase noise is as low as the phase noise of an ordinarv integer divide by N synthesizer.
• the auxiliary PLL is exactly dividing by M/N, M being the integer divisor of the first frequency divider and N being the integer divisor of the second frequency divider, no undesired spu ⁇ ous frequencies are generated.
• the second voltage controlled oscillator can easily be integrated on an IC (Integrated Circuit). Because of the extremely simple structure, low power consumption is obtained, and further a small chip area and a low cost design and development When using BiCMOS or short-channel CMOS technologies, the complete synthesizer can be easily be integrated on an integrated circuit
• any output frequency can be synthesized which is a fractional multiple of the input reference frequency
• Fig. 1 schematically shows a radio communication system with multichannel radio devices according to the present invention
• Fig. 2 shows a block diagram of a fractional division frequenc ⁇ 99/08384
• Fig. 1 schematically shows a radio communication system 1 with multichannel radio devices 2 and 3 according to the present invention.
• a system can be a cellular radio system such as a GSM (FD/TDMA system), a CDMA system with frequency channels in conjunction to code division, a cordless telephone system like a DECT system, a paging system like a FLEXTM system, or any other suitable multichannel radio system.
• the system further comprises a radio base station 4 which can communicate with the radio device 2 and 3.
• a radio base station 4 can be a radio base station in a GSM network, for instance.
• the radio device 2 comprises an rf-receiver branch 5 and an rf-transmit branch 6 both coupled to an antenna 7 via a duplexer or transmit/receive switch 8.
• the receive branch 5 comprises frequency down conversion means in the form of a mixer 9 and a frequency synthesizer 10, which can be a fractional division frequency synthesizer according to the present invention.
• the receive path 5 further comprises a low noise rf-amplifier 11 coupled to a receive filter 12.
• the synthesizer 10 provides a local oscillator frequency f L0 to an input of the mixer 9. An output of the mixer 9 is fed to a further mixer stage or to a modulator (not shown in detail here).
• the transmit path 6 comprises a mixer 13 out which an input is coupled to an rf-power amplifier 14 which is coupled to the duplexer 8 via a transmit filter 15.
• a frequency synthesizer 16 provides a carrier frequency f c to the mixer 16.
• Data to be transmitted is supplied to an input of the mixer 13.
• the radio device 2 comprises a microcontroller 17 which is programmed to submit adjustment data to the synthesizers 10 and 16 so as to adjust their frequencies.
• the radio device 3 comprises a mixer 20, a power amplifier 21, a transmit filter 22, a duplexer 23, an antenna 24, a low noise amplifier 25, a receive filter 26, a mixer 27 and a synthesizer 28.
• Fig. 2 shows a block diagram of the fractional division frequency synthesizer 10 according to the present invention.
• the synthesizer 10 has an output 30 at which an output signal having an output frequency f 0 arises and an input 31 to which a reference signal is fed having a reference frequency f ref .
• the reference f ref is generated by a reference generator (not shown in detail) such as a crystal or quartz oscillator.
• the output frequency f 0 is a fractional multiple of the reference frequency f ref .
• the fractional division frequency synthesizer 10 comprises a forward path between the input 31 and the output 32 including a cascade of a first phase detector PD, , a first loop filter LF, , usually a low pass filter, and a first voltage controlled oscillator VCO, .
• a first input 32 of the first phase detector PD is coupled to the input 31.
• the synthesizer 10 further a feedback path between the output 30 and a second input 33 of the first phase detector PD 2 including a cascade of a first frequency divider 34 having an integer division ratio M, a second phase detector PD 2 , a second loop filter 2 , usually a low pass filter, and a second voltage controlled oscillator VCO 2 .
• the oscillator VCO 2 is coupled to the second input 33 of the first phase detector PD j .
• An output 35 of the first frequency divider 34 is coupled to a first input 36 of the second phase detector PD 2 .
• the synthesizer 10 further comprises a second frequency divider 37 having an integer division ratio N, of which an input 38 is coupled to the second input 33 of the first phase detector PD j and of which an output 39 is coupled to a second input 40 of the second phase detector PD 2 .
• the frequency dividers 34 and 37 are so-called dual-modulus prescalers, well-known in the art.
• the divider 34 comprises counter P/P+ l whose division ratio can be switched from P to P+ l and vice versa by a control signal ctl, a programmable down counter Q, and a programmable down counter R.
• the programmable down counters Q and R are presentable. If a down counter has counted down from its preset value to zero, the output of the counter changes from one logic value to another logic value, e.g, from logic HIGH to logic LOW while at the same time the counter is loaded with its preset value.
• the microcontroller 17 can change the preset values so that any value for Q and R can be set.
• the frequency divider or prescaler 37 comprises a counter S/S + l, a programmable down counter T, and a programmable down counter U.
• the frequency dividers can also be implemented as a 4-modulus prescaler, or any other suitable type of frequency divider.
• f 0 (Q.P + R)/(T.S + U).f ref .

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• Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
• Transceivers (AREA)

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• 1998
  • 1998-07-16 WO PCT/IB1998/001081 patent/WO1999008384A2/en not_active Application Discontinuation
  • 1998-07-16 JP JP11511896A patent/JP2001502157A/ja active Pending
  • 1998-07-16 CN CN98801515A patent/CN1241325A/zh active Pending
  • 1998-07-16 KR KR1019997003082A patent/KR20000068744A/ko not_active Application Discontinuation
  • 1998-07-16 EP EP98929594A patent/EP0943180A1/de not_active Withdrawn

Non-Patent Citations (1)

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