Multistage modulation architecture and method in a radio
View Patent ↗In a multiple stage transmitter, and analog signal is modulated and mixed to produce a radio frequency output. A separate mixing frequency signal is provided to each stage. A single frequency synthesizer is used rather than a plurality of frequency synthesizers. In a two-stage system, first and second dividers each receive the output of the frequency synthesizer and deliver a mixing signal to the first and second stages respectively. The modulus of each divider may be selected to minimize spurious signals.
1. In a double conversion transmitter transmitting a radio frequency signal in response to an analog signal input and comprising a modulator having both in-phase and quadrature channels including a first mixer in each channel and providing an intermediate frequency output and a second mixer providing a radio frequency output, said mixers being supplied with first and second mixing signals respectively and mixing signal means for providing said first and second mixing signals, the improvement wherein said mixing signal means comprises:
a first frequency divider and a second frequency divider having outputs connected to the mixers in each channel of said first mixer and said second mixer respectively, each of said first and second frequency dividers having a respective, selected and different modulus for dividing an input to the frequency divider by the respective modulus; and
a frequency synthesizer providing a signal at a local oscillator frequency to the inputs of said first and second frequency dividers;
the modulus of the first and second frequency dividers are related by the expression:
f RF =[( M 1 +M 2)/( M 1* M 2)]* f VCO
where f RF is the frequency of the radio frequency signal, M1 and M2 are the first and second moduli respectively and f VCO is the output frequency of the frequency synthesizer.
2. The transmitter according to claim 1 wherein M1 is a multiple of 4 .
3. The transmitter according to claim 2 where M2=M1±N where N is a positive integer.
4. A double conversion transmitter transmitting a radio frequency signal in response to an analog signal input and comprising a modulator having both inphase and quadrature channels including a first mixer having a mixer in each channel and providing an intermediate frequency output and a second mixer providing a radio frequency output, said mixers being supplied with first and second mixing signals respectively, a frequency synthesizer providing a signal at a local oscillator frequency, first and second frequency dividers each constructed with a different modulus and each receiving an input from said frequency synthesizer at the local oscillator frequency and coupled for providing said first and second mixing signals to the mixer in each channel of said first mixer and said second mixer respectively, each at a frequency equal to the local oscillator frequency divided by a respective modulus, the modulus of the first and second frequency dividers being related by the expression:
f RF =[( M 1 +M 2)/( M 1* M 2)]* f VCO
where f RF is the frequency of the radio frequency signal, M1 and M2 are the first and second moduli respectively and f VCO is the frequency of the frequency synthesizer.
5. The transmitter according to claim 4 wherein M1 is a multiple of 4.
6. The transmitter according to claim 5 where M2=M1±N where N is a positive integer.
7. In a method for translation an analog signal to a radio frequency signal comprising modulating inphase and qaudrature components of an analog signal and mixing each said component of the analog signal with a first mixing frequency signal to provide a first intermediate frequency signal and mixing said first intermediate frequency signal with a second mixing frequency signal to provide a radio frequency output, the improvement comprising:
providing one frequency synthesizer as a source for said first and second mixing frequency signals; and
dividing the output of said frequency synthesizer by first and second moduli to produce said first and second mixing frequencies, the moduli in the division being related by the expression:
f RF =[( M 1 +M 2)/( M 1 *M 2)]* f VCO
where f RF is the frequency of the radio frequency signal, M1 and M2 are the first and second moduli respectively and f VCO is the frequency of the frequency synthesizer.
8. The method of claim 7 wherein the step of dividing comprises utilizing an M1 which is a multiple of 4.
9. The method of claim 8 wherein the step of dividing comprises utilizing moduli where M2=M1±N where N is an integer.
10. In a double conversion transmitter transmitting a radio frequency signal in response to an analog signal input and comprising a modulator including a first mixer providing an intermediate frequency output and a second mixer providing a radio frequency output, said mixers being supplied with first and second mixing signals respectively and mixing signal means for providing said first and second mixing signals, the improvement wherein said mixing signal means comprises:
a first frequency divider and a second frequency divider connected to said first mixer and said second mixer respectively, each of said first and second frequency dividers having a respective, selected modulus; and a frequency synthesizer providing a signal at a local oscillator frequency to said first and second frequency dividers, wherein said modulator comprises both in-phase and quadrature channels and said first mixer comprises a mixer in each said channel and wherein said first frequency divider provides an input to said mixer to each said channel, said first and second frequency dividers are each constructed with a different modulus, and the modulus of the first and second frequency dividers are related by the expression:
f RF =[( M 1 +M 2)/( M 1 *M 2)]* f VCO
where f RF is the frequency of the radio frequency signal, M1 and M2 are the first and second moduli respectively and f VCO is the output frequency of the frequency synthesizer.
11. The transmitter according to claim 10 wherein M1 is a multiple of 4.
12. The transmitter according to claim 11 where M2=M1±N, where N is a positive integer.
13. A double conversion transmitter transmitting a radio frequency signal in response to an analog signal input and comprising a modulator including a first mixer providing an intermediate frequency output and a second mixer providing a radio frequency output, said mixers being supplied with first and second mixing signals respectively, a frequency synthesizer providing a signal at a local oscillator frequency, first and second frequency dividers each receiving an input from said frequency synthesizer and coupled for providing said first and second mixing signals to said first mixer and said second mixer respectively, wherein said modulator comprises both in-phase and quadrature channels and said first mixer comprises a mixer in each said channel and wherein said first frequency divider provides an input to said mixer to each said channel, said first and second frequency dividers are each constructed with a different modulus, and the modulus of the first and second frequency dividers are related by the expression:
f RF =[( M 1 +M 2)/( M 1 *M 2)]* f VCO
where f RF is the frequency of the radio frequency signal, M1 and M2 are the first and second moduli respectively and f VCO is the output frequency of the frequency synthesizer.
14. The transmitter according to claim 13 wherein M1 is a multiple of 4.
15. The transmitter according to claim 14 where M2=M1±N, where N is a positive integer.
16. In a method for translation an analog signal to a radio frequency signal comprising the steps of modulating an analog signal and mixing the analog signal with a first mixing frequency signal to provide a first intermediate frequency signal and mixing said first intermediate frequency signal with a second mixing frequency signal to provide a radio frequency output, the improvement comprising: providing a one frequency synthesizer as a source for said first and second mixing frequency signals; and dividing the output of said frequency synthesizer by first and second divisors to produce said first and second mixing frequencies, wherein said modulator comprises both in-phase and quadrature channels and said first mixer comprises a mixer in each said channel and wherein said first frequency divider provides an input to said mixer to each said channel, the step of dividing comprises utilizing first and second moduli to produce said first and second mixing frequencies, and the modulus of the first and second frequency dividers are related by the expression:
f RF =[( M 1 +M 2)/( M 1* M 2)]* f VCO
where f RF is the frequency of the radio frequency signal, M1 and M2 are the first and second moduli respectively and f VCO is the output frequency of the frequency synthesizer.
17. The transmitter according to claim 16 wherein M1 is a multiple of 4.
18. The transmitter according to claim 17 where M2=M1±N, where N is a positive integer.