Signal generating system and signal generating method

This application claims the benefit of U.S. Provisional Application No. 62/068,777, filed on Oct. 27, 2014, the contents of which are incorporated herein by reference.

Quadrature signals with accurate duty cycles are always necessary for a circuit. For example, quadrature signals with accurate duty cycles are beneficial for coverage of an oscillator or for frequency planning.

Quadrature signals are commonly used but a conventional signal generating system only uses even-number dividers in order to generate the quadrature signals. Due to the limitation of divider ratio, it is not good for coverage of an oscillator or for frequency planning.

For example, if the signal generating system has 3 level triggering devices, the signal generating system can only generate the frequency divided signal having a phase of 180/3*N. N is a positive integer. For another example, if the signal generating system has 5 level triggering devices, the signal generating system can only generate the frequency divided signal having a phase of 180/5*N. Also, at least one adjusting step is needed to generate desired quadrature signals. However, such adjusting may cause more noises.

Accordingly, a new signal generating system and a new signal generating method are needed.

Therefore, one objective of the present application is to provide a signal generating system which can generate an output signal with a quadrature phase and odd-number divider ratio via a frequency dividing module, a frequency doubler with 50% duty-cycle outputs and an IQ divider.

Another objective of the present application is to provide a signal generating system which adjusts the duty cycle before the signal is frequency divided to generate I/Q signals.

One embodiment of the present application discloses a signal generating system for generating an output signal with a 50% duty cycle. The signal generating system comprises: a frequency dividing module, comprising an odd number of level triggering devices, for generating a plurality of frequency divided signals utilizing a frequency dividing ratio equaling to M, wherein the M is an positive integer; and a signal combining module, for combining at least two of the frequency divided signals to generate at least one output combined signal. The signal generating system generates the output signal based on the output combined signal. The frequency dividing module cooperates the signal combining module to provide a frequency dividing ratio equaling to N.5, wherein the N is a positive integer.

In one embodiment, N.5=M/2. Also, in one embodiment, the output combined signal is generated by one frequency divided signal and one input clock of the frequency divider module.

Another embodiment of the present application discloses a signal generating system for generating an output signal with a 50% duty cycle. The signal generating system comprises: a frequency dividing module, comprising an odd number of level triggering devices, for generating a plurality of frequency divided signals utilizing a frequency dividing ratio equaling to M, wherein the M is an positive integer; a delay module, for delaying at least one of the frequency divided signal to generated at least one delayed frequency divided signal; and a signal combining module, for combining at least one of the delayed frequency divided signals, or for combining at least one the frequency divided signal and at least one the delayed frequency divided signal, to generate the output signal. The frequency dividing module cooperates the signal combining module to provide a frequency dividing ratio equaling to N.5, wherein the N is a positive integer.

Signal generating methods can be acquired based on above-mentioned embodiments. The steps thereof are omitted for brevity here.

Another embodiment of the present application discloses a duty cycle calibrating circuit, which comprises: a first falling time tuning circuit, for receiving an input signal to generate a first adjusted input signal; and a buffer, for buffering the first adjusted input signal to generate a calibrated signal.

Another embodiment of the present application discloses a duty cycle calibrating circuit, which comprises: a seventh inverter, for receiving an input signal; a second falling time tuning circuit, for receiving output from the seventh inverter to generate a second adjusted input signal; and an eighth inverter, for inverting the second adjusted input signal to generate a calibrated signal.

Another embodiment of the present application discloses a signal combining module, which comprises: a first initial combining circuit, for receiving a plurality of input signals to generate a first output combined signal; a second initial combining circuit, for receiving a plurality of input signals to generate a second output combined signal; a first edge calibrating device, coupled between a first voltage level and the first initial combining circuit; and a second edge calibrating device, coupled between a second voltage level and the second initial combining circuit. The first edge calibrating device and the second edge calibrating device calibrate an edge of the first output combined signal and the second output combined signal to generate an output combined signal at an output terminal.

Another embodiment of the present application discloses a signal combining module, which comprises: an energy storing circuit, coupled to the output terminal; a charging circuit, for receiving at least two input signals to output a charging current to the energy storing circuit; a discharging circuit, for receiving at least two of the frequency divided signals to drain a discharging current from the energy storing circuit. The energy storing circuit generates an output combined signal according to the charging current and the discharging current to the output terminal.

In view of above-mentioned embodiments, an output signal with a quadrature phase and odd-number divider ratio can be generated via a frequency dividing module, a frequency doubler with 50% duty-cycle outputs and an IQ divider. Also, the quadrature phase is adjusted by calibrating the duty cycle of the input signal of the IQ divider, thus the noise can be reduced and phase performance is better.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

FIG. 1 is a block diagram illustrating a signal generating system according to one embodiment of the present application.

FIG. 2A is a block diagram illustrating a signal generating system according to another embodiment of the present application.

FIG. 2B is a wave chart illustrating the operation for the signal generating system depicted in FIG. 2A .

FIG. 3 is a circuit diagram illustrating the circuit for the frequency dividing module described in FIG. 1 , according to one embodiment of the present application.

FIG. 4 is a wave chart illustrating the operation for the circuit shown in FIG. 3 .

FIG. 5 is a circuit diagram illustrating the circuit for the frequency dividing module described in FIG. 1 , according to another embodiment of the present application.

FIG. 6 is a wave chart illustrating the operation for the circuit shown in FIG. 5 .

FIG. 7 is a circuit diagram illustrating the circuit for the frequency dividing module described in FIG. 1 , according to still another embodiment of the present application.

FIG. 8A is a circuit diagram illustrating the duty cycle calibrating circuit in FIG. 2 , according to one embodiment of the present application.

FIG. 8B is a block diagram illustrating that the signal generating system comprises a calibrating circuit, which comprises the comparator and the average computing circuit depicted in FIG. 8A .

FIG. 9A, 9B are circuit diagram illustrating the first duty cycle calibrating module and the second duty cycle calibrating module in FIG. 8A , according to one embodiment of the present application.

FIG. 10A , FIG. 10B , FIG. 10C , FIG. 10D are block diagrams illustrating the duty cycle calibrating circuits according to one embodiment of the present application.

FIG. 11 is a circuit diagram illustrating a circuit for the signal combining module described in FIG. 1 , according to one embodiment of the present application.

FIG. 12 and FIG. 13 are examples for the operation of the circuit described in FIG. 11 .

FIG. 14 is a wave chart illustrating the operation for the embodiments of FIG. 12 .

FIG. 15 is a circuit diagram illustrating a circuit for the signal combining module described in FIG. 2 , according to another embodiment of the present application.

FIG. 16 is an example for the operation of the circuit described in FIG. 15 .

FIG. 17 is a wave chart illustrating the operation of the embodiment described in FIG. 16 .

FIG. 18 is an example for the operation of the circuit described in FIG. 15 .

FIG. 19 is a wave chart illustrating the operation of the embodiment described in FIG. 18 .

FIG. 20 is a circuit diagram illustrating an XOR circuit applied to the signal combining module of the present application.

FIG. 21 is a wave chart illustrating the operation for the XOR circuit depicted in FIG. 20 .

FIG. 1 is a block diagram illustrating a signal generating system 100 for generating an output signal OS with 50% duty cycle according to one embodiment of the present application. As shown in FIG. 1 , the signal generating system 100 comprises a frequency dividing module 101 , and a signal combining module 103 . The frequency dividing module 101 comprises an odd number of level triggering devices, generates a plurality of frequency divided signals Q_ 1 -Q_M utilizing a frequency dividing ratio equaling to M based on the input signal INS, wherein the M is a positive integer. That is, M can be 1, or any other positive integer other than 1. The signal combining module 103 combines at least two of the frequency divided signals Q_ 1 -Q_M to generate an output combined signal CS. In one embodiment, the frequency divided signals Q_ 1 -Q_M have a 50% duty cycle, but frequencies thereof are not desired frequencies. Alternatively, the signal combining module 103 can combine one of the frequency divided signals Q_ 1 -Q_M and the input signal INS to generate the output combined signal CS. The frequency dividing module 101 cooperates with the signal combining module 103 to provide a frequency dividing ratio equaling to N.5, wherein the N is a positive integer. That is, N can be 1, or any other positive integer other than 1. One objective of the present application is to provide an output signal OS with a 50% duty cycle and a desired frequency. Accordingly, if the output combined signal CS already has a 50% duty cycle, the output combined signal CS can directly be output as the output signal OS. Alternatively, the signal generating system 100 can further comprise a duty cycle calibrating circuit 105 for calibrating the output combined signal CS to generate the output signal OS. In one embodiment, the frequency divided signals Q_ 1 -Q_M can be combined and then further processed to generate the output combined signal CS, but not limited.

The detail explaining of the frequency dividing module 101 , the signal combining module 103 and the duty cycle calibrating circuit 105 will be discussed later.

FIG. 2A is a block diagram illustrating a signal generating system 200 for generating an output signal OS with 50% duty cycle according to another embodiment of the present application. The signal generating system 200 comprises a frequency dividing module 201 , a signal combining module 203 , and a delay module 205 . Comparing with the embodiment illustrated in FIG. 1 , the signal combining module 103 is provided prior to the duty cycle calibrating circuit 105 , but the signal combining module 203 is provided after the delay module 205 . Accordingly, at least one of the frequency divided signals Q_ 1 -Q_M is delayed by the delay module 205 to generate at least one delayed frequency divided signal (Q_ 2 ′ in this example). In such example, the frequency divided signals Q_ 1 has a 50% duty cycle, and the delayed frequency divided signal Q_ 2 ′ has a 50% duty cycle as well. Afterwards, the delayed frequency divided signal and the frequency divided signal (or another delayed frequency divided signal) are combined by the signal combining module 203 to generate the output signal OS. After processed by the signal generating system 200 , the output signal OS can have a duty cycle for 50% and a desired frequency.

FIG. 2B is a wave chart illustrating the operation for the signal generating system depicted in FIG. 2A . As illustrated in FIG. 2B , the frequency divided signal Q_ 2 is delayed by the delay module 205 to generate the delayed frequency divided signal Q_ 2 ′, and then the frequency divided signal Q_ 1 and the delayed frequency divided signal Q_ 2 ′ are combined by the signal combining module 203 to generate the output signal OS (Q_ 1 ⊕Q_ 2 ′).

In one embodiment, the output signal OS can be frequency divided by a frequency dividing ratio 2 , but not limited. In such case, the embodiments in FIG. 1 and FIG. 2 form an I/Q divider.

FIG. 3 is a circuit diagram illustrating the circuit for the frequency dividing module 101 described in FIG. 1 , according to one embodiment of the present application. In the embodiment of FIG. 3 , the frequency dividing module 101 comprises three level triggering devices TD_ 1 , TD_ 2 and TD_ 3 , which respectively outputs the frequency-divided signals Q_ 1 , Q_ 2 and Q_ 3 . The level triggering devices TD_ 1 , TD_ 2 and TD_ 3 can be triggered by either the rising edge or the falling edge of the clock signal CLK based on the level of D and D , to generate the frequency-divided signals Q_ 1 , Q_ 2 and Q_ 3 , thus the level triggering devices TD_ 1 , TD_ 2 and TD_ 3 receive both the clock signal CLK and an inverted clock signal CLK , which has inverted phase of the clock signal CLK. The operation for the level triggering devices TD_ 1 , TD_ 2 and TD_ 3 can be illustrated as the following table T 1 . However, please note the level triggering devices TD_ 1 , TD_ 2 and TD_ 3 illustrated in FIG. 3 are only example. Other devices can be applied to perform the function of the frequency dividing module. In one embodiment, the input signal INS in FIG. 1 or FIG. 2 is the clock signal CLK or the inverted clock signal CLK .

FIG. 4 is a wave chart illustrating the operation for the circuit shown in FIG. 3 . In one embodiment, the signal combining module 103 in FIG. 1 comprises at least one XOR circuit. Therefore, if an XOR operation is performed to the frequency-divided signals Q_ 1 , Q_ 2 , an output combined signal Q_ 1 ⊕Q_ 2 is acquired (i.e. CS in FIG. 1 ). Also, if an XOR operation is performed to the frequency-divided signals Q_ 1 , Q_ 3 , an output combined signal Q_ 1 ⊕Q_ 3 (i.e. CS in FIG. 1 ) is acquired. In this case, the duty cycle for the output combined signal Q_ 1 ⊕Q_ 2 is 33%, and the duty cycle for the output combined signal Q_ 1 ⊕Q_ 3 is 66%. Accordingly, the output combined signals Q_ 1 ⊕Q_ 2 and Q_ 1 ⊕Q_ 3 are calibrated by the duty cycle calibrating circuit 105 to generate the output signal OS.

FIG. 5 is a circuit diagram illustrating the circuit for the frequency dividing module 101 described in FIG. 1 , according to another embodiment of the present application. In this embodiment, the frequency dividing module 101 comprises five level triggering devices rather than three level triggering devices described in FIG. 3 . For more detail, the frequency dividing module 101 comprises five level triggering devices TD_ 1 -TD_ 5 , which respectively outputs the frequency-divided signals Q_ 1 -Q_ 5 .

FIG. 6 is a wave chart illustrating the operation for the circuit shown in FIG. 5 . As above-mentioned, in one embodiment, the signal combining module 103 in FIG. 1 comprises at least one XOR circuit. Therefore, the output combined signals Q_ 1 ⊕Q_ 3 , Q_ 1 ⊕Q_ 4 , Q_ 1 ⊕Q_ 2 , and Q_ 1 ⊕Q_ 5 can be acquired. Please note, any two of the frequency divided signals can be selected to generate the output signal.

In view of the embodiments of FIG. 3 and FIG. 5 , the frequency dividing module 101 can comprise any odd number of level triggering devices. FIG. 7 is a circuit diagram illustrating the circuit for the frequency dividing module 101 described in FIG. 1 , according to still another embodiment of the present application. As shown in FIG. 7 , the frequency dividing module 101 , which has a frequency dividing ratio of M, comprises M level triggering devices Q_ 1 -Q_M, wherein M equals to 2*(N.5). Therefore, the frequency dividing module 101 in FIG. 7 can generate M frequency divided signals Q_ 1 -Q_M.

FIG. 8A is a circuit diagram illustrating the duty cycle calibrating circuit 105 in FIG. 1 , according to one embodiment of the present application. As shown in FIG. 8A , the duty cycle calibrating circuit 105 comprises a comparator 801 , a first duty cycle calibrating module 803 and a second duty cycle calibrating module 805 . The comparator 801 compares a duty cycle for the output signal OS and a duty cycle for an inverted output signal OS , to generate a comparing result. In one embodiment, the comparator 801 compares an average voltage signal AOS and an average voltage signal A OS to generate the comparing result, but not limited. The average voltage signal AOS indicates the average voltage of the output signal OS, which is the DC voltage level of the output signal OS, and the average voltage signal A OS indicates the average voltage of the inverted output signal OS , which is the DC voltage level of the inverted output signal OS . The DC voltage level can be acquired via filtering the output signal OS and the inverted output signal OS . The average voltage signal AOS and the average voltage signal A OS can be acquired by an average computing circuit 807 as shown in FIG. 8A , but not limited. The first duty cycle calibrating module 803 calibrates an edge of the output signal OS according to the comparing result. The second duty cycle calibrating module 805 calibrates an edge for the inverted output signal OS according to the comparing result. Please note in this embodiment the duty cycle calibrating circuit 105 comprises two duty cycle calibrating modules since the duty cycle calibrating circuit 105 is designed to generate a differential signal as the output signal.

As above-mentioned the delay module 205 can further comprise a function of calibrating the duty cycle. In such case, the delay module 205 comprises a circuit for delaying and a circuit for calibrating the duty cycle. The circuit for calibrating the duty cycle can be, for example, the structure in FIG. 8A , but also can be a circuit with other structures. The circuit for delaying can comprise various kinds of structures and is well known by persons skilled in the art, thus the description thereof is omitted for brevity here.

In one embodiment the duty cycle calibrating circuit 105 can comprise only one of the duty cycle calibrating modules to generate a single-ended signal as the output signal. In such case, one input terminal of the comparator 801 is coupled to a constant voltage level.

Please note, the duty cycle calibrating circuit 105 is not limited to the structure depicted in FIG. 8A . For example, the comparator 801 can compare the average voltage for one of the output signal OS and the inverted output signal OS with a predetermined voltage level to determine if the output signal OS has a 50% duty cycle. In such case, the output signal is a single-ended signal.

Please refer to FIG. 8B , which illustrates a structure that the signal generating system 200 in FIG. 2A comprises a calibrating circuit 810 , which comprises the comparator 801 and the average computing circuit 807 depicted in FIG. 8A . The calibrating circuit 810 detects if the output signal OS and the inverted output signal OS both have a 50% duty cycle. If not, the calibrating circuit 810 adjusts the delay amount of the delay module 205 . If yes, the calibrating circuit 810 does not adjust the delay amount of the delay module 205 . The operations for the comparator 801 and the average computing circuit 807 depicted in FIG. 8B can be understood according to the description for the comparator 801 and the average computing circuit 807 in FIG. 8A , thus are omitted for brevity here.

FIG. 9A , FIG. 9B , FIG. 10A , FIG. 10B and FIG. 10C are examples of the first duty cycle calibrating module and the second duty cycle calibrating module in FIG. 8A . Please note these examples are only for explaining the operation of the first duty cycle calibrating module and the second duty cycle calibrating module in FIG. 8A . Any circuit that can perform the function of the first duty cycle calibrating module and the second duty cycle calibrating module in FIG. 8A should fall in the scope of the present application. For example, the amount and the arrangement for buffers or inverters can be verified corresponding to different requirements.

FIG. 9A and FIG. 9B are circuit diagrams illustrating the first duty cycle calibrating module and the second duty cycle calibrating module in FIG. 8A , according to one embodiment of the present application. As shown in FIG. 9A and FIG. 9B , the first duty cycle calibrating module 803 comprises: a transistor of second type P, a first transistor of first type N_ 1 , a second transistor of first type N_ 2 , a first inverter IV_ 1 , a second inverter IV_ 2 and a third inverter IV_ 3 . The second duty cycle calibrating module 805 comprises: a transistor of second type P, a first transistor of first type N_ 1 , a second transistor of first type N_ 2 , a fourth inverter IV_ 4 , a fifth inverter IV_ 5 and a sixth inverter IV_ 6 . The transistor of second type P, comprises a first terminal coupled to a first voltage level Vdd, a second terminal and a control terminal. The first transistor of first type N_ 1 comprises a first terminal coupled to the second terminal of the transistor of second type P, a second terminal and a control terminal. The second transistor of first type N_ 2 comprises a first terminal coupled to the second terminal of the first transistor of first type N_ 1 , a second terminal coupled to a second voltage level GND and a control terminal. Please note, in one example, the transistor of first type described in the present application is an NMOSFET, and the transistor of second type in the present application is a PMOSFET, but not limited. Please note the second transistor of first type N_ 2 in FIG. 9A and FIG. 9B can be replaced with a tunable resistor.

In FIG. 9A , the output terminal of the first inverter IV_ 1 is coupled to the control terminals of the transistor of second type P and the first transistor of first type N_ 1 . The input terminal of the second inverter IV_ 2 is coupled to the second terminal of the transistor of second type P. The input terminal of the third inverter IV_ 3 is coupled to an output terminal of the second inverter IV_ 2 .

In FIG. 9B , the output terminal of the fourth inverter IV_ 4 is coupled to an input terminal of the fifth inverter IV_ 5 . The output terminal of the fifth inverter IV_ 5 is coupled to the control terminals of the transistor of second type P and the first transistor of first type N_ 1 . The input terminal of the sixth inverter IV_ 6 is coupled to the second terminal of the transistor of second type P.

The transistor of second type P, the first transistor of first type N_ 1 , the second transistor of first type N_ 2 , and the first inverter IV_ 1 in FIG. 9A can be regarded as a first falling time tuning circuit FTC_ 1 in FIG. 10A . The second inverter IV_ 2 and the third inverter IV_ 3 in FIG. 9A can be regarded as a buffer B in FIG. 10A .

Additionally, the transistor of second type P, the first transistor of first type N_ 1 , the second transistor of first type N_ 2 , and the fifth inverter IV_ 5 in FIG. 9B can be regarded as a second falling time tuning circuit FTC_ 2 in FIG. 10A . The fourth inverter IV_ 4 and the sixth inverter IV_ 6 are respectively the seventh inverter IV_ 7 and the eighth inverter IV_ 8 in FIG. 10A .

Accordingly, the circuits in FIG. 9A and FIG. 9B can be summarized as the block diagram depicted in FIG. 10A . The signal waveform of the circuit 803 , 805 , is illustrated in FIG. 10A . As illustrated in FIG. 10A , the first falling time tuning circuit FTC_ 1 adjusts the falling time of the output combined signal CS to generate a first adjusted output combined signal CSX. The buffer B buffers the adjusted output combined signal CSX to generate the output combined signal OS. The inverted output combined signal CS is inverted by the seventh inverter IV_ 7 and then adjusted by the second falling time tuning circuit FTC_ 2 to generate the second adjusted output combined signal CSY. After that, the second adjusted output combined signal CSY is inverted by the eighth inverter IV_ 8 again to generate the inverted output signal OS .

FIG. 10A also illustrates a wave chart illustrating the operation for the circuit described in FIG. 10A . As shown in FIG. 10A , the output combined signal CS has a 33% duty cycle, such that the inverted output combined signal CS has a 66% duty cycle. After processed by the falling time tuning circuit FTC_ 1 and the buffer B, the falling edge of the output combined signal CS can be delayed, such as the first adjusted output combined signal CSX. The delay level for the falling edge of the output combined signal CS can be adjusted via controlling the resistance of the falling time tuning circuit FTC_ 1 . Similarly, after processed by the falling time tuning circuit FTC_ 2 , the rising edge of the output combined signal CS can be delayed such as the second adjusted output combined signal CSY. The delaying level for the falling edge of the output combined signal CS can be adjusted via controlling the resistance of falling time tuning circuit FTC_ 2 .

Please note the structure of the duty cycle calibrating circuit according to the embodiment of the present application is not limited to the circuits depicted in FIG. 9A , FIG. 9B and FIG. 10A . As illustrated in FIG. 10B , the duty cycle calibrating circuit 903 corresponds the structures of the second duty cycle calibrating module 803 in FIG. 10A to process the output combined signal CS. Also, the duty cycle calibrating circuit 905 corresponds to the structures of the duty cycle calibrating module 805 in FIG. 10A to process the inverted output combined signal CS . Please note the duty cycle calibrating circuits 903 , 905 apply the first rising time tuning circuit RTC_ 1 and the second rising time tuning circuit RTC_ 2 to respectively adjust the inverted output combined signal CS and the inverted signal of the output combined signal CS rather than the first falling time tuning circuit FTC_ 1 and the second falling time tuning circuit FTC_ 2 stated in FIG. 10A .

In the embodiment of FIG. 10C , the duty cycle calibrating circuit 1003 applies the structure of the duty cycle calibrating module 803 in FIG. 10A , and the duty cycle calibrating circuit 1005 applies the structure of the duty cycle calibrating module 905 in FIG. 10B . The operations for the duty cycle calibrating circuits 1003 and 1005 can be acquired based on the description for the duty cycle calibrating module 803 and 905 , thus are omitted for brevity here.

In the embodiment of FIG. 10D , the duty cycle calibrating circuits 1103 and 1105 respectively applies the structure of the duty cycle calibrating module 903 in FIG. 10B and the duty cycle calibrating module 805 in FIG. 10A . That is, the duty cycle calibrating circuits 1103 comprises a seventh inverter IV_ 7 , an eighth inverter IV_ 8 and a second rising time tuning circuit RTC_ 2 . Also, the duty cycle calibrating circuits 1105 comprises a ninth inverter IV_ 9 , a tenth inverter IV_ 10 and a second falling time tuning circuit FTC_ 2 . The operations for the duty cycle calibrating circuits 1103 and 1105 can be acquired based on the description for the duty cycle calibrating module 903 , 805 , thus are omitted for brevity here.

Please note the duty cycle calibrating circuits depicted in the embodiments of FIG. 10A - FIG. 10D are not limited to be applied the signal combining module of the present application. Accordingly, the duty cycle calibrating circuit comprising the structure of the duty cycle calibrating module 803 can be summarized as: a first falling time tuning circuit (ex. FTC_ 1 ), for receiving an input signal to generate a first adjusted input signal; a buffer (ex. B), for buffering the first adjusted input signal to generate a calibrated signal.

Also, the duty cycle calibrating circuit comprising the structure of the duty cycle calibrating module 805 can be summarized as: a seventh inverter (ex. IV_ 7 ), for receiving an input signal; a second falling time tuning circuit (ex. FTC_ 2 ), for receiving output from the sixth inverter to generate a second adjusted input signal (ex. CSY); and an eighth inverter (ex. IV_ 8 ), for inverting the second adjusted input signal to generate a calibrated signal.

FIG. 11 is a circuit diagram illustrating a circuit for the signal combining module 103 described in FIG. 1 , according to one embodiment of the present application. As shown in FIG. 11 , the signal combining module 103 comprises: a first initial combining circuit X_ 1 (in one embodiment, a XOR circuit), a second initial combining circuit X_ 2 (in one embodiment, a XOR circuit), a first edge calibrating device EC_ 1 and a second edge calibrating device EC_ 2 . The first initial combining circuit X_ 1 and the second initial combining circuit X_ 2 receive a plurality of the frequency divided signals to generate output combined signals (i.e. CS in FIG. 1 ). The first edge calibrating device EC_ 1 is coupled between a first voltage level Vdd and the first initial combining circuit X_ 1 , to integrate an edge of the output combined signals. The second edge calibrating device EC_ 2 is coupled between a second voltage level GND and the second initial combining circuit X_ 2 , to integrate an edge of the output combined signals. In this embodiment, the first edge calibrating device EC_ 1 and the second edge calibrating device EC_ 2 are resistors. However, the first edge calibrating device EC_ 1 and the second edge calibrating device EC_ 2 can be replaced by other devices or circuits such as a MOSFET or a current source.

In one embodiment, the first initial combining circuit X_ 1 comprises the first transistor of first type N_ 1 , the second transistor of first type N_ 2 , the third transistor of first type N_ 3 , the fourth transistor of first type N_ 4 , the first transistor of second type P_ 1 , the second transistor of second type P_ 2 , the third transistor of second type P_ 3 , and the fourth transistor of second type P_ 4 . Also, the second initial combining circuit X_ 2 comprises the first transistor of first type N_ 1 , the third transistor of first type N_ 3 , the fifth transistor of first type N_ 5 , the sixth transistor of first type N_ 6 , the first transistor of second type P_ 1 , the third transistor of second type P_ 3 , the fifth transistor of second type P_ 5 , and the sixth transistor of second type P_ 6 . The detail connections for the transistors are illustrated in FIG. 11 , thus are omitted for brevity here.

FIG. 12 and FIG. 13 are examples for the operation of the circuit described in FIG. 11 . Please note the N illustrated in FIG. 12 and FIG. 13 is the same as the N for the frequency dividing ratio N.5 depicted in FIG. 1 . For example, if the frequency dividing module 101 cooperates with the signal combining module 103 to have a frequency ratio of 2.5, the N is 2. Additionally, the X illustrated in FIG. 12 and FIG. 13 is a positive integer between 0˜N−1. Furthermore, the symbol “B” indicates an inverted signal. For example, Q_ 1 B is an inverted signal of Q_ 1 , and Q_N+2+XB is an inverted signal of Q_N+2+X. Via setting N and X, the frequency divided signals inputted to the signal combining module 103 can be set to any combination. Please note the combinations illustrated in FIG. 12 and FIG. 13 are only two examples and do not mean to limit the scope of the present application. The output combined signal generated by the embodiment in FIG. 12 is an inverted signal for the output combined signal generated by the embodiment in FIG. 13 .

FIG. 14 is a wave chart illustrating the operation for the embodiment of FIG. 12 . As shown in FIG. 14 , frequency divided signals Q 1 _Q 3 are input to the transistors in FIG. 11 (i.e. N=1 and x=0), such that output combined signals Q_ 1 ⊕Q_ 3 and Q_ 1 ⊕Q_ 2 are generated. Also, the falling edges of the output combined signals Q_ 1 ⊕Q_ 3 and Q_ 1 ⊕Q_ 2 are integrated to generate the output combined signal CS, which has a 50% duty cycle. The output signal in FIG. 13 is an inverted signal for the output signal in FIG. 12 , thus the wave chart is omitted for brevity here.

FIG. 15 is a circuit diagram illustrating a circuit for the signal combining module 103 described in FIG. 1 , according to another embodiment of the present application. As shown in FIG. 15 , the signal combining module 103 comprises an energy storing circuit E, a charging circuit CC_ 1 and a discharging circuit DC_ 1 . The energy storing circuit E is coupled to the output terminal OT_ 1 . The charging circuit CC_ 1 receives at least two of the frequency divided signals to output a charging current to the energy storing circuit E. The discharging circuit DC_ 1 receives at least two of the frequency divided signals to drain a discharging current from the energy storing circuit E. The energy storing circuit E generates the output combined signal according to the charging current and the discharging current to the output terminal OT_ 1 . The signal combining module 103 can further comprise the charging circuit CC_ 2 and the discharging circuit DC_ 2 . The structures for the charging circuit CC_ 2 and the discharging circuit DC_ 2 are the same as which of the charging circuit CC_ 1 and the discharging circuit DC_ 1 , thus are omitted for brevity here. Also, the combined output signal generated at the output terminal OT_ 1 is an inverted signal for the output combined signal generated at the output terminal OT_ 2 .

In one embodiment, the discharging circuit DC_ 1 comprises a first transistor of first type N_ 1 , a second transistor of first type N_ 2 , a third transistor of first type N_ 3 , and a fourth transistor of first type N_ 4 . Also, the charging circuit CC_ 1 comprises a first transistor of second type P_ 1 , a second transistor of second type P_ 2 , a third transistor of second type P_ 3 , and a fourth transistor of second type P_ 4 . The detail connections of the transistors are illustrated in FIG. 15 , thus are omitted for brevity here.

FIG. 16 and FIG. 18 are two examples for the operation of the circuit described in FIG. 15 . As illustrated in FIG. 16 and FIG. 18 , the transistors in the circuit described in FIG. 15 can receive different combinations of frequency divided signals. The definitions of N and M are described in above-mentioned description, thus are omitted for brevity here. However, please note the input for the third transistor of second type P_ 3 and the fourth transistor of second type P_ 4 can be swapped for both the embodiments illustrated in FIG. 16 and FIG. 18 . Please note the input to other transistors can also be swapped, if the result caused by the swapped input does not change. For example, the inputs for the first transistor of first type N_ 1 and the second transistor of first type N_ 2 can be swapped, the inputs for the third transistor of first type N_ 3 and the fourth transistor of first type N_ 4 can be swapped, and the input for the first transistor of second type P_ 1 and the second transistor of second type P_ 2 can be swapped.

FIG. 17 is a wave chart illustrating the operation of the embodiment described in FIG. 16 , and FIG. 19 is a wave chart illustrating the operation of the embodiment described in FIG. 18 . In the embodiments of FIG. 17 and FIG. 19 , the frequency dividing module having a frequency dividing ratio of 3 and frequency dividing module cooperates with the signal combining module to provide a frequency dividing ratio of 1.5, thus the frequency divided signals comprise Q_ 1 , Q_ 2 and Q_ 3 , that is, N=1 and X=0. As shown in FIG. 17 and FIG. 19 , the output combined signals at the output terminal OT_ 1 and at the output terminal OT_ 2 are generated according to the frequency divided signals Q_ 1 , Q_ 2 and Q_ 3 . In such case, the output combined signal has a duty cycle of 50%, thus can be directly applied as the output signal.

As shown in FIG. 17 and FIG. 19 , the embodiments in FIG. 16 and FIG. 18 can operate in different states: a charging state, a discharging state, and a floating state. In the charging state, the first transistor of second type P_ 1 and the second transistor of second type P_ 2 are conductive, or, the third transistor of second type P_ 3 and the fourth transistor of second type P_ 4 are conductive. In such case, the output terminal OT_ 1 is charged. Oppositely, in the discharging state, the first transistor of first type N_ 1 and the second transistor of first type N_ 2 , or, the third transistor of first type N_ 3 and the fourth transistor of first type N_ 4 are conductive. In such case the output terminal OT_ 1 is discharged. In the floating state, the transistors of the charging circuit CC_ 1 , (or plus CC_ 2 ) and the discharging circuit DC_ 1 (or plus DC_ 2 ) are controlled to be non-conductive. Corresponding to different input signals, the output combined signal with a 50% duty cycle is generated through different states. For example, in FIG. 17 , the output combined signal is generated through three states. However, in FIG. 19 , the output combined signal is generated through only two states: the charging state and the discharging state.

Please note the structure for the signal combining module is not limited to FIG. 11 and FIG. 15 . For example, an XOR circuit 2000 in FIG. 20 can be applied as the signal combining module. As illustrated in FIG. 20 , the XOR circuit 2000 comprises a first transistor of first type N_ 1 , a fifth transistor of first type N_ 5 , a third transistor of first type N_ 3 , a sixth transistor of first type N_ 6 , a first transistor of second type P_ 1 , a second transistor of second type P_ 2 , a third transistor of second type P_ 3 , and a fourth transistor of second type P_ 4 . The connection for the transistors of the XOR circuit 2000 is similar with the first transistor of first type N_ 1 , the third transistor of first type N_ 3 , the fifth transistor of first type N_ 5 , the sixth transistor of first type N_ 6 , the first transistor of second type P_ 1 , the second transistor of second type P_ 2 , the third transistor of second type P_ 3 , and the fourth transistor of second type P_ 4 in FIG. 11 , thus is omitted for brevity here.

FIG. 21 is a signal wave form for the XOR circuit 2000 . For the period (1), only the first transistor of second type P_ 1 and the second transistor of second type P_ 2 are conductive, such that the logic level at the output terminal OT is pulled high. For the period (2), only the first transistor of first type N_ 1 and the fifth transistor of first type N_ 5 are conductive, such that the logic level at the output terminal OT is pulled low. For the period (3), only the third transistor of second type P_ 3 and the fourth transistor of second type P_ 4 are conductive, such that the logic level at the output terminal OT is pulled high. For the period (4), only the third transistor of first type N_ 3 and the sixth transistor of first type N_ 6 are conductive, such that the logic level at the output terminal OT is pulled low.

Based upon above-mentioned embodiments, a signal generating method for generating an output signal with a 50% duty cycle can be acquired. The signal generating method corresponding to FIG. 1 comprises the following steps: (a) generating a plurality of frequency divided signals utilizing a frequency dividing ratio equaling to M, wherein the M is an positive integer; (b) combining at least two of the frequency divided signals to generate at least one output combined signal; and (c) generating the output signal based on the output combined signal. The step (a) cooperates with the step (b) to provide a frequency dividing ratio equaling to N.5, wherein the N is a positive integer.

Also, the signal generating method corresponding to FIG. 2A comprises the following steps: delaying at least one of the frequency divided signal to generate at least one delayed frequency divided signal; and combining at least two of the delayed frequency divided signals, or for combining at least one the frequency divided signal and at least one the delayed frequency divided signal, to generate the output signal. The frequency dividing module cooperates the signal combining module to provide a frequency dividing ratio equaling to N.5, wherein the N is a positive integer.

Other detail steps can be acquired based on above-mentioned embodiments, thus are omitted for brevity here.

In view of above-mentioned embodiments, an output signal with divide-by-N.5 ratio and a 50% duty cycle can be used in IQ divider to generate divide-by-M quadrature signals, where M is odd number, since no phase calibration is used after the IQ divider.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.