BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a combined phase-locked loop (PLL) and amplitude-locked loop (ALL) module for switching FM signals received from a co-channel. More particularly, the present invention relates to the combined phase-locked loop and amplitude-locked loop module implemented by using field programmable gate arrays (FPGAs).

2. Description of the Related Art

A phase-locked loop used in telecommunications, computer and consumer devices is well known to a person skilled in the art, and has been described in many U.S. patents. For example, the related U.S. patents include: U.S. Pat. No. 7,271,664, entitled â€œphase locked loop circuit;â€ U.S. Pat. No. 7,253,692, entitled â€œphase locked loop;â€ U.S. Pat. No. 7,206,369, entitled â€œprogrammable feedback delay phase-locked loop for high-speed input/output timing budget management and method of operation thereof;â€ U.S. Pat. No. 7,174,144, â€œcalibration of a phase locked loop;â€ U.S. Pat. No. 7,170,965, entitled â€œlow noise divider module for use in a phase locked loop and other applications;â€ U.S. Pat. No. 7,148,758, entitled â€œintegrated circuit with digitally controlled phase-locked loop;â€ U.S. Pat. No. 7,095,992, entitled â€œphase locked loop calibration;â€ U.S. Pat. No. 7,082,295, entitled â€œon-chip loop filter for use in a phase locked loop and other applications;â€ U.S. Pat. No. 7,042,972, entitled â€œcompact, low-power low-jitter digital phase-locked loop;â€ U.S. Pat. No. 7,002,419, entitled â€œmetal programmable phase-locked loop;â€ U.S. Pat. No. 6,998,922, entitled â€œphase locked loop modulator calibration techniques;â€ U.S. Pat. No. 6,812,688, entitled â€œsignal acquisition method and apparatus using integrated phase locked loop;â€ U.S. Pat. No. 6,801,092, entitled â€œphase locked loop that avoids false locking;â€ U.S. Pat. No. 6,771,715, entitled â€œdemodulator using cordic rotator-based digital phase locked loop for carrier frequency correction;â€ U.S. Pat. No. 6,710,635, entitled â€œfrequency and phase locked loop;â€ U.S. Pat. No. 6,703,875, entitled â€œdevice for emulating phase-locked loop and method for same;â€ U.S. Pat. No. 6,680,644, entitled â€œdigital interpolation window filter for phase-locked loop operation with randomly jittered reference clock;â€ U.S. Pat. No. 6,542,040, entitled â€œphase-locked loop employing programmable tapped-delay-line oscillator;â€ U.S. Pat. No. 6,469,553, entitled â€œphase-locked loop circuitry for programmable logic devices;â€ U.S. Pat. No. 6,437,650, entitled â€œphase-locked loop or delay-locked loop circuitry for programmable logic devices;â€ U.S. Pat. No. 6,356,158, entitled â€œphase-locked loop employing programmable tapped-delay-line oscillator;â€ U.S. Pat. No. 6,356,129, entitled â€œlow jitter phase-locked loop with duty-cycle control;â€ U.S. Pat. No. 6,356,127, entitled â€œphase locked loop;â€ U.S. Pat. No. 6,271,729, entitled â€œphase-locked loop or delay-locked loop circuitry for programmable logic devices;â€ U.S. Pat. No. 6,218,876, entitled â€œphase-locked loop circuitry for programmable logic devices;â€ U.S. Pat. No. 6,177,844, entitled â€œphase-locked loop or delay-locked loop circuitry for programmable logic devices;â€ U.S. Pat. No. 6,133,769, entitled â€œphase locked loop with a lock detector;â€ and U.S. Pat. No. 5,999,025, entitled â€œphase-locked loop architecture for a programmable logic device.â€ Each of the above-mentioned U.S. patents is incorporated herein by reference for purposes including, but not limited to, indicating the background of the present invention and illustrating the state of the art.

An amplitude-locked loop also known in the art is constituted by a circuitry which embodies all the principles of the PLL but operates in the amplitude domain or real domain and not in the frequency or imaginary domain. For example, U.S. Pat. No. 5,341,106, issued to Pettigrew on Aug. 23, 1994, discloses a circuit using an amplitude-locked loop and a phase-locked loop to remove AM crosstalk from an FM signal, which is incorporated herein by reference for purposes including, but not limited to, indicating the background of the present invention and illustrating the state of the art.

With regard to the problematic aspects naturally occurring during the use of the PLL or ALL circuit, it cannot provide a function of exchanging or switching FM signals received from a co-channel while removing the effect of co-channel interference (CCI) and recovering the messages from carriers. Hence, there is a need for improving the function of the PLL or ALL circuit for providing the function of exchanging or switching FM signals received from a co-channel.

As is described in greater detail below, the present invention intends to provide a combined PLL and ALL module for switching FM signals received from a co-channel. The combined PLL and ALL module is preferably implemented by using FPGAs. The combined PLL and ALL module is controlled to process FM signals by adjusting the ratio of second amplitude to first amplitude to closely approach a predetermined value. Hence, FM signals are separated and switched by the combined PLL and ALL module in such a way as to mitigate and overcome the above problem.

SUMMARY OF THE INVENTION

The primary objective of this invention is to provide a combined PLL and ALL module for switching FM signals received from a co-channel. The combined PLL and ALL module is controlled to process FM signals by adjusting the ratio of second amplitude to first amplitude to closely approach a predetermined value â€œm.â€ Hence, the combined PLL and ALL module of the present invention is successful in separating and switching FM signals at a crossover pointâ€”a singular point of m=1 for example.

Another objective of this invention is to provide the combined PLL and ALL module for switching at least two different FM signals by simply adjusting the ratio of second amplitude to first amplitude to closely approach a predetermined value in demodulation. Accordingly, switching the two different FM signals or monitoring one of the different FM signals in demodulation is unsuccessful unless using the combined PLL and ALL module to adjust the ratio of second amplitude to first amplitude. Hence, the FM signals can be protected in demodulation due to the fact that a demodulation process for the FM signals require operating the combined PLL and ALL module. Advantageously, the high performance of the combined PLL and ALL module of the present invention can significantly achieve a high degree of information security of the FM signals in communication.

Another objective of this invention is to provide the combined PLL and ALL module for switching at least two different FM signals by simply adjusting the ratio of second amplitude to first amplitude to closely approach a predetermined value in demodulation. Hence, a public key or a private key for use in data encryption and data decryption of the FM signals in communication can further be omitted due to the fact that the combined PLL and ALL module is applied. Advantageously, the high performance of the combined PLL and ALL module of the present invention can simplify the entire communication procedure for achieving the high security application of using FM transmission signals.

The combined PLL and ALL module in accordance with an aspect of the present invention includes a PLL unit and an ALL unit electrically connected therewith. The PLL unit is used to initially process FM signals received from a co-channel. Outputs of the PLL unit are sent to the ALL unit and processed therein. The PLL unit and the ALL unit are controlled to process the FM signals by adjusting the ratio of second amplitude to first amplitude to closely approach a predetermined value such that the two FM signals are switched.

In a separate aspect of the present invention, the predetermined value is approximately 1.

In a further separate aspect of the present invention, the PLL unit serially connects with the ALL unit.

In a yet further separate aspect of the present invention, the PLL unit and the ALL unit are implemented by FPGAs.

In a yet further separate aspect of the present invention, the combined PLL and ALL module further connects with a pair of filter units to demodulate outputs of the ALL unit.

In a yet farther separate aspect of the present invention, the filter units are selected from butterworth filters.

Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a block diagram of a combined PLL and ALL module for switching FM signals received from a co-channel in accordance with a preferred embodiment of the present invention;

FIG. 2 is a block diagram of the combined PLL and ALL module in accordance with the preferred embodiment of the present invention while exchanging two output signals in adjusting operation; and

FIG. 3 is a schematic circuit of the combined PLL and ALL module implemented by a design of FPGAs in accordance with a first embodiment of the present invention;

FIG. 4 is a schematic circuit of the combined PLL and ALL module implemented by another design of FPGAs in accordance with a second embodiment of the present invention; and

FIG. 5 is a block diagram of a series of the combined PLL and ALL modules in accordance with the preferred embodiment of the present invention while exchanging multiple output signals.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, blocks of a combined PLL and ALL module for switching FM signals received from a co-channel in accordance with a preferred embodiment of the present invention are shown. In FIG. 1, the combined PLL and ALL module of the present invention is designated numeral 1, and a FM signal generator applied in the preferred embodiment of the present invention is designated numeral 2. The combined PLL and ALL module 1 includes a PLL unit designated numeral 11 and an ALL unit designated numeral 12.

With continued reference to FIG. 1, the FM signal generator 2 can generate a series of FM signals transmitting to the combined PLL and ALL module 1 in a predetermined co-channel. The FM signal generator 2 includes a FM modulator 21 which can modulated a first signal m₁(t) and a second signal m₂(t). The FM signal generator 2 is operated to convert the first signal m₁(t) and the second signal m₂(t) into two FM signals for wireless communication.

Furthermore, a noise signal w(t) is added to the first signal m₁(t) and the second signal m₂(t) for interference simulation in the present invention. It will be understood that w(t)=0 defines no noise signal which may be added to the first signal m₁(t) and the second signal m₂(t) in the present invention. Subsequently, the two FM signals of the first signal m₁(t) and the second signal m₂(t) are transmitted to the combined PLL and ALL module 1.

Still referring to FIG. 1, the circuitry structure of the combined PLL and ALL module 1 shall be described. The PLL unit 11 electrically connects with the ALL unit 12 so as to process the two FM signals of the first signal m₁(t) and the second signal m₂(t). In a preferred embodiment, the combined PLL and ALL module 1 is designed to have the PLL unit 11 serially connecting with the ALL unit 12. Once received, the PLL unit 11 is used to initially process the two FM signals of the first signal m₁(t) and the second signal m₂(t) received from the co-channel, and to suppress the effect of co-channel interference (CCI) for recovering the first signal m₁(t) and the second signal m₂(t). Subsequently, outputs of the PLL unit 11 are sent to the ALL unit 12 and processed therein in order to enhance the removal of the effect of CCI.

Preferably, the PLL unit 11 and the ALL unit 12 are controlled to process the two FM signals of the first signal m₁(t) and the second signal m₂(t) by adjusting the ratio of second amplitude of the second signal m₂(t) to first amplitude of the first signal m₁(t) to closely approach a predetermined value. In the present invention, â€œmâ€ is selected to define the predetermined value of the ratio of second amplitude of the second signal m₂(t) to first amplitude of the first signal m₁(t). Preferably, the value of â€œmâ€ is approximately 1 which is a singular point formed as a crossover point of FM signals in communication.

In a preferred embodiment, the combined PLL and ALL module 1 further connects with a pair of filter units 13 for demodulating the FM signals. In another preferred embodiment, the filter units 13 are selected from butterworth filters. Accordingly, the combined PLL and ALL module 1 generates a first demodulated signal (identified as â€œS₁(t)â€ ) and a second demodulated signal (identified as â€œS₂(t)â€ ). Prior to adjusting the combined PLL and ALL module 1, the two FM signals of the first signal m₁(t) and the second signal m₂(t) are processed and then separated into the first demodulated signal S₁(t) and the second demodulated signal S₂(t) respectively.

Turning now to FIG. 2, a block diagram of the combined PLL and ALL module in accordance with the preferred embodiment of the present invention while exchanging two signals in adjusting operation. In adjusting the combined PLL and ALL module 1, for example,

the value of â€œmâ€ is 0.99999999999999999999,

where â€œmâ€ is smaller than 1 and closely approaches 1; or

the value of â€œmâ€ is 1.00000000000000001,

where â€œmâ€ is greater than 1 and closely approaches 1.

Referring to FIG. 2, once adjusted, the second demodulated signal S₂(t) and the first demodulated signal S₁(t) generated from the combined PLL and ALL module 1 are successfully exchanged. Referring back to FIG. 1, in comparing with those shown in FIG. 2, the first demodulated signal S₁(t) and the second demodulated signal S₂(t) generated from the combined PLL and ALL module 1 are not exchanged due to the fact that the value of â€œmâ€ does not extremely approach 1.

As has been discussed above, the combined PLL and ALL module 1 in accordance with the present invention successfully provides the function of exchanging the first demodulated signal S₁(t) and the second demodulated signal S₂(t) by adjusting the value of â€œmâ€ . Hence, the second demodulated signal S₂(t) and the first demodulated signal S₁(t) are correspondingly obtained, as best shown in FIG. 2.

Referring again to FIGS. 1 and 2, in switching at least two different FM signals, the combined PLL and ALL module 1 must be applied to adjust the ratio of second amplitude to first amplitude closely approaching a predetermined value in demodulation. Accordingly, switching the first signal m₁(t) to the second signal m₂(t) and vice versa or monitoring one of the first signal m₁(t) and the second signal m₂(t) in demodulation is unsuccessful unless using the combined PLL and ALL module 1 for adjusting the ratio of second amplitude to first amplitude. Hence, the first signal m₁(t) and the second signal m₂(t) can be protected in demodulation due to the fact that a demodulation process for the first signal m₁(t) and the second signal m₂(t) require operating the combined PLL and ALL module 1. Advantageously, the high performance of the combined PLL and ALL module 1 of the present invention can significantly achieve a high degree of information security of the first signal m₁(t) and the second signal m₂(t) in communication.

In addition to this, a public key or a private key for use in data encryption and data decryption of the first signal m₁(t) and the second signal m₂(t) in communication may further be omitted by using the combined PLL and ALL module 1. It will be understood that the first signal m₁(t) and the second signal m₂(t) cannot be separated in other types of demodulators in the known art. In other words, a public key or a private key for use in data encryption and data decryption of the first signal m₁(t) and the second signal m₂(t) may be unnecessary. Advantageously, the high performance of the combined PLL and ALL module 1 of the present invention can simplify the entire communication procedure for the FM signals.

Turning now to FIG. 3, a schematic circuit of the combined PLL and ALL module implemented by a design of FPGAs in accordance with a first embodiment of the present invention is shown. The PLL unit 11 and the ALL unit 12 formed in the combined PLL and ALL module 1 are shown in the middle portion of FIG. 3. The FM signal generator 2 connected with the combined PLL and ALL module 1 is shown in the left portion of FIG. 3. Shown in the right portion of FIG. 3 are the two filter units 13 which are connected with the combined PLL and ALL module 1.

Turning now to FIG. 4, a schematic circuit of the combined PLL and ALL module implemented by another design of FPGAs in accordance with a second embodiment of the present invention is shown. The combined PLL and ALL module 1 is designed as a single chip, as best shown in the right portion of FIG. 4.

Turning now to FIG. 5, a block diagram of a series of the combined PLL and ALL modules in accordance with the preferred embodiment of the present invention is shown. A plurality of the combined PLL and ALL modules 1 are applied to demodulate different signals m₁(t), m₂(t), . . . , m_n(t) each of which possesses different power. In demodulation, the signals m₁(t), m₂(t), . . . , m_n(t) can be exchanged by selectively controlling one of the combined PLL and ALL modules 1.

Although the invention has been described in detail with reference to its presently preferred embodiment, it will be understood by one of ordinary skill in the art that various modifications can be made without departing from the spirit and the scope of the invention, as set forth in the appended claims.