JPH0758548A - Information transmission system - Google Patents

Abstract

PURPOSE:To suppress the carrier component in the communication of the frequency modulation system while keeping the excellent quality in the frequency modulation. CONSTITUTION:One clock generating source 1 and two phase locked loop oscillators PLL-1, PLL-2 are used, the phase locked loop oscillators oscillate signals whose phase difference is 180 deg., and a phase difference of 180 deg. is provided to modulation signals applied for frequency modulation. Then outputs of the two phase locked loop oscillators are added by an adder 11 at the same level to eliminate a carrier component and even-degree side band components. Thus, only odd-degree side band components are transmitted, and a multiple type phase locked loop oscillator is used in a receiver to attain demodulation from the received signal. This system is equivalent to carrier suppression modulation in frequency modulation, and transmission power is saved when the modulation figure is small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication system between a base unit and a small unit of a cordless telephone or a wireless communication modulation system effective for wireless communication via a satellite. The invention relates to the field of devices and devices for receiving modulated signals.

[0002]

2. Description of the Related Art A frequency modulation type information transmission system has a constant amplitude, exhibits various excellent characteristics, and is widely used in the field of communication. However, since there are drawbacks such as a large loss of transmission power, other communication schemes such as carrier suppression communication schemes have been put to practical use, but these save transmission power but have other drawbacks.

[0003]

If the carrier wave is suppressed in the frequency modulation signal, the transmission power can be reduced by the carrier power component. However, in the case of frequency-modulated signals, in many cases upper and lower sidebands are generated and it is virtually impossible to extract only the necessary sideband signals. The present invention relates to a modulation system that retains the excellent characteristics of the frequency modulation system and removes excess signal components to save transmission power.

[0004]

FIG. 1 shows an example for solving the problem. In FIG. 1, two phase-locked oscillators (PLL-1, PLL-2) input in-phase output and anti-phase output (17) from a modulation signal input (18) to filters (16) and (15), respectively. , A phase-locked oscillator (PLL-1) having a frequency modulation function, and (PLL
-2) and outputs outputs S1 (t) and S2 (t) of the voltage controlled oscillators (4) and (9), respectively,
It is added and subtracted by the adder of 1). In the case of FIG. 1, the phase inverting amplifier (6) causes the phases of the input clocks of the phase-locked oscillators (PLL-1) and (PLL-2) to be 180 degrees relative to each other.
Since there is a phase difference of degrees, the adder of (11) outputs the outputs of the phase-locked oscillators (PLL-1) and (PLL-2), S1.
It suffices to add (t) and S2 (t). When there is a level difference between the modulated wave radiations of the phase locked oscillators (PLL-1) and (PLL-2), the level can be adjusted by the adder. It is also possible to intentionally leave a part of the carrier wave by this device. The frequency modulator (PLL-
When only one modulation signal input of 1) or (PLL-2) is set to zero (for example, when the output of the filter 15 is zero), only the frequency-modulated carrier can be removed. FIG. 3 shows a spectrum diagram when the outputs of the two frequency modulators of FIG. 1 are added, in which (h1) and (h
2) is the output of (PLL-1) and (PLL-2), respectively, and (h3) is the output of the adder (11).
This example corresponds to the case where the modulation index is small, but when the modulation index becomes large, the even-order components of the carrier and the sideband are removed. FIG. 2 shows an example of a modulated signal receiver from the transmitter according to FIG. In FIG. 2, (1) is an antenna receiving section, (2) is a high frequency selective amplifier, (3) is a frequency mixer, and (4) is a first local oscillator. In this case, the first intermediate frequency in (5) is a high frequency. Tune to twice the difference between the received frequency and the first local oscillation frequency. At this time, since the carrier wave component of frequency modulation is generated by the signal of the product of the upper side wave and the lower side wave of the modulation signal, the second intermediate frequency stage in FIG. 2 has the same function as the conventional frequency modulation wave receiving unit. It will be good. In the example of FIG. 2, (6) is the second frequency mixer, (7) is the second local oscillator, and the second intermediate frequency in (8) is the difference between the first intermediate frequency and the second local oscillation frequency. (8) selectively amplifies the second intermediate frequency, and the phase-locked oscillator (PLL-3) at the next stage operates as a detector of the frequency modulation wave. In FIG. 2, the first intermediate frequency of (5) is selected as the difference between the high frequency input frequency and the first local oscillation frequency as in the conventional case, and the second intermediate frequency (8 ), Input it to the next-stage phase-locked oscillator (PLL-3), frequency-detect it (1
The detection output (14) can be taken out from the low pass filter of 3). In this case, the phase-locked oscillator (PLL-
In the operation of 3), the phase comparator (9) operates as a nonlinear mixer, (10) is a low-pass filter having an amplification function, and (1)
1) is a voltage (or current) controlled oscillator that oscillates in synchronization with a harmonic of twice the second intermediate frequency, and carrier recovery and frequency detection are possible with this phase-locked oscillator (PLL-3). That is, when such a phase-locked oscillator is used, it is possible to simultaneously reproduce and detect the carrier wave with respect to the frequency-modulated wave from which the carrier wave has been removed by the transmitter of FIG. (Phase-locked Oscillation with Double Carrier Wave) FIG. 4 shows a receiver which is an inverse configuration of the modulator configuration method of FIG. The modulated signal from the transmitter of FIG. 1 is input from (1) of FIG. 4 and passes through the high frequency amplifier of (2) to (3)
The mixer (4) is mixed with the output from the local oscillator to perform frequency selective amplification and phase inversion at an intermediate frequency based on the difference frequency between the input signal frequency (1) and the local oscillation frequency. Therefore, they are input to the phase-locked oscillators (PLL-1) and (PLL-2) as intermediate frequency outputs having mutually opposite phases. Next, the operation of the phase locked oscillator (PLL-1) will be described.
(8) is a phase comparator, which is preferably an ecclusive-or type or a ring modulator type, because the synchronous oscillation frequency of the voltage (current) controlled oscillator in (10) is set to twice the input intermediate frequency in (8). Since it oscillates synchronously, the type that full-wave rectifies the input wave is superior for synchronous control. (9) is a control filter having an amplifying function, and a detection signal of a modulated wave can be taken out from its output. Similarly, a phase-locked oscillator (PLL-
Since the detection output of the opposite phase can be taken out from the output of the control filter (13) of 2), these can be input to the adder of (16) and reproduced as the output (19) of the modulation signal at the time of transmission. The voltage controlled oscillator (10) or (14) of FIG.
Since the output of is restored to the frequency modulation wave with the carrier wave inserted, if the received signal contains pulse noise, (17)
It is also possible to detect the signal by a single frequency demodulator (product detection) via the amplitude limiter.

[0005]

Since the amplitude of the frequency wave number modulation wave is constant, a constant transmission power is required even when there is no modulation signal input. The present invention saves the transmission power by leaving the goodness of the frequency modulation method,
It is a communication method for transmitting information. As shown in the embodiment of FIG. 1, two phase-locked oscillators (PLL-1), and (PLL-1)
-2) is driven by the same clock source (1),
(In this case, the clock input phase of the PLL-2 is an inverted phase shifted by 180 degrees.) Not only the oscillation frequency of the voltage controlled oscillators (4) and (9) but also the phase is controlled to obtain the output, and the addition is performed. It is intended to remove the carrier component of the frequency modulated wave as the output of the device (11). What is important here is that it is desirable that the modulation signal inputs of the two frequency modulators (PLL-1 and PLL-2, which are phase-locked oscillators), are in opposite phases to each other and have the same voltage level. (Outputs of filters 15 and 16 in FIG. 1)

In this case, carrier components are removed from both frequency modulated waves as shown in the example of FIG. 3, and odd sidebands are added. In this example, the modulation index is small. When the modulation index is large, a large number of even-order sidebands and odd-order sidebands are generated, but the even-order sideband component is the adder (1
1), and the odd sideband components are added. The odd sideband component corresponds to the phase information component in the frequency modulated wave, and the carrier and the even sideband component transmit the amplitude information component. As described above, due to the use of the frequency modulator, the modulation signal of the present invention can be suppressed to a certain amplitude or less. Note that the transmission power is suppressed because the carrier component and the even-order sideband component are removed, as if the carrier-suppressed amplitude modulation method. However, since sidebands are generated differently and the characteristics of frequency modulation are retained, the receiver can suppress noise by using characteristics such as the limiter effect.
In case of voice transmission, when the voice input is zero
In the receiver, the phase-locked oscillator (PLL-3, or PLL-1, PLL-2) is no longer in the phase-locked state. Therefore, a pilot signal of a constant level or a cordless denwa 30hz-
It is preferable that the modulated signal shown in claim 3 is used as the transmission signal in which the identification signal in the range of 200 hz is inserted. The modulation level by the pilot signal or the identification signal in this case is selected to be 1 / 10-1 / 3 of the main modulation signal level.

[0007]

1 is an example of a transmission signal generator according to the present invention. This figure will be described. Phase-locked oscillators (PLL-1, PLL-) having two equal circuit constants.
In contrast to 2), one clock generation source (1), the comparison signal input of one comparator (2) and the other comparator (7) is reversed (180 degree phase difference) by the phase inverter (6). By doing so, the device (11) for adding the outputs of the two phase-locked oscillating devices at the same level is intended to suppress the carrier component of both the phase-locked oscillating devices. Note that (18) is a modulation signal (voice voltage input as an example), which is divided into an in-phase signal and an anti-phase signal by the amplifier in (17) and passed through the low-pass filters (15) and (16) respectively to obtain a phase-locked oscillator. Are supplied to the voltage controlled oscillators (4) and (9) to generate frequency modulated waves. As shown in FIG. 1, the sum of the outputs of the two frequency modulators (phase-locked oscillators) when the phase inversion of Kuroku and the phase inversion of the modulation signal are performed simultaneously is composed of the sum of only odd-order sidebands. . That is, the carrier component and the even sideband component are removed. The phase difference between the odd-order sideband component and the carrier-side component and the even-order sideband component is 90 degrees (cosine wave and sine wave). FIG. 3 shows an example of a case where the frequency deviation of the frequency modulation wave is small, and (h1) and (h2) are two phase-locked oscillators (PLL-1, PLL-2), respectively.
The sum of the output of the frequency spectrum of (h
3) I want to become.

FIG. 2 is a system diagram of a receiver for receiving the modulated signal of FIG. 1, where (1) is a receiving antenna section and (2) is a receiving antenna section.
Is a high frequency amplifier, (3) is a first frequency mixer, (4) is a first local oscillator, (5) is a first intermediate frequency selective amplifier,
(6) is the second frequency mixer, (7) is the second local oscillator,
(8) is a second intermediate frequency selective amplifier (PLL-
3) simultaneously reproduces the carrier frequency and demodulates the modulation (1
The output (14) is taken out through the low pass filter of 3). The portable operation of FIG. 2 will be described. First, frequency mixing is performed by the first frequency mixer at the antenna input frequency and the first local oscillation frequency, and the first frequency mixing by the difference frequency is performed.
It is selectively amplified at the intermediate frequency, and similarly, the second intermediate frequency is also output at the second frequency mixer, and the frequency is selectively amplified at (8) and input to the frequency demodulator (PLL-3) at the next stage.
(9) uses a phase comparator that operates in an exclusive OR type, (10) is a low-pass filter having an amplifying function, and (11) is a voltage-controlled oscillator that is twice the second intermediate frequency. A carrier wave (twice the carrier wave) is generated by performing phase-locked oscillation at the frequency of, and the phase of the carrier wave is delayed by 90 degrees due to the integral characteristic of the phase-locked oscillator. Therefore, by inserting the carrier wave by the phase comparator (9), (10 ), It becomes possible to demodulate the modulated signal.

The operation as another receiving method will be described with reference to FIG. In this case, the first intermediate frequency is selected to be 2 of the difference between the antenna input signal frequency of (1) and the local oscillation frequency of (4).
In this method, the carrier component is reproduced by this, and thereafter, the same frequency amplification and amplitude limitation as those of the ordinary frequency modulated wave are performed, and the frequency is demodulated. FIG. 4 relates to a modulated signal receiving apparatus of the present invention using two phase-locked oscillators. The structure and operation of the phase-locked oscillator is the phase-locked oscillator (P
LL-3) but in the case of FIG. 4, the following phase-locked oscillators (PLL-1, PLL-2) are driven by both the in-phase and anti-phase as the first intermediate frequency amplifier output of (5). , The outputs of the low-pass filters (9) and (13) are added to the adder (1
6) is added to obtain a demodulated signal (19). Figure 4
If you add the explanation about the system diagram of the receiver of (1)
Is a received signal input antenna section, (2) is a high frequency amplification section,
(3) is a mixer, (4) is a local oscillator, (5) selectively amplifies the difference frequency between the input signal frequency and the local oscillation frequency, and supplies in-phase and anti-phase outputs to the next stage. (8, 12) is a phase comparator, (9, 13) is a low-pass filter having an amplification function,
(10, 14) is a voltage controlled oscillator that oscillates at a frequency twice the first intermediate frequency. (17) in FIG.
(18) is a device added for the sake of explanation. Since the output of the voltage controlled oscillator of (10) is a frequency modulated wave in which a carrier wave is inserted, the amplitude limiter of (17) and the frequency detector of (18) are used (20). ), The demodulated signal can be taken out. In this case, the effect of suppressing noise can be sufficiently obtained.

[0010]

As shown in the embodiment of FIG. 1, when the same clock source (oscillation source) is used, the carrier wave and the even sidebands in the frequency modulated wave can be eliminated, and the transmission power of telecommunications can be reduced. Savings are possible. This is especially useful when the frequency deviation is small or when transmitting a video signal by satellite broadcasting. Further, in the receiver of FIG. 2, when a frequency of twice the difference between the input signal frequency and the local oscillation frequency is detected in the signal mixer, the carrier component is regenerated and becomes a normal frequency modulated wave, which can be easily demodulated. is there. That is, a carrier wave suppression transmission system that maintains good frequency modulation is realized.

[0011]

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a modulation signal generation system according to the present invention.

FIG. 2 is a system diagram showing an example of a modulated signal receiving apparatus according to the present invention.

FIG. 3 is a frequency spectrum diagram for explaining a modulated signal of the present invention.

FIG. 4 is a system diagram showing an example of a modulated signal receiving apparatus according to the present invention.

Claims (6)

[Claims] 1. A communication system for transmitting information by a signal formed by removing (or remaining a part of) a carrier wave and even sidebands in a frequency modulation signal. 2. A reference clock generator (1), a clock phase inverting device (6), two phase locked oscillators (PLL-1) and (PLL-2), and a phase locked device as shown in FIG. Modulation signal sources (15, 16, 1) for driving the oscillator
7. 18), and a device (11) for adding (or subtracting) both phase-locked oscillator outputs.
Modulation signal generation method. 3. The communication system according to claim 1, wherein an identification signal of a constant level or a pilot carrier is inserted to hold the minimum carrier information. 4. A phase comparator (9), a low-pass filter (10), and a phase-locked oscillator (PLL-) as shown in FIG.
3. A phase-locked oscillating device (PLL-3) comprising an oscillating device (11) that oscillates under voltage (or current) control at a frequency twice as high as the input signal frequency in 3).
Demodulator for a few modulated signals. 5. As a modulation signal receiving system according to claim 1 or 3, as shown in FIG. 2, a frequency mixer (3), a local oscillator (4), and a double intermediate frequency are selectively amplified and amplitude limited amplified. The modulated signal receiving system according to claim 1 or 3, wherein frequency detection is performed via a device. 6. A device (5) for generating an in-phase signal and a phase inversion signal as shown in FIG. 4, and two phase-locked oscillating devices (PLL-1, PLL-2) each having its output as an input. Each phase-locked oscillator has a phase comparator (8, 12),
Low-pass filter (9, 13), voltage (or current) that oscillates synchronously with the frequency twice the input signal frequency of the phase-locked oscillator
Controlled oscillators (10, 14) and low-pass filters (9,
The modulated signal receiving system according to any one of claims 1, 2 and 3, which comprises a device (16) for adding the outputs of (13).