JP2778519B2 - FM transceiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM transceiver.
In particular, time-division FM using the same carrier frequency for transmission and reception
The present invention relates to a transmission / reception device.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an example of this type of conventional FM transmitting / receiving apparatus. The baseband signal to be transmitted is input to the reduction filter 9 via the input terminal 17,
After removing the high frequency band, the VCO
(Voltage-controlled oscillator) 1 Control voltage input. This VC
The baseband signal is directly FM-modulated by O1 and VC
It will be derived to O output.

[0003] This FM modulated wave is n
The frequency is multiplied (n is a positive integer), amplified by the high frequency amplifier 10, band-limited by the bandpass filter 11, and transmitted from the antenna 14 via the switch 13.

[0004] The above is the time of transmission, but it is assumed that the switches 7 and 13 are switched as indicated by broken lines during reception.
At this time, the received FM modulated wave from the antenna 4 is input to the bandpass filter 12 and is band-limited and amplified by the high frequency amplifier 15.
Is one input.

[0005] The other input of the frequency mixer 5 is supplied with a frequency n times the oscillation frequency of the VCO 1, and this frequency mixing output becomes an FM demodulated baseband signal via a low-pass filter 6, and By being used as a control voltage of the VCO 1, a phase locked loop type FM demodulation circuit configuration is obtained.

In this example, the VCO 1 is used as an FM modulator during transmission, and is used as a local oscillator of a phase locked loop type FM demodulation circuit during reception. The carrier frequency is determined by the DC bias voltage Vc applied to the control voltage input terminal of the VCO 1. In this example, the carrier frequency is not changed.

FIG. 4 is a block diagram showing another example of another FM transmitting / receiving apparatus, which is described in Japanese Patent Application Laid-Open No. 57-192144. The same parts as those in FIG. 3 are indicated by the same reference numerals.

In this embodiment, a frequency synthesizer PL
An L (phase locked loop) circuit 21 and a VCO 25 are separately provided, and the synthesizer allows the local oscillation frequency in each of the frequency mixers 24 and 23 at the time of transmission and reception to be variable, thereby providing a function of varying the carrier frequency for both transmission and reception. Structure.

The baseband signal to be transmitted is input terminal 1
7 becomes the control input voltage of the VCO 1 through the switch 7 and receives FM modulation directly. This FM modulated wave is mixed with the local oscillation frequency changed by the synthesizer 21 and the VCO 25 in the frequency mixer 22, frequency-converted, and input to the bandpass filter 24. The output after the band limitation is transmitted to the antenna 14 via the high-frequency amplifier 10 and the switch 13.
Sent from

At the time of reception, the FM received by the antenna 14
The modulated wave is amplified by the high-frequency amplifier 15, mixed with the local oscillation frequency output from the VCO 25 in the frequency mixer 23, frequency-converted to an intermediate frequency, and
9 is input.

The output after the band limitation is amplified by the intermediate frequency amplifier 20 and amplitude-limited by the amplitude controller 16, and then becomes one input of the frequency mixer 5. The output of the VCO 1 is supplied to the other input of the frequency mixer 5, and the low-frequency component of the frequency-mixed output by the low-pass filter 6 is derived from an output 18 as an FM demodulated baseband signal. , VCO1 to form a phase locked loop type FM demodulation circuit.

[0012]

In the conventional FM transmitter / receiver shown in FIG. 3, the oscillation frequency of the VCO 1 is determined only by the bias voltage Vc applied as the control voltage, and the stable frequency of a frequency synthesizer or the like is obtained. Since there is no frequency loop, there is no standard for the frequency.Therefore, it is necessary to change the frequency during operation while measuring using a measuring device such as a frequency counter. It is possible.

In the conventional FM transmitting / receiving apparatus shown in FIG.
Although the carrier frequency can be accurately changed by the frequency synthesizer 21, the high-frequency
, A bandpass filter 24, and a VCO 25 for varying the local oscillation frequency are required, and the structure becomes complicated and expensive.

It is an object of the present invention to provide an FM transmitting / receiving apparatus which has a simple structure and which can easily change a carrier frequency by a frequency synthesizer function.

[0015]

According to the present invention, a voltage-controlled oscillating means to which a transmission baseband signal is applied as a control voltage at the time of transmission and an FM demodulation baseband signal at the time of reception, respectively, A transmitting means for transmitting an output of the means as a transmission FM modulated wave; and a frequency mixing of an output of the voltage controlled oscillating means with a received FM modulated wave upon reception to derive a low frequency component of the mixed output as the FM demodulated baseband signal. A high-pass filter for receiving the transmission baseband signal during transmission and receiving the FM demodulation baseband signal during reception as a control voltage of the voltage-controlled oscillating means. And determining the oscillation frequency of the voltage-controlled oscillating means so as to determine the carrier frequency of the transmission FM modulation wave or the reception FM modulation wave. Synthesizer and, FM, characterized in that it comprises a low-pass filter means for deriving a control voltage for said voltage controlled oscillation means receives the output of the synthesizer
A transmitting / receiving device is obtained.

Further, according to the present invention, a transmitting / receiving antenna, first selecting means for selectively deriving a transmitting baseband signal and an FM demodulated baseband signal, and a selection output of the selecting means are input. High-pass filtering means, a voltage-controlled oscillating means having an output of the high-pass filtering means as a control input, and supplying an oscillation output of the voltage-controlled oscillating means to the transmitting / receiving antenna or receiving FM modulation from the transmitting / receiving antenna A second selecting means for selecting whether to derive a wave, and a frequency mixing of the received FM modulated wave by the second selecting means and an output of the voltage controlled oscillating means to reduce a low frequency component thereof to the FM demodulation base. Means for deriving the signal as a band signal;
A synthesizer for determining an oscillation frequency of the voltage-controlled oscillating means for determining a carrier frequency of a modulated wave or a received FM modulated wave; and a low-pass filtering means for receiving an output of the synthesizer as an input and deriving the output as a control voltage of the voltage-controlled oscillating means. And an FM transmitting / receiving apparatus characterized by including the following.

[0017]

The VCO is used as a direct FM modulator during transmission, as a local oscillator of a phase locked loop type FM demodulator during reception, and the oscillation frequency of the VCO is controlled by the output of a frequency synthesizer for varying the carrier wave of the transmission / reception wave. It is configured to control.

At this time, at the control input section of the VCO, a high-pass filter and a low-pass filter are provided to separate a control input for FM modulation and demodulation at the time of transmission and reception and a control input of a frequency synthesizer for variable carrier. Add a bandpass filter. When a control input (baseband signal) for FM modulation and demodulation during transmission and reception is applied as a VCO control input through a high-pass filter and a control voltage of the frequency synthesizer through a low-pass filter, A single VCO allows the FM modulator and demodulator to be used together with a variable local oscillator with a frequency synthesizer.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and the same parts as those in FIGS. 3 and 4 are denoted by the same reference numerals.
In this example, the VCO 1 that oscillates at a carrier frequency or a frequency that is a fraction of the carrier frequency is used as an FM direct modulator during transmission, and is used as a local oscillator of a phase locked loop type FM demodulation circuit during reception. The signal output of the VCO 1 is branched into two, one is input to a phase locked loop frequency synthesizer circuit 8 for carrier frequency control, one is frequency-multiplied by an integer-multiplier frequency multiplier 4, and after another two branches, one is high-frequency The power is supplied to the antenna 14 via the power amplifier 10, the bandpass filter 11 and the high-frequency switch 13, and becomes a transmission high-frequency signal.

The high-frequency signal received by the antenna 14 is input to the frequency mixer 5 through the band-pass filter 12, the high-frequency amplifier 15, and the amplitude controller 16. The control terminal of the VCO 1 is transmitted from the baseband signal input terminal 17 at the time of transmission via the high-pass filter 2 via the high-pass filter 2 and passed through the low-pass filter 9, and output from the frequency mixer 5 at the time of reception. The demodulated signal that has passed through the low-pass filter 6 is applied via the baseband switch 7.

At the same time, an output control signal of the phase locked loop frequency synthesizer circuit 8 is applied to the control terminal of the VCO 1 via the low-pass filter 3.

The lower limit frequency f0 of the baseband signal to be transmitted is a binary FSK (Frequency Shif).
T Keying) transmission can be roughly evaluated as f0 = k / 2 ⁿ (1). Here, k is the number of bits transmitted (received) per second (bps), and n indicates the number of stages of the scramble pattern.

The relationship between the lower limit cutoff frequency f2 of the high-pass filter 2, the upper limit cutoff frequency f3 of the low-pass filter 3, and the lower limit frequency f0 of the baseband signal of the equation (1) is as shown in FIG. Shall be selected. That is, f3 <f2 <f0, and f2 and f3 are set to 1/10 to 1/100 of f0.

The baseband signal input from the input terminal 17 is passed through the low-pass filter 9 and the switch 7 to the high-pass filter 2.
To the VC without any loss of signal information
Applied to O1. The output signal of the VCO 1 is frequency-modulated and becomes a transmission output after integer multiplication.

The received signal is transmitted from the antenna 14 to the bandpass filter 1.
After being amplified by the high-frequency amplifier 15 through 2, the amplitude is limited and input to the frequency mixer 5. A part of the local oscillation signal obtained by multiplying the output of the VCO 1 by an integer is also input to the frequency mixer 5.

The frequency mixer 5 generates an error voltage corresponding to the phase difference of the input high-frequency signal, and after the band is limited by the low-pass filter 6, the VCO passes through the switch 7 and the high-pass filter 2.
1 to form a phase locked loop type FM demodulation circuit. A part of the signal input to the switch 7 is branched and becomes a demodulated output.

Since the lower cutoff frequency of the high-pass filter 2 is sufficiently lower than the lower limit frequency of the baseband signal, the information of the demodulated output is not damaged at all. Since the signal from the phase locked loop frequency synthesizer circuit 8 for controlling the carrier frequency is also applied through the low-pass filter 3, the baseband component of the control voltage applied to the VCO 1 may be damaged. Absent.

That is, the high-pass filter 2 and the low-pass filter 3 perform the modulation / demodulation operation of the signal applied to the control terminal of the VCO 1 and carry out the branch of the frequency control range.

[0030]

As described above, according to the present invention, the low frequency filter is connected to the frequency control terminal of the VCO which is shared as the local oscillator of the phase locked loop type demodulation circuit during reception as the FM modulator during transmission. A frequency divider comprising a high-pass filter;
The control signal applied to the CO is branched into a band required for FM modulation and demodulation and a band required for carrier frequency control, so that the VCO, the modulator at the time of transmission, and the local oscillator of the demodulation circuit at the time of reception can be used together as described above. There is also an effect that a frequency synthesizer function is also provided to facilitate changing the carrier frequency.

Further, as compared with the conventional embodiment in which the modulation / demodulation VCO and the carrier generation VCO are independently provided as in the conventional embodiment shown in FIG. 4, the configuration of the apparatus can be simplified, and the size and cost can be easily reduced. is there.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between characteristics of a high-pass filter 2, characteristics of a low-pass filter 3, and a lower limit frequency of a baseband signal.

FIG. 3 is a block diagram showing an example of a conventional FM transmitting / receiving apparatus.

FIG. 4 is a block diagram showing another example of the conventional FM transmitting / receiving apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 VCO 2 high-pass filter 3, 6, 9 low-pass filter 4 frequency multiplier 5 frequency mixer 7, 13 switch 8 PLL circuit 10, 15 high-frequency amplifier 14 antenna 16 amplitude limiter 17 transmission baseband signal input Terminal 18 Receive baseband signal output terminal

Claims (4)

(57) [Claims] 1. A voltage-controlled oscillating means to which a transmission baseband signal is applied as a control voltage during transmission and an FM demodulated baseband signal as a control voltage during reception, and an output of the voltage-controlled oscillation means as a transmission FM modulated wave during transmission. Transmitting means, and receiving the output of the voltage controlled oscillating means at the time of reception.
Receiving means for frequency-mixing the M-modulated wave and deriving a low-frequency component of the mixed output as the FM demodulated baseband signal, wherein the transmission baseband signal is transmitted during transmission, and the FM is transmitted during reception. High-pass filtering means for inputting a demodulated baseband signal as a control voltage of the voltage-controlled oscillating means, and an oscillation frequency of the voltage-controlled oscillating means for determining a carrier frequency of the transmission FM modulation wave or the reception FM modulation wave. And a low-pass filter that receives an output of the synthesizer as input and derives it as a control voltage of the voltage-controlled oscillator. 2. A transmission / reception antenna, first selection means for selectively deriving a transmission baseband signal and an FM demodulation baseband signal, and high-pass filtering means having a selection output of the selection means as an input. A voltage-controlled oscillating means having the output of the high-pass filtering means as a control input, and determining whether to supply an oscillation output of the voltage-controlled oscillating means to the transmitting / receiving antenna or to derive a received FM modulated wave from the transmitting / receiving antenna. 2nd to choose
Selecting means, and the reception FM by the second selecting means
Means for frequency-mixing the modulated wave and the output of the voltage-controlled oscillating means to derive a low-frequency component thereof as the FM demodulated baseband signal; and determining a carrier frequency of the transmission FM modulation wave or the reception FM modulation wave. F. A synthesizer for determining an oscillation frequency of the voltage controlled oscillator, and a low-pass filter for receiving an output of the synthesizer as input and deriving the output as a control voltage of the voltage controlled oscillator.
M transceiver. 3. A lower cutoff frequency of the high-pass filter and an upper cutoff frequency of the low-pass filter are both set sufficiently lower than a lower limit frequency of the baseband signal. The FM transceiver according to claim 1 or 2. 4. The FM transceiver according to claim 3, wherein an upper cut-off frequency of the low-pass filter is set lower than a lower cut-off frequency of the high-pass filter.