JPH05191302A - Radio transmitter - Google Patents

Abstract

PURPOSE:To obtain a radio transmitter able to send a signal at a different frequency band with simple configuration employing only one system of a PLL. CONSTITUTION:The transmitter is provided with a PLL (phase locked loop) 1 generating a signal at a 1st frequency band, an amplifier 21 amplifies an output signal of the said PLL and a transmission output at the 1st frequency band is obtained via a band pass filter 201. The output signal of the PLL 1 and a signal having a frequency being integral number of multiple of a frequency of a reference oscillator 3 obtained by a multiplier 4 are mixed by a mixer 5, a signal at a 2nd frequency band is obtained by a band pass filter 6, amplified by an amplifier 22 and a transmission output at a 2nd frequency band is obtained via a band pass filter 202. Thus, one set of the PLL and one VCO (voltage controlled oscillator) are enough to cope with plural frequency bands. Furthermore, since a signal at the 2nd frequency band is obtained by mixing with the signal resulting from multiplying an output of the reference oscillator 3, excellent frequency accuracy and stability are attained for a transmission output of any frequency band.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless transmitter capable of transmitting and receiving in two different frequency bands.

[0002]

2. Description of the Related Art In recent years, wireless devices have become smaller and more solid, and in particular, mobile wireless telephone devices typified by car phones and mobile phones are remarkably reduced in size and weight. Frequencies in the VHF band or the UHF band are usually used in these mobile radio telephone devices, and FM (frequency modulation) is mainly used as a radio wave modulation method. These transmitters were once several MH
A crystal oscillator having a frequency of 10 to 10 MHz is used, and the output of the crystal oscillator is multiplied by a required order to obtain a signal having a required transmission frequency. However, due to the progress of phase-locked loop (hereinafter abbreviated as PLL) technology, even in a transmitting device whose transmission frequency exceeds 1 GHz, a voltage controlled oscillator (hereinafter abbreviated as VCO) directly oscillates the transmission frequency. That is, a method of directly generating a signal of a required transmission frequency by a PLL is often used. In this case, the frequency variable range of the VCO is about several percent of the free-running frequency.
On the other hand, as a wireless telephone device capable of transmitting and receiving in two different frequency bands, for example, a cellular cordless telephone found in Japanese Patent Laid-Open No. 3-1621 has been proposed.

A conventional radio transmitter will be described below. FIG. 4 is a block diagram of a conventional wireless transmission device capable of transmitting in two frequency bands. In FIG. 4, reference numeral 1 is a first PLL that generates a transmission signal in the first frequency band, and includes frequency dividers 2 and 3, a phase comparator 4, a low-pass filter 5, and oscillation by the first frequency band. V designed to enable
Composed of CO6. Reference numeral 7 is a second PLL that generates a transmission signal in the second frequency band, and is P except that the VCO 8 is designed to be able to oscillate in the second frequency band.
It has the same configuration as LL1. Reference numeral 9 is an amplifier for amplifying the outputs of PLL1 and PLL7 to a required transmission power. Reference numeral 10 is a bandpass filter for suppressing unnecessary radiation other than the transmission frequency. 11 is PLL1 and PLL
A temperature-compensated crystal oscillator (hereinafter abbreviated as TCXO) is often used as the reference oscillator for supplying the reference frequency signal 7 in order to improve frequency accuracy and stability. 12
Is a voice processing circuit, which performs processing such as band limitation, amplitude limitation, or encoding in the case of performing digital communication on information to be transmitted, represented by a voice signal, and VC of PLL1.
It is input to the VCO 8 of O6 and PLL7 to perform frequency modulation.

The operation of the conventional radio transmitting apparatus configured as described above will be described below. The PLL 1 is constructed by a usual and well-known technique, and operates so that the output frequencies of the frequency dividers 2 and 3 match. That is, if the oscillation frequency of the reference oscillator 11 is fx, the frequency division ratio of the frequency divider 2 is M, and the frequency division ratio of the frequency divider 3 is N, the oscillation frequency of the VCO 6, that is, the output frequency f1 of the PLL 1 is become that way.

[0005]

[Equation 1]

However, it goes without saying that f1 is limited to the range within which the VCO 6 can oscillate. And PLL7
Works exactly the same. Therefore, different frequency bands are
In order to oscillate in each of L1 and PLL7, not only the frequency division ratio of each of the frequency dividers 2 and 3 is set to a desired value, but also the VCO 6 capable of oscillating a desired frequency band is set for each frequency band. Must be used. This constitutes a VCO 6 capable of oscillating in a wide band, and if a single VCO 6 tries to obtain signals in a plurality of frequency bands, the carrier-to-noise ratio (hereinafter abbreviated as C / N) generally deteriorates and transmission is performed. This is because spectrum noise is generated around the frequency, which is not practical.
As described above, the transmission signals emitted by the PLL1 and PLL7 are each amplified by the amplifier 9 and output to the outside such as the antenna through the bandpass filter 10.

On the other hand, in the wireless transmission device in the cellular cordless telephone seen in the above-mentioned Japanese Patent Laid-Open No. Hei 3-1621, as apparent from the configuration of FIG. Two systems are provided. That is, the configuration is such that two independent radio units having different frequency bands are simply combined.

[0008]

However, in the above-described conventional wireless transmission device in FIG. 4, two sets of PLLs are used.
Are required, and therefore two VCOs are required.
Therefore, there is a problem that the circuit scale becomes large, which hinders downsizing of the device. Further, since the VCO in the frequency band of several hundred MHz or more used by mobile radio such as a car phone is relatively expensive, the device becomes expensive. Further, in the conventional wireless transmission device in the cellular cordless telephone shown in JP-A-3-1621, since two independent wireless units are provided for two frequency bands, the circuit scale is also large, There is a problem that it is difficult to downsize the device.

It is an object of the present invention to solve the above problems and to provide a wireless transmission device capable of transmitting in a plurality of frequency bands with a simple structure.

[0010]

In order to achieve the above object, the present invention has a PLL for generating a first frequency band, an amplifier for amplifying a PLL output signal, and a multiplier for multiplying a reference oscillator output. A mixer for mixing the PLL output signal with the output of the multiplier, a bandpass filter for passing a second frequency band from the mixer output, and an amplifier for amplifying the output of the bandpass filter. ..

[0011]

According to the present invention, with the above configuration, the output signal of the PLL for generating the first frequency band and the signal of the frequency which is an integral multiple of the reference oscillator frequency are mixed, and the band pass for passing the second frequency band is passed. Since it is filtered by the filter, a signal in the second frequency band can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a radio transmitting apparatus according to an embodiment of the present invention. In FIG. 1, 13 is a PLL for generating a transmission signal in the first frequency band. PL
L13 is composed of frequency dividers 14 and 15, a phase comparator 16, a low pass filter 17, and a VCO 18 designed so that the first frequency band can oscillate, and PLL1 of FIG. 4 described in the conventional example.
Is similar to. Reference numeral 19 is a reference oscillator for supplying the reference frequency signal of the PLL 13, which is the same as that of FIG. 4 described in the conventional example. 20 is a multiplier, which is a reference oscillator 19
Is received, and this is frequency-multiplied. The multiplier 20 is usually composed of a bipolar transistor biased in class C or class B or a simple non-linear amplifier circuit of one field effect transistor. Reference numeral 21 denotes a mixer, which is the same as the frequency mixer used in a general superheterodyne receiver or the like. That is, it can be realized by a simple non-linear amplifier circuit of a bipolar transistor or a field effect transistor or a simple circuit of a diode and a transformer.
Reference numeral 22 denotes a bandpass filter, which selectively passes the second frequency band. Reference numeral 23 is a voice processing circuit, which is similar to that of FIG. 4 described in the conventional example. 24 and 25 are amplifiers for amplifying the first and second transmission signals to required transmission powers,
Reference numeral 26 is a bandpass filter for suppressing unnecessary radiation other than the transmission frequency.

The operation of the conventional radio transmitting apparatus configured as above will be described below. The PLL 13 operates in the same manner as the conventional example, and sets the oscillation frequency of the reference oscillator 19 to f
If x, the frequency division ratio of the frequency divider 14 is M, and the frequency division ratio of the frequency divider 14 is N, the output frequency f1 is given by the equation (1).

Here, f1 is clearly within the frequency range in which the VCO can oscillate, that is, within the range of the first frequency band.
Therefore, the transmission signal in the first frequency band is amplified to a required output voltage by the amplifier 24, and is output to the outside such as the antenna through the bandpass filter 26. On the other hand, PL
A part of the output of L13 is mixed by the mixer 21 with the signal of the frequency of the integral multiple of the reference signal generator 19 multiplied by the multiplier 20. Therefore, if the multiplication order of the multiplier 20 is L, the output of the mixer 21 is f1, L · f.
in addition to x

[0016]

[Equation 2]

A frequency component of appears. Further, the band-pass filter 22 allows only a desired component of the first and second frequency bands, that is, the second frequency band to pass, is amplified to a required output power by the amplifier 24, and is output to the outside by an antenna or the like. To be done. Then, when transmitting the first frequency band, the power supply to the amplifier 25 is stopped, and when transmitting the second frequency band, the power supply to the amplifier 24 is stopped and only the desired frequency band is supplied. Send it. For example,
When the frequency fx of the reference oscillator 19 is 15.36 MHz, the first frequency band is 824 to 849 MHz, and the second frequency band is 902 MHz to 925 MHz, the multiplier 2
The degree of 0 is set to 5, and 5 is multiplied, and f1 is 825.2 MHz to 848.2 MH for the second frequency band.
The values of M and N in (Equation 1) may be set so as to be in the range of z (for example, M = 5 for the first frequency band).
12, 27467 ≤ N ≤ 28300, for the second frequency band, M = 512, 27507 ≤ N ≤ 28273,
If set by, the frequency can be set every 30 kHz within the above frequency band. ). At this time, the components of 749.4 MHz to 772.4 MHz and 902 MHz to 925 MHz appear from the expression (2) in the output of the mixer 21. And by the band pass filter 22, 902MHz ~ 925M
Only the Hz component is sent to the amplifier 25, amplified, and further output to the outside such as the antenna through the bandpass filter 26.

Next, another embodiment of the present invention will be described. FIG. 2 is a block diagram of a wireless transmission device according to another embodiment of the present invention. In FIG. 2, 13 is a PLL for generating a transmission signal in the first frequency band. PLL13
Is a frequency divider 14 and 15, a phase comparator 16, a low-pass filter 17, and a VC designed to oscillate the first frequency band.
It consists of O18. 19 is a reference oscillator, 20 is a multiplier, 2
Reference numeral 1 is a mixer, 22 is a bandpass filter, and 23 is an audio processing circuit, which are similar to those in FIG. 1 described in the embodiment. An amplifier circuit 24 is an amplifier that amplifies the first and second transmission signals to a required transmission power. When the first and second frequency bands are relatively close to each other, the amplifier can be shared by the two frequency bands as described above to further reduce the size. In the case where the antenna also shares the transmission output, power may be fed through a bandpass filter having passbands of the first and second frequency bands for suppressing unnecessary radiation. Further, in the case of using a dedicated antenna, power may be supplied via a bandpass filter for each frequency band as shown in FIG.

[0019]

As described above, according to the present invention, it is possible to realize a radio transmitting apparatus that is compatible with a plurality of frequency bands with one set of PLL and one VCO with a simple configuration. Moreover, since the signal of the second frequency band is obtained by mixing with the frequency oscillator that has good frequency accuracy and stability, the output of the second frequency band as well as the first frequency band is output. Also has good frequency accuracy and stability. Therefore, according to the present invention, it is possible to realize a wireless transmitter which is small and inexpensive and has high frequency accuracy and which is compatible with a plurality of frequency bands. Further, by sharing the amplifier in different frequency bands, it is possible to provide a wireless transmission device having various excellent features such as further miniaturization.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a wireless transmission device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a wireless transmission device according to a second embodiment of the wireless transmission device.

FIG. 3 is a block diagram showing a configuration of a wireless transmission device according to a third embodiment of the wireless transmission device.

FIG. 4 is a block diagram showing a configuration of a conventional wireless transmission device.

[Explanation of symbols]

 13 phase locked loop 14 frequency divider 15 frequency divider 16 phase comparator 17 low pass filter 18 voltage controlled oscillator 19 reference oscillator 20 multiplier 21 mixer 22 band pass filter 23 voice processing circuit 24 amplifier 25 amplifier 26 band pass filter

Claims (2)

[Claims] 1. A voltage-controlled oscillator configured by a phase-locked loop, the oscillation frequency of which changes according to the magnitude of an input voltage, and a frequency divider with a variable frequency division ratio for dividing an output signal of the voltage-controlled oscillator. An oscillator composed of a phase comparator which outputs an output according to the phase difference between the output of the frequency divider and a reference frequency signal, and a low pass filter which is connected to the input of the voltage controlled oscillator and filters the output of the phase comparator. A second oscillator connected to the phase comparator for emitting the reference frequency signal; a first amplifier connected to the first oscillator for amplifying an output of the first oscillator; A multiplier that multiplies the output of the oscillator, the output of the first oscillator, a mixer that mixes the output of the multiplier, a bandpass filter that filters the output of the mixer, and an output of the bandpass filter. Second And an amplifier, the first radio transmission device characterized by the output of the second amplifier, the transmission output of each different frequency bands. 2. A voltage controlled oscillator whose oscillation frequency changes according to the magnitude of an input voltage, a frequency divider with a variable division ratio for dividing an output signal of the voltage controlled oscillator, an output of the frequency divider and a reference frequency. A phase comparator which outputs an output according to a phase difference with a signal, and a first oscillator constituted by a phase-locked loop including a low-pass filter which is connected to an input of the voltage controlled oscillator and filters a phase comparator output, , A second oscillator connected to the phase comparator, which emits the reference frequency signal, a multiplier for multiplying an output of the second oscillator, an output of the first oscillator, and an output of the multiplier. A mixer, a bandpass filter that filters the output of the mixer, and an amplifier that amplifies the output of the bandpass filter and the output of the first oscillator, and the output of the amplifier as a transmission output. What to do Radio transmission apparatus according to claim.