JPH10145262A - Dual band vco - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dual band VCO(voltage controlled oscillator) which is shared in a transmitting and receiving circuit of a portable telephone system in which frequencies are very different. SOLUTION: A resonance frequency of a VCO is switched, and a different frequency is oscillated and also higher harmonic waves of the other frequency is utilized as a mixed frequency in a mixer. In the case of a PDC(personal digital cellular) and a PHS(personal handyphone system) in the 800MHz band, the oscillation frequency of the VCO is switched between 680 to 696MHz and 825.5 to 837MHz bands, and the oscillation frequency of 1651 to 1674MHz 2nd higher harmonic wave of the 825.5 to 837MHz is outputted to the mixer. An output to a frequency-converting circuit at the time of transmission is similar.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a VCO (Voltage Controlled Oscillator) for use in a transmission / reception circuit of a portable telephone which can be used in two communication systems having greatly different frequencies. For a dual-band VCO.

[0002]

2. Description of the Related Art With the development of mobile communication technology, communication technologies using various mobile phones have been developed and put into practical use.
Some of these methods differ greatly, but others have almost the same method except for the frequency band and the filter configuration used therefor.

For example, an 800 MHz band PDC (Personal Digit)
al Cellular) and PHS (Personal Handyphone System) are both digital systems, generally using a double superheterodyne system, and have almost the same circuit configuration. However, the frequency band used is very different, PDC is in the 8-9 hundred MHz band, and the reception frequency is 810-82 MHz.
6MHz, transmission frequency is 940 ~ 956MHz,
HS uses a frequency of 1895-1918 MHz in the 1.9 GHz band.

Accordingly, the first intermediate frequency of the PDC is set to 13
Assuming that the first intermediate frequency of 0 MHz and PHS is 244 MHz, the first local oscillation circuit uses a VCO that oscillates at 680 to 696 MHz for PDC and a VCO that oscillates at 1651 to 1674 MHz for PHS. These frequencies are 2.4 times apart, and it has not been possible to share a VCO and a PLL using the same when manufacturing a mobile phone that can be used in both modes. This is because stable oscillation cannot be obtained simply by switching the resonance inductance or the resonance capacitance while maintaining the circuit constant of the VCO.

[0005]

SUMMARY OF THE INVENTION The present invention provides a transmission / reception circuit that can be used in portable telephone systems having greatly different frequency bands, such as a PDC in an 800 MHz band and a PHS in a 1.9 GHz band. And a dual-band VCO obtained by operating the VCO so that the PLL can be shared with the VCO of the local oscillation circuit. As a result, the number of circuit elements is reduced, and low power consumption, small size, light weight, and low cost of the mobile phone are realized.

[0006]

The present invention solves the above-mentioned problem by using a fundamental wave of one oscillation frequency and a harmonic of the other oscillation frequency of the VCO.

That is, in a dual-band VCO used in a receiving circuit of a portable telephone for receiving signals in two different frequency bands, one VCO switches and outputs each oscillation signal mixed with a reception signal by a mixer, It is characterized in that a harmonic of the oscillation frequency of the oscillator is used as one of the oscillation frequencies.

In a dual band VCO used in a transmission circuit of a portable telephone for transmitting signals in two different frequency bands, one VCO switches and outputs respective oscillation signals mixed with a transmission signal by a mixer. It is characterized in that a harmonic of the oscillation frequency of the oscillator is used as one of the oscillation frequencies.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Dual-band VC according to the present invention
If O is used, the first local oscillation circuit is shared between the transmission circuit and the reception circuit, and the filter unit is switched using one corresponding to each frequency band. V of the first local oscillation circuit
The CO and the PLL circuit including the CO are shared, and switch and use the oscillations of the frequencies corresponding to the two greatly different frequencies. For low frequency band, use the fundamental wave of VCO,
For a high frequency band, the harmonics of the VCO are used to output to the mixer.

For example, when used for PDC and PHS in the 800 MHz band, the PDC generates and uses a fundamental wave of 680 to 696 MHz in the VCO, and the PHS generates 825.5 to 837 MHz which is half the frequency of 1651 to 1674 MHz in the VCO. Use by oscillating with. The ratio between the center frequencies of the two oscillation frequency bands is about 1.2 times, and stable oscillation can be obtained only by switching the resonance inductance or resonance capacitance while keeping the circuit constant of the VCO constant.

In the above example, in the PDC, the lock frequency of the PLL operation is equal to the frequency injected into the first mixer. PH
In S, the PLL is locked at half the frequency to be injected into the first mixer to oscillate the VCO, and the first mixer performs frequency conversion by mixing with the second harmonic.

[0012]

1 shows a dual band VCO according to the present invention.
FIG. 2 is a block diagram showing a transmission / reception circuit of a mobile phone using
This shows an example of a circuit shared by an 800 MHz band PDC and a 1.9 GHz band PHS. The upper side of the figure shows the receiving circuit, and the lower side shows the transmitting circuit.

The signal received by the antenna 11 is input to the receiving circuit by the high frequency switch circuit 12, passes through the low noise amplifier 13, and a predetermined frequency is selected by the receiving RF filter 14. 810 ~ 826MHz for PDC, PHS for
Bandpass filters with passbands between 1895 and 1918 MHz are used, which are arranged in parallel and connected to only one by a switch.

The first mixer 15 performs frequency mixing, and in the PDC, an oscillation frequency of 680 to 696 MHz is input from the first local oscillator and mixed with the received signal. In PHS
165 which is the second harmonic of the fundamental wave with a frequency of 825.5 to 837 MHz
An oscillation frequency of 1 to 1674 MHz is input and mixed with the received signal. The operation of the first local oscillator will be described later in detail.

The output of the first mixer 15 is a first IF filter 16
Thus, an intermediate frequency of 130 MHz for PDC and 244 MHz for PHS can be obtained. Further, a second IF filter passes through the second mixer 17
18 provides a second intermediate frequency of 450 KHz or 10.8 MHz. The received signal processed in this way is input to the baseband signal processing unit 20 via the demodulator 19.

The transmission circuit includes a quadrature modulation circuit 27, a frequency converter 25, a filter 24 between transmission stages, and a power amplifier 23. The PDC is 260 MHz and the PHS is
The 244 MHz signal is mixed in the frequency converter 25 with the output of the first local oscillator. The oscillation frequency is the same as the above example,
The PDC is 680 to 696 MHz and the PHS is 825.5 to 837 MHz. The PHS uses the oscillation output of the second harmonic 1651 to 1674 MHz.

The frequency-converted signal is 940 to 956 MHz for PDC and 1895 for PHS by the filter 25 between transmission stages.
The signal is output as a signal of 11918 MHz and transmitted from the antenna 11 via the antenna amplifier 23. Switching between PDC and PHS is performed by switching the filter unit and the oscillator.

A dual band VCO according to the present invention used for a local oscillation circuit will be described. The frequency to be mixed by the mixer is 680 to 696 MHz for PDC and 1651 to 16 for PHS.
It is 74MHz. In the above example of the present invention, the PDC uses the fundamental wave of the oscillation frequency of the VCO, and the PHS uses the oscillation frequency of 1/2 of the above-mentioned frequency to input the second harmonic to the mixer.

That is, in the PHS, the VCO is 825.5 to 83
Oscillate with a fundamental wave of 7 MHz. The center frequency ratio of this oscillation frequency is about 1.2 times, and a VCO capable of oscillating in two bands can be obtained by switching the inductance or capacitance value while keeping the circuit constant of the VCO constant.

FIGS. 2 and 3 are circuit diagrams showing examples of a dual band VCO according to the present invention. FIG. 2 shows switching of the oscillation frequency by changing the line length of the microstrip MS of the microstrip resonator type VCO. Normal L Microstrip MS length L _A length L
_A tap is formed at position _B. By a control voltage V _T with the variable capacitance diode 1 is obtained so as to oscillate at 680 ～696MHz by changing the capacitance.

[0021] When used in a PHS line length by dropping from the tap point to ground by operating the switching diode 2 by the switch drive voltage V _SW becomes L _B. Changing the volume by V _T using variable capacitance diodes, in which so as to oscillate at 825.5 ~837MHz.

[0022] Although FIG. 3 is also one using a similar microstrip resonator line length of the microstrip MS is obtained by a constant, which was to switch the capacitance value of the parallel resonant circuit V _SW is there. The basic operation is no different from the case of the inductance switching described above.
Similarly, oscillation can be performed in two frequency bands.

Next, the dual band VCO according to the present invention
Will be described. PLL-IC
Has a pull-in operation range as shown in FIG. When the first oscillation frequency using the fundamental wave is Δf _A and the second oscillation frequency using the second harmonic is Δf _B , Δ
It is within f _A and delta f _B are both operating range, the second harmonic 2.DELTA. f _B of delta f _B is set to be outside the operating range. As a result, the fundamental wave and the second harmonic can be combined into one VCO and PLL-
It can be used using an IC.

For PDC and PHS, the above Δf _A is
680 ~696MHz, and the 825.5 ~837MHz Δ f _B, also this one has to be within the pull-in range of the PLL-IC,
If the 2Δf _B of 1651 to 1674 MHz is outside the pull-in operation range, the PDC can use the fundamental wave and the PHS can use the second harmonic. As a PLL-IC satisfying such a condition, “LMX2332” manufactured by National Semiconductor or the like can be used.

The present invention is not limited to the above example, but can be applied to other types of mobile phones and mobile phones of different frequency bands. It is also possible to use other harmonics such as the third harmonic or combine harmonics.

[0026]

According to the present invention, since the oscillation frequency band of the VCO can be made closer, there is provided a portable telephone which can share one VCO and PLL for two communication systems having greatly different frequencies by switching the inductance or capacitance. realizable.

Further, not only one PLL-IC can be used, but also a local oscillation circuit can be constituted by using only a low-cost PLL-IC for a low frequency.

Furthermore, according to the present invention, low power consumption, small size, light weight, and low cost of a dual band mobile phone can be easily achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a transmission / reception circuit of a mobile phone using a dual-band VCO according to the present invention.

FIG. 2 is a circuit diagram of an example of a dual band VCO according to the present invention.

FIG. 3 is a circuit diagram of another example of a dual band VCO according to the present invention.

FIG. 4 is an explanatory diagram of characteristics of a PLL-IC used in the present invention.

[Explanation of symbols]

 15: Mixer 25: Frequency converter MS: Microstrip line 1: Variable capacitance diode 2: Switching diode

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Katsuro Nakamura Inventor 828 Hinohara, Tamagawa-mura, Hiki-gun, Saitama Prefecture

Claims (6)

[Claims] 1. A dual-band VC used in a receiving circuit of a mobile phone for receiving signals of two different frequency bands.
In O, a dual-band VCO characterized in that one VCO switches and outputs respective oscillation signals mixed with a reception signal by a mixer, and uses a harmonic of the oscillation frequency of the oscillator as at least one oscillation frequency. 2. A dual-band VC used in a receiving circuit of a mobile phone for receiving signals of two different frequency bands.
In O, one VCO switches and outputs each oscillation signal mixed with a reception signal by a mixer, and uses a fundamental wave of the oscillation frequency of the oscillator as one oscillation frequency,
A dual band VC characterized by using a harmonic of another oscillation frequency of the oscillator as the other oscillation frequency.
O. 3. A dual-band VC used in a receiving circuit of a mobile phone for receiving signals of two different frequency bands.
In O, one VCO switches and outputs an oscillation signal having a different frequency to be mixed with a received signal by a mixer, and uses a fundamental wave of the oscillation frequency of the oscillator as one oscillation frequency and the oscillator as the other oscillation frequency. A dual band VCO using a harmonic of another oscillation frequency. 4. A dual-band VC for use in a transmission circuit of a mobile phone for transmitting signals in two different frequency bands.
In O, a dual-band VCO characterized by using one VCO to switch and output each oscillation signal mixed with a transmission signal by a mixer, and to use a harmonic of the oscillation frequency of the oscillator as at least one oscillation frequency. 5. A dual-band VC for use in a transmission circuit of a mobile phone for transmitting signals in two different frequency bands.
In O, one VCO switches and outputs each oscillation signal mixed with a transmission signal by a mixer, and uses a fundamental wave of the oscillation frequency of the oscillator as one oscillation frequency,
A dual band VC characterized by using a harmonic of another oscillation frequency of the oscillator as the other oscillation frequency.
O. 6. A dual-band VC for use in a transmission circuit of a mobile phone for transmitting signals in two different frequency bands.
In O, one VCO switches and outputs an oscillation signal having a different frequency to be mixed with a transmission signal by a mixer, uses a fundamental wave of the oscillation frequency of the oscillator as one oscillation frequency, and uses the oscillator as the other oscillation frequency. A dual band VCO using a harmonic of another oscillation frequency.