JPH0422370B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a wireless communication device of a simultaneous transmission and reception type in which the transmission frequency and the reception frequency are different and the frequency is set to a constant value depending on the channel used.

Conventional configuration and its problems Figure 1 shows how a telephone exchange is accessed via a base radio station, and telephone calls can be made by dialing to a telephone subscriber of a wired telephone network or wireless telephone system by simultaneous transmission and reception. This figure shows an example of a wireless telephone. The configuration of this conventional example will be explained below with reference to FIG. 1.

In FIG. 1, 1 is an antenna, 2 is a duplexer (DUP), and 3 is a first frequency converter C. If necessary, a pre-reception amplifier may be added. 4 is a bandpass filter (BPF), 5 is a second frequency converter (C), 6 is a second local oscillator 0, and 7 is a bandpass filter (BPF). Selection filters are used that provide excellent selection characteristics and attenuate adjacent channel frequencies by several tens of dB to 100 dB. 8 is an IF amplifier, which has a relatively wide band and high gain, and has a built-in limiter that limits the output to a constant amplitude. Also, IC circuits that output the level of the input signal as received information and have a built-in noise squelch circuit and frequency converter are generally used. 9 is an IF frequency signal detector (DET);
This is sometimes built into the IC of the IF amplifier 8. In the IF amplifier 8, a is an analog signal output section for call voice, etc., and b is a digital signal output section for control data, etc. In the case of a multi-channel switching car phone, it outputs an individual ringing signal, a channel switching signal, a transmitter, and a handset. , OFF signal, etc., which differ depending on each system, are output as digital signals to a controller (CONT) 26, which will be described later.
10 is an analog signal amplifier, 11 is the handset ON,
The OFF switch 12 is a telephone receiver, which is shown built into the handset. This handset is displayed with the assumption that it will operate as a ringer speaker that generates the ringing tone when it is called by the base station, but of course it is also possible to install a separate speaker in addition to this handset to amplify the ringing tone, or to use a hands-free Another method is to use a speaker for calls. Reference numeral 13 is a number dialing unit that sends the called party number to the base station.In addition to this, it also stores the dialed number in memory, sends out pre-stored numbers, and allows so-called hands-free calling, which allows calling without lifting the handset. This comprehensively represents various control switches (herein referred to as function buttons) such as ON and OFF switches when performing operations. Reference numeral 14 denotes a transmitter built into the handset, and the function button 14 collectively represents a hands-free icrophone installed elsewhere. Reference numeral 15 is a so-called hand switch (HS), which is turned on and off by lifting the handset from the stand, and is represented by a mechanical switch, but this is a switch that operates electromagnetically or optically. This is a comprehensive diagram and is sent as ON/OFF information to the controller 26, which will be described later.
16 turns on the analog signal from the transmitter 14,
It is a switch that turns OFF, and the answer switch 1
1 and is controlled by a controller 26. The above-mentioned units 11 to 16 are generally referred to as mobile telephones, and are often housed in one unit. Reference numeral 17 denotes an analog signal processor that processes the audio signal from the transmitter 14 according to the characteristics of the audio. This expression includes instantaneous deviation limiters (IDCs), etc. that prevent variable tuning. The compressor is operated as a paired expander with the expander of the analog amplifier 10. 18 is the modulator M ₀ and 19 is the oscillator 0. These do not exist independently, but are often combined as a whole, and the order in which they are displayed is also (M ₀ -0).
or (0-M ₀ ) is a comprehensive representation of modulation devices of various modulation formats.
A frequency converter (C) 20 mixes the frequency _S of a frequency synthesizer (SYNTH) 25, which will be described later, and the frequency _t of the oscillator 19, and converts the mixture into a transmission frequency _T. Reception frequency _R and transmission frequency
Depending on the magnitude of _T , (+) of ( _T = _S ± _t )
Or selected (-). 21 is a bandpass filter (BPF). When the number of switching channels is from several hundred to several thousand channels, the frequency synthesizer 25 uses the band _B , where the channel interval _{is c} and the number of channels is N _{c .}
=N _c・_c . Furthermore, when _c = 25KHz and N _c = 1000, the band _B used is a wide band of 25MHz. The bandpass filter 21, which reduces the spurious caused by the combination of the frequency _S of the frequency synthesizer 25 and the frequency of the oscillator 19 to about -70 dB with respect to one transmission frequency, is required to have a wide band and sharp selectivity, and is large in size. In addition, small-sized devices have a large insertion loss. 22 is a preamplifier that provides a high frequency output necessary for exciting the power amplifier 24. 2
3 is a transmission noise suppression filter (BPF) for the reception band, and 24 is a final stage power amplifier, which requires an output of 5 or 10 W for a car phone and about 1 W for a mobile phone. This power amplifier 24 is integrated into an IC, and can obtain 5 or 10 W with excitation of several tens of mW, and can automatically reduce the transmission output in multiple stages according to the receiving input level, and can Some have functions such as lowering the transmission output based on a control signal from the side. 25 is a frequency synthesizer whose frequency is locked to a stable and highly accurate oscillator, which generates frequencies of hundreds to thousands of channels according to instructions from the controller 26, and transmits this to the first receiver's It is used as a local oscillation and transmission frequency. 26 is a controller for the radio, which receives various control signals from the base station, sends response signals to the base station, and controls the operation of the radio, such as transmitting output based on the reception level and instructions from the base station. control of,
Various control functions are provided for connection of the in-vehicle telephone.

As explained above, the frequency synthesizer 25
When a band filter 21 with a wide band and high selectivity is used to synthesize the transmission frequency _T from the oscillator 19, the band filter 21 becomes large, which is a hindrance and drawback in downsizing the radio device.
Further, since the insertion loss increases when the filter 21 is made smaller, there is a drawback that an excitation amplifier 22 is required. Furthermore, since the input to the excitation amplifier 22 is lowered, a bandpass filter is required to reduce transmitter noise at the receiving frequency _R due to c/N deterioration.

Purpose of the Invention The present invention eliminates the drawbacks of the above conventional example, and by changing the circuit configuration of the transmitter, a transmitting oscillator, modulator, frequency converter, band filter, excitation amplifier, band limiting filter, etc. The purpose of this invention is to simplify, downsize, and make the radio equipment economical by eliminating the

Structure of the Invention In order to achieve the above object, the present invention uses the transmission frequency as the local oscillation frequency of the receiver, and sets the first intermediate frequency _I as the difference frequency ( _I = _T − _R ) between the transmission frequency _T and the reception frequency _R. There is. Furthermore, the transmission frequency _T is directly modulated by a frequency synthesizer, and the power is amplified to provide the transmission output. On the other hand, modulation equivalent to the transmission frequency _T is applied to the second station oscillator to cancel the modulation component of the local transmitter that occurs at the first intermediate frequency. This makes it possible to eliminate the transmitting oscillator, frequency converter, bandpass filter, excitation amplifier, and bandlimiting filter, thus simplifying the radio equipment.
This has the effect of making it possible to downsize and become more economical.

DESCRIPTION OF EMBODIMENTS The configuration of an embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, parts 1 to 26 using the same numbers as in FIG. 1 have the same functions as in FIG. In FIG. 2, a transmitting oscillator 19, a frequency converter 20, a band filter 21,
The excitation amplifier 22, band-limiting filter 23, etc. are not necessary and are therefore removed. On the other hand, the modulation signal is distributed to both the modulator 18 of the second local oscillator 6 and the frequency synthesizer 25 by a branch circuit 27 in order to give equal amplitude modulation to both.

Hereinafter, the configuration and operation of the present invention will be explained using FIG. 2.

25 is a frequency synthesizer that oscillates a transmission frequency _T , which oscillates a carrier frequency having a channel interval of _c and a channel number _Nc according to instructions from a controller 26, and its output is several tens of mW. This output is branched into two by a branch circuit 28, one of which is supplied to the power amplifier 24 via a switch circuit. The other one is supplied to the frequency converter 3 of the receiver as the first local frequency. A power amplifier 24 amplifies or attenuates the excitation power from the synthesizer 25 and outputs it from the antenna duplexer 2 to the antenna 1, from which radio waves are radiated. Furthermore, the power amplifier 24 has a built-in directional coupler and a level comparator provided on the output side, and compares the reference voltage E _cp of the controller 26 with the forward power E _f of the directional coupler and transmits the result. A function is provided to adjust the output to a reference level.

The audio signal from the transmitter 14 is sent to the signal switch 16.
is applied to the modulation signal controller (IDC) 17 via the output signal controller (IDC) 17, which performs at least peak limiting and unnecessary wave removal among level compression, audio peak limiting, and unnecessary wave removal, and outputs one output a of the branch circuit 27. is added to the self-excited oscillation section of the frequency synthesizer 25, giving FM modulation or PM modulation of ( _S ±Δ) to the output of the frequency synthesizer 25. The other output b of the branch circuit 27 is applied to the modulation circuit 18 of the second local oscillator 6. The second local oscillator 6 is, for example, a crystal oscillator, and may be of a type in which a variable capacitance diode is used as the load capacitance, and the frequency is changed by applying a modulation signal to the variable capacitance diode. This gives a modulation of ( _L ±Δ) to the second local oscillation frequency _L. modulation signal _n
Whether it is ( _L ±ΔF) or ( _L 〓ΔF) depends on the magnitude of the transmitting and receiving frequency, whether ( _T > _R ) or ( _T <
_R ).

Next, the condition ( _T > _R ) will be explained. Reception frequency _R , frequency of frequency synthesizer 25
The relationship among _S , transmission frequency _T , and first intermediate frequency _I is as follows.

(When both transmitting and receiving waves are unmodulated) _I = _S − _R = _T − _R ∵ _S = _T (When _T is unmodulated and _R is modulated) _S − ( _R ±Δ) = ( _I 〓Δ) ( _T modulation , _R non-modulation) ( _S ±Δ) − _R = ( _I ±) ( _T modulation, _R modulation) ( _S ±Δ ₁ ) − ( _R ±Δ ₂ ) = ( _I ±Δ ₁ 〓Δ ₂ ) becomes.

When connecting from a base station exchange to a general wired telephone network, the modulation level is reduced by the telephone line loss.
The standard telephone system loss is when there are 4 lines up to the toll office.
12.5dB, -16dB if there are 4 wires to the center station,
The base station switch compander reduces this loss by approximately 1/
2, and Δ becomes a smaller value by −6.25 dB and −8 dB.

At the output of frequency converter 3, the receiving frequency _R
If both the transmission frequency _T or _S are modulated and the line loss is −12.5 dB, the composite Δ is the average value.
It becomes 1224 times. Further, in the case of line loss of -16 dB, the average value of the composite Δ is 1063 times. Therefore, ΔF=
The composite Δ in case of 5KHz is 7.35KHz ~ at peak value
5.8KHz, average value is 6.12KHz to 5.32KHz. Here, the band filter 4 attenuates the carrier wave component of the adjacent channel by about 20 dB, and the degree of attenuation at the ±12 KHz detuning point is only about 1.5 dB. is not extremely attenuated and there is no problem with the composite Δ. In addition, in the case of a telephone line, if both parties talk freely at the same time, it is impossible to understand what the other party is saying, so according to the telephone line load theorem, the actual time spent talking is 1/2 of the total, and both parties talk the same amount of time. If the call is made, it is 1/2 of that time, and it can be seen that a true simultaneous call is an extremely short time when the conversation ends. Therefore, it is only necessary to know what kind of phenomenon is caused by the modulation signal of the transmitter of the own station.

When ( _S ±Δ ₁ ) is added to the transmission frequency ( _T = _S ), the output of frequency converter 3 is ( _S ±Δ ₁ ) − _R = ( _I
±ΔF ₁ ), is added to the second frequency converter 5, and is converted to the second IF _i by the second local frequency ( _I ±ΔF ₂ ). ΔF ₁ = ΔF ₂ , if _I > _L , ( _I ±
ΔF ₁ ) − ( _L ±ΔF ₂ ) = _i , if _I < _L , ( _L
±
Δ ₂ ) − ( _I ±Δ ₁ ) = _i , and the second IF _i has the transmitted wave
The modulation components included in _T are canceled and not output.

However, in reality, the frequency synthesizer 25 and the second
Due to the difference in modulation characteristics between the local oscillator 6 and the modulator 18 and the level setting error, a component Δ (Δ ₁ −Δ ₂ =Δ) that cannot be canceled is generated. The sidetone level of general telephones is said to be -12 to -15 dB, and it is said that it is sufficient to maintain Δ at (Δ ₁ /10), that is, about -20 dB. The component Δ is outputted from the detector 9 to the audio amplifier and expanded by a built-in expander, so that the relative signal level ratio is doubled, and the -20 dB component is lowered in level to -40 dB. When an expander is used, the degree of signal cancellation by the second frequency converter 5 may be about -10 dB.

If no expander is included after the detector 9, it is sufficient to set the remaining component Δ of the cancellation to about -20 dB, and it is possible to maintain this value without difficulty.

Although the above description has been made regarding a car telephone type radio device, the same effect can be obtained by using it in a simultaneous transmitting/receiving radio device in which the transmitting/receiving frequency is kept at a constant value. Also,
Although a relatively wideband radio device has been described for mobile communication, similar effects can be obtained with a narrowband communication radio device.

Effects of the Invention The present invention has the above-described configuration, and provides the following effects.

(1) The modulated transmission frequency can be used as the first local oscillation frequency of the receiver, eliminating the need for frequency converters, bandpass filters, amplifiers, etc.
It is advantageous for simplifying, downsizing, and economical circuits.

(2) As the transmission frequency uses the output of the frequency synthesizer at a high level, the C/N is large,
Therefore, the improvement effect of reducing transmitter noise in the receiving frequency band is also significant.

(3) Since the second local frequency signal is modulated independently so that it has almost the same frequency deviation as the first local frequency signal, mixers, multipliers, and BPFs are not required in the transmitting circuit. This has the effect of downsizing.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional wireless communication device for mobile communication, and FIG. 2 is a block diagram showing an embodiment of the wireless communication device for mobile communication according to the present invention. 1...Antenna, 2...Antenna joint device, 3,
5, 20...Frequency converter, 4, 7, 21, 23
...bandwidth filter, 6,19...local oscillator,
8, 10, 22, 24...Amplifier, 9...Signal detector, 11, 16...ON, OFF switch, 12
...Telephone receiver, 13...Number dial section, 14...
Transmitter, 15... Hook switch, 17... Analog signal processor, 18... Modulator, 25... Frequency synthesizer, 26... Controller.

Claims (1)

[Claims] 1 Used in a radio telephone that makes a call via a base station radio station, the base station compresses the level with a compressor and transmits it, and the radio telephone stands by and receives it, and transmits and receives it to and from the base station. When performing simultaneous transmission and reception using different frequencies, a modulation signal is used to give a frequency shift to the first local oscillation frequency of the dual superheterodyne receiver of the radio telephone to obtain a transmission frequency, and this is also applied to the first local oscillation frequency of the receiver. means for converting the frequency into a first intermediate frequency by injecting it as a single local oscillation frequency; means for converting the frequency from the first intermediate frequency to a second intermediate frequency; means for substantially canceling out the modulation component of the transmitter by independently applying a shift to a second local oscillator and converting it to a second intermediate frequency; and means for detecting the second intermediate frequency and expanding the level with an expander. A wireless communication device configured to receive a desired reception frequency.