JPS6248929B2 - - Google Patents
Info
- Publication number
- JPS6248929B2 JPS6248929B2 JP54035299A JP3529979A JPS6248929B2 JP S6248929 B2 JPS6248929 B2 JP S6248929B2 JP 54035299 A JP54035299 A JP 54035299A JP 3529979 A JP3529979 A JP 3529979A JP S6248929 B2 JPS6248929 B2 JP S6248929B2
- Authority
- JP
- Japan
- Prior art keywords
- intermediate frequency
- frequency
- frequency filter
- local oscillator
- filter
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Superheterodyne Receivers (AREA)
- Channel Selection Circuits, Automatic Tuning Circuits (AREA)
Description
【発明の詳細な説明】
本発明は、UHF帯などに使用される、スレシ
ヨールドレベルの低いFM用スーパーヘテロダイ
ン受信機に関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an FM superheterodyne receiver with a low threshold level, which is used in the UHF band and the like.
従来、周波数弁別器を備えたスーパーヘテロダ
イン受信機においては、局部発振器の周波数変動
を補正するために、自動周波数制御（AFC）を
行なうのが普通である。この方法は、周波数弁別
器の周波数安定度が局部発振器に比較して十分小
さいという点に着目して、周波数弁別器出力の直
流成分により局部発振器の周波数を補正する。こ
れにより、局部周波数と受信周波数の差の周波数
を常に中間周波フイルタの中心周波数とすること
ができる。 Conventionally, in a superheterodyne receiver equipped with a frequency discriminator, automatic frequency control (AFC) is usually performed to correct for frequency fluctuations of a local oscillator. This method focuses on the fact that the frequency stability of the frequency discriminator is sufficiently lower than that of the local oscillator, and corrects the frequency of the local oscillator using the DC component of the frequency discriminator output. Thereby, the frequency difference between the local frequency and the reception frequency can always be set as the center frequency of the intermediate frequency filter.
この方法において、中間周波フイルタの帯域を
決定するには局部発振器の周波数安定度を十分考
慮する必要がある。局部発振器の周波数安定度が
悪いと、中間周波フイルタの通過帯域幅は信号伝
送上必要な帯域幅より大きくなり、スレシヨール
ドレベルが高くなり、その結果感度が悪化する欠
点を有する。例えば、受信周波数800MHZ、温度
範囲―30℃〜60℃における水晶制御局部発振器の
温度偏差が±20×10-6とすると、局部発振周波数
の偏差は±16KHZとなる。また、信号伝送に必
要な帯域幅を6KHZとする。このとき、中間周波
フイルタに必要な帯域幅は最低32KHZと
（16KHZ×２）となる。 In this method, it is necessary to fully consider the frequency stability of the local oscillator in determining the band of the intermediate frequency filter. If the frequency stability of the local oscillator is poor, the passband width of the intermediate frequency filter becomes larger than the bandwidth necessary for signal transmission, and the threshold level becomes high, resulting in a disadvantage that sensitivity deteriorates. For example, if the reception frequency is 800 MHZ and the temperature deviation of the crystal-controlled local oscillator in the temperature range -30°C to 60°C is ±20×10 -6 , the local oscillation frequency deviation will be ±16 KHZ. Also, assume that the bandwidth required for signal transmission is 6KHZ. At this time, the bandwidth required for the intermediate frequency filter is at least 32 KHZ (16 KHZ x 2).
信号伝送には6KHZの帯域幅があれば十分であ
るが、局部発振器の周波数偏差を考えると
32KHZの帯域幅が必要となる。このときのスレ
シヨールドレベルの悪化量は、デシベルで表わす
と10log10（32×103／６×103）＝7.27dBとなる。 A bandwidth of 6KHZ is sufficient for signal transmission, but considering the frequency deviation of the local oscillator,
32KHZ bandwidth is required. The amount of deterioration of the threshold level at this time, expressed in decibels, is 10log 10 (32×10 3 /6×10 3 )=7.27 dB.
本発明の目的は、このような欠点を改善したス
ーパーヘテロダイン受信機を提供することにあ
る。 SUMMARY OF THE INVENTION An object of the present invention is to provide a superheterodyne receiver that overcomes these drawbacks.
本発明の特徴は、自動周波数制御を動作させる
には広い中間周波帯域幅が必要となるが、一担動
作すると、中間周波帯域幅は信号伝送に必要な帯
域幅であれば十分である点に着目したことにあ
る。 A feature of the present invention is that a wide intermediate frequency bandwidth is required to operate automatic frequency control, but once the automatic frequency control is operated, the intermediate frequency bandwidth required for signal transmission is sufficient. This is what we focused on.
以下、図により説明する。 This will be explained below using figures.
第１図は本発明の一実施例である。図におい
て、空中線１でとらえられた受信波は混合器２に
供給される。混合器２は、受信波を局部発振器３
からの局発振号と混合し、中間周波信号を得る。
フイルタ切替器１１および１２は、制御部１０か
らの信号により中間周波フイルタ１３と１４を切
替える。中間周波フイルタ１３の通過帯域幅は中
間周波フイルタ１４の通過帯域幅より広くなつて
いる。初期状態、すなわち、初めて受信波が到来
した場合、フイルタ切替器１１および１２により
中間周波フイルタ１３が選択されている。混合器
２の出力は、中間周波フイルタ１３を通つて中間
周波増幅器６で増幅され、周波数弁別器７に加え
られる。周波数弁別器７の出力は、低周波増幅器
８により増幅され受話器９に供給される。制御部
１０は、周波数弁別器７の出力から直流分を抽出
し、局部発振器３に加える。局部発振器３は、局
発周波数を補正し、中間周波信号に変換された受
信波が常に中間周波フイルタの中心になるように
動作する。さらに制御部１０は、受信波が中間周
波フイルタの中心、すなわち、周波数弁別器７の
中心周波数にあることを検出する。これは、周波
数弁別器出力の直流成分がある一定値、例えば、
OVとなつたことを検出することによる。制御部
１０は、検出信号をフイルタ切替器１１および１
２に供給することにより、中間周波フイルタ１３
を１４に切替える。一担、自動周波数制御、すな
わち、局発周波数と受信波の周波数との差が一定
周波数となる様に動作すると、受信波は常に中間
周波フイルタ１４の中心に位置することになる。
前述の如く、中間周波フイルタ１４の通過帯域幅
は１３の通過帯域幅に比較して狭いため、スレシ
ヨールドレベルが低くなる。受信波が低電界で、
中間周波フイルタ１３が選択されている場合、ス
レシヨールドレベル以下であつても、１４に切替
えたときスレシヨールドレベル以上であれば、低
周波出力のＳ／Ｎは大幅に改善される。さらに通
過帯域が狭くなる為、隣接する妨害波に対しても
効果が大きい。 FIG. 1 shows an embodiment of the present invention. In the figure, a received wave captured by an antenna 1 is supplied to a mixer 2. The mixer 2 converts the received wave into a local oscillator 3.
is mixed with the local oscillation signal from the oscillator to obtain an intermediate frequency signal.
Filter switchers 11 and 12 switch between intermediate frequency filters 13 and 14 in response to a signal from control section 10 . The passband width of the intermediate frequency filter 13 is wider than that of the intermediate frequency filter 14. In the initial state, that is, when a received wave arrives for the first time, the intermediate frequency filter 13 is selected by the filter switchers 11 and 12. The output of the mixer 2 passes through an intermediate frequency filter 13, is amplified by an intermediate frequency amplifier 6, and is applied to a frequency discriminator 7. The output of the frequency discriminator 7 is amplified by a low frequency amplifier 8 and supplied to a receiver 9. The control unit 10 extracts a DC component from the output of the frequency discriminator 7 and applies it to the local oscillator 3. The local oscillator 3 corrects the local oscillator frequency and operates so that the received wave converted into an intermediate frequency signal is always at the center of the intermediate frequency filter. Further, the control unit 10 detects that the received wave is at the center of the intermediate frequency filter, that is, at the center frequency of the frequency discriminator 7. This means that the DC component of the frequency discriminator output has a certain constant value, e.g.
By detecting that it has become OV. The control unit 10 transmits the detection signal to the filter switching devices 11 and 1.
2, the intermediate frequency filter 13
Switch to 14. First, when automatic frequency control is performed, that is, when the frequency difference between the local oscillation frequency and the frequency of the received wave is maintained at a constant frequency, the received wave is always located at the center of the intermediate frequency filter 14.
As described above, since the passband width of the intermediate frequency filter 14 is narrower than that of the intermediate frequency filter 13, the threshold level is low. When the received wave is in a low electric field,
When intermediate frequency filter 13 is selected, even if it is below the threshold level, if it is above the threshold level when switched to intermediate frequency filter 14, the S/N of the low frequency output is significantly improved. Furthermore, since the passband becomes narrower, it is also more effective against adjacent interference waves.
以上説明したように本発明によれば、たとえ局
部発振器の周波数偏差が大きくとも、スレシヨー
ルドレベルの低いスーパーヘテロダイン受信機を
得ることができる。 As described above, according to the present invention, a superheterodyne receiver with a low threshold level can be obtained even if the frequency deviation of the local oscillator is large.
第１図は本発明の一実施例を示す図である。
１……空中線、２……混合器、３……局部発振
器、６……中間周波増幅器、７……周波数弁別
器、８……低周波増幅器、９……受話器、１０…
…制御部、１１，１２……フイルタ切替器、１
３，１４……中間周波フイルタ。
FIG. 1 is a diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Antenna, 2...Mixer, 3...Local oscillator, 6...Intermediate frequency amplifier, 7...Frequency discriminator, 8...Low frequency amplifier, 9...Telephone receiver, 10...
...Control unit, 11, 12...Filter switch, 1
3, 14...Intermediate frequency filter.
Claims (1)
局部発振器の出力とを混合する混合器と、周波数
弁別器と、前記混合器と前記弁別器との間に設け
られた第１の中間周波フイルタおよび前記第１の
中間周波フイルタに比べて通過帯域の狭い第２の
中間周波フイルタと、前記周波数弁別器出力の直
流成分を検出する制御部と、前記制御部出力によ
り前記第１の中間周波フイルタと前記第２の中間
周波フイルタを切替える切替器とを含み、前記制
御部により前記局部発振器の周波数を制御すると
ともに、前記周波数弁別器出力の直流成分がある
所定の値になると前記第１の中間周波フイルタか
ら前記第２の中間周波フイルタに切替えることを
特徴とするスーパーヘテロダイン受信機。1 at least a local oscillator, a mixer for mixing an input signal and an output of the local oscillator, a frequency discriminator, a first intermediate frequency filter provided between the mixer and the discriminator, and the a second intermediate frequency filter whose pass band is narrower than that of the first intermediate frequency filter; a control unit that detects a DC component of the output of the frequency discriminator; a switch for switching a second intermediate frequency filter, the control unit controls the frequency of the local oscillator, and when the DC component of the frequency discriminator output reaches a certain predetermined value, the first intermediate frequency filter A superheterodyne receiver, characterized in that the superheterodyne receiver switches from the second intermediate frequency filter to the second intermediate frequency filter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3529979A JPS55127724A (en) | 1979-03-26 | 1979-03-26 | Superheterodyne receiver |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3529979A JPS55127724A (en) | 1979-03-26 | 1979-03-26 | Superheterodyne receiver |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS55127724A JPS55127724A (en) | 1980-10-02 |
| JPS6248929B2 true JPS6248929B2 (en) | 1987-10-16 |
Family
ID=12437892
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3529979A Granted JPS55127724A (en) | 1979-03-26 | 1979-03-26 | Superheterodyne receiver |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS55127724A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2768449B2 (en) * | 1990-03-01 | 1998-06-25 | 富士通株式会社 | Optical parallel data transfer method |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4312813Y1 (en) * | 1965-05-31 | 1968-06-01 | ||
| JPS4314649Y1 (en) * | 1968-02-15 | 1968-06-20 |
-
1979
- 1979-03-26 JP JP3529979A patent/JPS55127724A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS55127724A (en) | 1980-10-02 |
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