JPH10190509A - Microwave broadcasting reception circuit - Google Patents

Microwave broadcasting reception circuit

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Publication number
JPH10190509A
JPH10190509A JP34781596A JP34781596A JPH10190509A JP H10190509 A JPH10190509 A JP H10190509A JP 34781596 A JP34781596 A JP 34781596A JP 34781596 A JP34781596 A JP 34781596A JP H10190509 A JPH10190509 A JP H10190509A
Authority
JP
Japan
Prior art keywords
signal
local oscillation
level
circuit
agc
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.)
Pending
Application number
JP34781596A
Other languages
Japanese (ja)
Inventor
Osamu Shiraishi
修 白石
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NEC Corp
Original Assignee
NEC Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by NEC Corp filed Critical NEC Corp
Priority to JP34781596A priority Critical patent/JPH10190509A/en
Publication of JPH10190509A publication Critical patent/JPH10190509A/en
Pending legal-status Critical Current

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  • Television Receiver Circuits (AREA)
  • Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
  • Control Of Amplification And Gain Control (AREA)
  • Superheterodyne Receivers (AREA)

Abstract

PROBLEM TO BE SOLVED: To hold the input level of an FM demodulator fixed and to hold a fixed noise factor by setting the conversion gain of a frequency conversion circuit so as to perform an operation in a linear area changed in linear relation with the level of local oscillation signals. SOLUTION: When an applied voltage, that is an AGC voltage AG, is made larger, a current becomes larger and resistance becomes smaller. Inversely, when the voltage AG is made smaller, the resistance becomes larger. Thus, the level of the local oscillation signals LOT to be injected to a mixer 4 is raised by enlarging the voltage AG and the level of the local isolator LOT is lowered by making the voltage AG smaller inversely. Thus, by using the positive proportional area of the conversion gain GC and the level of the local oscillation signals LOT and varying the level of the local oscillation signals LOT by a local oscillation level varying circuit 3, the conversion gain of the mixer 4 is controlled. Also since the noise factor of the mixer 4 is decided by the noise factor of the respective bias states of constituting elements, it is turned to a stable value regardless of the conversion gain.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【0001】[0001]

【発明の属する技術分野】本発明はマイクロ波放送受信
回路に関し、特に衛星放送受信機等のマイクロ波帯の受
信信号を処理するマイクロ波放送受信回路に関する。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave broadcast receiving circuit, and more particularly to a microwave broadcast receiving circuit for processing a received signal in a microwave band such as a satellite broadcast receiver.

【0002】[0002]

【従来の技術】放送衛星(BS)の運用開始以来、この
BSからの放送電波を受信する衛星放送受信機(BS受
信機)が広く普及し、また近時通信衛星(CS)放送の
実用化に伴ない、このCS放送電波を受信するCS受信
機も普及しつつある。これらはいずれもKuバンドのマ
イクロ波帯を搬送波として用いるので、これらBS,C
S受信機は一般にアンテナ側にKuバンドからLバンド
に変換する周波数コンバータを備え、受信機本体(テレ
ビジョン受像機やVTR等)側にこのLバンドの変換信
号すなわち第1中間周波信号をUHFの第2中間周波信
号に変換し増幅復調するダブルスーパヘテロダイン方式
の受信回路を備える。
2. Description of the Related Art Since the start of operation of a broadcasting satellite (BS), satellite broadcasting receivers (BS receivers) for receiving broadcast waves from the BS have become widespread, and recently, practical use of recent satellite broadcasting (CS) has been realized. As a result, CS receivers for receiving the CS broadcast radio waves are becoming popular. Since all of them use the microwave band of the Ku band as a carrier, these BS, C
The S receiver generally includes a frequency converter for converting a Ku band to an L band on the antenna side, and converts the L-band converted signal, that is, the first intermediate frequency signal into a UHF signal on the receiver body (television receiver or VTR, etc.) side. A double superheterodyne receiving circuit for converting the signal into a second intermediate frequency signal and amplifying and demodulating the signal is provided.

【0003】従来のこの種の衛星放送受信機の本体側、
すなわち第1中間周波信号の処理回路であるマイクロ波
放送受信回路をブロックで示す図6(A)を参照する
と、この従来のマイクロ波放送受信回路は、アンテナ
(図示せず)の周波数コンバータから供給されるLバン
ドの第1中間周波信号すなわちRF信号ILを増幅しR
F増幅信号ALを出力する2段の低雑音増幅器1,2
と、AGC電圧AGの供給に応答してRF増幅信号AL
のレベルを次段のミキサの適正入力レベルに調整し信号
ATを出力する可変減衰器11と、レベル調整されたR
F増幅信号ATを局部発振信号LOと混合して周波数変
換し第2中間周波数(IF)信号Uを出力する周波数混
合器(ミキサ)4と、局部発振信号LOを発生しミキサ
4に供給する局部発振器5と、IF信号Uを増幅しIF
増幅信号UAを出力するIF増幅器6と、IF増幅信号
UAを所望の帯域特性に帯域濾波しフィルタIF信号U
Fを出力する表面弾性波(SAW)フィルタ7と、AG
C信号AGの供給に応答して利得が調整され信号UFを
増幅しIF出力信号UTを出力するAGC増幅器8と、
IF出力信号UTをFM復調してベースバンド信号Vを
出力するFM復調器9と、IF出力信号UTをAM検波
しAGC信号AGを出力するAGC検波回路10とを備
える。
[0003] The main body side of a conventional satellite broadcast receiver of this kind,
That is, referring to FIG. 6A, which shows a block diagram of a microwave broadcast receiving circuit which is a processing circuit for the first intermediate frequency signal, this conventional microwave broadcast receiving circuit is supplied from a frequency converter of an antenna (not shown). Amplifying the first intermediate frequency signal of the L band, ie, the RF signal IL,
Two-stage low-noise amplifiers 1 and 2 that output F-amplified signal AL
And the RF amplified signal AL in response to the supply of the AGC voltage AG.
A variable attenuator 11 that adjusts the level of the input signal to an appropriate input level of the next-stage mixer and outputs a signal AT;
A frequency mixer (mixer) 4 that mixes the F-amplified signal AT with the local oscillation signal LO to convert the frequency and outputs a second intermediate frequency (IF) signal U, and a local mixer that generates the local oscillation signal LO and supplies the same to the mixer 4 Oscillator 5 and IF signal U are amplified to IF
An IF amplifier 6 for outputting an amplified signal UA; and a filter IF signal U for subjecting the IF amplified signal UA to band-pass filtering to a desired band characteristic.
A surface acoustic wave (SAW) filter 7 for outputting F,
An AGC amplifier 8 whose gain is adjusted in response to the supply of the C signal AG to amplify the signal UF and output an IF output signal UT;
An FM demodulator 9 for FM-demodulating the IF output signal UT and outputting a baseband signal V, and an AGC detection circuit 10 for AM-detecting the IF output signal UT and outputting an AGC signal AG.

【0004】次に、図6(A)及びそのレベルダイアグ
ラムの一例を示す図6(B)を参照して、従来のマイク
ロ波放送受信回路の動作について説明すると、ビデオ・
音声信号をFM変調したBS/CSからのKuバンドの
放送信号を、アンテナ(図示せず)で受信しアンテナ内
の周波数コンバータでLバンドのRF信号ILに変換す
る。すなわちBSでは11.7〜12.0GHzから
1.03〜1.33GHZに、CSでは12.2〜1
2.75GHzから1.30〜1.88GHzにそれぞ
れ変換する。低雑音増幅器1,2はRF信号ILを増幅
しRF増幅信号ALを出力する。RF信号ILのレベル
は−65〜−20dBmと微弱であるので、典型的には
各12dBの利得を有する低雑音増幅器1,2は計24
dB増幅しRF増幅信号ALを後述の可変減衰器11を
介して信号ATとしてミキサ4に供給する。
Next, the operation of a conventional microwave broadcast receiving circuit will be described with reference to FIG. 6A and FIG. 6B showing an example of a level diagram thereof.
A Ku-band broadcast signal from a BS / CS obtained by FM-modulating an audio signal is received by an antenna (not shown) and converted into an L-band RF signal IL by a frequency converter in the antenna. That is, from 11.7 to 12.0 GHz in BS to 1.03 to 1.33 GHZ, and in CS from 12.2 to 1
Conversion from 2.75 GHz to 1.30 to 1.88 GHz, respectively. The low noise amplifiers 1 and 2 amplify the RF signal IL and output an RF amplified signal AL. Since the level of the RF signal IL is as weak as −65 to −20 dBm, the low-noise amplifiers 1 and 2 each having a gain of 12 dB typically have a total of 24 dB.
The amplified RF signal AL is supplied to the mixer 4 as a signal AT through a variable attenuator 11 described later.

【0005】ミキサ4は局部発振器5から局部発振信号
LOの供給を受け信号ATを周波数変換しUHF(40
2.75MHz)のIF信号Uを出力しIF増幅器6に
供給する。IF増幅器6はIF信号Uを一定利得で増幅
しIF増幅信号UAを出力し、SAWフィルタ7に供給
する。SAWフィルタ7はIF増幅信号UAを帯域フィ
ルタリングをし所定帯域特性のフィルタIF信号UFを
出力し、可変利得のAGC増幅器8に供給する。AGC
増幅器8はフィルタIF信号UFを増幅してIF出力信
号UTを出力し、FM復調器及びAGC検波回路にそれ
ぞれ供給するとともに、AGC信号の供給に応答してI
F出力信号UTのレベルが一定となるよう利得調整す
る。FM復調器9はIF出力信号UTをFM復調しビデ
オ信号や音声信号から成るベースバンド出力信号Vを出
力する。AGC検波回路10はIF出力信号UTをAM
検波し信号UTのレベルに対応するAGC信号AGを出
力する。
The mixer 4 receives the local oscillation signal LO from the local oscillator 5 and converts the frequency of the signal AT to UHF (40).
The IF signal U of 2.75 MHz) is output and supplied to the IF amplifier 6. The IF amplifier 6 amplifies the IF signal U with a constant gain, outputs an IF amplified signal UA, and supplies it to the SAW filter 7. The SAW filter 7 performs band filtering on the IF amplified signal UA, outputs a filtered IF signal UF having a predetermined band characteristic, and supplies the filtered IF signal UF to the variable gain AGC amplifier 8. AGC
The amplifier 8 amplifies the filter IF signal UF to output an IF output signal UT, and supplies the IF output signal UT to the FM demodulator and the AGC detection circuit.
The gain is adjusted so that the level of the F output signal UT becomes constant. The FM demodulator 9 FM-demodulates the IF output signal UT and outputs a baseband output signal V including a video signal and an audio signal. The AGC detection circuit 10 converts the IF output signal UT to AM
Detects and outputs an AGC signal AG corresponding to the level of the signal UT.

【0006】ミキサ4の利得は一般に固定であり、入力
RF信号ILのレベルが例えば−20dBmと高い場合
には後段のIF出力信号UTのレベルが大きくなりす
ぎ、FM復調器9の入力ダイナミックレンジに対応する
許容レベルを超えてしまい、歪の発生要因となってしま
う。このため、ミキサ4の入力側及びSAWフィルタの
出力側に利得調整用の回路として可変減衰器11及びA
GC増幅器8をそれぞれ備え、AGC信号AGにより可
変減衰器11の減衰量及びAGC増幅器8の利得をそれ
ぞれ調整しミキサ4への入力信号AT及びFM復調器9
への入力信号であるIF出力信号UTのレベルを一定範
囲内に保持する。
The gain of the mixer 4 is generally fixed. When the level of the input RF signal IL is as high as, for example, -20 dBm, the level of the IF output signal UT at the subsequent stage becomes too large and the input dynamic range of the FM demodulator 9 is reduced. Exceeding the corresponding allowable level may cause distortion. For this reason, the variable attenuator 11 and A are provided as gain adjustment circuits on the input side of the mixer 4 and the output side of the SAW filter.
A GC amplifier 8 is provided, and the amount of attenuation of the variable attenuator 11 and the gain of the AGC amplifier 8 are respectively adjusted by the AGC signal AG, so that the input signal AT to the mixer 4 and the FM demodulator 9
The level of the IF output signal UT, which is an input signal to the controller, is kept within a certain range.

【0007】可変減衰器11の構成例を回路図で示す図
6(C)を参照すると、この可変減衰器11は、入出力
インピーダンスが50Ω一定となるようπ型接続した3
個のPINダイオードD1〜D3から成り、AGC電圧
AGの供給に応答して減衰量が変化する。
FIG. 6C is a circuit diagram showing an example of the configuration of the variable attenuator 11. Referring to FIG. 6C, the variable attenuator 11 is connected in a π-type so that the input / output impedance is constant at 50Ω.
It comprises PIN diodes D1 to D3, and the amount of attenuation changes in response to the supply of the AGC voltage AG.

【0008】公知のように、この可変減衰器は減衰量に
依存して被減衰信号の雑音指数(NF)が変動する。例
えば、入力RF信号が−20dBと高い場合の所要減衰
量を15dBとするとNFは減衰量と等しいから15d
Bとなる。高周波回路素子のNFは前段へ行く程高周波
回路全体の雑音指数に対し支配的に影響する。ここで、
低雑音増幅器1,2の各々のNF=2dB,利得12d
Bとすると、上述のように減衰量15dBの場合は、こ
の従来の回路の場合は、次式で示すように、NF=5.
57dBと本来の低雑音増幅器1,2のNF=2dBに
比較して相当劣化する。 NFT=10log{NF1+(NF2−1)/G1+(NF3−1)/G1G 2…+(NFn−1)/G1G2…Gn}・・・・・・・・・・・・・(1) ここで、NFT:n段の高周波回路全体の総合NF(d
B)、NF1…NFn:第1段のNF…第n段のNF
(dB)、G1…Gn:第1段の利得…第n段の利得
(dB)をそれぞれ表す。
As is well known, the variable attenuator varies the noise figure (NF) of the attenuated signal depending on the amount of attenuation. For example, if the required attenuation is 15 dB when the input RF signal is as high as -20 dB, NF is equal to the attenuation, so
B. The NF of the high-frequency circuit element predominantly affects the noise figure of the entire high-frequency circuit as it goes to the preceding stage. here,
NF of each of the low noise amplifiers 1 and 2 = 2 dB, gain 12 d
B, when the attenuation is 15 dB as described above, in the case of this conventional circuit, NF = 5.
This is considerably deteriorated compared to 57 dB, which is NF = 2 dB of the original low noise amplifiers 1 and 2. NFT = 10 log {NF1 + (NF2-1) / G1 + (NF3-1) / G1G2 ... + (NFn-1) / G1G2 ... Gn} (1) , NFT: total NF (d
B), NF1... NFn: NF of the first stage... NF of the nth stage
(DB), G1... Gn: first stage gain... Nth stage gain (dB), respectively.

【0009】したがって(1)式より、G1,G2=1
2dB,NF1,NF2=2dB,NF3=15dBと
すると、NFTは5.57dBとなる。
Therefore, from equation (1), G1, G2 = 1
Assuming 2 dB, NF1, NF2 = 2 dB and NF3 = 15 dB, the NFT is 5.57 dB.

【0010】また、入力RF信号ILが−65dBmの
場合は可変減衰器11の減衰量は0dBすわわちNF3
=0dBの場合はNFTは2.24dBとなる。
When the input RF signal IL is -65 dBm, the attenuation of the variable attenuator 11 is 0 dB, that is, NF3
In the case of = 0 dB, the NFT is 2.24 dB.

【0011】[0011]

【発明が解決しようとする課題】上述した従来のマイク
ロ波放送受信回路は、ミキサの利得が固定であるため、
入力レべル変動に対応してFM復調器の入力信号レベル
を一定範囲内に保持するための可変減衰器を必要とし、
この可変減衰器の減衰量の大きいときに受信回路全体の
雑音指数を劣化させるという欠点があった。
In the conventional microwave broadcast receiving circuit described above, the gain of the mixer is fixed.
It requires a variable attenuator to keep the input signal level of the FM demodulator within a certain range corresponding to the input level fluctuation,
When the attenuation of the variable attenuator is large, there is a disadvantage that the noise figure of the entire receiving circuit is deteriorated.

【0012】本発明の目的は、受信信号レベルの変動に
対応して利得を変化させてFM復調器の入力レベルを一
定に保持するとともに一定の雑音指数を保持できるマイ
クロ波放送受信回路を提供することにある。
An object of the present invention is to provide a microwave broadcast receiving circuit capable of maintaining a constant noise level while maintaining a constant input level of an FM demodulator by changing a gain in response to a change in a received signal level. It is in.

【0013】[0013]

【課題を解決するための手段】本発明のマイクロ波放送
受信回路は、マイクロ波帯の入力高周波信号を増幅し高
周波増幅信号を出力する低雑音増幅器と、前記高周波増
幅信号を局部発振信号と混合して周波数変換しUHF帯
の中間周波数信号を出力する周波数変換回路と、前記局
部発振信号を供給する局部発振回路と、前記中間周波数
信号を増幅し所望の帯域の中間周波増幅信号を出力する
中間周波増幅器と、前記中間周波増幅信号をFM復調し
てベースバンド信号を出力するFM復調器と、前記中間
周波増幅信号をAM検波し自動利得調整用のAGC信号
を出力するAGC検波回路とを備えるマイクロ波放送受
信回路において、前記AGC信号の供給に応答して前記
周波数変換回路に供給する前記局部発振信号のレベルを
可変する局部発振信号レベル可変回路を備え、前記周波
数変換回路の変換利得を前記局部発振信号のレベルとほ
ぼ直線関係で変化する直線領域で動作させるよう設定す
ることを特徴とするものである。
A microwave broadcast receiving circuit according to the present invention comprises a low-noise amplifier for amplifying an input high-frequency signal in a microwave band and outputting a high-frequency amplified signal, and mixing the high-frequency amplified signal with a local oscillation signal. A frequency conversion circuit for converting the frequency and outputting an intermediate frequency signal in the UHF band; a local oscillation circuit for supplying the local oscillation signal; and an intermediate circuit for amplifying the intermediate frequency signal and outputting an intermediate frequency amplified signal in a desired band. A frequency amplifier; an FM demodulator for FM demodulating the intermediate frequency amplified signal to output a baseband signal; and an AGC detecting circuit for AM detecting the intermediate frequency amplified signal and outputting an AGC signal for automatic gain adjustment. In a microwave broadcast receiving circuit, a local oscillator that varies a level of the local oscillation signal supplied to the frequency conversion circuit in response to the supply of the AGC signal No. with the level variable circuit, is characterized in that configured to operate in a linear region that change the conversion gain of said frequency converting circuit in approximately linear relationship to the level of the local oscillation signal.

【0014】[0014]

【発明の実施の形態】次に、本発明の実施の形態を図6
(A)と共通の構成要素には共通の参照符号を用いてブ
ロックで示す図1(A)を参照すると、この図に示す本
実施の形態のマイクロ波放送受信回路は、従来と共通の
低雑音増幅器1,2と、ミキサ4と、局部発振器5と、
IF増幅器6と、SAWフィルタ7と、AGC増幅器8
と、FM復調器9と、AGC検波回路10とに加えて、
従来の可変減衰器11の代りにAGC電圧電圧AGの供
給に応答して局部発振信号LOのミキサ4への注入レベ
ルを可変して信号LOTを出力しミキサ4の利得を制御
する局発レベル可変回路3を備える。
Next, an embodiment of the present invention will be described with reference to FIG.
Referring to FIG. 1A, which is a block diagram using common reference numerals for components common to FIG. 1A, the microwave broadcast receiving circuit of this embodiment shown in FIG. Noise amplifiers 1 and 2, a mixer 4, a local oscillator 5,
IF amplifier 6, SAW filter 7, AGC amplifier 8
, An FM demodulator 9 and an AGC detection circuit 10,
In response to the supply of the AGC voltage voltage AG instead of the conventional variable attenuator 11, the level of injection of the local oscillation signal LO into the mixer 4 is varied to output a signal LOT and the local oscillation level variable to control the gain of the mixer 4. The circuit 3 is provided.

【0015】局発レベル可変回路3の構成をミキサ4と
ともに回路図で示す図1(B)を参照すると、この局発
レベル可変回路3は、コレクタとベースとを共通接続
(すなわちダイオード接続)しコレクタにAGC電圧A
Gを印加することによりエミッタとの間の導通抵抗を可
変するNPN型トランジスタQ31,Q32を可変減衰
素子として用いる。ミキサ4は一般的な3つの差動回路
から成る平衡型の乗算回路である。
Referring to FIG. 1B, which shows a circuit diagram of the configuration of the local oscillation level varying circuit 3 together with the mixer 4, the local oscillation varying level circuit 3 has a collector and a base commonly connected (ie, diode-connected). AGC voltage A at collector
NPN transistors Q31 and Q32 that vary the conduction resistance between the emitter and G by applying G are used as variable attenuation elements. The mixer 4 is a balanced multiplication circuit composed of three general differential circuits.

【0016】次に、図1(A),(B)を参照して本実
施の形態の動作について説明すると、まず、局発レベル
調整回路3のダイオード接続したトランジスタQ31,
Q32の電流電圧特性を示す図2(A)を参照すると、
印加電圧すなわちAGC電圧AGを大きくすると電流C
が大きくなり、抵抗Rは小さくなる。逆に電圧AGを小
さくすると抵抗Rは大きくなる。これにより電圧AGを
大きくすることによりミキサ4に注入する局部発振信号
LOTのレベルが大きくなり、逆に電圧AGを小さくす
ることにより局部発振信号LOTのレベルが小さくな
る。
Next, the operation of this embodiment will be described with reference to FIGS. 1A and 1B. First, the diode-connected transistors Q31,
Referring to FIG. 2A showing the current-voltage characteristics of Q32,
When the applied voltage, that is, the AGC voltage AG is increased, the current C
Increases, and the resistance R decreases. Conversely, as the voltage AG decreases, the resistance R increases. As a result, the level of the local oscillation signal LOT injected into the mixer 4 increases by increasing the voltage AG, and conversely, the level of the local oscillation signal LOT decreases by decreasing the voltage AG.

【0017】ミキサ4の局部発振信号LOTのレベルと
変換利得GCとの関係をグラフで示す図2(B)を参照
して、局部発振信号レべル可変による変換利得の可変の
原理について説明すると、まず、ミキサ4に供給される
RF信号AL,局部発振信号LOTはそれぞれ下式で表
される。
Referring to FIG. 2B which graphically shows the relationship between the level of the local oscillation signal LOT of the mixer 4 and the conversion gain GC, the principle of changing the conversion gain by changing the local oscillation signal level will be described. First, the RF signal AL and the local oscillation signal LOT supplied to the mixer 4 are represented by the following equations, respectively.

【0018】AL=Asin(2πfa・t) LOT=Bsin(2πfl・t) ここで、A,BはそれぞれRF信号AL,局部発振信号
LOTの振幅値、fa,flはそれぞれRF信号AL,
局部発振信号LOTの周波数、tは時間を示す。
AL = Asin (2πfa · t) LOT = Bsin (2πfl · t) where A and B are the RF signal AL and the amplitude value of the local oscillation signal LOT, respectively, and fa and fl are the RF signal AL and
The frequency of the local oscillation signal LOT, t indicates time.

【0019】次に、ミキサ4は、乗算回路であることか
らIF信号Uは次式で求められる。
Next, since the mixer 4 is a multiplication circuit, the IF signal U is obtained by the following equation.

【0020】 U=Asin(2πfa・t)×Bsin(2πfl・t) =(A・B/2)[cos{2π(fa+fl)t}−cos{2π(fa−f l)}t]・・・・・・・・・・・・・・・・・・・・・・・・・・・(2) ここで、A・B/2はIF信号Uの振幅値、fa+f
l,fa−flはそれぞれIF信号Uの周波数となる。
U = Asin (2πfa · t) × Bsin (2πfl · t) = (A · B / 2) [cos {2π (fa + fl) t} -cos {2π (fa-fl)} t] ·· (2) Here, AB / 2 is the amplitude value of the IF signal U, fa + f
l and fa-fl are the frequencies of the IF signal U, respectively.

【0021】ミキサ4の変換利得GCは、RF信号AL
の振幅値AとIF信号Uの振幅値A・B/2との関係で
あるので、次式で表される。
The conversion gain GC of the mixer 4 is equal to the RF signal AL
And the amplitude value A · B / 2 of the IF signal U, and is expressed by the following equation.

【0022】 A・B/2=GC×A すなわち、GC=B/2・・・・・・・・・・・・・・・・・・・・(3) したがって、変換利得GCと局部発振信号LOTのレベ
ルBとは正比例の関係を示す。
AB × 2 = GC × A That is, GC = B / 2 (3) Therefore, conversion gain GC and local oscillation The signal LOT has a directly proportional relationship with the level B.

【0023】しかし、変換利得GCはミキサ4を構成す
るトランジスタの特性とバイアス条件等に依存して上限
が決定されるため、飽和領域が存在する。従来は変換利
得をRF信号ALの入力レベルと無関係に一定に保持す
るためこの飽和領域で使用していた。
However, since the upper limit of the conversion gain GC is determined depending on the characteristics of the transistors constituting the mixer 4 and the bias conditions, there is a saturation region. Conventionally, the conversion gain is used in this saturation region to keep the conversion gain constant irrespective of the input level of the RF signal AL.

【0024】本実施の形態では、変換利得GCと局部発
振信号LOTのレベルBとの正比例領域を使用し、局発
レベル可変回路3により局部発振信号LOTのレベルを
可変することによりミキサ4の変換利得を制御する。ま
た、ミキサ4の雑音指数は構成素子の各バイアス状態の
雑音指数で決定するため、変換利得とは無関係に安定し
た値となる。
In the present embodiment, the conversion level of the local oscillation signal LOT is varied by the local oscillation level varying circuit 3 by using the direct proportional area between the conversion gain GC and the level B of the local oscillation signal LOT, thereby converting the conversion of the mixer 4. Control the gain. Further, since the noise figure of the mixer 4 is determined by the noise figure of each bias state of the constituent elements, the noise figure becomes a stable value regardless of the conversion gain.

【0025】本実施の形態のマイクロ波受信回路のレベ
ルダイアグラムを示す図3を参照すると、従来と同様の
条件、すなわち、G1,G2=12dB,NF1,NF
2=2dB,入力RF信号ILのレベル−20dB,−
65dBの各々の場合のNFTは、(1)式より計算さ
れ、G1,G2=12dB,NF1,NF2=2dBと
すると、いずれの場合もNFは2.24dBと同一値と
なる。
Referring to FIG. 3 showing a level diagram of the microwave receiving circuit according to the present embodiment, the same conditions as those in the prior art, that is, G1, G2 = 12 dB, NF1, NF
2 = 2 dB, level of input RF signal IL−20 dB, −
The NFT in each case of 65 dB is calculated from the equation (1). If G1, G2 = 12 dB, NF1, NF2 = 2 dB, the NF has the same value as 2.24 dB in each case.

【0026】次に、本発明の第2の実施の形態を特徴付
ける局発レベル可変回路3Aを図1(B)と共通の構成
要素には共通の参照符号を用いて同様に回路図で示す図
4を参照すると、この図に示す本実施の形態の第1の実
施の形態の局発レベル可変回路3との相違点は、トラン
ジスタQ31,Q32の代りにアノードを局部発振信号
の伝送線に接続しカソードを接地してAGC電圧AGを
上記アノードに供給したPINダイオードD31を備え
ることである。
Next, a local oscillation level varying circuit 3A, which characterizes the second embodiment of the present invention, is similarly shown in a circuit diagram by using common reference numerals for components common to those in FIG. 1B. Referring to FIG. 4, the difference between this embodiment and the local oscillation level varying circuit 3 of the first embodiment shown in this figure is that an anode is connected to the transmission line of the local oscillation signal instead of the transistors Q31 and Q32. And a PIN diode D31 that supplies the AGC voltage AG to the anode with the cathode grounded.

【0027】本実施の形態の動作について説明すると、
基本原理としてダイオードD31の電圧対インピーダン
ス特性を利用したものであり、ダイオードD31の印加
電圧すなわちAGC電圧AGに依存してダイオードD3
1のインピーダンスが0〜無限大まで変化する両対数関
係を有している。
The operation of this embodiment will be described.
The basic principle utilizes the voltage-impedance characteristic of the diode D31. The diode D3 depends on the applied voltage of the diode D31, that is, the AGC voltage AG.
1 has a double logarithmic relationship in which the impedance changes from 0 to infinity.

【0028】本実施の形態では、ダイオードD31のイ
ンピーダンスが無限大のとき、減衰量は0となり局部発
振信号LOのレベルがそのまま局部発振信号LOTとし
てミキサ4に供給される。すなわちミキサ4への局部発
振信号LOTの注入レベルが最大となる。ダイオードD
31のインピーダンスが低下するにしたがい、局部発振
信号LOはダイオードD31の方に流入し、その分局部
発振信号LOTのレベルが低下する。さらに、ダイオー
ドD31のインピーダンスが低下し、0となると入力端
で局部発振信号LOを接地した状態と等価となり、ミキ
サ4への信号LOTのレベルは0になる。
In the present embodiment, when the impedance of the diode D31 is infinite, the attenuation is 0 and the level of the local oscillation signal LO is supplied to the mixer 4 as the local oscillation signal LOT as it is. That is, the injection level of the local oscillation signal LOT to the mixer 4 becomes maximum. Diode D
As the impedance of the local oscillation signal 31 decreases, the local oscillation signal LO flows into the diode D31, and the level of the local oscillation signal LOT decreases accordingly. Further, when the impedance of the diode D31 decreases and becomes 0, it becomes equivalent to a state where the local oscillation signal LO is grounded at the input terminal, and the level of the signal LOT to the mixer 4 becomes 0.

【0029】次に、本発明の第3の実施の形態を特徴付
ける局発レベル可変回路3Bを図4と共通の構成要素に
は共通の文字/数字を用いて同様に回路図で示す図5を
参照すると、この図に示す本実施の形態の第2の実施の
形態の局発レベル可変回路3Aとの相違点は、ダイオー
ドD31の代りにアノードを局部発振信号LOの入力端
に接続しカソードを出力端LOTに接続してAGC電圧
AGを上記カソードに供給したPINダイオードD32
を備えることである。
Next, FIG. 5 is a circuit diagram showing a local oscillation level varying circuit 3B which characterizes the third embodiment of the present invention, using common characters / numerals as common components to FIG. Referring to this figure, the difference of the present embodiment from the local oscillation level variable circuit 3A of the second embodiment is that the anode is connected to the input terminal of the local oscillation signal LO instead of the diode D31 and the cathode is connected. A PIN diode D32 connected to the output terminal LOT and supplying the AGC voltage AG to the cathode.
It is to have.

【0030】本実施の形態では、第2の実施の形態と逆
にダイオードD32のインピーダンスが0のとき、減衰
量は0となり局部発振信号LOのレベルがそのまま局部
発振信号LOTとしてミキサ4に供給される。すなわち
ミキサ4への局部発振信号LOTの注入レベルが最大と
なる。ダイオードD32のインピーダンスが上昇するに
したがい、局部発振信号LOは減衰し、その分局部発振
信号LOTのレベルが低下する。さらに、ダイオードD
32のインピーダンスが低下し、無限大となると局部発
振信号うLOは完全に阻止されミキサ4への信号LOT
のレベルは0になる。
In this embodiment, contrary to the second embodiment, when the impedance of the diode D32 is 0, the attenuation becomes 0 and the level of the local oscillation signal LO is supplied to the mixer 4 as the local oscillation signal LOT as it is. You. That is, the injection level of the local oscillation signal LOT to the mixer 4 becomes maximum. As the impedance of the diode D32 increases, the local oscillation signal LO attenuates, and the level of the local oscillation signal LOT decreases accordingly. Further, the diode D
When the impedance at 32 decreases and becomes infinite, the local oscillation signal LO is completely blocked and the signal LOT to the mixer 4 is stopped.
Becomes 0.

【0031】[0031]

【発明の効果】以上説明したように、本発明のマイクロ
波放送受信回路は、AGC信号の供給に応答して局部発
振信号レベルを可変する局部発振信号レベル可変回路を
備え、ミキサ変換利得を局部発振信号のレベルとほぼ直
線領域で動作させるよう設定することにより受信回路利
得を制御することにより、入力RF信号レベルに依存し
て受信機の総合雑音指数の変化要因となる可変減衰器を
除去できるので安定した雑音指数を保持できるという効
果がある。
As described above, the microwave broadcast receiving circuit according to the present invention includes the local oscillation signal level varying circuit for varying the local oscillation signal level in response to the supply of the AGC signal, and the mixer conversion gain is locally adjusted. By controlling the gain of the receiving circuit by setting it to operate in a substantially linear region with the level of the oscillation signal, it is possible to eliminate a variable attenuator that causes a change in the overall noise figure of the receiver depending on the input RF signal level. Therefore, there is an effect that a stable noise figure can be maintained.

【図面の簡単な説明】[Brief description of the drawings]

【図1】本発明のマイクロ波放送受信回路の第1の実施
の形態を示すブロック図及び回路図である。
FIG. 1 is a block diagram and a circuit diagram showing a first embodiment of a microwave broadcast receiving circuit of the present invention.

【図2】本実施の形態のマイクロ波放送受信回路におけ
る動作の一例を示すミキサの特性図である。
FIG. 2 is a characteristic diagram of a mixer showing an example of an operation in the microwave broadcast receiving circuit of the present embodiment.

【図3】本実施の形態のマイクロ波放送受信回路の動作
の一例を示すレベルダイアグラムである。
FIG. 3 is a level diagram illustrating an example of an operation of the microwave broadcast receiving circuit according to the present embodiment.

【図4】本発明のマイクロ波放送受信回路の第2の実施
の形態を特徴付ける局発レベル可変回路の回路図であ
る。
FIG. 4 is a circuit diagram of a local oscillation level varying circuit that characterizes a second embodiment of the microwave broadcast receiving circuit of the present invention.

【図5】本発明のマイクロ波放送受信回路の第3の実施
の形態を特徴付ける局発レベル可変回路の回路図であ
る。
FIG. 5 is a circuit diagram of a local oscillation level varying circuit characterizing a third embodiment of the microwave broadcast receiving circuit of the present invention.

【図6】従来のマイクロ波放送受信回路の一例を示すブ
ロック図である。
FIG. 6 is a block diagram illustrating an example of a conventional microwave broadcast receiving circuit.

【符号の説明】[Explanation of symbols]

1,2 低雑音増幅器 3,3A,3B 局発レベル可変回路 4 ミキサ 5 局部発振器 6 IF増幅器 7 SAWフィルタ 8 AGC増幅器 9 FM復調器 10 AGC検波回路 11 可変減衰器 Q31,Q32 トランジスタ D1〜D3,D31,D32 PINダイオード 1, 2 Low noise amplifier 3, 3A, 3B Local oscillation level variable circuit 4 Mixer 5 Local oscillator 6 IF amplifier 7 SAW filter 8 AGC amplifier 9 FM demodulator 10 AGC detection circuit 11 Variable attenuator Q31, Q32 Transistors D1-D3 D31, D32 PIN diode

───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 FI H04N 7/20 H04N 7/20 ──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. 6 Identification code FI H04N 7/20 H04N 7/20

Claims (4)

【特許請求の範囲】[Claims] 【請求項1】 マイクロ波帯の入力高周波信号を増幅し
高周波増幅信号を出力する低雑音増幅器と、前記高周波
増幅信号を局部発振信号と混合して周波数変換しUHF
帯の中間周波数信号を出力する周波数変換回路と、前記
局部発振信号を供給する局部発振回路と、前記中間周波
数信号を増幅し所望の帯域の中間周波増幅信号を出力す
る中間周波増幅器と、前記中間周波増幅信号をFM復調
してベースバンド信号を出力するFM復調器と、前記中
間周波増幅信号をAM検波し自動利得調整用のAGC信
号を出力するAGC検波回路とを備えるマイクロ波放送
受信回路において、 前記AGC信号の供給に応答して前記周波数変換回路に
供給する前記局部発振信号のレベルを可変する局部発振
信号レベル可変回路を備え、 前記周波数変換回路の変換利得を前記局部発振信号のレ
ベルとほぼ直線関係で変化する直線領域で動作させるよ
う設定することを特徴とするマイクロ波放送受信回路。
A low-noise amplifier for amplifying an input high-frequency signal in a microwave band and outputting a high-frequency amplified signal;
A frequency conversion circuit that outputs a band intermediate frequency signal; a local oscillation circuit that supplies the local oscillation signal; an intermediate frequency amplifier that amplifies the intermediate frequency signal and outputs an intermediate frequency amplified signal of a desired band; A microwave broadcast receiving circuit comprising: an FM demodulator for FM demodulating a frequency amplified signal to output a baseband signal; and an AGC detecting circuit for AM detecting the intermediate frequency amplified signal and outputting an AGC signal for automatic gain adjustment. A local oscillation signal level variable circuit that varies a level of the local oscillation signal supplied to the frequency conversion circuit in response to the supply of the AGC signal, wherein a conversion gain of the frequency conversion circuit is set to a level of the local oscillation signal. A microwave broadcast receiving circuit, which is set to operate in a linear region that changes in a substantially linear relationship.
【請求項2】 前記局部発振信号レベル可変回路が、コ
レクタとベースとを共通接続しコレクタに前記AGC電
圧を印加することによりエミッタとの間の導通抵抗を可
変するNPN型トランジスタを備えることを特徴とする
請求項1記載のマイクロ波放送受信回路。
2. The local oscillation signal level varying circuit includes an NPN transistor that connects a collector and a base in common, and varies the conduction resistance between the emitter and the collector by applying the AGC voltage to the collector. The microwave broadcast receiving circuit according to claim 1, wherein
【請求項3】 前記局部発振信号レベル可変回路が、ア
ノードを前記局部発振信号の伝送線に接続しカソードを
接地して前記AGC信号を前記アノードに供給したPI
Nダイオードを備えることを特徴とする請求項1記載の
マイクロ波放送受信回路。
3. A PI circuit wherein the local oscillation signal level variable circuit connects an anode to the transmission line of the local oscillation signal, grounds a cathode of the local oscillation signal, and supplies the AGC signal to the anode.
2. The microwave broadcast receiving circuit according to claim 1, further comprising an N diode.
【請求項4】 前記局部発振信号レベル可変回路が、ア
ノードを前記局部発振信号の入力端に接続しカソードを
出力端に接続して前記AGC信号を前記カソードに供給
したPINダイオードを備えることを特徴とする請求項
1記載のマイクロ波放送受信回路。
4. The local oscillation signal level varying circuit includes a PIN diode having an anode connected to the input terminal of the local oscillation signal, a cathode connected to an output terminal, and supplying the AGC signal to the cathode. The microwave broadcast receiving circuit according to claim 1, wherein
JP34781596A 1996-12-26 1996-12-26 Microwave broadcasting reception circuit Pending JPH10190509A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP34781596A JPH10190509A (en) 1996-12-26 1996-12-26 Microwave broadcasting reception circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP34781596A JPH10190509A (en) 1996-12-26 1996-12-26 Microwave broadcasting reception circuit

Publications (1)

Publication Number Publication Date
JPH10190509A true JPH10190509A (en) 1998-07-21

Family

ID=18392783

Family Applications (1)

Application Number Title Priority Date Filing Date
JP34781596A Pending JPH10190509A (en) 1996-12-26 1996-12-26 Microwave broadcasting reception circuit

Country Status (1)

Country Link
JP (1) JPH10190509A (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1564883A1 (en) * 2004-02-10 2005-08-17 STMicroelectronics N.V. Method and apparatus for frequency conversion, in particular for controlling the emitting power of a cellular mobile telephone
JP2006203488A (en) * 2005-01-20 2006-08-03 Matsushita Electric Ind Co Ltd High frequency signal receiver, integrated circuit used for same and electronic equipment using receiver
JP2007124403A (en) * 2005-10-28 2007-05-17 Kyocera Corp Radio receiver and gain control method thereof
JP2009118386A (en) * 2007-11-09 2009-05-28 Hitachi Kokusai Electric Inc Level adjustment circuit of reception signal
JP2009218931A (en) * 2008-03-11 2009-09-24 Nec Infrontia Corp Radio communication set, and input voltage adjustment method
JP2014127795A (en) * 2012-12-26 2014-07-07 Nec Corp Radio communication device, signal conditioning circuit and signal conditioning method

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1564883A1 (en) * 2004-02-10 2005-08-17 STMicroelectronics N.V. Method and apparatus for frequency conversion, in particular for controlling the emitting power of a cellular mobile telephone
JP2006203488A (en) * 2005-01-20 2006-08-03 Matsushita Electric Ind Co Ltd High frequency signal receiver, integrated circuit used for same and electronic equipment using receiver
JP2007124403A (en) * 2005-10-28 2007-05-17 Kyocera Corp Radio receiver and gain control method thereof
JP2009118386A (en) * 2007-11-09 2009-05-28 Hitachi Kokusai Electric Inc Level adjustment circuit of reception signal
JP2009218931A (en) * 2008-03-11 2009-09-24 Nec Infrontia Corp Radio communication set, and input voltage adjustment method
JP2014127795A (en) * 2012-12-26 2014-07-07 Nec Corp Radio communication device, signal conditioning circuit and signal conditioning method

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