JPH065232B2 - FM modulation circuit test method - Google Patents
FM modulation circuit test methodInfo
- Publication number
- JPH065232B2 JPH065232B2 JP6872385A JP6872385A JPH065232B2 JP H065232 B2 JPH065232 B2 JP H065232B2 JP 6872385 A JP6872385 A JP 6872385A JP 6872385 A JP6872385 A JP 6872385A JP H065232 B2 JPH065232 B2 JP H065232B2
- Authority
- JP
- Japan
- Prior art keywords
- modulation
- circuit
- modulation circuit
- input
- voltage
- 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 - Lifetime
Links
- 238000010998 test method Methods 0.000 title claims description 5
- 238000012360 testing method Methods 0.000 claims description 22
- 238000006073 displacement reaction Methods 0.000 claims description 6
- 238000001514 detection method Methods 0.000 description 7
- 238000005259 measurement Methods 0.000 description 6
- 239000003990 capacitor Substances 0.000 description 5
- 230000008878 coupling Effects 0.000 description 4
- 238000010168 coupling process Methods 0.000 description 4
- 238000005859 coupling reaction Methods 0.000 description 4
- 239000004065 semiconductor Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000005236 sound signal Effects 0.000 description 1
Landscapes
- Testing Electric Properties And Detecting Electric Faults (AREA)
Description
【発明の詳細な説明】 産業上の利用分野 本発明は、ＦＭ変調回路の試験方法，特にＦＭ変調回路
の主要特性の１つであるＦＭ変調度の測定方法に関する
ものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for testing an FM modulation circuit, and more particularly to a method for measuring an FM modulation degree, which is one of the main characteristics of an FM modulation circuit.
従来の技術 従来、ＦＭ変調回路のＦＭ変調度は、第２図で示される
試験回路を構成して測定されていた。第２図の回路で示
すように、正弦波信号発生器１から、 で表わされる正弦波信号を、リレー２、入力信号分圧回
路３、カップリングコンデンサ４のそれぞれを介して、
ＦＭ変調回路５の入力端子５１に加え、その出力端子５
２からのＦＭ変調信号を、周波数カウンタ６で観測しな
がら、ＦＭ検波回路７を通したのち、交流電圧計８で検
出して、ＦＭ変調度を測定していた。すなわち、この測
定系によると、まず、出力周波数を調整するタンク回路
の可変リアクタンス５０１（または、これに相当するも
の）およびコンデンサ５０２を含む被試験ＦＭ変調回路
５の入力端子５１を、リレー２をオフにして、無信号に
し、出力端子５２のフリーラン周波数ｆ０を周波数カウ
ンタ６で測定し、同周波数ｆ０を、可変リアクタンス５
０１等を調整して、変調中心周波数（例えば、ＮＴＳＣ
ＴＶ音声中間周波数ならば４．５ＭHz）に合わせる。次
に、リレー２をオンにして正弦波信号発生器１から音声
信号である正弦波信号 を入力信号分圧回路３とカップリングコンデンサ４を通
して被試験ＦＭ変調回路５の入力端子５１に加え、出力
端子５２に接続されたＦＭ検波回路７を経て元の正弦波
に復調する。ここでＦＭ検波回路７のＦＭ検波リニアテ
ィ特性が、十分保証されていれば復調した正弦波出力の
レベルを交流電圧計８を用いて測定することにより被試
験ＦＭ変調回路５のＦＭ変調度を求めることができる。2. Description of the Related Art Conventionally, the FM modulation factor of an FM modulation circuit has been measured by configuring a test circuit shown in FIG. As shown in the circuit of FIG. 2, from the sine wave signal generator 1, The sine wave signal represented by is passed through the relay 2, the input signal voltage dividing circuit 3, and the coupling capacitor 4 respectively.
In addition to the input terminal 51 of the FM modulation circuit 5, its output terminal 5
The FM modulation signal from 2 was observed by the frequency counter 6, passed through the FM detection circuit 7, and then detected by the AC voltmeter 8 to measure the FM modulation degree. That is, according to this measurement system, first, the input terminal 51 of the FM modulation circuit 5 to be tested including the variable reactance 501 (or the equivalent thereof) of the tank circuit for adjusting the output frequency and the capacitor 502 is connected to the relay 2. It is turned off to make no signal, the free-run frequency f 0 of the output terminal 52 is measured by the frequency counter 6, and the same frequency f 0 is set to the variable reactance 5
01 etc. to adjust the modulation center frequency (for example, NTSC
If it is a TV audio intermediate frequency, adjust to 4.5 MHz). Next, the relay 2 is turned on and the sine wave signal generator 1 outputs a sine wave signal which is an audio signal. Is applied to the input terminal 51 of the FM modulation circuit 5 to be tested through the input signal voltage dividing circuit 3 and the coupling capacitor 4, and is demodulated to the original sine wave via the FM detection circuit 7 connected to the output terminal 52. Here, if the FM detection linearity characteristic of the FM detection circuit 7 is sufficiently guaranteed, the level of demodulated sine wave output is measured using the AC voltmeter 8 to obtain the FM modulation degree of the FM modulation circuit 5 under test. be able to.
発明が解決しようとする問題点 ＦＭ変調回路のフリーラン周波数ｆ０は、無調整時にお
いて、たとえば、被試験ＦＭ変調用半導体集積回路によ
り、ある程度（例えば、f0＝4.5ＭHzとすると最大で±1
00ＫHz程度）のばらつきをもっている。一般的なＦＭ検
波回路のＦＭ検波帯域でＦＭ検波リニアリティ特性が良
いのは、ＦＭ変調回路の最大変調度と同程度であるか
ら、同ＦＭ変調回路のフリーラン周波数ｆ０を無調整の
ままＦＭ変調度を測定しようとすると被試験ＦＭ変調用
半導体集積回路によっては、見かけ上のＦＭ変調度が悪
くなってしまう。そこで、従来からの試験方法では、可
変リアクタンス等による被試験ＦＭ変調用半導体集積回
路のフリーラン周波数f0の逐次調整を必要とし、その調
整が煩雑であり測定の自動化が困難である。Problems to be Solved by the Invention The free-run frequency f 0 of the FM modulation circuit is, to some extent (for example, if f 0 = 4.5 MHz, when the adjustment is performed), the free-run frequency f 0 is ±± maximum due to the semiconductor integrated circuit for FM modulation under test. 1
It has a variation of about 00 KHz). The FM detection linearity characteristic is good in the FM detection band of a general FM detection circuit because it is about the same as the maximum modulation degree of the FM modulation circuit. Therefore, the free run frequency f 0 of the FM modulation circuit is adjusted without adjustment. When it is attempted to measure the modulation factor, the apparent FM modulation factor may deteriorate depending on the semiconductor integrated circuit for FM modulation under test. Therefore, in the conventional test method, it is necessary to successively adjust the free-run frequency f 0 of the semiconductor integrated circuit for FM modulation under test by a variable reactance or the like, and the adjustment is complicated and automation of measurement is difficult.
本発明は、以上説明してきた従来の試験方法に存在した
問題点を排し、ＦＭ変調度試験の自動測定を目的とする
試験方法を提供するものである。The present invention eliminates the problems existing in the conventional test methods described above, and provides a test method for the purpose of automatic measurement of an FM modulation degree test.
問題点を解決するための手段 本発明は、上記問題点を解決するため、入力信号源から
見た入力インピーダンスを変えずに正弦波信号を直流電
圧に置き換え、同直流入力電圧の変位量に対応する出力
周波数の変位量を測定することにより被試験ＦＭ変調回
路のＦＭ変調度を測定するものである。Means for Solving the Problems The present invention, in order to solve the above problems, replaces a sine wave signal with a DC voltage without changing the input impedance viewed from the input signal source, and responds to the displacement amount of the DC input voltage. The FM modulation degree of the FM modulation circuit under test is measured by measuring the displacement amount of the output frequency.
作用 このようにして得られたＦＭ変調度のデータは、被試験
ＦＭ変調回路の特性評価において従来法と変わるところ
はない。また、直流入力電圧変位量に対する出力周波数
変位量からＦＭ変調度を求めているので絶対値である。
フリーラン周波数ｆ０のばらつきに影響されることがな
く可変リアクタンスの調整という作業を省くことができ
る。The data of the FM modulation degree thus obtained is no different from the conventional method in the characteristic evaluation of the FM modulation circuit under test. Further, since the FM modulation degree is obtained from the output frequency displacement amount with respect to the DC input voltage displacement amount, it is an absolute value.
The work of adjusting the variable reactance can be omitted without being affected by the variation in the free-run frequency f 0 .
実施例 第１図に本発明の一実施例を示す。まず、被試験ＦＭ変
調回路５の入力端子５１を、リレー２をオフにして無入
力とし、一方、入力端子５１を直流電圧計９につない
で、被試験ＦＭ変調回路５の入力自己バイアス電圧Ｖ０
を直流電圧計９により測定する。この入力自己バイアス
電圧Ｖ０は、入力信号を正弦波から直流電圧に置き換え
るため、第２図のカップリングコンデンサ４を取り除い
たときに第１図の直流電圧源は１０から見た直流入力イ
ンピーダンスと第２図の正弦波信号発生器１から見た交
流入力インピーダンスとが被試験ＦＭ変調回路の入力イ
ンピーダンスにかかわらず等価となるように、同回路の
測定の際に、直流入力電圧の設定基準及び入力信号分圧
回路３の分圧基準電圧として、基準電圧源１１から付与
するために測定する。次に、第１図に示す試験回路のリ
レー２をオンにして、基準電圧源１１を、先の測定で得
られた入力自己バイアス電圧Ｖ０に設定して、入力信号
を、直流電圧源１０より、従来法の正弦波信号の最大振
幅である を入力分圧回路３の分圧抵抗301，302により分圧して被
試験ＦＭ変調回路５の入力端子５１に加え、出力端子５
２に出力された各々の周波数ｆ１，ｆ２を周波数カウン
タ６により読み取る。その差である｜f1−f2｜により、
被試験ＦＭ変調回路５のＦＭ変調度を求めることができ
る。また、直流入力電圧を入力自己バイアス電圧Ｖ０を
基準にして広範囲に細かく取り、それに対応する出力周
波数を求めると被試験ＦＭ変調回路５のＦＭ変調リニア
リティ特性を知ることができる。Embodiment FIG. 1 shows an embodiment of the present invention. First, the input terminal 51 of the FM modulation circuit 5 under test is turned off to make no input, and the input terminal 51 of the FM modulation circuit 5 is connected to the DC voltmeter 9 to input the input self-bias voltage V 0 of the FM modulation circuit 5 under test.
Is measured with a DC voltmeter 9. Since this input self-bias voltage V 0 replaces the input signal with a DC voltage from a sine wave, when the coupling capacitor 4 of FIG. 2 is removed, the DC voltage source of FIG. In order to make the AC input impedance seen from the sine wave signal generator 1 of FIG. 2 equivalent regardless of the input impedance of the FM modulation circuit under test, the setting reference of the DC input voltage and It is measured so as to be applied from the reference voltage source 11 as the divided reference voltage of the input signal voltage dividing circuit 3. Next, the relay 2 of the test circuit shown in FIG. 1 is turned on, the reference voltage source 11 is set to the input self-bias voltage V 0 obtained in the previous measurement, and the input signal is changed to the DC voltage source 10 Is the maximum amplitude of the conventional sinusoidal signal Is divided by the voltage dividing resistors 301 and 302 of the input voltage dividing circuit 3 and added to the input terminal 51 of the FM modulation circuit 5 under test, and the output terminal 5
The respective frequencies f 1 and f 2 output to 2 are read by the frequency counter 6. By the difference | f 1 −f 2 |
The FM modulation degree of the FM modulation circuit 5 under test can be obtained. Further, the FM input linearity characteristic of the FM modulation circuit 5 under test can be known by finely capturing the DC input voltage in a wide range with reference to the input self-bias voltage V 0 and determining the output frequency corresponding thereto.
発明の効果 以上述べてきたように本発明によれば、ＦＭ変調回路を
構成する，たとえば、ＦＭ変調用半導体集積回路のＦＭ
変調度の測定において可変リアクタンスによる調整とい
う作業を省くことができＦＭ変調度試験の自動測定を容
易にすることができる。As described above, according to the present invention, an FM modulation circuit is constituted, for example, an FM of a semiconductor integrated circuit for FM modulation.
In the measurement of the modulation factor, the work of adjusting by the variable reactance can be omitted, and the automatic measurement of the FM modulation factor test can be facilitated.
第１図は、本発明の一実施例におけるＦＭ変調回路のＦ
Ｍ変調度試験回路のブロック図、第２図は、従来の試験
回路のブロック図である。 １……正弦波信号発生器、２……入力信号ON／OFFリレ
ー、３……入力分圧回路、３０１……分圧抵抗ＲＡ、３
０２……分圧抵抗ＲＢ、４……カップリングコンデン
サ、５……被試験ＦＭ変調回路、５１……入力端子、５
２……出力端子、５０１……可変リアクタンス、５０２
……コンデンサ、６……周波数カウンタ、７……ＦＭ検
波器、８……交流電圧計、９……直流電圧計、１０……
直流電圧源、１１……基準電圧源。FIG. 1 shows F of an FM modulation circuit according to an embodiment of the present invention.
FIG. 2 is a block diagram of an M modulation index test circuit, and FIG. 2 is a block diagram of a conventional test circuit. 1 ... Sine wave signal generator, 2 ... Input signal ON / OFF relay, 3 ... Input voltage dividing circuit, 301 ... Voltage dividing resistor RA , 3
02 ... voltage dividing resistor R B , 4 ... coupling capacitor, 5 ... FM modulation circuit under test, 51 ... input terminal, 5
2 ... Output terminal, 501 ... Variable reactance, 502
...... Condenser, 6 …… Frequency counter, 7 …… FM detector, 8 …… AC voltmeter, 9 …… DC voltmeter, 10 ……
DC voltage source, 11 ... Reference voltage source.
Claims (1)
て、被試験ＦＭ変調回路の入力自己バイアス電圧を基準
にした可変直流電圧源と入力信号分圧回路及び出力測定
用周波数カウンタを用いて前記被試験ＦＭ変調回路を構
成し、前記可変直流電圧源の直流電圧の変位量に対応す
る出力周波数の変位量を測定することにより、ＦＭ変調
度を求めることを特徴とするＦＭ変調回路の試験方法。1. In measuring the FM modulation degree of an FM modulation circuit, a variable DC voltage source based on an input self-bias voltage of an FM modulation circuit under test, an input signal voltage dividing circuit, and an output measuring frequency counter are used. A method of testing an FM modulation circuit, comprising forming an FM modulation circuit under test, and determining an FM modulation degree by measuring a displacement amount of an output frequency corresponding to a displacement amount of a DC voltage of the variable DC voltage source. .
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6872385A JPH065232B2 (en) | 1985-04-01 | 1985-04-01 | FM modulation circuit test method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6872385A JPH065232B2 (en) | 1985-04-01 | 1985-04-01 | FM modulation circuit test method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61226665A JPS61226665A (en) | 1986-10-08 |
| JPH065232B2 true JPH065232B2 (en) | 1994-01-19 |
Family
ID=13381998
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6872385A Expired - Lifetime JPH065232B2 (en) | 1985-04-01 | 1985-04-01 | FM modulation circuit test method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH065232B2 (en) |
-
1985
- 1985-04-01 JP JP6872385A patent/JPH065232B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61226665A (en) | 1986-10-08 |
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