摘要
本应用笔记介绍了压控振荡器(VCO)的槽路设计方法，并给出了常用的中频(IF) 85MHz、190MHz、210MHz压控振荡器的设计实例。这些设计减少了为优化设计而进行的重复工作，具体分析可借助一个简单的电子表格实现。
更多信息：
概述
本应用笔记介绍了压控振荡器(VCO)的槽路设计方法，并给出了常用的中频(IF) 85MHz、190MHz、210MHz压控振荡器的设计实例。这些设计减少了为优化设计而进行的重复工作，具体分析可借助一个简单的电子表格实现。
VCO设计
图2表示MAX2310 IF VCO的差分槽路，为便于分析，所给槽路只是一个简单的等效模型。图1表示基本的VCO模型，振荡频率由式1表示：
|
式1
|
fosc = 振荡频率
L = 槽路线圈的电感值
Cint = MAX2310槽路端口的内部电容
Ct = 槽路的总计等效电容
图1. 基本的VCO模型
Rn = MAX2310槽路端口的等效负阻
Cint = MAX2310槽路端口的内部电容
Ct = 槽路的总计等效电容
L = 槽路线圈的电感值
图2. MAX2310槽路
电感L与槽路等效电容和振荡器内部电容的总和产生谐振(Ct+Cint) (参见图1)。Ccoup提供隔直流、并将变容二极管的可变电容耦合至槽路。Ccent用来确定槽路振荡频率标称值的中心。它不是必须的，但为在不同的电感量之间调谐谐振腔提供了便利条件。电阻(R)通过调谐电压(Vtune)为变容二极管提供相反的偏置。应选择足够大的阻值，以保证加载后的槽路Q值不受影响；另外，还要保证电阻值足够小，使4kTBR噪声可以忽略。电阻的噪声电压受KVCO调制后将产生相位噪声。电容Cv是槽路内部的可变调谐元件，变容二极管的电容(Cv)是反向偏置电压的函数(变容二极管模型参见附录A)。Vtune是来自锁相环(PLL)的调谐电压。
图3在VCO模型中增加了Cstray，寄生电容和寄生电感使所有射频(RF)电路的罪魁祸首，为估算振荡频率必须考虑寄生参数。图3用电容Cstray表示寄生元件，振荡频率可由式2表示：
|
式2
|
L = 槽路线圈的电感值
Cint = MAX2310槽路端口的内部电容
Ccent = 用于确定中心振荡频率的槽路电容
Cstray = 电容漂移
Ccoup = 槽路电容，用来将变容二极管耦合至槽路
Cv = 变容二极管电容的净变量(包括串联电感)
Cvp = 变容二极管焊盘的电容
图3. Cstray模型
图4表示VCO模型的详细电路，它考虑了焊盘的等效电容，但为简便起见没有考虑串联电感。Cstray定义为：
 |
式3
|
CL = 电感的电容量
CLP = 电感焊盘的电容量
CDIFF = 平行引线的等效电容
图4. 详细的VCO模型
Rn = MAX2310槽路端口的等效负阻
Cint = MAX2310槽路端口的内部电容
LT = 电感槽路引线的串联电感
CDIFF = 平行引线的等效电容
L = 槽路线圈电感
CL = 电感等效电容
CLP = 电感焊盘等效电容
Ccent = 用于确定中心振荡频率的槽路电容
Ccoup = 槽路电容，用来将变容二极管耦合至槽路
Cvar = 变容二极管电容的变化量
Cvp = 变容二极管焊盘电容
LS = 变容二极管串联电感
R = 变容二极管反向偏置电阻的阻值
为简化分析，设计中忽略了电感LT。LT通常对高频端影响较大，为了用下面的电子表格描述LT所产生的频率偏差的数学模型，可适当增大CDIFF，减小LT以避免产生所不希望的串联谐振。这一点可通过缩短引线实现。
调谐增益
为获得最佳的闭环相位噪声特性应尽可能降低调谐增益(Kvco)，环路滤波器的电阻和电阻“R” (图2)会产生宽带噪声，宽带热噪声(
)将按照Kvco调制VCO输出，用单位MHz/V表示。减小Kvco的途径有两条：一是降低压控振荡器的调谐范围；第二种方法是增大所允许的调节电压范围。要在保证足够的VCO调谐频率范围的前提下减小其调谐范围，需要选用容差极小的元器件，后面将对这一点作详细描述。为扩大电压调节范围，需采用电荷泵电路以提供适当的电压范围，这种方式一般需要采用更高的Vcc。MAX2310允许的电压调节范围是：0.5V至Vcc-0.5V。电池供电应用中，电压调节范围受电池电压或稳压器的制约。
免调节设计的基本概念
VCO槽路设计中需对实际部件进行误差分析，为了设计一个振荡在固定频率(fosc)的VCO，必须考虑元件误差。在设计调谐增益(Kvco)时必须将这些元件容差考虑进去。元件容差越小、可能产生的调谐增益越小，闭环相位噪声就越低。考虑误差最大的情况，可以用以下三种VCO模型表示：
- 元件最大值(式5)
- 标准谐振电路，对应于元件标称值(式2)
- 元件最小值(式4)
图5. 极端情况下的槽路中心频率和标称中心频率
为保证槽路的闭环相位噪声最小，需尽可能减小调谐范围。但要注意在考虑系统最大容差时仍能覆盖标准振荡频率。元件值分别达到最大和最小时，槽路的调谐范围尽量靠近所期望的振荡频率的边沿，考虑到系统容差对式2加以修正，可得最大误差时对应的振荡频率式4、式5：
|
式4
|
 |
式5
|
TL = %电感(L)的容差
TCINT = %电容(CINT)的容差
TCCENT = %电容(CCENT)的容差
TCCOUP = %电容(CCOUP)的容差
TCV = %变容二极管电容(CV)的容差
式4和式5假设偏差量没有容差。
一般设计过程
步骤1
估算或测量焊点的寄生电容或其它寄生电容：用Boonton 72BD电容计对MAX2310评估板(Rev C)进行测试，测得寄生电容为：CLP = 1.13pF、CVP = 0.82pF、CDIFF = 0.036pF。
步骤2
确定电容Cint：这个参数在MAX2310/MAX2312/MAX2314/MAX2316数据资料的第5页查找到，谐振端口的1/S11随频率变化的典型工作特性给出了几个常用频点时的等效并联RC参数，附录B包含了槽路端口频率在高频端和低频端时Cint与频率的对应关系表。需要牢记的是本振频率为IF频率的两倍。
例如：
如果IF为210MHz (高频端谐振电路)，本振工作频率应为420MHz。由附录B的表5可得Cint = 0.959pF。
步骤3
选择电感：最好从几何平均值入手，这是一个需要重复迭代的过程。
 |
式6
|
上式中电感、电容的单位分别用nH、pF表示(1x10-9 x 1x10-12 = 1x10-21)。 如果fosc = 420MHz、L = 11.98nH，则槽路总计电容为C = 11.98pF。最初选择容差为2%、电感量为12nH的Coilcraft 0805CS-12NXGBC比较恰当。
如果选择电感具有一定的局限性时，式6.1将是一个很有用的公式。对于一个固定振荡频率fosc，LC的乘积应保持恒定。
|
式6.1
|
fosc = 420MHz时，LC = 143.5，按照表3采用试凑的方法可以得到：电感取18nH、容差为2%，而槽路总电容为7.9221pF。此时，图8中LC乘积为142.59，非常接近理论值143.5。由此可以看出上述关系时的实用性。为保证较低的相位噪声，选用高Q值电感，如：Coilcraft 0805CS系列，如果能够合理控制微带线的容差和Q值，也可选用微带线。
步骤4
确定锁相环(PLL)的合理范围：该参数表示VCO整个调谐电压(Vtune)的工作范围，对于MAX2310，适当范围为：0.5V至Vcc-0.5V，如果Vcc = 2.7V，则调谐电压范围为：0.5V至2.2V，电荷泵输出限定这一范围。槽路电压摆幅为1Vp-p、电压摆幅的中点为1.6V直流，即使选用较大的Ccoup，变容二极管也不会产生正偏。这是一个需要避免的情况，因为二极管将会影响槽路引脚上的交流信号，产生所不期望的杂散响应、造成闭环PLL的失锁。
步骤5
选择变容二极管，在所规定的调谐电压范围内选择容差较小的变容二极管，并保证串联电阻最小，确认变容二极管的自共振频率高于所期望的工作频率。在规定的工作电压范围内察看Cv(2.5V)/Cv(0.5V)的比率。如果选择较大的耦合电容Ccoup，最大调谐范围可利用式2计算；如果选择较小的耦合电容Ccoup，将会降低有效的频率调谐范围。选择变容二极管时需给出调谐范围的中点和端点处的容差，可以选择一个特性曲线较陡峭的变容二极管，如Alpha SMV1763-079，进行线性调节。取槽路总电容、并将其用于变容二极管的Cjo。注意，Ccoup会降低变容二极管耦合到槽路的电容。
步骤6
确定耦合电容Ccoup：Ccoup较大时，变容二极管耦合到槽路的电容较大、使调谐范围增大，但会降低槽路加载后的Q值。Ccoup较小时，会提高耦合变容二极管的Q值和加载后的Q值，但它是以减小调谐范围为代价的。通常是在保证调谐范围的前提下尽可能选择小的容量值。选择较小Ccoup的另一个好处是可以降低变容二极管两端的电压摆幅。
步骤7
确定电容Ccent。一般Ccent取2pF，考虑到电容误差也可选用稍微大一点的电容。利用Ccent调整VCO的标准频率。
步骤8
按照制作的电子表格推敲设计参数。
MAX2310在85MHz、190MHz和210MHz IF时的VCO槽路设计
下列电子表格给出了MAX2310在几个通用IF频点的设计，请牢记：LO振荡频率应为所期望的IF频率的两倍。
图6. 85MHz低频端IF槽路
表1. 85MHz低频端IF槽路设计
| Light grey indicates calculated values. |
| Darker grey indicates user input. |
| MAX2310 Low-Band Tank Design and Tuning Range | |||||
| Total Tank Capacitance vs. V tune | |||||
| V tune | Total C | Ct
(Nominal) |
Ct (Low) |
Ct (High) |
|
| 0.5V | Ct high | 14.1766pF | 13.3590pF | 14.9459pF | |
| 1.375V | Ct mid | 12.8267pF | 11.7445pF | 13.7620pF | |
| 2.2V | Ct low | 11.4646pF | 10.3049pF | 12.4534pF | |
| Tank Components |
|
||||
|
C coup
|
18pF
|
0.9pF
|
5%
|
||
|
C cent
|
5.6pF
|
0.1pF
|
2%
|
||
|
C stray
|
0.70pF
|
||||
|
L
|
68nH
|
2.00%
|
|||
|
C int
|
0.902pF
|
10.00%
|
|||
| Parasitics and Pads (C stray) | |||||
| Due to Q |
C L
|
0.1pF
|
|||
| Ind. pad |
C Lp
|
1.13pF
|
|||
| Due to || |
C diff
|
0.036pF
|
|||
| Var. pad |
C vp
|
0.82pF
|
|||
| Varactor Specs | |||||
| Alpha SMV1255-003 | |||||
| Cjo |
82pF
|
Varactor Tolerance
|
|||
| Vj |
17V
|
0.5V
|
19.00%
|
||
| M |
14
|
1.5V
|
29.00%
|
||
| Cp |
0pF
|
2.5V
|
35.00%
|
||
| Rs |
1Ω
|
Reactance
|
|||
| Ls |
1.7nH
|
X Ls
|
1.82 | ||
| Freq |
170.00MHz
|
||||
| Nominal Varactor |
X c
|
Net Cap
|
|||
|
Cv high
|
54.64697pF
|
-17.1319
|
61.12581pF
|
||
|
Cv mid
|
27.60043pF
|
-33.92
|
29.16154pF
|
||
|
Cv low
|
14.92387pF
|
-62.7321
|
15.36874pF
|
||
| Negative Tol Varactor (Low Capacitance) | |||||
|
Cv high
|
44.26404pF
|
-21.1505
|
48.42117pF
|
||
|
Cv mid
|
19.59631pF
|
-47.7746
|
20.37056pF
|
||
|
Cv low
|
9.700518pF
|
-96.5109
|
9.886531pF
|
||
| Positive Tol Varactor (High Capacitance) | |||||
|
Cv high
|
65.02989pF
|
-14.3965
|
74.41601pF
|
||
|
Cv mid
|
35.60456pF
|
-26.2945
|
38.24572pF
|
||
|
Cv low
|
20.14723pF
|
-46.4682
|
20.96654pF
|
||
| Nominal
LO (Nom) Range |
Low
Tol IF (High) Range |
Nominal
IF (Nom) Range |
High
Tol IF (Low) Range |
||
|
F low
|
162.10MHz
|
84.34MHz
|
81.05MHz
|
78.16MHz
|
|
|
F mid
|
170.42MHz
|
89.95MHz
|
85.21MHz
|
81.45MHz
|
|
|
F high
|
180.25MHz
|
96.03MHz
|
90.13MHz
|
85.62MHz
|
|
|
BW
|
18.16MHz
|
11.69MHz
|
9.08MHz
|
7.46MHz
|
|
|
% BW
|
10.65%
|
12.99%
|
10.65%
|
9.16%
|
|
| Nominal IF Frequency |
|
||||
|
Design
Constraints
|
|||||
| Condition for bold number |
<IF
|
=IF
|
> IF
|
||
| Delta |
0.66
|
-0.21
|
0.62
|
||
| Test |
pass
|
pass
|
pass
|
||
| Raise or lower cent freq by |
-0.21
|
MHz
|
|||
| Inc or dec BW |
-1.28
|
MHz
|
|||
| Cent adj for min BW |
84.98
|
MHz
|
|||
| K vco |
10.68MHz/V
|
||||
图7. 190MHz高频端IF槽路
表2. 190MHz高频端IF槽路设计
| Light grey indicates calculated values. |
| Darker grey indicates user input. |
| MAX2310 High-Band Tank Design and Tuning Range | |||||
| Total Tank Capacitance vs. V tune | |||||
|
V tune
|
Total C | Ct
(Nominal) |
Ct (Low) |
Ct (High) |
|
|
0.5V
|
Ct high | 10.4968pF | 10.0249pF | 10.9126pF | |
|
1.375V
|
Ct mid | 9.6292pF | 8.8913pF | 10.2124pF | |
|
2.2V
|
Ct low | 8.6762pF | 7.7872pF | 9.3717pF | |
| Tank Components |
|
||||
|
C coup
|
12pF
|
0.1pF
|
1%
|
||
|
C cent
|
3.4pF
|
0.1pF
|
3%
|
||
|
C stray
|
0.70pF
|
||||
|
L
|
18nH
|
2.00%
|
|||
|
C int
|
0.954pF
|
10.00%
|
|||
| Parasitics and Pads (C stray) | |||||
| Due to Q |
C L
|
0.01pF
|
|||
| Ind. pad |
C Lp
|
1.13pF
|
|||
| Due to || |
|
0.036pF
|
|||
| Var. pad |
C vp
|
0.82pF
|
|||
| Varactor Specs | |||||
| Alpha SMV1255-003 | |||||
| Cjo |
82pF
|
Varactor Tolerance
|
|||
| Vj |
17V
|
0.5V
|
19.00%
|
||
| M |
14
|
1.5V
|
29.00%
|
||
| Cp |
0pF
|
2.5V
|
35.00%
|
||
| Rs |
1Ω
|
Reactance
|
|||
| Ls |
1.7nH
|
X Ls
|
4.06 | ||
| Freq |
380.00MHz
|
||||
| Nominal Varactor |
X c
|
Net Cap
|
|||
|
Cv high
|
54.64697pF
|
-7.66426
|
116.1695pF
|
||
|
Cv mid
|
27.60043pF
|
-15.1747
|
37.67876pF
|
||
|
Cv low
|
14.92387pF
|
-28.0643
|
17.44727pF
|
||
| Negative Tol Varactor (Low Capacitance) | |||||
|
Cv high
|
44.26404pF
|
-9.46205
|
77.51615pF
|
||
|
Cv mid
|
19.59631pF
|
-21.3728
|
24.19031pF
|
||
|
Cv low
|
9.700518pF
|
-43.1759
|
10.70708pF
|
||
| Positive Tol Varactor (High Capacitance) | |||||
|
Cv high
|
65.02989pF
|
-6.44056
|
175.8588pF
|
||
|
Cv mid
|
35.60456pF
|
-11.7633
|
54.36221pF
|
||
|
Cv low
|
20.14723pF
|
-20.7884
|
25.03539pF
|
||
| Nominal LO (Nom) Range |
Low Tol IF (High) Range |
Nominal IF (Nom) Range |
High Tol IF (Low) Range |
||
|
F low
|
366.15MHz
|
189.23MHz
|
183.07MHz
|
177.78MHz
|
|
|
F mid
|
382.29MHz
|
200.94MHz
|
191.14MHz
|
183.78MHz
|
|
|
F high
|
402.74MHz
|
214.71MHz
|
201.37MHz
|
191.84MHz
|
|
|
BW
|
36.59MHz
|
25.47MHz
|
18.29MHz
|
14.06MHz
|
|
|
% BW
|
9.57%
|
12.68%
|
9.57%
|
7.65%
|
|
| Nominal IF Frequency |
|
||||
|
Design
Constraints
|
|||||
| Condition for bold number |
< IF
|
= IF
|
> IF
|
||
| Delta |
0.77
|
-1.14
|
1.84
|
||
| Test |
pass
|
pass
|
pass
|
||
| Raise or lower cent freq by |
-1.14
|
MHz
|
|||
| Inc or dec BW |
-2.61
|
MHz
|
|||
| Cent adj for min BW |
190.54
|
MHz
|
|||
| K vco |
21.52MHz/V
|
||||
图8. 210MHz高频端IF槽路
表3. 210MHz高频端IF槽路设计
| Light grey indicates calculated values. |
| Darker grey indicates user input. |
| MAX2310 High-Band Tank Design and Tuning Range | |||||
| Total Tank Capacitance vs. V tune | |||||
|
V tune
|
Total C | Ct (Nominal) |
Ct (Low) |
Ct (High) | |
|
0.5V
|
Ct high | 8.8304pF | 8.1465pF | 9.4877pF | |
|
1.35V
|
Ct mid | 7.9221pF | 7.0421pF | 8.6970pF | |
|
2.2V
|
Ct low | 6.9334pF | 5.9607pF | 7.7653pF | |
| Tank Components |
|
||||
|
C coup
|
12pF
|
0.6pF
|
5%
|
||
|
C cent
|
1.6pF
|
0.1pF
|
6%
|
||
|
C stray
|
0.70pF
|
||||
|
L
|
18nH
|
2.00%
|
|||
|
C int
|
0.959pF
|
10.00%
|
|||
| Parasitics and Pads (C stray) | |||||
| Due to Q |
C L
|
0.1pF
|
|||
| Ind. pad |
C Lp
|
1.13pF
|
|||
| Due to || |
C diff
|
0.036pF
|
|||
| Var. pad |
C vp
|
0.82pF
|
|||
| Varactor Specs | |||||
| Alpha SMV1255-003 | |||||
| Cjo |
82pF
|
Varactor Tolerance
|
|||
| Vj |
17V
|
0.5V
|
19.00%
|
||
| M |
14
|
1.5V
|
29.00%
|
||
| Cp |
0pF
|
2.5V
|
35.00%
|
||
| Rs |
1Ω
|
Reactance
|
|||
| Ls |
1.7nH
|
X Ls
|
4.49 | ||
| Freq |
420.00MHz
|
||||
| Nominal Varactor |
X
c
|
Net
Cap
|
|||
|
Cv high
|
54.64697pF
|
-6.93433
|
154.787pF
|
||
|
Cv mid
|
27.60043pF
|
-13.7295
|
40.99616pF
|
||
|
Cv low
|
14.92387pF
|
-25.3916
|
18.12647pF
|
||
| Negative Tol Varactor (Low Capacitance) | |||||
|
Cv high
|
44.26404pF
|
-8.56091
|
92.99806pF
|
||
|
Cv mid
|
19.59631pF
|
-19.3373
|
25.51591pF
|
||
|
Cv low
|
9.700518pF
|
-39.0639
|
10.95908pF
|
||
| Positive Tol Varactor (High Capacitance) | |||||
|
Cv high
|
65.02989pF
|
-5.82717
|
282.5852pF
|
||
|
Cv mid
|
35.60456pF
|
-10.643
|
61.54791pF
|
||
|
Cv low
|
20.14723pF
|
-18.8086
|
26.45795pF
|
||
| Nominal LO (Nom) Range |
Low Tol IF (High) Range |
Nominal IF (Nom) Range |
High Tol IF (Low) Range |
||
|
F low
|
399.20MHz
|
209.92MHz
|
199.60MHz
|
190.67MHz
|
|
|
F mid
|
421.47MHz
|
225.78MHz
|
210.73MHz
|
199.14MHz
|
|
|
F high
|
450.52MHz
|
245.41MHz
|
225.26MHz
|
210.75MHz
|
|
|
BW
|
51.31MHz
|
35.49MHz
|
25.66MHz
|
20.09MHz
|
|
|
% BW
|
12.18%
|
15.72%
|
12.18%
|
10.09%
|
|
| Nominal IF Frequency |
|
||||
|
Design
Constraints
|
|||||
| condition for bold number |
< IF
|
= IF
|
> IF
|
||
| Delta |
0.08
|
-0.73
|
0.75
|
||
| Test |
pass
|
pass
|
pass
|
||
| Raise or lower cent freq by |
-0.73
|
MHz
|
|||
| Inc or dec BW |
-0.83
|
MHz
|
|||
| Cent adj for min BW |
210.34
|
MHz
|
|||
| K vco |
30.18MHz/V
|
||||
图9. 高-Q值210MHz高频端IF槽路
表4. 高-Q值210MHz高频端IF槽路设计
| Light grey indicates calculated values. |
| Darker grey indicates user input. |
| MAX2310 High-Band Tank Design and Tuning Range | |||||
| Total Tank Capacitance vs. V tune | |||||
|
V tune
|
Total C | Ct (Nominal) |
Ct (Low) |
Ct (High) | |
|
0.5V
|
Ct high | 5.8856 | 5.5289 | 6.2425 | |
|
1.375V
|
Ct mid | 5.2487 | 4.9113 | 5.5858 | |
|
2.2V
|
Ct low | 4.8371 | 4.5156 | 5.1581 | |
| Tank Components
|
|||||
|
C coup
|
15pF
|
0.75pF
|
5%
|
||
|
C cent
|
1.6pF
|
0.1pF
|
6%
|
||
|
C stray
|
0.77pF
|
||||
|
L
|
27
|
2.00%
|
|||
|
C int
|
0.959
|
10.00%
|
|||
| Parasitics and Pads (C stray) | |||||
| Due to Q |
C L
|
0.17pF
|
|||
| Ind. pad |
C Lp
|
1.13pF
|
|||
| Due to || |
C diff
|
0.036pF
|
|||
| Var. pad |
C vp
|
0.82pF
|
|||
| Varactor Specs | |||||
| Alpha SMV1763-079 | |||||
| Cjo |
8.2pF
|
Varactor Tolerance
|
|||
| Vj |
15V
|
0.5V
|
7.50%
|
||
| M |
9.5
|
1.5V
|
9.50%
|
||
| Cp |
0.67pF
|
2.5V
|
11.50%
|
||
| Rs |
0.5Ω
|
Reactance
|
|||
| Ls |
0.8nH
|
X Ls
|
2.11 | ||
| Freq |
420.00MHz
|
||||
| Nominal Varactor |
X
c
|
Net
Cap
|
|||
|
Cv high
|
6.67523pF
|
-56.7681
|
6.933064pF
|
||
|
Cv mid
|
4.23417pF
|
-89.4958
|
4.336464pF
|
||
|
Cv low
|
2.904398pF
|
-130.471
|
2.952167pF
|
||
| Negative Tol Varactor (Low Capacitance) | |||||
|
Cv high
|
6.174588pF
|
-61.3709
|
6.39456pF
|
||
|
Cv mid
|
3.831924pF
|
-98.8904
|
3.915514pF
|
||
|
Cv low
|
2.570392pF
|
-147.425
|
2.607736pF
|
||
| Positive Tol Varactor (High Capacitance) | |||||
|
Cv high
|
7.175873pF
|
-52.8076
|
7.474698pF
|
||
|
Cv mid
|
4.636416pF
|
-81.7313
|
4.759352pF
|
||
|
Cv low
|
3.238404pF
|
-117.015
|
3.297904pF
|
||
| Nominal LO (Nom) Range |
Low Tol IF (High) Range |
Nominal IF (Nom) Range |
High Tol IF (Low) Range |
||
|
F low
|
399.25MHz
|
208.05MHz
|
199.62MHz
|
191.92MHz
|
|
|
F mid
|
422.78MHz
|
220.75MHz
|
211.39MHz
|
202.89MHz
|
|
|
F high
|
440.40MHz
|
230.22MHz
|
220.20MHz
|
211.14MHz
|
|
|
BW
|
41.15MHz
|
22.16MHz
|
20.58MHz
|
19.21MHz
|
|
|
% BW
|
9.73%
|
10.04%
|
9.73%
|
9.47%
|
|
| Nominal IF Frequency |
|
||||
|
Design
Constraints
|
|||||
| Condition for bold number |
< IF
|
= IF
|
> IF
|
||
| Delta |
1.95
|
-1.39
|
1.14
|
||
| Test |
pass
|
pass
|
pass
|
||
| Raise or lower cent freq by |
-1.39
|
MHz
|
|||
| Inc or dec BW |
-3.08
|
MHz
|
|||
| Cent adj for min BW |
209.60
|
MHz
|
|||
| K vco |
24.21MHz/V
|
||||
附录A
图10. 变容二极管模型
Alpha应用笔记AN1004对变容二极管模型提供了更多信息。变容二极管电容定义为式7:
|
式7
|
| Alpha SMV1255-003 | Alpha SMV1763-079 |
| Cjo = 82 pF | Cjo = 8.2 pF |
| Vj =17 V | Vj =15 V |
| M = 14 | M = 9.5 |
| Cp = 0 | Cp = 0.67 |
| Rs = 1Ω | Rs = 0.5Ω |
| Ls = 1.7 nH | Ls = 0.8 nH |
变容二极管串联电感可以用反向输出的感抗表示，计算新的等效电容Cv为:
|
式8
|
附录B
表5. MAX2310高频槽路中Cint与频率的对应关系
| Frequency (MHz) | Cint (pF) | Frequency (MHz) (cont.) | Cint (pF) (cont.) |
| 100 | 0.708 | 360 | 0.949 |
| 110 | 0.759 | 370 | 0.955 |
| 120 | 0.800 | 380 | 0.954 |
| 130 | 0.809 | 390 | 0.954 |
| 140 | 0.839 | 400 | 0.954 |
| 150 | 0.822 | 410 | 0.955 |
| 160 | 0.860 | 420 | 0.959 |
| 170 | 0.869 | 430 | 0.956 |
| 180 | 0.880 | 440 | 0.959 |
| 190 | 0.905 | 450 | 0.964 |
| 200 | 0.917 | 460 | 0.962 |
| 210 | 0.920 | 470 | 0.963 |
| 220 | 0.926 | 480 | 0.963 |
| 230 | 0.924 | 490 | 0.960 |
| 240 | 0.928 | 500 | 0.964 |
| 250 | 0.935 | 510 | 0.965 |
| 260 | 0.932 | 520 | 0.968 |
| 270 | 0.931 | 530 | 0.966 |
| 280 | 0.933 | 540 | 0.968 |
| 290 | 0.927 | 550 | 0.967 |
| 300 | 0.930 | 560 | 0.974 |
| 310 | 0.933 | 570 | 0.977 |
| 320 | 0.943 | 580 | 0.976 |
| 330 | 0.944 | 590 | 0.984 |
| 340 | 0.945 | 600 | 0.982 |
| 350 | 0.956 | - | - |
图11. MAX2310高频端槽路中Cint与频率的对应关系(6阶多项式曲线拟和)
表6. MAX2310低频端槽路中Cint与频率的对应关系
| Frequency (MHz) | Cint (pF) | Frequency (MHz) (cont.) | Cint (pF) (cont.) |
| 100 | 0.550 | 360 | 1.001 |
| 110 | 0.649 | 370 | 0.982 |
| 120 | 0.701 | 380 | 0.992 |
| 130 | 0.764 | 390 | 1.001 |
| 140 | 0.762 | 400 | 0.985 |
| 150 | 0.851 | 410 | 0.980 |
| 160 | 0.838 | 420 | 0.986 |
| 170 | 0.902 | 430 | 0.992 |
| 180 | 0.876 | 440 | 0.994 |
| 190 | 0.907 | 450 | 1.001 |
| 200 | 0.913 | 460 | 1.003 |
| 210 | 0.919 | 470 | 1.007 |
| 220 | 0.945 | 480 | 0.992 |
| 230 | 0.952 | 490 | 1.010 |
| 240 | 0.965 | 500 | 1.004 |
| 250 | 0.951 | 510 | 1.011 |
| 260 | 0.954 | 520 | 1.022 |
| 270 | 0.974 | 530 | 1.019 |
| 280 | 0.980 | 540 | 1.044 |
| 290 | 0.973 | 550 | 1.026 |
| 300 | 0.982 | 560 | 1.041 |
| 310 | 0.970 | 570 | 1.038 |
| 320 | 0.982 | 580 | 1.032 |
| 330 | 0.991 | 590 | 1.036 |
| 340 | 0.993 | 600 | 1.025 |
| 350 | 0.991 | - | - |
图12. MAX2310低频端槽路中Cint与频率的对应关系(6阶多项式曲线拟和)
参考资料
- Chris O'Connor, Develop Trimless Voltage-Controlled Oscillators, Microwaves and RF, July1999.
- Wes Hayward, Radio Frequency Design, Chapter 7.
- Krauss, Bostian, Raab, Solid State Radio Engineering, Chapters 2, 3, 5.
- Alpha Industries Application Note AN1004.
- Coilcraft, RF Inductors Catalog, March 1998, p.131.
- Maxim, MAX2310/MAX2312/MAX2314/MAX2316 Data Sheet, Rev 0.
- Maxim, MAX2310/MAX2314 Evaluation Kit Data Sheet, Rev 0.
- Maxim, MAX2312/MAX2316 Evaluation Kit Data Sheet, Rev 0.
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