第一页
philips semiconductors
product specification
double-balanced mixer and oscillator
ne/sa602a
description
the ne/sa602a is a low-power vhf monolithic double-balanced mixer with input amplifier, on-board oscillator, and voltage regulator. it is intended for high performance, low power communication systems. the guaranteed parameters of the sa602a make this device particularly well suited for cellular radio applications. the mixer is a "gilbert cell" multiplier configuration which typically provides 18db of gain at 45mhz. the oscillator will operate to 200mhz. it can be configured as a crystal oscillator, a tuned tank oscillator, or a buffer for an external lo. for higher frequencies the lo input may be externally driven. the noise figure at 45mhz is typically less than 5db. the gain, intercept performance, low-power and noise characteristics make the ne/sa602a a superior choice for high-performance battery operated equipment. it is available in an 8-lead dual in-line plastic package and an 8-lead so (surface-mount miniature package).
features
low current consumption: 2.4ma typical
excellent noise figure: <4.7db typical at 45mhz
high operating frequency
excellent gain, intercept and sensitivity
low external parts count; suitable for crystal/ceramic filters
sa602a meets cellular radio specifications
applications
cellular radio mixer/oscillator
portable radio
vhf transceivers
rf data links
hf/vhf frequency conversion
instrumentation frequency conversion
broadband lans
ordering information
philips 半导体
产品规格数
双平衡混频器与振荡器
ne/sa602a
描述
ne/sa602a 是一款单芯片、低功耗、双平衡的 vhf 混频器，自带有输入放大器、板上振荡器、稳压器。它适合于高性能、低功耗的通讯系统。sa602a 的保证参数使得它特别适合于蜂窝无线应用。混频器为一个“gilbert 单元”的倍增配置，在 45mhz 时典型增益为 18db。它可以使用高达 200mhz 的振荡器。可设置成为晶体振荡器、调谐的坦克振荡器，或者是一个外置 lo 的缓冲器。更高频率的 lo 输入可带来额外的驱动能力。在 45mhz 时的噪声系数的典型值小于 5db。对于高性能的电池供电的设备来说，ne/sa602a 的增益、拦截性能、低功耗与噪声特性，使得它成为一个优良的选择。可选 dip-8 与 sop-8 封装（smt封装）。
特征：
消耗电流低：典型值为 2.4ma。
优秀的噪声系数：在 45mhz 时典型值为 <4.7db
工作频率高
优良的增益、拦截、敏感度。
所需的外部器件少；适合晶体/陶瓷滤波器
sa602a 满足蜂窝无线电规格
features
low current consumption: 2.4ma typical
excellent noise figure: <4.7db typical at 45mhz
high operating frequency
excellent gain, intercept and sensitivity
low external parts count; suitable for crystal/ceramic filters
sa602a meets cellular radio specifications
应用：
蜂窝无线混频器/振荡器
便携式收音机
vhf 收发两用机
rf 数据链
hf/vhf 变频
仪表变频
宽带局域网
订购信息
第三页
absolute maximum ratings
ac/dc electrical characteristics vcc=+6v, t(a)=25℃; unless otherwise stated
description of operation
the ne/sa602a is a gilbert cell, an oscillator/buffer, and a temperature compensated bias network as shown in the equivalent circuit. the gilbert cell is a differential amplifier (pins 1 and 2) which drives a balanced switching cell. the differential input stage provides gain and determines the noise figure and signal handling performance of the system.
the ne/sa602a is designed for optimum low power performance. when used with the sa604 as a 45mhz cellular radio second if and demodulator, the sa602a is capable of receiving -119dbm signals with a 12db s/n ratio. third-order intercept is typically -13dbm (that is approximately +5dbm output intercept because of the rf gain). the system designer must be cognizant of this large signal limitation. when designing lans or other closed systems where transmission levels are high, and small-signal or signal-to-noise issues are not critical, the input to the ne602a should be appropriately scaled.
besides excellent low power performance well into vhf, the ne/sa602a is designed to be flexible. the input, rf mixer output and oscillator ports can support a variety of configurations provided the designer understands certain constraints, which will be explained here.
the rf inputs (pins 1 and 2) are biased internally. they are symmetrical. the equivalent ac input impedance is approximately 1.5k || 3pf through 50mhz. pins 1 and 2 can be used interchangeably, but they should not be dc biased externally. figure 5 shows three typical input configurations.
the mixer output (pins 4 and 5) are also internally biased. each output is connected to the internal positive supply by a 1.5kΩ resistor. this permits direct output termination yet allow for balanced output as well. figure 6 shows three single ended output configurations and a balanced output.
the oscillator is capable of sustaining oscillation beyond 200mhz in crystal or tuned tank configurations. the upper limit of operation is determined by tank "q" and required driver levels, the higher the "q" or the smaller the required drive, the higher the permissible oscillation frequency. if the required lo is beyond oscillation limits, or the system calls for an external lo, the external signal can be injected at pin 6 through a dc blocking capacitor. external lo should be at least 200mvp-p.
figure 7 shows several proven oscillator circuits. figure 7a is appropriate for cellular radio. as shown, an overtone mode of operation is utilized. capacitor c3 and inductor l1 suppress oscillation at the crystal fundamental frequency. in the fundamental mode, the suppression network is omitted.
figure 8 shows a colpitts varactor tuned tank oscillator suitable for synthesizer-controlled applications. it is important to buffer the output of this circuit to assure that switching spikes from the first counter or prescaler do not end up in the oscillator spectrum. the dual-gate mosfet provides optimum isolation with low current. the fet offers good isolation, simplicity, and low current, while the bipolar transistors provide the simple solution for non-critical applications. the resistive divider in the emitter-follower circuit should be chosen to provide the minimum input signal which will assure correct system operation.
when operated above 100mhz, the oscillator may not start if the q of the tank if too low. a 22kΩ resistor from pin 7 to ground will increase the dc bias current of the oscillator transistor. this improves the ac operating characteristic of the transistor and should help the oscillator to start. a 22kΩ resistor will not upset the other dc biasing internal to the device, but smaller resistance values should be avoided.
最大绝对额定值
ac/dc 下的电子特性
默认测试环境：vcc=+6v, t(a)=25℃（除非另作说明）
操作说明：
如 ne/sa602a 的等效电路所示：它由一个 gilbert 单元，一个振荡器/缓冲器，一个温度补偿偏置网络组成。gilbert 单元是一个差分放大器（脚1与2），它驱动了一个平衡开关单元。差分输入级提供了增益、检测噪声系数与信号处理系统的性能。
ne/sa602a 的功耗被优化到了最低。当 sa604 被用作 45mhz 的蜂窝无线电的第二 if 与解调器时，在 12db s/n 比时，sa602a 可以接收 -119dbm 的信号。三阶拦截的典型值为 -13dbm（因为 rf 增益，输出拦截大约为 +5dbm）。系统设计者必须认识到这个大信号的局限。在设计局域网或其它封闭的系统时，由于发射电平为高，小信号或者信噪比就不是问题了，ne602a 的输入必须适当第缩小。
ne/sa602a 是一款适用于 vhf 的低功耗的芯片，使用起来非常灵活。如果设计师知道它的局限时，就可以灵活地配置输入、rf 混频器的输出与晶体端口。这些规定如下所示：
rf 输入（脚1和2）在内部被偏置了。它们是对称的。在50mhz 时，等效的 ac 输入电阻大概是 1.5k || 3pf。脚 1 和 2 可互换，但是不能外接 dc 偏置。图 5 显示了 3 种典型的输入接法。
混频器输入（脚4和5）同样内部被偏置了。每个输出端都通过一个 1.5kΩ 的电阻连接到内部的正电源。这将许可直接输出、平衡输出。图 6 显示了 3 个单端输出配置与一个平衡输出。
振荡器能够维持超过200mhz的晶体或调谐坦克配置所产生的振荡。工作的上限取决于坦克“q”与所需要的驱动电平，“q”越高，所需要的驱动越小，可使用的振荡频率越高。假如所需要的 lo 达到振荡极限，或者系统使用外部的 lo，外部信号可通过一个 dc 隔直电容注入脚 6。外部 lo 至少为 200mvp-p。
图 7 显示了几个可用的振荡器电路。图 7a 适合蜂窝式无线电。如图所示，电路工作在泛音模式下。电容 c3 与电感 l1 被用来滤掉晶体的基频振荡。在基频模式下，滤波网络被省略了。
图 8 显示了一个使用考毕兹变容二极管的调谐坦克振荡器，适用于受控合成器。电路的输出端确保从第一个计数器或分频器来的开关尖峰，不会扰乱振荡器的波形，这对缓冲器来说是很重要的。使用双栅极的 mosfet，可提供优秀的小电流的隔离。使用 fet，可提供了简单的优秀的小电流的隔离，而在非关键场合，最简单的方案就是使用三极管。要使得射极跟随器电路中的分压电阻只消耗最小的输入信号，这样将会确保系统正常工作。
当工作频率高达 100mhz 时，假如坦克的 q 太小的话，振荡器可能就不会起振。在第 7 脚使用一个 22kΩ 的电阻接地，可增加振荡器晶体管的 dc 偏置电流。这将改进晶体管的 ac 工作特性，帮助振荡器起振。22kΩ 的电阻不会干扰其它的 dc 偏置内部的元件，但是不要用小阻值的电阻。
