MODEL 2A
MODEL 2A-C
APPLICATIONS
APPLICATION AS A ZERO-DISTORTION MODULATOR
The model 2A should be driven by a single-ended baseband plus DC signal into pin 9. The DC term supplied sets the average carrier output level, and the AC baseband signal superimposed on this DC swings the carrier amplitude above and below this value. The maximum frequency of the AC signal is 200 kHz, and the total harmonic distortion is highest for higher AC baseband frequencies, rising above that specified for 1 kHz modulation.
The RF output of the 2A in the modulator mode is very accurately controlled at 50 Ohms, and has an output RMS carrier amplitude of 1 Volt RMS at pin 7 (into 50 Ohms) per 1 Volt into pin 9, very accurately trimmed internally.
The maximum instantaneous undistorted RF carrier output level in this mode is 1 Volt RMS into 50 Ohms. Additionally, twice this level is available into an open circuit load with the 2A remaining stable.
No connections should be made to the pins not shown, except that pins 13 and 14 (the 10 MHz differential outputs) may be AC coupled into a type MC10116 or MC10216-style ECL line receiver using a 56 uH shielded inductor (eg, Nytronics WEE-56) between each ECL line receiver input pin and Vbb (pin 11 of the line recvr.). In this manner, the CW carrier, before modulation is impressed, can be used to synchronize other circuits as desired by the user, or can be used to furnish a system clock, since the 10 MHz signal is crystal-controlled and accurate to much better than 0.1%.
The modulator in the model 2A and 2A-C is two-quadrant.
APPLICATION AS A HIGHLY LINEAR RF DETECTOR
Refer to the appropriate pin-interconnection diagram. The modulator output is connected to the RF feedback-detector input pin (6). In normal high-accuracy use, the RF signal to be detected and/or demodulated is capacitor-coupled into pin 1, the RF input-detector. This capacitor coupling, or "DC-block", must be supplied by the user, and is suggested in order to provide identical transient-response in both the RF input and RF feedback paths (the RF feedback path is already AC-coupled via 0.1 uF). However, the penalty for not AC-coupling is not severe, causing only about 0.2% error.
The user-supplied trimpot zeroes the linearized-detector output baseline.
MODEL 2A-C CONFIGURATIONS
The model 2A-C is available in two versions: (1) configured as a modulator; and (2) configured as a linearized ideal detector. The input and output ports are SMA connectors. (See specs.)
USING THE 2A TO DETECT RF SIGNALS UNDER 10 MHZ
In the event that operation must be obtained at less than 10 MHz for the LINEAR RF DETECTOR configuration, external matched capacitors must be supplied from pins 3 and 4 to ground. The value of these must be at least 100 pF times the ratio of 10 MHz to the lowest carrier frequency to be detected. For example, for detection of a 10 kHz carrier frequency, each external capacitor must be 0.1 uF. The maximum recoverable modulation frequency will also be reduced by the same ratio (1000 times). In addition, an external compensation capacitor must be added to keep the RF feedback loop stable (free of oscillations). This capacitor must be added from pin 10 to pin 11 and must have a value at least equal to the previously calculated ratio (of 10 MHz divided by lowest carrier frequency), times 220 pF.
The internally-generated 10 MHz clock is available to the user on pins 13 and 14 as previously described in the description for configuring the 2A as a modulator.
As before, the recovered baseband signal is obtained at pin 9, and will have the instantaneous value of 1 Volt per each 1 Volt RMS instantaneous carrier level at pin 1. Maximum undistorted signal level is 1 Volt at both pins 1 and 9.
EXTERNALLY-SUPPLIED 10 MHZ CARRIER
The model 2A carrier pins 13 and 14 can accept an external 10 MHz Ac-coupled ECL-swing differential signal (must be 50% duty factor within 3%) only if specially modified in manufacture by T-Tech. The modified version omits the quartz crystal, however, and therefore can be used ONLY in the external-carrier mode. Order part number 2A/002A-E.
PIN KEYING & ORIENTATION
Note that all pins are spaced 0.2 inches apart except for the closer spacing of 0.1 inch for pins 9, 10, 11. This assures correct insertion into the PC board, and eliminates need for special markings.
MOUNTING
The 2A must be soldered directly into a master PC board if full carrier frequency range is desired. Teflon-fiberglass material is preferable if operation above 500 MHz is desired, although G10 fiberglass of 0.062 inch thickness may be usable. No ground plane should be provided directly under the 2A bottom surface, but microstripline and ground plane techniques are recommended for the main RF signal path.
MOUNTING MODEL 2A-C
Threaded mounting holes are provided in the 2A-C unit along the surface to which the SMA connectors are mounted. (see specs.)
| SPECIFICATIONS | |
| Power Supplies: | + 15 V ~ 150 mA; -15 V ~ 130 mA |
| Modulator Transfer Function: | 1 Volt RMS carrier @ 50 Ohms per 1 Volt into pin 9 (positive polarity only) Tolerance: 1.5% (or 0.15 dB) |
| Detector Feedback Loop Bandwidth: | 200 kHz |
| Closed-loop Detector Dynamic Range: | 1 Volt RMS @ 50 Ohms, down to - 40 dBV for 1 % linearity; Offset variation = - 43 dBV DC |
| Modulator Distortion: | 0.15% THD at 1 kHz baseband and 95% modulation and RF envelope crests at 1 Volt RMS into 50 Ohms |
| Modulator SNR: | 70 dB or better after demodulation by a perfect AM detector in a 20 kHz post-detection band, relative to full-scale RF crest output |
| Operating Temperature: | + 5 to + 50 degrees C for specified performance; usable from - 25 to + 125 C |
| Modulator Input Impedance: | Resistive (primarily), 1 megOhm within 30% shunted by less than 15pF |
| Baseband Output Impedance of Closed Loop Detector Config.: | Less than 250 Ohms |
| Load Resistance at pin 10 for Detector Configuration: | Greater than 1 k Ohm allowable |
| Modulator Output Impedance: | 50 Ohms, within 9 % |
| RF Detector Input Impedance: | 50 Ohms nominal; return loss less than 12 dB to 350 MHz, 15 dB to 100 MHz |
| RF Detector Response: | 10 kHz to 100 MHz within 0.3 dB, to 500 MHz flat within 0.5 dB; 1.5 dB to 1 GHz |
| Housing (model 2A): | Flame-resistant black encapsulated module |
| Housing (model 2A-C): | Nickel-plated RF sealed enclosure |
| Power dissipated: | Approximately 4.2 Watts |
| Maximum Detector RF Input Voltages: | 2 Volts RMS into 50 Ohms (about 20 dBm) |
| Maximum Power Supply: | + 16 and -16 V, absolute max. |
| Power Supply Immunity: | All specs met for supply noise less than 10 mV RMS |
| Model 2A-C Dimensions: | Metal box = 6" long x 3" high x 1.5" thk Mounting holes (4 each) spaced 1" apart in groups of 2; 5.5" distance between groups; each hole threaded for #6-32 screw; threaded to 1/8" depth |
| Model 2A-C SMA Spacing: | SMA Connectors spaced 5.375" apart |
| Model 2A-C Feedthroughs: | Feedthrough connectors for power & GND |
NOTE: All specifications are subject to change. T-TECH reserves the right to make improvements to the product without being obliged to install those improvements in previously sold units. No guarantee of suitability for any given application is implied, n or is the suitability of the unit outside the temperature range specified, or outside the specified voltages, both DC and AC.
This product contains both patented circuitry and block-diagram approach. Infringement will not be tolerated. However, non-exclusive licensing is available for qualifying O.E.M.'s in the event that they wish to package the product in a different form, or merge the packaging with their own PC boards, hybrids, etc. Contact T-TECH via email, fax, or telephone for details.