Equivalent Circuit of the Bolometer Detector

A small-signal dynamic equivalent circuit is established for the output voltage of a dc-biased bolometer (barretter) detector. The circuit consists of a voltage generator /spl upsi//sub g/, whose output is an undistorted replica of the incident RF-power modulation envelope, followed by a series resistor R/sub 1/ of dynamic origin, a shunt capacitor C that represents heat storage in the bolometer wire, and a series resistor R/sub 0/ equal to the dc resistance, usually 200 ohms. The resistance R/sub 1/ is independent of signal level, and is typically about 220 ohms for an 8.75-mA bolometer and about 120 ohms for a 4.5-mA bolometer. At a modulation frequency f/sub m/ near 0 Hz, the equivalent audio source impedance of the bolometer is R/sub 1/ +R/sub 0/. The common belief that the source impedance is R/sub 0/ in the weak-signal case is, therefore, refuted. Formulas are derived giving v/sub g/ / /P/sub RF/ and R/sub 1/ as functions of basic, easily determined bolometer parameters. The time constant for open-circuit load is /spl tau//sub oc/= R/sub 1/C, where /spl tau//sub oc/ is determined best by measurement, since catalog values of /spl tau//sub oc/ often are seriously in error. The capacitance is C=/spl tau//sub oc/ / /R/sub 1/. With one type of bolometer /spl tau//sub oc/ measures about 110 /spl mu/s, while various catalogs state values of 250 to 350 /spl mu/s. The equivalent circuit is confirmed quantitatively by measurements of output voltage and source impedance versus modulation frequency.     

A simple analytical model of counter doping in a uniformly and heavily doped channel region of MOSFETS

We analyze counter doping into a heavily and uniformly doped channel MOSFET region, which enabled us to suppress short channel effects with a proper threshold voltage V_th. We derive a model for the relation between the counter doping conditions and V_th and verify its validity with numerical and experimental data. We show that V_th is determined by the centroid, R_p, and dose, Φ_D, of the counter doping and that V_th is independent of the straggle ΔR_p. We show that R_p is almost invariable while (ΔR_p² + 2Dt) is smaller than R_p0², where R_p0 is the initial R_p which is the projected range of ion implantation, D is the diffusion coefficient of the counter doped impurities, and t is the annealing time. Using this technology we can expect superb short channel immunity with a reduced threshold voltage suitable for deep submicron gate length devices, which is shown from numerical analysis.     

Radiation on Losses Due to Variations of Radius Dielectric or Optical Fibers

The total loss of the HE/sub 11/ mode to the radiation field of a finite dielectric rod with small amplitude surface irregularities is considered, and a simple approximate analytic expression for radiation due to sinusoidal roughness is presented. It is shown that radiation occurs only when the frequency of surface roughness /spl Omega/ is in the range /spl beta/-k/sub 2/相似文献   

A high performance 1 Mbit EPROM

A high-performance 1-Mb EPROM has been developed by utilizing advanced 1.2-/spl mu/m minimum design rule technology. The device technology used is n-channel E/D MOS. The memory cell size is 5.5/spl times/7.5 /spl mu/m and the die size is 9.4/spl times/7.2 mm. The word organization is changeable between 64K words/spl times/16 bits and 128K words/spl times/8 bits. The active power dissipation is 500 mW and the standby power dissipation is 150 mW. The access time is typically 200 ns. The programming voltage is 12-14 V and the programming pulse width is typically 1 ms/word. In order to realize such a high-density, high-speed, low power 1-Mb EPROM, 1.2-/spl mu/m minimum patterning process technology, a high-speed sense amplifier, and a high-speed decoder are used.     

A new method of determination of minority carrier diffusion lengthin the base region of silicon solar cells

A new method of determination of the minority carrier diffusion length (L) in the base region of an n⁺-p-p⁺ silicon solar cell using the spectral response of the cell in a middle wavelength (λ) range, e.g., 0.75<λ<0.90 μm is presented. In this method Q_int or if required Q_int/f where Q_int is the internal quantum efficiency of the cell and f=exp(-(x_bα_λ ))(L²α_λ²/L² α_λ²-1), x_b being the distance of base region from the front surface, is plotted against the reciprocal absorption coefficient (α_λ^-1 of silicon. The Q_int versus α_λ ^-1 or else Q_int/f versus α_λ^-1, plot gives an intercept L_MW on the α_λ^-1-axis and a unit intercept on the other axis. The intercept length L_MW is related to L through d/L and S_B, where d is the thickness of the base region and S_B is the back surface recombination velocity of minority carriers. For d/L>2.5, L=L_MW and is independent of S_B. However, for d/L<2.5, the true value of L which may be somewhat different from L_MW can be determined if S_B is known. While most existing long wavelength spectral response (LWSR) methods require d/L to be large (d/L>2.5) is such that tanh(d/L)≈1, this method has no such restriction on d/L. It is highly suitable for cells for which L is large but x_b is small. We have applied the MWSR and LWSR methods to a few n⁺-p-p⁺ silicon solar cells and have found that the former is much superior to the latter if d/L<2.5     

Properties ofPN^2sequences (Corresp.)

A method for generating sequences that approximate binary random sequences with the probability of a 1 equal to 1/4 is described. These are calledPN^2sequences.PN^2sequences are generated by clocking aPNsequence generator at the l's of aPNsequence. ThePN^2sequence is 1 when the generator output makes a transition and is 0 otherwise. It is shown thatPN^2sequences have periodN^2if thePNsequence generators have periodN. The density of l's is shown to approach 1/4 for largeN. It is shown that the normalized out-of-phase pulse-coincidence autocorrelation function can never exceed 1/2 or be less than 1/4 and is 1/4 most of the time for largeN.     

Rise time of silicon p-n-p photodiodes

Exact analytical expressions are derived for the short circuit photodiode currents excited by light pulses, under the assumption that the drift carrier velocity linearly depends on the electric field in the depletion layer. Reflection from the back surface of the photodiode is taken into account. Using the obtained expressions it is possible to establish a connection between the rise time t_rise and the product W_eff of the absorption coefficient (λ) and effective depletion layer width W_eff(W) at various ratios of the diode thickness and the effective depletion layer width. The influence of the RC-constant (where C is the photodiode effective capacity and R is the sum of the diode series and loading resistances) on the rise time is also analyzed.

One of the most important conclusions is that generally the rise time is larger for p-n-n⁺ photodiode configurations than for n-p-p⁺ configurations at the same substrate resistivity.     

Resonance Measurements on Nickel-Cobalt Ferrites as a Function of Temperature and on Nickel Ferrite-Aluminates

The variation of line width (Delta H) and effective g factor (g/sub eff/) with cobalt content and with temperature is studied in a series of ferrites of composition Ni/sub 1- alpha/Co/sub alpha/Mn/sub 0.02/Fe/sub 1.9/O/sub 4+-/. Here alpha lies between 0 and 0.09; temperatures range from 20° to 340° C. A minimum in Delta H is observed at alpha=0.027; g/sub eff/ decreases with increasing alpha. The temperature dependence of each is qualitatively that which would be expected on the basis of the temperature dependence of the anistrophy of the mixed ferrite. Above room temperature Delta H and g/sub eff/ increase or decrease, depending on the cobalt content. It is also shown that the shape of the resonance line is determined by the sign of the anisotropy constant. For negative K/sub 1/ the line is steeper on the low-field side of resonance--for positive K/sub 1/ it is steeper on the high-field side. Resonance data are presented on several nickel-cobalt ferrite-aluminates, of composition Ni/sub 1_alpha/Co/sub alpha/Mn/sub 0.02/Fe/sub 2-t/Al/sub t/O/sub 4+-/, with alpha varying from 0 to 0.025 for t=0.3, 0.4, 0.5, and 0.6. The reduction of Delta H and g/sub eff/ expected from anisotropy considerations is observed.     

Bandwidth Potential of Cascode HBT-Based TWAs as a Function of Transistor ${ f} _{max} /{ f} _{ T}$ Ratio

The bandwidth potential of cascode HBT-based broadband amplifiers following the traveling-wave amplifier (TWA) concept is studied. An approximate expression for the gain of the circuit is derived, which is based on the transistor small-signal model and the artificial transmission-line parameters. In this way, a relation between the HBT cutoff frequencies f_T and f_max and the 3-dB cutoff frequency f_c of the amplifier is obtained. This is very useful for assessing the gain-bandwidth potential of a given HBT technology for cascode-based TWAs. Applying these results, we study the potential of two technologies with different f_max / f_T ratios, an InP technology with f_max / f_T of 120 GHz/190 GHz, and a GaAs technology with f_max / f_T of 170 GHz/36 GHz. The higher influence of /max (compared to f_t) on f_c is quantitatively demonstrated. TWAs in both technologies were realized and measured, and good agreement between measurement and theory is obtained.     

Theory of Direct-Coupled-Cavity Filters

A new theory is presented for the design of direct-coupled-cavity filters in transmission line or waveguide. It is shown that for a specified range of parameters the insertion-loss characteristic of these filters in the case of Chebyshev equal-ripple characteristic is given very accurately by the formula P/sub 0/ / /P/sub L/ = 1+h/sup 2/T/sub n//sup 2/[/spl omega//sub 0/ / /spl omega/ sin(/spl pi/ /spl omega/ / /spl omega//sub 0/) / sin/spl theta//sub 0/'] where h defines the ripple level, T/sub n/ is the first-kind Chebyshev polynomial of degree n, /spl omega/ / /spl omega//sub 0/ is normalized frequency, and /spl theta//sub 0/' is an angle proportional to the bandwidth of a distributed lowpass prototype filter. The element values of the direct-coupled filter are related directly to the step impedances of the prototype whose values have been tabulated. The theory gives close agreement with computed data over a range of parameters as specified by a very simple formula. The design technique is convenient for practical applications.     

A study of relaxation current in high-/spl kappa/ dielectric stacks

Dielectric relaxation currents in SiO/sub 2//Al/sub 2/O/sub 3/ and SiO/sub 2//HfO/sub 2/ high-/spl kappa/ dielectric stacks are studied in this paper. We studied the thickness dependence, gate voltage polarity dependence and temperature dependence of the relaxation current in high-/spl kappa/ dielectric stacks. It is found that high-/spl kappa/ dielectric stacks show different characteristics than what is expected based on the dielectric material polarization model. By the drain current variation measurement in n-channel MOSFET, we confirm that electron trapping and detrapping in the high-/spl kappa/ dielectric stacks is the cause of the dielectric relaxation current. From substrate injection experiments, it is also concluded that the relaxation current is mainly due to the traps located near the SiO/sub 2//high-/spl kappa/ interface. As the electron trapping induces a serious threshold voltage shift problem, a low trap density at the SiO/sub 2//high-/spl kappa/ interface is a key requirement for high-/spl kappa/ dielectric stack application and reliability in MOS devices.     

A model for fast switching transients in power systems: the nearzone concept

The author presents a simple time-domain model which makes it possible to predict the order of magnitude of the highest di/ dt values generated by closing switches in electrical power systems. The model is based on traveling-wave analysis. It is demonstrated that two different approaches must be applied, according to whether (a) the closing time, T_s, of the switch is faster than twice the traveling time to the first reflection point or (b) T_s is much slower. Under condition (b) the well-known quasistationary approach di/dt_max=U₀/L can be used, where U₀ is the switched voltage and L is the self-inductance of the line between the stray capacitances located to the left and the right of the switching device. Under condition (a) a new formula must be applied: di/dt _max≈2 U₀/ZT_s, where Z is the line impedance of the line in which the switching device is installed and T_s is the time during which the voltage across the switch collapses from U₀ to zero. Experimental results are given from both fast and slow closing switches     

Single-chip per channel codec with filters utilizing /spl Delta/-/spl Sigma/ modulation

A single-chip per channel codec with filters, fabricated using a single poly-Si NMOS technology, is discussed. In the encoder, the analog signal is converted to a 2.048 M samples/s digital signal by a /spl Delta/-/spl Sigma/ modulator. Filtering necessary for the sampling rate 8 k sample/s and compression by the /spl mu/255 law are performed digitally. In the decoder, the 8 k samples/s PCM is successively resampled and converted into the 2.048 M samples/s /spl Delta/-/spl Sigma/ signal, which is then decoded by a /spl Delta/-/spl Sigma/ demodulator. All the high-frequency images, which appear around multiples of 8 kHz, are removed by digital filters. The chip has continuous-signal antialiasing and smoothing filters for the 2.048 Samples/s sampling rate. It also has reference voltage generators for /spl Delta/-/spl Sigma/ modulation/demodulation. Some of the observed characteristics are given. The NMOS /spl Delta/-/spl Sigma/ modulator requires only two on-chip matched capacitors as precision components, and does not require a linear amplifier. A deliberate quantization step imbalance is introduced to allow a low sampling rate. The main band limiting for the 8 k samples/s is done by the recursive filter. This is realized with the serial-parallel pipeline multiplier (SPPM) in four-phase logic. The whole system is integrated on a 296 mil/spl times/342 mil chip.     

Measuring the /spl omega/ - /spl beta/ Diagram of Periodic Structures (Correspondence)

One of the most important properties of a periodic structure is the shape of the /spl omega/ - /spl beta/ diagram. A common technique for measuring the /spl omega/ - /spl beta/ diagram is to form a resonant section by placing shorting planes at positions of symmetry within the periodic structure and to observe the resonant frequencies of the resulting resonator. Discussed in this correspondence is a technique wherein the far end of the periodic structure is shorted and the positions of nulls of voltage on an input line are observed as frequency is varied. From these nulls it is possible to determine the frequencies where the electrical length of the loaded structure is a multiple of /spl pi/ radians. Basically, it is a procedure for graphically determining points on the /spl omega/ - /spl beta/ diagram.     

Conditions at a p-n junction in the presence of collected current

An abrupt p-n junction, such as occurs at the collector junction of an n-p-n transistor, is considered. The ratio of n- to p-region conductivity is taken to be very high, so that the transition region is restricted almost entirely to the p-region. The electron density distribution n within the transition region is investigated as a function of the applied reverse bias V_c, and of the minority carrier electron current density J which is injected into the transition region from the neutral p-region. It is shown that significant departures occur from the conventional solutions in which the presence of current is neglected. In particular, the electron density n_c at the plane of injection and the transition region thickness w_t, used as collector boundary conditions in the analysis of transistor operation, are shown to be current-dependent.

Two cases are considered. In Case I, applicable to transistors with an epitaxial layer in the base region below the collector, the electron velocity is assumed much less than the limiting drift velocity. For low injection level, where the minority carrier density n is everywhere less than the equilibrium majority carrier density p_p, the transition region is essentially a depletion region and the injected electrons move in an electric field determined uniquely by the applied voltage. It is shown that n_c ∝ J and w_t ∝ V_c^1/2. For high injection level, when n p_p, the transition region is essentially an accumulation region, and conditions of space-charge-limited current flow are established for which n_c ∝ J^2/3 and . The low-level injection results are primarily of interest as analytical extensions of the classical treatment. The high-level injection results are also relevant to the treatment of the dielectric diode.

In Case II, applicable to most alloy and diffused-base transistors, the electron velocity is assumed equal to the limiting drift velocity throughout the transition region. Mobile carrier depletion at low injection again gives way to accumulation at high injection. The functional relationships remain as for Case I at low injection, but become at high injection.

Semi-quantitative and detailed quantitative treatments are developed, and normalized graphs of the minority carrier density as a function of distance within the transition region are given for various junction voltages and injected currents.     

Full characterization of packaged Er-Yb-codoped phosphate glass waveguides

We present a procedure for the characterization of packaged Er-Yb-codoped phosphate glass waveguides. The procedure is based on precise measurements of the output optical powers when the waveguide is diode-laser pumped at 980 nm. The dependence of these optical powers on the input pump power is then fitted to the results from a numerical model that describes in detail the propagation of the optical powers inside the waveguide. The best fit is obtained for the following parameters: the signal wavelength scattering losses are /spl alpha/(1534)=8.3/spl times/10/sup -2/ dB/cm, the Yb/sup 3+/ absorption and emission cross sections (/spl ap/980 nm) are 5.4/spl times/10/sup -25/ m/sup 2/ and 7.0/spl times/10/sup -25/ m/sup 2/, the Er/sup 3+/ absorption and emission cross sections (/spl ap/980 nm) are 1.6/spl times/10/sup -25/ m/sup 2/ and 1.2/spl times/10/sup -25/ m/sup 2/, the Yb/sup 3+/--Er/sup 3+/ energy-transfer coefficient is 1.8/spl times/10/sup -23/ m/sup 3//s and the cooperative-upconversion coefficient is 8/spl times/10/sup -25/ m/sup 3//s. An approximate method is introduced that allows the determination of the absorption and emission cross section distributions for the erbium /sup 4/I/sub 13/2//spl hArr//sup 4/I/sub 15/2/ transition from the amplified spontaneous emission power spectrum.     

Convergence and loss bounds for Bayesian sequence prediction

The probability of observing x/sub t/ at time t, given past observations x/sub 1/...x/sub t-1/ can be computed if the true generating distribution /spl mu/ of the sequences x/sub 1/x/sub 2/x/sub 3/... is known. If /spl mu/ is unknown, but known to belong to a class /spl Mscr/ one can base one's prediction on the Bayes mix /spl xi/ defined as a weighted sum of distributions /spl nu/ /spl isin/ /spl Mscr/. Various convergence results of the mixture posterior /spl xi//sub t/ to the true posterior /spl mu//sub t/ are presented. In particular, a new (elementary) derivation of the convergence /spl xi//sub t///spl mu//sub t/ /spl rarr/ 1 is provided, which additionally gives the rate of convergence. A general sequence predictor is allowed to choose an action y/sub t/ based on x/sub 1/...x/sub t-1/ and receives loss /spl lscr//sub x(t)y(t)/ if x/sub t/ is the next symbol of the sequence. No assumptions are made on the structure of /spl lscr/ (apart from being bounded) and /spl Mscr/. The Bayes-optimal prediction scheme /spl Lambda//sub /spl xi// based on mixture /spl xi/ and the Bayes-optimal informed prediction scheme /spl Lambda//sub /spl mu// are defined and the total loss L/sub /spl xi// of /spl Lambda//sub /spl xi// is bounded in terms of the total loss L/sub /spl mu// of /spl Lambda//sub /spl mu//. It is shown that L/sub /spl xi// is bounded for bounded L/sub /spl mu// and L/sub /spl xi///L/sub /spl mu// /spl rarr/ 1 for L/sub /spl mu// /spl rarr/ /spl infin/. Convergence of the instantaneous losses is also proven.     

Surface-emitting laser diode with distributed Bragg reflector and buried heterostructure

A surface-emitting laser diode (SELD) with distributed Bragg reflector (DBR) and buried heterostructure (BH) is fabricated by the metalorganic chemical vapour deposition (MOCVD), reactive ion beam etching (RIBE) and liquid phase epitaxial (LPE) regrowth techniques. An Al/sub 0.1/Ga/sub 0.9/As/Al/sub 0.7/Ga/sub 0.3/As multilayer is employed for the lower reflector. The active region is embedded with Al/sub 0.4/Ga/sub 0.6/As current blocking layers. The threshold current is 28 mA, and the spectral width is 2.5 AA. A 2*2 array is also demonstrated.<>     

Precise Design of a Bandpass Filter Using High-Q Dielectric Ring Resonators

A precise design is presented for a bandpass filter constructed by placing TE/sub 01delta/ dielectric ring resonators coaxially in a TE/sub 01/ cutoff circular waveguide. On the basis of a rigorous analysis by the mode- matching technique, the interresonator coupling coefficients are determined accurately from the calculation of two resonant frequencies f/sub sh/ and f/sub op/ when the structurally symmetric plane is short- and open-circuited. For the TE/sub 01delta/ ring resonator,the resonant frequency f/sub 0/, the temperature coefficient tau/sub f/, the unloaded Q(Q/sub u/), and the other resonances are also calculated accurately in a similar way. From the calculations, the optimum dimensions are determined to obtain the maximum Q/sub u/, as F/sub r/ = f/sub r/ /f/sub 0/ is kept constant, where f/sub r/ is the next higher resonant frequency the ring resonator using low-loss ceramics (epsilon/sub r/ = 24.3, tan delta = 5 x 10/sup -5/) has Q/sub u/ = 16800 at 12 GHz and tau/sub f/ = 0.1+-0.5 ppm/° C, while the rod one has Q/sub u/ = 14700. A four-stage Chebyshev filter having ripple of 0.04 dB and equiripple bandwidth of 27.3 MHz at f/sub 0/ =11.958 GHz is fabricated using these resonator; the measured frequency responses agree well with theory. The insertion loss is 0.9 dB, which corresponds to Q/sub u/ = 9800.     

Characteristics of Inhomogeneous Broadside-Coupled Striplines

A variational method for the analysis of inhomogeneous broadside-coupled striplines is described. The data for even- and odd-mode characteristic impedances, effective dielectric constants, and mode phase velocity ratios are presented. It is found that the phase velocity ratio may be varied over the range 1.14 /spl les/ ( V/sub e/ / V/sub 0/) /spl les/ 3.6 for broadside-coupled suspended microstrip lines (BSML) and 0.36 /spl les/ ( V/sub e/ / V/sub 0/) /spl les/ 0.93 for broadside-coupled inverted microstrip lines (BIML) using materials with dielectric constant less than 16 and S/b /spl ges/ 0.05, W/b /spl les/ 2.0. The effect of nonzero strip thickness is also calculated. It is noticed that the effect of thickness is more pronounced for the odd-mode case than for the even mode. Losses are obtained using the incremental inductance rule of Wheeler. The odd-mode attenuation constant is always higher than the even-mode value.